Circuit Diagrams in "The Screwdrivers Experst Guide"

Post by **3pinplug** » 13 Feb 2022, 13:27

I am assuming the extra capacitance is whats needed, i put out 4 watts and am bang on frequency but when i get to ch23 (Hi band - new band added) the tx power has gone from 4 watts to 1/2watt and 27.635 is all i can get to - any ideas?

Post by **3pinplug** » 13 Feb 2022, 16:25

Hi All

With the weekend fading fast I took a punt and put an 82pf cap in parallel with C212(47p) shown above and good news is i have:/-

Mids: 26.965 - 27.405
Hi's: 27.415 - 27.855
All channel frequencies are good now.

However, I know need to work out how to get the radio to cover all the channels withRF output, as I have full 4 watts on the all the mids but still only 4 watts up to ch23 where it drops off and practically 0.1watts on ch40- of the Hi's.

Is there a tip for broadnading the power as well with this type of mod?

Thanks.

Post by **cb4ever104** » 13 Feb 2022, 20:23

It's not the same as the VCO . There's a lot more involved in the output stage . From the mixers , all the way through to the antenna . I've never seen that radio , but you might not get the full 80ch range on TX . Or RX for that matter . Sue posted a thread about the 2824 chassis and she used the VCO voltage to track/adjust both the TX and RX stages to broadband it , but it's a lot of work . You might be able to bridge a coil at the mixer stage to dampen it a bit , but it's just a guess . If you have a scope then you should be able to see which stage is dropping off .

Post by **3pinplug** » 13 Feb 2022, 21:50

Hi Sammy
Its got the TC9102p PLL in it and from what i read its fine for the 80 ch mod its just when u have me doing it that you run into problems! Haha! i will take your suggestions on the mixers etc and read up on those and see if i can glean anything i can try, many thanks for this much appreciated. .

Post by **3pinplug** » 14 Feb 2022, 15:13

Done!!! Working across all 80 channels it just needed a tweak on the tx pots!
My first addition of extra channels and it worked, i am amazed!!
In the words of that great philosopher “Alan Partridge”... Back of the Net!

Post by **cb4ever104** » 14 Feb 2022, 16:33

Glad you got it sorted . I thought you'd already tried realigning the output stage , but it looks as if that wasn't the case . Anyway . Well done !

Post by **3pinplug** » 15 Feb 2022, 15:41

Thanks for your help again!

Post by **dj56** » 31 Dec 2022, 22:21

No Oscillation frequency in the circuit you built nothing to inject.
What freq xtals are you using.
A 2n3904 transistor is what you need and the oscillator circuit for it to work.

Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"

Re: Circuit Diagrams in "The Screwdrivers Experst Guide"