CAKE. Notes March 10, 2018
CAKE Session March 10 2018
First off we were pleased to welcome Richard K8SQB with us for the first time and to learn he lives
just a few blocks from RonW6WO in Capitola. It is always a pleasure to have Bob K6XX with us fresh
from his visit to the Flea Market along with Don K6GHA and Reed N1WC. Also present were K6UNO
Kerry K3RRY, Eric KK6IZY, Jim K9YC and briefly Richard W1WUH .
Bob was pleased with his flea market purchase as it completed his collection of QSTs by finding
several missing issues for 1938. In one issue he found a card (postage paid) to become a member of
ARRL for $2.50. Worth a try Bob ? Another famous bargain hunter is Richard who showed a tuner for
receiving over the air TV that he found on Ebay for less than $20. You might make a set top Moxon
Beam for it Rich.
By now all will know we appreciate inquiring minds so when Eric and Kerry get their heads together
something interesting is going on. Today they had completely dis-assembled a combination padlock
and appeared to be changing its combination, it wasn't clear if this had any criminal intent. Don
produced a tiny device and our pair hazarded a guess it was for igniting electronic cigarettes.
Maybe you are wondering if we discussed anything specific to Ham Radio. Not to worry Jim was with
us and described in detail what he was doing with a variety of ferrite cores for baluns and transformers
.We are sure to learn more of his research using a vector network analyzer known as a VNWA 3E. Jim
also recommended a program called Zplots which converts VNA data into Excel spread sheets.
The term “proximity effect” was metioned by Jim and it is one not often heard, my ARRL hand book
makes no mention of it. I referred to my boyhood bible, Terman 4 th Edition and here it is described.
“When two or more conductors are in close proximity the current distribution in one is affected by the
magnetic flux produced by current in an adjacent conductor as well as the flux produced by the current
in the conductor itself. This effect causes the true resistance to be greater than due to simple skin effect
and is particularly important in RF coils”. Just as Jim told us!!
The VNA designed by N2PK and built by Ron (and OBTW also Warren NR0V) many years ago, has
been idle for quite some time (pre USB in fact). Putting it back in service is a current challenge. The
associated PC-based software called MyVNA was developed by Dave Roberts G8KBB. The many
common functions are easy to use but understanding all (such as trace arithmetic on S parameters)
would be equivalent to a degree in communications engineering. It may surprise to many that there was
a patent issued in the 1930s for a mechanical VNA used to measure common mode rejection (CM)
Recently Ron discovered that the characteristic impedance of RG58 was altered if the outer jacket was
removed (reason for finding this is another story). Two propositions were advanced to explain this
finding. One was that removal of the jacket relaxed the pressure between the braid and the internal
dielectric, the second was that by removing the jacket, E field leakage through the braid becomes
exposed to air instead of the higher dielectric constant of plastic. Other opinions are invited.
Jim described how he has been working with Frank W6JTI to activate an extremely rare grid square. If
I have it correctly it is CN70 located in a tiny spot on the coast near Shelter Cove. Getting there
requires backpacking down a steep trail, and of course the surrounding hills make any propagation
inland very difficult. A future presentation to the Club on such an adventurous expedition would be
very much appreciated.
There you have it gentle folk and I hope to meet again on the 24th
73 for now Ron W6WO