if you change the 10.24 inside already what happens is is skews the steps so the rx and tx wont track
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cobra 25 gtl (taiwan) full restoration
- Thread starter Uncle Ronnie 336
- Start date
so in this setup when the oscillator switches between the bands, does it just simply swamp out the extisting signal there? and by white and green wire.....since i dont have that reference on hand, the white is the oscillator output i'm assuming? what is the green?
Green refers to the signal coming from the main 10.240 oscillator, but in your case, you are generating a secondary 10.240, so no need. All other parts of this (JP15 and R69) remain, if using an "S" kit or clone.
I meant injecting a new 16.xx signal bypassing the pll completely. I don't know, sounded good at the time.
I was thinking of a varactor tuned vfo with some kinda temp compensation. Like 4.5 maz - 5.5. Then mix with 11 mhz crystal oscillator. Keep the 10.24 for rx and add new TX oscillator 10.695.
I would think the cheap $hit eBay freq counter would work because now only one frequency from the vfo is used on TX and rx.
Don't mind me really I just got done reading that pll book like for the 10th time. I've got some free time at work.
I would think the cheap $hit eBay freq counter would work because now only one frequency from the vfo is used on TX and rx.
Don't mind me really I just got done reading that pll book like for the 10th time. I've got some free time at work.
So here's the problem. The PLL has to provide two different frequencies for each channel. One for transmit and one for receive.
The difference between these two frequencies is always the same, so it gets generated from the only crystal in the radio, the 10.24 MHz.
That crystal's 10.240 MHz frequency gets divided by two ten times. This provides the 10 kHz frequency that sets the spacing between channels.
Just one problem. That only works for 10.24 MHz. Change the crystal and the channels will be farther apart if the new crystal's frequency is higher. And closer together than 10 kHz if the new crystal's frequency is lower.
The more crystals a PLL has, the easier it is to expand. And a PLL with only one crystal may be expandable, may not. Depends on the design of that model.
73
The difference between these two frequencies is always the same, so it gets generated from the only crystal in the radio, the 10.24 MHz.
That crystal's 10.240 MHz frequency gets divided by two ten times. This provides the 10 kHz frequency that sets the spacing between channels.
Just one problem. That only works for 10.24 MHz. Change the crystal and the channels will be farther apart if the new crystal's frequency is higher. And closer together than 10 kHz if the new crystal's frequency is lower.
The more crystals a PLL has, the easier it is to expand. And a PLL with only one crystal may be expandable, may not. Depends on the design of that model.
73
A long time ago, in a far, away place from here (Tampa), I used to work for NeoComm Electronics in Newton Falls, Ohio (Zipcode 44444).
A customer had a Cobra 1000GTL and a Glen 326-G VFO, and wanted me to install it to run the radio. I perf-boarded a 10.695 oscillator, because it was a one-off. I retrofit the CB/PA mode switch to where if the switch was set to CB, the uPD2816 PLL and internal VCO were "live", and when in PA mode, I depowered the Channel LED and PLL/VCO circuits, the Glen would then be active, and the 10.695 oscillator would also be powered in TX mode. I also broad-banded the RX and TX circuits using Lou Franklin's broad-banding info from the PLL Data book, which I had memorized the techniques from way earlier. I don't remember if I disabled the TX/RX line of the uPD2816, locking it in RX only, and let the 10.695 oscillator run in both modes, or disabled the external TX mix oscillator in CB (switch) mode, as that was 40 years ago, now.
The customer was very happy with the work.
A customer had a Cobra 1000GTL and a Glen 326-G VFO, and wanted me to install it to run the radio. I perf-boarded a 10.695 oscillator, because it was a one-off. I retrofit the CB/PA mode switch to where if the switch was set to CB, the uPD2816 PLL and internal VCO were "live", and when in PA mode, I depowered the Channel LED and PLL/VCO circuits, the Glen would then be active, and the 10.695 oscillator would also be powered in TX mode. I also broad-banded the RX and TX circuits using Lou Franklin's broad-banding info from the PLL Data book, which I had memorized the techniques from way earlier. I don't remember if I disabled the TX/RX line of the uPD2816, locking it in RX only, and let the 10.695 oscillator run in both modes, or disabled the external TX mix oscillator in CB (switch) mode, as that was 40 years ago, now.
The customer was very happy with the work.
Hi Nomadradio. The TX 10.695 makes up for the "split" requirement (at least until my mind anyway, lol). I mean feeding a 16.270 signal would be 26.965 (16.270 +10.695 = 26.965 on TX and 26.965 - 16.270 = 10.695 - 10.240 = 455) . I guess it means that one of those cheapie freq counters would work then because it's one frequency for both tx-rx.
So the counter IF would then just be set for 10.695 and I think it should be correct for both tx-rx.
Hi nz8n - nice work. (Any progress on the new 29 funnies)
So the counter IF would then just be set for 10.695 and I think it should be correct for both tx-rx.
Hi nz8n - nice work. (Any progress on the new 29 funnies)
For transmit. The PLL jumps down 455 kHz when you release the mike button. The display would have the correct offset for transmit only, not for receive.
73
took a pause and life got in the way....again. so last night i was fkin around with it. its too much drive for a single 9530 ekl FET and the PEP is enough to push the input swr up apparently annnnnnnnd i blew the HG final. idk why but it seems like HG 1969s are pretty delicate. i think somewhere i have a mitsubishi 1969 kickin around from a part-out so maybe i should drop the ol classic in.
so im back on it. threw another HG in, getting slightly less PEP. took the NPC mod out, for somereason things got hotter with that in reducting the carrier (weird) and it runs good with a 9w DK so i think im just gonna let it ride as a stout rig. maybe put it in front of 4xerf9530 mosfets which like a higher dk. got some unseasonably warm weather this weekend, so for future ratrod restos, i think the epoxy paint will come out, so i got some nice fresh painted cases to work with this winter. this radio looks both beat up and fresh at the same time. I didn't know that was even possible.
just tried this layout, for some reason im getting nothin from the rig now. thinkin i might be missing something....
WTF?
Only about twice or more what's safe for it. Reminds me of drag racers at the starting line. Now and again the nitrous gets away from them and explodes the air scoop 20 feet into the air.
Remember that a MOSFET like that throws more heat per Watt of carrier than a bipolar final. They're cheap, they can do more power than stock, and they fail spectacularly.
As a bonus, it draws more audio power from the modulator and speeds up the death of that side of the transmitter.
Doubling the raw power of that radio seems more costly on the whole that spending the same resources towards an amplifier. Even if you double the radio's power, nobody will know but the guy watching the wattmeter. S-meters at the other end won't be impressed. An amplifier, on the other hand, will make a difference they can see and hear.
Don't want to sound negative about people experimenting and learning from the experience. If that's the objective then go for it! And if bang for the buck is your desire, that would be different.
Hey, I've been following the story so far. It's your radio to experiment with, after all.
73
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