[ARC5] IIRC Stinson?s solution to sidetone issue

[David Stinson]

(Think I made the attachment too large.  Trying
again)


Thanks to Brian Clarke and Mike Hanz for jogging
my memory.

I reviewed the diagrams over coffee this morning
to blow the dust

off the creeky stuff in my old and
rapidly-emptying head.

 

The SPDT relay(s) in the receiver rack are picked
by the PTT buss.  

The Common contact is connected to the Receive
Audio busses

and their associated switching.  The Normally
Closed contact

is connected to the Receiver's pin 2, Audio Out.

The Normally Open contact is connected to the
Sidetone buss

supplied to the receiver rack.

 

Thus, in "Receive" mode, the radio's Audio Out
feeds the rack

audio busses and the Sidetone buss is
open-circuit.

In "Transmit" mode, the receiver Audio Output is
open-circuit

and the Sidetone buss is connected to the Rack
Audio buss

with its associated switching (and also out to the
RX Control Head).

In order to provide a means to Net the TX-RX, a
small toggle switch

on the display stand open-circuits these relays,
allowing the receiver

BFO (if properly aligned) to be used for netting.

See photo attached.  The switch obviously mounted
in a scrap 

adaptor box is for netting.  Please forgive the
"frumpy" look;

in the middle of refurbishing some sets.

 

Left the Sidetone buss open-circuit in all modes.

Did experiment with Sidetone attenuation schemes,
but all seemed

to affect the Modulation envelope to some degree.

I confess I did not try very hard; to do this "by
the book" would 

require the addition of an Interphone box to the
display.

 

Of course, I can't speak for anyone else, but the
point of my 

displays is to tell a story to hams in hopes of
sparking interest.

Those hams, mesmerized by the latest shiny things,
tinkling

bells and flashing lights (more expensive thingies
to break

and give the makers a Repair revenue stream)

are only half-curious to start with.

Getting them to stop the "Hamfest Zombie March"
long enough 

to talk about the sets is hard and getting harder.
Adding an interphone

box would make the display even more "busy,"
giving it an 

unbalanced look.  

 

And there is this:  In story-telling, there is an
axiom: 

"If a character does not advance the story, 

 the character should be cut."  

An interphone box would be of great interest to
you and me,

but it would not "advance the story" when trying
to ignite

a spark in a newbie.  An Interphone box adds a
complicating

element that would need further explanation.
Trust me; 

getting them to stand still long enough to talk
about the bare set

is hard enough.  Start adding elements and their
eyes will glaze-over.

Remember the goal, and Montgomery Scott's
admonition:

"The more complicated they make the plumbing,

the easier it is to stop-up the drain."

 

GL OM DE Dave AB5S

 

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