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Looking for good hyperabrupt varactor

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Space Varmint

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I always liked the ECG612 but have trouble finding them. The data sheets I've looked at on various other varactor diodes just don't measure up. I believe NTE made an NTE612 as well.
 
Would this family work? Check out the ZC933
Listed @ digikey

**broken link removed**
 
Apparently varactors are VERY difficult to come by these days, there was a company (now sadly closed) called MCES who specialised in tuner module repairs, we used them for years. For a long time before they closed, they were having massive problems trying to source replacement varactors for repairing duff tuners.
 
Apparently varactors are VERY difficult to come by these days, there was a company (now sadly closed) called MCES who specialised in tuner module repairs, we used them for years. For a long time before they closed, they were having massive problems trying to source replacement varactors for repairing duff tuners.

Yeah I've noticed that too. Well you do know that all diodes are varactors usually to a much smaller degree. Whenever you apply a reverse bias across a diode junction, it causes the depletion layer to expand and contract. So one solution could be to experiment with different types of commonly available diodes like 1N914s and when you find something pretty descent you can parallel them since capacitors in parallel add. But surely you don't need 20 diodes on your PC board that all do one thing...lol. Now that would be pretty silly, wouldn't it?

I want to know what happened to the germanium diode? I heard the military still gets them.
 
Yeah I've noticed that too. Well you do know that all diodes are varactors usually to a much smaller degree.

A rectifier diode actually makes a pretty decent varactor, with a good wide range - but for UHF you really need specific varactors, particularly as they are supposed to track together.

I want to know what happened to the germanium diode? I heard the military still gets them.

They are still easily available, used for detectors as they have always been.

Much too leaky for varactor use though - and in fact the most common failure of varactors is leaking slightly.
 
A rectifier diode actually makes a pretty decent varactor, with a good wide range - but for UHF you really need specific varactors, particularly as they are supposed to track together.



They are still easily available, used for detectors as they have always been.

Much too leaky for varactor use though - and in fact the most common failure of varactors is leaking slightly.

No kidding? I have not been able to find germanium diodes. I wouldn't use them for varactors, I just like the low bias for various obvious reasons.

You may have just helped me. I did not know that rectifier diodes where good for that but as a matter of fact I want to take advantage of some theory I read about where DC2DC converters were used to get a wider voltage range from the phase detector in a PLL. Well with some of the voltage ratings I have seen of the varactors, I still would not be able to swing that voltage a great deal, and of course if I used them in series it would defeat the frequency deviation since the capacitances divide in series. Obviously a big juicy power rectifier can handle the reverse bias. Maybe a couple of those in parallel would do the trick.... Thanks Nigel
 
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