TV aerial problems

[Guineafowl]

Freeview has been fine until the last couple of weeks. Now, certain channels glitch at times. I’m pointing at the Rosemarkie transmitter, and have roughly checked the bearing (288deg) with a compass. Aerial is horizontal. One of the directors is askew - could that be it?

“Focus, you f*ck!”

Looking at the Rosemarkie broadcast, it seems to be the PSB1/BBCA mux glitching, while the PSB3/BBCB one is fine. I’ll have to catch it glitching again to get more info. So it’s the higher frequency having the problem, suggesting a direction problem, maybe.

I haven’t been right up there, but there should be a reasonable line of sight to the transmitter. I have a basic signal strength meter, but it doesn’t tell me much about quality.

Have tried retuning when all’s well. No good.

Is my aerial an old analogue type, and worth replacing with a digital-ready one, with a filter? If so, which one?
Worth going up and checking the balun connection for corrosion?

Could do without glitching during the six nations

 

[voipio]

Having one director element slightly off isn't going to make a huge difference, unless the TV signals were marginal in the first place. I'd be looking at the cable, and the connection to the antenna first. Also check if there's any sign of water down the coax, as it will cause chaos with cable loss. If the outer braid looks the least bit wet, change the cable.

 

[ajlelectronics]

Is my aerial an old analogue type, and worth replacing with a digital-ready one, with a filter? If so, which one?
Worth going up and checking the balun connection for corrosion?

By eye, that is a good example of the £2 "contractor" aerials, whose only function should have been to fill a skip. Poorly made, no balun, flimsy connectors and a polar diagram like a badger's behind.

There is no such thing as a "digital" aerial. The aerial has no idea and cares less about the modulation method. An ideal replacement would be something from the Televes range on a decent length mast, at least a wavelength higher than its surroundings, ideally more to help with line of sight. Feeder should be a certified type, WF100 is the choice I made for my business a long time ago. Coaxial plugs either Vision branded or Antiference if you can't get Vision.

Alignment is done with a proper analyser for best Bit Error Rate across the band and NOT maximum signal strength. You should be seeing minimum signal levels of 45dBuV and no more than 60 ish. That is where the science of selecting the correct type and gain of aerial comes in.

 

[Guineafowl]

By eye, that is a good example of the £2 "contractor" aerials, whose only function should have been to fill a skip. Poorly made, no balun, flimsy connectors and a polar diagram like a badger's behind.

There is no such thing as a "digital" aerial. The aerial has no idea and cares less about the modulation method. An ideal replacement would be something from the Televes range on a decent length mast, at least a wavelength higher than its surroundings, ideally more to help with line of sight. Feeder should be a certified type, WF100 is the choice I made for my business a long time ago. Coaxial plugs either Vision branded or Antiference if you can't get Vision.

Alignment is done with a proper analyser for best Bit Error Rate across the band and NOT maximum signal strength. You should be seeing minimum signal levels of 45dBuV and no more than 60 ish. That is where the science of selecting the correct type and gain of aerial comes in.

Out of interest, (you might remember I had a brief foray into antenna physics), surely there must be some kind of balun, even on a cheap aerial, to convert the balanced dipole signal to unbalanced coax, and match its 300 ohm to the coax’s 75 ohm? I’d look it up in the ARRL antenna book, but I can’t find it and it’s impenetrable anyway.

I assume it’s like others I’ve seen on cheapie antennas, a wiggly PCB track.

I’ll look into upgrading, thanks.

 

[MoreWellie]

If you have an aerial amplifier/splitter to distribute to different rooms then it is possibly picking up 5G interference, definitely happens to older amplifiers which weren't expecting 5G

I replaced ours with a labgear LDA2081K and it has been fine ever since

 

[ajlelectronics]

surely there must be some kind of balun

Nope. The aerial's driven element terminates inside the connector box with brass pillar screw terminals, one on each leg. That's it! No idea about the headgear of insects though.

 

[ajlelectronics]

If you have an aerial amplifier/splitter to distribute to different rooms then it is possibly picking up 5G interference, definitely happens to older amplifiers which weren't expecting 5G

I replaced ours with a labgear LDA2081K and it has been fine ever since

5G is a technology, not a frequency band. It is highly unlikely that anything made in this Century would be wideband enough to receive and cross modulate enough to cause issues, even Philex junk (who bought the once respected Labgear name). What CAN cause an issue is excess amplification, a trick of many of the wild west installers who always assured the customer that a masthead amplifier was needed, "Ya need a booster mate".
This is why a proper analyser is required to make sure it is all in the right "window" across the band.

 

[Guineafowl]

No idea about the headgear of insects though.

Since showing an interest in this, I’ve thought that ‘antenna’ was a better name - not all aerials are in the air, after all.

If you insist, I’ll stick to ‘aerial’. Honour among pedants, and all that

With no balun, I take it the coax would be radiating somewhat, and there would be losses between the dipole and coax from impedance mismatch?

 

[MoreWellie]

5G is a technology, not a frequency band. It is highly unlikely that anything made in this Century would be wideband enough to receive and cross modulate enough to cause issues

Fair enough, I bow to your superior knowledge
I had a Labgear amplifier/tv signal with glitches that had worked ok for a number of years
I now have an amplifier (sold as "with 5g filtering") and no glitches
Snake oil it may be but at least it solved the issue for me

 

[voipio]

The 800MHz mobile band sits right at the top of the UHF TV broadcast allocation, and is used for 4G mobile networks by most, if not all, of the mobile networks. The antenna in the original posting looks on the "small" side,so maybe optimised for the upper end of the terrestrial TV broadcast band.

Which "channels" does the TV tuner find most of the TV multiplexes?

Channe 21 is at the bottom end (i.e. ~470MHz) whilst channel 60 (~790MHz) would be the current top end of the UK UHF terrestrial TV allocation. 5G can use 700MHz, which could cause issues with TV reception, though I don't think that allocation is for the UK.

 

[MoreWellie]

Actually on checking I see
"In the UK, existing 4G signals sit between 800MHz and 2.6GHz. Whereas 5G will operate at 700MHz and 3.4GHz to 3.6GHz"

 

[OJCar]

You give your location as Nairn and your using the Rosemarkie Transmitter.

Are there any ships "parked" in between you and the transmitter ?

 

[voipio]

You give your location as Nairn and your using the Rosemarkie Transmitter.

Are there any ships "parked" in between you and the transmitter ?

Or oil rigs?

 

[voipio]

Actually on checking I see
"In the UK, existing 4G signals sit between 800MHz and 2.6GHz. Whereas 5G will operate at 700MHz and 3.4GHz to 3.6GHz"

The Rosemarkie digital TV multiplexes are broadcast on UHF channels 39 to 45:

Rosemarkie (Highland, Scotland) Full Freeview transmitter

Freeview HD transmitter: Rosemarkie, Multiplexes: 7, Height: 327.5m/m, Power: 20kW/10kW/kW, Channels: 39/40/42/43/45/46/52, Polarity: Horizontal

ukfree.tv

 

[Guineafowl]

Which "channels" does the TV tuner find most of the TV multiplexes?

Not sure. How would I find out?

You give your location as Nairn and your using the Rosemarkie Transmitter.

Are there any ships "parked" in between you and the transmitter ?

Not that I know of!

Or oil rigs?

Ditto. I’ll have a look when I get up there. Too bloody cold ATM.

 

[ajlelectronics]

Since showing an interest in this, I’ve thought that ‘antenna’ was a better name - not all aerials are in the air, after all.

But most antennae are close to ground level adorning their owners. Using it to mean aerials is a yankism that needs nipping in the bud.

With no balun, I take it the coax would be radiating somewhat, and there would be losses between the dipole and coax from impedance mismatch?

It'll not radiate but it will not be working as a screen, so prone to picking up interference and passing it to the tuner. It is also why the polar diagram goes awry with no balun, the coax becomes part of the driven element.
Pulse type interference is particularly problematic for digital tuners, which is why coaxial cables became mandated for double copper screening.

 

[ukracer]

Freeview has been fine until the last couple of weeks. Now, certain channels glitch at times. I’m pointing at the Rosemarkie transmitter, and have roughly checked the bearing (288deg) with a compass. Aerial is horizontal. One of the directors is askew - could that be it?
View attachment 480046
“Focus, you f*ck!”

Looking at the Rosemarkie broadcast, it seems to be the PSB1/BBCA mux glitching, while the PSB3/BBCB one is fine. I’ll have to catch it glitching again to get more info. So it’s the higher frequency having the problem, suggesting a direction problem, maybe.
View attachment 480045

I haven’t been right up there, but there should be a reasonable line of sight to the transmitter. I have a basic signal strength meter, but it doesn’t tell me much about quality.

Have tried retuning when all’s well. No good.

Is my aerial an old analogue type, and worth replacing with a digital-ready one, with a filter? If so, which one?
Worth going up and checking the balun connection for corrosion?

Could do without glitching during the six nations

Our area is suffering as well. I seem to think it's got worse after the recent big storm we had.

I am thinking either the storm tweaked our ariels or potentially tweaked/damaged the transmitter.

 

[ajlelectronics]

Our area is suffering as well. I seem to think it's got worse after the recent big storm we had.

The usual cause of that is water in the connection box or damaged outer coaxial cable, letting water in that way. Symptoms lessen after a week or two of dry, warm weather which is another clue.

 

[Guineafowl]

aerials is a yankism that needs nipping in the bud.

Consider it nipped!

An aside: I recently described someone as ‘completely p*ssed’. A local girl, 19ish, asked me, ‘why was he angry?’

She had no idea that ‘p*ssed’ means drunk in British English, and angry in American. She thought it was always the latter. Oddly troubling.

 

[ajlelectronics]

Consider it nipped!

Good for you! One local amateur keeps using the plural antennae for the singular, which really gets "on oi teets".

An aside: I recently described someone as ‘completely p*ssed’. A local girl, 19ish, asked me, ‘why was he angry?’

She had no idea that ‘p*ssed’ means drunk in English, and angry in American. She thought it was always the latter. Oddly troubling.

The epidemic of yankisms is getting worse daily. Probably caused by the surfeit of American programming, leading to nonsense like "reach out to us" and the like.