[Elecraft] Antennas with resistor and OCFD.

[Jim Bolit]

The Rake



-------- Original message --------
From: Fred Jensen <k6dgw at foothill.net>
Date: 12/10/2015 5:54 PM (GMT-10:00)
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Antennas with resistor and OCFD.


On 12/10/2015 4:14 PM, Brian D. Comer wrote:
> I think stating any particular antenna configuration is unacceptable is
> ignoring what could be an ideal antenna for a given situation.

Absolutely!  Situations differ dramatically.  A low angle radiator on 80
in the evening is likely to underwhelm you if your need is to
communicate over 150 miles.

>  As I
> understand  it  a rhombic  uses a resistor, and sometimes works quite well.

Ummm ... rhombics *always* work well for their intended use.
Unterminated, they are bi-directional.  With the terminating resistor,
they are unidirectional in the direction from the feedline to the
terminator.  Since terminated rhombics are usually 2 or more wavelengths
on a side, they have very narrow beamwidths with a big F/B ratio, low
radiation angle, and high gain.

They were used on point-to-point HF circuits in the 30's through maybe
the 60's or so.  I worked coastal marine in 56-57.  We generally used
V-beams with wider beamwidths since our targets were ships that moved
around, but we had a couple of rhombics, one aimed at NMO in Hawaii.
Tap the key at 5 KW and they told us we were QSA 11R5:-)

OCF's can serve well in the right situations and with the right
precautions to mitigate the downsides.  The infamous B&W folded dipole
was never billed as anything other than what it was ... an antenna with
a non-inductive resistance that pretty much swamped any effects from the
antenna, and could be used 3 - 30 MHz, in the right situations.

Tom Schiller, N6BT, likes to show his "illuminator", a 300 W light bulb
fed through a common mode choke.  He even put three up as a "phased
array.  Any RF in any conductor will radiate.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org<http://www.cqp.org>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to jbollit at outlook.com