Mux 27 not viewable via pass-through connection to TV

Kirbett

New Member
Over the last month or so, I've been getting increased disruption on some Freeview channels (such as 5 USA) when viewed or recorded later in the evening. I'm still trying to pin down the symptoms, and as a first step I replaced my aerial booster last week with a new one (Labgear LDA204LR), the old one being over 25 years old (my aerial is internal and serves three TVs including the one connected to my PVR, running CF 3.10). And a new problem has emerged, although I can't be sure it wasn't present before I changed boosters ...

I can no longer view Freeview Mux 27 channels (ITV, etc) on a TV (Samsung UE40JU6400) connected to the PVR's pass-through. I've retuned the TV twice. On the first retune, it did not even pick up Mux 27. On the second retune, it picked up Mux 27 but with Signal Quality reported (by the TV) as 0-15% (with Signal Strength 90%).

Nevertheless,
  • I can view all Muxs but 27 (i.e. 21,22,24,25,28) on the TV (when connected to the pass-through
  • I can view ALL Muxs on that TV via the PVR (i.e. when connected to the HDMI)
  • I can view ALL Muxs on that TV when directly connected by cable to the booster
  • And I can view ALL Muxs on 2 other TVs connected by cable to the same booster

I've recorded the Signal Strength / Signal Quality for each of those setups (all using the booster), and they are as follows for Muxs 21, 22, 24, 25, 27 and 28 (all "percentages"):

TV 1 (via PVR pass-thru) .. 94/70-80 .... 92/25-50 .... 94/100 ....... 90/40-60..... 90/0-15 ...... 90/50-80
TV 1 (aerial cable) ............... 91/100 ........ 80/100 ........ 90/100 ....... 82/100 ......... 89/100 ........ 90/100
PVR (aerial cable) ............... 51/100 ........ 47/100 ........ 48/100 ....... 47/100 ......... 45/100 ........ 47/100
TV 2 (aerial cable) ............... 92/100 ........ 93/100 ........ 96/100 ........ 93/100 ........ 93/100 ........ 93/100
TV 3 (aerial cable) ............... 95/100 ........ 92/100 ........ 94/100 ........ 91/100 ........ 92/100 ........ 93/100

I assume the reported difference in Signal Strength between the PVR and the TVs is just down to a difference between those devices of what is considered to be maximum signal strength.

Any ideas on how the Signal Quality of one specific Mux could be affected in this manner?
 

MymsMan

Ad detector
while not ideal you could try Y-splitter to feed the TV from the booster without passing though the Humax.
 

/df

Active Member
If the Y-splitter works I'd be tempted to stick with it. But, is your booster really necessary?

As your booster usage predates the increase in DVB-T/T2 transmission power after closure of the analogue services, is it possible that the new booster is overdriving the signal and you would be better served by a passive splitter?

Although your power readings don't obviously support this, a first troubleshooting step would be from the aerial to the Humax to TV1. With any luck your booster isn't in a distant corner of the loft behind a pile of bat and mouse droppings.
 

Trev

The Dumb One
As above. Shove a splitter in and then, in accordance with the principle of diminishing returns, if it ain't broke then don't try to fix it any more. ;)
 
OP
K

Kirbett

New Member
Well, cycling through V-FORMAT was definitely instructive. TV1 on pass-through reported Signal Quality today on Muxs 21,22,24,25,27,28 respectively as ...

at 576i - all at 100
at 576p - all at 100
at 720p - 100, 100, 100, 100, 40-90, 100
at 1080i - 100,100, 100, 100, 40-60, 100
at 1080p - 100, 60-90, 100, 100, 9-30, 30-70

with Signal Strengths at 91-96 throughout.

So, as suggested, I put in a Y-splitter ahead of the PVR to split off the feed to the TV.

Signal Quality is now 100% to both the PVR and direct to the TV. Signal Strength to the TV has dropped to ~75%, but to the PVR has remained more or less unchanged at 43-50%. So all is well with Mux 27, and given the drop in Signal Strengths I think I'll just leave the booster in.

I'm assuming the increase in Signal Strength after replacing the booster may have provoked the HDMI interference. Would this interference have been within the PVR box or would it have been between the external HDMI and RF cables? Has this been a fault in the FOX T2 from the outset?

As yet, I don't know if this had anything to do with the late-evening disruption that I had previously been experiencing on viewing and recording of 5 USA etc. I've yet to retest if and when that disruption reoccurs.

Thanks, All :)
 

Black Hole

May contain traces of nut
HDMI emits RF noise in the UHF band, and poor screening of the RF and/or HDMI leads combined with them being in too close proximity can obliterate weak signals in the exact frequency band. Changing the V-FORMAT shifts the frequency characteristic of the HDMI emission, and therefore the exact interfering effect it has.

The alternative is to get better leads, particularly the aerial lead.
 

prpr

Well-Known Member
Would this interference have been within the PVR box or would it have been between the external HDMI and RF cables?
The interference is picked up on cheap crap cables. Let's see some pictures of the aerial cables you're using to connect it all together.
My prediction is they are white and flimsy, probably with plastic connectors...
 
OP
K

Kirbett

New Member
Black cable as it happens, but indeed with plastic connectors, and with a big BUT, now I know what's going on, with excess cable on both RF and HDMI coiled together for tidiness! ... My assumptions about the effectiveness of shielding have been seriously challenged :) No longer!
 

everthewatcher

Forum Supporter
My assumptions about the effectiveness of shielding have been seriously challenged :) No longer!
This is why I always make my own flyleads using proper double-screened CF100 cable and metal plugs. Another issue with cheap flyleads can be impedance mismatches causing multiplexes to disappear if the length is right.
 
Top