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High Minimum SWR (2.5 - 3.0) on 20m

Apr 3rd 2016, 10:53

WA2FTV

Joined: Mar 3rd 2012, 03:12
Total Topics: 0
Total Posts: 0
Hello Everybody,

I am hoping someone can provide some insight to this issue.

I have a homemade fan dipole (40m, 20m, 15, 10m) inside my apartment mounted near the ceiling with swag hooks along the perimeter of the room walls. There is no way to get an outside antenna. The wires are about 2 inches apart.

Readings below are from a MFJ 259 antenna analyzer.

On 10m, 15m and 40m, I can get a decent minimum SWR at resonance (1.25 - 1.5).

However, on 20m, the lowest SWR I can achieve is in the 2.5 -3.0 at resonance. Does anyone have a guess as to why and what might be causing this and is there a remedy?

Thank You for your input. It is appreciated very much.

Best Regards and 73s

Cedric
WA2FTV
Apr 3rd 2016, 12:44

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Cedric -

Tell us more about your apartment. Is it wood construction? Steel and concrete? The more "open" and insulating (like wood) the better. Some urban construction works like a Faraday Cage - keeping RF in (or out). Are you able to receive OK?

Your antenna is likely to be interacting with other conductors nearby -- power, telephone, cable, even plumbing. So it's not surprising that you have trouble tuning it. Something in the area may be near resonance in the 20 M band. Do you get RF in your telephone or TV? That's a sign. You could try reorienting the wire to see if that helps.

You may need an antenna tuner to get a reasonable match.

73 Martin AA6E
May 5th 2016, 23:30

K6BOR

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
What is the best antenna for low SWR I can buy to put on our porch.
We are on the 2nd story of a two story apt? This is for 40 thru 10 meters.
K6bor
May 5th 2016, 23:31

K6BOR

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
What is the best antenna for low SWR I can buy to put on our porch.
We are on the 2nd story of a two story apt? This is for 40 thru 10 meters.
K6bor
May 6th 2016, 13:37

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
What is the apartment made out of? Wood frame buildings are reasonably transparent to RF, but concrete and steel structures are very effective RF shields. You may want to experiment with a short length of wire as a receive antenna to investigate whether you could get out or not. I recall one case in which a ham enclosed his balcony--after doing so his antennas would no longer work.

http://www.mfjenterprises.com/Product.php?productid=MFJ-1623
You might download and study the manual for this antenna designed for balcony use.

Zack W1VT
ARRL Senior Lab Engineer

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