Phelps-Dodge (also known as PD) was bought by Celwave (year?), which was bought by Radio Frequency Systems (aka RFS) (year?) whose web site is at http://www.rfsworld.com/RFSGlobal.   If you are looking for other web pages containing information on a specific antenna - for example some repeater group whose web page mentions a Phelps-Dodge PD-458 in passing - you may have to check under all three company names.   For example, under Google, you would type (less the square brackets): [ "Phelps Dodge" OR Celwave OR "Radio Frequency Systems" OR "RFS" 458 ].   Note that the OR parameter in a Google search must be in ALL CAPS.

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Antenna Specialists was sold to PCTel (year?) - and their corporate web site is at http://www.antenna.com, and the product web site is at http://www.antenna.com/products.html.   The 2-way mobile product model number lookup page is at http://www.antenna.com/lm_cat/index.html.

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I was told recently that PCTel bought both Maxrad and Antennex (but I don't know the dates)

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DB Products was bought by Andrew, but they didn't want everything. The leftovers (including duplexers) are now sold by a company called dbSpectra, located in Lewisville, Texas (the web site is at http://www.dbspectra.com). From their web site: "...in December of 2004, dbSpectra signed a licensing agreement with Andrew Corporation to manufacture and sell the Legacy Decibel Products site management equipment such as filters, duplexers, combiners, tower top amplifiers and more. These products had been outsourced and dbSpectra successfully brought them back and have since hired many of the personnel involved in the design and manufacture of these excellent products."

In March of 2006 the Laird Group of England (AKA LairdTech) purchased Antenex for about $20.5 million, and then in Febuary of 2007 bought Cushcraft for about $90 million.

And about a month later Andrew purchased the English manufacturer Precision Antennas for about $36 million.

In December of 2007 Andrew was bought by CommScope for US$2.6 Billion.
Here's the current Andrew/Commscope catalog.

In many cases you will find that manufacturers web sites have theoretical information that is applicable to all... i.e. the theory articles on Manufacturer "X" products applies to Manufacturer "Y" and to "Z". Sometimes researching other manufacturers web sites can save you a lot of money... for example, if Manufacturer "X" claims that a crystal filter will solve your desense problem. Then you go to "Y"s web site and there you discover that, yes, a crystal filter can be used in the receiver feedline to notch out a local signal, or to pass your signal. What the Manufacturer "X" web site didn't tell you, and the Manufacturer "Y " or "Z" web site did, is that in your specific case it may not work. Unless you were familiar with crystal filters you would not know that the insertion loss can be as high as 12db, which in many cases makes a crystal filter on a repeater receiver unusable.... the signal level budget just isn't there (i.e. while adding the crystal filter would kill the interfering signal, it also reduced your receiving range to 1/2 of what it was, or maybe even less). So do your homework and learn all you can about the theory behind the hardware before you hand over your money.

Combiners
A Combiner is a system of cavities and optionally isolators (or cavities and optionally circulators paired with external loads) that allows multiple transmitters to share one transmitting antenna, but at a cost. Some combiner systems can cost you from 50% to 75% of your transmit power... i.e. that 100 watt repeater transmitter that gave you N miles radius coverage on a stand-alone antenna may only have the performace of a 50 watt or 25 watt system once the combiner is in line. Also don't forget that the antenna the combiner is feeding has a finite power limit. Some are rated at 200 watts, and by the time you combine 5 transmitters, each with 100 watts out, through a 3db loss combiner, that's still 250 watts that's going up the hose to the antenna, and (poof) goes the antenna (and the combiner needs dummy loads that can handle 250w continuous duty, and appropriate ventilation to get rid of the heat). Note that systems that use combiners usually have a separate receiving antenna that is multicoupled to each receiver.

Combiners are expensive not only in RF energy but also in money - a 2 port UHF combiner will set you back about US$4,600, a 4 port about US$8,400, an 8 port about US$16,000, and that's plus shipping. See http://www.telewave.com/pricelist/106-450combiners.html.

Additional detail for this introductary paragraph, and additional articles / publications on this topic are welcome.   Anybody want to write an article on how to pick the frequencies that can be combined onto a single antenna?

	About Combiners   By DB Products, copyrighted 1975. From the preface: "This booklet has been written for the many people engaged in two-way radio communications who are NOT radio engineers. A non-technical presentation of a rather complex subject has been attempted in an effort to bring about a better understanding of combiners used in two-way radio systems."
	Tuning Instructions for the DB4350 and DB4360 Low Loss Combiners   8kb   A one-page PDF file.
	Tuning Procedure for Two-Transmitter Combiners DB4351, DB4381, DB4352, DB4382, DB4384 Two page 64kb PDF describing the tuneup of a unit that is essentially two isolators, two low pass filters, a hybrid coupler and a dummy load.
	Product Description & Installation and Tuning Instructions for the ACT27nnJ2 and DBNXTL27nn Transmitter Combiner   85 KB   A two-page PDF file. 5-Channel Models: ACT2705J2, DBNXTL2705 10-Channel Models: ACT2710J2, DBNXTL2710 15-Channel Model: ACT2715J2 20-Channel Model: ACT2720J2
	Tuning Instructions for the DB4379 Low Loss Combiner   9kb   A one-page PDF file describing a unit for up to 8 transmitters.
	Celwave 220 brochure   580 KB PDF Back when 220-222 was stolen from the hams to be a new land mobile radio band Cellwave put together a brochure with the tech specs on all of their 220 products plus three sample system diagrams. The products include the PD220-8, PD220DT, 92.0101, and 93.0024 antennas, the TJD220-5T transmitter combiner, PD1604B cavity, PD5042-2 duplexer, PD5279 cavity, PD5280-1, PD5280-2 and PD5280-3 duplexers, PD1602 low-pass filter, PD506-2A duplexer, PD5091-2A dual notch cavity, PD5090-2B/3 bandpass filter and the PD5090-2A bandpass cavity.

What's a circulator? a.k.a. Properties of a Ferromagnetic Circulator   By Kevin Custer W3KKC
The Care and Feeding of the R.F. Isolator   a 14kb PDF by William F. Lieske, Sr. Founder, EMR Corporation
An Elementary Introduction to Ferrite Isolators, Circulators and RF Loads   a 1mb PDF file   A TX-RX Corp. "Seminar Series" writeup - 14 pages.
Circulators and Ring Hybrids   a 363 KB PDF by Wolfgang Borschel DK2DO
Field Tuning Instructions for Dual Junction Tunable Isolators   a one-page 21kb PDF file by Decibel Products
Generic single stage / single-section isolator tuning instructions from EMR   a 26kb PDF file donated by Eric Lemmon WB6FLY
Generic dual stage / dual-section isolator tuning instructions from EMR   a 55kb PDF file donated by Eric Lemmon WB6FLY
Sinclair's instructions on tuning isolators   Donated by Eric Lemmon WB6FLY
Microwave Associates 7R011 Isolator Tuning Instructions   Donated by Micheal Salem N5MS
Good for 125 watts, with 0.9 db insertion loss typical with 1.3 db max. The isolation can be as high as 60 db with 50 db typical.
Data sheet on the DB 4318H-2C High Band Single Channel filter and isolator
A two-page PDF file describing a Decibel Products 164 - 168.5 MHz dual isolator but the directions apply to similar units. The drawing is in error, it does not show the termaline on the output port.

Unmatched loads did not start with solid state PA decks. Feedlines over the years have included 35 ohms, 50 ohms, 72 ohms, 300 ohms and 450 ohms. As mentioned, one way to transform impedances is to use a "magic" length of the right impedance of coax as a matching transformer.   The cable length between the end cavity and the transmitter is NOT supposed to be critical, and if it is then you have an impedance problem.   While the most common situation is between the transmitter power amplifier and the duplexer, the same situation can happen on the receiver, it is just much less visible.   Matching the transmitter to the duplexer is covered in this article Cabling lengths between he Duplexer and Radio Set.   Despite the article title, there is a lot of Z-matcher info in there.

Tony King W4ZT has some information on the Z-Matcher that GE built into the Mastr II stations at the W4ZT Z-Matcher page. The closeup photos show how GE simply replaced the antenna relay (normally replaced with a jumper in repeater service) with the Z-matcher daughter board.
The schematic to the GE Z-Matcher is here.
It's part of LBI-30201G.
The tuneup info for the DB Products Z-matchers is here.

A duplexer is made up of a number of cavities and a similar number of critical length cables beteeen them, each of which adds to the total transmit-to-recieve isolation provided by the assembly.   If you're just starting out, I strongly suggest that you read the first eight articles below, especially those by Jacques Audet VE2AZX, John Portune W6NBC and by William F. Lieske.   Yes, there is some repeated material between the articles, but if you're new to duplexers, it won't hurt.   When you have multiple people writing on the same topic (any topic) some repetition is inevitable.   The 8 articles collectively will give you a basic education on duplexers.

The proper way to tune a cavity or a duplexer is to use 6db or 10db 50 ohm pads between the test equipment and the cavity or endmost duplexer can, as that ensures that pad "masks" any non-50-ohm-impedance in your test equipment and ensures that the duplexer is really tuned to precisely 50 ohms.

Note that duplexers are initially tuned and the ports labeled at the factory.   Most are labeled "REC", "ANT" and TRANS", or something similar (see this photo).   A duplexer is built with a "higher" side and a "lower" side, and the loops and inter-cavity cabling are selected for those frequencies.   The application an amateur has may conflict with the original port labels.   Most commercial repeaters (definitely in UHF, usually on VHF) receive on the higher frequency and transmit on the lower frequency, whereas amateur repeaters can swing either way.   So look at the original label and note if the receive side is the higher of the two frequencies, or if the transmit side is... and keep the high / low relationship the same as you retune it.   You may end up using the original receive side as your transmit side.   Personally, I remove the factory "Receiver" and "Transmitter" labels and replace them with my own permanent labels reading "High Side Pass" and "Low Side Pass", then I add temporary "Receiver" and "Transmitter" labels for each application. This is expecially true on UHF GMRS (+ offset) and on UHF amateur (- offset in Southern California, Oregon, Denver, and many other areas).   Some manufacturers have gone to even more detail with connector markings that read "pass low, reject high" on one side and "pass high, reject low" on the other.

Interestingly, if you order a untuned duplexer it arrives appropriately labeled... see this photo.

The cable length between the cavities in a duplexer is very, very critical, and the actual length of any one cable is dependent on three factors: (1) the cable velocity factor, (2) the length of the coupling loops, and (3) the frequency involved.   On a 600 KHz offset 2m duplexer the frequenciesa are so close together that the receive side and transmit side lengths are usually the same, however on a VHF commercial 5 MHz (or more) offset or on a UHF duplexer the optimum length is different between the receive and transmit side.   And the lengths of the cables between the duplexer ports and the antenna "T" fitting are also very critical and frequency dependent (and a different length than the intercavity cables). Many duplexer assemblies are wider in frequency than their harnesses - for example if you move a VHF duplexer from 160 MHz or 170 MHz to 2 meters you will have to aquire a new harness kit, or lengthen the old one. Hams that are moving a 470 MHz duplexer to 440 MHz will have the same problem.

Double-shielded silver-plated coax is the best thing to use to connect duplexers.   For example, RG-214 has two silver-plated braids and a silver-plated inner conductor for maximum noise rejection.   Avoid coax types that have disimilar metals rubbing against each other such as LMR-(any 3-digit or 4-digit number) or Belden 9913, both of which use an aluminum foil shield rubbing against a copper braid.   Many amateurs have purchased LMR-400 or similar cable, installed it, and it works fine (for a while).   They just rave about how good it is.   Then anything from 9 months to 5 years later they find themselves taking it down as the cable itself causes "duplex noise" (see the article on this page titled "Help!! I have a crackling noise in my repeater" by Kevin Custer W3KKC).   The expensive LMR cable gets reused somewhere else.   RG-142 and RG-400, both a smaller version of RG-214 but sharing the same construction, can also be used (but see the article on this page titled "Double Shielded Coax Cable, The differences between RG-142 and RG-400, and why you DON'T want to use RG-142..." by Eric Lemmon WB6FLY)".   My personal preference is to use nothing but Heliax and Superflex on the antenna side of the duplexer, and nothing but Superflex and RG-400 on the radio side.   Yes, it's expensive, but like my late father used to say about hand and power tools, "Buying quality only hurts once".   Good quality cable is going to be low loss and last a long, long, long time, and it's one less thing to worry about.   If you have to use coax then look at RG-393 for the large diameter (i.e RG-8/213/214 size) and RG-142/RG-400 (RG58 size).   All are double shielded with silver plated shields and will not cause duplex noise.

The type of cable that is used between the duplexer and the recevier and between the duplexer and the transmitter is important.   Many manufacturers scrimp and use cheap single-shielded cable, and in many cases get away with it.   The Motorola GR series repeaters and many of the Yaesu/Vertex VXR series repeaters were (still are?) supplied with single-shield jumpers inside the cabinet, and this allows random low level desense to occur.   Replacing the factory jumpers with RG-400/U double-shielded coax eliminates that.   And when you do make cables, make them with the correct silver-plated connectors on each end, so that you do not have to use any adapters.   Use a right-angle connector rather than a normal connector and a right angle adapter.   All it takes is one chrome or nickel plated connector or one nickel plated adapter to ruin your day.

A note on small mobile duplexers from Eric Lemmon WB6FLY:
(Most "mobile duplexers" are notch-only, and are sometimes called notchplexers)
Most UHF mobile notch-only "flatpack" duplexers will work fine below 50 watts at a 5 MHz split- but their performance rapidly deteriorates when operated outside of their stated band limits. For example, a commercial-band mobile duplexer that was manufactured to operate in the 450-470 MHz band will likely perform poorly in the 440-450 MHz Amateur band. Although such a duplexer may SEEM to be working in the Ham 70 cm band, it may have excessive insertion loss that the owner may not realize. That's because the internal coupling loops are set at the factory during manufacture and not readily adjustable by the owner.

I once tried to use a commercial-band mobile ("flat pack") duplexer on 70 cm in a portable repeater, and was disappointed in its performance- especially in the receive sensitivity at 441 MHz. I then ordered a new Celwave duplexer of the same model, but factory-tuned for my Amateur pair. What a difference! Once the new duplexer was installed, the receive range of the portable repeater was significantly improved, with no other changes.

Other people report no problems with moving flatpacks to 440 MHz or even 420 MHz, it all depends on the original design of the particular duplexer.   A good test, and a real eye-opener, is to measure the performance, especially the insertion loss, at the original design frequencies and then again on the your new frequencies. In most cases the numbers will surprise you.

Above all remember that notch-only duplexers are not appropriate for high level RF sites as they provide zero protection for the receiver from any other transmitter - they are designed to protect a single repeater from itself, and nothing else (and remember the "higher side" and "lower side" rule above). If you are going to have a quality system at a busy site you need to plan on a six cavity pass-notch duplexer.

	DUPLEXERS - An Introductory Tutorial   by Jack Daniel KD6YVL     (offsite link) This is a nice writeup that should be titled "Duplexers 101".   Well worth reading.
	Theory and Testing of Duplexers   by Jacques Audet VE2AZX This is a large (60 pages) technical writeup that should be titled "Duplexers 102".   Again, well worth reading.
	Technical Duplexer Page with good theory and explanations, and some homebrew construction notes. By John Portune W6NBC
	Understanding, Maintaining & Re-Tuning Antenna Duplexers 145kb PDF   By William F. Lieske, Sr., Founder, EMR Corporation A good basic theory writeup, including the differences between Band Pass and Band Reject.   The original copy at the EMR web site
	Combating Spurious Output And Overloading With Cavity Filters   1.2mb PDF   by TX-RX Corp. A "Seminar Series" writeup that covers the theory behind cavity filters - mandatory reading for those unfamiliar with them.
	Coaxial Resonators, Applied theory and practice, with photos   by Mike Pinfold, ZL1BTB
	Interference Control Through The Use Of Cavity Filters And Ferrite Isolators   900kb PDF   by TX-RX Corp.
	Technical Notes on Duplexer Problems and Remedies 1mb PDF   By TX-RX Corp.
	The Design of High Isolation Duplexers And A New Antenna For Duplex Systems   755 KB PDF An IEEE Transactions publication from March 1965 by W. B. Bryson of Communications Products Company, a division of Phelps Dodge.
	A Guide to Duplexer Specifications   over 130 different models, by Paul Kelley N1BUG (Contributions to the list are very welcome)
	Tuning and Adjusting Vari-Notch-Duplexers   185kb PDF   by TX-RX Corp. A "Seminar Series" writeup that covers the theory behind cavity filters and isolators.
	T-Pass Expandable Cavity Muticoupler System   500kb PDF   by TX-RX Corp. A "Seminar Series" writeup that covers the various type of cavity-based multicouplers and the T-Pass design.
	The Hybrid Ring Duplexer   A comprehensive explanation of the Hybrid Ring, by Kevin Custer W3KKC
	Six Meter Heliax Duplexer Design   by Jim Poll, WB5WPA   (off-site link) Here's one implementation of the above design   by Oscar KF6YB (off-site link) Here's another implementation of the above design   by Mike Perryman K5JMP (off-site link) Six Meter Heliax Receive Filter Construction and Testing article based on the above designs, by Robert Meister WA1MIK and David Malicki N1OFJ.   Note that this is NOT a full duplexer; just the receive half (but it could easily be extended to a full duplexer).
	Using open stubs to notch interference   By Nico PAØNHC   (offsite link) An excellent article on reducing paging transmitter (and others) interference into 2m repeaters. Note that common European usage is that a comma is used where Westerners use a period to mark decimals, for example 144.550 MHz is written as 144,550 MHz so readers used to the period will have to do some mental "translation".   In this article Nico has used a mix of both forms so it can be a little confusing on the first read.
	GE Datafile Bulletin 10002-1, A 25-250 MC Quarter Wave Stub Filter   General Electric produced several useful DataFile Bulletins (the ones we have are available for free download from the GE LBI page at this web site). This one is a 400KB PDF file, and is subtitled: "Even though General Electric Two Way Radio Transmitters well exceed FCC requirements for spurious radiation, the 60-80-db sprious attenuation provided may, in a few situations, be insufficicient to provent interference. This bulletin describes the construction of a filter, useful for supressing spurious radiation at one specific frequency...."
	Someone say 6 meter duplexer?   A comprehensive conversion of a lowband pass cavity to BpBr by Jeff DePolo WN3A...
	How do I tune this notch duplexer?   by Kevin Custer W3KKC
	A Homemade Duplexer for 2-Meter Repeaters   by John Bilodeau, W1GAN (from the July 1972 QST magazine) Note: In the 30-plus years since this article was written, the spring-contact based BNC has fallen out of favor.   Type N connectors are much preferred over BNC connectors as they depend on a silver-to-silver screw compression contact, plus they can handle more power.   You must use double shielded coax in the harness.   RG-55 is mentioned in the article, I'd use RG-400 and compensate on the inter-cavity lengths.   If anybody has built this unit with better connectors and modern cable, and would like to update this article please let me know.
	Tests of the DCI VHF and UHF 4-pole bandpass filters  by Robert W. Meister WA1MIK These filters definitely do the job, meeting or exceeding manufacturer's specs. They cover the entire 144-148 and 440-450 MHz bands and have sharp cutoffs. If you need more filtering, they also sell 6, 8, and 10-pole filters with attenuations over 80dB. These handle 200 watts and can be used at repeater sites.

	RFS / Celwave     See also Phelps-Dodge, as Cellwave bought that company and continued many of their products under the Cellwave name.   Click here for Celwave antennas
		Celwave model 696, 696SR (UHF), 896 or 896SR (800-960 MHz) Duplexer   86Kb PDF file   Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY
		Celwave Duplexer Cable Harness Lengths (oriented for printing)   44Kb PDF file   Donated by A. Nony Mous
		Celwave 220 brochure   580 KB PDF Back when 220-222 was stolen from the hams to be a new land mobile radio band Cellwave put together a brochure with the tech specs on all of their 220 products plus three sample system diagrams. The products include the PD220-8, PD220DT, 92.0101, and 93.0024 antennas, the TJD220-5T transmitter combiner, PD1604B cavity, PD5042-2 duplexer, PD5279 cavity, PD5280-1, PD5280-2 and PD5280-3 duplexers, PD1602 low-pass filter, PD506-2A duplexer, PD5091-2A dual notch cavity, PD5090-2B/3 bandpass filter and the PD5090-2A bandpass cavity.

Decibel Products   Click here for DB antennas Data Sheet on DB's line of power dividers - Three page PDF 264kb donated by John Lock KFØM This writeup covers the K522 & K542 for 144-174 MHz, the K526 & K546 for 406-512 MHz, the K528 & K548 for 800-960 MHz and the K528M & K548M for 1850-1990 MHz DB's pipe and tower mounting clamp kit DB365-OS   Early version donated by John Lock KFØM DB's pipe and tower mounting clamp kit DB365-OS & ASPR616     (later version) Installation and Tuning Instructions for DB Band Pass Cavity Filters   50kb   Despite the model number list this information is pretty generic. This writeup mentions these models: DB4001 (148-174 MHz), DB4002 (118-512 MHz), DB4011 (70-88 MHz), DB4013 (88-118 MHz), DB4015 (118-148 MHz), DB4020 (406-420 MHz), DB4018 (225-400 MHz), DB4021 (406-512 MHz), DB4026 (406-512 MHz), DB4028 (806-960 MHz), DB4042 (30-50 MHz), DB4170 (138-174 MHz), DB4171 (450-512 MHz). Field Tuning Instructions for Dual Junction Tunable Isolators   one-page 21kb PDF file by Decibel Products Tuning Instructions for the DB4022 (UHF) & 4029 (800 MHz) band pass / band reject cavities   31kb   A two-page PDF file DB 4023 UHF duplexer (3 cavity) and 4081 (4 cavity) spec sheet   donated by W. M. Kahl N6KYD Tuning Instructions for the DB4030 (four cavity) and 4032 (six cavity) Low Band Duplexers   five page 920Kb PDF donated by W. M. Kahl N6KYD     Tuning Instructions for the DB4030 and 4032 4-cavity and 6-cavity Low Band Duplexers   24kb   A two-page PDF file (appears to be a later version of the five page one above)     Converting the DB-4032 Low Band Duplexer to the 6M Amateur Band   29kb image   A one-page writeup from DB Engineering on converting the DB-4032 to the 6-meter amateur band   It's a scan of a fax so it's not perfect, but it's quite readable (oriented for printing) Same drawing sized to be printed on 11x17 paper   Both donated by Chris Nicholson N9LLO Installation and Alignment Instructions for the DB4036 (mid-band), 4044 and 4046 (high-band) Base Station Duplexers   47kb  A two-page PDF file describing wide-spaced (3 MHz and 5 MHz) duplexers that are not of much use to hams, but would be to public safety and disaster services folks. DB 4048 duplexer specs (high band - 146-174 MHz) - an eight page PDF file      DB4048 duplexer review article from June 1975 QST magazine -     Page 1     Page 2     Scan courtesy of Glenn Little WB4UIV Installation and Tuning Instructions for the DB4055 & 4056 (high band), 4067 & 4068 (406-420 UHF) and 4071 & 4072 (450-470 UHF) duplexers  40 KB   A two-page PDF file         Here's a photo of the internals of a 4072 housing. Installationa and Tuning on Decibel Products 4057 (three cavity) and 4058 (four cavity) high band duplexers   Two page 120kb PDF donated by A. Nony Mous Catalog sheet on the DB4060 & 4062 Band Pass / Band Reject duplexers   55kb PDF     Installation and Tuning Instructions for the DB4060 & 4062 Band Pass / Band Reject duplexers   46kb   A two-page PDF file (the DB4060 has 4 cavities, the 4062 has 6 cavities)     Repair of the DB4060 & 4062 Band Pass / Band Reject duplexers   46kb   An article by Bernie K5BP detailing notch capacitor replacement for these units, including a source for the original component.     Repair of the DB4060 & 4062 Band Pass / Band Reject duplexers   An offsite web page by N1BUG... he writes: I have a DB-4062, which is the 6 cavity version of the 4060. It was old when I placed it in service in 1997 but worked OK. Over the years it just slowly deteriorated until it became essentially unusable. Finally I took the thing apart to investigate, and was able to restore it to excellent function after 15-20 hours of work. I created a web page that covered my experience... Specifications and Data on the DB4075 and DB4076 UHF Bandpass Reject duplexers   Photo   423kb Tuning and Installation Information on the DB4075 and DB4076 UHF Bandpass Reject duplexers   91kb Tuning Information on the DB4090 806-960 MHz Bandpass Reject duplexers   43kb Installation and Tuning Instructions for the DB4104 (low band), 4040 (high band) and 4075 (UHF) single-cavity notch filters   25kb   A two-page PDF file Installation and Tuning Instructions for the 4307, 4308 and 4309 Hybrid Couplers   14kb   PDF file. Installation and Tuning Instructions for the DB4318H-2C Single Channel Filter and Isolator   10kb   A two-page PDF file describing a 164-168.5 MHz unit but the directions apply to similar units. Motorola Info on the T1480 series high band 4-can duplexer / cavity filter panel   1.14Mb PDF file of the official Moto manual that covers the two-cavity and four-cavity models (T1481, T1482, T1485A, T1485AF, T1487A, T1487AF) Info on the T1500 series UHF 4-can duplexer / cavity filter panel   There's quite a bit of info, so it has it's own web page that covers the T1500, T1501, T1502, T1503, T1504, T1505, T1506 and T1507 units. Phelps-Dodge PD-506 manual   263 Kb PDF   Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY NOTE: You CANNOT tell from the model number if a PD-506 is for 144-174 or for 220-225 MHz ! You have to look at the frequency label ! This is a 4-cavity pass-notch duplexer than is supplied as either a 144-174 or 220-225 MHz version. At high band it will work from 600 KHz to 7 MHz separation, and at 220 it will work at from 1 to 5 MHz separation. Rejection is specified at 80 db, and under 2 db insertion loss. PD-522-509     Does anyone have the spec sheet, the tuning instructions or can supply a couple of photos? This is a popular 6-cavity UHF duplexer that is built as a 4+2 unit (i.e. four cavities on one side and two on the other. If you set it on the table so that the single coax connector is on the left, and the two are on the right, the layout is in the sequence of: TXnotch--cable--RXpass--cable--RXpass--cable--TXnotch--cable--RXnotch--cable--TXpass, with the first 4 cavities on the receive side and the last two on the transmit side. PD-526     Photo 1     Photo 2 This is a 6 Cavity UHF Repeater-Base Station Duplexer that is an outstanding performer. Specs:     Frequency Coverage = 435 to 470 MHz.     Minimum Frequency Spacing, MHz. = 3     Minimum TX to RX Isolation, dB = 100     Maximum Insertion Loss, dB = 1.0     TX Bandwidth, MHz. = 0.025     RX Bandwidth, MHz. = 0.025     Maximum Power Input = 250 watts     Connectors = "N" Female     VSWR, Max. (50 ohms) = 1.3:1 Eric Lemmon WB6FLY wrote: This duplexer is a Motorola part number 0185417U05 unit, which has a current (mid 2009) dealer price of $ 1,173.00. It is made for Motorola by RFS/Celwave, which sells the same unit as PD526-4-2. It is the X182AD Option for Quantar, Quantro, and MTR2000 stations. I have an identical unit in service on a 100 watt UHF MTR2000 repeater, and it is an excellent performer. Prior to installation, I verified that its isolation was better than the 120 dB specified- a very good figure. PD-638-509-6 manual   263 Kb PDF   Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY This is a 6-cavity pass-notch mobile duplexer that is available as a 150-162, 162-174, 220-225, or 471-512 MHz unit. - 150-162 or 162-174 MHz: 150 watts, 75db rejection, 1.2 dB insertion loss at 2 MHz spacing. At 5 MHz the insertion loss drops to 0.7 dB. - 220-225 MHz: 100 watts, 75db rejection, 2 dB insertion loss at 1.6 MHz spacing. - 470-512 MHz: 75 watts, 75db rejection, 1.7 dB insertion loss at 3 MHz spacing. PD5042-1 VHF Duplexer data from Motorola   960 Kb PDF   scanned by Eric Lemmon WB6FLY Motorola relabels the Celwave model PD5042-1-50 duplexers and includes them as factory option with VHF Quantar or MTR2000 stations. Their part numbers are 0185417U01 for the 132-146 MHz range, 0185417U02 covers 144-160 MHz, and 0185417U03 covers 158-174 MHz. PD-7540, PD-7560, PD-7640, PD-7660 duplexer manual   109 Kb   This unit is also called the "MiniPlexer". This is a UHF flat-pack mobile notch-only duplexer that is limited to 40 watts and comes in two ranges: 406-435 and 435-470 MHz and in 4 can or 6-can versions (7n40=4-can, 7n60=6-can). The 4-can version provides 50 dB rejection and 1 dB insertion loss at 5 MHz spacing, and the 6-can version provides 75 dB and 1.3 dB. Like any notch-only duplexer, any frequency outside the notches rides right through...   Donated by A. Nony Mous. PD-7540, PD-7560, PD-7640, PD-7660 duplexer manual   518 Kb This is a later verion of the same manual, with enough new information to be worth having both versions available. Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY. Sinclair Labs P-Series Duplexer Specifications Sheet   Covering the P-1C01-G, P-1C02G, P-201G, P202G, P203G, P-301G, P-302G, P-303G models   by Sinclair Corporation. Sinclair Q202-G cable harness drawing   88 KB courtesy of WB6FLY A while back, Eric set up a Q202G duplexer for a local radio club. The duplexer was originally made for and used on a commercial pair in the 152-157 MHz band, and no matter how much work was spent on tinung the duplexer it would not perform. He had the club purchase a new low-split harness from Sinclair. When it arrived, he took careful measurements of both the new and the old harness, and the results are here... If the harness on your duplexer is the high-split version, with about 12 inches between tee centers, you will never be able to achieve optimum peformance on 2m, and especially in the 145 repeater range. Some people "stretch" the cables by adding 90 degree elbow adapters to the ends as a test, but end up buying or making a new harness. The factory-made harness uses Delta brand crimped connectors, and costs about $250. Eric commented that "If I were to do this again, I would consider fabricating the harness myself, with genuine Delta connectors and tees, which can be purchased for a total of around $120". If you do, don't forget to use real mil-spec RG-214 or RG-393 coax with the silver plating. Tuning instructions for "P" and "Q" series cavity duplexers, and FP, FR, FQ series cavities   manual CM-1008 by Sinclair Corporation. Tuning instructions for the Q-202G, Q-208G, Q-218G, 2B02G, Q-2B02G, Q-2B17G series cavity duplexers   manual FP-1032 by Sinclair Corporation. Catalog sheet and Specifications for the 6-cavity Res-Lock Q-Circuit VHF Duplexer Tuning instructions for the Q-Series, ResLok 4 - Q‑circuit Duplexers - manual number CM-351. Written on the front is "Sincl Q2330E" Installation and Tuning instructions for the Q‑Circuit Res-Lock Duplexers - manual number CM-1009. This manual covers the Q-1220E (66‑88 MHz), Q-2220E (132‑174 MHz), Q-2222E (148‑174 MHz), Q-3220E (406‑512 MHz) and Q-4220E (806‑960 MHz) duplexers. Photos of a new coupling loop for a 2220E: Photo 1     Photo 2     Photo 3     Photo 4 Duplexer Tuning Instructions for the R101G to R116G and R-1C01-G, R-1C02G, R-1A01G models   (manual number CM-159): Note: This manual also covers a large number of other models in the 2H-30, 2H-37, 2H-43, 2H-66, 2H-77, H-30, H-37, H-43, H-66 and H-77 series.   The actual list is on the first page. Modification of R101, R104, or R110 for amateur 6 meter operation   (manual number CI-051). Hybrid Ring Duplexer Tuning Instructions   (manual CM-106) (theory on the W2EUP-designed Sinclair Hybrid Ring Duplexer). MR-354, MR-356 and MR-3332 406-512 MHz mobile duplexer catalog sheet   191kb JPG file - scan of a catalog page. Mobile duplexer MR-354 Specification Sheet   2-page 88kb PDF file donated by Ted Maczulat VE7TFM Mobile duplexer MR-356 Specification Sheet   2-page 87kb PDF file MR series mobile duplexer tuning   (manual number CM-1010)   150kb PDF Covers the MR-254 and MR-256 (high band, 4.5-10Mhz separation), MR-354 and MR-356 (UHF, 5-10Mhz separation), MR-454 and MR-456 (806-952 MHz, up to 45 MHz separation) units. Note that these duplexers are rated at 50 watts or less. The high band units are built for 148-160 MHz and 160-174 MHz splits, the UHF are built for 406-450 MHz and 440-512 MHz splits, and the 800/900 units are built for 806-890 MHz and 928-952 MHz splits. SRL-101C Low band antenna information   The sheet says "30-50 MHz" but gives info on 30-90 MHz.   440kb PDF file. SRL-229 High band antenna information Epoxy Procedure   167kb PDF Base Pipe   61kb PDF Installation Instructions   143kb PDF Mounting Detail   92kb PDF "FP", "FR", "FQ" Series Bandpass Filters Product Description   Page 1 34.2kb     Page 2 28.9kb     Donated by Eric Lemmon WB6FLY. "FP" Series Electrical Specs 27kb PDF file donated by Eric Lemmon WB6FLY "FR" Series Electrical Specs 31kb PDF file donated by Eric Lemmon WB6FLY "FQ" Series Electrical Specs 30kb PDF file donated by Eric Lemmon WB6FLY "FP", "FR", "FQ" Series Tuning 48kb PDF file donated by Eric Lemmon WB6FLY "FP" Series Tuning 61kb PDF file donated by Eric Lemmon WB6FLY "FR" Series Tuning 68kb PDF file donated by Eric Lemmon WB6FLY "FQ" Series Tuning 71kb PDF file donated by Eric Lemmon WB6FLY "FP", "FR", "FQ" Series Parts 23kb PDF file donated by Eric Lemmon WB6FLY "P", "Q", "R" Series Description 37kb PDF file donated by Eric Lemmon WB6FLY "P" Series Electrical Specs 40kb PDF file donated by Eric Lemmon WB6FLY "Q" Series Electrical Specs 41kb PDF file donated by Eric Lemmon WB6FLY "P" and "Q" Series Preliminary Tuning 32kb PDF file donated by Eric Lemmon WB6FLY "P" and "Q" Series Outlines 42kb PDF file donated by Eric Lemmon WB6FLY "P" Series Retuning 58kb PDF file donated by Eric Lemmon WB6FLY "Q" Series Tuning 86kb PDF file donated by Eric Lemmon WB6FLY "P" and "Q" Series Parts 33kb PDF file donated by Eric Lemmon WB6FLY "C" Series Description 53kb PDF file donated by Eric Lemmon WB6FLY "C" Series Systems 79kb PDF file donated by Eric Lemmon WB6FLY "C" Series Electrical Specs 59kb PDF file donated by Eric Lemmon WB6FLY "C" Series Mechanical Specs 64kb PDF file donated by Eric Lemmon WB6FLY "C" Series Curves 49kb PDF file donated by Eric Lemmon WB6FLY "C" Series Typical Systems 67kb PDF file donated by Eric Lemmon WB6FLY "C" Series Tuning 49kb PDF file donated by Eric Lemmon WB6FLY "C" Series Parts 71kb PDF file donated by Eric Lemmon WB6FLY Telewave TPRD-series Duplexer Tuning Instructions   50Kb PDF file donated by A. Nony Mous Generic tuning instructions for their pass/reject duplexers. TPRD-1554 & 1556 Duplexers   92Kb PDF file donated by A. Nony Mous These are VHF pass-reject duplexers good for 350 watts. The TPRD-1554 is VHF 4 cavity and the 1556 is 6 cavity. TPRD-4544 & 4744 Duplexers   104Kb PDF file donated by A. Nony Mous UHF 4 cavity pass-reject, 250watts.   The 4544 model is for 400-470 MHz, the 4744 is for 470-512 MHz. TPRD-9044 Duplexer   88Kb PDF file donated by A. Nony Mous 890-960 MHz 4 cavity pass-reject, 250 watts If 4 cavities are enough in your RF environment then this is an ideal unit for 900 MHz amateur repeaters. TX-RX Overview of TX-RX Low Band Duplexers 2 mb PDF   Also has some Tech Aid documents Overview of TX-RX High Band & 220 MHz Duplexers 2 mb PDF   Includes a chart explaining their model numbering system Hint: The center digit pair are the magic numbers: 13=30-40 MHz,   14=38-50 MHz,   29=88-108 MHz,   36=132-150 MHz,   37=144-174 MHz,   38=132-174 MHz,   41=148-174 MHz,   52=215-250 MHz,   65=406-430 MHz,   66=442-450 MHz, and 97=1215-1300 MHz. Data Sheet on the TX-RX model 28-37-02A 144-175 MHz duplexer 2.7 mb PDF If a 4-cavity model is enough for your situation, this is the ideal model for a 2m repeater - it will handle 400 watts at 500 KHz spacing with 85 db of isolation.   Otherwise look at the 28-37-11, it's the 6-cavity version with 100 db.   Personally, I'd rather have the extra headroom of the 6-cavity version.   And TX-RX will sell you an upgrade kit of the extra cavities and cables. Instruction Manual Vari-Notch Duplexers (6" Cavities)   189 kb PDF While this is a generic manual on the TX-RX duplexers it contains a chart saying it pertains to the following units: 28-13-01F (30-40 MHz),   28-14-01F (38-50 MHz),   28-28-02A/G (66-88 MHz),   28-36-02A/G (132-150 MHz),   28-36-11E/G (132-150 MHz),   28-37-02A/G (144-174 MHz),   28-37-11E/G (144-174 MHz),   28-37-08G (144-174 MHz),   28-65-01A (406-430 MHz),   28-65-05A/G (406-430 MHz),   28-70-01A (450-470 MHz),   28-70-07A/G (450-470 MHz),   28-69-01A (470-512 MHz),   28-69-04A (470-512 MHz) WACOM and Remec WACOM started out as Waco Communications in Waco, Texas. At some point WACOM was bought by Remec, and in November of 2001 was sold to TX-RX. Notes on the Wacom WP-641 BpBr Cavity   by Kevin Custer W3KKC Field Tuning Instructions for Remec WP-604, WP-609, WP-612, WP-621, WP-629, WP-639 and WP-641 VHF Duplexers   donated by Eric Lemmon WB6FLY Field Tuning Instructions for Wacom WP-604, WP-609, WP-612, WP-621, WP-629, WP-639, WP-641 and WP-652 units   donated by Ivan OZ1HYG This is an earlier version of the above file (it's from Wacom), and the instructions are a little different. Field Tuning Instructions for Wacom WP-678-R2 and WP-665-R2 UHF Duplexers   donated by Eric Lemmon WB6FLY Spec Sheet for WP-604 (low band, 4-cavity)   371kb PDF Spec Sheet for WP-621 and WP-641 (high band, 4-cavity)   218kb PDF Spec Sheet for WP-623 and WP-643 (high band, 6-cavity)   178kb PDF Spec Sheet for WP-629 and WP-639 (high band, 4-cavity)   188kb PDF Spec Sheet for WP-652 and WP-653 (220mc, 4-cavity)   248kb PDF   This is the March 1997 version of the sheet. The September 1985 version (no image yet) has a few differences: the older sheet says 220-300 MHz, 1.0 MHz min. spacing, 350 watts max, gray enamel finish. The newer sheet says 210-260 MHz, 1.0 MHz min. spacing, 200 watts max, black enamel finish. The frequency response charts look identical, as do the loss & isolation specs. Spec Sheet for WP-665 and WP-678 (UHF, 4-cavity)   215kb PDF WP-687-3943 Catalog Sheet (900 MHz, 4-cavity)   145kb GIF WP-687-3943 Spec Sheet (900 MHz, 4-cavity)   1.65mb PDF WP-687-3943 Test Sheet (900 MHz, 4-cavity)   1.35mb PDF WP-687-3943 Field Tuning Instructions (900 MHz, 4-cavity)   409kb PDF WP-4941-7941 Spec Sheet (900 MHz, 2-cavity)   2Mb PDF Antennas Repeater owners tend to have favorite antennas - some prefer colinear antennas ("fiberglass sticks"), others prefer dipole arrays. Personally I prefer grounded dipole arrays as colinear antenas are more prone to duplex noise (see the article titled "Help!! I have a crackling noise in my repeater" by Kevin Custer W3KKC elsewhere on this page). Dipole arrays are immune to that but can have phasing harness degredation if you are not careful. Picture four loop dipoles side mounted on a steel mast. Suddenly one day you notice that the coverage has gone to hell. When you check the antenna with a SWR bridge you discover that you still have a 1:1 SWR. Phasing is the key concept here. The RF is fed to the dipoles by means of a cable harness of critical-length coaxial lines that accomplish both the phasing of the dipoles and RF power division. The VERTICAL pattern of the antenna is determined partly by the RF phase relationship between the dipoles. When the antenna is new, the phase relationships are perfect and the RF goes where you want it. As the coax in the harness ages, moisture can infiltrate the coax and connectors unless your waterproofing is perfect. The moisture deteriorates the coax dielectric (which changes the velocity) and corrodes any non-silver-plated center conductor and braid. This slow velocity change will cause the phasing to change. Since the apparent gain of the antenna is determined by the vertical pattern (and it is determined by the phasing between elements) the pattern of the antenna will change. A perfect SWR does you no good when your RF power is going straight up in the air or straight down into the ground! So if you use a dipole array then you want to be an annoying perfectionist about the phasing harness, the waterproofing of the cable, and of the connectors on it. And if you are looking at a new antenna you might want to look at the ones that have the harness inside the mounting tube. And as said above, don't go cheap on the antenna or feedline. You can have the best sounding repeater on the planet, but it's both worthless and useless if the users can't get into it or hear it because you used a Ringo Ranger 15 feet off the ground and RG-8 or RG-213-type feedline (don't laugh, I've seen it). Radio Antenna Engineering   By Edmund A. Laport   This is a 1952 textbook and the original copyright has expired. The PDF file is 38.5 Mb. At the time, Mr. Laport was the Chief Engineer of RCA International Division. While the book is oriented towards antennas up to 30 MHz, the Preface is worth reading (4 pages) as theory doesn't depend that much on wavelength. The Introduction (11 pages) has some math, but it's also very interesting. The W1GHZ Online Microwave Antenna Book   By Paul Wade W1GHZ (ex N1BWT)   An excellent text, and worth reading.     (offsite link) Antenna Design for Omnidirectional Repeater Coverage   By James Ruxlow N9SN What do you do when you need omni coverage, and you have to side mount the antenna to a triangular tower that is over fifteen feet on each face? The Western Illinois ARC figured it out. And their solution works well. Precipitation Static and Duplex Radio... The Phenomena and the Cure!   Rain and snow clouds contain more than rain and snow   By Kevin Custer W3KKC. Help!! I have a crackling noise in my repeater   Why it's there and how to cure it...   By Kevin Custer W3KKC. Vertical and Horizontal antenna separation charts   Provided by Kevin Custer W3KKC. 440 MHz Folded Dipole Repeater Antenna   (222kb PDF file)   This is a two page PDF file of the classic 73 Magazine construction article by Chuck Kelsey WB2EDV - Yes, you can build yourself a DB-224 folded dipole array. Information on a Cycloid Dipole (also known as circular polarization) antennas   By the WA7X crew     (offsite link) "Calculating Downtilt" by Scala Division of Kathrein Corp (Technical Bulletin #112)   39kb PDF Omni-Directional Gain Vertical Collinear Construction Project     By Mike Collis WA6SVT Yes, you too can build a Stationmaster - for any frequency from 2 meters to 1.3 GHz Some variations and constructions ideas on the WA6SVT collinear   by Kevin Custer W3KKC One ham's experiences with the WA6SVT antenna   by Paul Kelly N1BUG Here's the construction article promised in the above article   by Paul Kelly N1BUG Build A 9 dB, 70cm, Collinear Antenna From Coax   By Michael Martell N1HFX   (offsite link) Yes, you can build a decent home base station antenna from RG-58 coax. Fiberglass Antenna Painting Procedure   by Celwave Corp., provided by Mike Dees N3EZD   See the next article as well. Some Notes on Fiberglass Antenna Painting   Comments from several folks that accompany the above article. Retuning a Stationmaster type antenna   By Jim Barbour WD8CHL Cheap Yagi Antennas for VHF/UHF   By Kent Britain, WA5VJB for the Clear Lake Amateur Radio Club of Houston, Texas. This article describes a easy-to-build inexpensive yagi (beam) antenna that can be built for 2m, 220, 440, 900 or 1296 MHz. A QST article on a homebrew discone   375 KB PDF file from the May 2003 issue The article describes it as 144 through 450 MHz but it would work just fine at Civil Air Patrol (CAP) frequencies (just plug 139 MHz into the sizing formula) and at GMRS frequencies. I'd use copper screening, not steel hardware cloth. And discones aren't limited to 2m and up, as this photo of a commercial 25-75 MHz discone will show (photo by WA6ILQ). While it looks like the support mast is on a rooftop air conditioner, it is actually mounted into a tripod base about 20 feet on the far side of the unit. A search of the QST archives shows an article on constructing a 40 through 10 meter discone in the July 1975 issue and a followup/correction in September. A Copper Cactus Dual-Band J-Pole Antenna Project   By Tony Petersen N7QVC A homebrew Digital TV Antenna Project   By Make Magazine If you are going to make one I suggest you seal the wood first. If anyone has any other good homebrew antenna projects let me know. There is a section on mobile antennas towards the bottom of this web page.   Advanced Electronic Applications / AEA For information on AEA antennas including the Isopole please see the AEA page.   Andrew 2008 Andrew Corp. Base Station Antenna Systems Product Selection Guide   2.99 MB PDF   Celwave A detailed drawing by Skipp of the Celwave-built Motorola TDE6090A welded yagi beam antenna   69KB PDF file   This is a two page PDF, the first page is Skipp's measurements, the second is the Celwave drawing.   There is enough information here that anyone with a welder could make their own very strong winter-ice-proof welded 10db gain yagi antenna.   Note that the element length measurements shown in the diagram are for 420 MHz frequencies. If you need a good strong UHF point-to-point link antenna then use this design as your model. A PDF of a fax describing the Cellwave low band dipoles   166 KB PDF The products include the PD320 (one element, 2.5db, 10 feet of tower space), PD322 (two elements, 5.0db, 24 feet) and PD324 (four elements, 7.5db, 55 feet) side-mount antennas. Celwave 220 brochure   580 KB PDF Back when 220-222 was stolen from the hams to be a new land mobile radio band Cellwave put together a brochure with the tech specs on all of their 220 products plus three sample system diagrams. The products include the PD220-8, PD220DT, 92.0101, and 93.0024 antennas, the TJD220-5T transmitter combiner, PD1604B cavity, PD5042-2 duplexer, PD5279 cavity, PD5280-1, PD5280-2 and PD5280-3 duplexers, PD1602 low-pass filter, PD506-2A duplexer, PD5091-2A dual notch cavity, PD5090-2B/3 bandpass filter and the PD5090-2A bandpass cavity. Decibel Products / RFS IMPORTANT !! A letter suffix indicates the range that an antenna is built for: 138-150 MHz, 150-160 MHz, 155-165 MHz, or 164-174 MHz but that the actual end frequencies and the assigned letter is NOT consistent across the product line.   For example, on one product (i.e. one model number) an "A" model might be 150-159 MHz, while on another product an "A" model might be 150-155 MHz.   While in many cases an "A" range is the one that starts at 150 MHz, it can vary with EACH antenna model number: one antenna might have "A" be the 138-150 MHz range, and another might have "E" be the 138-150 MHz range.   Be very careful that you check your range letter definition before you spend your money (on new or used antennas) ! Data sheet on the DB201 ground plane omni antenna: This is the so-called "bent-over" ground plane that comes in two models. This is a one-page version from the Allen Telecom vintage   717kb PDF file It comes in two versions, one for 30-174 MHz and the other for 220-512 MHz This is a two-page version from DB Products   dated 1995. It was available for any frequency from 30 MHz to 512 MHz. Cutting chart for the DB-201     Page 1 159kb   Page 2 111kb   Allen Telecom version courtesy of Russ Stafford W3CH The same info in a 4 page PDF, better presented, from DB Products . A poor scan of the data sheet on the DB-212 side mount omni antenna (33-88 MHz) Page 1 260kb   Page 2 203kb   Drawing of the diagram on Page 2 34kb Here's the Andrew version of the same catalog sheet (and a much better scan), courtesy of Allen Wilde N1IOE and here's the DB-212 tower mounting instructions, also courtesy of Allen Wilde N1IOE   You can move a low band DB212 to 6m by basically freeing up the trombone section of the antenna, adjusting the postion, then locking it down again. Just measure the current length of the dipole and then multiply this length by (current-freq divided by the new-freq). So if the current length is 184 inches and the current freq is 46 MHz and your destination frequency is 52.5 MHz the new length (in inches) is therefore 184*(46/52.5).... To change the length you will need to remove the pop-rivet and a little dimple that the production line uses to hold the trombone in place until the rivet is installed. Sometimes the VSWR depends on the tower face. If you want to super tune the antenna set the antenna up on a tower leg several feet off the ground, preferrably a little over a 1/2 wave if you can do it. Then adjust the trombone to the length you calculated and apply a little RF power and check the reflected power. Then get a long stick and start moving the trombone slowly while watching the reflected power. When you get the best possible VSWR, stop and redo the rivets. Personally I'd add a bead of non-acidic silicone bathub sealer to water-seal the joint. Detailed measured diagram of the low-band four-element DB-212 wiring harness     Courtesy Bill Cotter N4LG. WA1ZYX's web page about modifying the DB-212 elements for 6 meters     Off-site Link. Detailed harness lengths for various DB-222 multi-bay antennas     Courtesy of Paul Dumdie W9DWP. DB-224 catalog data (PDF files): Decibel DB224 Data Sheet  156kb   Andrew DB224 Data Sheet  140kb   DB224 Instruction Sheet  153kb Here's the instruction sheet that comes in the box with the DB-224   Page 1 964kb   Page 2 1,032kb   Page 3 819kb   Courtesy John Lock KFØM. The DB224 is the standard antenna that all other 2m /  high band repeater antennas are measured against.   These guys cost a little more than a fiberglass antenna but will easily last 20-30 years, and don't have the cracked joint duplex noise problem, nor will you have a pile of fiberglass toothpicks on the ground after a nearby lightning strike.   How many Hustler, Comet or Diamond antennas will you go through in 20-30 years? The DB-224 is rated at 80 MPH winds, but that's wishful thinking unless you side mount it with clamps on BOTH the top AND the bottom.   Frankly, chosing to mount your antenna on the tower top only to get a few extra feet isn't worth a bent or broken metal support tube, and if your antenna is side mounted (even if the tip is only 6 feet down from the tower top) the tower itself (or someone else's antenna) can be the lightning rod and take the hit. Note that all "DB-224"s are not the same... they may all be tower-mounted exposed dipole arrays with 6 to 8db of gain (depending on the pattern), it's the suffix letter that is of utmost importance: the DB224-A model is 150-160 MHz circular pattern, the DB224-B model is 155-165 MHz circular pattern, the DB224-C model is 164-174 MHz circular pattern, the DB224-E model is 138-150 MHz circular pattern (but try and find one second hand...), the DB224-FAA model is 127-141 MHz circular pattern (it can be shortened to 2m), the DB224-F model is 160-170 MHz circular pattern, the DB224-J model is 276-285 MHz circular pattern, and the DB224-JJ model is 220-225 MHz circular pattern, the DB224E-A model is 150-160 MHz offset pattern, the DB224E-B model is 155-165 MHz offset pattern, the DB224E-C model is 164-174 MHz offset pattern, the DB224E-E model is 138-150 MHz offset pattern (again, try and find one second hand...), and the DB224E-JJ model is 220-225 MHz offset pattern, The DB224 series can be ordered as a single or dual antenna. Just modify the model number by adding an "S" in the right spot - a DB224-JJ single antenna becomes a DB224S-JJ as a dual antenna.   It amounts to separating the elements into two independent antennas on the same mast.   Each antenna has a separate feedline terminated at the bottom of the mast. A DB224ES-A or DB224ES-JJ is a dual feedline antenna with the offset pattern. And I've been told that at one point (maybe still can) you could order a new DB224 less the tubular mast, and supply your own. Supposedly one group built up a "single antenna" as defined by their tower agreement that was made up of a UHF stationmaster-type fiberglass stick on the top of an extended length tube, a VHF DB224 in the middle, and a end-mount UHF beam clamped a few inches above the bottom end of the tube. A detailed drawing of the DB-224-A and DB-224-E   104kb PDF file   A 2-page PDF donated by Skipp.   Note that the element length measurements are shown for both the "A" (150-160 MHz) range and the "E" (138-150 MHz) range. There is enough information here that anyone with some experience bending aluminum tubing can build one for themselves. Or if you are going to build your own and want extra strength you could use aluminum rod. Another detailed drawing of the DB-224-E   60kb PDF file   Donated by Doug Zastrow WBØUPJ.   Note that the element length measurements shown in the diagram are for 136-150 MHz frequencies. Conversion calculations for moving your DB224 to a different band split.   90kb PDF file   All of the magic calculations plus coax types necessary to redo your DB224's wiring harness and set the element length and spacing. DB-228 catalog data (PDF files): DB228 Data Sheet  87kb   DB228 Instruction Sheet 60kb Here's the instruction sheet that comes in the box with the DB-228   772kb PDF   Courtesy John Lock KFØM Note that on this antenna an A suffix indicates 150-160 MHz, B=155-165 MHz, C=164-174 MHz and E=138-150 MHz. The DB-228 is essentially two DB-224s on one 41-foot long mast, and can be ordered with a phasing harness that makes it one antenna - and that makes it the ultimate 2m repeater antenna (10 to 12db depending on the pattern).   The catalog sheet shows the "normal" mounting has being a split mount: the top half is above and the bottom half is below the top of a tower (i.e. the bottom half is side mounted with two clamps at the middle and bottom); however, unless you want to be the lightning rod the DB228 can be fully side mounted with the two brackets at top and bottom, or an optional third bracket can be added in the middle (I certainly would, especially in any area that has a problem with high winds, antenna icing, or both). Or if you need extra RX-TX separation: order it with the -S (split kit) option and use it with two feedlines and a split duplexer as separate DB224 receiving and transmitting antennas. DB's installation instruction sheet on the DB-264   155kb PDF   Courtesy of Paul Kelly N1BUG The DB-264 is a 4 element dipole array that is constructed for any 10 MHz segment of 150-285 MHz.   This is the model that has the feed harness hidden inside the support pipe. I've seen one of these on 224 MHz, and it's rugged! Anyone have any data sheets or instruction sheets on the DB-304 ?? DB's instruction sheet on the DB-314   114kb PDF   Courtesy A. Nony Mous The DB-314 is essentially a 8 UHF dipoles (a DB-408, 6.6db gain) and 4 high band dipoles (half of a DB-304, 3.2db) on the same mast, with separate feedlines.   If you need a commercial grade dual band antenna, this is it.   Or if you are limited to one antenna, then order this guy and use it as separate 2m and 440 antennas with two feedlines, or with a pair of commercial-grade TX-RX Corp. (or similar) "diplexers" that put both antennas on one feedline. But don't try and use one on a 147.09 MHz; repeater paired with a second repeater whose input is 441.275 MHz, or 147.36 MHz; and paired with 442.075 MHz; (do the math... and it doesn't matter what antenna you have in that situation). Skipp's measurments drawing of the DB-402-B   26 KB PDF   An early 4 dipoles antenna. Measurements are for 450-470 MHz. The DB-404 UHF dipole array is two pairs of UHF dipoles mounted to a mast.   Photo   Here is the factory data: (PDF files) DB 404 Data Sheet  93kb   DB 404 Instruction Sheet  131kb   Catalog sheet Page 1  879kb   Catalog sheet Page 2  568kb A detailed drawing of the DB-404-B   Donated by Skipp.   Note that the element length measurements shown in the diagram are for 450-470 MHz frequencies. A detailed drawing of the DB-404-D   Donated by Skipp.   Note that the element length measurements shown in the diagram are for 488-512 MHz frequencies. The DB-408 is essentially two DB404s stacked on one longer mast (almost 9.5 feet long) and can be ordered with one or with two feedlines (the "split kit").   Specify Omni or Offset pattern when ordering, and if top or side mounting when ordering. For side mounting order the DB5012 mounting kit. Here is the DB408 UHF dipole array factory data: DB408 Data Sheet  93kb   DB408 Instruction Sheet   80kb   (PDF files) On this antenna the power limit is 250w, the frequency range A = 406-420, B = 450-470, C = 470-488, D = 488-512. The "E" range is either 482-494 or 440-450 depending on which catalog you read, be very, very careful when ordering one. Do it by frequency range, not suffix letter. A detailed drawing of the DB-408-B   300kb   Donated by Skipp.   Note that the element length measurements shown in the diagram are for 450-470 MHz frequencies. DB411 UHF dipole array factory data: (PDF files) DB 411 Data Sheet  75kb     DB 411 Instruction Sheet  217kb A detailed drawing of the DB-411-B   25kb PDF   Donated by Skipp.   Note that the element length measurements shown in the diagram are for 450-470 MHz frequencies. The DB-420 is essentially two DB408s stacked on one longer mast and can be ordered with one or with two feedlines (the "split kit").   Specify Omni or Offset pattern, and if top or side mounting when ordering. A drawing of the DB-420-B phasing harness   140 KB PDF This is the 450-470 MHz version.   Anybody have a drawing (or the measurements) for 440-450 MHz ? The data sheet on the DB420 UHF dipole array   113kb PDF file   The DB420 is an array of 8 dual dipoles that can be configured as a single 8-element antenna or as two 4-element antennas on the same mast (conversion requires a different harness). The DB420 UHF dipole array Assembly and Mounting Instructions   145kb PDF file Factory 1-page data sheet on the DB-492, DB-493 and DB-498 806-960 MHz Yagi beam antennas   130 KB PDF This is the data sheet on the welded beams that are 6, 8 or 9DB. The 492 and 493 are light duty, the 498 is heavy duty. Phasing harnesses for 2 or 4 antennas are available for up to 15DB of gain. Factory data sheet on the DB5004 / DB5030 Outrigger   378 KB PDF This is the data sheet on the fiberglass outrigger that supports the Stationmaster and SuperStationmaster style fiberglass monopoles. You want to use at least one, in really high wind/bad weather areas I've seen two on a 21 foot SuperStationmaster).

	Motorola
		The 1964 manual for the TAD1000-series coaxial VHF antennas   donated by Skipp   Description, Installation, Assembly, Parts. 150KB PDF file Covers the models TAD1001x, TAD1002x, TAD1003x, TAD1004x, TAD6071x, TAD6072x, TAD6073x, TAD6074x (where "x" is an "A" or a "B").
		VHF unity-gain antenna model information and specifications for the TAD1010-series antennas   donated by Skip   255KB PDF file More info on the 1001, 1002, 1003 and 1004 models listed above, plus info on the TAD1012x, TAD1013x, TAD1014x, TAD1021x, TAD1022x, TAD1023x and TAD1024x series (where "x" is an "A" or a "B").
		VHF 3dB-gain antenna model information and specifications for the TDD602x-series antennas   donated by Skip   240KB PDF file Covers the models TAD6021A, TAD6022A, TAD6023A and TAD6024A units.
		VHF 5.5dB-gain antenna model information and specifications for the Motorola branded Stationmaster style antennas   donated by Skip   268KB PDF file This sheet covers the models TDD6071A, TDD6072A, TDD6073A, TDD6074A, TDD6075A, TDD6081A, TDD6082A, TDD6083A, TDD6084A, TDD6085A, TDD6090A, and TDD6100A.

Calculators (dBm / voltage, intermod, fade margin, etc.)
	Converting between dbm and millivolts or microvolts   A no-math graphical calculator   it's only a xerox copy of the metal rim of a attenuator wheel from a Measurements Corp. Model 80 RF Signal Generator... but it's very handy.   Courtesy of Ray Von Neumann K6PUW I suggest that you print this out and tape it to the front panel of your signal generator that is calibrated in uV and mV only. Once you realize how dbM numbers work you will find yourself referring to it on a regular basis.
	Converting between dbm and millivolts or microvolts   A no-math tabular calculator (a lookup table).   The above xerox of the attenuator scale is easier to use.
	dBm to Microvolts Conversion Chart   By IFR Corp.   The above xerox of the attenuator scale is easier to use.
	An online intermod calculator from AudioTechnica     Note that this is oriented to wireless microphones, but since it handles up to 30 frequencies it is very handy.   (offsite link).
	Another downloadable intermod calculator   This one is shareware written by KE6QH.
	This downloadable calculator program figures intercept points and device intermod levels     This one is is from Kessler Systems Inc.   (offsite link)
	This online calculator program from TCS Consultants, Inc.   saves the site description to a 'cookie' file on your computer.   (offsite link)
	Online fade margin calculator program from TCS Consultants, Inc.   This is neat!   (offsite link)
	FCC HAAT (Height Above Average Terrain) Calculator   (offsite link to the FCC web site)
	FCC Coordinate Calculation Program   (offsite link to the FCC web site) This is a useful calcualtor for point-to-point links... "This program will calculate the end coordinates, in degrees, minutes and seconds, given an initial set of coordinates, a bearing or azimuth (referenced to True North or 0 degrees), and a distance...."
	FCC Coordinate Conversion Program   (offsite link to the FCC web site) "This utility permits the user to convert latitude and longitude between decimal degrees and degrees, minutes, and seconds. For convenience, a link is included to the National Geodetic Survey's NADCON program, which allows conversions between the NAD83 / WGS84 coordinate system and the older NAD27 coordinate system. NAD27 coordinates are presently used for broadcast authorizations and applications."
	FCC Distance Calculation Program   (offsite link to the FCC web site) "This program will calculate the distance and azimuth (referenced to True North) between two sets of coordinates on the earth." The last four calculators above are courtesy of Dale Bickel of the USA Federal Communications Commission. The FCC also has a number of "Conversions" calculators including FM Channel to Frequency, FM Frequency to Channel, TV Channel to Frequency Band, Feet to/from Meters, Miles to/from Kilometers, dBu to/from mV/m, kW to/from dBk, Relative Field, Transmission Line Efficiency, and more.
	An old DB Products DOS program that calculates down-tilt for antennas   128kb ZIP file
	An old DB Products DOS program that plots some antenna patterns   383kb ZIP file
	An old DB Products DOS program that gives you some insight into the effects of side-mounting vertical antennas  134kb ZIP file The above three programs were supplied by Dave Gartner WD6AXM.

Mobile Antennas
Hints:
(1) Don't use solid center conductor coax on a mobile antenna (especailly on something that moves, like a trunk lid). Yes, it seems obvious, but you'd be surprised...
(2) Punch-mounts are 20 times better than clamp-on-the-edge-of-the-trunk-lid mounts and 50 times better than magnetic mounts. If you have to use a mag mount use a 1/2 wave antenna intended for zero-ground-plane installations (like what would be on a motorcycle saddle bag or a Corvette rear deck). Larsen makes some good ones, as does Tram (the model 1155 is VHF, the 1175B is UHF and both work well).

Think about this: You have a 5/8 wave antenna with a flexible whip. The whip is a radiating element. At 60 MPH the top foot of that whip is bent back almost horizontal.   What kind of a pattern does that give you?   I switched my 2m/440 MHz mobile to a center-loaded dual band whip with a fairly stiff rod about a year ago.   My signal flutter was reduced by over 50%...

	A mobile coaxial sleeve antenna for 2m   450 KB PDF file from the Aug 2001 issue The sleeve vertial (actually a coaxial dipole) is handy when you have no ground plane to work with, like on a bicycle, a motorcycle saddle bag or a Corvette rear deck.
	A Motorized Mag Mount for Mobile Antennas   1.53 MB PDF file from the May 2005 issue An interesting modification to an off-the-shelf Diamond mount.
	Base and mobile antenna cutting chart from Larsen Antennas    a 668kb PDF file from the Larsen web site, specifically the Technical Reference page.
	Mobile antenna patterns and designations    a 1.6mb PDF file from the Larsen web site.
	Low band radios that cover a wide frequency range (like the GE Delta, GE Rangr, Motorola Syntor X or Syntor X-9000 which covers 28-54 MHz in one range) have a big problem: the antenna bandwidth is much narrower than the radio is - most low band antennas are limited to about 1mhz in bandwidth.   Autotuning antennas have been around for a while, but a good design is fairly recent (the so-called "screwdriver" design).   A long time ago Motorola came up with a no-moving-parts solution: a "Diplex Antenna Matching" kit that allowed two differently cut low band whip antennas on one radio (i.e. one could be on 36 MHz and the other on 43 MHz), and done in a way that prevented them from interfering with each other.   The two antennas can be cut to any two low band frequencies.   Here is the complete documentation on the kit (Motorola manual part number 68-80100W86, a 1.9mb PDF), which contains three pages of info - enough to duplicate it yourself. If you need more than two fixed 1-mhz-wide "windows" then you need a good screwdriver antenna and a self-contained autotuner like an SGC.
	The KØBG web site   (link to another web site) Alan Applegate KØBG lives in Roswell, New Mexico and has created a very good reference web site for mobile amateur radio operators. I was pointed to it by a police department radio tech. While the site has a lot of material oriented to HF mobile, there is a lot of information that is relevant to VHF operation as well. Just look at the index along the left edge. If you look at nothing else, the Alternators and Batteries page and the Antenna Mounts page is worth your time.
	W8JI's page on Inductors and Loading Coil Current (Mobile and Loaded Antennas)   (link to another web site) Charles Rouch has a good web page on loading coils and how they work. It's HF oriented but the math is the same.
	Urgent Communications Mobile Radio Installation Notes   (link to another web site) Urgent Communications is a two-way radio industry publication, and their web site has some notes on mobile radio installations.
	You've heard of co-phased antennas? Well, here's the co-tanger antenna.

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