[AMRadio] Loop antenna feed question


Jim Wilhite w5jo at brightok.net
Sun Dec 4 21:27:35 EST 2005


Ask yourself, what do you gain by using a Loop?  From a transmit 
perspective, not much, if anything.  I have heard many people switch from 
loops to dipoles at the same power level and location and saw little 
difference.

>From a receive perspective, maybe something.  You might reduce noise in your 
receiver.  I can't speak to this since I have never used a Loop.

So, you gain in your receiver, but that is all.  What good is it to hear 
someone if you can't put a signal to him/her?  Not only that, you use 2X the 
wire to build a loop which won't transmit any better than an inverted Vee at 
the same height.

If you want close in communications out to 150 miles daytime and 300 or so 
nighttime (under current propagation conditions) on 75 use a low antenna. 
If you desire communications out further than that, get the antenna up over 
40 ft and the ends more than 20 ft. off the ground.  So long as the angle of 
the legs are more than 100 degrees.

Where all this falls down is the ground.  If the voltage points are near 
ground the worms will love you, if the current node is near ground, 
impedance problems.  So you have a choice.  In past years that I couldn't 
get my antenna up in the clear, I made lots of friends close in and always 
dropped out if someone couldn't hear me.

Remember----there are no short cuts on antennas.  Proper installation equals 
good results for the desired coverage and design matters little.

73  Jim
W5JO





> LB Cebik, W4RNL, on his web site, talking about Cloud Warmers, indicates 
> 35
> feet as the accepted height for a 75m loop. I am planning a loop for 160m 
> at
> just a little over that height.
>                                 Joe W4AAB



>
>
>> John,
>>
>> Hmmm.... 450" loop at 5'.   Feedpoint impedance would vary all over the
> place
>> depending on frequency.   Do you transmitting on this setup, and if so,
> are
>> you using some kind of an antenna tuner, balanced output or single ended,
> how
>> long is the feedline, and what frequencies do you intend to use?   In any
> case,
>> can't see that fanning out at the feedpoint would be necessary or useful.
>>
>> Dennis D. W7QHO
>> Glendale, CA





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