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LF: Noise cancelling by using optic transmission of RX signals; amendmen

To: <[email protected]>
Subject: LF: Noise cancelling by using optic transmission of RX signals; amendment
From: Stefan Schäfer <[email protected]>
Date: Thu, 17 Dec 2009 01:00:36 +0100
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Thread-index: Acp+lxx/qujYoWOaRWimQ3vuSUXi+QADtvmw
Thread-topic: LF: Noise cancelling by using optic transmission of RX signals; amendment

Hi Dave, LF,

Yes, a transverter would be an other possibility but it would be much more complex I think, just when regarding the needed power (compared to a LED). And you would get new problems when you receive on a “new” frequency, e.g. in the 2m band when there is another noise that is not coming from LF ;-)

 

I have a further idea:

DL2CH, Hans-Hellmuth Cuno (who was even qrv on LF before some years) presented a laser TRX in the CQDL (I think 2001). I have built this TRX and did some fascinating tests with a simple laser diode out of a laser pointer. I satisfactorily transmitted music/AF via the laser beam on a distance of 200m without a noticeable quality loss.

Instead of a transmitting LED and fibre optic cable it should be possible to transmit a LF signal via a laser beam to the shack. We could call it a 2,2km/650nm transverter ;-)

Let’s imagine someone has a garden in a distance of 200m, perhaps on a hillside apart the city where no qrm is, but with a road between the house that makes it impossible to use a cable. So he could operate e.g. a grabber to the internet from that clear region! Sure, if there is strong rain or fog and so on, it will be difficult but that are all possibilities, one could try without the need for much energy! I would try this with my laser TRX but there is no need for me (not yet) in the moment.

As we know, there are existing internet links via laser beams since many years…

Another word to the fibre optical transmission: Sure there are many methods suppressing noise coming from the coax screen. The optical solution is just one. But I think the advantage is, that this method decouples the preamp from the RX for 100%, say with an attenuation of 1000000000000000 dB (to come back for joking ;-) ). There is no need for choosing the right core out of the right material and the right number of turns at both sides of the right cable that is placed in the right way and so on and on. If the optic method is used, this theme is just finished, just like the question “would it even be better when I apply 10 turns more or take 2 cores and/or bury the coax 5m into the earth?”

Perhaps it’s no so easy as I think but in the moment it seems to be a good solution for me that is really working fine.

GN or GM de Stefan/DK7FC

 

 

73, Stefan

 

-----Ursprüngliche Nachricht-----
Von: [email protected] [mailto:owner-rsgb_lf_group@blacks
heep.org] Im Auftrag von Dave G3WCB
Gesendet: Mittwoch, 16. Dezember 2009 22:27
An: [email protected]
Betreff: LF: RE: Noise cancelling by using optic transmission of RX signals

 

Hello, Stefan.

 

This is very interesting. I have a MiniWhip on a pole some distance from the house, and it seems that most of the interference (ADSL hash) seems to be re-radiated by the coax outer and picked up by the antenna.

 

A relatively short optical link of one or two metres may still reduce the pick-up, as it would break the "copper" connection to the antenna.

 

Alternatively, it might be possible to transvert the amplified LF signal up to a vhf frequency and then set up a remote RX some distance away.

 

You could switch the power on and off by using a pressure switch from a discarded washing machine connected to the shack by a lenght of 6mm plastic tubing. Apply slight positive pressure to turn on the antenna circuitry!

 

73, Dave G3WCB IO91RM nr Windsor, S.E. England. 

 

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