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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Sat 25, 2014 10:43 pm 
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davep wrote:

Fifties, log em over on lispo id like to see your stations 8)
You might try dropping various small caps between the diode and the amp to ground .

Lispo? Link please. Several of the stations at the upper end of the band are foreign language, and not just Spanish, so dunno if I'd be able to ID them.

Re dropping small caps, you mean like .1/.01 discs? Between Diode Cathode and ground? What effect would they have?

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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Sat 25, 2014 11:10 pm 
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Hey fifties, you may now be bitten by the crystal radio DX bug! Sounds like your setup is working great. That's a hard one to shake.

Info, like Dave says, yes indeed. With a bit of playing around you might get some unexpected results. Once while using my loop with a transistor radio I hit a magic combination where the physical arrangement became uni-directional over at least part of the band. Cancellation, I guess.

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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Sun 26, 2014 12:29 am 
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Here 50s viewtopic.php?f=2&t=207609&start=640


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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Thu 23, 2020 7:20 am 
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This looks likes good topic to be reviewed again. That loop antenna seems like it can be made with not a lot of work You seem to make it look easy. Any tunable cap will work ??? Tom


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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Thu 23, 2020 7:29 am 
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Hey Tom,
I used one from a junked AA5. Using my bridge, it measured 405 pF, but I would imagine any metal air variable from an AM radio should work just fine. All you need to use on it is one of the gangs, whichever works better.

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 Post subject: Re: AM LOOP Antenna
PostPosted: Jan Fri 24, 2020 6:47 am 
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I have a lot of the condensers in the junk pile. to try. I have several from some small radios I can give a try first. Thanks for the information. I need to get the hoops but that should not be a problem. Tom


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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Mon 02, 2020 2:19 am 
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If you run a grounded wire along one side of the loop it will increase the directional DX off the opposite side.
Adjusting the distance from house bathroom or kitchen copper plumbing will effect signal strength.
One loop diameter above the house floor or table minimum. One loop diameter away from any metal objects like ham gear or file cabinets also.
Mapping the antenna receiving pattern is a good idea to avoid locations in the house that might drastically effect the antenna reception in one direction.


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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Sun 22, 2020 5:24 am 
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I tried my radios with three configurations one was a single loop, a two loop side by side, and the Australian finer tuned loop. The results were that the double loop was not much better than the single loop and the smaller white Australian antenna was an improvement over the select a tenna. I get a feeling a taller loop like Fifties would be much better. I use these in three different locations in my house but because of the different RF interference get somewhat different results. Tom


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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Sun 22, 2020 8:40 am 
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The loop in the first picture would indeed be better, simply because it's bigger. I too have found that using two tunable loops makes no improvement in gain or QRM rejection.

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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Sun 22, 2020 11:14 am 
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fifties wrote:
The loop in the first picture would indeed be better, simply because it's bigger. I too have found that using two tunable loops makes no improvement in gain or QRM rejection.

Yabbut...you talked earlier about bringing a second loop close to an AA5 (with built-in loop), and seeing a performance improvement.

With 2 antennas (of any type), I would assume that it depends on how they are connected. Suppose, for example, I have 2 identical loops and i want to try them in series. Since L in series adds, I now need to cut C in half to get the same tuning range. OR---each one needs the right C to resonate it, and then the 2 parallel combos wired in series.

For extra credit: If you have 2 identical parallel L-C circuits and put them in parallel, what happens? (I might know the answer in one coffee....)

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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Sun 22, 2020 7:05 pm 
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Something to keep in mind when building those old fashioned style loop antennas with radial windings: The turns close to the center of the frame have the least effect on total inductance, so it's not the most efficient use of the wire. You're better off keeping the radial depth of the winding to no more than about 1/5 of the loop's radius. There's also no benefit to spacing the turns more than about 1/4" apart. It just reduces inductance and requires more turns and more wire to get it back up to where it needs to be.


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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Sun 22, 2020 11:49 pm 
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pixellany wrote:
fifties wrote:
The loop in the first picture would indeed be better, simply because it's bigger. I too have found that using two tunable loops makes no improvement in gain or QRM rejection.

Yabbut...you talked earlier about bringing a second loop close to an AA5 (with built-in loop), and seeing a performance improvement.

Oy va Pix, you're killin' me! :wink:

How many loop antennas do you think are in his second two pictures? Maybe three? Hint; the radio has one, and he then placed two more next to it.

The second loop I had previously mentioned was the tunable loop, the first being in the radio itself.

I think I'll get a Tequila and OJ; my little brain is hurting...

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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Mon 23, 2020 8:57 am 
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I apologize for causing you stress---you are the loop oracle, and I am just a beginner...
Approaching the magic 5PM in So Cal, I do see the benefit of a libation, but Tequila and Orange Juice??---why does that remind me of Rum and Coke?

Enjoy your drink, but don't let it get you "loopy".......

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 Post subject: Re: AM LOOP Antenna
PostPosted: Mar Mon 23, 2020 9:38 pm 
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My experiments with two vintage loops similar to the ones shown did not give me a improvement but coupling one to 30 and 50 ft random wires across and around the room thru a BCB ferrite antenna coupled to gnd did give me good signal response in a crystal radio circuit.
Spacing of wires in a solid or stranded wire loop is critical. It varies with diameter. And on smaller wire Litz loops. Spacing using 660/46 Litz does not seem to be as important.


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