Old TV death ray?

[themadhippy]

If we'd followed BT's advice in the 90s and gone to fibre we'd be sorted

What and have BT's bank accounts look empty just before being sold.

[kerry davies]

Very little BT cable is more than 50 years old, Jon. Lead cable had such high scrap value it more than paid for replacement with either copper or, for trunk cables, fibre. What it sounds like is you had the dreaded aluminium cable. That was another Thatcher money-saver that cost billions and once past 5 years old falls apart when breathed upon.

 

If your line passes your house in an aerial cable on the way to the DP then returns in a "poly" and finally a dropwire it might explain things. It might have grown like that over time. Few linesmen have the time to spend rationalising cable runs that have grown up piecemeal as yours seems it might have.

[Junior8]

Brother in law was a PO Telephones linesman up to 2001 and would agree with everything Kerry says. Throughout the eighties he was always bemoaning the drive for cheap rather than best in what he always referred ti until he retired as the Post Office.

[J Pearce]

Thanks for the info and corrections Kerry. We had a succession of increasingly senior engineers visiting, each fixing another thing to chase the fault down the line. The most recent (hopefully final?) engineer was surprised by how old the cable under the road was, and said he'd flag the whole bundle as wanting attention. The route is underground from the cabinet to the pole that serves us via dropwire, but apparently went halfway down the street to a connection chamber then back to our pole. I was told our line length changed from over 500m to just under 200m.

[Brian]

Why 612KHz?

That's a good question, and one where googling has not been productive.

 

I'm thinking that a typo and that it should be MHz. 612MHz as the LO, mixing down to an IF of 45Mhz would put the received channel slap bang in the middle of terrestrial TV channels.

 

Plus, 612kHz is too low to be any use in receiving a video signal and has no bearing on the display side. It's an old TV so line scan will be 15,625Hz so 612kHz isn't going to be a harmonic of that with any strength.

[timsabre]

The article is talking about tuning an AM/FM radio to use as a detector - can't tune an AM/FM radio to 612MHz.

It is odd to give such a specific frequency - an AM radio would probably blurt out the noise whatever frequency it is tuned to.