Antenna help in SoCal

[sdchris]

My analysis is: http://www.tvfool.com/?option=com_wr...a3626e4b7ff9a0

I'll tell you what I have and what I have tried. I currently have a 91xg above my chimmey and a db5 vhf about 4 ft below that on the same mast. Both of these antennas hook into a channel master 7777 preamp which feeds down to the tv area. I'm getting both vhf affiliates fairly reliably with some cut outs or loss of service every once in awhile. However, the UHF signals are either non-existent or spotty. I get the Fox affiliate 69-1 fairly reliably with some cutout here and there. The NBC affiliate 39-1 is very spotty. It will work for 20 seconds and then cutout for 20 seconds. I can't get the other UHF affiliates at this time. I realize that I'm at a long distance from the towers and I'm stuck in a valley.

Anyone have any suggestions? I was thinking about jacking up the antenna another 6 ft with hopes that it might work. Also, I'm sure the planes flying overhead (close airport) add the spotty reception on a few stations, but should there be a reason that I get some UHF, but not all, from the same transmitting location?

Thanks in advance,
Chris

[mtownsend]

Post moved to its own thread.

[mtownsend]

Hello and welcome!

Did you mean ClearStream5 for the VHF antenna?

Just a few thoughts:

1) Is the 7777 configured for "separate" VHF/UHF inputs, and do you have the antennas connected in appropriately?

2) You might want to use the tilt feature of the 91XG mounting bracket to aim the antenna up a little bit toward the sky. You seem to have tall mountainous obstruction close to you, so it may help to have the antenna aimed slightly above the mountain tops.

3) You may want to experiment a bit with the aim of the antenna. When faced with tall mountainous obstructions, the signal might be diffracting over many points along the ridge line. If you aim at different points along the ridge, you might find some spots that produce stronger signals than others.

4) Experiment with the Interactive Maps tool (here) and try a bunch of different antenna heights (also verify the accuracy of your location on the map). Try 20, 30, 40, and 50 feet to see how much things change. This will give you an idea of whether or not it makes sense to go for more antenna height. The benefit of antenna height mostly depends on how close you are to the nearest mountain obstruction.

5) The 91XG and 7777 are already a pretty good combination. If adjusting your antenna as per these suggestions is still not good enough, it would seem the next steps would be to either increase antenna gain (by ganging multiple antennas), switching to a pre-amp with a lower noise figure (like one from Kitztech), or both.

[ADTech]

Yeah, you're in a tough spot.

Keep in mind that you should have two separate pointing directions. The C5 (we don't have a db5) should be pointed about due south towards La Jolla for 8 & 10. The 91XG should be aimed about 30° eastward towards Mt Miguel.

Take advantage of the 91XG's tilt bracket and boresight down the boom. Adjust the front of the antenna "nose-up" so that boresight is aimed at your visual horizon on heading 139° magnetic. Remember 1) that the 91XG has an extremely narrow beamwidth and will need accurate aiming and 2) the terrain path on your line-of-sight is very rugged and may cause the signal to come in a bit "off" from the predicted path.

About the only thing that can easily be done with the 91XG is add an additional center section (makes it about 11' long!). This will tighten the beam width just a bit and sometimes helps in severe situations.

ADT

Edit: I'm slow and got interrupted.... lol

[sdchris]

Thanks mtownsend and adtech. I have the 7777 hooked up properly where both vhf and uhf are coming out. I had a problem at first and then realized I should read directions instead of being hard headed. My 91xg is tilted toward the horizon. It's possible that the high mountain is diffracting the signal. I'm going to try repositioning it this weekend and see what happens. I do have a C5 (not db5) and get reliable VHF. I think I'll leave that alone since it's working. I will work your suggestions thoroughly this weekend and update you with pictures and results.

Thanks for the input!

Chris