WHDH-DT moves from RF-42 to 7

Garrett Wollman wollman@bimajority.org
Sat Jun 13 23:13:12 EDT 2009

<<On Sat, 13 Jun 2009 18:47:11 -0400, David Moisan <dmoisan@davidmoisan.org> said:

> I had thought WHDH-DT would run at low power for a while until their
> antenna is swapped out (their analog antenna is not suitable for
> VSB, I'd heard.)

The modulation mode makes no difference to the antenna -- the
bandwidth is the same.  The original construction permit for channel 7
specified a circularly-polarized antenna, and after that was granted
they decided that it wasn't worth the cost of replacing the antenna,
so they asked the FCC for an amendment for the maximum
horizontally-polarized ERP, which is the 30 kW you see in the files,
and that's what they're operating with right now.  The existing
antenna system has 8.9 dB of gain; the TPO for 30 kW is 3.67 kW.  The
current antenna is a Dielectric TWB9-7 with 0.75 degree of electrical beam
tilt; a comparable new antenna of the same type has 9.54 dB gain and
weighs 11,000 pounds.  (The antenna they specified in the previous
application weighs about the same and has 10.0 dB of gain.)

There's some theory that you might want a circularly- or
elliptically-polarized antenna and a high-UHF channel if you want to
be able to reach mobile devices.  (I'm not sure what Qualcomm MediaFLO
is using for antennas on channel 55.)


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