[Top] [All Lists]

Hygain 52' Crankup - good for me?

To: <>
Subject: Hygain 52' Crankup - good for me?
From: (Tony Brock-Fisher)
Date: Mon, 1 Jul 1996 10:34:30 -0400

1. The numbers I'm talking about do equate to 8-10 dB total gain for 
the XA, which is their published spec, and which is not unrealistic
for an antenna with a boom length of .5 lambda, which is what the
XA is for a given boom length. When comparing all these antennas
and simulations, and reviewing the results against the W2PV book, etc,
I was certain that all results met with "reality checks" in various
departments. What seems like an unrealistic "reality check" is that
the C3, on a 18 foot boom, can claim to outperform the XA, on a 32 foot

2. As for the heating argument, I can't address the particular incident
you related to me. However, in order for a device to be lossy, there
has to be some lossy material involved. The traps are made out of
conductors and insulators which by their shapes act like inductors
and capacitors. The inductive elements are made out of aluminum tubing,
much like the antenna itself. The losses associated with aluminum tubing
is either resistance (negligible); or skin effect resistance. The skin
effect resistance must also be negligible for reasonable diameter
aluminum tubing, or the C3 would also have similar losses. as for
the capacitors, they are also made of air and aluminum, just like the
caps in the plate section of your linear. These cannot either be 
expected to dissipate significant power. I just cannot find an
explanation for traps which are constructed this way to dissipate
significant power. Traps made with smaller diameter wire would
have higher skin-effect losses - but still very small, as witness
the 40-2CD traps which have a Q of 161 as measured by 'QHS.

3. The XA does have many connections - and therein lies it's
weakness. If it has been properly constructed with the appropriate
goop and is in good condition, these also, I believe, would be 
very low loss connections. Perhaps the connections in the antenna
which was alleged to hav gotten hot were poor. But then, it should
have had bad SWR if the connections weren't right.

4. I'll be changing antennas around this summer - so will have the XA's
back on the ground for a while as tower work gets done. at that time
I may try some experiments to measure any thermal effects.

5. Swapping a TH7 for a C3 is a good move. The TH7 is not as good
a performer as the XA, and is only 1 dB better than the C3, as
per simulations which don't include trap losses. In this case,
I'd call the performance a tie, and I do like the C3 construction.

-Tony, K1KP,

<Prev in Thread] Current Thread [Next in Thread>