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Old 16th May 2019, 5:13 am   #11
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Short Wave listening

Quote:
Originally Posted by davew View Post
Also, I fancy building a simple superhet, preferably valve - Any suggestions please?
It is hard to go wrong building a valve based single conversion superhet. You could go with a common type of design using a 6A8 converter and 6k7 IF and a twin gang capacitor. Philco made a real beauty that covered 5.7 MHz to 18.2 as I recall in one band and the tracking errors not too extreme (look up the schematic for model 38-7).

Or, you could go down the other road like the Eddystone 640 use an RF stage like an EF39 or 6k7, converter like a 6k8 or ech35 and another 6k7 IF and go for a 3 gang variable capacitor and divide the shortwave band in two or three segments for very low tracking errors.

A lot of noise on the SW bands can be ignored by using a ferrite rod, but depending on the particular rod, over about 12MHz they lose this utility.

This home made radio goes from 5.7MHZ to 18.2MHz and uses a rod:

http://www.worldphaco.com/uploads/TH...OC16_RADIO.pdf.

(also being 12V valves you cannot zap yourself )
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