SUPER RARE NRG GEM

[sinus trouble]

Hello Necks!
I was VERY lucky to be given this VERY rare piece of NRG kit which i believe was never released by Mr Moss!
There is no schematics or info available at all! However it was featured in the NRG workshop (PA only) to give a guide to amplifier construction!
As can be seen it is a VFO and should acheive around 12Watt with a BLY89 device!
Im still in the process of building and testing? but will keep updates comming!

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[teckniqs]

Did you get it working?

[sinus trouble]

Yeah Man! the tuning is a bit out? lol covering 92.2mhz to 120mhz putting out a watt so far but needs a lot of tweaking

[teckniqs]

That's not bad though considering it was never properly built and sold. Probably just slightly change a cap and it should go down.

[pjeva]

Sinus, just compress the coils in oscillator a bit. Don't add capacitor until you try that. Added capacitor could shrink your tuning range to just a few MHz...


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[sinus trouble]

Cheers Teck and Pjeva!
Yeah its real close, i was expecting alot worse than that!
Started work on the PA now, that may have an effect on overall tuning as it wasnt complete?
Ill post some more pics soon!

[MiXiN]

Very nice...

Wish Mr Moss was still doing all this. RIP.

I had a similar tuning range problem with a Pro 3, and adjusting the coils as Pjeva said did the trick.

By the way, where did you get it from?

[pjeva]

First stage after the oscillator should decouple oscillator from the "rest of the world", so output amplifier should not affect tuning.


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[Analyser]

Cheers Teck and Pjeva!
Yeah its real close, i was expecting alot worse than that!
Started work on the PA now, that may have an effect on overall tuning as it wasnt complete?
Ill post some more pics soon!

I can see you've taken the output after the two trimmers and small coil for testing; you realise this is the match for the following transistor and not for 50 ohms? That match will take the output down to 1 or 2 ohms so you won't get much power out until you add the final.

[sinus trouble]

Nice 1 Mr Analyser!
I had a feeling that would be the case,but wasnt 100% sure? many thanks for confirming!

[sinus trouble]

Hello Again Necks
Ive built up the PA based on the BLY89 circuit, Unfortunately i did not have the correct transistor so i put in an old RF2120 to see what would happen?
As expected its not performing well
Its doing 6watt and gets very warm!!! also goes into some crazy oscillation when trimmers are set at a specific position!
Anyways a BLY89 and alot of work is still needed, but ive added some pics!

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[RF-Head]

Try to put a 27pf capacitor by the last 80pf trimmer on the output to ground and a 27pf capacitor on the output pad to ground (by the coax)
And 1 to 3 100pf capacitors to ground on the base of the output transistor
Realy nice to see some old NRG stuff

[Analyser]

RF Head is right, you need some capacitance before and after last coil on the output of the PA. Try hat before adding base capacitance.
It also looks like you could do with a hotter soldering iron.

[sinus trouble]

Most Grateful for all your knowledge and expertise!
Its a challenge for me working on something that Mr Moss created, mastered with little documentation on!
Ive noticed even L3 on the driver side (3 turn coil) improves gain when i add a ferrite slug!

[sinus trouble]

It also looks like you could do with a hotter soldering iron.

I only have a little one! I guess size matters!

[Shedbuilt]

Yes. Following on from what RF Head and Analyser said - which I agree with.
As you know, you have a tuned amplifier. The inductor coming out of the final, and the 2 trimmers, are the output match. This should match to 50 Ohms, and what follows should be an output filter (I say should be, because at the moment, it's trying to perform an unwanted impedance match). Going with the inductor which is already there, and the caps as suggested by RF Head, you'll have a single pi section (3 pole) low pass, but looks like you've got tracks there to add another couple of sections - with the inductors at right angles.

[sinus trouble]

Cheers Mr Shed!
I followed all yous advice and here is what ive got now!

Completed the output stage!

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Getting Just Under 12 Big Ones!!

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Running at 12V around 2A consumption!

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SWR aint too great? I believe that is due to my homemade dummy lol

[sinus trouble]

Although all seems well? its not suitable for broadcasting! im getting spurs either side of the carrier,so something is clearly not right!

[Shedbuilt]

Although all seems well? its not suitable for broadcasting! im getting spurs either side of the carrier,so something is clearly not right!

Is it clean with the driver board alone powered up ?

[sinus trouble]

Tbh Mr Shed, im gonna have go back through it all from scratch!
Its a strange design and doesnt operate quite like any other NRG ive tested before?
the oscillator section is conventional but then feeds into two bf199s paralleled which from experience is prone to thermal instability?
Its most likely that ive made a blunder in the PA section, but also makes me wonder why Mr Moss scrapped this layout??