OTA Signal Analyzers, Meters, Aimers, Bench Gear, Diagnostic Software - Page 5 - Canadian TV, Computing and Home Theatre Forums

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post #61 of 311 (permalink) Old 2010-04-29, 10:22 PM
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Originally Posted by bpringlemeir View Post
Err, ok. Do you know of a PCI ATSC Tuner card that works under Linux that has a better front end?
Heh.. we have an _exclusively_ Linux household here!

My favourite Linux ATSC tuner is the HVR-950Q USB stick. But others in the HTPC forum here swear that the HVR-1250 and HVR-2250 are its equal or superior. And Stampeder has his own recommendation there!

I got into the pre-amp biz by wanting to receive WNPI-DT here, which was just "over the cliff" with my "5th generation" ATSC tuners, despite having a UHF-only (think.. "VHF/FM trap") RC preamp.

Then I got a Viewsonic TV that could pull it in _almost_ good enough to watch. So then I went to Staples (30-day try-and-return warranty) for the HVR-950Q. Bliss!

My suggestion to you, is to try the same -- get an HVR-950Q from somewhere (Staples?) with a return policy, and try it.

I do adore my two RC pre-amps, but they really only add less than 1dB over the cheaper Kitz pre-amps, despite their far more extensive circuitry. So unless you have money to burn, hold off on those until you've tried a modern ATSC tuner.

On the other hand -- if you are splitting the incoming signal with no amplification, then.. yes.. get a good pre-amp. Absolutely, definitely, no hesitation.

The Kitztech ones are good, the RC ones are great! If you have a lot of FM energy in the spectrum, then get a ChannelMaster instead (they have FM traps). Or if you don't give a willy about VHF, then absolutely get the RC 9254 (UHF-only) pre-amp. It rules that segment!

Cheers
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post #62 of 311 (permalink) Old 2010-04-30, 12:17 AM
 
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Originally Posted by mlord View Post
On the other hand -- if you are splitting the incoming signal with no amplification, then.. yes.. get a good pre-amp. Absolutely, definitely, no hesitation.

The Kitztech ones are good, the RC ones are great! If you have a lot of FM energy in the spectrum, then get a ChannelMaster instead (they have FM traps). Or if you don't give a willy about VHF, then absolutely get the RC 9254 (UHF-only) pre-amp. It rules that segment!
I don't think I have the maximum input figures for the Kitztech amplifier. However, is there no answer to measuring the power present at the antenna? Is there some device I can buy or a circuit I could build? Maybe rent a 1GHz DSO? The save and replay has some devices like this, http://overtheair.saveandreplay.com/ota_products.asp (ATSC DVB-T Signal Finder) and http://overtheair.saveandreplay.com/digiair.asp.

Is using a regular 75Ohm resistor as a load find for measuring the voltage and just a volt meter? It seems like it, or does all the multi-port/VWSR/S-parameter stuff apply at 800Mhz?

Thanks again.
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post #63 of 311 (permalink) Old 2010-04-30, 12:10 PM
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Least expensive DTV OTA Signal Level Meter is a "calibrated" CECB:
http://www.avsforum.com/avs-vb/showp...postcount=9117
Of course, don't expect the highest accuracy and YOUR CECB may have somewhat different "calibration".

Next is the DigiAir Pro or DigiAir Pro 2, but it isn't very sensitive and might need a (calibrated gain?) Preamp:
https://www.perfect-10.tv/P10WebAx/P...20Pro%2004.pdf
I think the sensitivity level for my DigiAir Pro is about 40 dBuV (-20 dBmV or -69 dBm).
[Don't confuse OTA DigiAir Pro with similar devices designed for SAT.]

Inexpensive used (Peak Reading) ANALOG Signal Level Meters can be purchased, but can have different
"re-calibration factors" when used to measure (Average) DIGITAL power levels:
http://www.pi-usa.com/pdf/dtva.pdf

A new DIGITAL Signal Level Meter is going to cost $1000++, such as used to "calibrate" the CECBs above.
Carefully check the sensitivity specs....many are intended for Cable rather than OTA....
Some "Cable" Signal Level Meters only have 30 dBmV (-19 dBm) sensitivity ($600 and up).
Sencore SLM 1476CM ($2000+) reaches ultimate sensitivity (15 dBuV, -45 dBmV or -94 dBm...typo on their spec).
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post #64 of 311 (permalink) Old 2010-04-30, 12:17 PM
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Quote:
Originally Posted by mlord View Post
But others in the HTPC forum here swear that the HVR-1250 and HVR-2250 are its equal or superior.
FYI the Linux drivers for the HVR-1250 and HVR-2250 only support the digital tuners. The analog tuners are not currently supported. With that being the case, you are paying for an MPEG encoder that you aren't able to use.

Also IR is not supported with these cards.
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post #65 of 311 (permalink) Old 2010-04-30, 01:34 PM
 
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I have to echo exactly what mlord and other have said re: tuners.

I just went through weeks of trying and trying to get better reception with a Kworld 120 PCI tuner. I stacked antennas, tried re-aiming, tried pre-amping, tried dist.-amping, etc. Some of it helped a bit, but not enough to justify all of my effort.

Finally I plugged the coax straight into my ViewSonic TV and BAM!, all my "iffy" channels were solid and I ended up getting channels that I didn't even know I could get before.

So then I bought an Hauppauge HVR-1250 and stuck it in my PVR. It gets all the same channels, no problem. It is a night-day difference. Seriously, I went from 18 or so (14 on bad days due to several "iffy") channels to 23 solid channels (26 if ION is ducting) just by changing the tuner.

PS. Even after adding another 50ft of coax (due to a re-routing issue), a grounding block and a 2-way splitter, the signals are solid.
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post #66 of 311 (permalink) Old 2010-05-01, 08:05 PM
 
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Quote:
Originally Posted by holl_ands View Post
Least expensive DTV OTA Signal Level Meter is a "calibrated" CECB:

Next is the DigiAir Pro or DigiAir Pro 2, but it isn't very sensitive and might need a (calibrated gain?) Preamp:

Inexpensive used (Peak Reading) ANALOG Signal Level Meters can be purchased, but can have different
"re-calibration factors" when used to measure (Average) DIGITAL power levels:

A new DIGITAL Signal Level Meter is going to cost $1000++, such as used to "calibrate" the CECBs above.
So, off the shelf devices will cost about the same as (or more than) a pre-amp itself. Even the DigiAir Pro is doing more than what is needed. I see that the LTC6405IMS8E has a unity gain at 2.7GHz and a -3dB point of 800 Mhz. If a 75Ohm load was the input in unity gain mode (to OpAmp above) with a diode bridge followed by an RC on the output, wouldn't that give a pretty good voltage estimate over the 800MHz frequency?

I see this chip basically does what I want at an alternate frequency range.
http://cds.linear.com/docs/Datasheet/5504f.pdf

I am proposing the same circuit without the mixer in the middle so that the whole ATSC frequency range is used. I guess a high/band pass filter could/should also be used. I think these components might run $20 (and a lot of time to get the right passives and layout). No IC like this exists for the ATSC band for automatic gain control or other uses? I guess AGC is integrated in bigger chips for ATSC.

Maybe I will buy an pre-amp and see if it works. I have calculation using azimuthal data for the CM4221 from hdtv primer (but I have the CM4221HD). Also, the DB loss past 45deg starts to get steep; ie difficult to control. Also, I think that multi-path reflections might add some power (especially bounces to the front lobe).

18 495.25 CHCH -49.36
64 771.25 CFMT -48.71
44 651.25 CJMT -48.36
43 645.25 WNED -47.64
40 627.25 CFTO -47.13
20 507.25 CBLT -44.86
32 579.25 WNLO -41.42

The next highest is -55dBm. I used tvfool terrain/distance/transmitter data with the hdtv primer CM4221 gain(over freq) data. I estimated a -25dB loss due to side lobes. I think that is only about -32dBm. However, I only did the digital channels. Maybe I will add the analog channels as well (I hope they go off air as per CRTC plans); I guess I might have to accommodate future uses for that band, but filters should be reasonable it that happens.

Thanks,
Bill Pringlemeir.
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post #67 of 311 (permalink) Old 2010-05-02, 02:29 PM
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Quote:
Originally Posted by bpringlemeir View Post
So, off the shelf devices will cost about the same as (or more than) a pre-amp itself. Even the DigiAir Pro is doing more than what is needed. I see that the LTC6405IMS8E has a unity gain at 2.7GHz and a -3dB point of 800 Mhz. If a 75Ohm load was the input in unity gain mode (to OpAmp above) with a diode bridge followed by an RC on the output, wouldn't that give a pretty good voltage estimate over the 800MHz frequency?

I am proposing the same circuit without the mixer in the middle so that the whole ATSC frequency range is used. I guess a high/band pass filter could/should also be used. I think these components might run $20 (and a lot of time to get the right passives and layout). No IC like this exists for the ATSC band for automatic gain control or other uses? I guess AGC is integrated in bigger chips for ATSC.
I think you would be happy with a used signal level meter (SLM) that would allow you to tune each channel and measure its signal power in dBmV.

If you are into building, I suggest a meter based on an RSSI chip. QST had an article (can't put my hands on it right now) for a DIY RF power meter based on such a chip that gave a readout in dBm (down to -77 I think). It didn't have a tuned front-end, so it might be what you need. You could add a tuned circuit or a filter like a HLSJ or a UVSJ to read the band of interest. Take a look at this page:
http://www.qsl.net/n9zia/wireless/appendixF.html
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post #68 of 311 (permalink) Old 2010-05-02, 03:00 PM
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No need to buy a signal meter. Most TV panels provide useable info regarding signal on digital channels...

DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection
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post #69 of 311 (permalink) Old 2010-05-02, 04:41 PM
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bpringlemeir:
I'm not sure if a WIDE-BAND energy detector is what you need, but www.linear.com
reveals the following for TV Freqs:
http://www.linear.com/pc/productDeta...1,C1743,P80944

There is such a commercial device on the market...but since it will be overwhelmed
by whichever channel is strongest at the antenna terminals, it isn't very useful for
tweaking WEAK signal reception:
http://www.tvaerials.com/product.aspx?productid=2158
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post #70 of 311 (permalink) Old 2010-05-03, 08:56 PM
 
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No need to buy a signal meter. Most TV panels provide useable info regarding signal on digital channels...
"TV Panel"????

Seriously, most digital TVs sets have "meters" that are only relevant when compared to another set of the same model. They are not substitutes for a real SLM which provide objective measurements in real-world units.
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post #71 of 311 (permalink) Old 2010-05-03, 09:14 PM
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I don't see how the average consumer would require that information. It the digital world it either works, sort of works, or doesn't work. There are plenty of online tools that assist people in deciding what equipment is necessary to receive a particular station. And AGC's prevent overloading in most cases.

And yes, a panel. Most tv's sold today are panels....

DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection
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post #72 of 311 (permalink) Old 2010-05-04, 10:42 AM
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Quote:
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I don't see how the average consumer would require that information. It the digital world it either works, sort of works, or doesn't work. There are plenty of online tools that assist people in deciding what equipment is necessary to receive a particular station.
I agree if everything always works, there is no need for that information. The problem comes when things aren't working properly. With analog broadcasts you could look at the picture you are receiving to help you diagnose the problem. With DTV, all you get is a blank screen and the tools built into most TVs (or panels as you call them) or set top boxes are only marginally useful as they typically take a bunch of things and combine them together in an unpublished way to give you some sort of idiot proof number or bar graph.

Online tools are great for guessing what you will need ahead of time and can give you clues as to what your problems might be, but there is no substitution for real world measurements for tracking down the true source of your problems.
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post #73 of 311 (permalink) Old 2010-05-04, 11:10 AM
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An accurate signal meter isn't going to diagnose noise/interference issues, or co-channel interference, or other problems that we typically use analog stations for (as a diagnostic tool). And certainly not in the presence of any amplifier.

It really comes down to logic: Where are the stations in relation to my antenna? What is their ERP? What are the online tools telling me in terms of what I should be expecting in signal level?

And when you pull all of that together, you should have a clear picture of whether or not a given amplifier with a given gain will cause overload or not. These are variables an OTA enthusiast should be aware of anyways...as it's necessary when making equipment selection decisions.

Would it be nice to have a signal meter in a completely digital world? Perhaps. Would it help in resolving all reception issues?! I don't believe so...

Probably the best tool to have in the arsenal is a multimeter to test continuity and resistance. By correctly OHM'ing out a cable run, you can even determine (within approximate distance) where a fault--if present--is located.

DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection
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post #74 of 311 (permalink) Old 2010-05-05, 11:27 AM
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TSReader Lite (FREE version) displays SNR and packet error statistics at SNR levels well below "lock",
making it easier to align an antenna when it isn't yet optimally aligned...also gives you a feel for
whether you are "close" to getting reception.....

Unfortunately, TSReader Lite only works with a relatively small number of USB Tuners:
http://www.tsreader.com/tsreader/index.html
http://www.tsreader.com/tsreader/hardware.html
Be sure you are looking in the "Terrestrial (ATSC)" hardware section....
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post #75 of 311 (permalink) Old 2010-05-05, 09:26 PM
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yep, tsreader is awesome for that.

I find the evga usb tuner i have won't lock at all below a 14.5 dB c/N threshold. And I've posted it's C/N vs Quality % readings as read in TsReader.

On the other hand, an ATI Wonder 650 USB Tuner will attempt to lock below
the usable threshold, but it's C/N Readings are all screwed up and don't correlate to anything that makes sense. Mainly from the interpretation
in the BDA ATSC .DLL's Source Code.

I've posted about that anomoly around here someplace as well.
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