In a message dated 99-10-19 21:50:54 EDT, KI7WX@aol.com writes:
> The bandwidth issue rules out a lot of shorty 40s and the interaction
issues
>
> clobber others. So how about using interlaced beams at the top? Say
20/40
> with 10/15 over it and a pair of stacked tribanders sidemounted below.
This
>
> could all be fed with a stackmatch and remote switch to split power and
> phase
> the antennas together. More trouble than tribander + 40M beam, but might
> work out. If the interaction issues are related to 15M one could go
20/40
> with a big 10M yagi over it and forgo the highest 15M beam.
>
> So, lots of options, I'm just curious what people have done in the real
> world. I think I'm going to put some effort into tracking down a 402CD...
The 402CD is a wonderful little antenna so you can't go wrong by
installing one. And it's got 250 kHz of bandwidth.
Here are a couple of developments in this arena. There are some guys in
W6 who have developed coils for 75M beams to replace the linear loading. They
claim that since the linear loaded wires (ala F12) are some distance from the
aluminum element that the efficiency goes down. Apparently most of the W6 big
gun 75M boys have converted with good results. Now I understand that they
have coils for 40M beams too. I've never been too thrilled with linear loaded
antennas so this might be a way to get the best of both worlds - smaller
antenna with more efficiency. I don't remember the name of the company or how
to get ahold of them - sorry. It's W6KW and his cronies.
The other thing is that apparently F12 has designed a new LL antenna
that doesn't self-resonate on 15M. They changed the design and it sounds like
there is little or no interaction so this might be worth investigating.
Unfortunately it's a LL design too.
Even with your proposed interlace antennas you still have to allow
10-12 feet separation but going with F12 designs means that the antennas will
work FB.
Cheers, Steve K7LXC
Tower Tech
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|