# OTA lock issue



## 4HiMarks (Jan 21, 2004)

I don't know if this is an issue with the 921 or something else in the signal path since all of my equipment was installed at the same time, so I'm X-posting here and on the Balt-DC locals thread over at AVS Forum. 

I live in Laurel, MD, about halfway between Balt. and DC. The DC stations are all about 15 miles to the SW of me, while the Balt. stations are about 20 miles to the NE. The Balt. stations come in fine (with minor dropouts), but I currently am unable to get any lock on the DC digital signals. If I go into the Point Dish menu and tune to the frequency they broacast at the signal-strength meter will go up to between around 67-75 (depending on station) and then immediately change to "not locked" and drop to zero. After a second or two, it repeats. It does this over and over. The SS on the Balt. stations varies between 86 and 107. (Fortunately, the 107 is on CBS, so I should be OK for the Super Bowl.) 

I can pick up the analog stations pretty well though. I have a Terk TV44 attached to my dish on the back (north) side of my roof. So, is it the 921, the antenna, the antenna placement, or the stations that is to blame? I have no problem with the idea of getting a better antenna, but I would rather not spend the money if it is a software bug in the 921 that will be fixed in a future upgrade. 

Does anyone else have trouble locking in on signals in the 67-75 signal strength range?

-Chris


----------



## jsanders (Jan 21, 2004)

4HiMarks said:


> I live in Laurel, MD, about halfway between Balt. and DC. The DC stations are all about 15 miles to the SW of me, while the Balt. stations are about 20 miles to the NE.
> 
> I can pick up the analog stations pretty well though. I have a Terk TV44 attached to my dish on the back (north) side of my roof. So, is it the 921, the antenna, the antenna placement, or the stations that is to blame? I have no problem with the idea of getting a better antenna, but I would rather not spend the money if it is a software bug in the 921 that will be fixed in a future upgrade.
> 
> ...


Is your UHF antenna directional, or omnidirectional?? Sometimes the pure signal strength isn't the problem in the metopolitan area, multipath can also be a huge issue. Reflected signals combine with the original one to create a hybrid signal that is a bit messed up. In the analog world, this would appear as ghosting. Anyway, a directional antenna, tends to block out reflections, and it is higher gain too. The problem is that you need to move the antenna around to get signals off of different towers. If you need signals from different towers, you can use multiple antennas with combiners, however, the distance between the antennas is important depending on the channel you are after. It think it was 10 feet if you want channel 2, UHF frequencies are less distance. The other caveat is that the leads going between the antenna and the combiner must be the same length to prevent the multipath that was just mentioned.....


----------



## BarryO (Dec 16, 2003)

4HiMarks said:


> If I go into the Point Dish menu and tune to the frequency they broacast at the signal-strength meter will go up to between around 67-75 (depending on station) and then immediately change to "not locked" and drop to zero. After a second or two, it repeats. It does this over and over. ... I can pick up the analog stations pretty well though.


This is typical behavior for an 8vsb tuner that cannot acheive/maintain sync lock on a station. 'probably due to excessive multipath; I wouldn't count this as a 921 bug.

If the analog stations are VHF, and the digitals are UHF, the analog reception isn't a good indicator of digital reception; the propagation characteristics of the UHF and VHF bands are very different.


----------



## 4HiMarks (Jan 21, 2004)

BarryO said:


> This is typical behavior for an 8vsb tuner that cannot acheive/maintain sync lock on a station. 'probably due to excessive multipath; I wouldn't count this as a 921 bug.
> 
> If the analog stations are VHF, and the digitals are UHF, the analog reception isn't a good indicator of digital reception; the propagation characteristics of the UHF and VHF bands are very different.


I thought multipath was generally only a problem in urban areas where there are a lot of tall buildings and the transmitter is relatively close. I am in a far suburb with a lot of empty space and 1-2 story homes around.

I didn't think analog VHF reception was a good indicator of digital UHF, but I couldn't be sure.

-Chris


----------



## paulcdavis (Jan 22, 2004)

I get the same oscillating lock / not locked pattern from the broadcast antennas close to my house (1.3 miles to Sutro tower, San Francisco, but no line of sight due to topography). I am able to get a stable lock on all of the Sacramento stations 62 miles away with signal strengths in the 70 - 80 range. I have a channel master 3023 large directional UHF antenna on a roof mast with a rotor. Does anyone know what the lowest signal strengh the 921 needs to get a stable lock?


----------



## Mark Lamutt (Mar 24, 2002)

Definitely a multipath problem.

I'm getting a station lock at about 55 on my 921, although it breaks up from time to time.


----------



## invaliduser88 (Apr 23, 2002)

Go to http://www.antennaweb.org/aw/welcome.aspx and look at what it recommends.

Will even provide you with a map and recommand initial direction to point your antenna for reception of certain channels.

Cheers!


----------

