2-bay UHF antenna for VHF channel 7? - AVS Forum
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post #1 of 17 Old 07-11-2008, 07:41 AM - Thread Starter
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I am running a 2-bay bowtie antenna to get OTA DTV via a Insignia STB.
After the changeover, Detroit's Fox will change from digital channel 59 to channel 7, moving from high UHF to high VHF.

Do you guys know if my antenna is likely to be good enough, or will I have to wire in a properly tuned and oriented VHF antenna to get channel 7?
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post #2 of 17 Old 07-11-2008, 07:52 AM
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Do you receive any analog VHF-HI(7-13) channels presently ? that would be some indication.
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post #3 of 17 Old 07-11-2008, 08:01 AM - Thread Starter
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I do, but they aren't perfect... a little noisy.
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post #4 of 17 Old 07-11-2008, 08:04 AM
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The 2-bay bowtie might work if the digital VHF 7 signal is strong enough. But the gain for VHF 7 for a typical 2-bay bowtie is poor. The station is WJBK-DT Fox 2, currently on UHF 58, but switching to VHF 7 next year correct? Checking Falcon_77's spreadsheet (http://www.avsforum.com/avs-vb/showt...3#post12890633), WJBK-DT will be using a side-mounted temporary antenna for VHF 7 after 2/17/09 while a new top mounted antenna for VHF 7 is put on top of the tower (presumably in place of VHF 2 antenna). Station plans to be at full power by July 1, 2009, but in the interim period will have reduced coverage.

If you have an analog NTSC tuner hooked up, what does the analog picture for WXYZ-TV ABC 7 look like? Good or very noisy? How far are you from the broadcast tower for WJBK?
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post #5 of 17 Old 07-11-2008, 08:10 AM - Thread Starter
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I am about 6 miles from the tower. My analog channel 7 reception is watchable, but a little noisy.
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post #6 of 17 Old 07-11-2008, 08:31 AM
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Since you are so close to the towers a VHF antenna might even provide too strong a digital signal at cutover and your digtial tuner will be overloaded and receive nothing,
I suggest that you wait till the cutover and then see if you have any problems.
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post #7 of 17 Old 07-11-2008, 11:22 AM
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Not sure if this is helpful, but our local ABC affiliate has been on VHF channel 7 since they started testing about four years ago. As the only VHF DTV station in our area, it's the weakest signal I get (70%-80%), but only rarely do I have any problems with it.

I'm using a Channel Master UHF 8-bay bowtie antenna from about 45 miles away. They are not running at full power and have recently applied to raise their transmitter and begin putting out a stronger signal. Their analog signal is Channel 5 and I couldn't receive it at all.

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post #8 of 17 Old 07-11-2008, 11:33 AM
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Quote:
Originally Posted by walford View Post

Since you are so close to the towers a VHF antenna might even provide too strong a digital signal at cutover and your digtial tuner will be overloaded and receive nothing, ...

Eh? An antenna with a pre-amp might overload, but a medium or short range VHF antenna by itself will be fine at 6 miles.

blood_donor, if you are willing to take a chance to go without the Fox station for several days after the changeover next February, you can leave your setup alone and see what happens. If you don't get reliable reception for WJBK-DT, then you can add a pair of rabbit ears, maybe clipped (through a non-conducting attachment) to the top of the bowtie reflector plate and a VHF/UHF combiner. Or go ahead and do it now. Won't cost that much. The rabbit ears only need to be extended to around 34" long for upper VHF 7 reception.
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post #9 of 17 Old 07-11-2008, 12:11 PM
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I was only trying to point out that digital tuners can get overloaded whereas analog tuners can not.

http://www.tvtechnology.com/pages/s.0072/t.7434.html
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post #10 of 17 Old 07-11-2008, 12:37 PM
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Quote:
Originally Posted by walford View Post

...digital tuners can get overloaded whereas analog tuners can not.

http://www.tvtechnology.com/pages/s.0072/t.7434.html

When I connect an analog TV directly to the output of a high powered strip amplifier (typically, 56 to 66dBmV adjustable output range), something definitely gets overloaded.
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post #11 of 17 Old 07-11-2008, 04:29 PM
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I too have a bow tie, 35 miles out and in an area where two stations 7 & 9 will revert to their analog frequencies. I plan on waiting till next year to see if I need to do anything. I strongly suspect I won't as the antenna already picks up the current 7 & 9 with NTSC signal strength at a 100% level. It too is noisy due to refections but If I can get the analog VHF signal already at 100% I don't foresee a problem receiving digital VHF @ 100%. I suspect the noise will disappear as none of the digital stations it receives now show any issues.
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post #12 of 17 Old 07-11-2008, 08:39 PM
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Quote:
Originally Posted by ultimate View Post

Not sure if this is helpful, but our local ABC affiliate has been on VHF channel 7 since they started testing about four years ago. As the only VHF DTV station in our area, it's the weakest signal I get (70%-80%), but only rarely do I have any problems with it.

I'm using a Channel Master UHF 8-bay bowtie antenna from about 45 miles away. They are not running at full power and have recently applied to raise their transmitter and begin putting out a stronger signal. Their analog signal is Channel 5 and I couldn't receive it at all.

Dennis

That CM 4228 is the only UHF antenna that gets semi-decent high-band VHF because of the way the bays are connected.
A high-band VHF antenna or one of the new UHF/high VHF antenna is needed.
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post #13 of 17 Old 07-11-2008, 08:56 PM
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Quote:
Originally Posted by SkiSmuggs View Post

That CM 4228 is the only UHF antenna that gets semi-decent high-band VHF because of the way the bays are connected.
A high-band VHF antenna or one of the new UHF/high VHF antenna is needed.

You say a UHF/High VHF antenna is needed. If you are already receiving an analog signal of 70 to 80% with an exsisting antenna why wouldn't it still pick up the digital signal in a 70 to 80% range unless the station drops power levels at changeover. Since a coat hanger can be used to pickup signals you don't always have to have a highly specialized antenna if the signal is strong.
Granted a high VHF antenna will have a higher gain in that freq range but if you can receive the signal on any type of antenna with a suitable signal level the type of antenna becomes mute. If you know something I don't please explain.
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post #14 of 17 Old 07-11-2008, 11:07 PM
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I agree with pkeegan. One post stated "6 miles really is not considered close". I'm no antenna expert (but I have built antennas) and 6 miles is pretty damn close by my standards. Last time I was in Detroit, I recollect it being pretty flat. I have a homemade UHF yagi with a CM amp that pulls in digital RF 11, 16 kW ERP, from 71 miles away. It's LOS, but it's not 6 miles away either.

I agree with the other post about attaching a rabbit ear dipole to the UHF antenna. Rabbit ears should be more than sufficient at 6 miles. A coat hanger probably would be.

Just my 2 cents.
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post #15 of 17 Old 07-12-2008, 12:57 AM
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Get a uhf/vhf combiner and add set top rabbit ears....or "mount" the rabbit ears elsewhere.

I kill for 6 miles to the tower. Its not too close and its definitely not far away.

The Channel Master 4000 is a good pair, or the Terk TV-1.

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post #16 of 17 Old 07-13-2008, 06:39 AM
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Quote:
Originally Posted by blood_donor View Post

I am running a 2-bay bowtie antenna to get OTA DTV via a Insignia STB.
After the changeover, Detroit's Fox will change from digital channel 59 to channel 7, moving from high UHF to high VHF.

Do you guys know if my antenna is likely to be good enough, or will I have to wire in a properly tuned and oriented VHF antenna to get channel 7?

Your present antenna will likely work. If not, move up to a 4bay, which at only 6 mi should work for VHF 7.

I would wait and see.
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post #17 of 17 Old 07-13-2008, 06:43 PM
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Quote:
Originally Posted by Rick0725 View Post

Why would you want to move up to a 4 bay uhf for VHF hi ???

Because I've seen it work at that distance for channel 7. Why use something complicated when something simple will work?
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