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OTA Receive Levels for ATSC Tuners


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17 replies to this topic

#1 OFFLINE   bt-rtp

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Posted 06 October 2007 - 11:52 AM

What is the min-max range that the ATSC tuners require ?

I'm in the range of 28 to 32 db.

Does the HR20 have 5th gen ATSC tuners ?
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


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#2 OFFLINE   jdspencer

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Posted 06 October 2007 - 02:40 PM

The signal strength is only one part of the equation. You can have a high signal, but any multipath (analog ghosting) will prevent the tuner from locking on. Others will probably now reply with more sophisticated answers. :)
DirecTV since '96, Waivers for ABC, CBS, NBC, & Fox, HR23-700 & HR24-500/AM21, using ethernet based MRV.

#3 OFFLINE   K4SMX

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Posted 06 October 2007 - 03:01 PM

......Does the HR20 have 5th gen ATSC tuners ?

It has been reported that they have 3rd gen. tuners. I don't know what they gen. are, but they're only so-so, particularly with respect to dealing with multi-path interference to the bit stream.
Stew in Florida

HR21-100 (eSATA: Seagate Barracuda 750gb/Antec MX-1), Mitsubishi LT-46131 (HDMI), Onkyo A/V (optical), Slingbox Pro/WLI-TX4-G54HP
HR20-700 (eSATA: FreeAgent Pro 750gb), Mitsubishi LT-46131 (HDMI), Pioneer A/V (optical)
HR20-700, Mitsubishi LT-37132 (HDMI), Sony A/V (optical)
HR20-700, Mitsubishi WD-65731 (HDMI)
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#4 OFFLINE   bt-rtp

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Posted 06 October 2007 - 03:11 PM

It has been reported that they have 3rd gen. tuners. I don't know what they gen. are, but they're only so-so, particularly with respect to dealing with multi-path interference to the bit stream.



I've also read that they are 3rd gen. Would you happen to know the vendor name of the tuner (LG, Broadcom, etc) I'm trying to learn what the recevier threshold is for it.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#5 ONLINE   litzdog911

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Posted 06 October 2007 - 05:43 PM

Search for Earl's post with his original review and interior photos of the HR20. You might be able to determine what the tuner ICs are.
HD DVRs: HR34-700; HR24-500; (2) HR20-700 + WD eSATA 1TB drive/Antec MX1 case; HR21-700; HR21-200 w/AM21
Receivers: H25-500 HD Receiver; H21-100 HD Receiver
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#6 OFFLINE   Milominderbinder2

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Posted 06 October 2007 - 07:48 PM

What is the min-max range that the ATSC tuners require ?

I'm in the range of 28 to 32 db...

I assume you mean signal %...

This is too low to be able to count on it whether you are getting mutlipath or not.

Here are two of the resources form the HR20 FAQ:

Dozens of Great HD Channels are Just Waiting for You
Adding More HD Channels to Your HR20

To help you more, we need to ask the...

Basic OTA HD trouble shooting questions
1. How far away are the TV towers?
2. Do you have newer RG6 Quad Shield all the way from the antenna to receiver?
3. How long is your antenna cable?
4. How old are the connectors?
5. Are there any splices or crimps?
6. Where is your antenna? Outside? Inside? Where exactly?
7. Any buildings or terrain nearby to cause reflectsions?
8. How high is your antenna?
9. What antenna are you using?
10. Any amplifiers? What ones?
11. Are you using splitters or diplexers?

- Craig

#7 OFFLINE   Stuart Sweet

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Posted 06 October 2007 - 11:26 PM

I would imagine that you would have to have signal percentages over 65 for consistent reception, just as in satellite signals.
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#8 OFFLINE   j2fast

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Posted 07 October 2007 - 07:39 AM

I would imagine that you would have to have signal percentages over 65 for consistent reception, just as in satellite signals.


That's been my experience for the most part; things are fairly consistent starting around 60%+/- (at least for me) and have been rock solid at 65%+.

#9 OFFLINE   jeffshoaf

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Posted 07 October 2007 - 08:24 AM

What is the min-max range that the ATSC tuners require ?

I'm in the range of 28 to 32 db.

Does the HR20 have 5th gen ATSC tuners ?


I think the OTA signal meters are showing signal quality instead of signal strength. Regardless, a reading of 28 to 32 is probably way too low to get reliable reception.

How is your OTA reception with those levels?

#10 OFFLINE   bt-rtp

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Posted 07 October 2007 - 08:50 AM

I think the OTA signal meters are showing signal quality instead of signal strength. Regardless, a reading of 28 to 32 is probably way too low to get reliable reception.

How is your OTA reception with those levels?



I used a RF signal meter. It's called a AutumnWave OnAir GT. It has a 5th gen ATSC tuner and includes a RF power meter. See this URL:

http://www.autumnwave.com/

RF power is measured in decibels (db). My OTA antenna signal strength as indicated on the HR20 is 77% on all stations being received.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#11 OFFLINE   jeffshoaf

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Posted 07 October 2007 - 09:40 AM

I used a RF signal meter. It's called a AutumnWave OnAir GT. It has a 5th gen ATSC tuner and includes a RF power meter. See this URL:

http://www.autumnwave.com/

RF power is measured in decibels (db). My OTA antenna signal strength as indicated on the HR20 is 77% on all stations being received.


Ahhh - that makes a big difference; we all assumed you were talking about the signal level indicated by the signal meters displayed by the HR20.

Actually, dB is a relative measure. Power is actually measured in dBm with the "m" indicating "milliwatt," so dBm is decibels relative to a milliwatt. dB are logarithmic, leading to a 3 dB increase in power being equal to a doubling of power.

That being said, I don't know what a reasonable dBm level for OTA reception is... I just scanned through the HR20 manual and I didn't see any sensitivity specs listed at all.

Regardless, a reading of 77% on the HR20 should give you reasonably reliable reception as long as it's steady. If it's wavering a lot and the weather is decent, then you're probably a victim of multipath.

ATSC receivers are also prone to issues with too strong a signal. I actually improved my OTA reception by adding a splitter. My TV has a newer chipset than my HR20 or my HR10 and seems less susceptible to multipath and overpowering; I have a splitter to split my OTA signal from my antenna between my TV and another splitter. That 2nd splitter is feeding the HR20 and the HR10. I tried various configuration (including no splitters and connecting one device at a time); none seemed to matter to the TV, but the 6 dB drop from the two splitters in my current configuration seems to provide the best feed to the two DVRs.

#12 OFFLINE   Milominderbinder2

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Posted 07 October 2007 - 07:32 PM

I used a RF signal meter. It's called a AutumnWave OnAir GT. It has a 5th gen ATSC tuner and includes a RF power meter. See this URL:

http://www.autumnwave.com/

RF power is measured in decibels (db). My OTA antenna signal strength as indicated on the HR20 is 77% on all stations being received.

Then it is multipath.

Have you looked through these...

Here are two of the resources form the HR20 FAQ:

Dozens of Great HD Channels are Just Waiting for You
Adding More HD Channels to Your HR20

- Craig

#13 OFFLINE   bt-rtp

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Posted 10 October 2007 - 07:26 PM

I discovered that the original ATSC standard called for a minimum carrier-to-noise (C/N) ratio of 15.3 dB. Most 5th generation ATSC tuners are capable of locking on a signal of this strength.

The HR20 has a 3rd generation ATSC tuner and these do not equalize multipath signals very well. I have not been able to determine the vendor of the ATSC tuners in the HR20s yet.

With the Channel Master 4221 4-bay UHF antenna, the receivable signals on my local major network broadcast stations are measured at 25 to 32 dB C/N.

Multipath is present and likely due due to the wide 45 degree beamwidth of the antenna and the close location to the transmitter towers (14.8 miles) resulting in a 77% OTA Antenna Signal reading by the HR20 receiver.

The Antennas Direct SR-15 was delivered and assembled today. It has a 25 degree beam width which should help reduce the effects of multipath. Testing is underway, more results in a few days.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#14 OFFLINE   bt-rtp

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Posted 13 October 2007 - 09:52 AM

Swapped out the Channel Master 4221 for the Antennas Direct SR15 yesterday afternoon.

The signal strength levels measured on AutumnWave onAir HD GT receiver with the 5th gen ATSC tuner do not fluxuate as much as they did with the Channel Master 4221. The receive level fluxuation was the dreaded multipath. The CM4221 has a wider beamwidth of 45 degrees versus the AD SR15's narrower beamwidth of 25 degrees.

The receive levels on all the other channels are about the same except for WNCN at UHF 55, that only transmits at 525 kW. The AD SR15 receives this at 30 db, a increase of 1.5 db versus the CM 4221.

The HR20 also still indicates the OTA Antenna Signal Strength as 77% on all UHF channels, regardless of their receive level. I suspect that the ATSC tuners are being over-driven a little bit. A 3 db attinuator had no effect.

Next Steps: 1.) I'm off to the Rat-Shack to buy a 5 and a 10 db attinuators to experiment with and see if they can raise the levels above 77%. 2.) Prime time viewing of WNCN NBC 17 to observe if my minor pixelation events will be reduced or eliminated.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#15 OFFLINE   bt-rtp

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Posted 13 October 2007 - 03:00 PM

Continued testing the HR20 OTA Antenna Signal Strength meter. Here are the results that depict the UHF receive level in db to the percentage indicated on the display of the HR20 meter.

10 db == 51%
17 db == 71%
20 db == 77%
27 db == 77%
30 db == 77%
33 db == 77%

The ATSC standard specifies that an ATSC tuner must be able to lock onto a signal of 15 db or greater.

The design approach used in the HR20 of displaying percentages for the OTA antenna signal strength is subjective. A software programmer decided the percentage values depicted above for each db levels.

It would be better if the actual db level as measured by the tuner was displayed with the necessary min to max threshold needed to lock on a signal. The meter should also update in real time.

Next Step: To determine just how much signal that the ASTC tuner of the HR20-700 needs to hit 100% on the meter, a Channel Master 7775 Pre-Amp that provides 26 db of gain will be installed.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#16 ONLINE   litzdog911

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Posted 13 October 2007 - 03:47 PM

The HR20 (and other DirecTV satellite receivers with ATSC tuners) doesn't actually read signal strength, but rather signal quality. It's an index based on bit error rate, not signal level. That's why a really strong signal can show low readings, due to overload increasing the digital bit error rate.

It's interesting that most of your signal seem to max out at 77.
HD DVRs: HR34-700; HR24-500; (2) HR20-700 + WD eSATA 1TB drive/Antec MX1 case; HR21-700; HR21-200 w/AM21
Receivers: H25-500 HD Receiver; H21-100 HD Receiver
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Additional equipment configuration details

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#17 OFFLINE   bt-rtp

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Posted 13 October 2007 - 04:09 PM

The HR20 (and other DirecTV satellite receivers with ATSC tuners) doesn't actually read signal strength, but rather signal quality. It's an index based on bit error rate, not signal level. That's why a really strong signal can show low readings, due to overload increasing the digital bit error rate.

It's interesting that most of your signal seem to max out at 77.


Yes, I agree that it is interesting, others have posted the same thing. They report 77% as the norm.

The AutumnWave OnAir GT, a 5th gen ATSC receiver, measures a signal that it is tuned to. It displays it as a "db" value. It does not display a bit error rate, but I wish that it did.

I would also mention that the new, Antennas Direct SR-15 antenna, is 14.8 miles away from the transmitter tower, mounted at 30 feet above ground level on my roof, with a complete line of site (LOS) and no obstructions.

I suppose that it's possible that I have a high Bit Error Rate (BER), but don't think that this is the case here. My TiVo H10-250 measured the ASTC signals in the mid 90 percent for each station. The H10-250 also used percentages like the HR20, so maybe it was a BER based value as well as you described.
HR24-500 with AM21
HR21-200
HR20-700
HR20-100


#18 OFFLINE   donshan

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Posted 16 October 2007 - 04:27 PM

I just unintentionally made a comparison of two HR20-700s (both 0x18a) connected to the same Antennas Direct DB-4 four bay UHF antenna with a splitter and discovered the 77% readings yesterday when I activated a new HR20-700. These meter readings were totally different than readings on the Family Room HR20 I got in June which are in the 98-100% range from the same DB4 antenna splitter. This suggests to me there has been a design change this year in the tuner/meters used in the HR 20-700.

In his talk to Merrill Lynch Sept 17 D* Mike Palkovic Executive VP indicated they had reduced their cost of the HD DVR by $100 in 2007. The first HR20 I got in June to replace the HR10 is on the big HDTV in our family room, which I will label HR20(FR) was made in April 4, 2007. The new BR HR20 was made in July 21, 2007 and will label HR20(BR)is on a smaller wall mount LCD HDTV. The performance comparison below may be of use and I would appreciate any comments:

Some antenna history and comparing the HR10 and first HR20:

Earlier I was using a Channel Master combo VHF-UHF antenna (model 3677) with a CM 7777 preamp for about 5 years. I was able to get our Fox digital station from 66 miles away on VHF ch 8 pm the HR10-250. with signal strengths of 80-85. The four UHF stations about 10 miles away had readings of 80-95 on the HR10. . All stations were in a direction within the 30 degree antenna beam width except one where I needed a wider beam width. Early this year everything changed when the Fox station installed a UHF translator here and started HD broadcasts on UHF 36. . When I upgraded to my first HR20-700 in June I found it did not have the Fox VHF channel 8 listed in the database, but they did support the FOX-HD ch 36. So I decided to switch to an Antennas Direct DB4 and also add a second HR20-700 to our BR. The VHF-UHF 3677 and preamp came down.

I first tested the DB-4 on our FR floor indoors on the HR20(FR) and the meter pegged all five UHF channels at 100% indoors so I had confidence I could eliminate the preamp and add a splitter to run to two rooms.

My son-in-law did the roof work last Saturday, and together we installed the new DB-4 thru a ground block to a splitter in the roof eve and then two cables- one to the Family room HR20 ( Mfg date April 4, 2007), and the second line to the BR to a new HR20 (Mfg date July 21, 2007). We also ran two Belden RG6 for the BR HR20. I was surprised by the initial OTA results. Both tuners in each HR20 have similar readings and all the HR20(BR) readings including some sub channels are rock steady at 77%, whereas the HR20(FR) readings fluctuate a little. The 90 degree beam angle of the DB4 made pointing easy and the values on HR20(FR) went up 10 to 20% vs. the older preamplified CM 3677 indicating both better reception and/or lower multipath:

Ch----------Meter in HR20-700s(FR)Mfg 4/07/07--- Meter in HR20-700s(BR)Mfg 7/21/07

11-1 (actual UHF 36)----98-100---------------------------77
19-1 (actual UHF 18)----98-100---------------------------77
25-1 (actual UHF 26)----99-100-------------------------- 77
31-1 (actual UHF 38)----99-100---------------------------77
42-1 (actual UHF 44)----97-100---------------------------77

My first reaction to the 77% readings was a cable/connection problem or a defective HR20. I did a number of resets without change, and even force downloaded the 0x18a software a second time. However when I put that cable on the HDTV digital tuner I got 100 on all channels. I then connected an indoor Silver Sensor with a different cable to the BR HR20(BR) and again got all 77 readings. It appears that HR20(BR) has a different tuner/meter. To be absolutely sure I should swap the two units, but don't have the time just yet and there is too much good HDTV to watch to mess with it. OTA on both HR20s is very good except when the station has a problem :)
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My Equipment:
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