On Tue, 15 Jun 2010 09:49:22 -0700, Timothy Coker wrote:
>Each time you tune the lower band, the higher band will be affected (amount
>depends on your installation).
The interaction is not as much as you might expect. I have four fan dipoles
in the air now, two are 80/40 fans, two are 20/15/10 fans.
In general, the SWR bandwidth of the lower frequency dipole will be the same
as for a single dipole, while the higher frequency dipoles will see their SWR
bandwidth reduced by half. No problem -- 40M is much narrower than 80M, so
they work fine. If your fan is low, feed it with 50 ohm coax. If it's high
(more than about 80 ft), feed it with 75 ohm coax. Here are links to an
application note on Antennas For Limited Space, followed by a Power Point
with more details and ideas.
http://audiosystemsgroup.com/LimitedSpaceAntennas.pdf
http://audiosystemsgroup.com/LimitedSpaceAntennasPPT.pdf
73, Jim K9YC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|