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All posts by Jim F

Below are all of Jim F's postings, with the most recent are at the bottom of the page.

Geoff: You can combine different signals onto a single coax cable using a diplexer (for two) or a triplexer (for three) etc. BUT you can only do this if the signals don't use the same frequencies.
This arrangement is used in e.g. blocks of flats where only one aerial system feeds a multiswitch which combines satellite, terrestrial TV, DAB and FM onto each coax output. The wallplate each flat contains the filters to separate these signals.
You won't be able to combine cable TV with anything, and likewise with ethernet, so keep these entirely separate.
The telephone and broadband are already diplexed (before any ADSL filters) so normally run in standard telephone cable (again, don't combine with anything else).
N.B. If you have a Sky+ or Sky HD box you'll need two separate coax cables for the inputs (but you could combine with terrestrial TV, DAB & FM).
Have a Google for "multiswitch" and also for "triplexer" to see what options are available.
Bear in mind that there is some signal loss going through diplexers - don't use with marginal signals.

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JiggleBob: I have seen an arrangement using a zone 2 dish (bigger) feeding a 2-way splitter (lossy, so needed the bigger dish). This enabled a single Freesat box to be used either upstairs or downstairs with only a single coax feed into the house.
However, in your situation, with two separate Freesat boxes I'd avoid doing that - Sky boxes send volts up to the LNB on the dish even in standby mode - Freesat boxes that I've tried don't (they only send volts up to the LNB when they're operating), but I can't say that's true for all Freesat boxes. You want to avoid the situation where your Freesat boxes are trying to send different voltages to the same LNB.
Best option is to have a quad LNB on your existing dish and separate cables to each room.

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Diagnostics - old version
Tuesday 9 August 2011 8:07PM

Bill Wallace: The aerial and masthead amp are likely to be OK, but you might possibly have a dodgy power supply or water in the coax cable (or both).
I've seen F connector joints on masts, all wrapped up nicely in self-amalgamating tape where water has somehow got in. This can produce an interesting effect - if the power supply is disconnected, and then reconnected, the signal momentarily comes back OK, but as water starts to conduct current the signal dies away.
First step is to change your power supply - but bear in mind that a new supply could behave as above, in which case check any joints out on the mast.

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All DAB transmitters
Thursday 11 August 2011 11:04PM

Briantist: Looking through Ofcom's list of DAB transmitters, they don't seem to include Aldeburgh, Cambret Hill, Foel Fynyddau, Holyhead South Stack, Morpeth & Pitlochry, even though these are shown on the BBC's DAB Tx list.
Additionally, Ofcom don't have Ebbw Vale and Membury as BBC National DAB sites, even though the BBC thinks they are.
Are the BBC running unlicensed transmitters, or have Ofcom missed a few off their list?

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All DAB transmitters
Friday 12 August 2011 9:55AM

Briantist: Could you also ask them about the ERP values? Looking through the lists, there are a few discrepancies (values in kW):

Tx BBC Ofcom
Abergavenny 0.5 0.2
Carmel 5 3
Chatton 3.2 3.05
Dover 1 2
Fenham 2 1
Hemel Hempstead 5 4
Holme Moss 5 2
Hungry Hill 0.01 0.08
Idle 0.7 0.3
Ivybridge 0.25 0.18
Kilvey Hill 10 3
Lark Stoke 5 3
Londonderry 6.2 6.3
Madingley 5 4
(Gt) Massingham E 1.2 5
Monmouth 0.1 0.23
Mormond Hill 3 2
Mynydd Baedan 1 0.75
Pontop Pike 10 8.2
Pontypool 1 0.5
Stanton Moor 1.8 1.5
(Sunderland) Hendon 1.2 0.8
Tunbridge Wells 0.7 3
Wenvoe 9 8
(Winchester) Crabwood Fm 1.5 1

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lee: Looks like the houses there in Saughall all have their aerials pointing at Winter Hill. Arq B MUX (for Film4) uses UHF channel 55, so try manually tuning for that and see what signal strength / quality you're getting. Reception where you are should be good, but Arq B is operating at low power at the moment, and doesn't go to full power until 21st September. If you can't get Film4 now, you may well find it'll "appear" then.

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BBC iPlayer on Freesat - starts soon
Friday 12 August 2011 10:48AM

Dave: Freesat TVs or digiboxes will typically display 100% signal strength and 100% signal quality on a very ordinary signal from a minidish.
Neither signal strength or signal quality will help you with getting BBC iPlayer though, since that comes through your telephone line and you need an ethernet connection from a modem to get it.

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All about Freesat | Freesat
Friday 12 August 2011 11:01AM

bernard: The full list of Freesat channels is at:….pdf

125 is More4+1 (i.e. not Challenge) on Freesat.

The Sky EPG is at:
TV Guide & TV Channel Listings UK - Sky TV

125 is Challenge. You'll need a Sky box and subscription to see it.

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Beary Peark (IoM) Freeview Light transmitter
Saturday 13 August 2011 8:07PM

Tony: Good point about interference possibly coming from behind the aerial - I've not (yet) got all the details for Irish transmitters to factor that in. I'm trying to think of a log periodic aerial with a large "deflector" though - which one did you get?

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jason carter: Two coax cables attached to one aerial is not normal or recommended (the mismatch will give significant signal loss).
Use one coax cable from the aerial to feed a passive two way (or however many ways you need) splitter. That will maintain the 75 ohm match and minimise your signal loss.
At around 16km from Mendip, you don't need a big aerial - though signal loss through roof tiles can vary substantially. Mendip is group C/D (and stays that way after the retune event on 28th September), so either a C/D aerial or a wideband should work fine.
Signal strength readings can be a combination of strength (power) and quality - its the quality that matters more than the power

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