[R-390] Capacitors

[Tisha Hayes]

"It can be expensive to go with OEM spec parts. It will not be too many
years before people will be laughing at those who would replace a dead tube
with a tube instead of a FET substitute circuit. (Quieter, cooler / less
power use, more linear, longer MTBF, etc.)"

They already laugh at us. I do not think that many of us are into tube based
gear so we can win a popularity contest. If you told someone that you owned
an R-390A you are likely to be met with a blank stare of incomprehension.

Many amateur radio operators do not know of anything more than 12 VDC. If
you follow some of the sites like eHam in the amplifiers forum you will find
people with a shocking (no pun intended) misunderstanding of what 2000-3000
volts will do to a person. You can get knocked dead by the B+ in most tube
gear and I suspect that most of the people who follow this mailing list have
gotten a kick from HV before.

(actually, I think that some folks do it repeatedly as a form of
electro-convulsive therapy <j/k>)

There have been a few write-ups done on folks who have taken the RF deck
from a R-390/A and used it with a radio that is solid-state from that point
onwards. (blasphemy! <g>). One thing you can say about a multiple band,
multi-stage, permeability tuned RF deck is that it is not small nor is it
light. Certainly there are quieter IF designs out there where you do not
rely upon a string of offset tuned IF stages and mechanical filters that are
a bunch of metallic disks tack welded together with coils on each end.

If you have never tried it, take the diode output on the back panel of the
radio, couple it through a capacitor and feed it into a high quality audio
amplifier. It is truly a treat to listen to. If you want to dip further
back, take the 455 KHz IF and go into a Sherwood Engineering SE-3.

Yea, if you were really into it you could solid state the entire radio. I
too have been tempted while looking at the schematics at the idea of
sticking a HEMT in as the first RF and adding a balanced mixer with a high
stability, spectrally pure frequency source. It would be one freakish
receiver with cams, gears and sliders that like to bathe in Mobil 1, mixed
with circuitry built on teflon substrate, cooled with liquid nitrogen and a
rubidium referenced oscillator. One thing you can say is that it would not
be a R-390A any more.

Back in the 80's I spent a great deal of my working day in a Faraday cage.
If it was not for it being so drafty it would have been a great place to
relocate my office into. The big latching door handle and gasketed door
frame was impressive enough to keep people away. I ran across a pile of
Faraday cage panels at a local electronics surplus place a few years ago. By
the time I went back they had stripped them down for the value of the copper
screening. What a shame.

-- 
Ms. Tisha Hayes/ AA4HA
----------------
"I'll be a diode, cathode, electrode
Overload, generator, oscillator
Make a circuit with me." -- The Polecats