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Hy gain ll 40 ch lowers mod

If thats the 2702a version, that PLL uses N codes 224-268, the non a version used N codes 330-286. If your radio uses the 224-268 N codes (easy enough to test with volt meter), then to get on 26.815, you need to bring binary to N code 209 (pin 10 of PLL chip low while on ch 15).

Edit: Had I noticed two schematics, i would have wanted to figure out what radio you had before suggesting anything. I saw hy-gain 2 and clicked the first one I saw in my cbtricks mirror. Sorry. There was two.
 
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brandon7861 said:
If thats the 2702a version, that PLL uses N codes 224-268, the non a version used N codes 330-286. If your radio uses the 224-268 N codes (easy enough to test with volt meter), then to get on 26.815, you need to bring binary to N code 209 (pin 10 of PLL chip low while on ch 15).



Edit: Had I noticed two schematics, i would have wanted to figure out what radio you had before suggesting anything. I saw hy-gain 2 and clicked the first one I saw in my cbtricks mirror. Sorry. There was two.
Cool! I'll look into it!!
Click to expand...
 
Both versions had the usual PLL reference crystal at 10.24MHz, both used a 10.695MHz crystal as well. The difference is in the PLL loop.

On Ch 1, the 2702 "non a" version doubles the PLL reference 10.24MHz to 20.48MHz (dual purpose) to mix with the VCO in the loop mixer. Both the sum and difference are used. The sum of the VCO (17.18MHz) + doubled reference (20.48MHz) = 37.66MHz which goes to the mixer to have 10.695MHz subtracted to get the desired 27.965MHz, while the difference, doubler (20.48MHz) - VCO (17.18MHz) = 3.3MHz, goes to the PLL N-divider where dividing by 330 gives the required (10.24MHz/1048) = 10kHz.

On the 2702a version, rather than using the reference crystal, an 11.80666MHz crystal is tripled to give 35.42MHz. Here, instead of the VCO running at 17.18MHz and taking the 37.66MHz from the mixer as in the other version, this VCO runs at 37.66MHz directly and the difference between the VCO (37.66MHz) and the tripler (35.42MHz) of 2.24MHz goes to the N-divider where 224 becomes the magic number.

This is why looking at those crystals can tell us what the radio is doing. One radio will only have two crystals, the 10.24MHz ref and 10.695MHz offset, and the other version will have a third crystal at 11.8066MHz (or whatever they had on hand).

Edit: so 26.815MHz + 10.695MHz = VCO at 37.51MHz. 37.51MHz-35.42MHz (or whatever that third crystal is x3)= 2.09MHz to divider. N=209. 209 in 9 bit binary is 011010001. The closest to that on the factory wired dial is 011110001 (binary written in P8-P0 order) which is ch 15 (N code 241). So to get 26.815, go to ch 15 and bring P5 (which is pin 10 of the 02A) low.
 
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Kinda over my head with the binary talk but putting a switch on pin 10 will get me to 26.815 I take it?
 
Staybolt said:
Kinda over my head with the binary talk but putting a switch on pin 10 will get me to 26.815 I take it?
Click to expand...
How did you wire it? Explain in detail how you tried and failed.

Also, if you are willing to go through the effort of adding a switch, can you please tell me what the crystals say on them?
 
I know the OP gave up on this one. But I saw the comment about this radio being "NOT able to be converted." It's a PLL02a chassis, there's got to be a way.

I found one on fleaBay and checked to make sure it was the same PTBM036AOX board, which it was.

So I bought it.

Once I had it here (and recapped) I made a truth chart for the standard 40 channels and figured out my post about manipulating pin 9 earlier in the thread was wrong.

What needs to be done to put this radio on 26.815 MHz, and I have verified this experimentally now, is to reverse the voltages on pins 10 and 11 and set the radio to channel 2. Normal channel 2 (26.975 MHz) pin 10 will high (5 volts) and pin 11 will be low (0 Volts). Switch that so that pin 10 is low (0 Volts) and pin 11 is high (5 Volts) and it will be on 26.815 MHz.

Now I'm going to reverse the mods I've done on this thing and get it buttoned up.
 
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TM86 said:
I know the OP gave up on this one. But I saw the comment about this radio being "NOT able to be converted." It's a PLL02a chassis, there's got to be a way.

I found one on fleaBay and checked to make sure it was the same PTBM036AOX board, which it was.

So I bought it.

Once I had it here (and recapped) I made a truth chart for the standard 40 channels and figured out my post about manipulating pin 9 earlier in the thread was wrong.

What needs to be done to put this radio on 26.815 MHz, and I have verified this experimentally now, is to reverse the voltages on pins 10 and 11 and set the radio to channel 2. Normal channel 2 (26.975 MHz) pin 10 will high (5 volts) and pin 11 will be low (0 Volts). Switch that so that pin 10 is low (0 Volts) and pin 11 is high (5 Volts) and it will be on 26.815 MHz.

Now I'm going to reverse the mods I've done on this thing and get it buttoned up.
Click to expand...
You got the same result as I did in post #20. Only difference is I chose to change channel 15 (011110001 to 011010001) instead of channel 2 (011100001 to 011010001) because it only required one switch.
 
brandon7861 said:
You got the same result as I did in post #20. Only difference is I chose to change channel 15 (011110001 to 011010001) instead of channel 2 (011100001 to 011010001) because it only required one switch.
Click to expand...
What can I say? I'm lazy and stopped looking once I found something that worked.
 
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