Well, I did my first VLF earth-mode field test today since my brain bleed in Sept 2013. Sadly, it was a total failure. I am at a loss to explain the results.
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| Tuned VLF loop |
I put the 5W, 8.976kHz, beacon on into the same earth electrodes used successfully on 472kHz (best DX on TX over 1000km) and went about 1.6km to a car park where I always had
strong signals using a tuned loop on RX and earth-electrodes on TX from the old QTH in the same village.
Nothing at all copied today - absolutely nothing. I waited in case I was in a pause between QRSS3 callsign transmissions, but no absolutely nothing at all. Not even the tiniest hint of a signal.
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| Deploying the VLF loop (Burwell in the background) |
So I parked in the road about 0.3km from the home QTH and again
nothing at all. At this point we drove home. What a dismal failure this was turning out to be. I am sure it is telling me
something but I cannot work it out. Sure enough, everything was still working at the TX end. I am using one remote ground and the mains ground at the shack end, exactly as for 472kHz. I did check this mains ground was grounded to real ground.
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| Checking Spectran on the PC - nothing ! |
Whatever utilities assistance I was getting before at the
old QTH is
not the same at this newer QTH. All very very odd. I was expecting to see
something. In the past I received transmissions from the old QTH at the new QTH (about 0.3km away) using just an E-field probe on the car. From the old QTH I spanned 6km!
In summary, this VLF test was a
total failure. I am at loss to explain things. Not only that, but the work has left me very exhausted. My brain is still foggy, but the results today were not due to any mistakes with the HW gear or PC Spectran settings.
I am not having much success today.
8 comments:
Nice day for it though.
Hope you took your sarnies, bag of crisps and a flask?
Better luck next time!
73 Steve
Yes, weather was perfect today.
Do not dispair: even a negative test is telling something hi!
Did you check the orientation of your earth loop in relation to the rx sites? If perpendicular, you won't hear much. It might also be that your new home is not connected to underground utilities as your old home was.
At my QTH there are no suitable utilities. My ODX on VLF is just 800 meters, using 5 Watt into a large (100 square meter) overground loop.
Good Luck es 73 de Robert
Hi Roger,
where did you manage to get a crystal (4.5957MHz) from that divided down to 8.976KHZ?
73 Ken G4APB
Thanks for the comments everyone. Yes a negative result tells me something.
Ken regarding the crystal I use an HF crystal and a 4060 divider. I cannot remember where I got the crystal but it was a UK supplier and expensive, as most crystals now are. If buying now I would have chosen one to give me an output at 8.27kHz as this is where most DXers are active, not that my earth-mode gets very far!
Roger - I think your day was a huge success not a failure. You've done something today that you have been wanting to do for many many months ...and you completed the task! Maybe the results were not what you wanted radio-wise but as far as personal goals went, you had great sucess!
73 Steve
Hi Roger,
just a thought, but have you changed laptops since your last success? I remember initially getting extremely poor results until I found the sound card on two PCs I had both had a steep audio rolloff above 3 KHz and was preventing me from hearing 8KHz signals.
Good to see you are at last in sufficient health to resume these experiments.
73 Ken G4APB
Ken, I have changed PC but I don't think this is the cause. MSK signals around 20kHz appear fine. Also, copy was fine in the lounge using a dummy load on the TX. I think it has to do with the (lack) of connection to utilities in the road at the newer QTH.
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