Hi Gary
Thanks for the reply, first thing, for "10dB hump at 8.9kHz" read
20dB. Direct coupling of coax to the feed was killing the Q, I have
added a 4 turn coupling loop. The flatness was only really noted
once it was outside.
I can see the need for an amplifier on a broad band loop as with the
E-Probe which is non resonant and at a few inches long hasn't got a
lot going for it but not for a resonant loop which untuned produces
10dB of noise and resonant 30dB I am dubious still.
Maybe M0BMU will have a comment :-) please.
73 Eddie G3ZJO
On 05/03/2011 15:21, Gary - G4WGT wrote:
Hi Eddie,
Yes, you will need a pre-amp, don' forget that the E-Probe
has a pre-amp. I advise you to build the M0BMU VLF pre-amp with
7 to 10 kHz band-pass filter, circuit attached.
73, Gary - G4WGT.
On 5 March 2011 14:22, [email protected]
<[email protected]>
wrote:
Hi Gary
I am testing a very similar loop to your 1.1m square, mine
is 800mm sq. and uses Litz wire. Results at the same hight
as my E-Probe are disappointing as yet.
I have no pre amp on it, and am wondering whether it would
be advantageous as when tuned to 8.9kHz the noise level
rises by 10dB. I suppose I shall end up building an amp to
try but I would welcome any thoughts from the group.
73 Eddie G3ZJO
On 05/03/2011 12:35, Gary - G4WGT wrote:
Hi All,
Whilst monitoring 9090kHz & 8970kHz using SpecLab
at 423uHz, I am testing 3 different VLF Rx antenna
types :-
1 - An 84mH shielded ferrite loopstick (10mm x 200mm),
1 metre above ground
2 - A modified PA0RDT Mini-Whip, 8 metres above ground
3 - A 1.1 metre square loop with 46 turns of 1mm
insulated wire, 1 metre above ground
Both of the loops using M0BMU VLF pre-amp.
I have had No. 1 connected since 2000utc last night
until 1030utc this morning, no signals detected on the
SpecLab display. I have connected No. 2 at 1030utc
& notice a fall in noise level of about 10dB &
a greater visibility of the Alpha signals. Later today
I will connect the large loop & report my
findings.
73,
Gary - G4WGT - IO83qo.
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