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AM21 Sensitivity Reduced - Why?


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#1 OFFLINE   gcd0865

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Posted 22 June 2009 - 12:01 AM

Hi All:

The OTA sensitivity of my AM21 and my tv's OTA tuner have always been quite comparable, even on the respective signal meters. Over the past two weeks or so, however, I think something has happened that has reduced the sensitivity of my AM21. If it makes any difference, I believe this happened before the June 12 DTV switch date, and none of these stations switched channel assignments or anything like that at the DTV switch date.

I have an antenna going into an A-B switch box for switching between my tv and my AM21. On my three distant channels (at night), I'm getting signal strengths of 45, 55 and 88 on my tv's signal meter and all three stations come in fine using the tv's tuner. All three of these stations used to also come in on the AM21, with approximately the same signal strengths. Now, two of these three stations don't come in at all on the AM21, and the third station (that registers an 88 on my tv's meter) comes in at 40-43 on the AM21. I knew that the two tuners were quite comparable previously because the two weakest of these stations would always appear in the evening at exactly the same time on both my tv's tuner and the AM21, as signal strengths came up (meaning that both tuners had approximately the same reception threshold based on signal strength).

To check for possible connection problems, I reversed the A-B switch, took the switch out of line, substituted the short coax going to the AM21, checked the cable going from the AM21 to my HR21, did a full reset followed by a new OTA setup, but couldn't trace any problems.

This is an all-of-a-sudden performance drop for my AM21. Could something have happened to my AM21 (heat?) that would reduce its sensitivity? Thanks in advance for any comments.

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#2 OFFLINE   litzdog911

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Posted 22 June 2009 - 12:31 AM

First time I've heard of a problem like this. I'm guessing you have a defective AM21.
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#3 OFFLINE   IDRick

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Posted 22 June 2009 - 09:44 AM

gcd, check your cables. You may have a loose connection, particularly between the AM21 and the a/b switch. In my case, a 45% signal strength really means that I have little margin to spare (on order of 3 to 5 dB before pixelating/dropout occurs). A pre-amp may help you. Need much more info before I can recommend a specific pre-amp. How many tvs? How many splitters? Total length of cable run? Which antenna are you using? Where is the antenna located? Can you post tvfool.com results from your actual address? We won't see your address, just the zip code and city.

#4 OFFLINE   gfrang

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Posted 22 June 2009 - 01:43 PM

It sounds to me like the am21 but what i would do next is pull the plug on the hr21 and am21 for a couple minutes and pull the usb plug and reinsert it.Plug it back in and see what happens.

#5 OFFLINE   dodge boy

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Posted 22 June 2009 - 10:03 PM

Mine does this too, I split the cable from the antenna to my TV and my AM21, my TV picks up all kinds of channels the AM21 wont, and I put the right zips in so all the same channels show up in the guide, just the AM21 won't tune them.

#6 OFFLINE   ciurca

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Posted 23 June 2009 - 10:19 AM

Same here, not so dramatic. Daytime, I would be around 88% for one and 75% for the other. Now I'm at around 80% and 65% respectively. My local cbs stated on June 12 that they would be upping their digital signal after shutting down the analog monster. I've only seen a decrease.
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#7 OFFLINE   gcd0865

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Posted 23 June 2009 - 01:15 PM

Thank you for all the comments. When time permits, I will check all the connections again (I had bypassed my switch and temporarily connected the AM21 to the antenna directly, with no change). I'm wondering if something has happened to the USB cable connecting the AM21 to the HR21 (I'll have to try a temporary substitute for that as well). I'll also try unplugging the units as suggested. The funny thing about this is that this isn't really an antenna or reception issue; my tv tuner and AM21 were exactly equal to each other two weeks ago, until one day, the AM21's sensitivity just went to crap all of a sudden.

#8 OFFLINE   David MacLeod

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Posted 23 June 2009 - 04:42 PM

I have had a usb issue on one, different cable fixed it.
my signals were lower than normal and jumping a lot.
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#9 OFFLINE   Davenlr

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Posted 23 June 2009 - 07:05 PM

Two things to consider...the AM21 has two tuners and a built in splitter, which will send a signal half as strong as the signal going to the tv, to each tuner.

Signal readings are dependent upon software on the host receiver. Did your software get updated at approx the same time this signal issue cropped up?

#10 OFFLINE   ciurca

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Posted 23 June 2009 - 07:42 PM

Two things to consider...the AM21 has two tuners and a built in splitter, which will send a signal half as strong as the signal going to the tv, to each tuner.

Signal readings are dependent upon software on the host receiver. Did your software get updated at approx the same time this signal issue cropped up?


So, there are probably no real changes in signal quality, just the measurement parameters?
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#11 OFFLINE   Davenlr

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Posted 24 June 2009 - 06:30 AM

I would say thats totally possible, except you said (I think) that you no longe get stations you used to?). If IRC, OP said "at night". Tropo enhanced reception can vary greatly, and cant be relied on. If you cant get a station at 2pm, but can at 8pm, its likely tropo enhanced reception and is out of your normal viewing range... In a case like that, the -3db splitter loss in the AM21 could be a deal breaker, and require you to "make it up" at the antenna (with more height) or (more capture area) or with a ln amp (channel master 7777) to overcome coax loss. This should get your -3db margin back.

#12 OFFLINE   gcd0865

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Posted 25 June 2009 - 08:43 AM

Hi All:

As an update, last night I unplugged the USB cable from the AM21 and did a full reset and new initial setup of the AM21. No difference. I then substituted a different USB cable between the AM21 and HR21; no difference there either. I didn't power down the units yet, as it's more difficult for me to reach back to do that (but I'll try that next).

To answer the other questions posted, the signal quality on the AM21 remains fine (for the stations that come in), just that the sensitivity of the AM21 has dropped substantially (and the signal meter now reads much lower). Before this all started, both my tv's tuner and my AM21 acted about the same: both would hold a stable picture at signal levels (on the respective signal meters) of greater than about 37; between 33-36 the picture would pixelate; and from 32 down, no picture and signal level would be at zero. Both my tv tuner and the AM21 would receive the exact same number of stations, and they would come in and fade out with nighttime/daytime passage at about the same time. Then, two weeks ago, something happened (instantly, one day) to the AM21.

Last night, distant stations were particularly strong, coming in mostly at 60-70 on my tv tuner. None of these would come in on the AM21 (but they all used to just fine, two weeks ago), except for one distant station registering 85 on my tv's signal meter; it registered about 45 last night on my AM21's meter. Local stations seem a little lower on the meter too, but not as much as the distant ones. So the AM21's sensitivity seems to have suddenly just dropped by 10-20 points for local stations, and up to 40 points for distant ones. The threshold for the AM21's tuner to lock on stations is the same as before (around 37), but since the sensitivity is now reduced so much, the number of channels received is less. I know it seems like I just have a bad coax cable or switch box, but I reversed the cables (no difference), substituted another cable (no difference) and took the switch box out of line to connect directly to the antenna (no difference).

Regarding the comments about antennas, amps, reception, tropo, etc., they are of course all factors in over-the-air reception, and I do still have some antenna system improvements to work on. But this is just a sharp all-of-a-sudden dropoff in my AM21 compared to what I reliably had before, so i'm just trying to diagnose that problem at this point.

I'll power down the units shortly and report back. But I'm suspecting that something in the circuitry of my AM21 just went bad one day about two weeks ago.

Thanks again for your interest and comments...

#13 OFFLINE   Davenlr

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Posted 25 June 2009 - 05:05 PM

Unless your DVRs software got updated at exactly the time this signal drop started, I would concur with you.

You might check the system info on the DVR and see if the data of the last software upgrade matches the date your problem started.

Are both tuners reading the identical signal level? It seems odd both would fail at the same time.

Hopefully unplugging and restarting will fix it up.

#14 OFFLINE   gcd0865

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Posted 26 June 2009 - 08:17 AM

Yes, both of the AM21's tuners are reading the identical signal level. Thanks for the additional tip; I'll also check the last software upgrade date.

#15 OFFLINE   gcd0865

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Posted 13 August 2009 - 07:25 AM

Hi All:

Wanted to give everyone an update on my AM21 situation, in case this happens to anyone else. I had double and triple-checked all my AM21 connections and became convinced that my AM21 was slowly going bad. Over the additional time since my last post, the signal strength numbers and the ability of the AM21 to receive stations continued to gradually decrease. Back in June, I had only lost my distant channels that were 50-65 miles away. But more recently, I gradually lost another station 25 miles away (it first started to pixelate, right at the threshold of being received, then I lost it altogether). This was a station that initially had an 85 signal strength that gradually declined to 34, then disappeared altogether on the meter. Then, I started to lose one or two of my local channels (8-12 miles away). Signal strength numbers continued to slowly decline through this time on the AM21, but my antenna was fine, as my tv's tuner still received everything just fine, with no signal strength change on the tv's meter.

I finally decided to call DirecTv, and was told that there is no warranty (at all) on the AM21, that they would not replace it, and that I had to purchase another one from them for $50 plus $3 tax. Since I could no longer reliably record shows over-the-air using my present AM21, I caved and bought another unit. Hooked up the new AM21 last night, using all of the original cables from the previous AM21, and it works perfectly (as good as the previous unit when it was brand new, getting all of my 50-65-mile stations again, and pretty much equivalent again to my tv's tuner).

Something gradually went bad with my original AM21 starting around May or June, where the unit resolved a picture just fine, but gradually lost its sensitivity, eventually getting to the point where it became useless. I had the AM21 directly on top of my HR21 receiver, as the AM21 manual says you can do. But when I removed the old AM21 to install the new one, the old one was quite warm overall, and was actually rather hot on the rear portion of the lower surface (maybe where the internal power supply is?). Perhaps the heat gradually affected some components inside that first AM21 over time. If it might be any issue, I seem to remember my HR21 showing a 117-degree internal temperature when I checked it a while back, which I was told was normal.

In any event, I installed the new AM21 in a different location, not directly on top of my HR21, and maybe others might want to consider the same, since there's no warranty on the AM21. If anyone else is noticing gradual reduced reception performance from their AM21, maybe the same thing is happening to yours. From how hot my AM21 was when I removed it, I don't think DirecTv should say in its manual that you can put it directly on top of your regular receiver. I also think it's a ripoff for DirecTv to not replace this unit for me at no cost. Even though the AM21 was a purchase, and not a lease, it ought to be covered in this kind of situation. Cable companies also lease their equipment to you, and if any equipment ever goes bad, they just replace it, because you are paying them a monthly fee for their service, which needs to work properly or you won't be satisfied.

I'd like to complain about this some more to DirecTv, but don't know who to contact. I'll certainly keep this in the back of my mind when cable HD offerings catch up to DirecTv (which looks like it will happen soon). I'd appreciate hearing anyone else's thoughts about this, or about their similar scenarios (if any). At least I feel a little better from venting. Hope this is helpful to prevent this from happening to anyone else...

#16 OFFLINE   tcusta00

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Posted 13 August 2009 - 07:39 AM

Hi All:

Wanted to give everyone an update on my AM21 situation, in case this happens to anyone else. I had double and triple-checked all my AM21 connections and became convinced that my AM21 was slowly going bad. Over the additional time since my last post, the signal strength numbers and the ability of the AM21 to receive stations continued to gradually decrease. Back in June, I had only lost my distant channels that were 50-65 miles away. But more recently, I gradually lost another station 25 miles away (it first started to pixelate, right at the threshold of being received, then I lost it altogether). This was a station that initially had an 85 signal strength that gradually declined to 34, then disappeared altogether on the meter. Then, I started to lose one or two of my local channels (8-12 miles away). Signal strength numbers continued to slowly decline through this time on the AM21, but my antenna was fine, as my tv's tuner still received everything just fine, with no signal strength change on the tv's meter.

I finally decided to call DirecTv, and was told that there is no warranty (at all) on the AM21, that they would not replace it, and that I had to purchase another one from them for $50 plus $3 tax. Since I could no longer reliably record shows over-the-air using my present AM21, I caved and bought another unit. Hooked up the new AM21 last night, using all of the original cables from the previous AM21, and it works perfectly (as good as the previous unit when it was brand new, getting all of my 50-65-mile stations again, and pretty much equivalent again to my tv's tuner).

Something gradually went bad with my original AM21 starting around May or June, where the unit resolved a picture just fine, but gradually lost its sensitivity, eventually getting to the point where it became useless. I had the AM21 directly on top of my HR21 receiver, as the AM21 manual says you can do. But when I removed the old AM21 to install the new one, the old one was quite warm overall, and was actually rather hot on the rear portion of the lower surface (maybe where the internal power supply is?). Perhaps the heat gradually affected some components inside that first AM21 over time. If it might be any issue, I seem to remember my HR21 showing a 117-degree internal temperature when I checked it a while back, which I was told was normal.

In any event, I installed the new AM21 in a different location, not directly on top of my HR21, and maybe others might want to consider the same, since there's no warranty on the AM21. If anyone else is noticing gradual reduced reception performance from their AM21, maybe the same thing is happening to yours. From how hot my AM21 was when I removed it, I don't think DirecTv should say in its manual that you can put it directly on top of your regular receiver. I also think it's a ripoff for DirecTv to not replace this unit for me at no cost. Even though the AM21 was a purchase, and not a lease, it ought to be covered in this kind of situation. Cable companies also lease their equipment to you, and if any equipment ever goes bad, they just replace it, because you are paying them a monthly fee for their service, which needs to work properly or you won't be satisfied.

I'd like to complain about this some more to DirecTv, but don't know who to contact. I'll certainly keep this in the back of my mind when cable HD offerings catch up to DirecTv (which looks like it will happen soon). I'd appreciate hearing anyone else's thoughts about this, or about their similar scenarios (if any). At least I feel a little better from venting. Hope this is helpful to prevent this from happening to anyone else...


Thanks for your update.

I would explain the situation in an email to the office of the Sr. VP of Customer Relations, Ellen Filipiak. While they may not be in a position to do anything about your situation now since it's resolved, they will probably take it under advisement and hopefully work to fix what's wrong with the AM21 itself and the warranty (or lack thereof). (Of course the forum trolls will respond otherwise)

The email to her office is ellen.filipiak@directv.com.

I think the tone of your thread and posts remained professional while getting across your criticisms, which is important in getting someone to listen to you at DirecTV and ultimately effect some change.

#17 OFFLINE   CCarncross

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Posted 13 August 2009 - 08:24 AM

While I see your point, since the AM21 is just an add-on ATSC they will sell you that does nothing to receive SAT signals, when and if they go bad D* really shouldnt have to replace them after the initial 90 day warranty or whatever they have. If they leased them fine, but they don't, they are purchased, and everyone should know they are purchased when they buy them. My understanding is the PP doesnt cover them either.

#18 OFFLINE   tcusta00

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Posted 13 August 2009 - 08:29 AM

I have to disagree. Most electronics have a one-year warranty.

Additionally, the capability that that AM21 provides to HR21/2/3 users is included in HR20s at no additional cost. If they're asking the customer to pay $50 to add this onto the receivers to get the same capability as older receivers then the least they can do is give a 1 year warranty. I understand the rules as they're currently written and hope to never have an AM21 go bad, but I must respectfully disagree with them.

#19 OFFLINE   DarinC

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Posted 13 August 2009 - 12:51 PM

If they're asking the customer to pay $50 to add this onto the receivers to get the same capability as older receivers then the least they can do is give a 1 year warranty.


Although, as you probably know, 90 days is all they give on a DVR as well. I know, because I had a drive die in a new owned box, which they wouldn't help on. Actually, was bad from day one, but it wasn't until it completely died into the 4th month that I realized it was a bad drive, and not just flaky HR21 issues. Unfortunately, you can't get warranty service direct from the drive manufacturer, because the serial# maps to an OEM.
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#20 OFFLINE   David MacLeod

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Posted 14 August 2009 - 05:35 PM

got spare am21 ready to go just in case :)
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