Down-sizing or de-cluttering, 14th February 2023

Farewell 40m CW transmitter

I have already disposed of a home-brewed 160 metre transmitter, power supply and two modulators. They have gone to a good home. I have just photographed my 40 metre CW transmitter prior to its departure to the same good home. This transmitter is built into a re-cycled case and is equipped with three crystals 7030, 7052 and 7.200 and dates from the late 1980s or early 1990s. I did not add a socket to attach a modulator. There was little use of AM the on the 40 metre amateur band then. SSB was king! Now 7.125 Mhz is a sacred site and is used by the AM fraternity as a meeting place. Sadly I do not have a crystal for that frequency, but maybe the new owner can source one here or from overseas.

Photo shows front panel of transmitter. Note the two holes in the front panel near the plate capacitor. I never mutilate panel metres by modifying the label, The metre shows the plate current and you simply tune for a dip, peak the load capacitor and then re-dip.

Top view of transmitter. Note the four pi RF choke near the load capacitator. Secondly, the load capacitor has a 5/8 of an inch shaft. A very good friend on mine, the late Clem Tilbrook, VK5GL, turned up a brass bush 3/8 female and drilled and fitted a grub screw with a quarter inch female end for a tuning knob.

Rear panel showing SO239 socket for the antenna and a 1/4 inch socket for a morse code hand key. I covered some holes with printed circuit board and painted it with aluminuim paint. The old-fashioned dymo labels date the device.

The end view shows the 7.2 Mhz crystal plugged into the front panel and the other two crystals are wired to a rotary switch. In earlier times this style of transmitter would have required three valves: an oscillator valve, an RF amplifier and a rectifier. Threee goes into one! The rectifier is now full wave solid state with four silicon diodes and more efficient than an 80, 5Y3GT or a 6X4 valve and the oscillator and RFamplifier are in one glass envelope, a 6GV8, a very efficient valve. The tank coil is next to the 6GV8 and the output circuit is a pi arrangment (capacitor, coil and capacitor). And there are no key clicks!

We plan to leave at the end of the year after 20 years in our paradise. Four seasons, quietness, RF quiet as well and good neighbours, some humans but mainly birds and marsupials. Three into one is also a metaphor relevant to my down-sizing. reducing the size of my station considerably and saying good bye to all the bits and pieces of I collected over the years and my home brew projects, believing I might just need them in the future!