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All posts by David Warner

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


Thanks for you detailed reply.
I have a compelling argument as to why my problem is NOT caused by high signal levels.
All Freeview channels carried by "Old" channel numbers 22, 23, 25, 26, 28, 30 and 35 are being received perfectly. This includes channel 30, which in London carries the Full HD channels BBC1, BBC2, ITV, Channel 4, Channel 5, CBBC and TBC (this being a narrow bandwidth H264 commerical gospel channel).
My problem is only with the low power COM7 and COM8 which radiate at 746MHz and 754MHz.
My own theory is that these much higher frequencies are attenuated more by the roof felt and the slates.
Then of course there is the matter of the trees - which change with the season.
I asked you if you could direct me to a website to give me the compass bearing to Crystal Palace.
Such a site existed a year ago - but not now, as far as I can see.
I notice that when I installed the 20 element aerial - it was ordered from CPC around 20th October 2019. With a compass. Having endured some months of BBC Four HD misery on the non-performing 10 element aerial installed may in April or May 2018, I got six months of decent reception.
Until the leaves came out on the trees??
You said in your replay that the Crystal Palace COM 7 and COM 8 signal had been boosted from 40kW to 84 and 81kW. Where did you get that from. I am wondering whether they have actually altered the radiation pattern - pointing it towards Nigel Farage perhaps, rather than rebellious Brixton?
Just to repeat my TV shows now sign of overloading on Freeview 1-105. Or 231-235.
On the other hand it shows severe lack of signal on channels 106,107,109 etc PLUS 93 PBS America+1 (which I watch a lot in the morning - or did until now).
The TV I use has a sort of signal strength indication - but this seems a bit unreliable.
Your comments about my railway viaduct problems - yes is the signal is week all sorts of things happen to the picture (chopped in half, goes green, sound screetches like bats), Currenntly this woud happen on channel 93 - PBS+1, although most of the time totally unusable.
On the other hand all the non-HD channels plus BBC1-Channel5 HD are very stable.
Over to you mate.
PS the aerial currently installed is https://cpc.farnell.com/a…1003
I do have all the previous ones, except the very first Band A on for analogue which I scrapped.
But I don't see a 10 element 1990 wideband installed for analogue channel 5 OR the Band A 10 element aerial I had to install when Freeview went HD (for me 2010), or the 10 element Band T aerial I had to install when Arqiva/OFCOM introduced the wretched COM7 and COM8. I don't see how they will help me now. You are only suggesting that because of you incorrect hypothesis about the signal being too strong.


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I just found your excellent article "Rebuilding Freeview High Definition from 2019 onwards" - and it explains a lot.What it doesn't explain is the rationale behind COM7 and COM 8 not being public service provision that license fee payers have the right to receive.

I understand that OFCOM's process for auctioning off the 5g 700Mhz frequencies is delayed - not least no doubt because of the present public health considerations.
Your article postulates an overall improved service when BBCA and D3&4 mulitplexes can be upgraded to HD, and this in turn depends on when it is deemed that the vast majority of TV receivers are capable of provcessing the DVB-T2 signal.

Anybody have any idea when that is likely to happen? I discovered yesterday that as well as myself getting very ropy reception on COM8 and none on COM7 (Crystal Place - 3 miles away), my brother who lives in Swaffham and uses Tacolneston has similar problems on these COM7&8 transmissions.

With regard to the use of COM7 and COM8 on synchronised frequencies - is this a short-term experiment? I see there is theoretical literature about Single Frequency Networks - including guidance from the EBU.
I would like to know why the COM7 and COM8 transmissions are only 20% of the power of the main multiplexes - especially as even an increase to maybe 100kW would most likely cure by my problem and my brother's problem with poor reception. Please note also that the theoretical information from the EBU suggests that interference from neighbouring transmtters is POSITIVE but only when an omni-directional receiving aerial (such as on a portable TV) is in use.

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StevensOnln1: re your comment - I have a broadband - or to be specific a Band T - aerial.
I'm not familiar with how DTV receivers work, but possibly I will be if I have to keep researching and posting. You suggest that I am suffering from excessive signal strength.
I say to you - I have perfect reception (near enough) on the multiplexes operating on 482MHz (200kW), 490MHz (200kW), 506MHz (200kW), 514MHz (200kW), 530MHz (200kW), 546MHz (200kW) and 586MHz (20kW).
On the other hand I currently get ZERO reception on 746MHz (43.1kW) and intermittently good/poor/nonexistent reception on 754MHz (39.8kW).
I noticed this comment on the RxTxLog website:
"Preparations for 5G arriving have been made though: in order to maintain a guard between 5G and the temporary multiplexes in the centre gap, a 167kHz offset is applied to multiplex COM8, which carries channels including FreeSports and BBC Four HD. This has reduced the amount of bandwidth available. To ensure reception of the multiplex remains robust, the forward error correction was changed to 1/2 earlier this year, which in our observations has made the signal slightly more reliable than before the change."
https://www.rxtvlog.com/2020/04/why-some-freeview-services-are-getting.html

Does this explain which I can sometime get COM8 signals at present, but NEVER COM7?


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