| Electronics > Beginners |
| Air gap variable capacitors - buy cheap? |
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| aneevuser:
--- Quote from: CJay on March 22, 2019, 12:48:41 pm --- Why specifically does it have to be air variable and not a polyvaricon? --- End quote --- I've got a couple of those and as mentioned up-thread, I'm not getting great results, so I want to try something different. Anyway, I've already ordered one of the air caps, so I'll have something to compare them to, at some point. --- Quote ---When you say 'tuning' is it for transmitting or receiving? --- End quote --- receiving |
| james_s:
--- Quote from: soldar on March 22, 2019, 04:24:21 pm ---Dismantling an old radio set just for the variable capacitor is bordering on criminally stupid because the old radio is worth a lot more if it is not missing parts. A lot of those components suffered from microphonism, not only variable capacitors but also vacuum tubes. Many were improved over the years to reduce the effect. Variable caps had thick plates so they would not vibrate. --- End quote --- Certainly if it's a true vintage radio I would agree. There are lots of cheap junky radios from the 80s and 90s that are not worth anything, but I wouldn't get one just for the capacitor unless I already had one laying around. |
| rhb:
A late 70's table radio has a lot of useful parts. And a sharp eye will get you more than you have room to store as they get thrown away. Thrift stores test donations and stuff that doesn't work gets pitched. The $20 LCR/transistor testers make them even more valuable as a parts source than when I was 20 something. |
| CatalinaWOW:
--- Quote from: rhb on March 22, 2019, 06:50:23 pm ---A late 70's table radio has a lot of useful parts. And a sharp eye will get you more than you have room to store as they get thrown away. Thrift stores test donations and stuff that doesn't work gets pitched. The $20 LCR/transistor testers make them even more valuable as a parts source than when I was 20 something. --- End quote --- But if looking for the air variable cap you need to go a few years earlier. The air caps started disappearing at the end of the 60s. The more compact plastic separated ones lasted a few years longer, but by the late 70s I think varactors had completely taken over. |
| james_s:
--- Quote from: rhb on March 22, 2019, 06:50:23 pm ---A late 70's table radio has a lot of useful parts. And a sharp eye will get you more than you have room to store as they get thrown away. Thrift stores test donations and stuff that doesn't work gets pitched. The $20 LCR/transistor testers make them even more valuable as a parts source than when I was 20 something. --- End quote --- The fact that they pitch anything that doesn't work has always bothered me. The non-working stuff is what I would be most interested in purchasing so long as it is priced accordingly. Quite a lot of stuff has simple faults that are an easy one afternoon project. |
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