[BC] Accurian HD AM tests

[Mark Humphrey]

I tested the AM side of the Accurian today and found that its digital
sensitivity in this band is really good.  However, out here in the
country, the supplied loop antenna is useless; it's necessary to
connect an outside antenna, away from sources of noise, to receive any
stations in HD.

I'm using a "K9AY" terminated loop, with a circumference of about 80
feet.  With the main lobe centered at 110 degrees (towards
Philadelphia), I receive these three stations consistently:

610 WIP has a measured field strength of 2.4 mV/m (on a FIM-41) and my
outdoor antenna provides a signal of -56 dBm with no pad.  I was able
to insert 39 dB of attenuation before the radio lost digital lock at
-95 dBm.

770 WABC, with a field strength of 0.45 mV/m, provides -69 dBm from
the antenna and decodes fine with no pad.  After adding 22 dB of loss,
it switched to analog at -91 dBm.

950 WPEN recently increased daytime power to 25 kW with a DA.  I'm on
the back side of their new pattern, where radiation is suppresed to
the level of their former 5 kW non-DA facility, and I usually measure
their field strength at 1.05 mV/m.  Without a pad, I measured -60 dBm
from the antenna, but I was able to drop this by 40 dB to a surprising
-100 dBm before the Accurian lost digital lock.

On the spectrum analyzer, I see that WPEN's digital sidebands are out
of symmetry by about 5 dB.  This was not apparent in December when
they were still operating on the non-directional antenna, so pattern
bandwidth may not be flat in this direction.  However, this doesn't
seem to have any adverse effect on digital reception.

At 0.5 mV/m, 710 WOR's field strength measures a bit higher than
WABC's, but a local station on 690, about 25 dB stronger, makes it
impossible to decode WOR's HD signal.

1340 WHAT in Philadelphia recently went HD, but their field strength
is less than 0.2 mV/m this far west of the city.  Even on the outside
antenna, their signal receives too much adjacent-channel interference
to decode.

I think we can conclude that the Accurian receiver itself is not
"deaf", but ambient noise and/or interference are the limiting
factors.

I'm currently working on a comprehensive test of the FM sections of
the Accurian, Radiosophy, JVC car radio, and Belar HD monitor.  Twenty
FM stations are receivable here in HD with the yagi, so I should have
some interesting numbers when the tests are completed.

Mark