Thanks John, interesting and encouraging.
Brian VE7JKZ
On 9/18/2013 7:54 AM, John Kaufmann wrote:
I also use a low dipole, ten feet high, as a supplementary receiving
antenna. It's a random length, not even resonant on 160. I make no
effort at all to match it. For receiving only, it's just not
necessary. There is a lot of mismatch to the feedline, but unless
your feedline is very, very long where the mismatch would cause very
large feedline loss, you won't see any difference except for higher
signal levels with matching. However, the SNR should be same with or
without matching because the noise floor is set by atmospheric noise
that comes in on the antenna.
I find the low dipole often comes "alive" right at local sunrise and
allows me to hear and work DX stations (VK's, ZL's, JA's, etc.) that
are inaudible on my multi-element vertical receiving array. The
difference is sometimes dramatic, but it only lasts for a short time.
The rest of the time, the verticals usually kill the dipole for receiving.
73, John W1FV
On 09/17/13, Brian_ve7jkz<ve7jkz@telus.net> wrote:
I've been looking at a very low dipole to hopefully assist in receiving.
Living in suburbia space is limited but thanks to a helpful neighbor I
could put up something in the shape of an L. I would have a 90ft
straight length, then the feedpoint, then a 30ft straight length, a 90
degree turn, followed by another 60 ft straight length. Total length of
180ft approx. Running along the top of the garden fence approx 6ft high.
EZNEC 3 tells me that at 1.83Mhz the feedpoint impedance would be
0.65-j590, and at 3.52Mhz it would be 1.7+j510. How do I match it? I
could always use a relay to switch in some L for 160m and some C for
80m, then a transformer to get to close to 50 ohms, then a high pass
filter because I'm only a few hundred yards from a 50kW BC station on
690Khz, followed by a W7IUV amplifier.
Is this a reasonable approach or is there a better/simpler way?
Brian VE7JKZ
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