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rabbit73
22-Oct-2019, 11:50 PM
A post by ckwsp101_tv gives a very useful chart that converts SiliconDust Signal Strength % readings to dBmV

https://forum.tvfool.com/showpost.php?p=62282&postcount=33

Found on SiliconDust forum

SS% dBmV
0% -60 dBmV
5% -57 dBmV
10% -54 dBmV
15% -51 dBmV
20% -48 dBmV
25% -45 dBmV
30% -42 dBmV
35% -39 dBmV
40% -36 dBmV
45% -33 dBmV
50% -30 dBmV
55% -27 dBmV
60% -24 dBmV
65% -21 dBmV
70% -18 dBmV
75% -15 dBmV
80% -12 dBmV
85% -9 dBmV
90% -6 dBmV
95% -3 dBmV
100% 0 dBmV


I decided to invert the chart, putting 100% at the top. I first learned how to measure the strength of TV signals in microvolts with an old borrowed Sadelco meter.

http://i.imgur.com/ch7LDqQ.jpg

I next bought a meter that read in dBmV which used the 0 to -30 scale.

https://forum.tvfool.com/attachment.php?attachmentid=3547&d=1572033639

An then, I had to learn how to use Noise Margin and dBm values that were in TVFool reports:


SiliconDust HDHR Signal Strength Conversion Chart

SS% dBmV dBm
100% 0 dBmV -49
95% -3 dBmV -52
90% -6 dBmV -55
85% -9 dBmV -58
80% -12 dBmV -61
75% -15 dBmV -64
70% -18 dBmV -67
65% -21 dBmV -70
60% -24 dBmV -73
55% -27 dBmV -76
50% -30 dBmV -79
45% -33 dBmV -82
40% -36 dBmV -85
35% -39 dBmV -88
30% -42 dBmV -91
25% -45 dBmV -94
20% -48 dBmV -97
15% -51 dBmV -100
10% -54 dBmV -103
5% -57 dBmV -106
0% -60 dBmV -109


Comment by Calaveras:
https://www.avsforum.com/forum/25-hdtv-technical/3087874-600mhz-lte-filters-lpf-600-substitutes.html#post58705364
The HDHR shows 100% Signal Strength at 0 dBmV or -48.75 dBm and greater. The TV dynamic range runs up to around -8 dBm or 40 dB stronger. It's too bad they chose to set 100% to 0 dBmV because it's not helpful in seeing how strong a signal really is. In many cases 100% on the HDHR is no problem at all for the TV tuner.
The latest unit is dBuV/m (dB microvolts per meter) field strength in reports from rabbitears.info.

https://en.wikipedia.org/wiki/Decibel

dBμV/m, dBuV/m, or dBμ
[57] dB(μV/m) – electric field strength relative to 1 microvolt per meter. The unit is often used to specify the signal strength of a television broadcast at a receiving site (the signal measured at the antenna output is reported in dBμV).
The field strength of the signal is just before it touches the antenna. The signal at the output of the receiving antenna is measured in dBμV or dBmV (which can be converted to dBm), which are measurements of signal power.

SiliconDust HDHR Signal Strength Conversion Chart

SS% dBmV dBm NM dB* dBuV/m**
NA 40 dBmV -9 82 121
NA 30 dBmV -19 72 111
NA 20 dBmV -29 62 101 Signal strength is important but
NA 10 dBmV -39 52 91 the goal with HDHR readings
100% 0 dBmV -49 42 81 is to maximize Signal Quality
95% -3 dBmV -52 39 78 (SNR) and have 100% Symbol
90% -6 dBmV -55 36 75 Quality
85% -9 dBmV -58 33 72
80% -12 dBmV -61 30 69 Conversion factor used for
75% -15 dBmV -64 27 66 dBmV to dBm: -49
70% -18 dBmV -67 24 63
65% -21 dBmV -70 21 60 Conversion factor used for
60% -24 dBmV -73 18 57 dBm to NM: +91
55% -27 dBmV -76 15 54
50% -30 dBmV -79 12 51 Conversion factor used for
45% -33 dBmV -82 9 48 UHF dBm to dBuV/m: +130
40% -36 dBmV -85 6 45
35% -39 dBmV -88 3 42 Signal Margin in a rabbitears
30% -42 dBmV -91 0 39 report is similar to Noise
25% -45 dBmV -94 -3 36 Margin in a TVFool report
20% -48 dBmV -97 -6 33
15% -51 dBmV -100 -9 30 * NM (Noise Margin)is used in
10% -54 dBmV -103 -12 27 TVFool reports
5% -57 dBmV -106 -15 24 ** dBuV/m is used in reports
0% -60 dBmV -109 -18 21 from rabbitears.info
rabbit73 Oct 25, 2019
**dBuV/m is an approximation valid for UHF signals. Report values
for VHF have a negative correction factor applied to allow for higher
noise levels on VHF. This ranks VHF signals lower in the report.

The last two attachments are the same chart. The Chart4-120.JPG is a little larger because it is at 120% of a BB code image in a post.

This is the Chart5-115 image for comparison with the original code image above:

https://forum.tvfool.com/attachment.php?attachmentid=3551&d=1572044127

rabbit73
3-Nov-2019, 1:39 AM
After making the chart above, I started to wonder about the accuracy of the signal strength readings given by the HDHR tuner. I have never used an HDHR tuner, so I ordered an HDHR4-2US Connect Duo to make some tests.

When it came, I connected it to my Windows 7 laptop with a network cable. I went to my.hdhomerun.com which told me there wasn't a tuner connected, so I couldn't immediately download the software. I then went to the SD website and downloaded the software. I still wasn't able to connect until I entered the correct IP address in my network adapter and changed settings in my Norton software. I'm not a software expert, so this was becoming much more difficult than turning on a TV and going into the menu.

I set up the tuner and my 32" Sony TV with a splitter so that I could compare tuner sensitivity and signal readings. I picked my strong channel 33 to check the 100% signal strength reading of the HDHR and my marginal channel 9, that has just barely enough SNR above the noise, as test signals.

My 32" Sony KDL32R400A is a little different than most other Sony models. Its signal strength indicator goes all the way up to +41 dBmV (-8 dBm) at 100% instead of maxing out at 0 dBmV for 100% as most other TVs. Each step on the scale is one dB and I calibrated it with my signal level meter so that it can be used for tests like this.

https://i.imgur.com/USrn73K.jpg

I adjusted a step attenuator before the splitter so that the HDHR SS was 100%:
HDHR Signal Strength 100%, Signal Quality 98%
Sony TV SS 62 (+3 dBmV), SNR 28-29 dB

So the HDHR 100% was pretty close to 0 dBmV, considering my measurements aren't lab grade.

My marginal channel 9 signal looks like this; just barely enough SNR above the noise:

https://i.imgur.com/ffD8rlD.jpg

I adjusted the attenuator to make the signal weaker at the "Digital Cliff" to see which tuner would drop out first. To my surprise, the Sony tuner dropped out first; the HDHR tuner is more sensitive than I expected. It was still giving reliable reception at 50% Signal Quality.

https://forum.tvfool.com/attachment.php?attachmentid=3561&d=1572747217

At 49% Signal Quality, the Symbol Quality often dropped down into the red at lower readings:

https://forum.tvfool.com/attachment.php?attachmentid=3562&d=1572747230

and finally dropout:

https://forum.tvfool.com/attachment.php?attachmentid=3563&d=1572747239

mikecandu
28-Jun-2020, 4:47 PM
Hi,

I get similar results with my HD Home Run connect. As long as the signal strength is at least 50% and the SNR is 50% or above (yellow colour) the station is watchable. IF SNR drops below 50% (red) it is unwatchable.

My new(ish)Samsung 4K TV UN65MU&000FXZC does have a slightly more sensitive tuner then my HD HomeRun. My old Bell Satellite Box 9242 has a less sensitive tuner.

All of these are fed from the same rooftop antenna through a 4 way splitter.

Mike