Activity on 500kHz

Activity on 500kHz

With only 3kHz to play with in the UK most of the activity on the band is on normal CW and QRSS (slow CW). There has been a little PSK31 activity and it is expected that there will be experimentation with other data modes in due course. Ofcom have not said how many NOVs have been issued and we don't expect them to, but it is estimated there are around 20 active stations and probably quite a few more who have not got round to getting their stations on the air yet. In the early weeks there was quite a lot of activity with many itching to try out the new allocation. That has dropped off somewhat of late, maybe the novelty has worn off or they have found it harder than they thought.

Propagation on the band is somewhat like that on 160m. In the daytime propagation is mainly by groundwave and QSOs to 100-200 miles is possible by well equipped stations. At night the longer distance stations come. Some people have heard the USA experimental stations in their band and copy of the German and Swedish ones is also possible. During the summer months operation is made more difficult by the presence of thunder static, which 500kHz seems particularly badly effected by and may be a reason for the current drop off in activity.

All operators on the band, including listeners, gain a lot from the RSGB LF reflector. This was originally set up for our 73kHz and 136kHz slots and has been expanded to include 500kHz. It is a useful forum for exchanging ideas about equipment and antennas and also to exchange information about recent activities and alert others to new faces on the band. To join the reflector follow the instructions on the RSGB Spectrum Forum website.

What have I been hearing?

The first impression I had of the band was that signals were strong despite the low 100mW erp. Quite a few of the stations are copyable at up to s9. My noise level also seems to be relatively low and normally causes no problems - I was particularly concerned that this might not be so as a few years ago I had terrible noise on 136kHz from a neighbour's TV, and I am right in the middle of a suburban estate where a high noise level seems inevitable these days.

To give you an idea of what the band sounds like I have made a few recordings of stations I have received as follows:

G3DXZ Retford 15 July 2007
G3KEV Scarborough 4 June 2007
G3OLB Sheldon, Devon 4 August 2007
G3UNT Maidstone 2 June 2007
G3VTT nr. Rochester 5 June 2007
G3XAQ Canterbury 5 June 2007
G3XIZ Biggleswade 4 June 2007
G3YXM Birmingham 29 June 2007
G4GDR Swindon 16 June 2007
GM4SLV Shetland Is 30 September 2007
GW3UEP 25th July 2007
GW4HXO Haverford West 16 June 2007
M0BMU Hatfield 29 June 2007

As I hear new stations I will endeavour to record these as well and upload them to the same place. If your signal is among the recordings I would welcome comments (email address on my home page).

Argo screen shot

I mentioned earlier that some of the operators use QRSS, or slow CW. This is a technique where the morse characters are sent very slowly and at the receiving end copied via a computer sound card. It allows very weak signals to be copied below the noise level where they would not be audible by ear. 3 second dots are commonly used on 500kHz, dots as long as 60 seconds have been used in transatlantic tests on 136kHz, so a QSO takes many hours! Argo, a program developed by Alberto, I2PHD, is a popular software for decoding QRSS, find it on his weaksignals website.

I have never been that much of an enthusiast for QRSS, but have had a short listen on the mode using Argo. This screenshot is of SM6BHZ, the stronger upper trace, signing BHZ and DI2AG, on 505.1kHz. In the evenings SM6BHZ peaks 589 so QRSS is hardly necessary - he runs around 10W erp, much higher than other stations, and it clearly makes a difference. I have also heard DI2AG by ear, but he is much weaker.

Stations worked at G3YMC on 500kHz

Callsign      Name          QTH                Locator

G3AQC         Laurie        Chichester
G3KZU         Mike          Oxford
G3OLB         Tom           Honiton, Devon
G3UNT         Brian         Maidstone
G3VTT         Colin         Rochester          JO01GK
G3WCB         Dave          Iver, Bucks        IO91RM
G3XAQ         Alan          nr. Canterbury
G3XIZ         Chris         Biggleswade
G3XVL         Chris         Ipswich            JO02NB
G4GDR         Adrian        Highworth, Wilts
M0BMU         Jim           Hatfield        

December 2007 - I am currently taking a break from 500kHz so that I can use the vertical on 160m during the winter season. I hope to be back in the spring.

500kHz Websites

There are relatively few websites specifically for 500kHz, but the following is a selection of associated LF and MF sites.

G3YXM - very active on 136kHz in the early days. Extensive site with lots of links and now with a small section on 500kHz.

G3NYK - Alan is a propagation expert on 136kHz and he has an extensive site with links. Also a 500kHz erp spreadsheet.

M0BMU's FET PA Transmitter producing around 11W on 500kHz.

PA0SE's Field Strength meter - several ops have modified this for 500kHz and have been taking measurements with interesting results.

Roger G3XBM - a fellow QRP enthusiast who now has some 500kHz pages on his website.

G0MRF 500kHz low pass filter - as used in the G3YMC transmitter.

John GM4SLV - in the Shetland Islands, currently the most northerly operator on the band. You will find a recording of G3YMC there!

USA 500kHz group website - what goes on across the pond.

G4WGT's pages - Gary has some pages on short vertical antennas not dissimilar from mine.

Sites will be added as they become available.