Author Archives: Thomas

Sony CRF-330K fetching top dollar on eBay

Many thanks to SWLing Post contributor, Mario Filippi (N2HUN), who writes:

Saw this Sony receiver at a current high price on eBay:

Interesting that it has a cassette recorder, although back in those days cassettes were popular and other radios had ’em installed to record your favorite shows or to just use as a player.

Yes indeed, Mario! I remember absolutely lusting after a few radio models with built-in cassette recording features when I was much younger. It would have made off-air recordings much easier!  Of course, the most affordable (and accessible) model I remember in the past couple of decades was the vulnerable Sangean ATS-818cs or RadioShack DX-392.

I’ve never seen a pull-out cassette tray like the CK-330K’s:

It appears this Sony CRF-330K only has a few hours left of bidding at time of posting. There’s a bit of a bidding war going on, it seems, based on the bid history.

Click here to view on eBay.

I assume the CK-330K is a performer. Perhaps our resident expert, Dan Robinson, will share his comments?

Thanks for the tip, Mario!

Numbers station in a Netflix series “The Same Sky”

Many thanks to SWLing Post contributor, John Harper (AE5X), who writes:

I don’t know if you’ve heard of a new series on Netflix – “The Same Sky” is a Cold War spy series regarding an attempt to gain access to an American eavesdropping facility in Berlin in the 1970’s.

Not a lot of radio-related activity in the series but there is a scene of a spy receiving his coded instructions via a numbers station. I’ve posted a YouTube video of the scene here:

Click here to view on YouTube.

Thank you, John! I’ve just added The Same Sky to my watch list–I love Cold War spy films and series!

I’ll add this post to our ever growing archive of radios in film!

Only 24 hours to work the special Y8 call signs

(Source: Southgate ARC via Ralf Bender)

The ex-DDR call-sign group from Y81A through Y89U, not used for 28 years has been issued especially for the WRTC Championship in Wittenberg, Germany.

BUT …. These call signs will ONLY be on the air for the 24 hours of the WRTC / IARU HF contest – after that these call signs may never appear on the air again – or perhaps only in another 28 years?

All stations are built and all competitors out on their sites waiting patiently to be able to use these very special call-signs from 1200 UTC on Saturday 14th. July.

The stations will be active on CW & SSB on all contest bands from 80m through 10m. Not only is this the ONLY opportunity to work these call signs, there’s also a range of awards available for working the WRTC stations.

Full award details, live streams, on-line scoreboard and a daily news report is available from the website at

KiwiSDR network adds Time Difference of Arrival direction-finding functionality

There has been some fascinating functionality added to the excellent KiwiSDR network of online software defined radios: Time Difference of Arrival (TDoA) direction-finding functionality. has posted an informative article about this new feature and how effectively it works:

The KiwiSDR is a US$299 HF SDR that can monitor the entire 0 – 30 MHz band at once. It is designed to be web-based and shared, meaning that the KiwiSDR owner, or anyone that they’ve given access, can tune and listen to it via a web browser over the internet. Many public KiwiSDRs can be found and browsed from the list at or by signal strength and location on this website.

One thing that KiwiSDRs have is a GPS input which allows the KiwiSDR to run from an accurate clock, as well as providing positional data. Time Difference of Arrival (TDoA) is a direction finding technique that relies on measuring the difference in time that a signal is received at over multiple receivers spread out over some distance. In order to do this an accurate clock that is synchronized with each receiver is required. GPS provides this and is able to accurately sync KiwiSDR clocks worldwide.

Just recently all KiwiSDRs were pushed with a beta update (changelog) that enables easy TDoA direction finding to be performed with them. Since many KiwiSDRs are public, this means that right now anyone can browse to a KiwiSDR web interface and start a direction finding computation. You don’t even need to own a KiwiSDR to do this so this is the first freely accessible RF direction finding system available to the public.[…]

Of course, as the KiwiSDR network grows, TDoA accuracy will increase.

If you’d like to host your own KiwiSDR, you can purchase the full setup at SeedStudio or for $299 US (affiliate link).

Check out’s full article and TDoA tests by clicking here.

Click here to go to the KiwiSDR portal.