How to exchange the GU74b / 4CX800 tubes on your Alpha91b (Alpha99) Amplifier

it finally happend…. After a decade of reliable service, my Alpha91b amplifier broke. Most likely on it’s way to Spain one of the tubes broke. During the comissioning at ED1R contest station, fire & smoke shot out of a chimney. The first shock was big, but a few measurements confirmed that just the tubes were broken. In this blog post I will share the knowledge I gained during during debugging, comissioning and breathing new life into the amplifier.

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When antennas come down

During CQWW CW we had a shootout from ED1R with our friends from the Bavarian Contest Club. The group around DQ4W organized a Contest-Expedition to Corsica (TK) to get on the air as TK4W. Considering the available antennas, (two A3S, and three verticals) they generated a great score. For details comparisons between ED1R and TK4W click here.

Ulf, DK5TX created a serious of cool stop motion videos of the antenna work. Unfortunately, including the moment when one of the 17m tall masts came down and damaged the mounted A3S severely.

Fortunately nobody was injured and the A3S still worked, even being a bit deformed.

Building a beverage switching box

Listening on Beverage Antennas on the LowbandsThis year we wanted to seriously compete in CQWW CW from ED1R contest station. While the station is equipped reasonably on all bands with Yagis and verticals, there were no dedicated receiving antennas available – yet. Out of my former contest participations from other stations I know that when it come down to winning a CQWW, dedicated receiving antennas are a must have. Beverages provide great directivity and reduce the EU clutter significantly.

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PowerSDR-UI – knobs for your SDR radio

At the end of last year I announced the “proof” that Software Defined Radios also can have buttons and knobs. At that stage the software was still a prototype and not ready for a public release. In the meantime I was working hard to eliminate bugs and implement further improvements. By today I’m happy to announce the release of PowerSDR-UI beta. This is a call for beta testing. Please feel free to download the software and participate in the beta testing phase!

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The portable dog killer

Security Now! is one of my favorite podcasts and a weekly “must listen”. The heart and soul of this podcast is Steve Gibson. Steve is a true “builder”. Ever since he loved to build stuff. Beside of his “geekiness” he is an excellent writer and story teller. Most of the topics he has already covered (like all flavors of encryption) are still up to date, but there is one episode which deserves special attention: Episode 281 – The portable dog killer. Its a story of Steves youth. Back in these early days, when transistors were still something exciting and new, he built a special kind of (non-lethal) weapon to educate the neighbours dog…. with unforeseen consequences.

The reason why I recommend this particular episode, because it is to entertaining to listen, but also so educating at the same time. He explains in such a great way how much fun it is to actually “build something” instead of playing video games in front of your TV. Gather your friends, your kids or your grandkids  around your stereo and let yourself inspire!

SDR Resources

This is a list of SDR related Hardware and Software project. It is intended as a living document and will be updated whenever I encounter a new project or product!

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Let’s build a computer!

Security now - How computers work While the average users mainly use the PC to surf  the web and to order every now and a book on Amazon, we, the Amateur Radio community are using PCs much more intensively. Especially in Software Defined Radio appliances, the PC is a central part of the system. So are you aware what DMA, ASM and ROM are? Do You know the difference between L1 and L2 cache? If not, I’ll show you a great way how you can gain a deep understanding without going to college again.

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5B4AGN sets up new W3NQN Bandpass Filters

w3nqn_bandpass_filterA couple of minutes ago I was informed by Bob 5B4AGN that he developed W3NQN style Bandpass filters. Probably the most important information is that he is taking orders for PCB.

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Debugging the RS232 serial port


Debugging Serial Communication FT1000MP Win-Test CW-Skimmer

In this article we will investigate how various Contest programms (Win-Test, N1MM and CW-Skimmer) communicate with the FT1000MP shortwave transceiver over the serial port. We will see what happens when multiple programs try to talk to the transceiver at the same time, what problems appear and how we can successfully monitor and debug them.

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Measuring ICE Bandpass Filter

ICE Bandpass filter with TAPR VNA

Today, I had the possibility to measure the performance of the well known ICE bandpass filters. Read more about the measurement results…

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