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Guest Message by DevFuse

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AM21 Sensitivity Reduced - Why?


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48 replies to this topic

#26 OFFLINE   mloiterman

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Posted 22 January 2012 - 11:43 PM

I can confirm that the AM21 is a major piece of junk. I'm on my third one and they all have died after about a year for the same reason.

The behavior is exactly has been described by others - out of the box the unit is able to lock onto a wide range of signals. The unit will operate fine for about year or maybe 18 months and then it gradually becomes unable to lock on to signals that it did when it was new.

Each time I have had to replace the box for $50.00 bucks. Sigh...

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#27 OFFLINE   CCarncross

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Posted 23 January 2012 - 07:34 AM

Both mine are over 2 years old...work the same as the day I got them.

#28 OFFLINE   Surveyor40

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Posted 23 January 2012 - 07:54 AM

I've been using the AM21 for about 3 years without issues on 4 of my DVR's. I would consider there maybe other factors causing the failure of the AM21, and not rule out an antenna system or electrical problem.

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#29 OFFLINE   say-what

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Posted 23 January 2012 - 09:07 AM

I have 2 AM21's. One I got as soon as they were available, the other 3 to 6 months later. I've used these two on various HR2x's over time (HR21, HR23, HR24 and HR34) and neither has had a problem and I use a small indoor antenna. The only problem I've had is when I've moved the antenna to clean and that affects the TV also.

#30 OFFLINE   jamsys

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Posted 14 January 2013 - 12:50 PM

I am having horrible problems with my AM21 and the HR34. Some days it finds the channels, some days it doesnt....

My peeve is that on page http://www.directv.c...protection_plan it states protection for ALL your DIRECTV devices.... I am paying $5.99 a month for this. After 5 calls and the same answer I dont know what to do...... They say that since its not a Sat box, it isnt covered, but I tell them to look at their web page and it says all devices!

Thoughts?

#31 OFFLINE   CCarncross

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Posted 14 January 2013 - 01:59 PM

I am having horrible problems with my AM21 and the HR34. Some days it finds the channels, some days it doesnt....

My peeve is that on page http://www.directv.c...protection_plan it states protection for ALL your DIRECTV devices.... I am paying $5.99 a month for this. After 5 calls and the same answer I dont know what to do...... They say that since its not a Sat box, it isnt covered, but I tell them to look at their web page and it says all devices!

Thoughts?


Exact words from the standard PP: All active DIRECTV™ Receivers, remote controls, dish antenna, wiring, connectors, switches, and dish antenna realignment.

It does not say all devices. It is not a Directv receiver, it does not fall under any of that wording. Are you perhaps looking at the wording for the Premier plan which is like $20 month?

#32 ONLINE   texasbrit

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Posted 15 January 2013 - 08:39 AM

I am having horrible problems with my AM21 and the HR34. Some days it finds the channels, some days it doesnt....

My peeve is that on page http://www.directv.c...protection_plan it states protection for ALL your DIRECTV devices.... I am paying $5.99 a month for this. After 5 calls and the same answer I dont know what to do...... They say that since its not a Sat box, it isnt covered, but I tell them to look at their web page and it says all devices!

Thoughts?


Your problem is almost certainly because your signals are too weak. The Hr34 is the only DVR that scans for signals instead of using a fixed database. The good news is that you can receive stations that are not in DirecTV's database. The bad news is that stations that have marginal signal can come and go, just as you are describing. With the other DVRs, you can only get stations that are in the database, but if the signal is low you might still receive them.
You almost certainly need a better antenna.

#33 OFFLINE   chrisjmccord

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Posted 17 January 2013 - 11:54 PM

Does it matter what kind of antenna you get to hook up to the AM21? I guess for looks sake I'd want to get one to put in the attic, but would need to run or fish a cable down the wall to the TV. What kind of antenna would you but for up in the attic? I'm not too far away from our towers here, maybe 5-8 miles?

#34 OFFLINE   moghedien

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Posted 18 January 2013 - 07:19 AM

The Hr34 is the only DVR that scans for signals instead of using a fixed database.


According to the Solidsignal website, the THR22(Directv TiVo) will also scan with the AM21. Is anyone here able to confirm or deny this?

#35 OFFLINE   Scott Kocourek

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Posted 18 January 2013 - 07:25 AM

Does it matter what kind of antenna you get to hook up to the AM21? I guess for looks sake I'd want to get one to put in the attic, but would need to run or fish a cable down the wall to the TV. What kind of antenna would you but for up in the attic? I'm not too far away from our towers here, maybe 5-8 miles?


Try these guys for your antenna questions. http://www.solidsign...&d=antenna-help

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#36 OFFLINE   palmgrower

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Posted 19 January 2013 - 10:42 AM

I added amplifiers after the off air antennas to drive the signal, zero issues with AM21's since and marginal locks are solid locks, good luck:)

I used a Winegard HDA100 15 dB Distribution TV Antenna Amplifier (HDA-100)

Edited by palmgrower, 21 January 2013 - 08:14 AM.

2- HR24-500 with AM21n OTA's & RC65RBX Backlit Remotes
1- HR34-700 with AM21n OTA & RC65RBX Backlit Remote
2- Samsung PN59D8000 Plasmas
Winegard YA 1713 Prostar 1000
Televes DAT 75 Deep Fringe UHF
DIRECTV AU9-SWM-13 LNB


#37 OFFLINE   Garyunc

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Posted 19 January 2013 - 11:00 AM

I got a AM21 and a AM21N. Ive notice that on the AM21 I have a station that is 100%. Then if I hook the AM21N to the same reciever the signal is about 87%.


+1. Amplifier is the way to go.

This is the one I got.
http://www.radioshac...oductId=2103093
DirecTV customer since 1995

#38 OFFLINE   veryoldschool

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Posted 19 January 2013 - 11:10 AM

+1. Amplifier is the way to go.

This is the one I got.
http://www.radioshac...oductId=2103093


If you're going to go with an amp, this one might be a better choice: http://www.solidsign...&sku=1579839664

Why is because it has a noise figure of 3 dB, and the radioshack doesn't bother to list theirs, which means it might be as high as 8 dB.

BTW I also have a Radioshack very similar to that one [with only one output] and it barely makes a difference to my weak channels.
A.K.A VOS

#39 ONLINE   texasbrit

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Posted 19 January 2013 - 11:25 AM

According to the Solidsignal website, the THR22(Directv TiVo) will also scan with the AM21. Is anyone here able to confirm or deny this?

Yes, that is apparently true although I don't have one to confirm it.

#40 OFFLINE   P Smith

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Posted 19 January 2013 - 12:23 PM

Yes, that is apparently true although I don't have one to confirm it.


:confused: then why not provide a link to your source ? we will follow there to see its credibility ...

#41 OFFLINE   tigerwillow1

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Posted 19 January 2013 - 08:09 PM

If you're going to go with an amp, this one might be a better choice: http://www.solidsign...&sku=1579839664
.

As an "enhancement" to this suggestion, this is the Winegard HDA100. Look also at the HDA200, only a few bucks more. In addition to more gain (and :-( higher noise figure), it has an adjustable attenuator. I used the HDA200 with my AM21 and found that it was just as bad receiving signals that were too strong as those that were too weak. The amp had to be adjusted "just right" for me to pull in the stronger and weaker stations at the same time. I've posted before about the AM21 being a "weak" receiver, with it not picking up at all stations that were solid on two other receivers split off of the same antenna. With a Dish DVR now using the same connection that the AM21 formerly was, OTA reception is much more reliable, and the gain setting on the amp doesn't make a bit of difference except for changing the reading on the signal meter.

#42 OFFLINE   veryoldschool

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Posted 19 January 2013 - 09:04 PM

As an "enhancement" to this suggestion, this is the Winegard HDA100. Look also at the HDA200, only a few bucks more. In addition to more gain (and :-( higher noise figure), it has an adjustable attenuator. I used the HDA200 with my AM21 and found that it was just as bad receiving signals that were too strong as those that were too weak. The amp had to be adjusted "just right" for me to pull in the stronger and weaker stations at the same time. I've posted before about the AM21 being a "weak" receiver, with it not picking up at all stations that were solid on two other receivers split off of the same antenna. With a Dish DVR now using the same connection that the AM21 formerly was, OTA reception is much more reliable, and the gain setting on the amp doesn't make a bit of difference except for changing the reading on the signal meter.

You bring up a good point [that I don't agree with :lol:]

First: not all solutions will work in every situation.

You can over amplify the signals for the strong stations as you're trying to boost the weak stations.
Dynamic range of the tuner [any tuner] is what comes into play here.

The HDA200 has a 4.5 dB NF and a max gain of 24 dB
The HDA100 has a 3 dB NF and gain [fixed] of 15 dB

So the question sort of comes down to how much gain do you need for the weak signals verses how much noise are you adding, thus reducing the noise margin, which is what this is all about.

The best solution is using a larger antenna, as its gain doesn't add any noise.
The next is to use a low noise amp, and add another amp if you need more gain for distribution losses [cable & splitters].

The HDA200 gain ranges from 6 dB [max attenuation] to 24 dB.
At its minimum gain, you've got 6 dB, but you're adding 4.5 dB NF
Not the best solution is it?
It would be better at about 16 dB of gain, as the noise margin would now be close to the HDA100, and it would then work better to the 24 dB output, "if" you needed that much gain.

Now if I needed more gain than the HDA100, adding a http://www.solidsign...ku=610370581759

Might be a better choice.
The combined NF would be < 3.5 dB and the total gain would be ≈ 26-36 dB.
Again not every solution is best for every situation.

And if you're dealing with trying to find the sweet spot between the strongest and weakest signals, it might only need one of these:
http://www.solidsign...ku=853748001293

YMMV
A.K.A VOS

#43 OFFLINE   tuff bob

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Posted 20 January 2013 - 11:13 AM

It is not a Directv receiver, it does not fall under any of that wording


That's real cheesy to use that as an exception. It a receiver and its got DirecTV written on it.
Half a DLB, Half a DVR.

#44 OFFLINE   jcwest

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Posted 20 January 2013 - 12:40 PM

In Mobile Al. during the summer "storm season" we frequently have extremely large afternoon/evening storms passing by, hence the need for OTA backup to satellite locals.

I got the AM21 right after I got my first HR21 box (2007 I think) our NBC channel is on the fringe of constant strong signal.
Added the Channel Master 7777 signal amp and have never looked back.
Signal via the AM21 has been rock solid every since.

J C

HR20-700
HR34-700 AM21
HR21-200 AM21N
HR21-200


#45 OFFLINE   gov

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Posted 20 January 2013 - 06:24 PM

A rule of thumb from 'sparky school':

Connect one TV to your antenna (no splitters, no amps) and the stations you get are the stations you are going to get when you're done. RF amps just let you drive more tuners (with appropriate splitters), they don't drag signal out of the noise.

But, remember, for me 'sparky school' was before digital anything. LOL! Maybe ATSC is a little more forgiving ??

#46 OFFLINE   Davenlr

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Posted 20 January 2013 - 06:29 PM

A rule of thumb from 'sparky school':

Connect one TV to your antenna (no splitters, no amps) and the stations you get are the stations you are going to get when you're done.


Not actually true. By using a mast mounted preamp, any stations above the noise floor at the antenna terminals, will be present after the often rather high coax losses, at the TV. Without the preamp, stations you otherwise would be able to receive, might get lost in the attenuation of the coax. This is especially true when using RG59, or if the stations are on UHF band (which most ATSC stations are).

You are correct in that the use of amps on the indoor end of the coax only serve to boost the signal enough to pass through splitters, but dont improve the incoming signal at all.

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#47 OFFLINE   veryoldschool

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Posted 20 January 2013 - 08:19 PM

A rule of thumb from 'sparky school':

Connect one TV to your antenna (no splitters, no amps) and the stations you get are the stations you are going to get when you're done. RF amps just let you drive more tuners (with appropriate splitters), they don't drag signal out of the noise.

But, remember, for me 'sparky school' was before digital anything. LOL! Maybe ATSC is a little more forgiving ??


Not actually true. By using a mast mounted preamp, any stations above the noise floor at the antenna terminals, will be present after the often rather high coax losses, at the TV. Without the preamp, stations you otherwise would be able to receive, might get lost in the attenuation of the coax. This is especially true when using RG59, or if the stations are on UHF band (which most ATSC stations are).

You are correct in that the use of amps on the indoor end of the coax only serve to boost the signal enough to pass through splitters, but dont improve the incoming signal at all.

Seems we all have our take on this.

I don't see either as "wrong", but I still see more to what both are trying to say.

The noise floor starts at about -106 dBm, so you need 15-16 dB SNR/CNR for ATSC.

Your best [primary] gain comes for the antenna.
From here the loss of the transmission lines drops signal, but not noise power.

Using an amp generally defines the system NF, as loss/gain is linear, but cascaded NF is anything but linear, as you can find here: http://www1.sphere.n...b/tool/NF_e.htm
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#48 OFFLINE   bflora

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Posted 20 January 2013 - 08:49 PM

Amps never improve the S/N ratio at any given point in the line but they can help preserve S/N ratio 'downstream'.

#49 OFFLINE   veryoldschool

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Posted 20 January 2013 - 08:59 PM

Amps never improve the S/N ratio at any given point in the line but they can help preserve S/N ratio 'downstream'.

This is true, and the only thing you can play with is what is "upstream" and where downstream starts.
A.K.A VOS




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