Losing reception at night

dprljackson · 11-Jul-2011, 3:03 PM

Hi all,

I'm a relative newbie when it comes to antennas. I'd like some help trying to reliably receive FOX. Here is my TV Fool report:
http://www.tvfool.com/?option=com_wr...03d9ab235afa3f

I've been using an HBU33 in the attic with a 7777 pre-amp and I have never really been able to receive channels 8.1 and 43.1. On a very rare occasion, they would come in for brief periods of time.

Anyway, I finally bit the bullet and mounted this antenna to the roof and low-and-behold, I got both channels. Unfortunately, it didn't really last. While channel 8 comes in reliably, channel 43 only comes in sporadically. In particular, it seems to come in very reliably at night and in the morning but it is hardly ever available during the day.

I'm guessing there's not much I can do except get a larger antenna. If this is the case, I'm open to recommendations. I really want to keep the antenna as small as possible. Would a Winegard HD-7696P improve the situation much or would I still have the same problem?

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ADTech · 11-Jul-2011, 5:14 PM

Please note that your problem channels both come from a different direction, are further away, and are slightly obscured by terrain. You didn't mention what your aiming direction for the existing antenna is, but I suspect it may be misaimed for those two channels while benefiting the other ones.

You might try an aiming direction that attempts to split the difference with a bit of favoring towards the ESE and see if you can make all the signals happy. With about a 50° spread, it will become more difficult, especially when dealing with a compromised signal path due to terrain. Moving to a "longer" range antenna as you proposed will make it more directional and will aggravate reception from spread-out transmitters unless you add a rotor to physically aim the antenna in the most effective direction.

The alternative may be a pair of broad-beam antennas that can attempt to focus enough signal from the disparate directions to work without resortng to a rotor.

Do first try aiming the existing antenna directly to the ESE first to see if can pick up those two difficult stations without loosing the "easy" ones.

John Candle · 11-Jul-2011, 7:30 PM

Read and understand about , REAL Digital Broadcast Tv Channels , Virtual Digital Broadcast Tv Channels , Analog Broadcast Tv Channels , http://forum.tvfool.com/showthread.php?t=695. I suggest aim the antenna at about 94 degree magnetic compass. And then turn the antenna to the left and right to find a sweet spot that might receive the stations in the wide spread of 41 to 120 degree magnetic compass , thats a spread of 79 degree and thats really wide for a directional antenna to receive. The end of the antenna that has the short cross bars is what is aimed at the transmitters. If this does not work then I have another suggestion.

dprljackson · 12-Jul-2011, 11:42 AM

Thanks for the responses. Sorry I wasn't more clear in my original post. The antenna I have (HUB33) is currently aimed more-or-less in the direction of the problem stations. That is, it is currently aimed at ~120 degrees. I still pick up all the other channels just fine and channel 8 is fine. Channel 43 is the only one that is not perfect, although it's fine at night. It sometimes comes in during the daytime but is not really watchable as it goes out a lot or doesn't come in at all.

So a larger antenna will have a narrower beam width which might improve the reception for 43 but make worse the reception for the other channels, is that correct? Looks like the Winegard has a beam width of somewhere around 50 degrees for most of the channels and a gain of about 2-3 dB more than the HBU33. Is that enough of an improvement to pick up this channel? And would I lose the others in the process?

Or, as was alluded to, is there something else (even easier, I hope) that I can try?

Tower Guy · 12-Jul-2011, 1:48 PM

Quote:

Originally Posted by dprljackson

Or, as was alluded to, is there something else (even easier, I hope) that I can try?

You could try raising or lowering the antenna a few feet to see if you can find a "hot spot".

This is good background information.
http://www.hdtvprimer.com/ANTENNAS/siting.html

Dave Loudin · 12-Jul-2011, 4:57 PM

Quote:

Originally Posted by dprljackson

a larger antenna will have a narrower beam width which might improve the reception for 43 but make worse the reception for the other channels, is that correct? Looks like the Winegard has a beam width of somewhere around 50 degrees for most of the channels and a gain of about 2-3 dB more than the HBU33. Is that enough of an improvement to pick up this channel? And would I lose the others in the process?

It only will make for worse reception if you are trying to use a fixed antenna. Antenna gain figures are for the peak gain in the center of the beamwidth only. Quoted beam widths are typically the range of angles where the antenna gain is within 6 dB of the peak gain. Beyond the quoted beamwidth, gain starts to fall off rapidly.

ADTech · 12-Jul-2011, 6:22 PM

Beamwidth is defined at the "half-power" points, that is, -3 dB from the peak.

As an example, the ClearStream 1 & 2 antennas from our lineup have a nearly uniform beamwidth of 70°; 35° on either side of boresight where the gain is down 3 dB from the peak. Our 91XG, OTOH, has a beamwidth of only 24° at channel 51.

dprljackson · 13-Jul-2011, 1:17 PM

Quote:

Originally Posted by Dave Loudin

It only will make for worse reception if you are trying to use a fixed antenna. Antenna gain figures are for the peak gain in the center of the beamwidth only. Quoted beam widths are typically the range of angles where the antenna gain is within 6 dB of the peak gain. Beyond the quoted beamwidth, gain starts to fall off rapidly.

Can you please clarify? Increasing the gain should improve reception in the center of the beamwidth, correct? The cost would be decreased reception for the other channels that currently come in just fine. So the question seems to be whether I can increase the gain enough along the center of the beamwidth to pick up 43 while not losing everything else. And that sounds like a trial and error situation to me (which I don't like the sound of).

I think I'll try moving it up and down to see if there is a hot spot.

Dave Loudin · 15-Jul-2011, 1:24 AM

Increasing gain does mean more sensitivity in the center. This comes at the expense of sensitivity in other directions. It's like squeezing a balloon.

Your summary of the question is exactly the point I was trying to make. You have all the data you need in your TVFool report to estimate the impact of narrower beamwidths (NM vs. azimuth.) Not nearly the trial-and-error you might think.

dprljackson · 15-Jul-2011, 12:58 PM

Quote:

Originally Posted by Dave Loudin

Increasing gain does mean more sensitivity in the center. This comes at the expense of sensitivity in other directions. It's like squeezing a balloon.

Your summary of the question is exactly the point I was trying to make. You have all the data you need in your TVFool report to estimate the impact of narrower beamwidths (NM vs. azimuth.) Not nearly the trial-and-error you might think.

The reason it seems like trial and error to me is that I don't know how to compare the HBU33 that I'm using with the HD-7696P that *seems* like it would be better. Here's my reasoning:

The HBU33 says it has a gain of around 7.7 for the UHF band and 7.6 for VHF high. It doesn't break it down by frequency. The beamwidth is around 55 degrees. The HD-7696P has a gain of 10.8 near channel 43 with a similar beamwidth (although it's a bit smaller, around 40 degrees, near channel 43). So it *seems* like the HD-7696P would give me about a 3dB improvement over what I have now since the antenna is already pointing at channel 43. According to my TVFool report, the difference between channel 8, which I get fine, and channel 43, which I get sometimes, is approximately 6dB. Since I am getting channel 8 fine, I assume I am less than 6dB from getting channel 43. But am I 5dB from getting it or 1dB from getting it? I can't tell. If changing the antenna gives me a 3dB improvement, it still seems like a shot in the dark to me.

Does that analysis make sense or am I missing something?

John Candle · 17-Jul-2011, 9:14 PM

dprljackson also has another post , go there for more information and answers.