I’ve had plenty of Transatlantic QSO’s using radios I’ve built from kits, but I had never scratch built a radio for a band higher than 30m, or scratch built a voice mode radio. I thought that I might as well combine my goals and aim to build a scratch built voice mode rig suitable for DX contacts.
At the beginning of 2014, I started looking for suitable designs to meet my needs. I canvassed opinions at the Blackpool rally, stating my ultimate target of a home brew DX voice QSO. The general opinion was that I should build a double sideband suppressed carrier transceiver featuring a direct conversion RX. I bought a few components and went home from the rally deep in thought.
A few months passed by and I was listening to SolderSmoke http://www.soldersmoke.blogspot.co.uk/ and Bill, N2CQR, the host was talking about his ‘BITX’ radio. ‘BITX’ is a design by VU2ESE, it uses the same basic amplifier block throughout, and uses a ‘bidirectional’ architecture. A lot of the circuit is shared between RX and TX. The beauty and appeal of the BITX design is that it uses very common (cheap!) parts, there’s lot of troubleshooting information and Yahoo support group, and it is a single sideband superhet transceiver.
The BITX design was shouting out to me! I contacted Bill, N2CQR, and asked his opinion as to whether a common or garden ham could build such a thing. The answer was simple - go for it! Those that know me will know that I get a kick out of minimalist radio - the simpler the better. I intended to build my radio with a traditional VFO, true to VU2ESE’s design, I didn’t want to be experimenting and ending up in a mess. Recent episodes of SolderSmoke have featured Pete Juliano, N6QW. Bill had copied Pete in on the emails and Pete put forward his case for a DDS VFO. At first I resisted, but then having thought about it and my battle with the MKARS80 rig to keep it on frequency on a cold summit (it’s fine in a warm shack BTW), I decided that Pete was probably 100% correct!
Oh no, now I had to learn enough about Arduino to get an AD9850 module singing to the right tune! Pete was a great help, shooting back emails from California with new titbits of information. By October, the Arduino / AD9850 DDS VFO was up and running with a flashy white on blue four line LCD.
The main PCB came together nicely, I only made one mistake, incorrectly connecting a resistor in the RX IF amp after the crystal ladder filter. I found my mistake as soon as I started sweeping my filter bandwidth and I noticed that my IF amp was attenuating rather than amplifying! By the end of November, my board was up and running as a receiver.
The main board was finished and ready for a first on air test by the end of January 2015.
A first try into a proper antenna had me punching the air and beaming from ear to ear!
Now with the rig working, I needed to put the circuit into a suitably robust case for SOTA. My step dad came to the rescue, neatly bending up a box from aluminium sheet. I choose a black colour scheme, with blue LED / Display on a bare metal front panel.
I finished the rig during this week and declared it ready for a SOTA outing! (Yes, its a home brew mic too!) There’s more functions in the Arduino code than I need, the RIT is the most useful. Arduino code is by Paul Darlington, M0XPD
I’m really trying my best to reach Mountain Goat status, I’ve been doing SOTA since 2004, but it came along just at the wrong time for me. I have two sons, 8yrs and 2yrs and family time takes priority. I like to cash in on winter bonus points, there’s more gain for the same outlay! Over the past couple of winters, the weather has always seemed to be poor for the day allocated for my SOTA outing.
It had been planned that I would do SOTA on Sunday 1st March, but a look at the weather forecast told of high winds. The forecast for this morning was much better, although it would be foggy on the tops. I decided to swap my SOTA day for today instead. I needed to back home by 1pm, so a local summit had to be chosen. I decided upon Sharp Haw, G/NP-029 as this is one of the nearest qualifying summits to me that I hadn’t done this year.
With it being an early morning activation, the long path propagation to VK was something that I thought I should be exploiting. A look at the VOACAP propagation tool (http://www.voacap.com/) promised a small chance of a path peaking at 0800utc. I reckoned that I needed to be on air by 7am. My alarm clock batteries decided to die in the night, so I was 45 minutes late getting out of bed. As it happens, I was set up with the home brew radio ready to go on air at 0725.
The default power on frequency is 14.200, straight away heard an Australian accent coming through the speaker, things were looking good! I tuned up towards 14.285MHz, but it seemed that the whole world was working DX. I ended up finding that 14.315 sounded clear and nobody responded to ‘is this frequency in use’. I managed some multi-tasking by self spotting and calling CQ at the same time (I haven’t managed this yet with my usual CW, good job the RBNgate does it for you!) Trade was a bit slow to start, but I was pleased when Vlado OM1AX called me with a nice sounding strong signal - great, the rig was still working!
After working a few Eu stations, I heard a faint ‘VK1’ coming through the speaker (I love it when a plan comes together!). There is no AGC on the rig, so I turned the AF gain up and Ian, VK1DI, was coming through nicely, not strongly though, from Canberra. Ian gave me 33 and I returned with 55. I was over the moon! I shot some video, but unfortunately the mic was facing the wind and you cant hear the QSO 
I think it’s worth sharing my reaction though! -
http://youtu.be/Zxyu8tX3Zhc
Further VK QSOs were to follow with Gerard, VK2IO, Tony, VK3CAT and finally Ernie, VK3DET at 0755utc with a solid signal.
Pleased!
What a fantastic end to my project, I’m surprised at how everything has worked so well from start to finish. I’m very grateful to all those involved in my journey from first time home brewer for the LA1KHA PP3 challenge to reaching the point of achieving DX QSOs with a home brew SSB radio. SOTA and the great people who take part have been the driving force behind all of this.
Thanks to all for QSO’s today, every single QSO was special.
73, Colin M1BUU
Signal was pretty weak at my end but you had picked a good clear frequency so could read you okay. My home station antenna is only a 20 m dipole so not much gain, but had 100 w to call you with.