medium wave Pll with cd4060 / cd40103 /cd 4046

[Hamnchips]

Albert did you use that 2N3707 transistor in yours? The circuit definitely doesn’t work for me as printed, I’m getting noisy results across the whole band, and some FM too!

I’ve been over it many times, varied coupling capacitance from the C4053, tried pull down resistors, nothing really changes, the results are more or less the same.

Only other thing I can think to try is different inductors or another transistor. The inductors in using are small epoxy coated ones bought online, I wonder if they perform ok at these frequencies...

[Albert H]

That's weird! I'll have a look at what I lashed together on the end of my little MW thing. You have put it before the lowpass filter, haven't you? As I recall I used a 2N3707 because I have a box of them on my workbench - it's just a generic low power NPN silicon transistor!

[Hamnchips]

Yep definitely before the output filter - I tried a 2N3904 and same results.

I seem to be burning through those 2.2mH chokes as well, very hot to touch and after not long become low value resistors. The transistors and the emitter resistor are getting very hot too

[Hamnchips]

Perhaps the weedy little inductor is burning out very quick and then sending far too much current down the collector....

Ive ordered some chunkier units with higher current capacity and will report back if any different.

[Albert H]

OOPS! The collector choke I've got here is 22µH not 2.2

[Hamnchips]

Ah, does that mean both chokes are in uH and not Mh then also? Maybe I’m using wrong for both in that case.

So should the 2 inductors be 1mh and 22mh, or 1uh and 22uh in that case?

[Hamnchips]

I assume it has to be millihenry (mH), not microhenry (uH). Otherwise they seem too low a value to stop RF getting into the power supply....

We shall see

[Hamnchips]

Albert am I missing something with this choke?

With 1mh used at the base, and 22mh used at the collector, it works better in that the audio quality is clean, but the range is awful and the collector choke is getting a roasting. What type of inductor did you use exactly?

Looking at the specs of most 22mh inductors, their max srf is only say 200khz. Trying to find one to take moderate current and work at medium wave frequencies seems impossible. Did you make one yourself? Any suggestions would be great.

I assume the choke is not performing for 2 reasons:

1) its getting roasted to death

2) The best output I can get is when no inductors in the filter network are switched in, which tells me the signal is preferring to go up the power supply as the choke, so it must not be resisting the RF very well.

3) I've tested all other components and rechecked the layout several times. I've even tried other matching networks other than the onboard one, and it barely gets 1 or 2 feet out.

All the best,

Adam