NP0 caps become much more important when going cold... not such an issue for ham electronics which will likely never see temps below 0C
Matt
W8ESE
sent from my VIC-20
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On Thu, Jun 17, 2010 at 12:33 PM, hanssummers2000
<hans.summers@...> wrote:
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Hi Steve et al
> Greetings from sunny England,
Speak for your own part of England! Here in London, the sun has disappeared behind some thick clouds.
> Those of you who have built the beacon kits will have noticed that we do not use NP0 caps. In fact I cannot remember the last time I used them. Yet these beacons are very, very stable in output frequency as are my other projects. Which makes me wonder if modern caps are much less temperature sensitive than they were in times of yore and question why people still use them.
>
> What do you guys think?
Personally I think NPO caps might be useful sometimes, but generally are over-rated. There are a lot of other temperature-sensitive parts involved in an oscillator, including of course, the crystal itself.
In past QRSS work, I have used the DB6NT crystal heater, see . I found that it completely removed any observable drift, even though I didn't trouble with NPO capacitors. So I believe that, in the case of crystal oscillators for QRSS, the main freuqency-drift-determining component is the crystal itself. The DB6NT crystal heater is very nice. It typically goes on an HC49 crystal, whereas the crystal in the QRSS Beacon kit is a 1/4 height crystal. So I'm not sure how well it would work, or maybe need adaption. Beware too, that it will cost you somewhat more than the QRSS beacon kit cost you!
73 Hans G0UPL
