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Discussion Starter · #1 ·
Since this post asks about UHF verus VHF antennas I will post it here also


I installed a ChannelMaster 4221 on a 10 foot pole in my garden above a retaining wall and turned it in the direction of 320 degrees. I am getting NBC, ABC and even CBS which is at 5 degrees. I am unable to get PBS which is 318 degrees at only 8 miles from my house though I am getting TBN at 318 degrees the same distance. The only difference is that PBS is VFH and the TBN is UHF. The UNC PBS in UHF comes in even though it is 45 miles away. Is the 4221 so selective an UHF antenna that it unable to receive a close VHF signals? Are there people I Greenville area who are using this antenna and are able to receive the VHF PBS signals?


It will be difficult to put a combo UHF/VHF antenna that can receive all because of the size of the antenna needed to get the distant UHF signals. Should I place a second VHF antenna and combine the signals?


On another note, I can easily attach a coper wire to the house ground but am unable to attach the same 6 gauge wire to the mast. How do people attach a ground to a ¾ or 1†mast pipe?


Thanks for all your help
 

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What channel on VHF? The 4221 "can" pull in 12-13 in the right conditions.
 

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The 4221 is a UHF only antenna. It can sometimes get the upper VHF channels (ch 7 - ch 13) depending on how far away the station is, what power they transmit at, and how their transmit antenna is orientated. If a 4221 works for you on everything else, then a CM5646 or a Winegard HD7210 may be a better choice of an antenna. Both of those antennas are both VHF & UHF capable and work well up to 30 miles when roof (pole) mounted.


Go to your local hardware store and look for a grounding clamp for a ground rod. I have attached a .GIF that shows what one looks like. Typically, they can handle up to 1" galvanized pipe and will accept 6 ga wire.


Bob Chase

KHWB-TV
 

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Mast grounding requires only 10 gauge copper, 8 gauge aluminum or 17 gauge copper clad steel wire. I wouldn't bother with the aluminum, because it might react to one of your clamps, but you can obtain the 10 gauge copper cheaply. Most home improvement centers don't stock 10 gauge copper solid but do have stranded 10 gauge copper available for cutting to specified length.


There is a gap in the broadcast spectrum between VHF channel 13 and UHF channel 14 that is large enough for over forty channels, so the fact that an antenna "tuned" to receive channels 14-69 doesn't receive channels 13 and below well does not mean that it is tightly tuned, but rather, that channel 13 and below need a fundamentally diifferent antenna for optimal reception.
 

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If you are "close enough" to a high power VHF or UHF station, even a coat hanger (see slide 11) might work:
https://secure.connect.pbs.org/confe...ns/TC05_43.htm


Kerry Cozad also included VHF measurements for several other UHF antennas (but not a 4-Bay).

The fol has an expanded scale so you can actually see the results:
http://hdtv.forsandiego.com/messages...tml?1118216319


NEC simulation results for the 4-Bay CM-4221 (and others) can be found here:
http://www.hdtvprimer.com/ANTENNAS/comparing.html

The CM4221 was worst than rabbit ears on CH11 and below....

But maybe you don't need much antenna gain to begin with....
 

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Discussion Starter · #7 ·
Thanks to everyone for their input. I tried an indoor rabbit antenna for the VHF signals but the local PBS station did not tune in. I may have to get Channel Master VHF antenna. I will get the grounding block for the mast from the local hardware store as Bob Chase recommended.
 
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