On a related question, while querying Mouser and others to find these 50 pF N75 caps, I'm asked what is the wattage. This isn't on the caps or on the schematic. I have no clue where to find it.
Hi, It's for a transistor VFO run off 12V -- any value you buy will work since the voltage will not be that high, nor the power. Have fun cap hunting, Mark.
The VFO inductor in this kit apparently with heating, drifts in value a lot in the positive directionl So he's following a correction plan someone came up with that employs some negative coefficient caps...
Understood. But, IMHO, it would be better to build the thing first, and then, if the drift seems excessive, to seek out the fix.
N75 : ±60 ppm/°C max. capacitance change from +25°C reading over temp. range of -25°C to +85°C == Craigslist, eBay. ... these are 25 pF https://www.dubuque-forsale.com/OLD...25-pf-ceramic-disc-capacitors-N75-5-qty-5.php OR contact SP International in Burnaby, B.C. (majority of their products are SMT parts) http://s-pintl.com/wp-content/uploads/2017-Capacitor-Catalogue-June-2017.pdf SP International 650 - 3711 North Fraser Way Burnaby, British Columbia, V5J 5J2 Phone - 604-324-4811 Fax - 604-324-3184 E-Mail - info@s-pintl.com Web - www.s-pintl.com
If anyone is still following this thread, I appreciate all of your "pre-flight" advice on the HW99. It's moving along. I checked all the resistor values (replaced a few) and got new electrolytic caps to replace these 30+ yr caps in the kit. The boards are all assembled, and now I'm running the initial multimeter tests and hitting some sour notes. It's hard to know where the culprit(s) could be, as the parts are so old. My soldering is pretty good, no bridges or cold solder joints. I'm posting these queries in the technical forum "Radio Circuits, Repair & Performance" if anyone wants to come visit. Thanks again for all of your invaluable suggestions.
I built one circa '85; still works, but disappointing vfo. Drifts a bit when turned on as to be expected; doesn't return to the original starting point when off. The accumulated error is about 22 Khz. Artifact from my youth; wouldn't part with it. One day soon I'll do a couple of contacts with it for old time's sake.
