Re: VLF: Carrier on 3675.005 Hz

[Markus Vester <markusvester@aol.com>]

Hi Paul,

> Not much use continuing with carrier when I only have half a receiver

> but the system noise is still consistently 0.1 dB worse than the existing rx

Hmm, loosing 3 dB or more while attempting to gain the last 0.1 dB - sometimes being perfectionist can be a curse ;-)

All the best,
Markus


-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 9. Aug 2017 15:43
Betreff: Re: VLF: Carrier on 3675.005 Hz

I'm measuring about 0.016 fT daytime, 0.045 fT nighttime.

Daytime signal phase leads the night phase by about 67 degrees.

Combining and normalising day/night signals and excluding
the terminator periods gives

http://abelian.org/vlf/tmp/170809a.gif

Still not significant, only about 3.5 sigma, 10.9 dB S/N
in 1.13 uHz.

> Seems the result is even poorer than on 2.97 kHz?

Probably just because I'm not using the E-field.

> i would try some first EbNaut on that 82 km band over
> to DL0AO in 226 km.

Yes, if the S/N is good enough at DL0A0. Not much use continuing
with carrier when I only have half a receiver.

This afternoon I'll do some more work on the new E-field rx.
Running side-by-side comparison with the old rx.

I've been working on the new rx for over 2 years but the system
noise is still consistently 0.1 dB worse than the existing rx.
The front-end noise of the new rx is lower but the bandwidth is
wider. The extra signal is raising the noise floor slightly
due to a tiny amount of distortion in the line driver and
isolating transformers. On the test bench the new rx does very
well: very low noise and low distortion. But with the full
signal from the antenna there is enough mixing to slightly raise
the noise floor. I just need that 0.1 dB and also to cure some
mechanical noises (microphonics) when the wind blows.

PS, the new rx also also covers 137 kHz!

--
Paul Nicholson
--