Re: LF: Earth electrode antenna tests

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Your findings also tie up with mine Tony. 

On 136kHz the 20m spaced TX earth electrode behaves as a loop in terms of far field directionality with nulls orthogonal to the line of the electrodes and strongest signals end on. This also ties up with my WSPR reports on 500kHz which came from N.Holland, Tring and Bristol i.e. in the line of the electrodes with no reports orthogonal to the electrode alignment. 

On 0.838kHz the best orientation when picking up pure induction signals (up to around 0.5km) was orthogonal to the electrodes. When receiving "utilities assisted" conducted signals 5.6km away the orientation did not matter, which is what one would expect.

There is no doubt in my mind that this sort of "antenna" behaves like a loop on 136 and 500kHz. 

By the way, good luck Stefan with the earth electrode DX tests.

73s
Roger G3XBM

On 17 August 2010 16:11, Tony <ei8jk@o2.ie> wrote:

 Hi Stefan

I tried the antennae this afternoon on 23 KHz and the E/W wire is 12dB up on the N/S wire.
I have no idea what I was receiving as I was using a FRG-7700 which only displays to the nearest KHz.
When I disconnected the far end from the earth stake the signal dropped by 18dB, the receiver is at the eastern end of the E/W wire and the northern end of the N/S wire.

I will try sub 10 KHz when I sort out where my local QRM is coming from.

Tony, EI8JK.

On 16/08/2010 22:16, Stefan Schäfer wrote:

Hello Tony,

Thanks for that interesting work!
Could you extend the measurements to the VLF band? It would be interesting what the levels and directivity would be there.

73 and pse a sked for your upcoming LF stn! :-)

Stefan/DK7FC

Am 16.08.2010 16:35, schrieb Tony:

 Yesterday I spent some time playing with different antennae.
I started by laying out another wire 52m long orientated roughly north/south and then I shortened my original wire also to be 52m and this one is east/west, both terminated with an earth rod.
Results were not as expected however as although the two earth electrode antennae show most definite directivity they were the wrong direction.

I monitored BBC R. Bristol on 1548 KHz which is about 500 Km due east of me and on the inverted L (tuned VSWR 1.6:1) I could just detect a carrier heterodyne, on the N/S earth electrode antenna it was S1 but on the E/W earth electrode antenna it was S3.
RNE5 on 531 KHz about 960 Km due south of me was S3 on the E/W and S8 on the N/S

HGA22 (135 KHz) to my east was S4 on the E/W and S1 on N/S

Readings were taken about 12:00 utc so most definitely ground wave.

I was expecting the directivity to be broadside on the earth electrode antennae, but they seem to behave like a Beverage in that respect, but something that I think I will investigate further, maybe see if there is any difference if I terminate them with a resistor.
I'm sure Mal is correct though that they would be useless to TX through but for RX they seem to have possibilities especially after dark as they are a lot quieter.

All good fun.
73, Tony, EI8JK.

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