Optimal Attenuation for HDHomeRun Prime Units

[KeithAbbott]

I am hoping that someone from SiliconDust can answer this question.

I have two Prime units connected to my cable TV service. I use inline coax attenuators to decrease the signal strength going into the Primes, to avoid overdriving the internal splitter/tuner. I am trying to determine the optimal attenuation (3dB, 6dB, etc.) to apply to obtain the highest signal quality.

I have put a software solution in place that queries the active tuners every 60 seconds, and captures signal strength, quality and symbol quality. So I am able to see how small adjustments in incoming signal strength affect the signal quality over time.

From what I can tell, signal strength of -0.5 dBmV or above equates to 100% signal strength. A signal strength of -0.6 dBmV equates to 99%.

If that is true, I would expect that the optimal inline attenuation value would keep the maximum signal strength (over time) at or below -0.6 dBmV, with the average signal strength being as close to -0.6 dBmV as possible.

Is my reasoning correct here? Is there a better way to determine the optimal attenuation? Also, is there a minimum signal strength value that I should be monitoring?

p.s. I sure wish the OTA HDHomeRun tuners could return dBmV levels when queried, that would make fine-tuning signal level(s) so much easier...

[signcarver]

I've always preferred my primes to run a little hot... anything up to +10dBmV should work just fine for anyone but I don't suggest much under 0 though you shouldn't have problems unless below -10dBmV. At one of my locations I typically had to run most stations as hot as +17dBmV as there was a band that was underpowered in the neighborhood that the amplification helped with (note that isn't always the case).

As for OTA typically you would want measurements in dBm not dBmV and such is available on the 4k units with the dev upgrade.

[nickk]

Official spec is -12dBmV to +15dBmV.

-6dBmV (90%) to 0dBmV (100%) is perfect for cable TV.
-12dB (80%) is the official min spec for QAM256.

dBmV measurement - tune a channel in the HDHomeRun app then go to the device webpage http://hdhomerun.local/ - Tuners, Tuner0 - this page will show the power level in % and in dBmV.

[KeithAbbott]

Thank you, nickk and signcarver. Very good information.

So for OTA, would the 4K dev units display dBm on the device webpage, similar to how the Primes display dBmV on the device webpage? My software (see attached) is screen-scraping the dBmV value from the device page. It wouldn't take much of a change to grab the dBm value from the 4K dev unit, if it is being displayed.

https://drive.google.com/file/d/1JIfXOP ... March MTD

[nickk]

Best to pull /status.json

On 4K DEV and TECH models it returns both dBm and dBmV.

[KeithAbbott]

Best to pull /status.json

On 4K DEV and TECH models it returns both dBm and dBmV.

Perfect, that's even better!

[KeithAbbott]

Official spec is -12dBmV to +15dBmV.

-6dBmV (90%) to 0dBmV (100%) is perfect for cable TV.
-12dB (80%) is the official min spec for QAM256.

nickk, can you give me the same info for an OTA 4K DEV unit?