Re: LF: Continued VE7TIL LF grabber outage...

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Hi Scott

This is fascinating. Can you remind us what power you were running and what mode/bandwidth for this sea coast 10km earth mode test please?

I wonder if the signal is copyable for some distance further along the sea coast edge as there is nothing essentially stopping it other than the inverse cube (I think) attenuation rate.  It would be most interesting to know the limit along a sea coast where the seawater is a very large and good conductor (analogous to my water pipes but with rather larger cross-sectional area!). In my experiments the signal only stops when the pipes end, but the Pacific coast of Canada is rather longer, HI.

Using very slow QRSS or DFCW (or continuous carrier as for the radiated VLF tests over here) one could imagine some remarkable ranges could be possible.You sound to be well placed to try to find this limit.

Also, I am intrigued to know if best results at the RX end are with a horizontal loop, E-field probe or another electrode pair (one being in the water and one some distance in from the shore). With utilities assisted (pipes) earth mode a horizontally mounted loop always, without fail, gives the best RX signal. I still struggle to understand why this beats another earth electrode pair which is directly connected to the pipework.

Good luck with this and the radiated tests you plan at VLF.

73s
Roger G3XBM

On 1 May 2011 21:11, Scott Tilley <sthed475@telus.net> wrote:

Hi Roger

With probes with 60' base and my 1m square portable loop resonated on 8970 about 10km.

73 Scott

On 5/1/2011 1:03 PM, Roger Lapthorn wrote:

Hi Scott

I'm wondering how far up/down the coast a signal can be detected with a similar electrode probe pair (one in the water and one on land)? Alternatively looking for the signal along the shoreline with a horizontal loop or E-field probe? Could be an interesting test.

73s
Roger G3XBM

Via my 2.4GHz handheld (iPod Touch 4g)

On 1 May 2011, at 20:48, Scott Tilley<sthed475@telus.net>  wrote:

Hi Roger

The closest electrode to the ocean is feeding into a creek that itself feeds into the ocean.  This electrode is<75m from the salt water.  The other electrode is about 0.5km inland at my house.

Within about 2-3km of the setup I can run PSK250 with good SNR and near perfect copy with on about 30W feed into the antenna.  Once outside this range things degrade rapidly...

Placing an electrode into the salt water won't last too long with the beachcombers, dogs and electrofobes passing by etc.

73 Scott


On 5/1/2011 10:47 AM, Roger Lapthorn wrote:

Scott

How close to the ocean are the electrodes in the earth mode tests? Can you try with one in the ocean and one some way inland?

73s
Roger G3XBM

Via my 2.4GHz handheld (iPod Touch 4g)

On 1 May 2011, at 18:38, Scott Tilley<sthed475@telus.net>   wrote:

Hi All

The VE7TIL 2200m grabber will remain off for another week or so.  This is do to a hardware failure in a wide band amplifier in the the DDS system.  I'm waiting for some replacement parts as my efforts to make repairs with parts on hand were less than satisfactory.

I apologize for any inconvenience this may have caused users.

However, by the grabber returns to operation it will be augmented by a new VLF grabber page.  I just finished installing the loop in the garden and it is working wonderfully.  I spent the evening last night listening to tweeks/atmospherics and comparing my results on the VLF transmissions with that of Laurence KL7UK in AK...

Work on preparing a 8970 test transmission into my LF loop continues and I expect to have the time to perform QRP tests later in May.  Earth mode testing continues and so far best DX has been about 10km.    Interestingly, the best path seems to be along the shore of ocean here.  Inland propagation over the poor rocky ground here does not penetrate very far.

73 Scott
VE7TIL

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