Ceramic filters on 472-479kHz?

An eBay seller from Hong Kong has 100 off 472kHz DIP ceramic filters on sale for £5.31 delivered to the UK. See item number 400305093888.

Some filters similar to this have useful bandpass characteristics and acceptably low insertion loss (around 3dB), so may be seriously useful for 472-479kHz rigs and transverters. For example, as a roofing filter to protect a RX after a small gain stage, or as a filter to clean up the output of a transverter at low level before applying a signal to a driver and PA. I guess they must also be useful in a ceramic stabilised oscillator.  Anyone used these in similar applications?

WSPR on the new 472-479kHz band

For the first time I've been monitoring 477kHz USB dial for WSPR signals, hoping to copy some of the Germans now allocated the band. SM6BHZ is on too, but not yet seen.

At 2058z DF0WD was copied at -27dB S/N for my first German WSPR signal on 477kHz at a distance of 556km. I have also heard a couple of other stations from elsewhere in W.Europe who appear to be testing at very low power before the band is officially released in their countries.

500kHz WSPR and OPERA compared

Today I've been comparing OPERA OP4 and WSPR performance by running my QRP beacon in daylight in both modes for several hours each on 500kHz. Theoretically OP4 should outperform WSPR by a few dB, but I am getting roughly similar reports from stations 126 and 210 km away in both modes.

Personally I prefer WSPR because of the neater on-line reporting system and user interface, shorter TX period (2 mins rather than 4 mins) and the fact that more data is being transmitted (call, power, location). Unfortunately only a couple of UK stations have been looking for my 500kHz WSPR signals, so the test is a bit limited.

SAQ VLF tests today

SAQ, the very old alternator TX on 17.2kHz VLF, was transmitting today and was copied as far away a North America. Here are some recordings made in Germany by Stefan DK7FC.

Dear VLF group,

Today the S/N of SAQ was much weaker here in Heidelberg/JN49IK, probably due to the high QRN levels.

I extracted a wav file containing the full message and tests. Can be used for reprocessing if of interest for someone: https://dl.dropbox.com/u/19882028/VLF/SAQ/SAQ_afternoon01Jul2012.WAV (117 MB)

And here is a mp3 file for listening in a normal player (first 2/3 is a test procedure, then the mesage comes): https://dl.dropbox.com/u/19882028/VLF/SAQ/SAQ_afternoon01Jul2012.mp3 (24 MB)

73, Stefan/DK7FC

MF bands and local comms

This morning with my 20mW ERP on 500kHz I worked G3XIZ around 45km away on CW. Chris gave me 569 (on his meter) when using his loop antenna on RX. He was a very good signal here. Earlier I copied the other stations in his net M0JXM and G3DXZ. Yesterday G3KEV was a good CW signal and PA0A was copied later today.

500kHz QRP transverter with ferrite rod ATU on bench

The new 472-479kHz will be an ideal band for local area CW nets: as my far less than ideal set-up here proves, one can work up to around 45-50km without any problem even with very low ERPs. Running 6dB more power from the PA (I currently have just 5W out) will help further.

This afternoon my 500kHz OPERA has reached yet another new station: G8ALS in Coventry 126km away. My maximum daytime range on OPERA OP4 mode seems to be around 220km, although a few more stations reporting may increase this.

500kHz ERP

Using the coax feed to my 10m/6m halo as a vertical I've worked out the ERP currently on 500kHz OPERA. The RF power from the transverter is around 5W from an IRF510.

The 10m and 6m halo lengths correspond to a horizontal capacitance of around 35pF. Some of the feed from the shack to the bottom of the vertical section is horizontal through the loft and this has not been included (I think it may add loss though). The vertical section outside is 6m long, equivalent to a vertical capacitance of 36pF. Using standard formula this means my effective height is around 4.48m.

Radiation resistance then works out as 0.088 ohms.

Measured antenna current is 0.48A (using a current transformer and detector)

ERP = 0.48 x0.48 x 0.088 = 20mW (or lower if the losses are higher).


 

First 500kHz OPERA reports

Having managed to match my 6m long coax feed line (as a Marconi vertical) up to the 10/6m halo antenna on 500kHz by adding some inductance wound on a ferrite rod in the shack, I've just received my first OPERA beacon reports on the band from ON6EO at a distance of 220km and G0KTN at 210km. Reports were -30dB and -29dB S/N which is marginal.

OPERA mode on 500kHz

500kHz OPERA RX this afternoon (on left are my spots)

Having now uploaded the latest version of OPERA weak signal mode software I have been looking on 500kHz using my, as yet, untuned short vertical antenna. CPU load without waterfall is running at around 40-50% on my Dell Inspiron 630m and the PC is running in a stable way. So far copied PA0A, PA3ABK and M0FMT. If I can get the antenna resonated crudely I may try OPERA TX on 500kHz later this weekend.

10m ROS16 QSO

ROS16 10m QSO this morning: my first for some time

The last time I tried ROS and OPERA on my PC it reacted badly and crashed so I'd been reluctant to try the mode again in a hurry. However, today I loaded v7.0.9 which runs OK when the waterfall is deselected on my 6 year old Dell Inspiron 630m with 1GB RAM and a 1.73GHz Intel M processor.  As an initial test I ran 5W on 28.185MHz and managed to answer a CQ call from DK6SQ who reported me at -13dB S/N.

Denmark active on 472-479kHz band

In the last few days OZ amateurs have been granted access to the new band. Along with Monaco and Germany there are now 3 countries (to my knowledge) allowed to use this new LF band. It has been confirmed that The Netherlands will get access on Jan 1st 2013.