Signal dropouts (signal strength 30% - is this too low?)

[Ian Manning]

My T2 is increasingly losing its TV signal completely (i.e. a blank screen with the "no signal" message), or the picture is breaking up badly. This also causes some scheduled recordings to fail. According to the hidden settings menu I usually have a signal strength of about 30%, although sometimes it reports 0%. It's the same for both tuners. Is 30% too low for signal strength - i.e. should I be looking to get an aerial person in to see what they can do?
My TV uses the same RF feed, but doesn't struggle as badly as the Humax - i.e. the live TV picture never breaks up or disappears. It's a Samsung UE55ES7000. Presumably that's because the TV has a better tuner than the Humax?

 

[Ezra Pound]

Yes, It may be that your signal is on a digital 'cliff edge' where it falls from 30% to 0% in which case increasing the signal strength would be a good idea, I would say 30% is pretty much the lower limit.

It is better to get a stronger signal (with a better aerial) , rather than amplifying the weak signal you currently have, although if used properly an amplifier can also help

The Humax will need a better signal than your TV as it is a recorder

 

[Ian Manning]

Thanks - I'll get someone in. As a matter of interest, what sort of minimum signal level should I expect? I'm in the Greater London area, but the house is at the bottom of a hill :0(

 

[Black Hole]

My T2 is increasingly losing its TV signal completely...

It could be that your aerial is no longer the right group. See https://hummy.tv/forum/threads/refe...nel-numbers-aerial-groups-how-to-choose.9224/

 

[Ezra Pound]

Thanks - I'll get someone in. As a matter of interest, what sort of minimum signal level should I expect? I'm in the Greater London area, but the house is at the bottom of a hill :0(

It's not really possible to say what level you should expect, obviously the nearer you are to the transmitter the higher the signal will be, but even close to the transmitter you may not have 'line of sight' because something is in the way e.g. hills, buildings, trees etc.

Don't aim for 100% signal strength, this is too high, anything in the range 40% to say 80% will probably fix your problem, but don't forget amplifying a bad 30% signal to 80% won't help very much

 

[Ian Manning]

It could be that your aerial is no longer the right group. See https://hummy.tv/forum/threads/refe...nel-numbers-aerial-groups-how-to-choose.9224/

Thanks for the link - interesting stuff. My table includes a couple of minus numbers (30- and 2 - see below, but based on my chart can I assume that I need channels 23 to 55 inclusive, and hence a Group T or Group W aerial?
Is there any way of telling what group of aerial I currently have, without the need for specialist equipment?

 

[/df]

Have a look and compare it according to https://www.aerialsandtv.com/knowle...nds#wideband-v-grouped-TV-aerials-gain-curves (also, consider buying something there). Inspection may also reveal, as I found with one property, that the aerial is not intact, say, hanging off the pole, with no visible effect on reception for some devices.

The Freeview checker recommends Group T or A (some mistake, surely?) with horizontal polarisation for Crystal Palace. Apparently a Group K or even B might be effective as well, depending on the high/low(respectively)-end drop-off.

In London you're quite unlikely to have a signal weakness problem, since the power was turned up after DSO. In your case the checker suggests that you should be getting a good signal and I assume that it knows about hills. Ch 55, which (while it lasts) gets much less power than the others, may sometimes be problematic. You may have a strength problem, especially if an amplifier is involved between the aerial and the sets. Although you're seeing 30%, ISTR the strength measurement can lie when there's no signal to detect -- is that the same on the TV?

You could try temporarily connecting an internal aerial, or a coax plug with a short length of cable and you touching the exposed core at the other end, to check the signal.

 

[Ian Manning]

Hmmm....this is interesting...I finally found the signal strength menu item on my TV - it shows a signal strength of 93:


If I unplug the RF cable from the TV and plug it directly into the Humax, the Humax shows a signal strength of 10%:

Maybe there's nothing wrong with my aerial - maybe it's a Humax problem??

 

[Black Hole]

You've not given like-for-like figures - the TV is on 546MHz, and the Humax is on 482MHz. Looks like a case of being tuned to the wrong transmitter to me.

 

[Ian Manning]

Oh....will an automatic retune fix that? Or is there a way to manually select the transmitter?

 

[everthewatcher]

FWIW stacking up all the attenuators I've got here, totaling 26dB (10+10+3+3) and using Crystal Palace Ch55 (HD), drops the signal strength from 75% to 39% and signal quality is still 100%.

 

[Black Hole]

Oh....will an automatic retune fix that? Or is there a way to manually select the transmitter?

I don't know what the real source of the problem is.

On the HDR-FOX, if you press "OK" while tuned to any particular service then press "i" (info), you will get a pop-up reporting the transmission characteristics for that service - of particular interest is the UHF channel number. Also, on Menu >> Settings >> System >> Signal Detection then press the right cursor, you get a list of the UHF channels currently tuned (also available via WebIF >> Diagnostics >> Mux Info). You can compare that list with what you are supposed to have (see https://hummy.tv/forum/link-forums/freeview-coverage-checker.41/).

Whatever, you can only do a meaningful signal strength/quality comparison between the TV and the Humax if you have them comparing reception of the same mux, because your aerial has an efficiency which varies by frequency (it is necessary to match the aerial pass-band to the range of frequencies in use in your area, as noted in my previous reference), and the various muxes are not necessarily all transmitted with the same power ("local" services tend to be very weak).

As for the tuning procedure, you've been around here long enough shirley. See Things Every... (click) section 2 and http://hummy.tv/forum/threads/hdr-fox-t2-tuning-advice.472/page-2#post-5824.

 

[xyz321]

For the Crystal Palace transmitter 482MHz is UHF channel 22, mux COM5. The PSB3 (BBC B) mux is at 546MHz, channel 30.

 

[Ian Manning]

Ok I just realised that I can change the transponder on the Signal Test menu (doh!), so I changed it to match the one that the TV was using - 546MHz. The Humax is now showing signal strength of 25% - worse than on 482MHz, and worse than the TV's 95% signal strength from the same source
???

 

[Ian Manning]

Sorry I missed Black Hole's previous about the manual tuning procedure. Believe it or not I don't think I've ever come across that before.

So I have a couple of queries regarding a couple of the instructions from that link:

• do I only need to search the 7 channels listed in the "N" column from the Freeview site detailed view?
• my BBC B HD channel is shown as "30-" - is there any significance to the "-"?

...and does the 25% signal strength still suggest that I need to get an aerial person in??

 

[everthewatcher]

Sorry I missed Black Hole's previous about the manual tuning procedure. Believe it or not I don't think I've ever come across that before.

Using it means you don't get any funnies in areas served by two transmitters, as here on the eastern edge of Guildford.

So I have a couple of queries regarding a couple of the instructions from that link:

• do I only need to search the 7 channels listed in the "N" column from the Freeview site detailed view?

Assuming Crystal Palace, which is what I'm using, the current channels are:

SD C22 C23 C25 C26 C28-
Local C35
HD C30- C55

That's eight by my count.

Note that C55 is outside the frequency range of Group A aerials that were originally needed for CP so expect the signal to be lower than C22-28. Here with a Group AB aerial the figures are 89% vs 81%, and 74% for C55.

• my BBC B HD channel is shown as "30-" - is there any significance to the "-"?

Yes, but nothing to worry about.

...and does the 25% signal strength still suggest that I need to get an aerial person in??

As as above here in Guildford I'm getting 89-90% on the SD multiplexes with a 15dB (?) masthead amp that's no longer needed. Without it would drop to around 75%.
25% is very low - almost what I'd expect with no aerial at all - so something is wrong.

If you do get someone in and the aerial needs replacing, get a decent log periodic aerial. They're wideband so will cover any frequency used for DVB and are smaller/neater so have a much lower wind loading than the equivalent gain Yagi.

 

[Ian Manning]

OK I've now completed a manual retune but things don't look much different. If the TV reports 95% signal strength from the same source then can I assume that there's nothing wrong with my aerial?

 

[Black Hole]

• my BBC B HD channel is shown as "30-" - is there any significance to the "-"?

That means the actual frequency is slightly lower than the nominal frequency for UHF channel 30. Receivers set to channel 30 will still lock onto it, and it is typically used to reduce co-channel interference from another transmitter.

...and does the 25% signal strength still suggest that I need to get an aerial person in??

The only thing that can be said for sure is that the TV seems to be getting an adequate signal for its own needs.

The only reason for using the signal test on the service menu is if you suspect only one tuner is working (and clearly they are giving the same performance). So far as I know there is no option in the service menu version to change the UHF channel for the test. Using Menu >> Settings >> System >> Signal Detection doesn't offer a choice of tuner - but does allow you to survey all the tuned muxes. I recommend you do that, and get a feel for signal strength over the whole band (and I'm sure we don't need photographic evidence - just the figures).

What you need to look at is the figures when the signal is dropping out (as you describe it) - the quality won't be 100%.

can I assume that there's nothing wrong with my aerial?

"Nothing wrong" is not the same as "good enough". Your HDR-FOX appears not to be getting enough signal for what it needs (as opposed to what the TV needs), so...

 

[everthewatcher]

OK I've now completed a manual retune but things don't look much different. If the TV reports 95% signal strength from the same source then can I assume that there's nothing wrong with my aerial?

Ah, knew I should have read the full thread.

Are you using exactly the same setup for TV and HDR? In other words are you just moving the flylead connector from TV to HDR?

 

[everthewatcher]

So far as I know there is no option in the service menu version to change the UHF channel for the test. ...

Oh yes there is - I'm looking at it now.