# Question: Can OTA Multipath Rejection be Improved?



## zephyr (Jun 25, 2005)

Can multipath interference rejection in the 942 be improved, particularly in a future software upgrade? Comparing it side-by-side with a Sony tuner, the 942 does a poor job of locking onto poor or below normal signal quality (signal stength mid-80's). Both the Sony and a previous Zenith were able to lock in on signals that the 942 cannot. Same antenna, cabling, etc. 

Have tried antenna amp, attenuator, checking on AVS local HD forums, searching this forum, etc. Would hate to get rid of a perfectly good piece of equipment because it can't get the US Open tennis match.

Is this a software-fixable issue, or is it basic to the hardware?

Thanks.


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## Mark Lamutt (Mar 24, 2002)

There are some software settings that can be tweaked to make the tuner more or less sensitive.


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## zephyr (Jun 25, 2005)

Issue may not be multipath, as I studied the analog picture quality. Analog and digital are on adjacent channels, so analog is a good indicator of antenna and reception quality. It may be sensitivity or some other kind of interference rejection.

Mark, are they planning to work on this?

For me the issue is channel 3.1 (broadcasts on 2), WWMT, Grand Rapids, MI market.

By contrast, HD satellite image quality is fantastic!


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## Mark Lamutt (Mar 24, 2002)

They are working on it in every release. But, with OTA, what may help some people won't make any difference at all for others.


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## GateTraveler (Aug 27, 2005)

Mid-80s is poor for OTA?? That is a number I always thought was good. On my 811, I don't have problems until the signal strength goes into the 60's. 

The 942, on the other hand, won't lock on one of my channels that is in the 70s (yet it locks on other weaker channels). It also consistently locks on my Fox station but won't add it to the guide even though I get nothing but green on the channel (no drop outs, consistent 80s signal). This is very frustrating considering the fact that my 811 has had no problems with any of my OTA stations.

When will the next updated software be released? I'm hoping for a fix since advanced tech support has had me buy all kinds of stuff from Radio Shack and it still isn't working.


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## zephyr (Jun 25, 2005)

GateTraveler said:


> Mid-80s is poor for OTA?? That is a number I always thought was good. On my 811, I don't have problems until the signal strength goes into the 60's.
> 
> The 942, on the other hand, won't lock on one of my channels that is in the 70s (yet it locks on other weaker channels). It also consistently locks on my Fox station but won't add it to the guide even though I get nothing but green on the channel (no drop outs, consistent 80s signal). This is very frustrating considering the fact that my 811 has had no problems with any of my OTA stations.
> 
> When will the next updated software be released? I'm hoping for a fix since advanced tech support has had me buy all kinds of stuff from Radio Shack and it still isn't working.


The Sony receiver indicates both signal strength and signal quality. The 942 requires signal quality of 'good' to lock. Signal strength can be from the 70's (even lower) on up. In other words the 942 OTA receiver is not 'hot' to quote a professional antenna installer. It needs a pure signal.

I have a bag full of returns for Radio Shack, none of which did any good.

Am going to give one last try with a high quality antenna pre-amp tomorrow.


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## Bichon (Jun 5, 2003)

Mark Lamutt said:


> They are working on it in every release. But, with OTA, what may help some people won't make any difference at all for others.


And sometimes, as with the green macroblock monster in L226 (fixed in L227), what may help some people can really screw things up for others. I cross my fingers (and my toes, and even my eyes :eek2: ) everytime they make a change to the code for OTA reception.


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## Jeff McClellan (Apr 22, 2002)

I have tested the following with the 942 and my Sony KDF-50WE655 internal tuner.

Channel Master antennas-4228, 4221, 4248
Antennas Direct- 42xg, DB8, DB4- their antennas stink, now that they are made in China,
Radio Shack-15-2160
Winegard-4400 and 8800

the Sony held up better with Signal to noise ratio than the 942. But, Dish is close to matching it and it may not take much.

As for antennas in my area, the 4221 beat the rest hands down. In range, multipathing, hell everything. The 4221 beat the 4228 in range. I pull in stations, depending on time of day and weather, 110 miles away mounted 6 feet off roof. So thats my take, the 942 is doing pretty good in my thoughts.


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## Jeff McClellan (Apr 22, 2002)

zephyr, what antenna are you using and preamp. Are you only looking at getting digital stations and about how far away are your towers. Keep in mind that most will tell you that bigger and higher is better. Most that are really knowlegable in this field, will tell you this isn't true for UHF. I get more stations with my antenna mounted 5 feet lower. It has a cleaner line of sight at that height.


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## 421602 (Jan 30, 2004)

I have found a couple of things that worked for me. 

First: Don't use an AMP unless you absolutely have to. I tried very high end amps and they they helped the signal strength but not multipath. They made it worst. If you must use one, put it near the antenna, not near the TV. If you can only put it near the Tv/Receiver, you are probably better off justing letting the tuner get the signal unmolested.

Second: Try aiming your antenna away from your stations. For me. Aiming the antenna straight at the stations picked up lot's of multi-path. However aiming the antenna 30 degrees north decreased the strength but eliminated any multi-path I was getting and allowed me to get rock solid signals.


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## zephyr (Jun 25, 2005)

JEFF M said:


> zephyr, what antenna are you using and preamp. Are you only looking at getting digital stations and about how far away are your towers. Keep in mind that most will tell you that bigger and higher is better. Most that are really knowlegable in this field, will tell you this isn't true for UHF. I get more stations with my antenna mounted 5 feet lower. It has a cleaner line of sight at that height.


The antenna is a Royal 17, which is specifically designed for the Grand Rapids, MI market. It has 3 booms with elements of various lengths, tuned for the clustering of transmitters that are generally in 3 directions from our city. I am only interested in digital OTA, though analog is useful in aiming the antenna and diagnosing interference types.
The only issue with the antenna design is that a couple of the digital stations use much different channels than their analog counterparts. I have accommodated this by aiming two of the booms toward different transmitters than those for which they were originally designed. The result is the analog stations don't look so hot, but the digitals look great and are strong.
The problem child is 3.1, which transmits on 2. That boom is pointed as originally designed, and picks up the all the other stations in that direction great. Of course this is the most distant transmitter and has the longest wavlength, so it is the most susceptible to interference. The transmitter is 22 miles away.
The antenna is mounted in the attic, primarily for aesthetic reasons. I realize there is signal loss.
The reason I have raised the question about the 942 is that I own one and want to make it work. I have two other HD tuners that have pulled in every channel, including 3.1, day and night. The 942 only seems to want to receive it on a good night if it's in a good mood, and never when the sun's out.
I have purchased a Winegard pre-amp that I will try tomorrow.
I also am willing to move the antenna to the roof, but would prefer to tweak the existing setup first.
It is clear from reading many posts that the 942 OTA performance is not as hot as other receivers.
Oh, and [email protected], thank you for the suggestions.

Brian


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## Jeff McClellan (Apr 22, 2002)

get a channel master 4221, mount it on the roof on a 5 foot mast, get a rotor, get a Channel Master preamp, 7xxx series, use rg-6 quad shielded cable. Ground it. Put a variable attenuator from radio shack and place it between the power supply to the preamp and the receiver, get a male/female dc block to connect to the imput on the receiver, use GE silicon around all your outside rg connections, and sit back and enjoy.


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## zephyr (Jun 25, 2005)

Jeff M,

If I understand their literature correctly, the 4221 is a UHF antenna. Here, about half the digital channels are in the VHF band, so I need a combined VHF/UHF antenna.
I also will try the fixed, non-rotating antenna solution first, because it is mechanically simpler and does not have to be re-aimed if I want the 942 to record different OTA stations while I am not around.
Antennas are making brain surgery sound simple by comparison. 

Thanks!


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## zephyr (Jun 25, 2005)

[email protected] said:


> I have found a couple of things that worked for me.
> 
> ...Second: Try aiming your antenna away from your stations. For me. Aiming the antenna straight at the stations picked up lot's of multi-path. However aiming the antenna 30 degrees north decreased the strength but eliminated any multi-path I was getting and allowed me to get rock solid signals.


It works! It was also the same advice given to me by a professional antenna installer. Don't know if it was multipath, but whatever it was, the signal strength is lower and the reception is better.


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## JR_Baas (May 5, 2005)

zephyr said:


> It works! It was also the same advice given to me by a professional antenna installer. Don't know if it was multipath, but whatever it was, the signal strength is lower and the reception is better.


So what was your final setup? Are you using an amp, or an attenuator? Did you move the middle antenna more to the east? What signal strength are you getting on each station? Are you pointing the bottom antenna at WZZM and the top at WGVU? Any help would be appreciated.


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## zephyr (Jun 25, 2005)

JR_Baas said:


> So what was your final setup? Are you using an amp, or an attenuator? Did you move the middle antenna more to the east? What signal strength are you getting on each station? Are you pointing the bottom antenna at WZZM and the top at WGVU? Any help would be appreciated.


Final setup is Royal 17 with Wyngard 8700 pre-amp at antenna. Single RG6 downlead, power injector in basement, with splitter at back of TV for TV and 942.
Main boom is aimed about 142, which is almost 30 deg east of the "correct" bearing to transmitters.
Antenna is 'upside down' in attic, due to clearance at sloped roof. The 3 booms are on the mast right side up, but in reversed order. Main boom is still in the middle.
Boom originally designed for 35 is aimed at 13 and vice versa, to accommodate their different digital frequencies.
Signal strength is lowest on 3.1 (upper 60's, low 70's) and 43.1 (PAX). 13.1 and 17.1 are upper 80's. 35.1 low 90's. 8.1 is 100.
There are still occassional breakups on 3.1, but it appears this is as good as it will get without moving antenna to roof.


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## JM Anthony (Nov 16, 2003)

It's signal quality that's more often than not the key on OTA reception (assuming you live in reasonable proximity to the transmitter towers) versus relative strength. Invest a few bucks in getting an antenna specialist out and have him check your signals with a spectrum analyzer.

John


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## zephyr (Jun 25, 2005)

JM Anthony said:


> It's signal quality that's more often than not the key on OTA reception (assuming you live in reasonable proximity to the transmitter towers) versus relative strength. Invest a few bucks in getting an antenna specialist out and have him check your signals with a spectrum analyzer.
> 
> John


I agree. The issue of signal quality was noted in post #6. The 942 has a problem with 'below normal' signal quality, even though it can lock on to signals in the low 60's signal strength. I do not know what the signal quality issues are in my case, so the best move is the investment you recommend. I do suspect some kind of electrical interference, because analog OTA shows tiny sparks or white flashes/streaks in the picture. The worse the sparks, the worse the 942 does at locking. There are no ghosts or snow. In this case, the analog is an indicator of digital reception, because 3.1 transmits on 2. Thanks!


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## jpage4500 (Jul 30, 2005)

JM Anthony said:


> It's signal quality that's more often than not the key on OTA reception (assuming you live in reasonable proximity to the transmitter towers) versus relative strength. Invest a few bucks in getting an antenna specialist out and have him check your signals with a spectrum analyzer.
> 
> John


I'm also interested in finding the best position and hardware for an OTA signal. Where would I find an antenna specialist anyway? I don't suppose you can just pick up a spectrum analyzer at Radio Shack? 

j


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## zephyr (Jun 25, 2005)

jpage4500 said:


> I'm also interested in finding the best position and hardware for an OTA signal. Where would I find an antenna specialist anyway? I don't suppose you can just pick up a spectrum analyzer at Radio Shack?
> 
> j


In our community it was word of mouth plus yellow pages (antennas !). Best references were from older sales/service people at a traditional TV/appliance store. Analog antenna guys have had to learn the transition to digital.


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## JM Anthony (Nov 16, 2003)

jpage4500 said:


> I'm also interested in finding the best position and hardware for an OTA signal. Where would I find an antenna specialist anyway? I don't suppose you can just pick up a spectrum analyzer at Radio Shack?
> 
> j


Spectrum analyzers are pretty pricey, so you don't want to go there. Best bet. Head for your local high end A/V store (the guys with the REALLY good stuff) and ask who sets up their antennas. Give that dude a call. Other option - head to the AVS Forum and find the local thread for OTA issues in your area and check out their advice.

I pursued option one (because I didn't know of option two at the time) and hooked up with a guy who knew one hell of a lot about OTA issues. Cost me about $600 for him to do a custom install, but he pretty much guaranteed results after his initial survey and before I plunked down any cash. I live in the middle of an urban forest and I figured it would take a magician to get me a good signal. Well, this guy was Madrake. I get great reception on all of the major locals.

Good luck. OTA reception is as much art as it is science. If you're in a tough area, you definitely want some help to sort it all out. PM me if you want to kick this around some more. I learned some lessons along the way.

John


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