MAY - WTFDA.org

Antennas:
Marketing suggests you need a special antenna to receive digital signals. I have
a “Stereo compatible color antenna” box in my basement. “Antenna” is the only word
that's meaningful!
Stereo, color, and now digital TV signals are all broadcast in the same frequency
range. What makes an antenna good for analog reception is the same thing that makes
it good for digital. Accessories – preamps, splitters, coaxial cable, rotors, switches, etc.
- are all the same for digital as they are for analog. If you have a good DX antenna
system in place for analog, you can simply connect it to your DTV receiver and have a
good DTV DX system. If you don't already have a good analog antenna system, just
remember that the same rules that apply to analog apply to DTV.
There is one important difference. Digital TV is very intolerant of multipath -
“ghosts”. You may be able to tolerate watching an analog signal with a single stationary
ghost, but your DTV receiver may not decode such a digital signal at all. Any poor
cable connections, cheap cable, leaky splitters, or sources of signal reflections will need
to be fixed or replaced before you'll get reliable digital reception.
Propagation modes:
To date, virtually all DTV DX has been via tropospheric propagation. The current
tropospheric distance record is 835 miles. 4 Tropospheric propagation affects all
channels including UHF, and tends to be stable in signal strength over moderate
periods. This allows the DTV receiver enough time to “lock in” on a signal. UHF
channels have fewer stations 5 , so there's less interference to prevent DTV “lock”.
One DTV signal has been identified via sporadic-E. 6 Sporadic-E tends to involve
deep and rapid fading; often, an Es DTV signal doesn't stay in long enough to decode.
Es also only affects VHF channels, where there are many more analog stations. The
chances of interference from other stations are much greater. Finally, there are very
few digital stations currently operating on VHF channels 2-6. 7
Luckily, the latter issue will eventually change. 35 stations have digital
assignments “outside core”, in channels 52-69, while having analog assignments in
channels 2-6. These stations (at least in theory!) will be required to move their digital
operations to their low-band channels at the end of transition. Many of the mostfrequently-seen
analog Es stations are among this list – WMAR-2, WCAX-3, KGFE-2,
WOAI-4, KTVU-2, KQTV-2, WEDU-3, KJRH-2.
4For reception of WNCN-DT channel 55 Goldsboro, North Carolina by DXer Jeff Kruszka in Baton Rouge,
Louisiana.
5There are 62 full-power analog stations in the USA on channel 7; there are only 15 such stations on channel 47.
6Gerard Westerberg in Lexington, Kentucky received KOTA-DT channel 2 Rapid City, South Dakota. Only PSIP
data was decoded – no usable audio or video.
7As of August 2003 I'm only aware of eight low-band VHF DTV stations.
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