Space Spanner.. O'Man, I could only afford the Ocean Hopper.. Man, them
were the days!

Joel AG4QC

"Steve Nosko" wrote in message
...

Steve,
Although I didn't figure it out at the time, my Knight-Kit Space
Spanner
circa 1960 had terrible microphonics - very noisy. I cleaned the entire
chassis & rewired it to no avail. Today I suspect a mica cap, the old
square type, since I heard of same thing this some time ago.

"Rich Grise" wrote in message
...
"Jim Adney" wrote in message
...
On 16 May 2004 07:06:24 -0700 (Steve
Kavanagh) wrote:

[snip]

If silvered mica caps are so crappy, why did they ever use them in
the first place?

Thanks,
Rich


Well made, they are very stable & handle considerable current. These were
top of the line. If they make junk now, so be it.

--
Steve N, K,9;d, c. i My email has no u's.

"Rich Grise" wrote in message
...
"Jim Adney" wrote in message
...
On 16 May 2004 07:06:24 -0700 (Steve
Kavanagh) wrote:

[snip]

If silvered mica caps are so crappy, why did they ever use them in
the first place?

Thanks,
Rich


Well made, they are very stable & handle considerable current. These were
top of the line. If they make junk now, so be it.

--
Steve N, K,9;d, c. i My email has no u's.

"Joel" wrote in message
...
That "Steve Nosko" wrote in message
...

Steve,
Although I didn't figure it out at the time, my Knight-Kit Space
Spanner
circa 1960 had terrible microphonics - very noisy. I cleaned the entire
chassis & rewired it to no avail. Today I suspect a mica cap, the old
square type, since I heard of same thing this some time ago.


Space Spanner.. O'Man, I could only afford the Ocean Hopper.. Man, them
were the days!

Joel AG4QC


Yea! AND, get this, I think I took plates off, or bent some, of the
bandspread cap to reduce its range and calibrated it for 40 M. Every
Saturday morning I'd listen to the same group on SSB talking about their
Collins rigs and inverted Vees.
Wish I still had it and the Knight-Kit crystal set. Had it hooked up to
a loud speaker in my room (course I was in Wood Dale, IL., not too far from
the WBBM and WGN AM transmitters...)
73
--
Steve N, K,9;d, c. i My email has no u's.

"Joel" wrote in message
...
That "Steve Nosko" wrote in message
...

Steve,
Although I didn't figure it out at the time, my Knight-Kit Space
Spanner
circa 1960 had terrible microphonics - very noisy. I cleaned the entire
chassis & rewired it to no avail. Today I suspect a mica cap, the old
square type, since I heard of same thing this some time ago.


Space Spanner.. O'Man, I could only afford the Ocean Hopper.. Man, them
were the days!

Joel AG4QC


Yea! AND, get this, I think I took plates off, or bent some, of the
bandspread cap to reduce its range and calibrated it for 40 M. Every
Saturday morning I'd listen to the same group on SSB talking about their
Collins rigs and inverted Vees.
Wish I still had it and the Knight-Kit crystal set. Had it hooked up to
a loud speaker in my room (course I was in Wood Dale, IL., not too far from
the WBBM and WGN AM transmitters...)
73
--
Steve N, K,9;d, c. i My email has no u's.

Real mica has to be real old and it sn't aging much in a capacitor because
it has been aging for eons and for all pracitcal purposes inert. If mica
capacitors are jumpy it must be due to the plating or encapsulation! If
there's no clue to the mfg it could be that these jumpy were not
manufacutured for your application. JMHO
73
Hank WD5JFR

"Steve Kavanagh" wrote in message
om...
A year or so ago I was working on a microwave local oscillator (at
about 2.5 GHz) multiplied up from a crystal oscillator near 40 MHz.
The output was found to jump in frequency by tens or hundreds of Hz
many times as the LO chain was warming up. I was able to reduce this
jumping by replacing all the dipped silver mica capacitors in the
crystal oscillator stage with NP0 ceramics. There is still a bit of
jumping which may come from some silver micas which remain in the
stage following the crystal oscillator.

I have just been observing the same sort of frequent jumping behaviour
(up to a kHz or so at a time) in another local oscillator (output at
about 10.5 GHz, phase locked to a crystal oscillator around 100 MHz).
I note that this one also has dipped silver mica caps in the crystal
oscillator and I wonder if it too would be improved by replacing them
with NP0 ceramics.

The capacitors used in both cases are from unknown sources and were
probably manufactured in the early 1980's.

Has anyone else experienced this behaviour ?

Steve (VE3SMA)

Real mica has to be real old and it sn't aging much in a capacitor because
it has been aging for eons and for all pracitcal purposes inert. If mica
capacitors are jumpy it must be due to the plating or encapsulation! If
there's no clue to the mfg it could be that these jumpy were not
manufacutured for your application. JMHO
73
Hank WD5JFR

"Steve Kavanagh" wrote in message
om...
A year or so ago I was working on a microwave local oscillator (at
about 2.5 GHz) multiplied up from a crystal oscillator near 40 MHz.
The output was found to jump in frequency by tens or hundreds of Hz
many times as the LO chain was warming up. I was able to reduce this
jumping by replacing all the dipped silver mica capacitors in the
crystal oscillator stage with NP0 ceramics. There is still a bit of
jumping which may come from some silver micas which remain in the
stage following the crystal oscillator.

I have just been observing the same sort of frequent jumping behaviour
(up to a kHz or so at a time) in another local oscillator (output at
about 10.5 GHz, phase locked to a crystal oscillator around 100 MHz).
I note that this one also has dipped silver mica caps in the crystal
oscillator and I wonder if it too would be improved by replacing them
with NP0 ceramics.

The capacitors used in both cases are from unknown sources and were
probably manufactured in the early 1980's.

Has anyone else experienced this behaviour ?

Steve (VE3SMA)

On Tue, 18 May 2004 02:31:08 GMT "Rich Grise"
wrote:

"Jim Adney" wrote in message
.. .
On 16 May 2004 07:06:24 -0700 (Steve
Kavanagh) wrote:

The capacitors used in both cases are from unknown sources and were
probably manufactured in the early 1980's.

That may be the secret here. In the past, I've used silver mica caps
in a number of applications with positive results. The only problem
I've ever seen with good quality ones was a single one in a 40 year
old HP amplifier that had become leaky.

If silvered mica caps are so crappy, why did they ever use them in
the first place?

I was not suggesting that they were crappy. I was suggesting that of
all the high quality ones I have worked with over many years, I've
only seen 1 failure.

His experience may well be due to the fact that his were of unknown
origin and unknown quality.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

On Tue, 18 May 2004 02:31:08 GMT "Rich Grise"
wrote:

"Jim Adney" wrote in message
.. .
On 16 May 2004 07:06:24 -0700 (Steve
Kavanagh) wrote:

The capacitors used in both cases are from unknown sources and were
probably manufactured in the early 1980's.

That may be the secret here. In the past, I've used silver mica caps
in a number of applications with positive results. The only problem
I've ever seen with good quality ones was a single one in a 40 year
old HP amplifier that had become leaky.

If silvered mica caps are so crappy, why did they ever use them in
the first place?

I was not suggesting that they were crappy. I was suggesting that of
all the high quality ones I have worked with over many years, I've
only seen 1 failure.

His experience may well be due to the fact that his were of unknown
origin and unknown quality.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

Thanks for all your comments. Since speculation has started here is
what I know about the capacitors.

Those used in the 2.5 GHz source are surplus from a company that makes
high quality stuff. They were probably procured to a military or
space specification but I am not sure. The 10.5 GHz source was
manufactured by MA/COM about 20 years ago. All of them are the usual
deep maroon (is that the right word ?) to brown colour.

Keep in mind I am being pretty picky. I consider short term frequency
jumps of much over 100 Hz to be unsatisfactory - that is 10-40 parts
per billion depending on which source is considered. The largest
observed jumps are about ten times this. Of course, since these are
crystal oscillators, the corresponding capacitance jumps must be much
larger, since the crystal should dominate the oscillator stability. I
would not consider them "crappy", just not as good as one might be led
to expect. I have used capacitors from the same provenance as those
in the 2.5 GHz source in LC oscillators at a few MHz with no observed
problems. The smooth portion of the warm-up drift is reasonably
normal in both cases...only the jumpiness is unusual.

Steve