Yesterday, Joel KB6QVI, tipped me off to a new source for ceramic resonators that look as if they should be a godsend for anyone building a simple QRP rig for the phone portion of 40M (such as VK3YE’s Beach 40) – that’s if they perform according to specifications. A while back, we both bought some Murata resonators with a specified frequency of 7.2MHz, only to find that the very highest frequency they would oscillate at was 7.15MHz. Cecil K5NWA runs an online parts site called The Parts Place, and is listing a 7.28MHz resonator. The description says,
“Tunes over a wide frequency range. With 100 pf capacitor a shift of 7036KHz – 7284KHz is expected – will verify when parts arrive, do not use the center pin.
Note that for a lower top frequency, put a fixed small polystyrene capacitor in parallel with the adjustable capacitor, which can be made smaller.”
Joel and I ordered 20 each, and Patrick W9PDS said that he was going to purchase some as well. When Joel first found them, there were 167 available – there are now 127* as I write this. They are 30 cents apiece, 22 cents if you buy 10 or more, so it would seem worth picking up a few for the parts bin, as resonators that are usable in the upper portion of 40m don’t come along too often. The last time we found good ones was from hamshop.cz, and they have been out of stock for months now.
Please note that we haven’t yet received ours and don’t know whether they will resonate reliably within a usable range of frequencies but for home-brewers, this is worth a try while they’re available. If they are indeed usable, let’s hope that Cecil is able to get more in once the current lot is sold out. Incidentally, Cecil’s site is easy to use. I received e-mail status updates to verify that the order had been received, then another one to verify that payment had been received, and another one to notify that the order had been approved – all in short order. I assume that there will be another when the order has shipped. With a business like this, being run by an individual ham, this level of notification already surpasses what I would expect.
My soldering iron hasn’t been seeing much action lately, but Joel is an inspiration at the workbench; I have lost track of the sheer number of projects he has put together since I have known him. Doubtless he will verify that these are usable for ham applications once his arrive and I’ll post the results here once that happens. If I happen to put one of mine into a test circuit, I’ll let you know what happens with that too
Here’s the link once again (opens in a new window), and thank you to Joel for bringing this to our attention.
*As of 16:25 UTC (8:25am PST), there are now just 88 available.
NOTE – Steve G1KQKH, in the comments below, noted that this same resonator is available from Mouser. Check the comments section for his link to UK Mouser. If you’re in the US, the link is here (opens in a new window).