This is my first contest with the KX3 2m module. I started late, having first had my bi-weekly CWOps training session. I packed up the radio, antenna and other equipment and headed out to the crag. It took two trips on foot from the car to carry the equipment to the crag to be on air just before 10pm. I was able to stay on air for about 20 minutes until rain came and I had to pack away.
This outing allowed me to experiment with a couple of new techniques. The equipment list is as follows:
- Elecraft KX3 with 2m module
- 20Ah AGM Lead Acid battery
- OWL 5el beam antenna
- Zoom F8 Field Mixer/Recorder/Interface
- Audio Technica Headset
- Laptop running CubicSDR
The Antenna System
The antenna was fitted with an Arca-Swiss camera mounting plate and mounted to a heavy camera tripod via a ball head. This allowed very easy rotation using the head’s rotation axis. The ball head allows the antenna to be rotated easily into vertical polarisation and if needed pointed at any angle. The whole system works incredibly well, such that I’ll leave the mounting plate permanently attached and buy a new one for the camea.
Sound and SDR
The Zoom F8 provides up operation at up to 96kS/s when run in sound interface mode. this can provide an input to CubicSDR giving me a band scope nearly 48kHz either side of my tuning point. The Zoom will not record in this mode which is unfortunate. I can enable recording but I drop the sample rate to 48kS/s. This could still be very useful.
I did not make too much use of the SDR. I was able to find signals quite well tuning around. The KX3 is certainly a good receiver. The aggressive screen lock and password protection on the laptop meant that often the screen was off.
It is possible to see vertical traces on the waterfall. I’ve performed earlier experiments with the Zoom and found a lot of emissions via the USB cable on the 2m band. Even though this was some way from the antenna, I suspect I am receiving those emissions. They were also audible as heterodynes when tuning around the band, though they did not stop operation. I could notch them out on the receiver if needed. In the end I just ignored them.
Channels 1,2 of the F8 provided the I/Q input for CubicSDR. Channels 3 and 4 provided the stereo audio from the KX3 and were routed to my headphones. They also provide the radio’s own transmit foldback monitor function, so I did not have to route my own microphone into the headphones to hear myself. The microphone on channel 5 (next to the headphone socket) was routed pre-fade to the Sub Output at microphone level into the radio for transmit audio.
The KX3 can certainly hear well. I heard a lot more than I’m used to hearing. A good position on a high point with the antenna on its tripod likely helped. Replying was a little harder needing more power to break into pileups. That said, my contacts were on the back of the beam so my effective radiated power in the given directions was hindered! The antenna I use seems no longer sold. This looks like its replacement (Inovantennas LFA 5el 2m). If the figures are similar then my ERP on the rear lobe assuming no cable loss will have been 300mW! Maybe with cable loss we can call that 150mW. I still managed around 100km in these conditions, with a signal report around “55”.
One challenge was log keeping. I was writing on a waterproof notepad, but it is fiddly in the dark. I operated transmit using the XMIT switch on the KX3, not trusting the VOX circuit to wind noise. (The F8 was set to filter at 200Hz to reduce this). I can see the advantage of computer logging. It would also make sense to log frequencies and who was operating where.
The hands free operation of the headset, along with a footswitch, should allow operation of a computer logging system. This is something to practice in future. I could try making up adapters to connect the headset to the radio, or stick to using the F8 with option to record.