Re: LF: RE: Todmorden receiver

[Paul Nicholson <vlf0403@abelian.org>]

Ground to a halt this weekend on the new H rx, waiting
for parts.  There's always something that's out of stock!

 http://abelian.org/vlf/tmp/171210a.jpg

I decided I could fit both pre-amp and line driver into
the same box.   I couldn't see any noticeable feedback
or coupling between in and out transformers on the
breadboard.

Stefan wrote:

> what is the 'gain' on 2970 Hz relative to the old system from
> the last season?

Hard to say, because I couldn't determine the cause of the
low S/N (compared to E-field) at 2970 and 5170.  My guess is
intermod and if so the new rx should be a few dB better!

Meanwhile I spent a bit of time on the new spectrogram - it
can be tried out at

 http://abelian.org/vlf/fbins3.html

eg some recent T/A signals

 http://abelian.org/vlf/fbins3.html#p=1512392400&b=280&s=sp&m=fb&c=1

and it needs a standards-compliant browser which rules out most
versions of Internet Explorer, except maybe v10.

The difference with this one is that it downloads raw spectrum
data to the browser and all the arithmetic is done in JavaScript
within the browser.   This makes it much more interactive, and
quicker too, although the spectrum data is downloading in ASCII
at the moment.  It'll double speed when I switch it to binary.

It also means you can rip off the code and use it for your own
on-line spectrograms.  You just need to supply the spectrum
data from your web server, which is about a 30 line shell
script running vlfrx-tools.

My plan is to make it multi-band, easy - just change the URL
that it pulls spectrum data from.
--
Paul Nicholson
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