G3ZJO/M     G3ZJO/P

THE PAST

It comes as a surprise to some to learn that in the UK we used to have to apply for and pay a separate fee for a Mobile Licence. But we sure did, and kept a separate mobile log book.

In the 1960's Top Band was where the main mobile activity took place. I was impressed one day when G3OQJ listening on a valve broadcast receiver at work heard G3SIJ/M some 7miles away. Stan G3OQJ had provided his boss with an intercom telephone (rare in those days). Stan ran the wiring as a 600 Ohm open wire feeder straight down the middle of the warehouse, about 150 feet, an ideal Top Band antenna. The workshop AVO signal generator was zero beat onto G3SIJ and the output tapped onto the intercom wires, a solid contact was established.

Possibly the strangest mobile I have will ever use was the PYE Cambridge VHF radio telephone which I converted to Top Band, I inserted a transistor front end receive board and re-built the valve transmit strip.

Early 2m mobile used AM with horizontally polarized antennas (the halo).

In September 1971 I went mobile with FM and a vertical whip only to be told " you can't do that, no one will talk to you as they run AM horizontal stations ". My reply  " I think one day we will all run vertical FM ".

THE PRESENT

Whilst impressive contacts can be made on HF using mini aerials best results will always be obtained from efficient design large diameter loading coils. 

Click on the Pic. to ENLARGE

80m mobile antenna loading coil 60mm dia. 300mm long glass fibre former 14swg wire

On VHF of course full quarter wave verticals are easy, mag mounted on the vehicle. For omni directional portable use I find it useful to elevate the antenna, using a dipole, mounted on a length of plastic pipe so removing the need for an elevated ground plane. Mounted at 45 degrees this arrangement is efficient for both horizontal and vertical polarization. 

THE CARAVAN

I have two birth caravan (trailer) it makes an ideal base for mobile/portable operation sometimes we find a location for a 14 day stay high on a hill, miles from civilisation the ham's dream QTH..

I have taken several photographs of my antennae on the caravan so why can't I find even one? To follow, sorry.

A problem with caravans is antenna mounting and cable entry. My arrangement for heavy HF whips can be seen in the picture this system uses a spare towball to take support from the hitch. It will only fall over when the caravan falls over, (not tested)

Cable entry should not interfere with the water integrity of the van, bearing in mind manufacturers guarantees. My solution uses a fabricated bracket mounted on the draw bar, this carries a PL259 socket into which aerials are plugged, the cable from this enters under the van through a standard ventilator grille.

Pictures soon!