[mythtv-users] OT: Indoor VHF gain antenna
gull at gull.us
Wed Jan 27 01:24:02 UTC 2010
On Tue, January 26, 2010 5:09 pm, Tom wrote:
> You need to know the actual frequency of RF channel 9, and whether it's
> been moved to a UHF allocation in the digital transition.
It hasn't. It's actually on RF channel 9, which puts the DTV carrier at
186.31 MHz. Indeed, my dipole worked best when trimmed to about 2.5 feet
long, which fits the usual dipole formula of L=468/f. As Brian pointed
out, though, I haven't matched it properly.
> Aiming it could be tricky, not to mention picky.
The wall it's on faces north, and the transmitter site is north-northwest.
Aiming is the least of my worries -- any antenna small enough to be
practical indoors is going to have a pretty wide beamwidth.
> But the dimensions of the reflectors, directors, and driven element are
> critical. Contruction is not so critical. It's better to use larger size
> conductors, like maybe 1/4" aluminum rod, but heck, even 12 gauge copper
> wire will do. You could tape it to the ceiling, if there isn't tons of
> metal in the walls facing the station.
Yeah, that was my thinking...
Thanks for the web links. I'm going to fix the mismatch on my simple
dipole first, but if that doesn't work I may try for a Yagi design.
Frankly, this is a lot easier on UHF, not because the physics are any
different, but just because a UHF antenna with substantial gain is much
smaller. I have a four-bay bowtie antenna that's working great for UHF
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