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Re: VLF: Earth antenna transmissions on a guide rail?!?? NOW on the air

To: [email protected]
Subject: Re: VLF: Earth antenna transmissions on a guide rail?!?? NOW on the air...
From: Roman <[email protected]>
Date: Sat, 28 Jul 2018 16:54:09 +0300
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Congrats, Stefan!

Pse inform us with screens as possible!


> And another update: The 5170 Hz carrier was running from 10:13...11:19
> UTC. The current was constant at about 555 mA.
> Now my last transmission for today is on 2970.005 Hz, running 590 mA,
> on air since 11:22 UTC, running for at least 1 hour...
> 73, Stefan
> Am 28.07.2018 12:50, schrieb DK7FC:
>> Update: Since 10:13 UTC i'm TXing on 5170 Hz. The antenna current is
>> 556 mA and the phase looks a bit less inductive but still inductive.
>> Despite beeing in the center of the Pfälzer Wald, i have mobile
>> internet access and so i reached my Linux PC recording the VLF stream
>> (both loop antennas). Using vlfrx-tools i managed to produce a spectrum
>> peak of 17 dB SNR after just 30 minutes!!!! (More later) So it is
>> possible with this ground loop TX antenna to transmit on 5170 Hz and
>> beeing detected in about 55 km distance! :-) These are two new
>> records for the TX earth antenna league :-)
>> I'm going to continue transmitting on 5170.000 Hz until 11:13 UTC, then
>> i'll do QSY to 2970.005 Hz which simply means i change the frequency in
>> SpecLabs signal generator driving my PA! :-)
>> 73, Stefan
>> Am 28.07.2018 11:43, schrieb DK7FC:
>>> Hi VLF,
>>> I'm sitting in my car while writing this email. I'm in JN39WI96GX and i
>>> transmit on 8270.000 Hz with a GPS locked signal generator into an
>>> about 450 m long earth antenna using two guide rails as the earth
>>> electrodes on both ends. On each end there are 16 (18) massive T-T
>>> poles holding the guide rail, providing a super good earth coupling. I
>>> measured that they are connected to each other.
>>> The transmitter is on the air since 9:08 UTC running 550 mA with just
>>> 75 W DC inout power into my hand warm lossy linear mode VLF PA!
>>> I'm amazed about the low losses! At DC i got 447 mA at 50.9 V. The wire
>>> is 0.4 mm diameter so it has 63 Ohm. That means the ground loss is just
>>> 50 Ohm !!!! Amazing! And i have no efforts to build up a ground
>>> connection here, i just need to connect the wire. Since the wire losses
>>> are higher than the ground losses, i can get maybe 2 dB more signal
>>> when buying some better wire. I already found a source that offers 0.75
>>> mm^2 100 m loudspeaker cable (i.e. 200m wire)for just 13 EUR....
>>> BTW i even have an ugly old scope here which is battery powered. I can
>>> see that the phase of voltage and current is slightly inductive, maybe
>>> 30 deg or so. So i could series resonate the antenna with some C. This
>>> is for the next experiment...
>>> The signal becomes visible on my grabber now, in 424 uHz and also some
>>> bright pixels in the 3.8 mHz window.
>>> I'm going to stop the carrier at 10:08 UTC, after 1 hour. Then i'll
>>> continue on 5.17 kHz!
>>> BTW the antenna , if it works like a real loop, is beaming directly to
>>> Paul Nicholson ;-)
>>> 73, Stefan
>>> Am 26.07.2018 17:19, schrieb DK7FC:
>>>> ...i just searched in the old emails and also on G3XBM's blog and found
>>>> this entry: 
>>>> So that is the best distance on a transmit earth antenna (or ground
>>>> loop) so far, at VLF, by amateurs.
>>>> I had a much lower earth resistance in mind but actually i just got
>>>> 0.53 A at 250 W RF power, so the losses were rather 890 Ohm!
>>>> Will it be possible to make 55 km distance at 8.27 kHz, maybe in a
>>>> lower bandwidth like 424 uHz, with power levels in the range of 50 W
>>>> only?
>>>> 73, Stefan
>>>> Am 22.07.2018 20:28, schrieb DK7FC:
>>>>> Hi all,
>>>>> During the weekend i am in the Pfälzer Wald again which is such a nice
>>>>> place to be! I already installed a fixed E field antenna for VLF/ULF
>>>>> reception in JN39XI06 :-)
>>>>> Now i have the idea to use a guide rail (attachment!) as an electrode
>>>>> for a earth electrode antenna! There is a perfect road which is not
>>>>> much frequented and where no way is crossing so i could temporary
>>>>> install a long wire on the ground between two of these guide rails. I
>>>>> would assume they provide a good grounding. They are located on a
>>>>> relatively high hill/mountain with stony ground. The mountain is very
>>>>> steep there and in some distance, 200m deeper, there is a brook..
>>>>> With some luck the ground losses can be near 200 Ohm? Maybe rather 300
>>>>> Ohm. I'm going to prepare things and plan to transmit for some time
>>>>> next weekend. If the ground loop actually acts like a loop, the bearing
>>>>> should be 135 deg, so it will be in a 45 deg angle towards my QTH where
>>>>> my grabber is listening in 55 km distance. That's quite a good distance
>>>>> for testing! I'd like to try LF and VLF, maybe ULF it all works well.
>>>>> A BTW the wire length will be 860 m! However there are two guide rails
>>>>> in a shorther distance, about 450 m. I will try the shorter length
>>>>> first, to get an impression of the loss resistance and to see if
>>>>> something is visible at all :-)
>>>>> 73, Stefan
Roman, RW3ADB

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