Nags Head II

Frank Gentges
Wed, 5 May 1999 01:22:37 +0000 (GMT)


We went down to Nags Head over the last week of April.  A bunch of LF
receiving gear went along and we were thinking about setting up out on the
beach for at least one evening.  The weather turned foul and we were faced
with cold rain and high winds off of the ocean so a beach trip was never

At the cottage we were able to set up both the NRD525 and the TenTec RX320
and do side-by-side comparisions.  In most situations the two receivers were
neck and neck with no clear winner.  We were able to copy the European LF
broadcast station carriers for some of the time.  On one night the modulation
was coming through and the audio was judged to be Q3 to Q4.  It was in the
French language so I could not understand it. Surprisingly, the static was at
tolerable levels. 

On several nights I was able to detect VLF stations between 16 and 24 kHz
that I simply could not hear from my home in Great Falls VA.  Being only 2
blocks off of the beach seemed to have a clear advantage on these signals
over more inland sites like my home.  I was also able to consistantly copy
the Navy VLF signal from Hawaii there that I cannot copy from home so there
seems to be more than just getting the land out of the signal path. 

These VLF signals were close to detectability so they were a good test of the
difference of the two receivers.  Essentially signals at the threshold of
detectability on the NRD525 in the 200 Hz CW bandwidth were not detectable in
the RX320 in the 300 Hz bandwidth.  The differences are not much as the
signal is right at threshold.  I would only estimate the difference as being
2 or maybe 3 dB.  Nonetheless, the difference was seen on several nights on
different signals so the difference seems to be real and not a statistical
artifact.  This all occured where I was cued that the signal was there and
yet could not detect it. 

This may raise the issue if there is a difference between analog and DSP
receivers similar to the arguments in the audio field of vinyl record audio
vs. digital CD audio.  More work needs to be done to find the differences in
some more objective measure.  For now I am convinced it exists. 

The RX320 was tried in the car using the automobile 12 volt power in place of
the plug-in power supply and the Toshiba notebook on batteries.  A simple
cigarette lighter plug cable with the coax power connector on the other end
was used. This setup worked well except that more work needs to be done to
suppress other automobile interference to make it really usuable. 

Frank K0BRA