Month: February 2017

Interesting Signals on HF

Sony Pro80 Receiver

I’ve always been interested in listening to the short wave bands, with my first receiver being the Sony Pro80 receiver. The Sony was a portable HF receiver that covered from 150 kHz to 223 MHz and was powered by 4x AA batteries. The receiver was excellent on the HF bands, and this receiver provided many years of reliable service.  I quickly realised that most of the interesting signals were outside of the broadcast bands, in the early days listening to the phone patch signals from troops in the Gulf war talking to their loved ones back home. Many of the signals were in the clear, simple analogue SSB signals.


HF Path Sounder


The advent of SDR receivers has allowed you to visualize and listen to signals, providing a unique view into how signals are modulated and propagate on the air. One such signal that caught my eye was this one seen on 11.14 MHz. It looked a little like OTHR, but was far too narrow and the way it increased and decreased its frequency did not look like anything I had seen before.  I checked with  Peter Martinez G3PLX (inventor of Amtor and PSK) who is world renowned for his technical expertise in these matters and he suggested an HF path sounder. A device that tests the HF propagation conditions, in some cases jumping around the HF spectrum. Something that I’ve never seen before, but without a spectrum display I may have never been able to identify this type of signal. Thanks to Peter for his assistance.

Sounds Like a Numbers Station

Much speculation has been published about HF number stations, one thing is for sure they have declined in popularity somewhat since the 1990’s. They were often found in the HF bands, 5 to 10 MHz being the most popular, and it’s now quite rare to find one on the bands without a little preparation. I was interested to see a station that sounded like a traditional numbers station on 6.739 MHz USB the other evening. It turns out this is not a traditional number station but generated by the USA military.



Firsttoken a youtube users suggests

This is not a “numbers station” (but calling it one is a common mistake). This is a transmission of the US Military HF-GCS network. These messages are called “EAMs”, or Emergency Action Messages as rangers199487 points out, in the hobby community. There is some question as to if all such messages are truly EAMs or not. These transmissions happen daily, many times a day. Common frequencies are 4724, 6739, 8992, 11175, 13200 and 15016 kHz. Many other types of signals are heard on the HF-GCS.

Numbers Station

Number stations are still around, and by checking the schedule at you can simply look up and listen to the next scheduled transmission. This example is broadcast on 8157 kHz USB.

Viewing the Bands in a Contest






The Kiwi SDR enables you to view to view up to 30 MHz of spectrum at one time. This can help identify areas of activity and provides a unique insight into how the HF bands are used.

KiwiSDR 10 kHz to 30 MHz now online.

The SDR is online 24×7 for your enjoyment. If you find the SDR useful consider making a small donation to help with its upkeep.

Listen to my SDR

KiwiSDR User guide 

Access other SDR from around the world.

Buy one online.


In April 2016 the KiwiSDR project was born on Kickstarter, the plan was to produce a software-defined radio (SDR) covering shortwave, the longwave & AM broadcast bands, various utility stations, and amateur radio transmissions, worldwide, in the spectrum from 10 kHz to 30 MHz.

Fast forward and the project has now been completed with the first units having been dispatched

The first time I used one was when Dave G7UVW added his to the website. Dave has recently moved his SDR to a remote site in the Secret Nuclear Bunker Kelvedon Hatch. You can listen to this  SDR online.

After using it for a few weeks via the web browser I was sold, it was ideal for HF monitoring, and with remote access with up to 4 independently tunable receivers.

The idea of having your own web-based SDR always online, and accessible from anywhere in the world was very appealing and coupled with an active antenna the performance if very good. The advantage of the active antenna is it works well over the entire HF spectrum, it’s especially good below 5 MHz.

I use the Wellbrook loop mounted outdoors at around 5m, but you may be interested in a much less expensive project version as detailed by George M1GEO.

The SDR software has a built-in WSPR decoded that works really well, and with time they hope to add further features.

I’ve been updating the station text, its work in progress but I’ve added quite a few of the mediumwave station names.

Have a listen with my SDR, I understand Safari, Firefox and Google browsers work best. The display is not mobile friendly at the moment, but it does seem to work OK on the IPad.

Be sure to let me know how it works, leave us a comment and don’t forget to include your town/country or callsign.

MX0SNB Operating CQ WW WPX RTTY Contest

This weekend was the CQ WW World Prefix Contest (WPX) and RTTY has never been so popular. The bands were once again packed with RTTY, with most of the big contest stations making their mark. I used the Secret Nuclear Bunkers club call MX0SNB, as its quite rare and was more popular than a standard M0 call this weekend.

The basic setup is here.

The Expert 1.3k-FA purring along at 400w.

Using just a doublet antenna and a 10m vertical and I was active on 7, 14 and 21 MHz.

Its possible with a small antenna and some power to have some fun on the bands, here was a spot added to DX summit from DL2SAX “Big Pile up RTTY

7 MHz was mostly EU although the band can throw up the odd surprise later in the evening. Operating time was casual, just fitting in some RTTY in between other tasks. In total I managed to work 359 stations in 52 DXCC.

I used the Expert 1.3K-FA solid state linear amplifier, with around 5w drive and 400w out. This was the first time I had tried the linear with sustained contest style usage, and it coped very well. Even with frequent CQ calls the temperature never passed 43 C.

Most of my contacts were around EU, although a few DX did get worked.

Maps produced by SH5 contest log analyser

Enjoyable few hrs on the band, thanks to everyone we worked. The prefered QSL method for MX0SNB is LoTW and EQSL.CC, although we will reply to any cards via the bureau (VIA M1GEO).

The results have been published


Canvey Radio Rally 2017

The first rally of the year Canvey, organised by SEARS can sometimes be snowy, cold and wet being in February. This year it was quite mild, so no need for the snow boots thankfully.

Transport was provided by Peter G0IAP, and we were joined by Dave G7UVW. We arrived in good time around 9.45 and noted people already starting to congregate outside the door, we opted to remain in the warm car and await the door opening. The doors opened shortly after 10, and just £2.50 provided you entrance to the multitude of lovingly used vintage items (OK junk) on display in 2 halls.

The main hall was busy with the usual mix of traders and Special Interest Groups. Peter M0PSX from Essex Ham had information and a display video showing 2016 events.  It was good to see Charlie M0PZT from Ham Goodies  both very busy, in fact I didnt really get a chance to chat with either Peter or Charlie as they we both so busy dealing with punters!

The RSGB has a book stand and this was well staffed with the usual helpful volunteers from team RSGB.

Walters and Stanton had a good display of items, giving Essex amateurs a chance to ask about the changes to their business model.

Tea, coffee and the infamous bacon rolls were on offer from the serving hatch in the main hall. I think we all remember the year Canvey rally didn’t serve any bacon, it almost caused a riot in the streets. Thankfully special attention has been give to catering, and further disasters has been averted.

Nice to catch up with so many friends from LEFARS, Secret Nuclear Bunker CG, Essex Ham and the RSGB. I has a nice catch up with Dave G4ZST and Riche M0TYA while browsing some junk.

Here you can see Dave G7UVW giving the sniff test to a recently acquired vintage light meter.

A chance to rest your feet.

So what bargains did I find ?

A couple of project boxes and some heat shrink, but rallies arent about the junk you buy more about the people you meet and a chance to chat.