Optimal Attenuation for HDHomeRun FLEX 4K DEV Units

[KeithAbbott]

I am hoping that nickk or someone from SiliconDust can answer these questions.

I just got my shiny new FLEX 4K DEV today, and am looking for help with what the official spec and optimum dBmV range is for OTA. Similar to this post from a couple of weeks ago, but for OTA instead of cable:

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.

Also, is there a benefit to using dBm instead of dBmV to adjust signal strength to optimal settings? My preference would be to use dBmV, to be consistent with my HDHomeRun Prime units.

Bonus Question: Is there any way visually to tell a FLEX 4K DEV from a FLEX 4K?

[nickk]

The range for antenna is much wider but also fuzzy as it depends a lot on what else is being broadcast (how many TV frequencies and at what relative strength, FM being broadcast, LTE, etc)

[KeithAbbott]

I just realized I forgot to include in my original post that I will only be using ATSC 1.0 for the foreseeable future, not sure whether that factors into the equation or not.

So if a signal strength range is hard to determine, should I at least be trying to keep the signal strength to 0dBmV or lower, similar to the Prime? Or is it not that straightforward either?

Any other guidelines or rules of thumb that I should be aware of?

[nickk]

I just realized I forgot to include in my original post that I will only be using ATSC 1.0 for the foreseeable future, not sure whether that factors into the equation or not.

So if a signal strength range is hard to determine, should I at least be trying to keep the signal strength to 0dBmV or lower, similar to the Prime? Or is it not that straightforward either?

Any other guidelines or rules of thumb that I should be aware of?

The signal level basically doesn't matter for broadcast TV until it impacts signal quality.

ie if signal quality is good call it good. If signal quality is poor then signal strength information can hint at what to look at.

I had a mast-head amplifier down to a 4 way splitter out to 4 pieces of equipment. After a few years the mast-head amplifier died so to confirm I bypassed it. The result - signal strength dropped on all channels, signal quality went up.

[KeithAbbott]

OK, so it looks like I've been looking at this the wrong way. For OTA, instead of optimizing SignalStrengthDBmV, I should be optimizing SignalQualityDB. Is it safe to assume that higher SignalQualityDB is always better? Is it also safe to assume that if signal strength is too high and ultimately overdrives the internal splitter/tuner, that signal quality would drop as a result?

[nickk]

OK, so it looks like I've been looking at this the wrong way. For OTA, instead of optimizing SignalStrengthDBmV, I should be optimizing SignalQualityDB.

Perfect.

Is it safe to assume that higher SignalQualityDB is always better?

Yes. It is a measurement is how close to ideal the signal is.

Is it also safe to assume that if signal strength is too high and ultimately overdrives the internal splitter/tuner, that signal quality would drop as a result?

Yes. It may not even be the channel you are looking at that is the cause.

[KeithAbbott]

I have a Televes SmartKom antenna combiner/amplifier, and recently upgraded my UHF antenna. After I installed the new antenna, I kept all of the same SmartKom settings as before and was a little disappointed in the performance of the new antenna. So I decided to have the SmartKom rescan the antennas, which selects what it thinks is the best antenna for each channel, and the best overall signal strength. I was surprised to see that it picked a much higher overall signal strength level (25 dBmV) for my UHF and VHF antennas. As a result, the signal quality increase has been substantial! Now I can start fine-tuning each channel for optimum performance.

Which brings me to my first question. Is there a maximum recommended signal strength (dBmV) that I should be feeding my Flex 4K DEV units? If so, I would keep it at or below that maximum; I don't want to create any short-term or long-term hardware problems by overloading the circuitry.

And my other question, which is related: does the Flex 4K DEV model show signal strength (percent & dBmV) coming into the internal splitter, or coming into the tuner? Or perhaps there is no signal level difference between those two...

p.s. I sure wish the dBmV values for the Flex 4K Dev had a resolution to one tenth of a dBmV, like the Prime does. Possible future firmware enhancement?

[nickk]

Which brings me to my first question. Is there a maximum recommended signal strength (dBmV) that I should be feeding my Flex 4K DEV units? If so, I would keep it at or below that maximum

It depends on how many channels you have in your area (total spectrum power)
Overloading won't damage anything but will reduce signal quality and make reception worse, possibly on other channels. as well.

And my other question, which is related: does the Flex 4K DEV model show signal strength (percent & dBmV) coming into the internal splitter, or coming into the tuner? Or perhaps there is no signal level difference between those two...

At the RF input. The signal strength reporting for each tuner is calibrated during production test.

p.s. I sure wish the dBmV values for the Flex 4K Dev had a resolution to one tenth of a dBmV, like the Prime does. Possible future firmware enhancement?

Where are you seeing that? I will get it changed.

[KeithAbbott]

p.s. I sure wish the dBmV values for the Flex 4K Dev had a resolution to one tenth of a dBmV, like the Prime does. Possible future firmware enhancement?

Where are you seeing that? I will get it changed.

When I go to the http://192.168.1.xx/status.json page, the returned SignalStrengthDBmV field only returns an integer value. That's on firmware version 20240506.

[KeithAbbott]

p.s. I sure wish the dBmV values for the Flex 4K Dev had a resolution to one tenth of a dBmV, like the Prime does. Possible future firmware enhancement?

Where are you seeing that? I will get it changed.

Any word yet on whether the firmware can be updated so that the Flex 4K Dev will return one tenth values instead of just integers? If so, is there a timeline for this to happen? Also, if it can be updated, would it just be a normal firmware upgrade, or something different (due to it being a dev model)?

[nickk]

It has been implemented. Beta release should be out in a little over a week.

[KeithAbbott]

It has been implemented. Beta release should be out in a little over a week.

Fantastic! Thanks so much. Sounds like it will just be a firmware upgrade, I'll keep an eye out for it.