In car TV reception issues (Digital TV aerial design question)

[Phil]

Hi All,

I recently bought a digital set top box (DSTB) for my in car LCD screen. I
assumed that a DSTB would be better equipped at receiving a better image
than a standard analogue TV tuner. Having tried the unit on my home TV with
only a 10cm wire for an aerial, I was impressed at the excellent image
available on all channels. I confidently installed it in the car assuming I
would not have any reception problems once done. Not so. Trying the old
10cm wire for an aerial inside or outside the car did not give me any
channels at all. Using some rabbit ears positioned at the rear window only
gave marginal results. The moment the rabbit ears were held outside, bingo,
a brilliant image on all channels. I thought it might have been the
interference from the inverter which was powering the DSTB. So I tried an
extension cord to the car and powered it from mains. Still poor reception.
So I guess the problem is with the large amount of metal surrounding the
aerial in the car. This leads me to believe that the only way around the
problem is to build a good aerial on the outside of the car. I have thought
about getting a plastic spoiler for the boot, and building the aerial into
that. Which finally leads me to my two questions:

Would a TV amplifier help with the reception? Do standard TV amplifiers
amplify the digital signal as well as the analogue signal?

Is the thickness of the aerial wire a factor? Any other thoughts on design
aspects?

Rgds, Phil

 

[Ken Taylor]

Hi All,

I recently bought a digital set top box (DSTB) for my in car LCD screen. I
assumed that a DSTB would be better equipped at receiving a better image
than a standard analogue TV tuner. Having tried the unit on my home TV with
only a 10cm wire for an aerial, I was impressed at the excellent image
available on all channels. I confidently installed it in the car assuming I
would not have any reception problems once done. Not so. Trying the old
10cm wire for an aerial inside or outside the car did not give me any
channels at all. Using some rabbit ears positioned at the rear window only
gave marginal results. The moment the rabbit ears were held outside, bingo,
a brilliant image on all channels. I thought it might have been the
interference from the inverter which was powering the DSTB. So I tried an
extension cord to the car and powered it from mains. Still poor reception.
So I guess the problem is with the large amount of metal surrounding the
aerial in the car. This leads me to believe that the only way around the
problem is to build a good aerial on the outside of the car. I have thought
about getting a plastic spoiler for the boot, and building the aerial into
that. Which finally leads me to my two questions:

Would a TV amplifier help with the reception? Do standard TV amplifiers
amplify the digital signal as well as the analogue signal?

No. You have no signal to amplify.

Is the thickness of the aerial wire a factor? Any other thoughts on design
aspects?

In theory, yes. In practice, no. If your piece of wire works as an antenna
once outside the car, I think you now have all the relevant factors. As you
said, the amount of metal is not insignificant. Building an antenna into the
spoiler is a cute idea, by the way.

Oh, and don't watch any late-night porn while hooning down the highway.

Ken