Help w/Amp 80m Anomaly?

[Scott Ellington]

Brian Short wrote:

> Suddenly, the amp shut down, blowing both 250v 15a fuses.

Most likely one of the tubes in the amp flashed over.  It's
unlikely an RF arc would cause the amp to blow the fuses.
If a tube flashed over, it may or may not still work.

-- 
73,

Scott  K9MA
sdelling at facstaff.wisc.edu

>From 74237.2073 at CompuServe.COM (James W. Fisher, Jr.)  Wed Jan 15 17:17:57 1997
From: 74237.2073 at CompuServe.COM (James W. Fisher, Jr.) (James W. Fisher, Jr.)
Date: 15 Jan 97 12:17:57 EST
Subject: GAP VERTICAL PHASED???
Message-ID: <970115171756_74237.2073_BHR40-1 at CompuServe.COM>

Sergio, PP5JR/ZX5J (pp5jr at pp5jr.ampr.org) writes:

>i have 2 Voyager DX ( GAP- vertical for 20-40-80-160), and i'd like some
>information if is it possible to phased them on 80 and 160m.

Yes, but with simple arrangements, the end-fire pattern would be valid for
only one of the two bands.  In addition to various homebrew arrangements,
commercial possibilities include Dunestar SM-03/V, which phases the two
broadside on all bands and switchable end-fire on one selected band.  The
broadside pattern would be OK on both 80 and 160 if you space them 1/4 wave
on 160.  Above 80, it would split due to the over-5/8 wl spacing.  The
Dunestar Model 834 would also be a possibility; that drives either element
and leaves the second element as a reflector.  Some modeling or discussions
with them would be required to see what would happen given different
spacings and feedlengths of different characteristic coaxes.  Dunestar is
reachable at AA7EA at AOL.COM. You might also want to contact COMTEK systems as
(704) 542-4808 and discuss their offerings to see if they have something
suitable.

>>If possible witch is the ideal distance between them, and witch is the cable
that i need to use. 

If you want an arrangement similar to the one I described first, where both
bands have broadside and one has switchable end-fire, you should space them
1/4 wl at the band you want to use end-fire.  The GAP seems to work
much better on 80 than 160, so that might influence your choice in either
direction.

>>Secound question about this type of antena: If i put a lot of radials, for
>>160m, for example, i will improve de gain?

I've done this with my GAP Voyager to improve efficiency, but an added
complexity is the counterpoises.  After reading ON4UN's article in Sept 96
CQ Contest, while he was talking about radials rather than counterpoises, I
decided to lift the counterpoise wires as they run away from the base, taking
them up at a 45 degree angle and then off at more-or-less two meters above
the ground (and the 15 or so long radials I have laid so far on the ground).
I have yet to receive any qualified technical comments as to whether lifting
the counterpoise was a good idea.  The revised system seems to work better
on 80.  It may work better on 160 too but efficiency still seems pretty low.

Sergio, another good source of advice on antennas as well as towers is
Towertalk, and I've taken the liberty of forwarding this reply there as well
as to the CQ-CONTEST reflector on which you posted it.  If you care to
subscribe, it's towertalk at contesting.com and the mentor is Steve, K7LXC at
K7LXC at contesting.com.

73 es GL,

Jim, VE1JF/W8JF