TV Fool

TV Fool (http://forum.tvfool.com/index.php)
-   Antennas (http://forum.tvfool.com/forumdisplay.php?f=10)
-   -   Can a rotated 10 foot long (UHF only) antenna ........ (http://forum.tvfool.com/showthread.php?t=15542)

user name 8-May-2015 4:38 PM

Can a rotated 10 foot long (UHF only) antenna ........
 
I rotated a 10 foot long UHF antenna 90 degrees and tried to use it as a VHF antenna but did not succeed.

Can a rotated 10 foot long (UHF only) antenna receive a VHF signal?

GroundUrMast 8-May-2015 4:48 PM

There are a few UHF only designs that happen to have some useful VHF capability and vise versa. However, if you really need VHF performance, you need to use an antenna that was intentionally designed for that frequency range.

The problem I've observed when receiving VHF through a UHF only antenna is the signal quality (not to be confused with signal strength). Two factors appear to play a major role in this, widely variable frequency response outside the designed operating frequency range of the antenna, and unacceptably high VSWR (voltage standing wave ratio). Both factors are closely related and contribute to the signal being distorted before it is delivered to the tuner.

stvcmty 8-May-2015 6:50 PM

Quote:

Originally Posted by user name (Post 51056)
I rotated a 10 foot long UHF antenna 90 degrees and tried to use it as a VHF antenna but did not succeed.

Can a rotated 10 foot long (UHF only) antenna receive a VHF signal?

If I understand your question, you are asking: “If I try to use my antenna as a 10’ dipole, why didn’t it work?”


A 10’ dipole would be resonant at 46 to 49MHz, depending on velocity factor. TV channels don’t start until 54MHz, and there is not much full power DTV on channels 2-6, so the frequency that matters is 174MHz for channel 7 up to 216MHz for channel 13. A dipole resonant at 49MHz is not going to do much for channels 7 to 13.

The boom for your UHF antenna is most likely electrically bonded to ground through your mast. So for a sideways UHF antenna boom to act as a dipole antenna, the UHF antenna would need to be electrically floating relative to the mast, and it would need to have an insulator half way along its length. Then a wire could be attached to each side of the insulator and there would be a dipole in the boom.

dbseeker 9-May-2015 4:14 PM

GroundURMast

Can I assume your comment applies to the Channelmaster 4221 and 4228 models?

GroundUrMast 10-May-2015 4:26 PM

The CM-4228 and Antennas Direct CS5 are examples of single band designs that proved to have some useful performance in another band.


All times are GMT. The time now is 7:13 AM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright © TV Fool, LLC