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What is this ?
This is IBMs'   network card from the early eighties for the original IBM PC. I cannot imagine how much this card  would have originally cost. Judging by the cards complexity it would have cost more than the PC. This card predates generic coaxial ethernet (IEEE CheaperNet) by a number of years.  The analog electronics on this card is a radio modem that uses CATV cabling. IBM then saw that there allready existed a large amount of CATV cabling in buildings. The cards radio could be tuned to unoccupied chanels to establish a radio link. The radio modem is made from high quality components and I suspect was capable of full duplex operation at probably one or two megabits/second.  The IC under the heatsink at the left is a first generation Intel ethernet controller chip. The square chip is an 80286 cpu.  The network controller had ten times the mippage of the PC into which it was plugged.  IBM thought CATV cabling was the way to go because the technology was allready ubitquitous and there was a large pool of technicians that could install and terminate CATV cabling and accesories.
I found a large carton of these devices in a dumpster and it was a lucky find indeed. There are many UHF large signal bipolar transistors on this card adn they were very welcome for my ham radio activities. I dont know what this card was called or what the original cost was.


The AIRMEC type 871,  ZD 00783 OSCILLATOR TEST No1 CT212

   A very nice signal generator picked up at a hamfest for $10. Beautifully made, Larkspur like construction practices and very high biuld quality.  The paint color suggests it was made for Naval use, however, the VMARS site reveals that it was purpose biult for servicing Larkspur series equipment. Maybe the paint job determined which Service is was delivered to.   Internal components are very similar to things found inside a C42.
but now, thanks to the hard work of the people at VMARS, the complete EMER (thats manual to you! ) is available here   at  www.vmarsmanuals.co.ok/archive/files_index.htm 
some of the key words  for documentation,  EMER Tels Z341 Z342 Z344  and also T&M F142   . Look for documents numbers 1287,1288,1289 and 1290  which are complete and contain the schematics.
They are a free download, but as they are copyrighted to VMARS I cannot host the files here.

The Burroughs B7800
and my part in its maintenance.

Including burroughs chip house codes to commercial equivalents

coming up .... a history of the Network  at Monash University  to be published sometime soon in 2015

Larkspur Control Harness Project
I have three Larkspur radios. When I purchased these in the late seventies I did not want the control harnesses because there was 
no documentation and there was literally a shipping container full of harnesses and misc gear that fitted no ryme or reason. I bought suffiecient of this junk to liberate enough connectors for my purposes  and made my own control boxes. However, after many house moves most of my early stuff was lost  and just enough remains for me to construct "one harness to rule them all".  Eventually this little project will be completed and it will get its very own web page.
controls for C13,C42 and C11my poor excuse at recreating Larkspur quality!C13,C42 and C11 waiting for control harness project completionstill need to make a PSU for the C11

the talking stones
as inspired by the Black Dog

ferric chloride etching of copper PCBsA vhf/uhf grid dip oscillator
(but there is no grid!)
a PLL based signal generatorThe  selection criteria of  L C R components

making PCBs in Ozbased on push-pull balanced FET oscillatordont try this at home!an old school assignment
Home made mitre box for precision cutting of metal extrusions, pipe etc etc

This gadget was constructed from heavy brass angle stock that I found in a dumpster at work.  It had numerous holes in it allready but was otherwise intact. This mitre box permits "precision"  cuts to be made in light alloys.  My problem with the hacksaw is an in-ability to make good 90 degree cuts which this solves. But more interestingly  the use of stops  permits  reliable precision step and repeat cutting. Very nice if you have to make uniform spacers.  This mitre box permits me to make objects only slightly wider than the kerf of the hacksaw blade.   The saw guides are spaced to allow the blade free movement.  I have found in practice that two guides, front and rear were required to make consistently good true square cuts.    The guides are made in such a way as to permit alignment after assembly.  Heavy bolts permit alignment. The alignment, when achieved, is then cemeted in place with a purposely drilled hole and small snugly fitting bolt . This ensures that when you drop or otherwise abuse  the mitre box  the alignment is unconditionally held.  This mitre box was designed to be easily held in a bench vice and have ample surfaces for workpiece,  clamps and stops

 allo  allo allo...whats all this then ? coming up, an article about the care and feeding of Lithium Ion cells.  Dont try this at home. LIONs can burn and need special care and attention to keep them safe.  This will be my lightweight 20AH cell for backpacking and SOTA. So much nicer than a Lead Acid gell cell.

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last update Tue Feb  2 13:58:36 EST 2010
Fri Feb 26 18:57:59 EST 2010  added control harness notes
Mon Mar  5 18:28:57 EST 2012 added collinear antenna
Tue Nov 25 18:56:22 EST 2014
  added mitre box, lion cell image