I am quite happy with my Discoverer 2-element.
It´s now about 15 years on the tower and never had a problem, except the
insulators on the driven element which burned out when I was not aware of
icing on the antenna.
Being only 18m high it?s a very well performing antenna.
My 3-element full size at 38m is in the average 1 s-unit better and to
California the difference is 10dB, but that is mainly due to the much lower
elevation angle of the high yagi.
It compares pretty well with my 4-square on DX.
During the summer I will move it 10m higher.
Front to back is as expected, about 15-20dB.
73
Peter
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
Sent: Montag, 19. Juni 2017 15:56
To: towertalk@contesting.com
Subject: [TowerTalk] 40 Meter Yagi
Date: Sun, 18 Jun 2017 11:02:02 -0600
From: "Doug Renwick" <ve5ra@sasktel.net>
To: "'AB2E Darrell'" <ab2e@hotmail.com>, "'Kim Elmore'"
<cw_de_n5op@sbcglobal.net>, "'Gary'" <gary_mayfield@hotmail.com>
Cc: <towertalk@contesting.com>
Subject: Re: [TowerTalk] 40 Meter Yagi
<Hi,
<I junked my Hygain Discoverer and replaced it with the XM-240. The linear
<loading wires near a bend at the end would keep 'breaking'. Keep in mind
the
<XM-240 balun is a piece of junk. The rest of the antenna is good value.
<Doug
## Linear loading is out of vogue these days. But the coils used in the
XM-240
leave a bit to be desired, too lossy imo. They could have done the coils
better.
Still, its a proven performer.
## 68 turns of 12 ga magnet wire, wound tight, on a 5.57 inch long x .75
OD solid fiberglass rod
results in a less than optimum coil Q...like Q = 81.
http://www.qsl.net/ve6wz/CC_coil.html Steve rewound the
oem CC coils with hb coils made of .1875 AL tubing, air core.
11.5 turns, 5 inch diameter, 5 inch long x .1875 inch OD Al tubing,
3003-H0 alloy. Q=767
The complete unit weighs 12.1 oz.
The original CC coil weighs 11.4 oz.
## If made from .1875 Cu tubing, the tubing weight would have increased
by aprx 2.76 X. Q = 1200
## If you use Termans formulae, the coil Q is even less, but this is all
debatable.
## JK antennas winds their 40m coils from .25 inch solid AL...then welds
the ends. Zero ohm connections.
https://jkantennas.com/manufacturing.html
Jim VE7RF
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