"Faraday Telescope"
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| Oct 21st 2019, 18:10 | |
wd6ejnTotal Topics: 0 Total Posts: 0 |
Almost two decades ago I started fashioning long loop yagis with information I got (see my other post re wi fi loop yagi) on the internet (loop quad or loop yagi calculator)as a unwilling abused neighbor I spent most of these years devising stealth antennas to hide outside. Even a thirty gage wire can arouse suspicion in many busy bodies, and I'm not just talking about hoa's if you rent in one of these stalig 13s you can have an all out battle as "you have no rights" to join in any activities as home owners do. So I decided to avoid the "inconvenient bands" (hf) and build indoor antennas to beam out skylights or on a balcony no luxury of an attic in an apartment. My latest experiment is a 20 foot long 70 centimeter loop yagi having just over 20 (approx 12" spacing or less) directors as I have exactly 20 feet from sliding door balcony to front door. I decided to use a very small gage wire of 30 gage memory wire wich is silver plated so that I can use an extremely high gain tunable (432-435 mhz) radio telescope (hopefully under 100$) preamp with cor relay less then 10 watts for weak signal work. I'm really not interested in traditional dx contacts and hope to have a following of local hams interested in cw. It looks as if the 30 gage driven element will be spaced extremely close to the 1st and second directors and reflector as the influence on them seems almost nonexistant, I don't know how this will effect gain. As sites such as ssb electronics and Down East Microwave also Ramsey Electronics have disapeard, I am having hard time Google searching for a preamp to compensate for the db loss from the faraday cage of a tiny apartment, I'm talking about 100 db gain and < 1 noise figure. I had no luck at all with the silver plated "memory wire" Itossed it in with the 1-800-junk stuff! So, since the 20 + directors and reflector loop are 1/4" wide and 9-10" diameter, I decided to make the the driven element the same and copper to solder to I wonder how much difference it would make if the driven element was sterling (no I'm not going to swipe car exausts or antique stores) silver less then 1/4" wide . It appears that when I was tuning the memory wire I must have forgot to solder the ends of the open end of the loop back, making the resonent frequency go away together, now I have 1.1-1 from 432 to 435 mhz, emulating the mfj swr anylizer for a high radio telescope preamp which I have not found yet, all I have is an old Radio sShack scanner which is useless and all I hear is a lot of noise (probably 40-50 noise level and nothig else let alone anything on 70 cm sub band. I was forced to move some distance from here and was able to place less then half the loops (10 or so?) and tried to have 432-449 mhz. the signals from repeaters are so strong this did not work so I am going to look up repeater input frequencies and 432 MHz weak signals. When I had the 20 foot loop yagi inside the apartment I used the 100 uwatt? signal as a sort of beacon,, to my surprise I actually heard the signal from the mfj antenna anylizer about a quarter of a mile away actually threading through buildings and alleys! I was up about 20 feet on the second floor. The rules re motif pronounced motif! are more strict re indoors so I had to put the yagi on a balcony, I also use a stearling silver wire (22 ga) and it tunes great but still can't hear anything. I'm thinking now of just making a corner reflector and using the stirling silver loop, the turning radius will be limited but it seems that a corner reflector should work a lot better. I have searched endlessly for something a lot smaller (probably 8 feet on each side and 90 degree angle with no luck, everything is the same.....a lot of real estate or nothing. So, now that the yagi boom has been reduced to 8 feet (I hide it under the edge of the upper balcony eave, (I am using the same 2" diameter pvc mast for my 95 year old mother's hdtv antenna, so when I want to try to hear a 70cm signal from a handie talkie on the input of a repeater, the hdtv signal usually goes away! I tell her its just the weather) I am going to see if I can find a roll of pure silver or gold for the loop elements as I figure I can always recycle what's left I have been using aluminum foil cut with a paper circle cutter and the aluminum does not seem to work with anything less then 20 feet as the indoor antenna, although there was that cool happening with the uwatt signal going almost 1-4 mile. |
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