Yes i think its my design
Please post a picture and i can help you

RF-Head wrote: ↑Tue Jan 31, 2017 5:48 pm Yes i think its my design
Please post a picture and i can help you

Ok, here are the two photos:

I have been testing it and it gives 50mW at 13V, off course without FET at final.

Frequency is set by dip-switches on MC145151P2.

Output part of the board is been messed a bit but it can be repaired. Since I don't know what exact FET is been used in original configuration I am thinking about placing RD06HVF in the circuit. Feedtrough cap is broken, probably RF choke, like VK200 have been removed just after feedtrough capacitor. Resistor 1R0 was placed in power rail and it was burned and BIAS trimmer is completely pulled out from the board.

Capacitor on base/gate of buffer transistor has been soldered or changed definitely, as can be seen on the photo.

That is all that I can see on this short inspection. If You see something else please tell. Thanks.

Yes this is my old design
The output transistor is a BLF242 and the transmitter runs on 24V
If you can't find a BLF242 then i can look for you

@RF- Head

Nice one.
I will contact my friend about this. I think he ordered RD devices so we will probably avoid the option of putting back original BLF242.
Main reason is 12 vs 24 V power supply and much lower price of the RD06HVF comparing to the BLF242.

Can you please tell me what were the rest of the components, that are missing on the board right now? You probably had VK200 or ordinary 1uH choke to the power supply to the OP-AMP 723?

Also another thing. On the first picture you can see there is one empty place for some component, after the buffer stage toward the output FET, just below the coil with 4 turns.

Transmitter works without it anyway so maybe its not in use?

It's a real long shot that the RD06 will work in place of a BLF242. The output impedance to match the BLF properly will be a lot higher, plus the packages have totally different mounting so it will be a challenge tomget the RD to fit.

Personally, I would buy the original transistor so that the circuit works as the designer intended. Enigma shop have the BLF for £16 so they're not that hard to find.

@Analyzer

Hi. thanks for joining the party.

Well, correct me if I am wrong, but changing/modifying the output matching network of this transmitter should not be problem IMHO. There is enough place for that.
I planed to mount RD06HVF1 on edge of the case, where proper heat sink can be mounted. In the original design BLF242 was placed below PCB, probably due to the available heat sink or maybe it was placed of one big heat sink, where another bigger amplifier was mounted, so exciter and amplifier were on same heat-sink. Just guessing.

Dont forget reason that I mentioned in previous post. 12 V vs 24V power supply! My friend dont have 24V and dont know much about this (or dont want to bother with it). He has 13.8 V supply and already purchased RD06HVF as I know.

Radio Garfield wrote: ↑Wed Feb 01, 2017 11:45 am @Analyzer

Hi. thanks for joining the party.

Well, correct me if I am wrong, but changing/modifying the output matching network of this transmitter should not be problem IMHO. There is enough place for that.
I planed to mount RD06HVF1 on edge of the case, where proper heat sink can be mounted. In the original design BLF242 was placed below PCB, probably due to the available heat sink or maybe it was placed of one big heat sink, where another bigger amplifier was mounted, so exciter and amplifier were on same heat-sink. Just guessing.

Dont forget reason that I mentioned in previous post. 12 V vs 24V power supply! My friend dont have 24V and dont know much about this (or dont want to bother with it). He has 13.8 V supply and already purchased RD06HVF as I know.

Of course, you're right you can modify the output matching to make it work.

Another thing to consider might be that the PLL won't lock over the whole band with only a 12/ 13.8V supply. Now, I've never had one of these in front of me so I can't tell for certain. I'm sure RFHead will reply with that info.

Let us know how you get on!

@Analyser

When I tested it on 13V it worked OK on various frequencies. I did not knew positions of dip-switches of 88 and 108, so I just tried various random positions of dips and was reading it on f-counter. PLL worked fine on every place I was.
I will let You know about detailed testing.

Thanks. Hear you agn...