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Thread: 75/80 meter indoor loop antenna

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    SK Member 04/29/2020 w2amr's Avatar
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    75/80 meter indoor loop antenna

    I built this little gem a few years ago with parts I had laying around. The performance is surprisingly good as is , but when I use it with my old AMECO PT-2 preamplifier, it really comes to life. I used gator clips for the coil wires, because I planned to build coils for other bands .
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    Orca Whisperer PA5COR's Avatar
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    Reminds me on my project that was used to transmit, Varco started to spark above 25 watts though, used coax cable as Varco that went good to 100 watts shifting the outer braid making it cover the innard wire more or less.
    Might have used RG213 for that but I had enough Rg58 in supply ...
    Nice work, quick and dirty ;)
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    SK Member 04/29/2020 w2amr's Avatar
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    If you wanted to attenuate your signal, this would be a good transmitting antenna.

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    'Grumpy old bastid' kb2vxa's Avatar
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    Nice job but for one thing, it's too close to the wall to be rotatable. That comes in handy for squashing QRM considering the figure 8 pattern has deep nulls off the edges of the loop. An interesting coincidence, I have the same preamp. Oh, I like those old radios, my very first was an All American 5 in a Bakelite case. My discovery of stations between stations at night started me on the road to SWLing and eventually Amateur Radio.
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    SK Member 04/29/2020 w2amr's Avatar
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    Actually it's about 17" away from the wall, so it can be easily rotated. The nulls are very noticeable. In addition, the tuning is pretty sharp . So other than the frequency it's tuned to, the entire band is attenuated. I like using the old AM BC radios. It's a shame there isn't much to hear anymore.

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    SK Member 05/26/2022 WX7P's Avatar
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    Quote Originally Posted by w2amr View Post
    Actually it's about 17" away from the wall, so it can be easily rotated. The nulls are very noticeable. In addition, the tuning is pretty sharp . So other than the frequency it's tuned to, the entire band is attenuated. I like using the old AM BC radios. It's a shame there isn't much to hear anymore.
    No kidding. With all the syndicated shows on at night, BCB dx'ing is really not much fun anymore. I loved the clear channel days...
    http://i138.photobucket.com/albums/q275/nx6d/ham%20radio/SANY1260.jpg

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    Administrator N8YX's Avatar
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    I did something similar at an apartment. Several turns of wire around the top of the bedroom and a pair of loops at quadrature to each other with maybe two more turns apiece than the ceiling loop. Feed was by balanced line to a tuner and I could select each loop from the tuner's antenna switch.

    This thing worked surprisingly well at digging out utes across the HF spectrum and Europirates in the 49M band. I may put up another of these - maybe steerable and remotely tunable - for LF and MF work.
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

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    'Grumpy old bastid' kb2vxa's Avatar
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    Funny how pictures CAN lie, like those stupid side mirrors on vehicles these days "objects appear closer than they are". Once upon a time I had SO much fun parking a van I could just scream!

    "With all the syndicated shows on at night, BCB dx'ing is really not much fun anymore."
    Good old cookie cutter radio and just to make things interesting the FCC dropped the full ID with callsign every 30 minutes requirement. Now we hear the same satellite driven robot crap out of Houston in every major market and they all use the same logos so there's no clue what station you're hearing.

    "I loved the clear channel days."
    You must mean 50KW flamethrowers with no other stations on the frequency, Clear Channel is anything BUT a clear channel. (;->)
    Rant mode off AR/EX //

    Back to receiving loops, they're great for everything I said they are. I remember inheriting a Hallicrafters SX-122 seen here in mint condition and some home brew stuff from an avid AM BCB DXer when he went to the big monitoring station in the sky. The most useful thing he made was a spider web loop. Looking at that schematic above I recognized it immediately as the same configuration only mine had bigger coils and more paralleled sections of 365mmF (no pF in those days) variable caps not shown here.
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    Whacker Knot WØTKX's Avatar
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  10. #10
    La Rata Del Desierto K7SGJ's Avatar
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    Quote Originally Posted by kb2vxa View Post
    Funny how pictures CAN lie, like those stupid side mirrors on vehicles these days "objects appear closer than they are". Once upon a time I had SO much fun parking a van I could just scream!

    "With all the syndicated shows on at night, BCB dx'ing is really not much fun anymore."
    Good old cookie cutter radio and just to make things interesting the FCC dropped the full ID with callsign every 30 minutes requirement. Now we hear the same satellite driven robot crap out of Houston in every major market and they all use the same logos so there's no clue what station you're hearing.

    "I loved the clear channel days."
    You must mean 50KW flamethrowers with no other stations on the frequency, Clear Channel is anything BUT a clear channel. (;->)
    Rant mode off AR/EX //

    Back to receiving loops, they're great for everything I said they are. I remember inheriting a Hallicrafters SX-122 seen here in mint condition and some home brew stuff from an avid AM BCB DXer when he went to the big monitoring station in the sky. The most useful thing he made was a spider web loop. Looking at that schematic above I recognized it immediately as the same configuration only mine had bigger coils and more paralleled sections of 365mmF (no pF in those days) variable caps not shown here.
    Huh, I remember it as uuf, or mickey mic. Must be an Arizona thing.


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