My first mag loop | K4UPG.COM

Adventures in Ham Radio QRP Portable Ops!

SIDEBAR

»
S
I
D
E
B
A
R
«

Mag Loop First Attempt

September 5th, 2009 by kmack

I finally got around to putting a mag loop together tonite. Using 10 ft of 5/8′ copper tubing I made a circle and using some lath strips I had laying around I made a lightweight frame. (too light) I had a nice pair of air variable caps mounted in parallel and made an exciter loop for testing out of #12 solid copper wire. Using a BNC to binding post adapter I hooked it up to my MFJ 207 antenna analyzer. It is showing 2:1 SWR on 7.040 and I think with a bit more capacitance I can bring it down. It is too late to do much more tweaking tonight, but I’ll update you on progress and other experiments. Here’s a quick look at it as it is now in its testing mode.

My first attempt at a mag loop in testing mode now

2 Responses

Myles writes:
January 11th, 201211:21 amat

Use a Faraday induction loop, the SWR will be 1.1.

Use the inner of RG-213 coax and slide it into one tube, this acts a a capacitor.
By finding what length is required for a band you are set.
I use 3 lengths, 20M 30M and 40M, you could also have anothe cap in the other tube end, and connect the two with a wire link.
I am using a 2 element in series Magloop – this halves the cap needed to reach resonance.
The Faraday induction loop is never adjusted.
The varying cap tunes to loop.
I also tape the ends on the coax inner to prevent arcing.
Other caps can be made with PET as the dielectric material, soda bottles are made from PET, it will withstand 20KV.

I realise this article is in 2009.

I make 5 Watt contacts on WSPR at 18,600KM everyday.
kmack writes:
January 11th, 201211:29 amat

Myles,

Thanks so much for the input on this… I think I grasp what you are saying and makes a lot of sense to me. Do you have any write up or photos on the net to help me visualize it a bit better? Would love to see how you have done this in more detail… i.e. lengths for the bands and how you are connecting the capacitor and length of coax. When you say 2 element in series Magloop… are you speaking of two main loops or just the faraday inductor?

Very thought provoking and my original loop has been mostly idle and most of my operation is on weekends when I have time to go out in the field portable.

72,
Kelly K4UPG