These pages last updated on Monday, 04 February 2008
Some illustrative examples of some aspects of my obsessive -compulsive gathering behaviour! Over the years I have collected KWM2/KWM2A ,51S1, 75S1 ,32S3A, 32S1 , 75S2 , 32S1 , the KW2000B in the top left corner is a English copy of a KWM2 that was marketed in the early 60 s also the Black Collins ART13 aircraft rig that was standard equipment on the B17&B29 Superfortress bombers with a pair of Collins 390A receivers.
Click on the small pictures for a higher resolution image.
One of Bernie's most recent projects. A kW Antenna Tuner. Looks like it should be good for 5-6 kilowatts! It's hard to get a true idea of the overall physical size but I'm guessing about 300mm high and 550-600mm deep.
A 4-400A linear with 4KV supply and iron powder tank circuit; also showing detail of tuned input which is switched from the main tank switch with a right angle drive, it transforms 50 ohms input to 25 ohms which is the impedance of three tubes in parallel.
2 x 4-1000A Linear Amplifier
This is a Grid driven arrangement with a pair of 4-1000A tubes, 6kV on the plate and 1kV on the screens its 7 bands and fully neutralised with 6 Watts of drive giving 4800 Watts into a dummy load the power supply is fully interlocked with overload, air and sequencing circuits and is connected via an umbilical cord to the R.F. deck. This project is still a work in progress. I have had it working but I would need to rewire the radio shack with special wiring as when you whistle it takes 45Amps from the 240V mains my present mains supply is limited to 15Amps !
This linear is a Copy of the Collins 30S-1 linear with a 4CX-1500B and 3kV on the plate. It also covers 160 metres and utilises vacuum capacitors as the tuning and loading functions. The Roller Inductor is also home built and cost $70.00 to get silver plated. It is made with the same fibreglass that the Plate trannie bobbin is made from. The tube is running in SUPER CATHODE Configuration; which is to say that the R.F. voltage is applied to the control grid and the cathode in the same Phase. Compared to G.G. operation there are advantages in doing this although the cathode drive voltage is higher, the feed-thru power is greater, the need for negative bias in the grid is much reduced and the screen can be grounded, adding greatly to stability. Much higher linearity is also achieved thus resulting in lower values of inter-modulation distortion. -40 db has been measured with tube in this Linear. Also pictured is the Home made Plate trannie made with a couple of sec hand C Cores stripped from a scrap yard , The secondary is wound with 0.7mm wire which is rated at 1 Amp The 3kV supply is in the bottom level and the minor power supplies and housekeeping circuits such as timers and sequencing circuits. Airflow and other interlocks are all done with relays. Good access to the power supply and R.F. deck is aided by 'pull-out' instrument slides [Also from the scrap yard]. This Linear has been in operation for 25 Years at VK2ABN.
An all band G2DAF transmitter from the RSGB handbook. The PA stage is running in Class "A" with 2 stage Breune Neutralization. Output is 10-15watts. Mostly made from 'junk' recovered from old B&W TV sets. The dial was acquired from the 'bones' of a KW Viceroy which was given to me by a local Ham.
This page last updated on Monday, 04 February 2008
