O/T: Folded Dipole

[J. Clarke]

Some form of multiplexing.

[J. Clarke]

There are no "new digital frequencies". There are different channel assignments but the frequencies are the same as for analog TV, except that for digital there are fewer of them since the FCC has chosen to divert one block of frequencies to other purposes.

[Art Greenberg]

Subchannels are on the same carrier - IOW the same frequency - as the main channel. The various data streams for all of the channels, both video and audio, are divided into fixed-length sections called packets. Each packet includes a few bits that say which stream the data in it belongs to. Then the packets from the various streams are mixed together ("multiplexed") to create the transmitted data stream.

When you switch among subchannels for a particular main channel, all you are doing is telling the receiver to pick the packets that belong to the selected subchannel.

The frequencies will change due to the need to simultaneously transmit the digital and analog versions of the channels for some period of time, and then reclaim some of frequencies from the low VHF and high UHF channels for other uses once the analog signals are turned off.

Depending upon where you are, you may still need a combination high VHF/low UHF antenna to receive all of the digital stations in your area. I know this is true in Philadelphia PA, for example, where WPVI and WHYY will relocate their digital transmissions to the high VHF band on June

12th.

[Nova]

The following web site allows you to input your zip code (the only information REQUIRED), indicate if there are obstructions in your area and tell the calculator what type of structure the building is and the site will provide a chart of the stations in your area and what type of antenna is required for each station.

see:

[Leon]

That's is what I thought but my dad gets a lot of pixilization and slow motion and dropped sound with his digital tuner and TV. I thought you would get all or none way back when. As it turns out with my HD satelite DVR and mostly only with local stations broadcast through satelite I regularially get pixilization. The probpem is nonexistent with the premium satelite channels unless it is raining.

[Doug Winterburn]

The top 108Mhz of the UHF band has/is being assigned or auctioned off for other purposes, otherwise all old TV frequencies are the same. However, there may be some stations migrating from VHF to the remaining UHF frequencies. As well, some stations may not alight on their final frequency assignment until the June deadline.

Formerly K7OQF from the vacuum tube days.

[Maxwell Lol]

As long as the signal is strong.

When the signal is weak, the picture doesn't just get "fuzzy."

[J. Clarke]

That may be the theory, but if it misses a few bits you get a black screen while with analog you get a viewable degraded image.

Lucky you.

[J. Clarke]

This is the big problem with digital--it doesn't degrade gracefully--it's all or nothing.

[Mike O.]

Here's a link to the now famous coat hanger antenna.

are a couple variations of this but this is the basic idea. It's mostly a UHF antenna but some guys get upper VHF channels especially with an added reflector. That version builds the bowties on one edge of a 2x4 with a piece of plywood (or cardboard) covered with foil attached to the other edge. You can also combine 2 for more gain and some guys are mounting them on a rotor.

I built one and set it the back yard and it worked just fine. I used pieces of romex I found laying around the jobsite for the bowties. I haven't fished a wire from the basement to the attic yet so now it's hanging in the floor truss space for emergencies. Basically that's at ground level and it even works there.

You can buy practically the same antenna for not a whole lot of money but where's the fun in that?

Mike O.

[Morris Dovey]

I'll probably build a seven-element quad much like the 2m (146 MHz) antenna that let me check into a Rhode Island FM repeater net from my Minnesota home using a 14W transceiver.

Swingman helped me draw the hubs with SU a while back. :-)

[MikeWhy]

SU is the bomb! But how did he work around the line of sight problem?

[Morris Dovey]

Good electronics, good antennas (IIRC they had a Phelps-Dodge omni at

60'), and a 1200 mile "wormhole" is the only explanation I can offer. There was considerable surprise at both ends - that's a /long/ way for a low-power VHF signal to travel.

SU did well until I tried to add a threaded hole for a setscrew. :-(

[MikeWhy]

Me too! I learned a trick or two about 10d nails from that. At this rate, I'll be ready to test again, oh say, 2012 when the auroras descend again to the plains states. Wondering if Skynet and Nostradamus will cooperate. (I worked Moscow on 3 watts in 2000 on an attic wire. That was special enough for me.)

[Joe Brophy]

If you ever need a antenna with a bit more capability, google "HDTV coat hanger antenna". You will likely be able to receive stations you didn't know were even there. The added plus is that it is also very economical to make. regards, Joe.

[J. Clarke]

Signal propagation is a wonderful thing.

I remembrer one night I was watching something on Channel 4 in Jacksonville, Florida, and the picture faded out and came back with a different show from the one I had been watching. Then there was a station break and I found that I was now watching the Channel 4 that was in some place more than a thousand miles away (I forget where--that was at least 40 years ago).

[Leon]

Where did you hear that? My digital can be terrible right in between perfect and nothing. Terrible pixelization and this goes for my neighbor, BIL, and father.

[Leon]

Are you reading this some where? Do you actually have digital? I have had digital for close to 4 years and if I am getting bad reception the picture is all kinds of terrible, you would swear you were doing mushrooms when this happens.

[Art Greenberg]

Tropo duct, no doubt.

I think the bandwidth of that quad is going to be a bit narrow for even one digital channel, let alone a whole range of channels. You ought to be able to put together a simple log-periodic yagi that would likely do much better.

Hmmm... what would a log-period quad look like?

[Art Greenberg]

Yes, you _can_ have a marginal signal. Its just that the signal strength "knee" is quite sharp. If you have a picture with artifacts present due to marginal signal strength, it won't take much of a decrease in signal strength to get to where no data can be recovered ... and no picture produced.