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Old 27-Sep-2015, 4:14 PM   #1
fusionteck
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Antenna spread

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How far should the spread distance be between the UHF and VHF antenna?
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Old 27-Sep-2015, 4:25 PM   #2
ADTech
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Depends on the antennas.
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Old 27-Sep-2015, 5:29 PM   #3
fusionteck
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Winegard YA 1713 and a 91XG
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Old 27-Sep-2015, 6:48 PM   #4
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4 feet if possible, although at 1 foot separation I haven't noticed any signal degredation between the 91XG/YA-1713. YMMV
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Old 27-Sep-2015, 8:44 PM   #5
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The rule of thumb is to have a separation equal to at least 1/2 wavelength of the lowest frequency channel of the VHF antenna.

Channel 7 is 174 to 180 MHz.
5540/174 = 31.8 inches

http://www.tvantenna.com/support/tut...combining.html

I think you should be more concerned about Chromstar UHF preamp overload from strong local TV and FM signals than antenna spacing.

http://www.tvfool.com/?option=com_wr...8e03cccd493fef
Attached Images
File Type: jpg Antenna Spacing.JPG (136.1 KB, 131 views)
File Type: jpg fusionteckHDF FM.JPG (108.3 KB, 125 views)
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Last edited by rabbit73; 27-Sep-2015 at 10:20 PM.
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Old 28-Sep-2015, 2:23 AM   #6
fusionteck
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Quote:
Originally Posted by rabbit73 View Post
The rule of thumb is to have a separation equal to at least 1/2 wavelength of the lowest frequency channel of the VHF antenna.

Channel 7 is 174 to 180 MHz.
5540/174 = 31.8 inches

http://www.tvantenna.com/support/tut...combining.html

I think you should be more concerned about Chromstar UHF preamp overload from strong local TV and FM signals than antenna spacing.

http://www.tvfool.com/?option=com_wr...8e03cccd493fef
Rabbit
Thanks again I appreciate and learn from everything you mentor me on, With that said I have removed the chromstar and put up a 777 I am a little confused on your concern on the chrome star as it is only a UHF preamp and my two closes stations 13 which is 3 miles away and is VHF but it doesn't overload it sits at about 91 Now the station next to it which is UHF 20.1.2.3.4.5 it doesn't over load either sits at about 91
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Old 28-Sep-2015, 2:36 AM   #7
rabbit73
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It is possible to have partial overload that doesn't show on the strong signals, but will damage the weakest signals.

Which is what I tried to show you here:



Half of the channels (the weak ones) are gone; the damage comes up from the bottom which is why the weak signals are damaged first, leaving the strongest ones OK:



The 7777 will also overload easily, according to Channel Master:

http://www.channelmaster.com/TV_Ante..._p/cm-7777.htm
Quote:
The Titan 2 High Gain Preamplifier will amplify signals received by your antenna. This antenna amplifier is a high gain, low noise preamplifier used to allow weaker signals at the antenna to be amplified to a viewable strength, and is ideal for installations in which all broadcast towers are located at a distance of more than 80 miles.

The Titan 2 High Gain Preamplifier is recommended for professional installers only. Due to the high gain output of this product, it can result in over amplification if not used in the appropriate scenario. Over amplification can cause issues with the television tuner’s ability to receive and display some or all channels.
which is why Tower Guy and ADTech both told you to use a preamp that is resistant to overload.
Quote:
Originally Posted by ADTech View Post
I'd also dump the Winegard amp and replace it with something with a lower noise figure and superior overload resistance. If we had our Juice available, that would be the suggested amp. However, since it's out of stock for a while, my second choice would be to re-purpose an Electroline EDA2100 distribution amp in a mast-mounted, remote powered configuration. It has a very good noise figure and you won't overload it. As a matter of fact, I'd probably do that first.
Quote:
Originally Posted by Tower Guy View Post
Yet the two super strong VHF stations could overload that amp it if the VHF/UHF filtering in the 4800 is inadequate. KYFQ FM 91.7 is also extremely strong at roughly -22 dbm at your location. Again the filtering of the amp should minimize that, as should the smart way that you've combined the VHF antenna after the UHF preamp.

To rule out a problem from VHF or FM, try just the 91XG and the preamp and see if KIRO comes back. If so, you are chasing down interference which is likely caused by overload. If not, trees may have grown in front of your antenna. You can search for a location that has fewer trees.
and why I suggested this:
Quote:
Originally Posted by rabbit73 View Post
In order to keep the strong VHF and FM signals out of the preamp and tuner, I suggest you try this:
Code:
 91XG > UVSJ > AP4800 > 
                       \
                       AD EU385 > coax > power inserter > TV
                       /
YA1713 Yagi > FM trap >
The second UVSJ between the 91XG and the preamp attenuates the FM and VHF signals, but allows the UHF signals to pass through. FMFOOL report in attachment 4.
http://www.mcmelectronics.com/produc...-FM-88-/33-341
https://www.antennasdirect.com/store...on_filter.html

If KTBW is too strong for the preamp, switch to a preamp that resists overload better, as ADTech and Tower Guy suggested. ADTech did some preamp tests in a strong signal area that show the Winegard Chromstar UHF preamp overloads easily which harms the weak signals.
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Last edited by rabbit73; 28-Sep-2015 at 3:08 AM.
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