Antenna for Island in WA

[beflyguy]

I have learned a lot here and just got my account verified. I would like to get a recommendation for an antenna setup. Currently I have a Radio Shack directional antenna as below on a ground mast 20ft high and a CM-7777 mounted just below the antenna. The major problem is a number of large fir trees all around the area. Most of those north-northeast are 200-400 yards away on a hill about 20-40ft higher than my location. Presently I get many of the channels I want up to 33 but the reception is very spotty. Some days everything comes in decently, some days very little comes in without breaking up sporadically. Rotating the antenna 30 deg between north and northeast helps a bit for individual channels. I plan on mounting an antenna permanently on the roof as soon as I settle on the right one and my height will increase about 20ft. I would rather not use a rotator if possible.

Here is my map.

I very much appreciate any help.

[rabbit73]

Welcome, beflyguy:

The 7777 preamp is easily overloaded by strong signals.
http://www.channelmaster.com/TV_Ante..._p/cm-7777.htm

KCPQ -37.5 dBm
7777 Max input level 15 dBmV = -34 dBmV
-37.5 dBm + 12 dB antenna gain = -25.5 dBm, overload

The 7778 would have been a better choice:
http://www.channelmaster.com/TV_Ante..._p/cm-7778.htm

7778 Max input level 34 dBmV = -15 dBm, OK
-25.5 dBm + 16 preamp gain = -9.5 dBm, just below tuner overload

Try your antenna without a preamp.

The antenna you selected is a high gain antenna which means that it has a narrow beamwidth, making it more difficult to aim; that's the tradeoff.

Trees are a problem for TV signals. Maybe there will be enough signal to get over them to be useful.
http://forum.tvfool.com/attachment.p...0&d=1448314548

If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.

[beflyguy]

Rabbit73,

Hi and thanks for the help. I thought I was far enough away from all the transmitters that overloading would not be a problem but maybe you can tell from my signal analysis if this is correct. I did actually try without an amp and I received very little.

I don't know if this is a proper test but if I unplug the booster power now, I get no channels at all. Maybe I would have to take the amp out of the circuit to test properly?

Is there a way to tell the difference between a weak signal and an overload problem?

It seems like most of the lower channels are in the same direction other than 13 which is powerful enough to come in off angle. Do you think this is correct?

Would it help to angle the antenna over the trees?

Thanks again

Brian

[ADTech]

I don't know if this is a proper test but if I unplug the booster power now, I get no channels at all.

It is not.

Maybe I would have to take the amp out of the circuit to test properly?

That is mandatory for a valid test.

Is there a way to tell the difference between a weak signal and an overload problem?

It depends what tools you have at your disposal.