O-O

CptlA

I think the market will dictate what will happen. On one hand, ATSC can be received from further distances but can not be received while traveling faster than 5 MPH. With ATSC-M/H, it can be received while in route traveling faster than 5 MPH, but the ATSC-M/H signal does not travel as far.

O-O

Wonder if any of the car makers are going to offer mobile dtv options in cars with TVs un the back seat.

Piggie

I would think it would have identical range to ATSC? ATSC-M/H is bundled in the same data stream as the ATSC. My understanding it's no different than a sub channel, you either receive the broadcast tower or you don't.

It's like people that report receiving say 5.2 but can't see 5.1 from the same station. They have a decoding problem not a reception problem.

All that said, it would take some kind of an antenna on the vehicle. People will want it hidden, which alone will limit it's range.

It would seem though that cars could have a short 5 inch whip on the roof that was slanted back by 45 degrees. At this angle is a M/H station is purely horizontal the antenna will operate 3db down. If they purely circular the signal will also be 3 db down. This might be small enough of an antenna to appear "hidden".

Of course this means the mobile antenna at best will -6dbd, pretty big penalty. A quarter is to itself in the proper polarization -3db. The tilt it 45 degrees to the incident wave's plane polarization and you loose another 3db. Same if in a circular or elliptical field.

Making a longer whip similar to a cell antenna with a pig tail twist in it would help, but most people would not want something this long on their car, but could be an aftermarket option.

Another idea is the old in the windshield antenna. But they were poor performers. The idea was to eliminate a whip on the vehicle. But being inside all the metal of the car the windshield antennas were massive failure on reception of FM which is a lot easier than TV. One advantage to a newer style windshield antenna would be one that is both horizontal and vertical for stations that are some form of elliptical polarization. (Remember from Geometry a circle is a special case of an ellipse where the two foci become one point).

From my experience with in windshield antennas though the advantage of being cross polarized would be negated by the antenna being a poor location on the vehicle.

Going back to my idea of a whip at 45 degrees 1/4 wavelength long I would predict the reception range would be slightly better than an indoor loop on UHF. A loop has about the same attenuation from receiving signals after passing through the walls.

Still that doesn't offer much range. Blowing down the interstate you would receive signals from a town I would guess 10 to 20 miles either side of it. Then nothing again until the next town.

I used to do a lot of mobile TV back in the analog days. Often running from hurricanes. I would look for strong VHF stations normally low band where my outside antenna would work well. I actually never felt that worked that well. Even low band had a lot of fading miles from the source, as I use back roads when evacuating and stay off the interstates.

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But here would be the ticket for better mobile TV reception, but only the nerds in the crowd would put one on their car.
2 Meter & 70 Centimeter Mobile Halo Antenna by dxzone.com

The halo antenna is horizontally polarized with unity gain compared to a dipole. It is possible to stack halos. Here isa picture of one for 146 MHz, but one could be made for 600 MHz for UHF TV and it would be 1/4 of the size. 2 Meter & 70 Centimeter Mobile Halo Antenna by dxzone.com

__________________
The more I understand, the less I know.

O-O

If ATSC and ATSC M/H have identical ranges, why would anyone chose an ATSC tuner then?

That antenna has to create some drag for sure.

Piggie

What is drag compared to good DX? At one point in my ham career I had 5 antennas sticking up in the air from an 86 Volvo wagon, it was crowded. I actually blew out the preamp on my 224 MHz receiver with running so much power on 445 and 146 MHz. I had to leave the preamp turned off.

It would seem easy to me to build a device that received both standards. One might want an ATSC receiver as there is more content on ATSC. Example of most RV owners watch more TV standing still than driving. Depending who is in the vehicle I would rather have my "copilot" helping me watch the road than watching TV. Then when you park put up the antenna and watch ATSC.

M/H though might be a great thing for say a city bus, that is always in range of a station. Or a cab to offer without having to pay monthly fees.

__________________
The more I understand, the less I know.

O-O

That is very true, and subways too. They could install some small LCDs in each of the cabins for entertainment.

Piggie

How do you receive it in a subway?

__________________
The more I understand, the less I know.