[Elecraft] KPA1500 RFI on 12m

Jim Brown jim at audiosystemsgroup.com
Sat Oct 26 04:32:18 EDT 2019


On 10/25/2019 2:01 PM, Bob McGraw K4TAX wrote:
> Except for my 6M yagi, all of my antennas are non-resonant antennas. My 
> favorite is the 256 ft center fed wire {resonant at 1.825 MHz}  with a 
> balanced feed.

Dean Straw, N6BV, retired editor of the ARRL Antenna Book and Antenna 
Compendiums, is a very smart engineer and a very good friend. But his 
promotion of this sort of antenna is probably the greatest error of his 
time in that job, an idea whose time is LONG past, for many reasons. 
Primary -- 1) it cannot be choked to kill noise on RX, and 99.9% of hams 
live surrounded by local noise and 2) it's pattern is different on every 
frequency.

I am a strong believer in resonant antennas for each band, if if the 
must be multi-band antennas like fan dipoles to fit in the available 
space. For example, a 20/15/10 fan fits in 33 ft and works great, with a 
predictable pattern on each band. An 80/40 fan works on 15M, with a 
predictable pattern on both 80 and 40. Hypower Antenna company sells 
loaded antennas that are resonant on 80 and 40 and fit into about 100 
ft; I used one in Chicago on 30 to great effect. All of these antennas 
are fed with 50 or 75 ohm coax, and CAN be choked to kill RX noise.

RX noise is a VERY big deal -- if you can't hear 'em, you can't work 
'em. If you haven't worked to minimize your RX noise, you're DXing with 
one hand tied behind your back! My friend AG6EE goes to remote locations 
in NV, OR, and CA to light up rare grids with 1kW on 6M. Folks trying to 
work him complain of one-way propagation because he hears them really 
well and the don't hear him, but the REAL problem is their local RX noise.

http://k9yc.com/KillingReceiveNoise.pdf  Text, NCJ article
http://k9yc.com/KillingRXNoiseVisalia.pdf  Slides Visalia talk

73, Jim K9YC


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