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I have a hughes E86 STB and am wondering what the OTA sig strength meter actually measures. Signal to noise ratio?, Bit error rate? I think it is more than basic signal level.

Jim
 

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From what I've read on the Antenna threads, the Signal Meter is just that = basic signal level.


Those threads state that, on their STBs, signals below 20% (of full scale) give no signal, between 20% and 40% they get intermittant picture (poor signal to noise ratio = SNR), and over 40% to 50% (depending on the STB) they get a perfect signal.


My conclusion is it's the RF level of the carrier being received. Anything else would seriously raise the cost of the STB.


- Claus
 

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In regards to the digital channels, when I started putting attenuators in my antenna cable, I never really saw the signal meter drop until I got to the point that it suddenly went to almost nothing. That point was with over 18dB of attenuation stacked on in 5 increments. I would think that if it was a measure of simple signal level, I would have seen a measured drop in signal level on the meter each time I added an attenuator.


I was told by an RF engineer at one of our local DTV stations that the OTA signal meter is an indicator of how well the receiver is locking on and decoding the digital signal, not an indicator of just how strong the RF signal is. He also told me that a bouncing or "breathing" signal level on the meter is an indicator of multipath reception problems.


-Mike
 

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Spike89's account is accurate.
 

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Quote:
Originally posted by Spike89
I was told by an RF engineer at one of our local DTV stations that the OTA signal meter is an indicator of how well the receiver is locking on and decoding the digital signal, not an indicator of just how strong the RF signal is. He also told me that a bouncing or "breathing" signal level on the meter is an indicator of multipath reception problems.


-Mike
As Greywolf said -- All true. One exception is the S/N and AGC readings on Hauppage's WINTV-D Card, which tells you a little more about the RF signal itself .. I don't know of any other exceptions, but there may be some.


Also, while a bouncing or fluctuating meter MAY mean multipath, instead, it MAY be an indication of other problems, such as Co-Channel/Adjacent channel interference, Preamp overload/Tuner overload/Intermodulation distortion, various other interference related issues, etc.


I expect, most, if not all(except the WINTV-D card) other DTV receivers out there implement their meters In the way(or in a very similar way) discussed in the explanation of ATSC receiver design in the following document(This document was put out by Zenith, and has loads of other great info on DTV/ATSC(Including results of 2600 field tests) as well) :

http://www.atscforum.org/doc/FieldTestReport.pdf


Follows is an excerpt from this document of what it says concerning how implementation of "signal meters" can be achieved in DTV receivers, from 1st paragraph of page 3 :


"The MPEG data sync is reinserted at the receiver output for subsequent processing in the receiver's MPEG transport decoder. The one-segment long binary frame sync not only provides pseudo-random number sequences(PN) for data frame synchronization, but can also be used as a training signal for the receiver's equalizer AND AS A MEANS TO MEASURE RECEIVED SIGNAL QUALITY."
 

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there are two signal levels

analog

digital (Eb/N)


my guess is your STB signal strength meter is recording the second


(On the coship 3188c receiver mpeg dvb receiver they list both)



--G
 

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G --


Did you read the 3 posts previous to yours? I don't believe Most(meaning almost all) Meters in Over-the-air, ATSC 8VSB DTV receivers(Not DVB, not sat receivers) measure "actual" signal strength, or S/N(Update - oops, I left an important part out, the next part) OR Error rate directly in any shape or form(even though they may say "Signal Strength" right on the screen) ...


From what I've seen, The only time they can(sometimes) give you any sort of "hint" of signal strength is when the signal is relatively weak, just over(probably within a few db or so over) the "threshold" needed for DTV reception.(approx 16db of S/N) ... As spike89 described, adding add'l attenuation in the feedline can often show you this(unless of course, you're dealing with a relatively weak signal to begin with, in which case any add'l attenuation will likely make the meter immediately begin to go down) ...
 

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That's what I like! Learn something new every time. Great :).


- Claus
 

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Quote:
Originally posted by Nitewatchman
G --


Did you read the 3 posts previous to yours? I don't believe Most(meaning almost all) Meters in Over-the-air, ATSC 8VSB DTV receivers(Not DVB, not sat receivers) measure "actual" signal strength, or S/N directly in any shape or form(even though they may say "Signal Strength" right on the screen) ...


From what I've seen, The only time they can(sometimes) give you any sort of "hint" of signal strength is when the signal is relatively weak, just over(probably within a few db or so over) the "threshold" needed for DTV reception.(approx 16db of S/N) l attenuation will likely make the meter immediately begin to go down) ...
Again, let me say this ... which is correct.


Since I have not tested what "most" OTA only STBs do, I

will not presume, like the above poster does, to say what they do.


I will merely say what the Samsung T-150 and T-151 models actually

do.


And that is, as best as I can tell, measure the actual

signal strength, not the signal to noise ratio nor errore rate.

It does, however, read zero if it cannot decode the signal,

so it can flop from very high to zero.


Certainly most pure satellite receivers actually measure error rate.


Doug McDonald
 

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Mr. Mcdonald,


If you read my above posts, you'll see I made sure to use words such as "believe" and "expect", "From What I have Seen" etc. I did not "presume" anything, I am merely basing my comments on what I, and others with various DTV receivers(including the models you mention) have experienced.


----------------------------------------

Update: Furthermore, Since Mr. Mcdonald Doesn't have AVS PM activated,(which is how I would have liked to address this issue more thoroughly)

Quote:
Originally posted by jdmcdonald
Since I have not tested what "most" OTA only STBs do, I

will not presume, like the above poster does, to say what they do.
Is there something about the below you don't understand? Especially note the last sentence :

Quote:
Originally posted by Nitewatchman
. One exception is the S/N and AGC readings on Hauppage's WINTV-D Card, which tells you a little more about the RF signal itself .. I don't know of any other exceptions, but there may be some.
------------------------------


IF I had knowledge which would demonstrate the meter on "such and such" specific model of receiver actually performs as a signal strength meter(as you may have noticed, I specifically mentioned the Hauppage WINTV-D card as an exception in one of my above posts - It doesn't have a "signal strength meter per se, but it does have S/N, AGC+error rate readings), then I would certianly say so, or I would have used some other word besides "most" ....


I certianly don't have any "hard" info which would indicate Exactly how(specifically) the Samsung T-151+T-150's "signal meters"(bars I believe) specifically work -- Should I maybe have made an exception for those receivers and excluded them in my "most" statement? Maybe so, but I have not heard any info on these receivers(including from your posts) which would demonstrate that it is, in fact an exception to my comments.


Specifically, on the Samsung models you mention, I(and I'm sure others here) would surely welcome some sort of evidence which would indicate what you are saying is true.


Now, I have heard differing reports on the Samsung T-151's meter, which is why I would welcome some "hard info" which would demonstrate what you are saying(where the T-151 is concerned) IS in fact, correct ....


------------------------------
 

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I suppose I should produce some evidence concerning the meters on the receivers I personally am using, currently(Zenith HDV420, RCA DTC-100) which, in part, is why I have made some of my above comments ... .


I receive 13 Local DTV stations Solidly from my location, all are within 39 miles of my location -- I'm quite sure that MOST of them have quite strong signals, but, one, I believe is quite a bit weaker than the others. They ALL show up in 76-100% range on the meters on both receivers - Given proper antenna aiming. This is true regardless of my distance from these stations, their power/frequency/terrain issues/etc. Couple of examples:


One of these stations(distance 32 miles - DT-34) was running 7KW ERP at first, a few months later they increased power to 215KW ERP, Using the same transmitting antenna - When they made this change, did I see a change in readings from either receiver(~88% readings)? No. However, When this station was at low power, I could only receive them w/o dropouts(and significantly lower readings) IF I aimed my fairly directional antenna(RS VU210) within 30 degrees or so of their tower --- After they increased power, I can now receive them with antenna off target 90 degrees+ without dropouts(more or less).


Another example ... One station, from 32 miles, DT-31 800KW ERP from approx 1600FT ASL(some 800FT or so AGL) -- 82~88% Reading on both receivers - Can receive it with antenna aimed almost in any direction, for the most part w/o dropouts. Ardman.net predicts around 80dbu signal strength from this station from my location. Takes some 20db+ of attenuation in feedline before meter readings being to go down from this station.


Another station - DT-24 - 53KW ERP from 1099FT ASL(279FT AGL), 39 Miles distant .. 76~82% readings off either receiver ... Can receive this station only within 30 degrees or so antenna heading ... Add any sort of add'l attenuation in feedline(even as little as 2db or so), and readings immediately begin to drop ... 3.5db of attenunation=readings in the low 50's .. 5-7db of attenuation .. Readings go below approx. 30% on either receiver, and I'm just at the level where the receiver can achieve a lock - but only get a frame of video every now and then. A detailed Longely rice propagation study(A Radiosoft software package was used) for my location indicated a predicted 43dbu signal strength for this station at my antenna ...


Do the meters show "0" when there is no(or very, very little signal), do they show low readings given signals which are quite weak, just below, or at the threshold required for DTV Reception? Yes ... But, Are the meters in my receivers acting as "Signal Strength" meters? I don't think so, even though, the RCA receiver says "Strength" right on the screen ... Does your Specific model of receiver have a real "signal strength" meter? I'd certianly be interested in learning about it, if it, in fact does ...
 
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