All posts by Bill Wallace
Below are all of Bill Wallace's postings, with the most recent are at the bottom of the page.Mike Green's post regarding the use of a splitter prompts this cautionary note. Unless the splitter has both output ports terminated with the characteristic impedance of the aerial and its downlead/s (usually 75ohms) either at the splitter or the far end of the distribution cable - eg, the TV - AT ALL TIMES, any cables connected to it will act at "stubs" and will create standing waves, possibly resulting in the equivalent of a shortcircuit (or open circuit) at the aerial at some frequencies.
Equally, the current changes from analogue to digital may result in some channels being beyond the frequency range of the aerial (check the Group for the latter). If the required channels are very disparate (eg, some down at channel 24 and 27 and others at 67 as I have) the best results will come from a wide band aerial (eg. a log periodic array). But because these rarely have an overall gain of more than 10dBi (much less than so-called "hi-gain" aerials), a masthead or similar amplifier (possibly with a passive hybrid distribution system) will probably be required.
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Although I'm using a JayBeam wide band LPA which has always been OK in the past, coupled with a Triax 15db TFM15W Masthead Amp at my location NN12 7TN, I'm now experiencing poor signals for transmissions on Channel 67. Is there any reason for this from my current transmitter (Sandy Heath)? I'm prepared to wait a few weeks until further channel rearrangements are completed (August 31st and later).
The aerial still looks fine mechanically but I suppose it is just possible that the head amplifier could have failed in some way (I hope not because I'm less able to climb masts than I once was!).
Any thoughts, particulay on the reliability of the Triax TFM15W?
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If anyone is interested in a low cost but effective wideband aerial they should look at the Fraccaro LP45NF marketed by DASTV (their part number is DAS 1087). It costs less than a tenner (plus postage) and is quite well made, specified and CAI certified.
My experience of several orders with DASTV has been very satisfactory, both in terms of value for money for the wide range of products socked and for the quick and efficient ordering and supply. www.dastv.co.uk/shop will take you direct to their online catalogue and ordering facility - well worth a look.
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For Sue, re LG Flatron RZ-15LA32
According to my info this model has 1 SCART socket. If so, you don't need a box with a modulator as described by JB38. There are a number of Freeview devices which plug directly into a SCART socket without a lead; ie, they are behind the TV or whatever. Such devices are still available for under £30.00. I'm currently using a Metronic "Digi"Scart in such a manner.
The only drawback is you may have to bring the LG Flatron RZ-15LA32 forward from the wall to accommodate such a device, thus possibly also needing a new mounting bracket.
Mind you, with the cost of digital TVs now being so low (you should be able to get a 15" one for well under a £100) the cost of such a device and new mount may not be worth it.
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Alan Thompson: Re (jb38 Monday 14 November 2011 9:33PM). jb38's comments valid only for Freeview boxes with an external power supply (some, even cheap ones, have inbuilt mains PSU). Also, even with external PSU, check the voltage. Many are 5 volts rather than 12 volts.
If it has/needs an external PSU but requires 5v, you should be able to get a 12 v to 5 v converter (used for operating USB accessories or similar from a cigar socket)from anywhere stocking computer accessories.
Even if the box has an inbuilt mains PSU, look at the Maplin range of inverters (providing 230v AC from DC) which are quite cheap and come in a range of sizes from a few watts up to half a kilowatt!
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Does anyone have any information on how/when to check on software updates for a Tevion 48405 Set Top Box? The supplier's service agent cannot help and is dismissive of any need due to the newness of the STB (Aug 2011).
The user manual gives no such information other than the fact that there is provision via the Tools Menu to achieve this, namely Upgrade by Air or Upgrade by Media. If opting for the former, a search commences immediately despite "greyed out" screen options for inputs as follows:
Frequency: 000.000MHz
Bandwidth: selectable 6,7 or 8MHz (default 8MHz)
Download PID: 0000
Start
Althought the menu options are initially all "greyed out", pressing Exit then accesses them - but with no instructions on what, if anything, needs to be input and/or when, and the user manual gives no details. However, if no action is taken (ie, Exit not selected) the search continues but results in an Invalid Information message. Pressing Exit accesses the above menu items but, if no frequency or PID info is input followed by Start, the result is as before (Invalid Information). Clearly, SOME information is needed for these parameters
If Upgrade by Media is selected, a USB device must first be connected - but the user manual again gives no details of how the software is obtained.
Any advice on the above (or on this particular STB) would be welcomed.
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Apropos jb38's comments to Gay Skinner, Friday 17 February 2012 7:46AM:
Could you please elaborate on "mux has negative offset on its frequency"? Although my query does not relate to the Guildford transmitter, one of my set top boxes (a Tevion 48405) shows offsets varying between -635kHZ on mux channnel 24 and -664kHz on mux channel 52, all from from Sandy Heath. What is the significance of this? Is it a function of the transmission (doubtful, in my opinion) or the demodulation by this particular STB? I favour the latter because I seem to recall much lower offsets being shown for another of these STBs which I had to return to the retailer a few months ago with an unrelated problem. But if it IS the STB, are such large offsets a problem (or a potential one, perhaps indicative of a phase locked loop near the limit of its locking range)?
I also have a question regarding FFT which, for this particular STB, is shown as 2K on all mux channels whereas my LG M227WD monitor/TV with integral Freeview shows 2k on channnel 31 only, with channels 24, 27, 48 and 52 all showing 8k. Again, any explanation would be helpful.
For the record: of the several different STBs and two TVs with inbuilt Freeview (the LG and a Sanyo CE32LD33-B) I'm currently using, only the Tevion STB gives such detailed signal information, followed by the LG monitor/TV with rather less information. If there is any means of posting images to this forum (or e-mailing direct to either jb38 or Briantist) I'd be happy to send such details; if so, please advise.
Regards
Bill W
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Does anyone have any experience of the Panasonic TU-CT20 set top box (they call it Digital Converter Box)?
This is a fairly old device (superseded by the CT30 box a few years ago) but it was recently fully serviceable and reputedly coping with all of the recent retunes/channel changes in my location . However, I've been asked to put it back into service (intended for a non-SCART TV because it has an internal modulator) and this is being problematical - not helped by Panasonic being unable to help because of the obsolete nature of the box.
When setting it up via SCART to another TV it appears to tune mux channels 24, 27, 48 and 52 (but I haven't seen 51, although it may be there) but does not show all of the program channels. Notably, those from COM4 and COM6 appear to be missing - the first being a surprise since Ch48 appears in the setup scan list. Most annoyingly, the program identification numbers (all in ascending order) do not agree with Freeview numbers. Additionally, radio channels are mixed in with that ascending order of program numbers. Any ideas on how I can separate Radio from TV and, ideally, allocate Freeview numbers? The User Manual is unhelpful or, at best, unclear.
I can understand why COM4 Freeview channels are missing if I haven't got Ch51 but why not Freeview 12, et al which should be on mux COM6 (Ch48). All are certainly present on my other TVs.
Signal strength and quality are not a problem. Quality is in excess of 9 (on a bar graph to 10) for all programs and I suspect that the problem lies elsewhere. The STB seems susceptible to different power supply units (PSUs) despite all giving a measured 15vDC on load, the main susceptibility being that setup sometimes freezes at mux Ch48 on the original Panasonic PSU (a switched mode device) whereas OK on a "linear" PSU.
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Hi jb38.
Thanks for that response. At least someone has experience of this box or similar and can share the experience!
Failing the acquisition of another box with an inbuilt modulator, is there any way to reorganise and relable the channels I've got into Freeview (LCN) order on this TU-CT20?
Or do you have any suggestions re other (available and reliable) Freeview boxes with integral modulators which meet current DVB-T standards. Sadly, it's my misfortune to have a TVonics MFR-200 which died without warning, also several Daewoo DS608P boxes which used Setpal technology which does NOT meet the current standard!
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Wednesday 18 May 2011 7:25PM
Towcester
I don't have any reception problems, only channel numbering on a newly acquired Technika TDVB77 set top box. The channels are numbered in what I suspect is the order they were decoded from each mux and, whilst they can be resorted, there appears to be no provision for renumbering in LCN order.
I can't find any tech support for Technika in the UK (Note, this is NOT a box from Tesco which is a major retailer of Technika products)so I wonder if anyone can help with the problem or advise me of a link for tech support?