18-10-2023, 06:40 PM
Here's a topic to which I contributed elsewhere but all posts were rapidly deleted.
The very idea of having a television set in the car has always fascinated me for some reason. The closest I got to this was 50 years ago, when I had my Sony TV9 on the passenger seat and I drove past the Crystal Palace transmitter. There was no reception on Ch 1 due to the sheer signal overload, but a good picture on all the other channels! An illegal act I grant you, which I wouldn't wish to encourage, but hopefully I've now got away with it.
Of course, today it is straightforward to obtain perfect TV reception in a moving car. The mobile phone cell network, with shared digital reception and video over the internet takes care of that.
But how was it in the analogue days, when perhaps you had an Ekco TMB272 in the back of your Daimler limousine? What was the battery drain of one of these sets? The figure of 4 amps comes into my mind for some reason... it may have been more. Anyway it was enough to rapidly run the battery down with the car parked up and the engine not running. I expect the picture would then begin to shrink.
I'm wondering what the results would have been like in a moving car in the UK on both VHF and UHF. All the signals were AM, except for the FM sound on UHF.
And what sort of receiving aerials were used? The car aerials sold for 'television' in those days were exotic looking things, presumably coming from Japan or the US. They were probably wide-band, and seemed to assume horizontal polarisation. I don't think these would have been ideal for use in the UK on Bands I and III, where vertical polarisation was mostly used. Anyway, taking into account all the reflections and the closeness to the ground, the polarisation as received must have been all over the place.
For this exercise, I'm assuming the car's semi-vertical whip radio aerial was used, whose resonant tuning (if any) would have been purely accidental. Never mind the losses in the low-capacitance car radio feeder! Incidentally, what transmission line impedance was this supposed to have?
Anyway, my guesses are as follows. Good interference suppression is assumed on the 'Daimler'. The car is in motion and situated within the primary service area of the transmitter. You're sitting in the back of course!
Band I. Basically steady reception with moving ghosting causing varying blurring of the picture. Some severe ghosting from buildings in urban areas... the longer the delay, the slower the ghosting would change. Ignition interference coming and going from other vehicles, often severe.
Band III. Less ignition interference but some ghosting, some signal 'flutter' and variable agc noise.
Bands IV and V. Continuous, objectionable signal flutter but little ignition interference. Popping on the sound. Diversity reception (with two aerials) worth considering. Colour would come and go.
As you can see, the results would probably have been barely watchable. We didn't miss much by not having television in the car!
Steve
The very idea of having a television set in the car has always fascinated me for some reason. The closest I got to this was 50 years ago, when I had my Sony TV9 on the passenger seat and I drove past the Crystal Palace transmitter. There was no reception on Ch 1 due to the sheer signal overload, but a good picture on all the other channels! An illegal act I grant you, which I wouldn't wish to encourage, but hopefully I've now got away with it.
Of course, today it is straightforward to obtain perfect TV reception in a moving car. The mobile phone cell network, with shared digital reception and video over the internet takes care of that.
But how was it in the analogue days, when perhaps you had an Ekco TMB272 in the back of your Daimler limousine? What was the battery drain of one of these sets? The figure of 4 amps comes into my mind for some reason... it may have been more. Anyway it was enough to rapidly run the battery down with the car parked up and the engine not running. I expect the picture would then begin to shrink.
I'm wondering what the results would have been like in a moving car in the UK on both VHF and UHF. All the signals were AM, except for the FM sound on UHF.
And what sort of receiving aerials were used? The car aerials sold for 'television' in those days were exotic looking things, presumably coming from Japan or the US. They were probably wide-band, and seemed to assume horizontal polarisation. I don't think these would have been ideal for use in the UK on Bands I and III, where vertical polarisation was mostly used. Anyway, taking into account all the reflections and the closeness to the ground, the polarisation as received must have been all over the place.
For this exercise, I'm assuming the car's semi-vertical whip radio aerial was used, whose resonant tuning (if any) would have been purely accidental. Never mind the losses in the low-capacitance car radio feeder! Incidentally, what transmission line impedance was this supposed to have?
Anyway, my guesses are as follows. Good interference suppression is assumed on the 'Daimler'. The car is in motion and situated within the primary service area of the transmitter. You're sitting in the back of course!
Band I. Basically steady reception with moving ghosting causing varying blurring of the picture. Some severe ghosting from buildings in urban areas... the longer the delay, the slower the ghosting would change. Ignition interference coming and going from other vehicles, often severe.
Band III. Less ignition interference but some ghosting, some signal 'flutter' and variable agc noise.
Bands IV and V. Continuous, objectionable signal flutter but little ignition interference. Popping on the sound. Diversity reception (with two aerials) worth considering. Colour would come and go.
As you can see, the results would probably have been barely watchable. We didn't miss much by not having television in the car!
Steve
It's rare and desirable
