Beauty and the Beast on 70cm

I am the Club’s token 70cm enthusiast. I know that the 70cm amateur allocation is secondary and that everyone, everyone, uses 2m. However 70cm is a huge band with room for everything, including any quantity of mysterious QRM, and its antennas are a sensible size, neither a shipyard job nor watchmaker’s work. Furthermore there is always the principle of ‘use it or lose it’ which applies to under-utilised amateur allocations just as it does to the use of cash.

The Club is quite well provided for in respect of FM vertical 70cm, having a Yaesu FTM-400XD which gives 50W into a dual band colinear, sufficient to work UHF mobiles and handhelds all across our area.

We have had no provision at all for DX work on 70cm. A donation provided a very fine Icom IC-251E 2m 10W multimode set, which with a suitable linear will do nicely, but since then we have been on the prowl.

70cm being historically under-utilised and 70cm sets tending to cost more than 2m ones, finding a suitable multimode set has taken some time as there were never very many to start with. Eventually on e-bay a Yaesu FT-780R was found for £125. The seller swore that it worked, but on arrival it turned out to have no RF output at all. It was duly packed up and sent off to Liskeard in Cornwall where M1APC briskly replaced the PA, also replacing the N socket, tweaking up a switch and generally tidying the rig which now looks thus:

FT-780

For myself I prefer this understated, rectilinear styling to that of blobby, biological-looking modern rigs, believing that Post-Modernism has done no more for amateur radio product design than it did for anything else.

Despite looking so nice the FT-780 is a rather peculiar shape, with a curious projection underneath and also some switches which make it tricky to put the rig down on a flat surface. It has its own mounting bracket which is much more sophisticated than the usual crude angle-bracket-and-two-handscrews kind, having rails in the sides of the rig allowing it to slide back and forth as well as tilt. This is fortunate because the very minimalist wire stand, on which along with its odd belly bulge it would once have stood, has long since been lost.

The FT-780 produces 10W on 70cm which is just right for driving a big old fashioned Microwave Modules 432/100 100-watt linear. Curiously exactly such a linear appeared as though on cue in Messrs. Lynchy’s secondhand pile and was duly snapped up. Lynchy’s crew swear that it works despite its control panel being upside down, which strongly suggests that the PCB behind it is too:

Upside down front panel

However it does at least have proper sockets (Anti PL-259 Bigotry Score = +1) on the back:

Proper sockets

As this linear draws more than 20A at 12V under full drive it will not be possible to test it in my own lab; we will have to arrange to do it at the Club, and will post the results in due course.

Naturally if all this works it will have to have some kind of antenna for horizontal polarisation that will handle 100W, which will no doubt eventually generate another report.