Mare & Gal Electronics

This is small module for splitting 1 signal to 4 receivers. It is part of the multiband SDR receiver, but it can be used standalone for any similar application.

Yaesu FT-991A Frontend has nasty hidden fault. It is not normal from €1000 radio to stop working just because you use it in a pileup situation or when your close OM is beaming toward you with QRO.

New, out-of-the box radio receive performance of the FT-991(A) was normal, but after other station(s) had transmitted at a higher power levels, the FT-991(A) receiver failed. The failure mode was as follows:

• Receiver operation is normal when the Attenuator feature is disabled.
• Receiver operation fails (no receive and a very quiet noise-floor) when the Attenuator feature is enabled.
• IPO operation enables the Attenuator and results in the same receiver failure mentioned immediately above.

Same issues are reported elsewhere:

• Yaesu FT-991A Receiver Front End Failure
• FT991 frontend gone bye bye
• FT 991 A deaf in IPO mode, receives normally in AMP modes in HF bands

Patient with exactly the same simptoms got to the operation table in my lab today. The owner is OM S52W, very successfull contester and member of the famous contest club.

There are many flight tracking services around the web and most of them are based on ADS-B receivers placed by individuals. Few months ago I put together simple GP antenna, RTL-SDR and installed Pi-Aware software. It fed data to FlightAware. Soon after one of my mod-school friends asked if I could do the same for FLightRadar24. After some search I found this github repo: Balena ADS-B Multi-Service Flight Tracker. I had good experience with balena (for LoRa gateways) and followed the really excellent step-by-step instructons. Below are some details about my installation of this Multi-Service Flight Tracker.

The plane tracker is now feeding online (with short outages) since August 2019.

Here are links:

https://flightaware.com/adsb/stats/user/s54mtb

https://www.flightradar24.com/account/feed-stats/?id=24076

https://planefinder.net/coverage/receiver/102325

“Special offer” came out for 5GHz antenna. It was posted on Polish web store Interprojekt, where I sometimes buy some equipment for long range WiFi point-to-point links.

The antenna came well packed in carton with additional box for the feed. The grids were separated with paper to avoid scratches during transport.

In this post, I will first introduce some of the basic technical background of the control of the transmit signal (PTT) and other signals (eg CW or linear activation). The second part will describe the  interface development and the final product.

Standard DB9 male connector

Continue reading ‘Small USB to PTT/CW adapter’ »

Do you ever wondered how much magnetic field garbage is around you? This is cheap and easy build to measure magnetic noise or to compare which switching supply is more sh*tty.

Near field probes are nothing new. It’s easy to find one via web search. Here is one good reference for H and E field probes which I found via google image search:

EMC near field probes for H and E field

Continue reading ‘Cheap sh*t magnetic pickup’ »

I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.

Here are the updates:

Continue reading ‘Mini CW Keyer / QRSS beacon V1.1’ »

ADF4351 is very interesting PLL chip with many features. Here is prototyping board to start playing around with this interesting chip.

Continue reading ‘Prototyping with PLL ADF4351’ »

Full bunch of wires is hanging from each HAM station and PC connected to the station: CAT, audio, each via dedicated interface for isolation or level shifting. Additional mess is with parrots or digital interfaces for digital mode. I wanted simple solution, which can be conected to PC via single USB cable.

I was looking for simple audio CODEC and found WM8731. To have enough processing power for some simple DSP audio I chose cortex M4F microcontroller. There is also micro-SD on the board for audio recording and playback, two mini-DIN connectors with YAESU pinout and galvanic isolation for USB. I stareted this project few months ago. I will add posts when I will make progress with module programming.

The PCB is 80x45mm.

Here is schematic: modem

And PCB layout: lingva

Stay tuned for further progress reports.

The software will be published on git.

I was looking for dummy load on ebay for HF testing. All dummy loads were too expensive. Then I found bag of thick film resistors. Unfortunately they were 820 ohm, which is not optimal for 50 ohm load, but close enough. Then I constructed two PCBs.

The construction is simple…

At the end I would like to put everything into oil bath to make it more suitable for high power testing.

The small SMA connectior is for measuring via the 1:10 voltage divider.

Here’s altium PCB for the two boards: dummyload (31.10.2014 21-23-06)