menuMENU    UK Free TV logo Archive (2002-)



Click to see updates

All posts by c/s GBXZ

Below are all of c/s GBXZ's postings, with the most recent are at the bottom of the page.

Hi all, 1st post for me here.

I'm possibly looking to build my own antenna, probably Log Periodic to keep it simple) for a loft install (unavoidable I'm afraid) in the Chatton service area.
Looking at the "after switchover" section the 3 future/proposed multiplexes are at/below the bottom of the group. Not being "in the TV trade" (though with 25 years of RF engineering) - MY QUESTION IS:
Q: Will the proposed Com7/8/9 Multiplexes ever materialise?
Reason - If I can concentrate the antenna design on a higher group of channels I can get more gain and a tighter pattern on my (maximum) 2 metre boom length.

My location is down below a huge masonry building from the TX site and there's a very strong Tetra base 60-70 metres away at 10 degrees off my badly-obstructed LOS. The obstructing building is so close and has a sharp enough roof that diffraction of the wanted UHF TV signal may (hopefully) occur.
The Tetra is unfortunately unobstructed, and I'm right in it's vertical beamwidth at loft-level.

Analogue reception from Chatton is not possible at the moment due to the Tetra patterning on the snowy picture (even with some mass-produced Tetra notch filters and AKD/Garex HPFs on the front end) so I'm clutching at straws and not sure exactly how much signal I (don't) have.

It's all commercial properties either side of me so no nearby recent installs to compare to. Most are 60's-era 405line or old beams on Pontop .Not a sausage from there, badly obstructed that way nowadays, picked up nothing before Tetra came to town a few years ago. (I've been on-site here for 15 years but now need TV rx here)
No satellite LOS here for Freesat either :(

I've cadged quite a few few assembled ants from TV trade mates over the last year or two and none have given any joy on any multiplex so far, though it's hard to tell as the front-end of any box is getting so hammered by the Tetra intermod. I fear I may have to fabricate some cavity filters, silver them myself, use an amplifier.

Thoughts anyone?

link to this comment
GB flag
What price for an aerial installation? | Rigger's zone
Saturday 28 January 2012 8:10PM

@Steve P
that was one I'd respond to in years gone by ;)

Can't see the bird/s from any walls or windows :(

link to this comment
What price for an aerial installation? | Rigger's zone
Saturday 28 January 2012 8:20PM

Further my last: "living in a hut in an enclosed yard" - would sum it up nicely.
I'm in a terrace with a deep dark yard to the south, surrounded by taller buildings all round as neighbours,
Across the road is the huge building between the Chatton TX and me.
I've tried a variety of "class 1 benchmark" ants with no joy other than Tetra overload in any direction.
No external antennas, wires, brackets or anything by order of the landlord. The other tennants of the building would grass me up anyways - 'tis fun here.

I love a challenge but this is turning out silly.

link to this comment

Steve P:
Current analogue is nothing at all, it's an old apartment over commercial below, with commercial either side. This building has no ants at all, probably been unused since the 50's.
They neighbouring commercial tenants are all a bit eccentric - far worse than me!

Briantist: Thanks for that.
OK, looks like I'll have to look into making amps and heavy filtering, I just can't get the gain from the wide bandwidth I need in the space I have in the loft.

Part of the loft was planned to be for HF tx kit but isn't useful for UHF on Chatton due to an internal brick wall separating it.

I've already tried all the kit on the market up to the size of the unix-52 and similar with nojoy. Other than phasing a 4 or 8-square array of them (bandwidth far too wide for that if the com7/8/9 are needed) I'm at a loss down the commercial route.

The local riggers (all a friendly bunch) have given up long ago but wishing me the best.

link to this comment
GB flag

Steve P: yes and no, 300m line length from the exchange but on faulty (aluminium) cables so up up is about 600kb/s and down is ok to 800/1400 or so depending on -Max or ADSL2+. ADSL2+ shows a lot of wandering in speed, ADSL1-Max is much more stable. I'm trained to around CCNP/CCIE standard (though not current) so there's not much more that can be done there. No 'cable' or 'fibre' for 20 miles. It's the sync dropouts (caused by the aly underground BT cable that bugger up the 'internetTV' idea, we get about 10-20 a day on a good day, 50-60 on a bad. BTOR have washed their hands awaiting a new pull of cable along the street.
I also "work" from home so anything that fill my personal pipe is unwanted.

Dave: it's not for me - I'm getting nagged (incessantly)

UHF or nuthin haha

link to this comment
GB flag

Steve P: sorry 6000 kb/s peak sync, max throughput depends on time of day and ISP of course (I've been through a few ISPs here over the years). The internet TV option is really a non-starter, I have to pull quite large disk images to work on and they're usually d/l'ded at peak TV viewing times. (thank the Gods for wget)
BT are a mess these days, the repeated cutbacks have left them with a lot of dodgy and undocumented plant and they can't blame the cowboys!

I'm suppose I'm really asking "Is there a off-the-shelf option for this extreme case? If so how much?"

### Summary - 10 miles from Chatton, 70metres from Tetra base, no view of any relevant sats at all. External antennae AND cabling (!) prohibited by feudal tenancy agreement. HUGE high masonry building blocking view of Chatton. Current analogue signal is below the Noise+Tetra. Internet TV not an option. Other half wants channel-hopping telly. MUST be UHF-over-the-air option in loft I think, all other avenues are dead-ends. ###

Anyone here tried GaAsFET amps or large-scale stacking? Is there anything available off-the-shelf? DIY is feasible, I'm an RF guy with 25 years experience and UHF/SHF design skills. I know (all to well) it won't be easy, especially from 560-700+MHz
with that level of Tetra close by (physically as well as in spectrum terms).

I haven't watched TV since Swap Shop myself, so I'm also p!zz3d off about the whole scheme right now.

PS: If any "normal" customers are reading this, it's a perfect illustration why you pay good money to expert riggers. Cowboys are 2-a-penny. Knowledge costs. So does pro kit.

link to this comment
GB flag

Steve P: whoops, that should have been downstream speed is about 6000kb/s and upload is maxed at the 800-odd or 1500-odd depending on ADSL-Max, ADSL2, ADSL2+ etc and premium upload options depending on contract. (The Mole echo looks like a complete mess). Sorry for confusion.

But like I say above, TV and Internet won't mix due to work internet commitments (and the frequent dropouts).

link to this comment
GB flag

barry lloyd:

A couple of main things spring to mind -

1/ THE USUAL CULPRIT IN MOST HOUSES - Overheating in the lounge, but not in the bedroom??? Allow plenty of ventilation around and under it. Don't put it in a cabinet for example, even if it's an open-fronted one (+on top of a TV is a _very_ bad place, both old CRT/glass TVs (heat, strong magnetic fields and static) and new "flat" ones (mainly heat)

To improve ventilation, stand it on 4 empty matchboxes or similar small blocks and make sure the vents aren't blocked with dust.

NEVER cover things like this with ANYTHING. Even a TV remote left on top can make some consumer-grade kit overheat nowadays.

If it lasts longer when better ventilated, prove it by blowing a desk fan over it for a few hours and see if it still locks up.

2/ Some PVR things might get very confused if can't get it's channels correctly - a bad signal corrupting the EPG can sometimes cause the software to hang (*)
Check your wiring - coax leads to the wall aerial socket for example.

Other factors:

3/ occasionally (quite rare nowadays) florescent lights interfere with the infra-red remote control codes. Sometimes the remote control command meant for the TV or VCR/DVD/HIFI might get confused and cause a software hang (*) This fault sucks.
To try to rule this out, tape a piece of card over the infrared sensor on the PVR t shade it from the room light but NOT from the remote. This is almost unheard of nowadays but I've had to do this for a couple of mates recently.

4/ Power glitches can cause lockups - things like kettles, washing machines/dryers, welders and other heavy loads on the same ring-main sockets can cause glitches that may not affect upstairs so much. A "transient protector" can sometimes help, but in some cases a house rewire is in order (!). Very drastic but I have seen it.

5/ Some weird interaction due to leakage currents from the various switch-mode PSUs in the TV/DVD/VCR/etc etc downstairs. Try a different socket, or try a 4-way or 6-way strip and plug everything into it (eg: all TV kit on one socket) to see if it makes a difference. This problem is sometimes manifested by a little electrical "tickle" shock when you plug aerial and audio cables into set-top boxes and PVR/DVD kit whist plugged in, even if on standby. It's a nightmare to explain to a layman, never mind sort out.

(*) this is bad programming, the software _shouldn't_ "lock up" on errors like this. Dream on.

My first guess is heat/ventilation problem, given a change in room helps. Next guess is a confused EPG dues to bad connection in aerial lead downstairs

Good luck.

link to this comment
GB flag

barry lloyd:

also, bear in mind that loft antennae are _always_ a bad compromise, the fact that there's more signal upstairs due to a shorter cable run than to downstairs may be causing the software to get confused, see above ^

link to this comment
GB flag