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Will a Balun improve my receive performance?

Dec 22nd 2011, 20:24

KQ0J

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Just a question - I have a 6 meter dipole in my attic. I found a 1:1 KLM balun the other day in my junkbox that had a stated range up to 60 mHz. I am wondering if adding that to the dipole would have a positive or negative effect on either transmit or receive.

I may try it just to see if it helps to eliminate some RFI - the smoke detector under the antenna keeps chirping when I am on 6M.


Thoughts / comments?

73
Jan 3rd 2012, 17:22

gw0nvn

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Depending on your antenna design and feed arangement the balun will help. A simple wire dipole will be balanced and have an impedence of about 72 ohms. The balun should help coupled this to your unbalanced coax feeder and help reduce the outer of the coax acting as part of the antenna.

You will need to investigate your problem a little more.

Is the problem frequency specific?
Is there a power level where it doesn't happen?
Is the fire detector system corectly engineered and installed?

A simple thing to remember when dealing with interference. Double the distance quarters the field strength. So providing the problem is not caused by the frequency in use. Moving the antenna and downlead further away from the smoke detector and its wiring will help. You could of course reduce your output power by a half (3dB) to see if this makes any difference.

There is much information on the ARRL website to help. Antennas in attics are always a compromise. But there are times when you can't use outside antennas. I have limited myself to 10W into a wire loop antenna in the attic not to trip nearby smoke detectors.

Being pedantic. Do you really mean 60 millioneth of a Hertz (mHz) and not 60 Million Hertz (MHz). It's a mistake many people do on the Internet in computer and electronics magazines. Even some avertising for Ham Radio equipment from the three big manufacturers have these 'typo' issues.

Have a really good New Year ( but not too serious)

Simon GW0NVN N1XIH

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