Spending a lot of time outdoors this summer with handheld CB radios got me thinking about a lightweight 12 Volt portable power system for a mobile CB radio.
Don’t get me wrong, the Harvard 410T handheld is a thing of beauty, its just a little awkward to use over long periods and there’s nothing more comfortable than having a rig sat by your side and a proper microphone to talk into.
Thankfully the 5 Star is so light it isn’t a hassle to slip into the rucksack (even more so when compared to some of the other radio gear I usually lug around).
This is actually a battery holder used to give life to 12 volt SW receivers that get taken on radio field days and with a slightly thicker wire upgrade it does nicely for the Binatone. Using ‘off the shelf’ batteries over a something rechargeable means I can carry a few sets for the weight of a single 12v high amp sealed battery.
As you can imagine this doesn’t give much scope for output power and in true QRP style, I used the CB on low power just for an experiment (never one to do things the easy way).
Location and Antenna
Wanting to be left in peace for at least a few hours when transmitting outside isn’t an easy task these days and there’s always a fair trek to get the any suitable location. I also wanted a nice bit of height for 27 MHz to show its true potential. Luckily I have a good bit of altitude at the nearby Lickey Hills which is a short train ride and about an hours hike away.
I use the spot a lot for ham VHF/UHF operating because of the excellent view over Birmingham and the surrounding Midlands.
At first things were going down the required length of wire strung up a tree route, but I really wanted a more portable setup so opted for an old CB mag-mount whip I’ve had gathering dust for ages. Thought transporting it was going to be a problem without looking like a weirdo/potential terrorist (and possibly taking someones eye out) until I managed to bend it enough to fit neatly in my big arse camping rucksack.
At 500mw I wasn’t too worried about excessive SWR although had a quick check at home just to avoid running into any problems while I was out. With the half watt output and a nice short piece of coax I got an average SWR of about 1.3.
The battery pack gave out a nice 14.2 volt with some brand new Duracell AA’s and while transmitting the power consumption was about an amp.
In an effort to keep the amps down (and extend the battery life) I made a little mono adapter for the rigs extension speaker socket so I could just a pair of ear buds instead of the CB’s greedy built in speaker.
Keeping the rig down to its low half watt setting does make communication a little more difficult, but the standard UK FM CB band is a lot less populated than in the past and I did have a massive height advantage to play with.
OK, UK FM CB can be interesting at the best of times and takes a whole new turn over to the dark side during the evenings on the weekends 🙂 . Don’t get me wrong there’s still a few good breakers on 27 MHz FM, but for every one of them there’s are least 10 boozed up, music playing and foul mouthed morons!.
Sadly I don’t have the best location at home for 27Mhz and did enjoy spending time on 19 listening to all the people clogging up the channel while up on the hill. There was so much activity (helped by my altitude) and it was obvious that most of the people couldn’t hear each other.
Had a few quick contacts into parts of Birmingham, a very broken QSO with someone from Tamworth way but the best was a clear run down into Evesham (which isn’t bad on half a watt).
The plan was to wait around to try and catch one of the Friday night nets, but the cold got into my bones and I had to make a move long before they usually get going.
Had a few attempts at getting some video to put up on this websites YouTube channel but was constantly plagued with swearing so give up as the editing would have been a nightmare!