Wall socket from UHF has F connector; TV has Belling-Lee input. Any impedance issues?

Forums › Freeview (DVB-T/DVB-S) › Wall socket from UHF has F connector; TV has Belling-Lee input. Any impedance issues?

xarqi

727 posts

Ultimate Geek

#106715 30-Jul-2012 14:14

A neighbour's house is sprouting antennae: old VHF, new high-gain UHF, and a sky dish (but no decoder/subscription). I've been asked to see what I can do as their reception is crap. I haven't had a look inside yet, but already I know I need a bit more information from the community here, if you please.

I'm expecting that they are hooked up to the VHF at the moment as they don't report being able to get Prime, and other channels are noisey mush. I'm also expecting to find F connectors on the wall sockets both for the lead from the dish/LNB and from the UHF antenna. The presence of a high-gain UHF implies to me that at some time an effort was made to get Prime, and so even though we are in a marginal area of Auckland for Freeview-HD reception they may be able to get it even if I can't.

Now, here's the deal. They are planning to get a new telly, probably with a built-in DVB-T tuner. If theirs is anything like my newish 50V20, it'll have a Belling-Lee type connector on the back, but the wall connection is likely to be an F type.

Doing a bit of reading reveals that the Belling-Lee connector may not be suitable for use with 75 ohm impedence cables, yet my Panasonic book implies strongly that it is.

So, I have a few qualms about just making up a cable with a Belling-Lee on one end and an F on the other, and hoping for the best, even though I see such cables on sale from the likes of Dick Smith (but just about nobody else).

What's the real story?

(I didn't have this issue myself as my reception is via DVB-S with F connectors, then via HDMI and my AVR to my telly. If it turns out that the neighbours CAN get DVB-T, I may explore that option too, but if it turns out that they CAN'T, they too will end up with an F-connector equipped STB.)

Thanks for reading, and any help proffered.

Jaxson

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#664000 30-Jul-2012 14:21

No worries, TIVO for instance comes with a belling lee to F connector cable as their aerial input is an F connector style. Jaycar etc used to offer conversion adaptors if you don't want to rewire anything.

I'd be tracing the UHF aerial connection, see where that goes. If it goes into a UHF/VHF diplexer then I'd move to dump that and create a single run from the UHF aerial only into the TV. Check if they have any other analogue TV/VCR's etc connected that still require a VHF signal though. Hopefully they don't.

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xarqi

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#664015 30-Jul-2012 14:37

Thanks for that, it was the answer I was hoping for.

That's the strategy I had in mind too. The UHF and VHF antennae are on opposite corners of the roof, so I suspect that they are quite discrete installations (that is, a cobbled together botch up with all sorts of "legacy" components). I doubt if the signals are diplexed.

I think they are running on the VHF, so my plan is to see if I can pick up Prime once I find where the UHF terminates inside. If I can, then the next thing is for them to get a new telly, and we'll have a go at Freeview-HD, and in the interim they can stay on the VHF system. If I can't get Prime, I'll still have a go at DVB-T when they get their TV, but if there's still no joy, I'll just give them a basic DVB-S STB I've got floating around.

I asked if they were interested in recording anything - answer was no, so I'm picking no VCR or DVD-R that would need to retain VHF. In any event, they'd have to make the jump before long anyway, when VHF goes quiet.

sbiddle

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#664110 30-Jul-2012 17:21

Freeview spec says that devices need to come with a Belling Lee connector, purely for legacy reasons. F connectors are the way to go and there aren't any impedence issues.

xarqi

727 posts

Ultimate Geek

#664115 30-Jul-2012 17:27

Thanks for that confirmation and clarification. Much appreciated.

xarqi

727 posts

Ultimate Geek

#667779 5-Aug-2012 13:52

Progress!

Long post, sorry, but I like to provide a lot of detail up front.

---

Executive summary:
Up and running on DVB-S.
VHF is thoroughly knackered.
UHF installation is a bit shabby and has a mystery box on the mast needing identification - no signal yet, but I may never actually have tried it as I misidentified where the cable went!

---

Up and running with the el-cheapo DVB-S box using the existing ex-Sky dish/LNB. There were a few moments of anxiety when I could get nothing at all, even tweaking the IF a bit, but then, an intermittent signal came through, and then it settled. Not great levels - about 65% for strength and quality, but good enough. I put the intermittent business down to some water somewhere in the system that got boiled off once power was applied!

I got on the roof anyway to check exactly where the leads from the various other antennae went, and noticed a few things of interest. The LNB is a dual throat one with four outputs, two of which have cables to the house; I'd previously misidentified one of them as coming from the UHF, so they should be able to put another box and TV downstairs too. The LNB does have a few water drops visible inside it, so it may or may not last, and my theory about the intermittent signal does seem to hold water, as it were.

The VHF/UHF antenna is completely stuffed. Pointing down into the bush with busted elements and a cable that has splits in the insulation. It terminates in a TV/FM diplexer plate (that I also thought may have come from the UHF antenna).

On the UHF side, the antenna (maybe 2+ m long - dozens of elements) is not in as good repair as I thought initially, being quite lichen-encrusted. There is a box on the mast, a Kingray product of some sort - I'm thinking a splitter. It has no model number I can see. Squarish, about 10cm x 10cm x 4 cm, mostly a beige colour with a mid-gray front. Three socket in the bottom: one from the antenna, one to the house and one plugged and unused. Is it indeed a splitter?

I'm thinking that maybe this was a Sky UHF installation, rather than an attempt to get Prime or DVB-T.

So, they are quite happy with the DVB-S box, but are probably going to get a new telly with a DVB-T tuner. At that stage I'll have another crack at getting DVB-T now I know where the UHF cable actually terminates inside. I could try to get Prime on analogue now (I don't have a DVB-T STB), but that won't tell us much either way or change the TV purchase plan or the ability to get DVB-T when that day comes. What may be important is figuring out what the box on the mast is, so any pointers would be appreciated. Also, can someone clarify if masthead amps can be powered via coax, or do they have to have a separate power line and input. If they can be powered via coax, maybe what they've got is an amp, or amp/splitter. In which case, does just plugging it in to a telly power it, or should I be looking for another box inside somewhere?

Thanks.

B1GGLZ

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#667824 5-Aug-2012 16:14

xarqi: Progress!
Also, can someone clarify if masthead amps can be powered via coax, or do they have to have a separate power line and input. If they can be powered via coax, maybe what they've got is an amp, or amp/splitter. In which case, does just plugging it in to a telly power it, or should I be looking for another box inside somewhere?

Thanks.

It may indeed be a masthead amp.
If you open it up you should find out.
They are powered by the co-ax and I think Jaycar still has power supply plugpacks for them.
You could try bypassing the Kingray box with a new length of co-ax and see what happens. If you can then get Prime on analogue, Freeview should be OK.
Have you tried inputting your address on the Freeview site to see if your area is OK?

B1GGLZ

1961 posts

Uber Geek

#667826 5-Aug-2012 16:16

xarqi: even though we are in a marginal area of Auckland for Freeview-HD reception they may be able to get it even if I can't.

Just re-read original post.
Sounds like an old Sky UHF installation that needed a masthead amp.

xarqi

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Ultimate Geek

#667860 5-Aug-2012 17:23

Thanks for the info.
I was a bit precariously placed on the roof and although I tried to open the box by sliding the front grey panel up (if that is indeed the way they open), I was unable to. I couldn't see any screws or similar, but if I unship the whole thing and move to somewhere a bit safer I'm sure I can suss that out. That'll keep for after their new telly though, because who knows - it may just work as is with a DVB-T tuner. It's also possible that they'll see no benefit in trying especially hard to switch to DVB-T, HD notwithstanding, as they aren't huge TV watchers anyway and may feel that SD from Optus D1 will suffice.

Another aspect (I think raised in a different recent thread) is that they are renting, so the onus for providing UHF reception and the costs involved are in a bit of a grey area.

The Freeview coverage site says "possible with a high antenna", same as for my place two doors down. Theirs is higher than average; certainly I couldn't reach the elements standing underneath it, so it must be about 2.5m above the roof level. I've got a good length of high quality RG6 cable left from my satellite dish installation, so, if I can access the antenna, what with it being so high and me being not young, nimble, or lightweight in any combination, then I can have a crack at running a new lead and bypassing the mystery box as a bit of an experiment.

xarqi

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Ultimate Geek

#667868 5-Aug-2012 18:00

Oh - I forgot to mention that in my first investigation about a week ago, I was just able to receive some UHF analogue channels using a 36 dB gain powered indoor UHF antenna. That's something that I can't do at my place, and it does suggest that a high, amplified, high-gain exterior antenna may do the business for them for DVB-T.

Jaxson

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#667890 5-Aug-2012 18:46

Many masthead amps are setup as diplexers. I'd try without anything on the line initially, just a straight run from the UHF to the TV. A masthead amp will be close to useless without any power, and on a lucky day you won't need it at all if running UHF only and not trying to mix it with VHF as well.

If it does need to be powered, then as B1GGLZ mentions above, you could try Jaycar. It gets inserted into the coax and powers it that way.

B1GGLZ

1961 posts

Uber Geek

#667971 5-Aug-2012 21:47

The Kingray masthead amp I have (in my junk box) is hinged on one side with a snap clip on the other side.
Jaycar still have power supplies on their website.

http://www.jaycar.co.nz/productView.asp?ID=LT3256&keywords=masthead+amp&form=KEYWORD

xarqi

727 posts

Ultimate Geek

#668024 5-Aug-2012 22:50

Thanks again.

No obvious hinge or clip on the box here. It seemed to be in two parts based on colour - looking like a main beige box with a separate thin grey cover. The only marking was "Kingray" embossed on the front, but possibly there is something on the back hidden by the mast itself. It may just be a generic plastic box, with perhaps, a die-cast unit inside.

Looking at some of the current Kingray products, one big difference between them and what is on the mast is that the sockets on the bottom of the one in question here are vertically mounted from the actual bottom of the box, rather than horizontally mounted from the bottom part of the front face, if that helps pin down what it is that I'm looking at here.
(I guess I should have taken a pic.)

Thanks again for all the help. There probably won't be any more action on this for a while as I'm not sure quite when they are planning to get their new TV, but I'm thinking in terms of weeks. I'll report back if there are developments, or, as is more likely, I need more help!