TV Fool  

Go Back   TV Fool > Over The Air Services > Special Topics > Antennas

Notices

Reply
 
Thread Tools
Old 8-May-2015, 4:38 PM   #1
user name
Junior Member
 
Join Date: Apr 2015
Posts: 24
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?
user name is offline   Reply With Quote
Old 8-May-2015, 4:48 PM   #2
GroundUrMast
Moderator
 
GroundUrMast's Avatar
 
Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,773
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.
__________________
If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

(Please direct account activation inquiries to 'admin')
GroundUrMast is offline   Reply With Quote
Old 8-May-2015, 6:50 PM   #3
stvcmty
Senior Member
 
Join Date: Mar 2013
Posts: 135
Quote:
Originally Posted by user name View Post
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.
stvcmty is offline   Reply With Quote
Old 9-May-2015, 4:14 PM   #4
dbseeker
Member
 
Join Date: Apr 2014
Posts: 36
GroundURMast

Can I assume your comment applies to the Channelmaster 4221 and 4228 models?
dbseeker is offline   Reply With Quote
Old 10-May-2015, 4:26 PM   #5
GroundUrMast
Moderator
 
GroundUrMast's Avatar
 
Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,773
The CM-4228 and Antennas Direct CS5 are examples of single band designs that proved to have some useful performance in another band.
__________________
If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

(Please direct account activation inquiries to 'admin')
GroundUrMast is offline   Reply With Quote
Reply

Bookmarks

Go Back   TV Fool > Over The Air Services > Special Topics > Antennas


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off




All times are GMT. The time now is 7:24 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © TV Fool, LLC