Odd TV Signal Problem - Turned out to be HDR FoxT2

I agree about RF being black magic! How multi-gigahertz processor PCBs work is beyond me - in my day we never went above a few megahertz.
 
Black Hole said:
I agree about RF being black magic! How multi-gigahertz processor PCBs work is beyond me - in my day we never went above a few megahertz.
Click to expand...

The thing that blows my mind is increased bandwidth using MIMO antennas. I can get 450mbits instead of 150mbps using 3 antennas rather than 1 (this works with my home wifi). But all three antennas are using the same frequencies, they're only seperated in space (not frequency or time). Surely this breaks the laws of physics?
 
Owen Smith said:
(Hence more water in the tree to attenuate the signal.)
Click to expand...
Water doesn't have any significant effect at terrestrial TV reception frequencies.
And as I said in a previous post, perhaps your cable has developed a fault?

Or your aerial, if it's an outdoor aerial they don't last forever in the weather. The connections inside may have become water penetrated or corroded.
Click to expand...
One of these is where my money is. Just because it worked until now doesn't mean it hasn't been deteriorating for ages.
That's the bad side of digital modulation.

Anyway, the change in the weather in the next few days might make some difference if it is atmospherics.
 
prpr said:
Water doesn't have any significant effect at terrestrial TV reception frequencies.
Click to expand...

Yes it does. Otherwise, how to you explain trees growing vigourously in spring affecting reception, or water penetrated coax attenuating high channel numbers more than low?
 
Owen Smith said:
Yes it does. Otherwise, how to you explain trees growing vigourously in spring affecting reception
Click to expand...
That's an obstruction. A wet obstruction is the same as a dry obstruction.
or water penetrated coax attenuating high channel numbers more than low?
Click to expand...
You moved the goalposts.

Water in free space (AKA heavy/torrential rain) does not affect terrestrial reception.
 
prpr said:
That's an obstruction. A wet obstruction is the same as a dry obstruction.
Click to expand...

So why in summer when the leaves are still on the trees but they're not growing as vigourously (and hence not as wet) are the leaves on trees much less of a problem? This is well docomented on many reception advice sites, trees growing in spring causing problems but not an issue in summer.
 
Just reseating the connectors in the final link has got me:

Ch23 50/100
Ch26 51/100
Ch48 57/100
Ch49 58/100
Ch52 48/100
Ch54 42/100
Ch56 36/100
Ch58 30/100

The HiDef services (Ch58) have always been a bit glitchy at this end of the wire, so I reckon I'm back to where it was before - never ignore the simple things!

The drop-off at the higher frequencies might be something to do with my distribution network, and could be endemic or a result of deterioration, but it could also be something to do with the aerial group. I have no idea what groups the aerials are, they were here when I arrived 25 years ago, and the last berk had a horizontal aerial pointing at a vertical transmitter.

Case solved, although re-addressing the aerial network is on my long-term to-do list.
 
Do the high channels drop off the same on your other boxes running from the same aerial? If not then it's not the aerial, it's the distribution system.

As for cables, I hate Belling Lee style UHF connectors (the ancient standard for TV in the UK). My entire system is cabled on double screened CT100 (many years ago) and all the wall plates and cables use F connectors. Then in the back of the boxes UHF inputs I have F to Belling Lee converters, this avoids the need for me to manually wire up rubbish Belling Lee.

The great thing about hand made CT100 fly leads from the wall socket is I can have exactly the length I need without spare cable sprawling all over the place.
 
Owen Smith said:
Explain please, why is water penetrated coax not the same as water in free air? (Capacitance perhaps?)
Click to expand...
Rain doesn't corrode the inside of the cable, nor affect its dielectric which stops it performing as designed and increases attenuation and HF loss.
 
prpr said:
Rain doesn't corrode the inside of the cable, nor affect its dielectric which stops it performing as designed and increases attenuation and HF loss.
Click to expand...

So what does rainwater do to a cable when it penetrates and creeps all along the cable then? It does something that attenuates high frequencies.

And if it doesn't corrode, what turned the cabled I opened up green along the entire length?
 
Owen Smith said:
So what does rainwater do to a cable when it penetrates and creeps all along the cable then? It does something that attenuates high frequencies.

And if it doesn't corrode, what turned the cabled I opened up green along the entire length?
Click to expand...
That's exactly what I was saying water in the cable DID do, and which rain DID NOT.
 
I think we're misunderstanding each other, leading to violently agreeing. It happens. He said rain, I assumed that meant rainwater in the cables. I think we've got it straight now.

Edit: for the avoidance of doubt, I believe it is: rain when it is in the act of falling out of the sky does not affect terrestrial TV reception. But that same rain, when it becomes water in the cable, attenuates high frequencies and does affect terrestrial TV reception.
 
Trev said:
Do you mean that rain when in the act of falling out of the sky is NOT water?:frantic:
Click to expand...

Now you're being awkward. Prpr seemed to be confused by my calling it rain when in the cables, since by then it isn't falling out of the sky any more,
 
;-) good chuckle through the thread

I'm glad black hole is sorted like me without resorting to Spider-Man antics to get to the aerial, I was so close to checking no 'sky water' had penetrated to where the cable connects to the aerial as in our last house which was infinitely easier being a bungalow on a hill.

I had enough ladder to get to the aerial and enough space to crawl underfloor so replaced the lot.... Then moved!


Sent from my iPhone using Tapatalk
 
You must log in or register to reply here.
Back
Top