[ScanIndiana] Attic antennas

[ArnalCC at aol.com]

Message: 4          Date: Sun, 30 Jan 2005 13:53:54 -0500
From: "Terry Hoover" <tghoover at iquest.net>
To: "Indiana Scanning" <scanindiana at mailman.qth.net>


Could I benefit from an antenna in the attic of my home? I live in a sub
that has outdoor antenna restrictions I can barely get by with a Satellite
dish, if I can get by with an Ant in the Attic which type of ant. would I
get the most bang for my buck?


Terry,
       In most cases, absolutely.  Too little information in your posting to 
know what you want the antenna for, but I presume a scanner (vice Ham, but not 
sure).

       Satelite dish 
is permitted (prohibitions preempted) by FCC's PRB-1, three feet diameter and 
under, for TV direct broadcasting (e.g., 3' limit, no C band dishes).  TV 
antennas are also covered to get local broadcast TV.  Antennas for other 
services, such as SW or scanners, or transmit antennas, or not included in the 
preemption.

       There are add-on conventional-TV antennas that look like a bent loop 
of tubing, that are designed to attach to the 3' dishes to allow local TV 
broadcaster reception.  Receiving antennas perform over very broad range, the 
proverbial "even a coat hanger will work."  Yes, you could "measure" their 
non-performance, but without the precision high-dollar gear to do it, your ear will be 
impressed by the improvement.  

       Remember, the Police and Fire transmitters have to ensure a signal to 
a handheld "buried in the mud."  Even a poor antenna up higher will get enough 
local signal to be heard.  Other-band antennas may not make the best DX 
antennas, but for local service, they should be fine.
       
       Virtually ANY conventional antenna higher up and in the clear will 
outperform any rubber duck on the scanner at ground level.  Most broadcast TV 
antennas are horizontally oriented and polarized.  Virtually all mobile 2-way 
radio services are vertically polarized.  The tubing-antenna for the Dish has 
portions in both polarizations, making it even better for dual-duty in the non-TV 
bands for your scanner.  

       If you think you could get away with building and mounting a vertical 
dipole to mount to the Dish, do so, and just tell people it is a "local, over 
the air, broadcast TV antenna permitted by PRB-1."  Just hook it up to your TV 
to prove it!  (Likewise, the vertical antenna will pick up some TV signals, 
too!)

       Best if you can run the lower-loss 300 ohm twin lead from the 
commercial made TV-add-on antenna down to the radio, then convert it to 75 ohms 
(standard $1 converter at the Dollar Store, and the $1 splitter there, too!) will do 
what you need to do to make it work.  However, 300 ohm twin lead takes 
special precautions, like keeping it away from metal (down spouts, pipes, wires, 
etc.).  If you can't do that, put the 300 ohm to 75 converter transformer at the 
antenna and run the 75 ohm coax down to the splitter.  Coax is not sensitive 
to any of the metal since it is shielded.  Radio Shack has several adapters for 
the TV standard "F" connector to connectors for your scanner.  Again, if 
anybody asks, just show them the connection to the TV!

       If you build your own vertical dipole (e.g., 19" each leg for VHF, 6" 
for UHF, and 3" each leg for 900 +/- MHz), just use the TV 75 ohm coax 
directly to the antenna.  Cable TV uses 75 ohm coax for the lower loss (how many 
10,000s miles of cable do they operate?) than 50 ohm coax, which handles more 
transmitter power for the available materials (determined in WW II to maximize the 
manufacturing with limited resources).  

       Even if not outside, one in the attic should still work better, IF 
your roof is not metal, or the insulation in the roof rafters isn't aluminum foil 
backed.  Insulation below the antenna (ceiling rafters) would be OK of any 
type for the radio.  For a scanner or Ham, keep the antennas vertical.

Arnal N9ACC