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Old 13th Feb 2018, 11:19 pm   #24
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Join Date: Jun 2006
Location: Chard, south Somerset, UK.
Posts: 6,188
Arrow Re: My first frame aerial

Originally Posted by bikerhifinut View Post
Could one of these loops be mounted away from the radio, say on the roof of my shed/summer house and a feed led in to the radio a few yards away?
And would the tuning/matching capacitor be ok mounted by the receiver?
Two good Qs. I don't have the experience nor in-depth knowledge to be totally prescriptive about all that, but a moments consideration of 'the basics' indicates the following . . .

With the assumption that a frame aerial has a coupling winding, where the tuning cap. is wired across the main winding, you will have a feeder from that coupling loop to the radio. Since the main winding is a balanced-to-ground affair, (it's important to preserve that) you need a balanced transmission line to connect from the coupling winding to the radio, which will need a balanced aerial input. (Failing that a balun will be needed *). That line will be low-Z, so the tuning cap. must be across the main loop (which will be high-Z) - thus remote from the radio.
As for it being outside, obvious considerations apply. Site it away from earthed objects - especially metallic things - and ensure that the loop - wire, woodwork and tuning cap. - are well protected from harsh weather, incl. strong winds.

* Once, I owned an Eddystone 730/4 comms. radio. That did not have provision for a balanced aerial. However, I was able to re-engineer it so that the coupling windings on the aerial input cols had each earth end lifted up from ground and taken to a separate terminal, thus providing a balanced input. OTOH, the Eddystone 888A which I also owned already had provision for a balanced aerial.
The point is this: if your intended set doesn't have a balanced aerial input, before getting involved with baluns and such like, see if you can modify the proposed radio. A domestic set should be much easier to modify than a six-range comms. radio like the 730/4.

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