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Cluster Activity

Spots per uW band today:
UK spotter or spotted only.

Solar data:
SFI
2
A-Index
0
K-Index
11
Exp.K
qui
Sunspots
qui
Activity
no
GMF
Aurora?
M0DTS

My Weather

ArrayDate:17/10/21 Time:10:37
Temp:16.5C
Wind Speed:12.5mph
Wind Dir:180deg
Pressure:1010.86mB
Humidity:78%
Dew Point:12.1C
UKHASnet

Most VLF antennas are up in the air but the length of wire you can get up is limited vs the wavelength of the frequency in use, hence VERY large loading coils are required to bring the antenna to resonance. Often many kilovolts are on the wire in use.

As i'm only doing tests through earth mode (for now) i've been using an earth loop antenna.


For transmit tests I've got an earth loop antenna consisting of Earth Electrodes spaced at 40m E/W and 40m N/S, also allowing 60m NE/SW.

The 8.27KHz signal at over 100V is applied between the electrodes.



Hopefully I'll be able to extend the current earth loop length of 60m to try for some Dx....!

There's the possibility of a 240m Earth Loop but the cable would need to be buried as there are sheep in the field...they love to get tangled up or chew on on wire!


For any more information email me rob at m0dts.co.uk


Tx Amplifier is currently a Behringer NX3000 with a 120-240/50-50 mains toroid as the step-up transformer on the output.

Have plans to build a H-Bridge PA like DK7FC has done, should improve efficiency and allow more power.




VLF Tests so far:

06/2011 - First interested in VLF Comms, detected DK7FC test with Kite antenna on 8.97KHz - Found a Screengrab here!
2011 - some earth mde tests using 17m spaced electrodes, 1w power, dx ~1km.
2020 - Various Earth Mode Tests upto 4km with ~20W power - 40m spaced electrodes
14/8/2021 - 12:20-15:05UTC ~30W to electrodes 40m apart - 8270.0117
14/8/2021 - 15:35-18:50UTC ~40W to electrodes 40m apart - 8270.0117
15/8/2021 - 07:30-10:30UTC ~80W to electrodes 40m apart - 8270.0117 - 1st 'Dx' result to Todmorden, 100km!: Grabber Snapshot
20/8/2021 - Installed a new Earth spike to the east, again 40m distance.
20/8/2021 - 17:30-19:45 - ~100W to E/W 40m spacing 8270.0111
21/8/2021 - 09:45-11:45 - ~100W to NE/SW 60m spacing 8270.0111 - Better as expected: Grabber Snapshot
22/8/2021 - 09:00-12:00 - ~100W to E/W 40m spacing 8270.0111 - Grabber Snapshot

28/29/30 /8/2021 - Various tests not logged.
5/9/2021 - GPS Referenced 10MHz oscillator as Tx source now in use, freq=8270.011750. New Matching transformer in use using N30 core.
7/9/2021 - 08:00-11:00 - ~200w to E/W earth loop, visible at Todmorden but weak - No reception at G4FVP 17km away.
8/9/2021 - 08:00-11:00 - ~250w to E/W earth loop - Received by G4FVP 17km to the west of me for the first time!! - Narrow filter used on M0BMU Loop Preamp, Signal is ~8dB/700uHz
9/9/2021 - 08:30-11:30 - ~250w to E/W earth loop - Received by G4FVP With M0BMU preamp in wide band setting there was no signal detected but signal is there again with narrow filter selected.
10/9/2021 - 08:30-10:30 - ~250w to E/W earth loop
10/9/2021 - 08:30-10:30 - ~250w to NE/SW earth loop - Same strength at G4FVP as E/W, but NE/SW is longer.
11/9/2021 - 08:00-11:00 - ~250w to NE/SW earth loop - Much weaker at Todmorden (maybe 10dB less!) - Heavy rain overnight before this transmission. Soil moisture mesurements to be done before future tests.
















Last page added:25/03/00 18:32
M0DTS.co.uk