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mfj 1798 vs. GAP verticals

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Subject: mfj 1798 vs. GAP verticals
From: 74237.2073@CompuServe.COM (James W. Fisher)
Date: 02 Jan 97 17:09:34 EST
Comparisons were invited.  I haven't used the MFJ ant but this is perhaps the
opportunity to summarize the comments I received from fellow towertalk GAP
owners, plus my own.  Thanks to K7LXC, N4XY, N8JF (!--my US call is W8JF!) for

1. Everybody was complimentary on 80 and 40 performance (20 works fine too but
probably most GAP owners use another antenna on 20).

2. 160 meter LOADS OK (and if you want to move the resonance on this and/or
another band  the factory is very helpful).

3. 160 meter PERFORMANCE was disappointing to everybody but N4XY, who rated it
"at least OK" but was running an Alpha 78 with 3 8874s.

I reported on my attempts to improve performance on 80 and 160:
o Raised the radials a few feet above ground (average probably about 7'), with
the near ends brought down at a 45 degree angle to base
o successfully moved resonance points (contact factory with your specific needs)
o put in a ground system--perhaps 12 or 15 radials ranging from 150' to 250'
(plan to add more).
o put in Radiowire coaxial choke ($26) between antenna and coax to shack.

Seemed to help on 80 (nothing scientific--comparing my perceived 80-M
competitiveness on CQWW CW test in 1995 vs. 96; ability to sustain runs; time
before success in modest pileups in S&P).  160 is still disappointing
head-to-head with stations where I know the equipment/location/antenna vs. mine.
It appears that the inherent loss in the 160-meter matching arrangement is
significant and that the ground loss reduction through lifting the counterpoise
and adding radials was not sufficient to transform this into a competitive
antenna.  The most telling similar evidence was from K7LXC who operated from a
beach above the ground (salt) water and said the response to his calls was poor.

I received no feedback on the technical reasonableness of the steps I took to
improve performance.

Mechanically the GAP looks good (even my XYL thinks so, and she rates radio
amateury as right down there with mass murder and toxic waste dumping) and has
held up against coastal winds with no apparent problem so far.  The factory has
been very responsive to my questions.

Hope this helps.  Good luck in your choice!


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