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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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20th Aug 2014, 11:28 am | #1 |
Octode
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,326
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Frame Aerials
(Should this go to "General Vintage Radio" as it was originally about vintage radio aerials feeds, or is it "Homebrew" because it's partly DIY?)
For whoever wanted info on frame aerials: MWDX circle have more aerial info than you'd ever need here with loop info at the end. They also have loop info here with their MW source directory. More here from 'frame aerials' Google images. Tuned loops don't necessarily need any matching amp, but do need tuning! Un-tuned loops do need an amp. Construction isn't critical (but don't use a metal frame!) and the size for MF the classic design is about 40 inch sides, with 7 to 8 turns (depending on tuning cap) and one coupling turn to the feeder to the set. Very directional but not very portable! Ian |
20th Aug 2014, 3:18 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,970
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Re: Frame aerials
You can also use a ferrite rod and coil if you don't have room for a frame, either amplified or unamplified.
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20th Aug 2014, 3:47 pm | #3 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Frame aerials
Another useful design
http://www.radionz.co.nz/listen/amhelp |
21st Aug 2014, 12:13 am | #4 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
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Re: Frame Aerials
I have had some success with relatively small ones measuring about eight by six inches attached on standoffs to the back of the set. I made a wooden frame a bit like a picture frame with small dowels in the corners, and simply wound approx twenty turns on for MW, measured the inductance and added or removed turns till I obtained the right value to resonate with the tuning cap. I found that they perform at least as well as a ferrite and are less prone to interference, but of course you can't adjust the inductance easily like you can with a ferrite rod, and they are prone to proximity effects if you mount them too close to the metal chassis.
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21st Aug 2014, 7:39 am | #5 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,903
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Re: Frame Aerials
Ferrite rod coils tend to be fairly high Q and are resonated to get best sensitivity, which makes them narrowband, which is OK for one antenna per receiver but would limit the ability for the different sets in different rooms to be on different stations.
In a distribution system intended for general use, where the sets get moved around, I'd envisage a good broadband antenna with a distribution amp to a coax socket in each room. Then there would have to be a plugged in dummy antenna for sets with sockets, or a coupling loop like a mini frame antenna for sets with internal frames or ferrite rods. David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
29th Jan 2015, 1:28 pm | #6 |
Nonode
Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
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Re: Frame Aerials
One post concerning a replacement frame aerial for a specific radio moved here; https://www.vintage-radio.net/forum/...d.php?t=113480
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Brian |