Step 1 (click on the image to see it full size - and you may want to print it)
Up one level (Radio Shack index)
Back to Home
July 19 1998 Expanding the PRO-43 frequency range to 6-1000 MHz by Al Mellon N8KLI This modification is only possible on radios able to be modified to receive the full 800 MHz range (i.e. can be modified for cellular reception - look for the FCC tag, and pray that your unit says FCC ID AA020-300. If it says AA020-300A then your PRO-43 is not modifiable. Scope and nature of the modification: To allow the PRO-43 to receive frequencies from 6 MHz to 1000 MHz. This is accomplished by setting the PRO-43 to non-standard splinter frequencies, the CPU will then step the radio beyond the normal band edges. To derive the non-standard splinter frequencies it is necessary to change the diode configuration matrix, and to use the monitor-search function. The hardware modification should take about thirty minutes. The rest of the mod is programming / search will take as little as 45 minutes (depending on how interested you are in the signals you encounter during the 806 MHz to 30 MHz search. I claim no responsibility for any damage done to your radio by attempting this modification. I will also not be responsible if you use this radio to break the law by monitoring cellular mobile telephone transmissions. Anyone attempting this modification should be comfortable working with surface mounted components and have a reasonable familiarity to the key pad functions of the PRO-43.
Step 1 (click on the image to see it full size - and you may want to print it)* Remove the antenna * Remove the battery pack * Remove the four screws (A) * Remove the rear cover
STEP 2 * Remove the six screws (A) * Using a knife blade, pry the connector at the bottom of the circuit board apart (B) * With the connector (B) apart the top circuit board can be pressed side to side to allow removal of the two hidden screws (C) * Lift the two stacked circuit boards (watch the connectors on the right edge of the main board) * Swing the two stacked boards to the left (as shown by the arrows)
STEP 3 Remove the RF shield by heating the four solder pads (A) and GENTLY prying the shield up at the corners. Watch for any surface mount components! STEP 4 Note the location of diodes D1 - D5 (factory U.S. configurations has diodes D1, D2, D4 in place, and D5 missing).
Diodes D1 - D5 enable the following functions D1 - KEY LOCK switch enable D2 - 30 MHz to 54 MHz enable D3 - 54 MHz to 88 MHz enable D4 - Cellular lockout enable D5 - Cellular 12.5 kHz step enable The normal broad band coverage modification (DRAWING 5A) has D1, D2, D3 in place providing the following coverage: 30 MHz to 88 MHz 118 MHz to 174 MHz 220 MHz to 512 MHz 806 MHz to 999.9875 MHz (30 kHz cellular channel spacing) If your radio does not have D3 then move D4 to position D3 D5 should not be in place See DRAWING 5B. Solder a diode - cathode side (has the line) to the upper side of the D5 position. Make sure that the leads are the proper length to allow this new diode to sit on top of D2 and D3, and that none of the legs touch. Solder the anode side to the lower side of the D1 position. Installation of this diode allows the user to select the channel spacing in the cellular bands. KEY LOCK off at time of power on yields 30 kHz spacing. KEY LOCK on at the time of power on yields 12.5 kHz spacing. By using the monitor memory and changing this configuration in the middle of a search in the cellular band we are able to derive non-standard splinter frequencies. This seems to evade the CPU programming of the allowable band edges, allowing the radio to search beyond normal frequency coverages. At 30.005 MHz, the next downward frequency (at 5 kHz steps) is 30.000 MHz. The CPU then realizes it has reached the lowest valid frequency, so that the next step down the operating frequency is set to 999.9875 MHz. We will store a frequency of 30.0025 MHz in channel 200. Using the DIRECT feature of the radio we are able to tune to a frequency above or below any stored frequency. The CPU reads 30.0025 steps down by 5 kHz and is now at 29.9975. Since the frequency still does not equal 30.000 MHz it is able to step down again. 29.9925 MHz - you probably get the idea. At 2.5 kHz it does jump up to 999.9975 MHz and then to 895.9875 MHz. (Sensitivity drops below 15 MHz, but remains useable to about 6 MHz.) In the procedure below you will store band edge frequencies that can be stepped above or below to grant added coverage. The CPU will not store in memory any frequency outside of the permitted coverage. This necessitates the use of the direct mode. STEP 5 Reassemble the radio STEP 6 Keyboard entries * With the KEY LOCK switch OFF turn the radio on. The unit will now step by 30 kHz steps from 825 MHz to 845 (cellular mobile input channels - base channels are 870 MHz to 890 MHz) * Set the squelch to open (MIN) and volume to low * Enter to the key pad PGM LIMIT 30 ENTER LIMIT 825.120 ENTER DOWN LIMIT DOWN MON (The display should read 825.120 down search) * Turn the KEY LOCK switch ON and turn the radio off * Turn the radio on and set the KEY LOCK switch to OFF * Enter to the key pad (Squelch should still be open.) MANUAL MON DIRECT DOWN (The display should read 825.1075 down search) * Close the squelch to allow the radio to search down. * Use the UP DOWN and the squelch control to stop the radio at 806.0075 MHz * Enter to the key pad MON PGM 194 PGM MON ENTER (Channel 194 has now been programed with 806.0075 MHz) DIRECT DOWN (The display should read 805.9950 down search) * Close the squelch to allow the radio to search down. (I've noticed birdies in the 560 to 700 MHz range.) * Use the UP DOWN and the squelch control to stop the radio at 511.995 MHz * Enter to the key pad MON PGM 195 PGM MON ENTER (Channel 195 has now been programed with 511.995 MHz) DIRECT DOWN (The display should read 511.9825 down search) Close the squelch to allow the radio to search down. Note: From this point on, I have listed frequencies that you most likely will program to your radio. If your frequencies are not exactly the same, they will work as long as the last small digit is a 5 (.5 kHz), and the frequency is within the normal allowable frequency band limits. By this time you have probably noticed that the search step is per the next valid band the radio will encounter in the direction being searched. * Use the UP DOWN and the squelch control to stop the radio at 220.0025 MHz * Enter to the key pad MON PGM 196 PGM MON ENTER (Channel 196 has now been programed with 220.0025 MHz) DIRECT DOWN (The display should read 219.9975 down search) * Close the squelch to allow the radio to search down. * Use the UP DOWN and the squelch control to stop the radio at 173.9975 MHz * Enter to the key pad MON PGM 197 PGM MON ENTER (Channel 197 has now been programed with 173.9975 MHz) DIRECT DOWN (The display should read 173.9925 down search) * Close the squelch to allow the radio to search down. * Use the UP DOWN and the squelch control to stop the radio at 118.0225 MHz * Enter to the key pad MON PGM 198 PGM MON ENTER (Channel 198 has now been programed with 118.0225 MHz) DIRECT DOWN (The display should read 117.9975 down search) * Close the squelch to allow the radio to search down. * Use the UP DOWN and the squelch control to stop the radio at 87.9975 MHz * Enter to the key pad MON PGM 199 PGM MON ENTER (Channel 199 has now been programed with 87.9975 MHz) DIRECT DOWN (The display should read 87.9925 down search) * Close the squelch to allow the radio to search down. * Use the UP DOWN and the squelch control to stop the radio at 30.0025 MHz * Enter to the key pad MON PGM 200 PGM MON ENTER AM/FM (Channel 200 has now been programed with 30.0025 MHz AM) To listen to Rush at noon on WRNO 15.420 MHz * Enter to the key pad MANUAL 200 MANUAL DIRECT DOWN * Use the UP DOWN and the squelch control to stop the radio at 15.4155 MHz * Enter to the key pad UP (The display will now read 15.4175) MON The radio is now locked to the correct frequency (the AFC will lock the radio to 15.420 MHz) To listen to CB-19 27.185 MHz * Enter to the key pad MANUAL 200 MANUAL DIRECT DOWN * Use the UP DOWN and the squelch control to stop the radio at 27.1775 MHz * Enter to the key pad UP (The display will now read 27.1825) MON The radio is now locked to the correct frequency (the AFC will lock the radio to 27.185 MHz) To listen to TV channel 8 audio on 185.760 MHz * Enter to the key pad MANUAL 197 MANUAL DIRECT UP * Use the UP DOWN and the squelch control to stop the radio at 185.7575 MHz * Enter to the key pad MON The radio is now locked to the correct frequency (the AFC will lock the radio to 185.760 MHz) To listen to Civil Air Patrol on 26.620 MHz * Enter to the key pad MANUAL 200 MANUAL DIRECT DOWN * Use the UP DOWN and the squelch control to stop the radio at 26.6125 MHz * Enter to the key pad UP (The display will now read 26.6175) MON The radio is now locked to the correct frequency (the AFC will lock the radio to 26.620 MHz) STEP 7 Ask yourself why Radio Shack did not include shortwave or extended VHF coverage in the PRO-43 software. Answer: They wanted to sell you a shortwave receiver too. - OR - They've just grown accustomed to following the leaders, not being one. Notes: It is necessary to drop below the desired HF band frequency and then search up to re-enable the VHF-LO band circuitry. None of the other bands require this. The lowest frequency I've been able to copy with out modification of the RF cicuitry is 5.8 MHz. The best SWL sensitivity is from 15 MHz and up. I use my 2 meter 5/8 wave HT antenna for SWL and have good results from my office. As with all rigs, an outdoor antenna works far better than an undersized rubber duck. When listening to 10 meter FM check your mode. If the key pad operations must be interupted, it is not neccesary to restart the programing from 825.120 MHz. Simply go to the last memory channel programed with a non-standard splinter channel in the manual channel mode. Then enter to the key pad DIRECT DOWN This will restart the search from the last possible frequency. Steps to enhance the HF receive sensitivity. * Remove L101 * Add the following circuitCx1 = .01uF Cap Cx2 = .01uF Cap Lx1 = inductor - use L101 if not broken (I used an inductor from a Radio Shack Bulk part assortment 273-1601) Cx3 = .047 pF Cap (Approximately) Point 1 = Juntion L101 and C101 and Ant connection Point 2 = Juntion L117 and C205 and R135
Up one level (Radio Shack index)
Back to Home
The Repeater Builder's site does not evaluate the accuracy of materials created by persons beyond its control or supervision. Therefore, although this site links to many additional web sites, The Repeater Builder's site is not responsible for the availability of or the accuracy of any materials contained within those web sites.