The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Update:
The old expanded GE is up and running with hfr-20w very well .

G'day Sue, thanks very much for your offer although wont need to take you up on it as i now have some bb809 varicaps on their way :) . Thanks also for taking time again to set me straight,so to speak :) and explain in a way thats easy to understand. Next on the list will be getting the chassis to ha...

Thanks for the heads up Sue that the varactor capacitance value has no effect to the circuit apart from core slug position. I had a dig in my varactor parts and checking against datasheets found i have Toshiba 1SV149 varactors with low voltage operation and large capacitance ratio,perhaps i should h...

Thanks lbcomms,

I will heed your advice and set it up for 120 channels to 28.2 maximim leaving the cap values in vco as they are per diagram and leave the second varactor in to save removing from board again.

Unless,you recommend removing the second parallel varactor.

Cheers,
Craig

Well with a bit more playing around with vco,before i realised that my main problem lay in the 21mhz injection into the vco mixer,i'm not sure what to do there to increase the signal could only go so far with the adjustment with tuning coil T3 and signal is low, perhaps changing cap coupling values ...

Ok,was able to get from 26.965 to 28.695 after adjusting mixer coils before vco quit operating on transmit/receive at 28.705.It would transmit at 28.705 then when tx button released there would be no receive no tx until i came back down into low 27 mhz where vco became operational again and unit wou...

The vco with only the varactor BB910 added had lack of range/unable to tune,intermittent operation,it was about a week or so ago i tried it and that is what prompted me to post here in case the varactor i was using was not suitable and there was something else that needed doing such as addition/remo...

Hi lbcomms, As is usual i have found, you are a valuable source of information and technical expertise willing to share your knowledge and help those of us of a lesser education and experience. I searched for hours/days looking for a working mod for this vco with no joy. I already had the epoxy remo...

Hi all, I am looking at broadbanding a GE A3-5825A and do have a few new old stock Phillips BB910 varactors and am asking here if these would be suitable for the task of extending the range on the vco and if so,what range extension can i reasonably expect ?. Is there a better,wider capacitance range...

Thanks Sue,
No more questions on that one,you have answered/explained everything.

Cheers.

G'day Sue and thanks for the reply. Yes,it has had an 18 to 40 switch conversion. Wire removed and problem fixed :D What was the purpose of this wire connection originally when 18 ch switch fitted ? I see in a couple of schematics for the 48AOX boards this circuit feeds + dc to either pin 1 or pin 2...

Radio Make and Model: GE A3-5825A PCB Number: PTBMO58COX PLL Number: 02A Test gear available: Dmm,Frequency counters,Leader LSG-215A signal generator,Tektronix 2235 AN/USM 488 scope,audio/function generators,80 watt 50 ohm dummy load with rf "sniffer" port.etc Symptoms: When channel select...