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Author Topic: Magnetic loop antenna for 2 meter RECEIVE ONLY  (Read 171 times)

KK4GMU

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Magnetic loop antenna for 2 meter RECEIVE ONLY
« on: September 13, 2022, 05:07:49 AM »

Is anyone here aware of a "receive only" magnetic loop antenna for 2 meter/70 cm commercially available or from a knowledgeable "home brewer" who sells such a thing?

I'm wondering for "stealth" vs "performance" if it might be better than a vertical.  Again, only "receive only" for an SDR receiver.
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G4AON

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #1 on: September 13, 2022, 05:43:49 AM »


I don’t doubt there are various active VHF/UHF antennas that may work to some extent, but a dual band antenna can be made quite easily and can be discreetly mounted.

Towards the bottom of this web page, check out the “FBK 2/70 portable coax antenna”. It’s both east and cheap to make.
https://www.qsl.net/pa0fbk/hampage_uk.htm

There is the commercial dual band Slim Jim by N9TAX if you don’t want to strip a piece of coax…
https://n9taxlabs.com/shop/ols/products/dual-band-slim-jim-antenna-with-10-or-16-foot-cable

73 Dave
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W1VT

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #2 on: September 13, 2022, 06:24:52 AM »

Horizontal slots cut into a dish will work as vertical antennas.
https://w6nbc.com/articles/20xx-dishslot.pdf
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K5LXP

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #3 on: September 13, 2022, 07:28:37 AM »

"Better" in this context would be gain but in the case of VHF/UHF the type of antenna is mostly secondary to where it's located .  Even a crappy antenna up high beats just about anything else down low.  I've worked 80 miles out simplex on 2M with an HT and rubber duck, standing on Pike's Peak.  You can hear satellites running half a watt from 120 miles out in space.  Without line of sight though no amount of gain will make a difference. Figure location (height) first for line of sight, then after that the signal strength received becomes a link margin calculation based on gain and losses of your system.  For an apples-apples comparison between say a vertical and a "loop" it comes down to pattern vs gain (or loss), and a tradeoff of having one that's omnidirectional and one that isn't.

Mark K5LXP
Albuquerque, NM
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KK4GMU

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #4 on: September 13, 2022, 08:54:28 AM »

This one: 
https://www.amazon.com/dp/B09P8B6492/?coliid=I3EMV8CXE48FYT&colid=3B04RKX85L5W0&psc=1&ref_=lv_ov_lig_dp_it 
https://m.media-amazon.com/images/W/WEBP_402378-T1/images/I/51xLZ8oBuyL._AC_SL1500_.jpg

...is designed for attaching to an HT.  I wonder how well it would do on the end of an LMR-400 coax up highish.

Most here are familiar with the MLA-30 used for receive only on HF.  I wonder if there is an equivalent version for VHF?  It is a powered "active loop" antenna. 
https://www.amazon.com/Antenna-100kHz-30MHz-Receiving-Rainproof-Amplifier/dp/B091Y55VW6/ref=sr_1_3?keywords=mla-30&qid=1663083838&s=electronics&sr=1-3

Or perhaps a VHF version would have less need of being active or powered.

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AI5BC

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #5 on: September 13, 2022, 05:56:33 PM »

Sure do, I can sell you whatever you want. Never mind it looks like a Mag-Mount with a mobile antenna stuck on a cookie sheet. Only $400 sent over night Fed-Ex

Make check payable to Dewey Cheatum & Howe.

Sincerely

Ben Dover.
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KK4GMU

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #6 on: September 14, 2022, 06:03:31 AM »

What a coincidence.  I just had a tooth pulled by a dentist with a similar name:

Dewey Pullman and Howe. 

I'll bet he does antennas, too.  Maybe he can implant a small loop.  Then when I wear my tinfoil had I could hear Cuber.
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WB6BYU

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #7 on: September 14, 2022, 12:42:41 PM »

Like this one?

In stock at HRO.


I expect signals to be weaker than a vertical whip.
And, given the whip can be made with thin wire or
brazing rod and painted to make it unobtrusive,
I doubt the loop would be more stealth.  Besides,
there is a null in the loop pattern, so it isn't
omnidirectional.

My "stealth" antenna for transmitter hunts that I
hide in plain sight is a yellow wasp trap, with the
transmitter inside.  The 2m antenna is an 18" black
wire that the trap hangs from, with 2 black wire
radials draping out the bottom.  Everybody ignores
it, until their antenna points straight at it hanging
in a tree.

Do make sure that you seal the holes in the trap first,
however.
« Last Edit: September 14, 2022, 12:51:39 PM by WB6BYU »
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WA3SKN

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #8 on: September 14, 2022, 03:13:56 PM »

Why not just make a full size loop for 2 meters?  Its only a square with about 20 inches of wire on a side.  Feed it directly with coax at the top or bottom for horizontal polarization, and at either side for vertical.  The loop itself is mounted vertically.  Horizontal mounting for SSB.

-Mike.
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W1RKW

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Re: Magnetic loop antenna for 2 meter RECEIVE ONLY
« Reply #9 on: September 15, 2022, 03:52:43 AM »

could even expand on that and build a 2 or 3 element quad. boom length for a 3 element quad would be about 30 inches.

Why not just make a full size loop for 2 meters?  Its only a square with about 20 inches of wire on a side.  Feed it directly with coax at the top or bottom for horizontal polarization, and at either side for vertical.  The loop itself is mounted vertically.  Horizontal mounting for SSB.

-Mike.
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