Radio Preppers

General Category => Antennas => Topic started by: johno on April 23, 2018, 11:05:16 PM

Title: Magnetic loop antenna.
Post by: johno on April 23, 2018, 11:05:16 PM
I've tried different antennas for my RV, using my ICOM-7000 with the AH8 tuner and a long wire or a Buddy Pole.  It's hard to put up an antenna with other campers around and the park rangers don't want anything hanging from trees, and I'm afraid someone will walk into the tips of the Buddy Pole.  So, I've started using an Alpha magnetic loop with my HB1B and some RG-6.  RG-8 weighs more than the loop and the radio combined and is awkward to store.  The RG-6 “seems to be” ok for this, but I'm still in the trial stage.  Also, in case I break the coax, RG-6 and connectors are available just about everywhere.

The only real problem I've had with the loop is the little tripod it came with is junk, and after about the first 15 minutes I got my regular camera tripod out and suspended a part of a tractor 3 point hitch iron from it with a bungee cord because of gusty winds.  The loop receives very well, and many time signals are so strong it's hard to tune in the exact station I want, they are all so close together.

Anyone have experience with a magnetic loop antenna? 

N5AZO/WQYX855
Title: Re: Magnetic loop antenna.
Post by: gil on April 24, 2018, 04:29:53 AM
Hi, yes, but I had a larger one, which I built out of copper pipes, 21ft diameter. Loops work very well. You just have to retune them every time you change frequency. If you use a short length of coax, try RG-316...

Gil.
Title: Re: Magnetic loop antenna.
Post by: johno on April 24, 2018, 09:43:03 PM
??  21 x 3.14159=.....wow, that's a lot of copper! 

I think it was Bob Grove of Monitoring Times that started a big discussion a few years ago about using RG-6.  I know we use it at a lot higher frequencies that 30 megs.  I'll certainly look into your suggestion.  I used RG-6 because I had about a mile of it and some connectors.

To me, light weight is good.  I'm now living in my first bug out location, but keep the camper fully stocked and ready to go. 

Just for info, radio station WLO transmits weather and pirate activity reports on 8.470.8 megs USB in RTTY and SITOR-B and are authorized to operate with emergency organizations should the need arise like in another Katrina scenario where everything is gone.  I monitored the bands for hurricane Harvey and the Puerto Rican hurricane and there was virtually nothing to hear, which shows me that we have a long way to go.
Title: Re: Magnetic loop antenna.
Post by: RadioRay on April 24, 2018, 09:46:54 PM
I had FCC add 'narrow band telegraphy' on my marine SSB license many years ago, so was able to talk with Rene' from WLO once, during Night of Nights on marine freqs when I lived aboard.  That was fun. Unfortunately, I received that after they stopped issuing the 4 letter ship's calls to 'voluntarily equipped' vessels, so my call sign in Marine Morse was about a foot and a half long - ha ha.
Title: Re: Magnetic loop antenna.
Post by: Jon_Garfio on April 25, 2018, 02:08:01 AM
I made this two months ago.
It is amazing how works into the floor.
The problem is found a good variable Air capacitor at low price.(https://uploads.tapatalk-cdn.com/20180425/d378f8086c31f2b95fd22aadca6ba37a.jpg)

Enviado desde mi Redmi Note 4 mediante Tapatalk

Title: Re: Magnetic loop antenna.
Post by: gil on April 25, 2018, 03:39:49 AM
Quote
??  21 x 3.14159=.....wow, that's a lot of copper! 

Oops, I meant perimeter, not diameter!

Good looking loop Jon. Now you can get fairly cheap vacuum capacitors from Russia, not much more than a good air capacitor.

Gil.
Title: Magnetic loop antenna.
Post by: N1KTJ on April 26, 2018, 06:34:57 AM
I've tried different antennas for my RV, using my ICOM-7000 with the AH8 tuner and a long wire or a Buddy Pole.  It's hard to put up an antenna with other campers around and the park rangers don't want anything hanging from trees, and I'm afraid someone will walk into the tips of the Buddy Pole.  So, I've started using an Alpha magnetic loop with my HB1B and some RG-6.  RG-8 weighs more than the loop and the radio combined and is awkward to store.  The RG-6 “seems to be” ok for this, but I'm still in the trial stage.  Also, in case I break the coax, RG-6 and connectors are available just about everywhere.

The only real problem I've had with the loop is the little tripod it came with is junk, and after about the first 15 minutes I got my regular camera tripod out and suspended a part of a tractor 3 point hitch iron from it with a bungee cord because of gusty winds.  The loop receives very well, and many time signals are so strong it's hard to tune in the exact station I want, they are all so close together.

Anyone have experience with a magnetic loop antenna? 

N5AZO/WQYX855

Have an RV and just sold my loop. It was QRP only. Good for digital jt65 but not a lot else. Saw a few videos on YouTube about loops and respectable hams mention it’s not very efficient with its RF.

Suggestion 1: look at EAGLE antennas. They have an RV set up that many love. Mounts on the ladder.

Suggestion 2:  MFJ big ears.  Bought that set up as other ham club members have the same. Great for portable at 100w output.

N1KTJ


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Title: Re: Magnetic loop antenna.
Post by: gil on April 26, 2018, 07:03:21 AM
Loops can be very efficient, but small loops sold by most antenna companies are just too short. Best for 20/30/40m would be a 19ft perimeter loop.

Gil.
Title: Re: Magnetic loop antenna.
Post by: N1KTJ on April 26, 2018, 10:42:09 AM
Loops can be very efficient, but small loops sold by most antenna companies are just too short. Best for 20/30/40m would be a 19ft perimeter loop.

Gil.

And that can handle 100w with all components. Not just QRP. If you can find one.


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Title: Re: Magnetic loop antenna.
Post by: Skynet on May 15, 2018, 08:31:38 PM
Hi
I found a nice windows calculator for magnetic loops antenna which works from 1 thru 30Mhz Imperial and metric readouts of data.
 http://www.iw5edi.com/software/magnetic-loop-calculator  (http://www.iw5edi.com/software/magnetic-loop-calculator) KI6GD designed it.

I'm building a loop for 20m meters with 7/8 AVA5-50 hardline which has an outside diameter of 1" or 25.4mm
The loop is going to be 16' circumference 5'1" diameter. I bought a 20 thru 130pf 4kv variable capacitor.
Don