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Old 21-Dec-2019, 3:20 PM   #29
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,569
Quote:
Originally Posted by BigHenry View Post
As suggested by rabbit73 in an earlier post, I figured out a way to shorten my balun leads to 2.5" while still able to mount the balun. As if by magic I'm now receiving solid signal strengths on ALL original channels (7.1, 7.2, 10.1-10.5, 15.1-15.4, 24.1, 27.1-27.4, 38.1-38.6.

I would like to thank all who helped me out, with a special thanks to rabbit73 for the balun testing leading to the discovery of an optimal balun lead length.
Thank you for the report of improved reception. I'm glad that my balun tests gave you an idea that helped. I hope the improvement will continue.
Quote:
Frankly, antennas, baluns/leads and RF frequency waves seem like voodoo to me.
Antennas have always seemed like magic to me. I have been experimenting with them since I was 8; I'm now 86.
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Could any of you experts on the forum help me understand why shortening balun leads so dramatically improved my reception. Does the orientation of the leads also have an effect? e.g. like the leads in close parallel proximity or spread apart as far from each other as possible.
A little bit of luck helped both of us.

The wire leads from the antenna terminals to the balun form a transmission line. The transmission line transfers the signal energy from the antenna terminals to the balun. If the design of the transmission line is correct, most of the energy will reach the balun.

The transmission line must have the correct impedance and length to match the output impedance of the antenna terminals to the input impedance of the balun windings. The impedance of the transmission line is determined by the diameter of the wires and the spacing between the wires. My thought was to make it look something like the spacing of 300 ohm twinlead. Some baluns actually have 300 ohm twin lead instead of two separate wires.
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Lastly, as long as balun lead placement won't mess up my reception, I am thinking of inverting the threaded studs to which the balun leads attach, so they will now be beneath the boom and once again the balun will hang down on the centerline below the boom.
My reaction is similar to Tim's. Don't mess with it if it's working. If you do mess with it, make certain you can put it back the way it was. The studs will become part of the transmission line.

When I was young, I built an audio amplifier on a breadboard using two 6L6 tubes in push-pull in the output stage. It worked very well. I bought an aluminum chassis and mounted the parts on the chassis. It didn't work as well.

When I was older, I built a regulated power supply for an electronic flash using transformers connected to form a saturable reactor to regulate the voltage with a small DC control current. I built it in an enclosure that I had on hand; it worked very well. I built a second power supply in a fancy cabinet with a carrying handle. It didn't work as well, and I never could figure out why.

Thanks again, Don for your report of success with the balun. I consider it a Christmas present from you to me.

Best regards,
rabbit73
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Last edited by rabbit73; 21-Dec-2019 at 7:00 PM.
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