All posts by Kurt Eaves
Below are all of Kurt Eaves's postings, with the most recent are at the bottom of the page.
Briantist: well thats what i would have thought, however where the aerial comes in it goes to a programmable johansson cluster filter/equaliser which only allows through channels 50-59, channel 60 is a freeview mux but the cluster allows it through as the dropoff isn't that perfect and only a 5db loss is noticed if the attenuation is reduced on channel 59.
However we have already noticed an issue with the BBC channels and Sky News this morning, the occasional freeze, audio clipping, and a longer blank screen when changing to these channels.
The mast in question is around I would say about 300-400 meters away in a neighbouring street on a spot of waste land, so I think this problem is going to remain.
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Briantist : The postcode for your reference is B65 8HN.
We did have issues with reception while the analogue service was still active, however since September last year when the analogue disappeared we have had no problems. Just seems very coincidental that today of all days we have problems.
Managed to connect a spectrum analyser and there is alot of noise on the band between 794.00mhz and 857.00mhz, I can't check any higher as the analyser won't go past 857.00mhz.
It's been suggested interference may be leaking through either my FM or DAB aerial. Just going to try disconnecting those from the triplexer after the filter which filters the UHF component of the system. However I would have thought the FM and DAB aerial would have been highly attenuated outside their operating frequencies.
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Briantist : We received our mailer on Friday explaining our area was going to be trialled for reception problems as Rowley and Cradley had been identified as an area where interference was a high possibility.
Being the naturally suspicious person I am I connected my analyser to the system on Saturday and the band following channel 60 was very clean. However as from this morning the band from channel 61 was experiencing only what I can describe as intermittent spikes and prolonged pulses ranging power from 40dbmv to 55dbmv.
I have since disconnected the DAB an FM from the triplexer and capped off the inputs with 75ohm terminators and the problem has disappeared and the band is now cleaner than it was all that can be seen now is what I would describe as slight rumbling and spiking from channel 61 onwards.
The notable channels that were affected were bbc1, bbc2 & sky news.
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Popping and breaking up of the picture were mainly the problems. The complete system uses double screened copper cable with crimp connections throughout.
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I have left the FM and the DAB disconnected for now until I can filter it. I have connected the Johanssen Filter directly to a Vision V5-204 which then connects to V5-512 & V5-516 multiswitches, the 4 satellite cables also connect to the V5-204. I could have used a V5-524 but splitting the switches gives a better range of outputs as some of the cables are quite long as two cables venture outside to an outbuilding.
I've checked the signal levels directly off the aerial and they are a little jumpy ranging between 71 & 78dbmv, out of the cluster they are level at 66-67dbmv. At the plates the UHF power level is no less than 51dbmv and no greater than 57dbmv and thats taken from a selection of plates across the house. The satellite power ranges from 64dbmv to 73dbmv.
The error levels on the UHF muxes varies between a CBER of 4.3E5 & 7E4, & constantly at a VBR of <1.0E7 with an MER>32 and C/N at least >32dbmv. Which is back to normal now with the DAB and FM disconnected.
Before I disconnected the DAB and FM the VBER on channels 59 & 60 were fluctuating sometimes dipping below 5E7 which is around the cut-off for picture and sound problems.
So I think something was definatly hitting either the DAB or FM, not sure which one or maybe both. I'm going to do some more testing tomorrow now everything is working fine for tonight.
However I'm sure the system is not overloaded and working within spec.
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The V5 system was installed about 3-4 years back when the effects of 4G were little known however this is the Johansson Cluster Equaliser that filters the TV.
Programmable Filter-Equalizer - Johansson
To be fair I didn't think the 4G signals would leak in through the FM & DAB aerials as much as they have, I would have thought they would be highly attenuated outside their operataing range 88-108mhz & 217.5 - 230mhz especially more so towards the higher end of the UHF band.
The ingress of the 4G signal as said has stopped for now since removing the triplexer and inputing the filtered output from the cluster directly to the multiswitch, so just looking for a product to apply more attenuation on the FM & DAB outside their operating ranges.
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Vision do their own FM, DAB & UHF Triplexer(V24-310) which may give enough rejection of the 4G signal passing through the FM & DAB.
Frequency Range:
FM 88-108MHz
DAB 216-240MHz
UHF 470-860MHz
Inputs: 1-FM 1-DAB 1-UHF
Outputs: 1
Insertion Loss dB: FM 1.0dB
DAB 1.5dB
UHF 0.7dB
DC Pass: 12v 50ma
UHF Input/Output Rejection dB: >30dB
Well worth giving a try.
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Briantist : Yes still the same today, affecting Channel 59 more so today, in the sense that Sky News & Pick TV and everything else on that MUX have completely disappeared. The VBER is off the scale no doubt accounting for the complete loss of the MUX.
So I've disconnected the FM and DAB yet again and the problem is resolved. Ive got a Vision V24-310 on order so hopefully that will clear the problem once and for all.
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It's definitely the DAB thats causing the issue, I've left the FM connected to the Triplexer and disconnected the DAB and tapped off the input with a 75ohm terminator and all seems well.
As said before i'm waiting for a Vision triplexer which offers about 30db of rejection outside all three bands, so we'll give that a try, as the triplexer in using is a Labgear one at the moment.
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Monday 18 March 2013 1:57AM
Well I live in Rowley Regis and paid a huge amount of money for a small IRS system to be installed in our home so that we can watch freeview or locate a sky+ receiver in any room of our home.
Now I know for a fact i'm going to get grief when this test kicks off today as a 800/900mhz base station is directly in the line of sight between us and the transmitter at Brierley Hill.
I can see this whole 4G launch is going to cost me a small fortune as no way is £50.00+VAT going to cover the cost of putting my system right, and if it can't be put right and I have to buy freesat boxes for each TV in the house that defeats the whole idea of buying TV's with freeview tuners in them and the idea of an extra box sitting next to each TV is just plain ugly.
I realy feel some poor folk such as myself and others are going to suffer financially and really feel like we've been conned by the government and mobile operators out of our investment in upgrading our home for a digital future.
What are the chances there is going to be legal action in getting compensation for being directly affected by this as someone somewhere has to be held accountable.