My dad (W5JHJ, SK) used an AV640 for a number of years on 40 m when we
had a schedule between OK and CO on 40 m every Sunday afternoon. It was
up about 10 ft above the ground attached to the eave of the roof. As I
recall, it tuned by the book after assembly. It looked wobbly but held
up fine for many years. I used double hose clamps on everything and also
Ox-Gard on every mechanical connection. The only problem I recall with
it (other than it was rather complex to assemble) was that there was a
strap from the matching assembly to the vertical element that flexed
slightly as the antenna moved in the wind. That strap finally broke due
to fatigue, so I fashioned another one and it worked FB after that.
I vaguely recall that the instructions said there was a sweet spot in
the mounting height; 10 - 30 ft or something like that. I never quite
understood why and it was never an issue, anyway.
73,
Kim N5OP
On 10/24/2015 6:23 PM, Roger (K8RI) on TT wrote:
From my experience with the AV640, I am impressed with it on 40 meters
(Its lowest band) mounted at 25 and 32 feet with it matching the
center fed,sloping half wave on average for DX. Due to its
sensitivity to nearby objects I wouldn't recommend it as a limited
space antenna. OTOH if that's the only space available, I'd use one.
Get it as high as possible, or convenient. Tripod roof top mount,
short pole or tower.
I do have one caveat for both antennas. There are a lot of mechanical
connections for jumpers, coils, traps and stubs subject to corrosion.
I'm not down wind from any nearby industry, but I still get a lot of
degradation of solder and Al to Al connections. The solder turns grey
and just crumbles away. Al to Al held by screws often gets a buildup
between the Al pieces. I have needed to redo a number of the coil and
jumper connections on the AV640. I've had good luck with liquid
Electrical tape. Around here the clear Krylon doesn't last long. YMMV
As a comparison, All of my C3i antennas (one 7L 6-meter, two 12L 147,
and two 11L 440s) have had all solder joints for the matching networks
fail. What solder was left would crumble to powder when rubbed between
my thumb and fore finger. Those all had several coats of clear
Krylon. They are getting liquid electrical tape.
73
Roger (K8RI)
On 10/24/2015 6:48 PM, Jim Brown wrote:
On Sat,10/24/2015 6:49 AM, Daniel Danny Horvat wrote:
There is no R6 antenna, there is a R-6000 antenna which I designed for
Cushcraft followed by R8 antenna which was covered in K7LXC & N0AX
report
with high score.
Congrats on your work, Danny. It's not easy getting good performance
with small size!
I was against implementing a 80m on R8 vertical back then (1998) due
low
efficiency and narrow bandwidth. MFJ has no problem to claim
anything just
to sell.
N0AX acknowledged this in his write-up of their tests. Only a fool
would expect otherwise. :) His advice for all of these antennas as a
class was to buy one rated for at least one band lower than you
intend to operate with it. That is, if you want to work 40, buy one
that will work 80, and don't expect good performance on 80M from a 30
ft vertical.
Verticals, R5/R7 R6000 R8 and also clones AV620, AV640 are IMO better
My friend K9OR, a very good op on a very small lot in Evanston (near
Chicago), has done very well with an AV640 on the roof of his small
ranch-style home.
than 43 foot verticals or even worse CHA250 and clone verticals.
I suggest that anyone considering an HF vertical or other antennas
for limited space take a look at these pieces on my website.
http://k9yc.com/VerticalHeight.pdf
http://k9yc.com/43FtVertical.pdf
http://k9yc.com/VertOrHorizontal-Slides.pdf
73, Jim K9YC
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--
Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
/"In theory there is no difference between theory and practice. But, in
practice, there is." //– Attributed to many people; it’s so true that it
doesn’t matter who said it./
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