Tag: kiwisdr

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 Priyom.org 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.

Background

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 SDR.hu 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 medium wave 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.

© 2015 Dave, M0TAZ