Going Portable with Ham Radio
I recently worked up the courage to go out and operate my radio in public. My loft is far too small to easily rotate my new 10 element yagi antenna for 2m band. Here are two photos…
The second was taken by my housemate, who posted it to Snapchat with the caption "Why am I spending my Saturday night like this…" - Good question! Primarily because it's fun! But also, the noise floor is so low when you're not surrounded by noisy ring-mains and switch mode power supplies. When operating from home, I can have between S4 and S6 when no one is transmitting which makes it almost impossible to hear anything.
If you are familiar with the campuses of the University of Nottingham, you may have recognised the signage in the background. The altitude of this little hill in Nottingham has an altitude of roughly 70m. Not very high, but good enough to get my signal out across Nottingham at least. My own house is at around 38m and surrounded by large metal industrial units.
The yagi was pointing south, and I was able to pick up APRS quite easily from Leicestershire using my Kantronics KPC-3. I only made one CQ call because I was being eaten alive by gnatts, but it ended it resulted in a nice chat with someone in Nottingham (wow, that yagi came in handy…). To make matters worse, it was being picked up from the east - from the side of my antenna.
In total, I took the following equipment:
- Kenwood TM-V71E 2m/70cm transceiver,
- 10 element Yagi and some coax,
- Camera tripod to hackishly mount the yagi to something,
- Kantronics KPC-3 + a few cables,
- Emergency jump start / tyre pump car battery thing.
The majority of this stuff fits into a small camera bag. I carried the laptop in my rucksack and the yagi and battery separately. The biggest issue was the battery - it is far too large and heavy. A little research online suggests LiFePo4 (Lithium Iron Phosphate) is a good choice, because the voltage range is fairly stable as the battery is drained and the cells are able to deliver a large amount of current.
I want to do more of this kind of thing. A friend has suggested Silverhill Wood, which despite the name is quite sparse at its highest point - around 170m. I'd also like to try HF portable because noise is probably an issue for this too, so I ended up ordering a PackTenna Mini. This is a very compact long-wire antenna system which includes a 9:1 unun for impedance matching. I've played with this a bit at home and can pick up lots of stations, no one seems to hear me though. Perhaps I will walk up Snowdon again at some point, lugging a radio behind me.
Finally, upon writing this I realised I had forgotten what the difference between "Mobile" and "Portable" is. This page offers a good explanation, but to summarise - mobile is moving, where as portable is fixed but temporarily.