OTA Signal Analyzers, Meters, Aimers, Bench Gear, Diagnostic Software - Page 3 - Canadian TV, Computing and Home Theatre Forums

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post #31 of 311 (permalink) Old 2009-01-12, 05:58 PM
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I don't see much need for doing ATSC analysis since they're not directly related.
Yep, despite marketing hype, I have yet to see any evidence that one antenna produces a better or worse waveform pattern than another. (except when at the very ends of the bandwidth range) ATSC antenna gain is the same as NTSC antenna gain.

I guess it may be possible to distort the waveform pattern using very jagged elements, but no one does that, heh.

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post #32 of 311 (permalink) Old 2009-03-24, 04:32 PM
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I had a spectrum analyzer hooked up to an antenna and just moved it up and down and side to side near ground level and found the signals would vary by 5 to 10 db in just a few feet.
For an average Tv user, and antenna builder, is it worthwhile getting one of these analyzers...I have no other way to measure the signal strengths...
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post #33 of 311 (permalink) Old 2009-03-24, 04:50 PM
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For an average Tv user, and antenna builder, is it worthwhile getting one of these analyzers...I have no other way to measure the signal strengths...
A cheap CECB, like the Apex DT502 or Sansonic FT300a which have both Signal Quality and Signal Strength meters are sensitive, down and dirty tools to use.

According to rabbit73 (on the other forum) the Apex DT502 is more sensitive than his new digital meter.


Quote:
Originally Posted by 300ohm
rabbit73,

Id be interested in seeing a comparison analysis of your new digital meter compared to the two signal meters on your Apex DT502 CECB.

rabbit73:
Here is the comparison. Most of the signal level readings were made with the DisplayMax 800, but I added a few from the 719E for comparison or when the level was too low for the 800. The specs for the 800 say that it can read digital down to -23dBmV. When the level is too low for it, the display says "Ur." which I assume to mean unreadable. I used the same box #1 as last time, first in a strong signal location:


Code:
Attenuator Quality Strength DM800 719E
dB % % dBmV dBmV

0 100 84 +14.1 +12.5
3 100 84 +11.2
6 100 84 +7.6
9 100 83 +4.8
12 100 80 +2.5
15 100 75 -0.8
18 100 72 -4.6
21 100 67 -7.7
24 100 64 -10.2
27 100 60 -12.8
30 100 56 -14.9
33 100 53 -17.1
36 100 47 Ur. -23.0
39 100 42 -27.2
42 100 37 -28.5
45 66 27 -35
48 34 0

The OTA readings seemed to vary a bit that day, probably because of the strong wind through the trees that are in the signal path.

and then in a weak signal location:

Code:
Attenuator Quality Strength DM800 719E
dB % % dBmV dBmV

0 100 62 -14.1 -17.5
3 100 54 -16.3
6 100 49 -18.4
9 100 44 Ur. -26.0
12 99 37 -29.5
15 81 32 -35
18 21 0 -38
21 DropoutI think that all CECBs should have two signal bars because of the importance of signal QUALITY for digital reception. So far, I have tested the Zinwell ZAT-970A, the Apex DT502, and the Sansonic FT300A. My first choice as a measurement tool is the Apex. The Zinwell and Sansonic don't always give consistent readings for the same input, and the Sansonic bars take a long time to respond to changes.
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From *** forum page 288 Rabbit73 2-10-2009

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post #34 of 311 (permalink) Old 2009-03-24, 04:53 PM
 
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Balm

a spectrum analyzer is very expensive and most likely beyond the reach of many of us (think the price of a car!). Maybe you could rent one or know someone that can borrow one from work

a less expensive option is to buy an antenna analyzer for couple hundreds dollars but you won't get the fancy graphical output
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post #35 of 311 (permalink) Old 2009-03-24, 06:35 PM
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Ok then, I think I would rather buy the car for that price...

Are the antenna analyzers easy to get...
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post #36 of 311 (permalink) Old 2009-03-24, 06:39 PM
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post #37 of 311 (permalink) Old 2009-04-09, 06:03 PM
 
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Antenna testing

I may have the means to play with this.

A couple of questions:

Could the transmit ant. be a simple set of rabbit ears adjusted to 1/2 wave at the test frequency?

What minimum distance would the ant. under test have to be from the transmit ant. to be considered in the far field at UHF frequencies?

I found some math on far field measurements online but am confused by what is called "largest ant. dimension" in the formula.
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post #38 of 311 (permalink) Old 2009-06-18, 12:13 PM
 
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New RF Spectrum Analyser?

Saw this in the news today. Any applicatiosn for OTA?

http://www.brightsideofnews.com/news...n-rf-chip.aspx

EDIT opps the title of the article is terrible. its a spectrum analyser not an antenna....
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post #39 of 311 (permalink) Old 2009-06-18, 02:23 PM
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I believe many industries that utilize RF could use a better Spectrum Analyzer. However, this one is still in R&D mode, and is apparently analog only. Therefore, I don't see a practical use for OTA at this time....
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post #40 of 311 (permalink) Old 2009-08-09, 12:31 PM
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Cool Photo Album - ATSC Signals on a Spectrum Analyzer

In case anyone was a little curious to see what ATSC TV signals looked like on a Spectrum Analyzer (I was).
I took some pictures and posted them in a photo album.
Location is , Buffalo, NY. Antenna used was a Gray Hoverman
(only the driven element) hanging in the basement.
Apparently doesn't take much signal to be able to watch
TV.

Another use for these UHF antennas. Buffalo Police just happen
to use UHF 400 Mhz, so the GH makes a decent scanner antenna also.





The rest of the album is here:

http://www.digitalhome.ca/forum/picture.php?albumid=293
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post #41 of 311 (permalink) Old 2009-08-09, 12:43 PM
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Quote:
Apparently doesn't take much signal to be able to watch
TV.
That's long been known as one of the advantages of digital signals. Depending on the modulation & reception methods, it's even possible to recover a signal that's below the noise level, something that's pretty much impossible with analog. If you look at the digital TV transmitters, you'll find they're running much less power than the old analog transmitters.
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post #42 of 311 (permalink) Old 2009-08-09, 12:49 PM
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Yeah, I know.
Wouldn't mind looking at a typical Link Budget for ATSC TV reception.
Happen to know of something to look at online, lemme know...
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post #43 of 311 (permalink) Old 2009-08-09, 07:30 PM
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Quote:
Originally Posted by JamesK View Post
That's long been known as one of the advantages of digital signals. Depending on the modulation & reception methods, it's even possible to recover a signal that's below the noise level, something that's pretty much impossible with analog.
Amateur radio operators have been doing that for a while with PSK31. The desired signal is typically below the noise level but the software pulls it out and makes a usable signal.
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post #44 of 311 (permalink) Old 2009-08-12, 01:27 PM
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Quote:
Wouldn't mind looking at a typical Link Budget for ATSC TV reception.
Happen to know of something to look at online, lemme know...
TVFool.com interactive maps feature is a good start. You can see the receive power level at any location you which on google maps. Click on the station id, and you can gt a colour coded power level map.

It won't do the rain fade part of the link budget, though, if that's what you're looking for -- just terrain-based propagation issues.
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post #45 of 311 (permalink) Old 2009-10-21, 04:31 PM
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The fol. should help to sort out the different Signal Level Meters.

1. Inexpensive "Satellite Signal Level Meters" are ONLY good for aligning SAT dishes:
http://www.solidsignal.com/pview.asp...=2I7SF01005354

2. Inexpensive "OTA Signal Level Meters" are simple, full-band energy detectors which
are useful to align OTA DTV Antenna...but ONLY when ALL desired LOCAL, STRONG towers
are in the same location---which hardly EVER happens in real world applications:
http://transatelectronics.com/store/...fb055ca6cde549

3. Some CECB Converter Boxes have been cross-calibrated against professional Signal Level Meters:
http://www.avsforum.com/avs-vb/showp...postcount=9117
Probably the least expensive way to measure signal strength on a channel-by-channel basis
and will measure very weak signals.
Some USB Stick Tuners also display Signal Strength (e.g. HDHomeRun, et. al.) but I have not
(yet) seen any data re cross-calibration to professional Signal Level Meters.

4. There are VERY FEW low cost OTA Signal Level Analyzers which can display receive levels
for individual channels. Here's the Digiair Pro for just under $200:
http://www.solidsignal.com/pview.asp...ource=googleps
However, it will not measure very weak signals, so consider using a Preamp with it.

4. There are numerous Analog TV "Field Strength Meters" appearing from time to time
on the used equipment market. An adjustment factor is needed to convert from Peak Reading
for Analog to Average Reading for Digital. Correction may vary from model to model:
http://www.pi-usa.com/pdf/dtva.pdf
http://www.boonton.com/pdf/AN50.pdf
BTW: If the "Field Strength Meter" comes with an antenna, it's intended to measure
the very strong signal levels in the vicinity of the transmitter....not the receiver....

5. Pricey, professional OTA/CATV Signal Level Meters with increasing levels of useful features:
White Paper from 2003: http://www.sencore.com/uploads/files...RF_Signals.pdf
Some are CATV ONLY, whereas some do both OTA and CATV. Some even add SAT band.
http://www.sencore.com/products/rf-analysis/
Carefully check the minimum signal level capability....many are intended for CATV use
and have limited sensitivity when used for OTA.

6. Expensive Spectrum Analyzers that can display multipath degradation and various sorts
of interference, whether co-channel, adjacent channel or intermodulation distortion.
Some of the more expensive Signal Level Meters have this capability built-in.

Additional info:
http://www.avsforum.com/avs-vb/showthread.php?t=1084674
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