“Hysterical loop was what I probably jumped through when I predicted back in the sixties that transistors and computers would never catch on. I did so love those cathodes, grids and anodes.

Oh well! We all make mistakes in life I suppose.”

“Dave, I think the birth control mechanism is the " hysterical loop ".
" `omes law " is a cockney spin-off of the famous american series (I think).”

“Far from boring Bill, I found it very enlightening. I gave up a career in electronics when I discovered ohms law had nothing to do with house purchase, and a hysteresis loop was not a birth control device.

Thanks for the sound advice, but was only joking about my lounge lights. Still using three candles and an old oil lamp.”

“250 watts is the E.R.P. (effective radiated power) in the U.H.F. (ultra high frequency ) band from the Bathampton repeater station.

I have equipment that can broadcast close to the same freqencies, and with it I can use 20 watts of power and reach as far as the Weymouth amatuer repeater.

A portable handheld P.M.R. radio transmitter has a range of 5 kilometers (3 miles) and only has 0.5 watt output.

The electromagnetic radiation from a Radio / TV transmitter reduces at the inverse of the square of the distance from it.

Think of it as a light bulb, from all angles the light is the same brightness. But as you walk away from it the amount of light cast on the ground reduces very quickly as the pool of light gets ever larger. Radio waves are like light, they are out of the range of frequencies that our eyes can detect.

So, to provide the power to cover a few miles for the Bath area, 250 watts is more than enough. (unless you are in the shadows of of hills etc.)

I hope that clarifies why the huge difference in power is needed for the main area transmitters such as Mendip or Wenvoe.

By the way low energy bulbs use about 15% of the 250 watts you use to light your lounge. You could save 85% of the 10.5p + it costs you every 4 hours. (250w x 4 =1 kw hour).

See, I said it would be boring didn`t I?”

“Did you not mean 250,000 watts Bill? 250 watts would only just light up my lounge lamps.”

“For the record.
Transmitter power outputs:-

Mendip 500,000w
Wenvoe 500,000w
Bath Repeater 250w”

“Here is a link to the list of TV transmitters in the West of England. It shows their channel allocations, power output locations etc.
http://www.ofcom.org.uk/static/reception_advice/regions/view_transmitters.asp-itv_region_id=18.html

Digital services will be occupying the same allocated frequencies, but they are multiplexed, (tranmitted in a sequence) on those channels. There will be a limit as to how many will be multiplexed, as there are only 4 channels alloted to the Bath (Mendip repeater) station.

The channels are allocated so as not to interfere with other transmitter sites using the same frequencies in our area.

The amount of broadcast channels available to the UK is regulated by OFCOM, and is subject to international agreement about sharing the electromagnetic spectrum.

Here is the link to the Digital transmitter information. http://www.ofcom.org.uk/static/reception_advice/dtt_pocket_guide_4_2.pdf

As a licensed Radio Amateur and a retired electronics engineer I could write a book about transmitters, their propogation characteristics, how weather influences elctromagnetic radiation over topography. But I`m sure it would bore most perople to death.

However, one thing remains probable for the future with regard to the (relatively new) digital transmissions, improvements to the allocated band plan will be made, more narrow band channels will be avaiable to allow repeater stations such as Bathampton Down to provide more TV channels.

Until either the laws of physics with regard to co-channel interference (spaces required between channels) is re-written, or some means of squashing more information into the existing channels is discovered, Bath will remain a technical outcast on the terrestial TV network.

Here is the last link to allow some understanding, and for Baths TV "problems" to be put into perspective "in the grand scheme of things."
http://www.ofcom.org.uk/radiocomms/isu/ukfat/”

“You'd need a long extension cable to get to Mendip!”

“Dave,
1. Fair point.
2. I wonder how many homes in central Bath actually have a good enough westward view to pick up Wenvoe. The high ground at Kelston, Lansdown and Priston is going to block most of them, although from http://www.ukfree.tv/txdetail.php?a=ST110742 it looks as though there may be a few hotspots to the east of the city. I also believe that Wenvoe transmits Welsh regional programming, which may not be ideal for people in the west of England wanting a ¿local¿ TV service.
3. The most up-to-date prediction (2 March 2010) for our old Walcot address http://www.digitaluk.co.uk/postcodechecker/main/display/detailed/BA1+5NS/NA/0 claims good reception on 18 standard channels and 2 HD channels. I¿ll be interested to see how it pans out.
The issue with the BBC¿s HD transmission appears to be national rather than confined to Bath, but it does lead on to the problems for people who want to watch HD transmissions in the centre of Bath being limited by planning restrictions on satellite dishes. I don¿t know the ins and outs of that one.
If only we all had cable¿”

“Hugh

"It's all down to Bath's hilly geography and the position of the two transmitters that serve us."

This is not the full story. For commercial reasons it was decided not to upgrade the Bath relay transmitter.
What's rather annoying is that other similar masts that broadcast to fewer homes have been improved.

"And unless you're one of the lucky few Bathonians with a clear line of sight to the Mendip transmitter, Bath is where your TV signal comes from."

Not strictly true. If you have the correct aerial & a good view westwards you can pick up Wenvoe in South Wales which is 10 times more powerful than Mendip.

"From March 24 we'd be getting good digital reception on eight channels, in place of the current dodgy analogue signal on four."

From what I've read this is not true. As the new digital signals have to compete for space with the remaining analogue ones, they are to be transmitted at reduced strength.
There also seems to be some confusion about how much those signals will be increased come the full switch over on the 7th of April.

And on top of all that there's the criticism of the quality of BBC's reduced HD transmissions.”