Combiner problem

[somerset]

Hello everyone:
I know that combining two antennas is very hit or miss, but I want to see if anyone out there can help me out. Here is my TV Fool report:
http://www.tvfool.com/?option=com_wr...46aee20119ca6d
I currently have an 8 bay bowtie pointed NW towards Pittsburgh, and a 4 bay bowtie pointed NE towards Altoona, PA . Both have a Channel Master 7778 preamp, and run 75’ to a Channel Master DVR+. One antenna is mounted on the front of the house and the other is mounted on the side of the house, I think that the only channels picked up by both antennas are WJAC, WPCW and WWCP.
When either antenna is hooked up separately, most channels have a good signal (close to 100% strength and 100% quality). When I combine the antennas, the signal drops a little bit on some channels but the signal quality on WATM and WTAJ drops down to 0% (with 100% signal strength).
Does anybody have any tips or trick that I can try to pick up WATM and WTAJ?
These are the channels that I can pull in:
WWCP
WJAC
WTAJ
WQED
KDKA
WPXI
WPMY
WPGH
WINP
WPCB
WTOV
WPSU
WBGN
WNNB

[ADTech]

Here's your *best* solution that is guaranteed to work (you probably won't like it).

Buy a second DVR and have one DVR per antenna. Eliminates all the mess that you're experiencing. Probably cheaper than commissioning a custom filter/combiner.

[rickbb]

When I tried to get a custom filter/combiner, I was told politely that I couldn't afford one. They mostly work if you only want filter one or two channels from the 2nd antenna.

If you want to play around and have a bit of technical know how, browse over to www.hdtvprimer.com and look for combining antennas, tuning the aiming of them to take advantage of nulls and such.

It's still hit or miss though. But very interesting reading.

[eggman531916]

Not 100% sure, but I think you need to identical antennas with identical lengths of coax running from each antenna to the splitter/combiner (i.e. 10' from each antenna).

[somerset]

Since the two channels that "drop out" aren't being picked up by the other antenna, do I still need the identical setups?

[eggman531916]

Originally Posted by somerset

Since the two channels that "drop out" aren't being picked up by the other antenna, do I still need the identical setups?

As far as I know, the answer is yes. I don't have anywhere near the experience as some of these other guys do so if someone wants to chime in and correct me, that would be good. But I believe I've read somewhere that it's best to have two identical antennas for UHF if they're connecting into the same feed. Since they're not facing the same direction, they need to be separated by at least 3' with the identical lengths of coax from each antenna to the combiner. Of course, you could run a feed line from each antenna into an A/B switch and just switch back and forth between the antennas, but if you're like me, you won't want to do that.

[nikopow]

I am looking into a similar issue. I talked to Winegard's support team. They recommended two of the same antenna models spaced no closer than 2-1/2 to 3'' from each other. Make sure the coax from each antenna is approximately the same length to the combiner like their Winegard C-7870, which is built for two antennas. Power one antenna and make the 2nd one passive. No guarantees the set up will work but, they have a 90 day return policy and if you call tech support they will give you good advice. If this doesn't work there is always a rotor.

[rabbit73]

If you have two identical antennas, aimed in the same direction, and are using a splitter reversed as a combiner, the coax lines must be the same length for maximum gain. You will be able to get up to 2.5 dB more, 3 dB because of doubling the signal minus the 0.5 dB internal loss of the combiner.

When the antennas are aimed in the same direction, the incoming wave front arrives at both antennas at the same time (when perpendicular), and the signals arrive at the combiner at the same time, so they add in phase.

This only works if the wave front is uniform across both antennas. If the wave front is not uniform across both antennas (like thru trees), you don't get the gain you expected. This explains why a 4-bay bowtie antenna sometimes works better than an 8-bay bowtie, like 4221 VS a 4228, because it has a smaller capture area.

If the two antennas are not aimed in the same direction, the incoming signals do not reach each antenna at the same time, so it is not necessary to have the coax lines the same length, because the same signals aren't going to arrive at the combiner at the same time anyway. Sometimes it works, sometimes not.

It is possible to adjust the lengths of the coax lines to different lengths so that one desired signal from both antennas arrives at the combiner in phase, but that often harms the other signals that might have been OK before adjusting the lengths.

[nikopow]

Than you for the clarification.

The title says it all. I have invested time and money to get an OTA system working. I have 7 remotes for Blu-Ray, Amp, 2 for TV plus keyboard, harmony One, VCR, Apple TV and Channel Master. I am reluctant to add another antenna to enhance the present setup. I think I will settle for the 6 channels I receive for the time being. Perhaps in the Winter when the reception drops I'll invest some more T & M.