Monday, January 18, 2021

HF noise at my home

Since moving to our smaller home in Thornbury I've been observing the noise on HF. It varies widely. Sometimes, 40m has broadband S9 noise.

At other times it's pretty good.

Sometimes the noise appears to be from a switching power supply (and this pattern is repeated all across HF!)

20m can be pretty good at times.

Yesterday I had a good voice contact with Ray, VK2ELO. One thing that stands out is, what I presume to be, over the horizon radar. Normally pretty narrow but this one sweeps more than 250kHz.

The noise canceller I built can work on the switching noise but can't help with broadband noise. Sometimes the most practical way to do ham radio from a suburban home is to transmit locally and receive via a near by WebSDR.

Saturday, January 09, 2021

Be careful of prices for ham radio gear on eBay

Searching for an end fed half wave antenna tuner kit on eBay I came across this amazingly over priced product:

Amazing but the reviews are all good (or fake). They've sold 665 of these so that's a pretty good business. What appears to be exactly the same product is advertised for much less if you scroll around.

Peter, VK3YE, has a recent video on the topic of second hand ham radio gear purchasing.

Peter makes some excellent points. You don't always get what you pay for, particularly as technology marches on.

Friday, January 08, 2021

Elecraft MH3 Microphone cord frays

I like the Elecraft KX3 very much but unfortunately the MH3 microphone cord has spontaneously frayed for me. Looking around the internet I can see that I'm not alone.

The repair isn't impossible but it is rather fiddly. I wasn't able to re-use the strain relief and have replaced it with shrink wrap. Here's the colours of the wires for future reference.

I hope Elecraft can choose a different cord in the future so this doesn't happen.

Stephen, VK2BLQ, sent me this picture of a Chinese manufactured mic that came with a CRKits radio. It looks the same and has the same fraying. Perhaps Elecraft gets their mics from the same source?

Sunday, January 03, 2021

Apple Silicon Fldigi but no sound yet

The x86 version of Fldigi for macOS doesn't run on an Apple Silicon Mac. It's the first thing I've run in to that didn't work in emulation. Prompted by a tweet from @xssfox, who had done a native build but run into sound problems, I have also been able to build. 

Looks good but when I try to select PortAudio...

I see this in standard out:

||PaMacCore (AUHAL)|| AUHAL component not found.||PaMacCore (AUHAL)|| OpenStream @ 8000 returned: -9999: Unanticipated host error

Here's how I got it to build

Xcode is installed. Homebrew is installed.

brew install automake

brew install libsamplerate

brew install portaudio

brew install fltk

brew install libsndfile # I already had this

brew install hamlet

brew install xmlrpc-c

brew install pkg-config

brew install zlib

brew install lzlib

brew install libpng

brew install --build-from-source portaudio libsamplerate hamlib libpng fftw

export CPPFLAGS='-I/opt/homebrew/include/'

export PKG_CONFIG_PATH=/opt/homebrew/Cellar/zlib/1.2.11/lib/pkgconfig

export LDFLAGS='-L/opt/homebrew/lib'

mkdir ~/Developer

cd ~/Developer

# get the source code whichever way you prefer

cd fldigi-fldigi


automake --add-missing



./src/fldigi # to run!

It looks like this is an issue with PortAudio on macOS 11 when built against the macOS 11 SDK. "PA/CoreAudio uses some "deprecated" APIs which fail on Mac OS 11.0 #218".

This issue in PortAudio that deals with the issue.

Friday, January 01, 2021

House battery meter for the van

While the solar charge controller in the van has a volt meter in it, the display is very small and difficult to read from many angles. I've now added a much easier to read battery meter.

The meter itself came from this AliExpress listing. It was AU$5.81 and, as often happens these days, I spent more on the box and connectors than the electronics. It draws very little current and even the backlight turns off after settable time.

Four magnets with holes are bolted to the corners of the box and they work too well - the box comes apart before they let go of the van wall.

Monday, December 28, 2020

Scratch built uSDX from VK2BLQ

I took the easy path building the uSDX transceiver by ordering a board to build on but master home brewer, Stephen, VK2BLQ took the harder road and scratch built his. It is a thing of beauty (click to enlarge):

 He has sent a report of his experience so far.

"The progress so far with the scratch built uSDX as most of the parts were in the parts box or already existing.

The computer doesn't have Paint, sorry no labels on the PCB but I think that you can see the components.

The chassis and front panel were for a project in the works and merely redirected to the uSDX so the pots are redundant unfortunately the large LCD has no back light.

You can see the micro-controller board  that has little on it, just the chip, 20 MHz crystal and resistors.

The demodulator section uses the 74HC4053 created by Tasic YU1LM (DR3 series) and Miguel PY2OHH (#195). Since then, PY2OHH has incorporated this into his USDX Nano version.

It proves the concept, but has quite high conversion loss so would need a RF amplifier, the original FST3253 is much better and I wasn't going to waste the only one I had. 

It  seemed to me that the Class E output is used because of the hack of the original QCX and the higher efficiency so 

perhaps even Class C would still work providing there is  a tuned amplifier, linear amplifiers would work too, but defeats the purpose of the design. 

I don't comprehend  the magick that creates SSB from the 328P and the phase shifted CLK 2 of the SI5351, but it looks to be some sort of gate modulation of the three BS170 FETs. That extra FET I don't think actually worked properly anyway. You might see that there are only two FETs, as I blew up  the other three, and the filter is a simple PI.  Avoided is the tuned Class E  and band pass filter as there wasn't enough room.

Building the demodulator board was little more than a direct conversion receiver and tested OK with a couple of signal generators and a CRO.

Your eyes are better than mine so I didn't modify the SI5351 board and just plugged it in, maybe for Morse it will be fast enough.

The first sketch used was 1.02 ver e loaded into a normal older Arduino Uno displayed signs of life on the 20x4 lcd. This meant the LCD would work, thereupon it was transferred to the receiver board. There were are couple of problems due to "Murphy's whiskers" and bad solder joints but did receive in a fashion. Fixing the faults and loading ver m was a vast improvement. The added functionality with the morse keyer and demod during sending and receiving is a real plus.

It may be a factor of the 74HC4053 and the Si5351 but there are a bunch of birdies ( is that a flock ) throughout 40 m, the FST3253 could be better. Then again, the UBITX V6 is no better. 

The next version needs a bit of a rethink into layout. I would be interested if any really smart people can pare down the sketch to make it suitable for use by a 16 MHz Arduino Uno board, perhaps not SSB or elaborate display. The whole project is super clever and could be good for the current generation of homebrewers.

As you know, the project isn't over until the cabinetry is done, so it gets a wooden box, which got a bit warped before the glue dried and is out by a millimetre or two which is a pest. The spray on stain took a while to dry and dribbled a little, next time use a different stain.   

Any way, that is my adventure  with the uSDX,


Great stuff Stephen, I am in awe of your home brewing skills and persistence.

Saturday, December 26, 2020

Receiving High Altitude Balloon telemetry

Facebook might be useful for something. I noticed a post from Mark Jessop, VK5QI, to say that there was a High Altitude Balloon (HAB) heading towards Melbourne from near Adelaide so I thought I'd have a go at receiving the telemetry on 70cm with my vertical. The signal is on 434.199 Upper Side Band, 25mW.

The decode software was downloaded via here and I was happy to get a few decodes.

If you upload your position will show you on the map.

The balloon is about 230km from me and the signal is very weak but I do get decodes from time to time. Great stuff!

There's a video about this fascinating work here: