[Subscribe to Daily Digest] |
Members do not see ads below this line. - Help Keep This Site Online - Signup
I am mounting a 1/2 wave FM dipole to overcome FM reception problems in our house. I have a custom notch filer for the local FM station and a FM specific amp/splitter. Without the notch filter, a strong signal going through a amp stage cab cause clipping and signal to noise ratio can be degraded.
FM antenna's were originally set up for horizontal polarization as were the VHF TV channels. When FM radios started to appear in automobiles with vertical whip antennas there was a problem as the polarization was very wrong. The answer would have been to broadcast with a vertical polarization, bun then legacy antennas would not work, including TV VHF antennas as FM antennas. So the FCC mandated circular polarization or 45degree polarization as a compromise. [The FM band is between the old VHF channels 6 and 7.]
I connected the filter, amp and antenna to a receiver and rotated the antenna at different angles. Sure enough, most FM station signals were better at 45 degrees. So take that in mind when placing the FM wire antennas that come with tuners etc. Any directional FM antennas may also work better rotated to 45 degrees.
I found one station that was 30 degree off vertical. That station's antenna is located part way up a mast that supports other radio stations. The mast might be rotating the effective polarization from the expected 45 degrees.
I was wanting my antenna mounted vertically to keep birds off and better ability to carry ice loads. So now its going to be 45 degrees and that will look odd. Most pictures of FM antenna's for FM broadcast recieving show vertical or horizontal mounting; which would be a mistake for any weak distant signals.
A horizontal dipole is a directional antenna. A vertical antenna is omnidirectional. At 45 degrees, it will be a little of both.
[FM base station antennas for commercial use are vertical as are the receiving units.]
posted by 108.207.11...
, Fri, 3 Jan 2014 12:21:28
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
