Zenith DTT901 Mobile

Jim1348 · 10-31-2009, 07:37 PM

I will be trying something of an experiment. I took a Zenith DTT901 converter box and put it in my work vehicle today. I know that ATSC doesn't work in motion, but I am in the car most of the work day and I was wondering if this will work for TV audio while I am parked for lunch. Our local stations have news broadcasts from 11AM to 12:30 PM and I usually take my lunch break sometime during that time period. My DTT901 was sitting in my detched garage and wouldn't get much use this winter anyway, so I decided to Velcro it to a location in the car to keep it from shifting around. For power, I had a spare 12 volt DC to 120 volt AC inverter that doesn't get used very often. So that just plugged into a a spare cigarette lighter jack. For audio, I took an MP3 adapter that has RCA jacks and connected directly to the auxiliary input on my in dash AM/FM stereo. The antenna is the questionable part for my right now. I am going to try a spare FM antenna first that is probably just a 1/4 wavelength of wire that terminates to an F connector. My normal work area is less than 20 miles from the transmitters at Shoreview MN. Anyway, what do you guys here think? Will this be an exercise in futility trying to get TV audio while parked? Also, are there any other antennas that I should be trying? The channels that I will be trying to listen to are:

4.1 (32) = 578-584 mHz
5.1 (35) = 596-602 mHz
9.1 (09) = 186-192 mHz
11.1 (11) = 198-204 mHz

Judging from the frequency ranges, I suppose ideally if I had an antenna resonant at about 195 mHz and 590 mHz, thus a 1/4 wave antenna cut to about 196 mHz would be 3/4 wave at 590 mHz. I will try my random wire antenna Monday, but if that doesn't work I will do some more experimenting. Also, I tried looking at the FCC records to determine if each of those are using horizontal polarity, but I couldn't tell from the FCC Database.

Trip · 11-01-2009, 08:49 AM

KMSP is the only one using elliptical polarization. The rest of the ones you've listed are using horizontal. (My website notes polarization in the Technical Data section of its listings.)

VHF is a real pain to get on antennas that aren't fixed outdoor setups, in my experience. You might be able to get the UHF ones pretty easily, though.

- Trip

HTNut · 11-04-2009, 11:29 AM

Subscribed to this thread.

Jim1348 · 11-04-2009, 03:43 PM

I now have three days experience with this. What I have learned so far is that the "random length" wire antenna did not work very well for me. Last night I switched to a rigid multi-band scanner antenna. I have it inside the vehicle horizontally. I seems to work great on Channels 4 & 5. These are the channels of greatest interest to me since there are newscasts from 11 AM to noon and then noon to 12:30PM. As far as set-up, menus, and channel numbers, that is not a problem for me. I set it up ahead of time, so all I really have to do is use the up down button for channel selection. For example, when I finished listening to Channel 4 this afternoon I tuned it back to Channel 5 and when I turn it on tomorrow between 11 AM and noon I should be all set. I may still do some more antenna experimenting. In as much as I am pretty happy with audio reception on 4 & 5, if I could get an antenna that also receives well on 9 & 11, that would be icing on the cake. For the amateur radio operators here, you might notice that 9 & 11 are actually pretty close to the amateur 220 mHz band. The trouble is, it is actually lower in frequency, thus requiring a long antenna. Perhaps the easiest would be to get a 1/4 wave 2 meter antenna and cut it for 195 mHz.

Piggie · 11-04-2009, 06:23 PM

I read Trip's post above that most are purely horz, but just to speculate on whips:

The idea of one element for both UHF and VHF might work if the signal is moderately strong to strong. If you cut the UHF it will be good for about 50 MHz or so across the UHF band if you were transmitting, but receiving it's probably good across 100 MHz or so.

If you make a whip for VHF, they are good for about 5MHz on transmit (2:1) but will work for about 10 to 15 MHz tuned well on receive. So one whip will cover channels 9 to 11 pretty darn good on receive.

Now the problem comes in that an antenna like a 1/4 wave or a 1/2 dipole will in fact have a very low impedance at a frequency slightly more than 3 times the frequency that resonates at the fundamental of the 1/4 wave.

Piggie · 11-04-2009, 06:25 PM

Quote:

Originally Posted by Jim1348

For the amateur radio operators here, you might notice that 9 & 11 are actually pretty close to the amateur 220 mHz band. The trouble is, it is actually lower in frequency, thus requiring a long antenna. Perhaps the easiest would be to get a 1/4 wave 2 meter antenna and cut it for 195 mHz.

You could look up the old plans and build a 2 band halo antenna changing the size to fit the TV bands.

Jim1348 · 11-04-2009, 07:27 PM

I actually have one of the Nil-Jon Super-M Classic Mobile Antennas. Although it is unlikely I would use it day to day, I might have to just try it at home to see how it performs in this application.

The Super-M Classic? Mobile Antenna

Piggie · 11-04-2009, 07:42 PM

Quote:

Originally Posted by Jim1348

I actually have one of the Niljon Super-M Classic Mobile Antennas. Although it is unlikely I would use it day to day, I might have to just try it at home to see how it performs in this application.

The Super-M Classic? Mobile Antenna

Actually that looks like a good antenna if you already own it. With the slant on the verticals to reduce interaction, they are also not totally vertical.

I bet it works pretty good in moderate to strong signal areas.

Trip · 11-14-2009, 08:19 AM

I'm told Fox has swapped the SD subs, so now the Fox 9-2 is on the channel 29 transmitter (and similarly, the My Network TV 29-2 feed is on the channel 9 transmitter). So you might want to go ahead and program that in for your experiment. That'll just leave KARE on VHF as your biggest problem.

- Trip

Jim In Seattle · 11-14-2009, 09:29 AM

Quote:

Originally Posted by Jim1348

I will be trying something of an experiment. I took a Zenith DTT901 converter box and put it in my work vehicle today. ... For power, I had a spare 12 volt DC to 120 volt AC inverter that doesn't get used very often. So that just plugged into a a spare cigarette lighter jack ...

---------------------------------------------
Jim, etal: I wonder how much noise the power inverter might generate? Ihad a similar idea and was going to try it with my DTV PAL converter box, which runs on 5 vdc - pretty easy to get from 12 volts.
Jim in Seattle


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