[Elecraft] Portable antenna

[Charles Greene]

Hi,

A week or so ago, Wayne was asking about a low noise and I recommended a 
vertical.  Here's my latest finding:

I made up a 20 meter vertical for portable use and installed it on my sea 
wall for test. It is full size, and I used some junk 1" aluminum tubing I 
had in my attic. It has two wire radials elevated 1' above the ground. I 
made the radiator slightly short and the radials about 2' long to bring up 
the feed impedance to 50 ohms and also the impedance of the radials so one 
of them does not hog the current which it is inclined to do if all radials 
are at zero ohms.  The first contact I made was day before yesterday, and I 
got a S9+20 report from the Fiji islands, running 30 watts on PSK31. Then I 
ran some tests on it. It is located about 50' farther away from the house 
than my 6BTV and G5RV. Using Spectrogram, I determined the noise floor was 
10 dB (voltage) lower than the 6BTV and 16 DB lower than the G5RV. The 
received signals were about the same as the other two, with a slight edge, 
1 to 2 DB stronger. On comparative reports I have received on transmit, it 
is running "slightly" to 1 S unit more than the other two. On DX, it is at 
the edge and 8' above sea level at high tide of Narragansett Bay, 4 miles 
wide at this point. On the other two antenna, my 6BTV has 22 radials of 
480' of wire, and the G5RV is 30 ft high and about 50' higher than the sea 
level of the bay at high tide.. Both seem to work well. I knew the G5 was 
noisier than the 6BTV, but that usually does not come into play unless the 
signals are so weak they are in the noise level.
I really can't explain why the vertical is so low noise (my house isn't 
that noisy), and I would have guessed it would have performed a little less 
well than the doublet and the vertical antenna with a fair number of 
radials. I can understand why it is better on the long haul stuff, as it 
has nothing between it and the frezonal zone a mile or two away. I would 
appreciate any comments.




73, Chas, W1CG
K2 #462