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Information on Two-Way Radio Specific Test Equipment Web page created by Kevin Custer W3KKC Some information added by Mike Morris WA6ILQ Mike knows very little about this equipment so please don't ask!

If anyone has any additional Helper documents (especially their Applications Notes) or Helper history I'd be happy to add it to this web page.

Info from Mike WA6ILQ:
I first ran into Helper Instruments equipment at a 2-way shop around 1983-1984. They had an original Sinadder sitting on a shelf over the workbench. The shop owner said that he had bought it at the Helper booth at a trade show sometime around 1977-1980 from the owner / designer / builder (would have been Bill Detwiler). It had a note on the front: "Modified for floating I/O" - they had added 1:1 audio transformers inside to prevent grounding the low side of the audio. When the Sinadder was designed all of the radios (Motracs, Mastr Pros, etc. had audio output transformers between the audio output stages and the speakers. When the radio manufacturers went to floating speaker outputs (like in Maxtracs and almost every product line after) any test equipment that connected to the speaker leads required an audio transformer in line to "float" (isolate) the input of the test equipment.

Helper Instruments Company was located at PO Box 3628 (later at 131 Tomahawk Drive), Indian Harbour Beach, Florida 32937 (407) 777-1440 or (800) 327-9308. The company was founded by Bill Detwiler (callsign?) in 1975 and made land mobile radio test equipment to help a bench or field technician properly maintain station or mobile radio equipment before the individual tests were incorporated into modern test gear. One example was the ability to test SINAD sensitivity, another was an RF Millivoltmeter to help tune the receiver tuned circuits, tuned lines or helical resonators.

Bill passed away December 1989 and his wife Betty and daughter Susan ran the company for a while. Zetron acquired Helper around 1999. They elected to continue some of the Helper line, but not the RF test equipment, such as the Millivoltmeter, the Modulation Monitor, and the SM-512, SM-520 and SM-1000 Service Monitors. As part of the acquisition the Helper web site was folded into the Zetron web site. The web pages for the Helper products that they chose to continue had this at the bottom of each page:

Helper Instruments | Phone: 1-800-327-9308 | Fax 1-425-820-7031
12034-134th Ct. NE, Suite 100, Redmond, Washington 98052 USA
Helper-Instruments. A Division of Zetron, Inc.

Useful Helper Documents:

Helper published several applications notes. We'd appreciate the donation of the missing ones. If all you have is a paper copy we'd be happy to scan it and return it.

• Sinad Alignment For Optimum Performance – We have a PDF below of this one for download below.
• Everything you need to know about SINAD
• Line Measurments Speed Control System Troubleshooting
• What the Modulation Monitor Has Missed
• Troubleshooting With Your Power Supply
• R.F. Voltmeters

	Sinad Alignment For Optimum Performance   354 kB PDF This is the only Application Note that we have - it is the doocument that got Helper started. It is a quite readable explanation of the the theory behind SINAD measurement.
	An Early Helper Catalog   2.6 MB PDF file donated by Skipp
	Helper Instruments Catalog   1.43 MB PDF I believe this is the last catalog that Helper released while Bill Detwiler (the founder) was alive.
	Helper Instruments Final Catalog   9.53MB PDF file   Donated by Dennis Casey KØGWK This one details the era when Susan, Bill's daughter took over the company after Bill passed away.
	Helper Instruments Desktop Reference   322 kB PDF file   Donated by Eric WB6FLY A collection of charts, tone lists, SINAD test procedures, "and an occasional discrete mention of the time saving, money making test instruments by Helper Instrument Company." We think this is older than the file below although it has the same information in it.
	Helper Instruments Desktop Reference   439 kB PDF file   Donated by John K3KR A collection of charts, tone lists, SINAD test procedures, "and an occasional discrete mention of the time saving, money making test instruments by Helper Instrument Company." We think this is newer than the file above although it has the same information in it.

Equipment Manuals:

	Sinadder model S-101   508 kB PDF file     Photo 1   Photo 2 This is the manual for the original small sloping-front "Sinadder" unit from the late 1970s, complete with parts layouts and schematics. After they came out with the Sinadder II this became known as the "Sinadder I". Despite the age, it's still a very useful test bench instrument.
	Sinadder model S-101   305 kB PDF file This is another manual for the original small sloping-front "Sinadder" unit, with the 1992 schematic revision and a 1999 parts list.
	Sinadder 3   Front Photo 1   Front Photo 2   457 kB PDF file Donated by Eric Lemmon WB6FLY This is the manual for the later flat-front Sinadder model 3. Also see the Sinadder 5 Ground Lift Modification below.
	Sinadder Linear 5 (model SL-105) with optional CML-1 addendum   1.4 MB PDF An improved version with split pages 1.9 MB PDF The SL-105 was available both with and without the CML-1 option (used in cellular applications). There were later units that had a different front panel (see this photo). It is complete with parts layouts and schematics for the plain unit. This PDF file does not have the schematic for CML option. Here's a photo of the front of a CML-1 Sinadder provided by Gary KJ4RED. Here's a photo of the rear of a CML-1 Sinadder provided by Gary KJ4RED. Note that SL-105s were initially built in the SL-101 case, and mid-production switched to the case shown.
	Sinadder Linear 5 (model SL-105)   1.6 MB PDF donated by Paul N2XZF This copy has a bit less gray background than the one above. No mention of option CML-1 is present in this manual.
	Sinadder Linear 5 (model SL-105) Ground Lift Modification   310 kB PDF by Paul N2XZF This simple mod, which also applies to the Sinadder 3, removes the earth ground on the test input leads, which could destroy some audio output amplifiers that can't be grounded (such as the Motorola GM300, Spectra, etc.).
	Lineman model LM-106   416 kB PDF file   This unit is used to test the AC and DC characteristics of the leased phone lines used to control remotely located base stations. It is also a very useful bench test instrument.
	Modulation Monitor model MM901   476 kB PDF file   Donated by John K3KR This unit works with an FM receiver. It gets its input signal from the 400, 450, or 455 kHz IF circuit. ICs: U1 = MC3357P; U2, U3, U7, and U8 = LM348N; U4 and U5 = CA3130E; U6 = LM741CN. Service Note: "If readings appear low, check and replace C24 and C25."
	Audio Frequency Counter model Toner-II   769 kB PDF file   Donated by John K3KR This unit displays frequencies from 50 Hz to 9,999 Hz. ICs: U1 = LM348N; U2, U3 = CA3130E; U4 = MC14046B; U5 = CD4518BE; U6 = SCL4077A/BE; U7 = ICM7207AIPD; U8 = ICM7224IPL; LCD DISPLAY = PURDY/AND # FE0202-C. Service Note: "If the unit has difficulty locking onto CTCSS tones (but higher tones are OK), check and replace C1."
	Millivoltmeter Model RF-801 data sheet   284 kB PDF From the old Zetron web site.
	Millivoltmeter Model RF-801   506 kB PDF   Both this file and the one below donated by Mike Felack WA3WOM Photos: Front panel       Rear panel Helper Instruments RF-801 Millivoltmeter hi-res Schematic   196 kB PDF   This is the component layout and schematic only. Darrel WA7OIB found a probe schematic and created a parts list. Here's an inside photo of the probe. It's similar to the one used on Boonton RF millivoltmeters. He also built his own RF-801 meter; click here for an inside photo.
	Matchbox model MB-500   990 kB PDF Both this file and the inside photo below were donated by Don Mosher WB5BRY Photos: Front panel       Inside       Rear panel
	Helper Instruments SM1000 Operator Manual   12.44MB PDF file   Donated by Dennis Casey KØGWK

Additional photos:

• MB-800 Matchbox front
• Prototype mod box front
• Prototype mod box rear
• SM-512 Service Monitor

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This page initially created 22-November-2012 by splitting all of the Helper equipment from the Test Equipment page.

This web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.