In a message dated 97-03-18 13:00:37 EST, email@example.com (Carlos
Augusto S. Pereira) writes:
> A local ham is selling a Hy-Gain TH7DX beam. My current set up has a Mosley
> TA-33, in other words, a 3 el. triband Yagi. Is it worthy to replace the
> TA-33 with the TH7DX? Does anyone have compared the TH7 with a 3 el
> beam? Of course the TH7 is superior but how much better it really is. I
> mean, in DB what would be the differences between the two beams
> the same height per band?
The TA-33 has a boom length of 14 feet; the TH7 is 24 feet - almost
double. And YES, a very worthwhile improvement. The exact gain differences
in the real world is the subject of some argument.
> I have heard that the Hy-gain engineers optmized the F/B and didn't care
> much about FWD gain! Is that right? Is it much worse compared to the KLM
> KT34XA? Also what is the difference between the TH7DX and TH7DXS?
The Hy-Gain antenna range is much more suited to testing F/B than
forward gain. If you were an antenna designer, you'd know that many times
when you decrease the amount of signal off the back of the antenna, the
energy that goes out the front of the yagi increases (more F/B, more gain).
Of course they cared about gain! The fact that the TH6/TH7's are
probably the most popular high performance tribanders ever made and used by
thousands of hams around the world shows how successful Hy-Gain antenna
designers were in creating an antenna that REALLY WORKS.
The TH7 and the KT34XA are practically identical in terms of on-the-air
I don't know what a TH7DXS is except it probably means Stainless Steel
TOWER TECH has a reprint of a test done in the 80's that compares 10
different triband antennas. It's not the definitive antenna test but does
give you more information in regard to your questions. An SASE to TOWER
TECH, Box 572, Woodinville, WA, 98072, USA, will get you a free copy.
73, Steve K7LXC
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