[Elecraft] 160m loop experiment a big failure

[Ron D'Eau Claire]

Well, Don, that's how Hams have learned about these things for over 100
years. 

I believe that by "microwave" you are referring to an intense medium
frequency RF field in your home, not to a "microwave" which refers to much,
much higher frequencies in the 1,000 MHz range. However, that terminology
may confuse others since "microwave" refers specifically to frequencies
above 1,000 MHz. 

Keep in mind that you can resonate an antenna either at the point where the
feed line connects to the antenna or at the point at which the feed line
connects to your rig. In the latter case the feed line become part of the
antenna system and must be a low-loss type in most cases. That's why ladder
line or (even better) open wire lines are used when the feed line is part of
the antenna since it may have rather high SWR levels on it. 

Even with a balanced line (and balun at the feed point) you may need a
ground at the rig to prevent "RF in the shack". RF in the shack usually
results from a high-impedance point at the rig end of the feeder. It has
nothing obvious to do with the impedance of the feed line and everything to
do with the RF pattern on the antenna system that includes the feeder.
However, such grounds have little to do with the efficiency of the ground
and a suitable ground to eliminate stray RF may be nothing more than a
single 1/4 wave radial or a ground stake connected to the rig. Another
approach is to change the length of the feeder. Adding or removing 1/4
wavelength will exchange a high-impedance (so high RF voltage) feed point
for a low impedance (and so low RF voltage) feed point that will cure the
problem .

For me, Ham radio has been a fascinating hobby. One of the things we who
have been tinkering for a while get out of it are fond memories of our
experiments over the years. After 59 years on the air, building countless
rigs and hanging endless antennas, I still keep a paper log filled with my
past station setups, antenna and notes along with details of all my
contacts. It's fun reading and sometimes I shake my head, amused at
experiments such as trying to use a 5-foot Tesla coil for an antenna and
noticing corona discharges coming from the top! 

73 and good luck!

Ron AC7AC 



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of goldtr8 at charter.net
Sent: Saturday, October 15, 2011 3:00 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] 160m loop experiment a big failure

Based on all my research today it is apparent that the loop as put up 
will have to come down.

As Don points out, I dont want to be in the middle of the microwave.   I 
just never thought about this other than the nice layout of trees.

Basically I will be pulling it down and use some of my trees and then 
have to put two poles up for two corners.

Plus it is clear since I want to use it on multiple bands that I will 
have to get a 4:1 current balun.

At least the radio warned me that I was making a microwave by all the RF 
in the shack.

I am not as smart on this stuff as I thought I was, as I did research on 
the loop and length and so on, but never figured the effect on being in 
the middle.

But my dipole works just fine and I will continue to be on the air.

Thanks
Don


~73
Don
KD8NNU