On 11/3/99 0:00, Herb Rosenberg at herbr@netcom.com wrote:
>I think this has been covered here before, but I would appreciate hearing
>comments about the Cushcraft R7000, especially in these areas:
>
>Power Handling? Will this antenna RELIABLY withstand 1500 watts into
>it?
I think that depends on how you define 1500 watts. If you mean 1500 watts
full duty cycle, I'd say no. I've heard far too many stories of people
frying a trap or the matchbox at that power level. It's probably OK for
1500 watts PEP on SSB -- duty cycle for SSB is 40% or lower. But CW or
RTTY is another matter.
>I want to use it for a second antenna in rtty contesting,
>and need it to be able to handle the load without frying.
I wouldn't recommend it for 1500 watts RTTY. 500 or so sounds about right.
>Ground Mount or Elevated? What is your experience here? I can easily do
>either, would like the optimum set up?
Don't ground mount a R7000. The manual recommends at least 8 feet in the
air, and 25 feet from all obstructions. The design told me the antenna is
optimized for a height of 18 feet. Going much higher doesn't improve
things much. Anywhere from 8 to 25 feet should be OK.
>SWR Bandwidth: What does it look like? Is it really flat on each band,
>or how close to their specs is it? Can the center point be adjusted, or
>is it fixed on each band?
This is subject of some debate. Early units apparently had some variation
in the traps, caused by production. Several owners of these early units
(like myself) cannot get the rated specs for SWR bandwidth out of the
antenna. Later units have a slightly modified trap design which is more
consistant.
Even so, your results will vary. Much will depend on how well your
installation comes close to the ideal antenna-range installation
Cushcraft measured.
As for adjustments, my experience has been that the R7000 is so dominated
by trap resonances that anything other than minor adjustments are pretty
useless. It usually works fairly well with the factory lengths. On the
lowest band - 40m, you can pretty much put the SWR dip where you want it.
On the higher bands, it probably isn't worth it.
If you have an automatic antenna tuner, I wouldn't worry too much about
the SWR bandwidth. Although some owners claim that their R7000 came with
a warning label that the warranty was void if they used an antenna tuner.
>Comparisons: Anyone have comparison information with this antenna to a
>Hygain, Gap or other multi band vertical?
The R7000 has the advantage of being mechanically simple and robust for a
7-band vertical. It's performance is comparible with these other designs.
Some early owners have had fold-over problems. Cushcraft made a design
change to incorporate some reinforcing around the CT1 (bottom) trap. This
reinforcing used to be part of the 80m extension kit (R80), but now is
part of the standard R7000.
>Overall impressions? How satisfied are you with it? Is there a better
>multiband vertical out there? Any commments would be appreciated.
It's not a bad antenna. It performs fairly well on 40m and the WARC
bands. On 20, 15 and 10m, you're competing against a lot of tribanders
and other beams, so it doesn't do so well.
I bought the R7000 as a second rig antenna, but I haven't gotten my tower
up, so I've been using it as my main antenna for 3 years. I have never
gotten the SWR bandwidth figures that Cushcraft claims. My recent
correspondence with Cushcraft has beenless than satisfactory, and I
suspect that I may have a trap or two that has a manufacturing defect
(but I haven't figured out how to prove it).
As for a better multiband vertical, the R7000's predecessor - the R7 -
may have offered slightly better performance. It also had many more
parts. I've heard from a lot more satisfied R7 owners than R7000 owners.
But a multiband vertical such as this is a compromise antenna. It's only
going to work so well, although you can work a lot of stations with such
an antenna.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@radio.org
Quote: "Boot, you transistorized tormentor! Boot!"
-- Archibald Asparagus, VeggieTales
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