Re: [VLF_Group] Re: E-field rx, front-end protection
- Yes I ignore output stage noise in modelling, my spice models
only do the input-referred current and voltage noise.
We usually hope that dominates! Anyway, on the bench the
breadboarded circuit has about the expected noise level.
It is only outside that the excess noise appears and now
that seems to have dropped with effective isolation of
the downlink cable.
Listening to all the microphonic rumble, I can see why the
Schumann resonances are buried. The antenna is quite unsuitable.
Needs either a loosely slung collection of wire as Sead suggested
(mechanical oscillations well below 7Hz) or a very rigid antenna
(vibrates well above). With a rigid antenna, might be able to
turn the bootstrap back on. I have one of those large blue plastic
barrels (the ones with the clip-down lids), maybe line that with
chicken wire and fill with soil or gravel.
Conditions a bit grim here, been out on the moors for a few hours
this morning. Not a good day for playing with antennas.
- Got a good price for the PCB fabrication from a local
(Todmorden) manufacturer and I added up the parts cost,
In UK pounds for the populated boards:
prx-e1 E-field front end: 23.67
prx-t1 Filter, line driver, PSU: 52.73
prx-r1 Line receiver: 24.42
About 100 quid for the set, not including boxes and
cables, etc, and doesn't include assembly and test.
Well that's a bit cheaper than I thought it would come
to. Will complete the breadboard testing this month
and have a set of boards built up in April and then some
Further back in the pipeline is prx-h1 which is an
H-field front-end developed from the loop receiver I
currently use, and a -p1 isolated power supply.