Re: Mil 810 C, D, E for shock......Mil 810 C, D, E, for vibration in IC706/7000


MKM <starlight04@...>
 

Great story.
Thanks.

On Mar 4, 2005, at 7:08 PM, jdow wrote:


Ah yes, that is likely true about the missing analog filters.

Now the time was in the very early 70s. The setting was a small company
in Arcadia that was building a Sonobouy receiver for the S3A aircraft.
This receiver had 31 individual receivers through the low level audio
output, a 31 by 16 multiplexer, and a fancy antenna multicoupler with
a preamp from science fiction. (130MHz or so frequency Very high IMD
intercept point and a noise figure so low that measuring it required
liquid nitrogen.)

We were testing unit 1 for shock and vibration. The unit was firmly
mounted to the vibration table. It was powered up. And as I heard it
some one of the table's jockeys pulled a wire. The table went WHAM
against its stops. The poor receiver suffered. About 1/3 of the
crystal filters died. Some were degraded. And one degraded and died
as I was retesting it after the event. It seems those nice little
wires to the plated areas on the crystals in the crystal filters do
not like heavy shock and vibration. They tend to break loose. So any
receiver that can minimize the number of crystal filters can survive
more shock and vibration. This is also a good reason to have multiple
first conversion filters that can be selected arbitrarily by the user
overriding any automated selection.

Not that the 7800 gets much shock and vibration in most uses but it
should have this override capability as a redundancy feature that
leaves the radio mostly useable while replacements are on order. For
military or Homeland Security purposes such a design should be
considered a requirement.

{^_^} 62 new filters later and that radio was back in business,
in theory anyway. Now, I've forgotten how many were replaced.
But it was not "62". <sigh>
W6MKU
----- Original Message -----
From: "MKM" <starlight04@gmail.com>

Also, the IC-7000 does not require analog filters so it is mechanically
/ electrically more robust in theory.

I heard last night from the 3840 group that the rig will have digital
in / out for audio...hope it is true.

I can't wait, Icom should just release the specs now and deliver later.

On Mar 4, 2005, at 3:32 PM, Mike Valentine wrote:



Hi Tom,

I am under the impression that surface mounted components have less
mass, shorter cantilever length, and therefore much, much higher
mechanical resonant frequencies than leaded parts.

Am I missing something?

Cheers,

Mike - W8MM




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