The antenna pattern is highly predictable using modeling software.

oh it's predictable all right, however it's often USELESS. it's a
compromise antenna relative to decent dipoles.

Gravity

PHP!

http://www.commparts.com/catalog/ima...ts/8010ABD.gif

i'm too lazy to provide more links.

Gravity

These included
a 25 ft marine whip, and a military vehicular antenna. All you need is a
3 dB pad for 3:1 VISOR.

you can burn up 6 dB in an antenuator and RG 58. and that's if the SWR is 1
to 1.

if someone has interest in 28 mhz, just put up a rotatable dipole too.

Gravity

Giving a power rating to a dipole is suspicious also; although voltage
breakdown may be a factor. Note that it is rated at 400 WE "ROMS"
-- whatever the heck that is supposed to mean.

400 w RMS.
750 w peak.

Gravity

check out their Windom. not bad.

http://www.eham.net/reviews/detail/5840

Gravity

"Frank" wrote in message
news:uZxng.91997$S61.76029@edtnps90...
Sorry I must have clicked spell check for VSWR not "VISOR"! Also
"W" for "WE" and "RMS" for "ROMS".

i googled VISOR thinking it was some cool military antenna.

Gravity

Frank, in the absence of information on the balun, I did model it as
ideal, and that the load at the load end of the coax was 4200 ohms.
That is probably a reasonable assumption.

i dunno it's a 1:1 Balun.

i might email them, cause threads like this are pure profit for them.

Gravity

On Sun, 25 Jun 2006 15:26:13 GMT, "Frank"
wrote:


The antenna pattern is highly predictable using modeling software.
The transmission line losses are probably not as high as Owen predicts
since we do not know the value of the attenuator inside the balun.

That implies there is an attenuator inside the balun. I don't believe
we actually have any information with which to better understand the
balun.

Frank, in the absence of information on the balun, I did model it as
ideal, and that the load at the load end of the coax was 4200 ohms.
That is probably a reasonable assumption.

A real balun would not perfectly isolate the transmission line from
drive so influencing feed point impedance , and would probably
transform the real feed point impedance to something different to 4200
ohms, and so the line losses could be different (better or worse).

If the balun was built with substantial loss, it would tend to reduce
line losses, and yes, 3dB of loss (which would affect performance on
all bands), would improve the performance on 7MHz (though that balun
doesn't look like it contains a 200W dissipater).

All in all, the configuration, although used widely, can be expected
to perform poorly. IMHO was right in being
suspicious of the product claims.

Owen
--

On Sat, 24 Jun 2006 22:19:43 -0400, Dave wrote:

I get product not found!!

Is the URL complete?

Googling indicates that several domains are directed to this eCommerce
website, including jeanshobbies.com, amateurradio.org, buxomm.com,
commparts.com, packetradio.com.

Did someone say this guy is an Elmer? Looks like he runs a business
with a lot of front doors.

Owen
--

"Owen Duffy" wrote in message
news
On Sun, 25 Jun 2006 15:26:13 GMT, "Frank"
wrote:


The antenna pattern is highly predictable using modeling software.
The transmission line losses are probably not as high as Owen predicts
since we do not know the value of the attenuator inside the balun.

That implies there is an attenuator inside the balun. I don't believe
we actually have any information with which to better understand the
balun.

Frank, in the absence of information on the balun, I did model it as
ideal, and that the load at the load end of the coax was 4200 ohms.
That is probably a reasonable assumption.

A real balun would not perfectly isolate the transmission line from
drive so influencing feed point impedance , and would probably
transform the real feed point impedance to something different to 4200
ohms, and so the line losses could be different (better or worse).

If the balun was built with substantial loss, it would tend to reduce
line losses, and yes, 3dB of loss (which would affect performance on
all bands), would improve the performance on 7MHz (though that balun
doesn't look like it contains a 200W dissipater).

All in all, the configuration, although used widely, can be expected
to perform poorly. IMHO was right in being
suspicious of the product claims.

Owen

I am inclined to agree with you Owen. I was being a little facetious
about the load. I also noticed there is not a single specification on the
web site, except for power ratings. (Including the irritating term
"RMS power"). Incidentally 750 W into 4200 ohms represents
2.5 kV peak. If the balun is a real transformer it must be well
insulated.

Frank