Hi Luis & Stefan,
>>...ill try also a twisted pair instead of the coax
>>...Then you can clearly hear the hum of the QRM noises
>...There will be no improvement. I would stay at coax.
Hum means H-fields.
Coax shield is completely transparent i.e. without any effect to H-fields.
The question is where the hum is being picked up.
73
Clemens
DL4RAJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of DK7FC
>Sent: Friday, May 12, 2017 2:19 PM
>To: [email protected]
>Subject: Re: LF: Some improvements in VLF Rx
>
>Hi Luis,
>
>Am 12.05.2017 11:43, schrieb VIGILANT Luis Fernández:
>
>
> I can add an SMD ferrite bead (0805) in the gate
>
>Worth to try.
>
>
>
>
> The voltage in the coax down in the shack after the
>390R is 6V. Power supply is 14V. So there must be some current
>trought the FET
> Will measure the current
>
>Yes it is 8V/390R = 20 mA. That's a bit much. You could
>increase that resistor to get about 10 mA, maybe 680 Ohm is a
>good value.
>
>
>
>
> This is the picture of the 5m mast, which is metal. The
>last section is a PVC pipe which holds the MiniWhip. The VLF
>probe is hold in a plastic box
> containing the FET and attached to the metal mast using
>a metal adaptor. So it is quite close to the metal mast, which
>can provide high capacity ?
> Probe lenght is 1m
>
>https://dl.dropboxusercontent.com/u/7162072/fotos%20varias/MF/I
>MG_20170430_125017.jpg
>
>Looks like a good place. The 1m probe should be fine. The
>capacity is given by the probe, about 5 pF/m is the rule. 1m
>should be fine when the antenna is at this location.
>The only problem seems to be the contaminated ground. You just
>need to experiment and find the best results.
>Maybe it helps to isolate the probe ground from the mast and
>feed the cable down to the ground where it has its own earth
>and an isolation transformer between the TV cable and
>soundcard... You know...
>
>
>
> Yes. Using the battery there was no difference, once
>the ground loop was removed.
>
>Sounds good!
>
>
>
> That will be fine ! File is here
>
>https://dl.dropboxusercontent.com/u/7162072/fotos%20varias/MF/V
LF_Soundcard_32KHz.USR
>
>Modified file in attachment.
>
>
> Will try also a twisted pair instead of the coax
>
>There will be no improvement. I would stay at coax.>
>Good luck for getting a cleaner background...
>
>73, Stefan
>
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