| Electronics > Beginners |
| Air gap variable capacitors - buy cheap? |
| << < (4/7) > >> |
| aneevuser:
--- Quote from: rhb on March 22, 2019, 12:18:29 am ---Visit a few thrift stores and buy an old radio. The older the better taking into account condition. --- End quote --- I can't think of anywhere local to me that would have something suitable - I don't live in a big city and the only "old radios" that I've seen were in antique shops at antique shop prices. Maybe it's easier to find such stuff in the States. Back in the day I would have gone to a charity shop for one, but these days in the UK they've gone upmarket and expensive. --- Quote ---And if you want top of the line air variables I have an unknown quantity of NOS 1940's vintage air variables at a wide range of voltage specifications made by Hammerlund and such. Send me a PM if interested. --- End quote --- Thanks but I suspect freight charges will make that unfeasible - anyway I have one on order, and am going to start playing around with the varactor approach too, so I'm good for now. |
| aneevuser:
--- Quote from: james_s on March 22, 2019, 12:22:48 am ---Why not just buy a cheap variable capacitor from eBay? They're not that hard to find yet and often not very expensive. --- End quote --- I already have one - it was quoted as having a max. capacitance of 125 pF, but I'm finding that a) it's more like 25 pF (maybe I was ripped off) b) I seem to get very poor Q at the limits of its range for some reason. So I want to try another type to see if I get better results - not yet sure how much my problems are due to my cluelessness or due to a dodgy cap. |
| rhb:
Are these too expensive? https://www.ebay.co.uk/itm/ALPS-Air-Variable-Capacitor-for-FM-AM-SW-Crystal-Radio-Antenna-Tuner-Ham-Radio/132962614313 https://www.ebay.co.uk/itm/ALPS-Variable-Capacitor-20pf-320pf-FM-AM-Crystal-Radio-Antenna-Tuner-Balun/132992365516 |
| CJay:
--- Quote from: aneevuser on March 19, 2019, 02:16:40 pm ---I'm looking for a variable capacitor suitable for tuning over the AM frequency band, and this: https://www.ebay.co.uk/itm/Single-Joint-Air-Dielectric-Variable-Capacitor-12PF-to-365pf-250M-35-29-26mm-/192610325869 at about 9 quid looks suitable. However, having looked around, I've seen similar caps priced at £80 quid or more, or similar in dollars. So I'm wondering what I'd actually be getting for the £9 price - cheap junk or something usable? Does anyone have any knowledge of these? --- End quote --- Why specifically does it have to be air variable and not a polyvaricon? When you say 'tuning' is it for transmitting or receiving? The cheap polyvaricon tuning caps are good for receive and, surprisingly, transmit too but only to a couple of watts, they're also considerably cheaper than the air spaced ones (£2 ish) |
| soldar:
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. |
| Navigation |
| Message Index |
| Next page |
| Previous page |