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Old 13th Dec 2010, 4:09 pm   #21
terrykc
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Default Re: Freeview DXing

It looks as if a lot of people are going to be doing some serious Freeview DXing for years to come. The problem being, of course, that they don't want to!

NTL, as it was at the time, had a series of cheap diplexers for combining the RF output of the STB with an aerial feed. There were different types depending on broadcast region and STB output channel (which, obviously, was chosen to avoid a clash with the local off-airs.

They were in a tinplate box with an outer plastic casing ~3cm cubed.

Considering the mass market there could be for them, I can't understand why no-one has produced a range of filters for DTV. All that is needed are high-pass filters with LF cut-off frequencies tailored to suit the local Tx. Group A doesn't need one, obviously, so the first would pass Group B and above, then the next would pass Group C and so on ...

I'm sure someone's missing an opportunity here ...
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Old 13th Dec 2010, 4:56 pm   #22
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Default Re: Freeview DXing

Some freeview boxes have a manual tune facility, OK for us but for Joe Bloggs and other non techy types it is a real problem!
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Old 13th Dec 2010, 7:55 pm   #23
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Default Re: Freeview DXing

This is something I've been thinking about for a long time (and was meaning to start a thread myself but never got round to it!)

It would be useful to know which STBs are best for this - manual tuning, VHF coverage for the Continental stuff etc..


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Old 13th Dec 2010, 9:09 pm   #24
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Default Re: Freeview DXing

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Originally Posted by G0MEM Michael View Post
...BTW I can confirm that Freeview DX does not work, as I can't receive Freeview at all from my current location...
I like it!
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Old 14th Dec 2010, 9:33 am   #25
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Default Re: Freeview DXing

A thought on the auto-tune issue - surely it was a problem on analogue before anyway?
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Old 14th Dec 2010, 9:37 am   #26
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Default Re: Freeview DXing

Indeed it is, but you can switch the channels round so that the strongest signal appears under the correct channel number.
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Old 14th Dec 2010, 2:21 pm   #27
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Default Re: Freeview DXing

I've got two "Oggle" freeview boxes (sold by Asda a few years ago), and they have become impossible to retune cos they get conflicting data from other transmitters, namely Winter Hill which is just in range to provide a weak signal, but, those have now been retired in favour of a Humax Fox t2 which had built in discrimination allowing you to choose your local transmitter, and it's great, not a problem and no messed up channel lists unlike with the Oggles...

I miss analogue, it wasn't so confusing...
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Old 14th Dec 2010, 8:03 pm   #28
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Default Re: Freeview DXing

We live in a weak Freeview area, and regularly have signal dropouts. Sometimes it seems to be channel selective. i.e. some good channels and some bad. I did start to suspect that this may be due to reducing power for engineering purposes but now I firmly believe its a path problem. We used to have similar problems on microwave links depending on the type of precipitation believe it or not. I have also found that our Freeview box is very susceptible to local impulse noise which tends to cause momentary freezing of the picture and sound dropouts. So for DXing, using high gain masthead amps etc. may just cause more problems. I wouldn't want to discourage you though, it's still worth a bit of experimenting with.
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Old 14th Dec 2010, 10:56 pm   #29
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Default Re: Freeview DXing

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Originally Posted by Biggles View Post
... I have also found that our Freeview box is very susceptible to local impulse noise ...
DTV in general is more susceptible to impulse interference so it's unlikely to be your box.

A problem that's been building up for years is the widespread use that terrible old brown (why was it nearly always brown?) coax with more fresh air than copper in the so-called screen.

The best thing is to replace the down-lead with CT100 or similar - the foam dielectric version is more resilient to kinking - and, if it's been up there for a few years, it might be a good idea to replace the aerial while you're at it.

Make sure it's a decent grouped one (unless your location demands a W version) without lots of plastic for the birds to peck at!

I'm amazed by the contrasting aerials around this neck of the woods which, as I've said earlier in this thread, is in a good reception area. Either it's monstrous arrays with three lots of directors (and plenty of plastic for the birds!) or cheap wideband contract aerials.

There are a lot of large houses round here that have been subdivided into flats, so it's not unusual to see three of these cheap things on the same mast - usually not much thicker than a pencil - supported by a flimsy lashing kit. Inevitably they are now usually perfectly aimed for reception from Australia or the moon ...!

Considering the cost of labour compared with the price difference between the right and the wrong kit, a lot of these expensive installations have short lives for the sake, virtually, of pennies ...

Bill Wright has an excellent Rogues Gallery which is well worth a look and here are some I've spotted.
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Old 14th Dec 2010, 11:12 pm   #30
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Default Re: Freeview DXing

I found out the hard way with the brown coax. Originally because of our location we couldn't get freeview at all, then I did a bit of investigation with a signal meter and discovered that the signal was best at the end of our shed roof, far stronger than higher up on the house chimney. This involved quite a long run of coax so I used the black stuff throughout after comparing it with a roll of the brown I had lying around. A new antenna was installed and a mast head amp. I suspect the impulse interference is actually affecting the amp because everything else is "watertight" installation wise. We did have a neighbour with a faulty cooker thermostat which caused havoc around tea-time for a while but that's been sorted now. You can see the white impulse trails on analogue TVs quite clearly, when it gives trouble, but as everything is running on a signal knife-edge anyway, I've just accepted it. Maybe it'll get better when we have to go fully digital.
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Old 14th Dec 2010, 11:22 pm   #31
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Default Re: Freeview DXing

If you are considering DX possibilities from specific transmitters, this handy calculator might prove useful.

By entering your location and the wanted transmitter, you can see the path on a map and, perhaps more important for this exercise, a signal profile shows the terrain in between you and the transmitter so that you'll be able to find out if there any obstructions in the way.

It's also loaded with both pre and post DSO transmitter information, which can also be useful and, a bit OT here, there is a satellite calculator on the same site. You can drag the position of the dish to exactly the right place and, if you use the OS map and zoom into maximum magnification, every building is shown, which can be very useful as an initial dish pointing aid.
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Old 14th Dec 2010, 11:38 pm   #32
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Default Re: Freeview DXing

We used to call this a path profile when engineering microwave links and there were quite a few different factors to plan in. We didn't have the luxury of seeing blocks of flats on ours though, just the contours and heights of the hills in the way. Links over tidal water were interesting, using space diversity systems to compensate for changing sea levels. Anyway, best get this back on topic.
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Old 14th Dec 2010, 11:41 pm   #33
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Quote:
Originally Posted by Biggles View Post
... Originally because of our location we couldn't get freeview at all ...
If you are using Pontop Pike, I'm not surprised! I've just plotted the profile from the centre of Hexham and there are two ruddy great hills in the way. Perhaps you are higher up? I note that there are plenty of contour lines on the OS map!

The calculator suggests Newton relay as your best bet but no Freeview until DSO!
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Old 15th Dec 2010, 12:07 am   #34
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Yep, Pontop Pike, and no, I'm down in the valley. It's a miracle really. Depending on where you are in the village (I'm not right in Hexham) you can get a signal, but move a hundred metres and its gone. I regarded freeview reception as a bit of a challenge, hence the perseverence with the antenna. Our local TV transposer is about two miles away but only rebroadcasts analogue. The picture on analogue from Pontop is watchable but grainy, and fades occasionally, but there is no clear line of site, so that proves it, RF does go round corners!
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Old 26th Dec 2010, 8:03 pm   #35
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Default Re: Freeview DXing

I have an MVision 200C stb that does satellite Fta and terrestrial DTV. The advantages are that you can tune to a specific channel / frequency and run a scan for Services , this only takes a few seconds so it would be fine for DXing. Also it does MPEG4 so will pick up Irish DTV and French TNT. For viewing ease you can mix terrestrial and satellite services in any order, so I have RTE on first few channels from terrestrial and BBC etc from satellite starting fom number 106. Also my Panasonic has a manual tune facility for both freeway and terrestrial
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Old 26th Dec 2010, 10:29 pm   #36
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Default Re: Freeview DXing

Hi Andy.
I can receive RTE analogue on VHF here via my VHF 12 element aerial and D100 DX receiver.
I doubt it would be possible on Digital though.
I am not sure though if Irish Digital is transmitted on VHF though`!
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Old 27th Dec 2010, 1:03 am   #37
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Default Re: Freeview DXing

Trevor

Your post just took me back to the mid-late eighties.
There's a D100 here, once connected to a continental (then new) band 1/3 array on my parents house.
I doubt it would be worth pressing back into service now,
but it cost a lot of money (at the time) then.
Bit OT, sorry folks

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Old 27th Dec 2010, 1:42 pm   #38
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Default Re: Freeview DXing

Quote:
Originally Posted by terrykc View Post
I doubt that anybody is going to build your special box for you! I shudder to think what it might cost!

Your best hope is that like minded person will re-write the firmware in a standard STB to do what you require. I know that there are a lot of people out there who write special mods for Topfield PVrs, but I don't know if the RF front end is amenable to such hacks.

Why not find a forum for Toppy fans and ask there? You never know, someone might already have done it or, perhaps, be interested in taking up the challenge ...

The only suggestion I can offer in the meantime is to use a spare STB (to keep the peace!) and a pen and paper.

Do a scan and watch progress. Every time it stops to acquire info, jot down the channel number. Then, when it's finished, analyse the results in conjunction with an up to date transmitter list. The STB will add programmes in the order it finds them so, if you end up with three lots of identical programmes, you should be able to identify which one is which by the channel order that particular mux is on. Sounds complicated but it probably wouldn't be too bad once you get used to it.
I have a few spare STB's around so this could be a a good starting point. As France and the nearer European countries are now for the first time using the same system as us I have heard a few reports from people living near the south coast receiving crystal clear French tv. Regards the reception of DTT from the southwest in Corsham, does your box say what channel you are receiving this multiplex on. Stockland Hill uses grp A channels whilst Beacon Hill is on the same grp as Mendip ie C/D channels.
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Old 27th Dec 2010, 7:18 pm   #39
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Quote:
Originally Posted by murphyv310 View Post
Hi Andy.
I can receive RTE analogue on VHF here via my VHF 12 element aerial and D100 DX receiver.
I doubt it would be possible on Digital though.
I am not sure though if Irish Digital is transmitted on VHF though`!
No, digital is UHF only, but it is pretty High power, main tx sites are in the hundreds of kW e.r.p. I have received UK DTT in the past here in South East Ireland
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Old 28th Dec 2010, 11:10 pm   #40
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Default Re: Freeview DXing

In october during a tropo opening i received german tv at a distance of 500 miles

http://www.youtube.com/user/radioredcat

using a sagem picnic box and also a asda durabrand box as well as nearly every transmitter from the south of england.

I can receive Llandonna here at 60 miles.

http://www.youtube.com/watch?v=bbDOITIc5To

I can also recieve Moel-y-parc 40 miles and The Wrekin 58 miles all the time except when rowridge/sandt heath and oxford knocks out the wrekin muxes via tropo.


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