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LF: Re: 136kHz Getting started..

To: <[email protected]>
Subject: LF: Re: 136kHz Getting started..
From: "Alan Melia" <[email protected]>
Date: Sun, 3 Jun 2007 21:18:08 +0100
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Hi Rob as dave said it is quiet at the moment. I found attaching a gen to a
loop can give silly answers, and you can finish off far enough off resonance
to seriously affect the signal levels. I connect my generator to a small
coil about 8in diam with about 8 turns or any-old-wire. Set the two loops in
the same plane with the exciter look a couple of diameters of the big loo
along the axis. Then peak the main loop. I get quite a bit signal from DCF39
on 138.83 here the field strength is about 1mV/meter and that vives me an
S9+32dB signal from a 12m high Inverted L.. You will get a little less on a
loop but not that much less with a large one.
Most of the "accumulated wisdom" is summerised on a couple of big tutorials
on Rik Stobbe's web site, and he has lots of links to other projects

It occurs to me that depending on your location you may need a low-pass
filter between your loop and the rx to keep out MW  BC stations, the 612 is
not the best intermod performer, but is adequate if protected sufficiently.

The use of a PC "waterfall" program (ARGO is popular, free, and easy to use,
and works with most on-board sound cards I think) is very useful for
identifying QRM and also spotting weak signals.

Welcome to LF ( which stands for Lotsa Fun !!)
Alan G3NYK

----- Original Message -----
From: Rob, M0DTS <[email protected]>
To: <[email protected]>
Sent: 03 June 2007 14:25
Subject: LF: 136kHz Getting started..

> Hi All..
> Just found this list and seems like the only sort of forum on the net to
> do with LF!
> I'm just looking into 136kHz and looking for a few pointers..
> I've temporarily built a loop similar to G3LDO's super loop (but not in
> the pvc tube) and got it resonant but cannot tell how high Q it is..
> Only equipment i have that will check the loop out is a DDS wobbler unit
> that i can connect up across teh pick up loop and see it is resonant
> around 136-138kHz...
> I'm feeding the loop into a simple sa612 mixer and 100kHz LO and sending
> the IF into the sound card at 36-38kHz.
> I've only got basic knowledge of home brew stuff so looking for a simple
> setup to get me receiveing to see if it will be worthwhile making a
> transceiver for the band...
> So far I've not seen anything on the band apart from qrm...hi
> especially on 137.4  +/-100Hz a noise band that is always there.
> Are there any beacons active all the time or is there anything just
> outside the band i can look for to check the system is working?
> When are the best times to find stations active?
> Any comments welcome!
> Thanks
> Rob
> M0DTS - IO94IL

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