|
As you will of already gathered , all of my operating is done using qrp. I have now decided to go down another route and have decided to close the home shack down and concentrate on /p and /m work. There were two reasons for this, firstly i had a lot of money sat around idle in the form of radio equipment that simply wasn't getting used. As i found myself mainly working 40m on 2 watts it seemed a waste having a few multiband radios when i had an mfj cub that would do exactly what i wanted.So im in the process of selling up except a few bits and bobs. I will be keeping one of my 817's ,a couple of small qrp cw trx , a vswr meter and things like dummy loads and a few antennas .The second reason is im bored sat in the shack, especially in the summer months and as im saving at the moment for a trike the extra money from the sale will come in handy.. So i find myself on another learning curve and am looking forward to see what can be achieved using what will most likely be comprimise antennas for convienience .
My mobile set up.
Above is my mobile set up. Its situated in the tool compartment in the back of my van. Radio is an mfj cub for 40m along with an mfj 902 tuner . The tuner is there on bypass when used with the 40m pro am antenna but i want the option to mess around with different antennas in the future or maybe wires from the van along with my 817. BELOW is the pro am on the rear quarter panel of my van. Not the best location but the roof has 5 sunroofs so very little metal so the side of the van may well be a better option. My idea is to homebrew a multibander center loaded antenna using a mast to get as much of the antenna/coil ect out the way. This is simply my initial move from the house into the van so all work is in progress.On a recent trip to porthmadog in wales i worked into europe using this set up with very little problems using the roof mount although the tx did seem to be doing better than the rx so as i say work in progress.
bonding/resonating and matching
In my eyes the best way to go with mobile installations is as i have done in the past is to lower the ground resistance as much as possible by bonding all panels using copper straps and literally bond anything you can. My last car could of been in a pile up and im sure the bonding would of kept the thing together. Resonating the antenna instead of simply tuning for a low swr ( which doesn't have to be the same) and which if using an analyser is where the (X) reactance is zero then matching the feedpoint impedence to coax is the way i will eventually go once im out of the house properly with the radio gear.For now though its a matter of simply getting on the air and as i have already made contacts into EU using this set up it is working to a degree, all i can do now is make it more efficient as i want all my 2 watts in the air..
well my first move to a more efficient mobile set up was to strip the pro am whip i initially started /m with and used the blank to make the above 40-10m center loaded antenna. proper tests are yet to be carried out but it will out perform the pro am range of whips on all bands no doubt. Including the cost of the pro am whip this antenna cost around £20 to make .
next job is to do some bonding on the van and then tune the antenna to resonance and then shunt feed it to match the feedpoint impedence up to 50 ohm on the lower bands..
|
