2 Frederick - Plantronics Mo 1273 FSK Teletype Keyer/Demodulators - Mil Spec

Description

For Sale:
A pair of used Fredericks / Plantronics Model 1273/S1 FSK Teletype Keyer - Demodulators each set for a custom shift.  Shift frequency is determined by two crystals labeled Mark & Space on the Tone Keyer board inside the unit.  The installed crystals are shown in photos. The I/O lines are attached from the rear and there is a switch to toggle I/O to coax (75 ohm) or open lead (600 ohm).  Construction is mil spec: G10 boards with protective coating.  Power supplies appear good as units power up and all fuses are good.
We have available a full copy of the original Fredericks/Plantronics manual.
The top unit is crystalized with 2100 kHZ and 1500 kHZ crystals and the bottom unit has
Mark 2182.5 kHZ and Space 1417.5 kHZ.  According to the manual, these can operate at 300 Baud & 75 baud.  The top unit has has a 10 Turn vernier dial replacing the original pot.  The bottom unit has its original in place.  Both units seem to have been changed more than once but I have no history on them, only the pencil marks & actual installed crystals.  The baud rate boards both have multiple 10 turn pots on them and, in general, think they are a good opportunity to turn one back into its original 850 shift keying and the other into a 170 shift set.  I'm guessing at this but I think there is a good chance I am right.  In recrystallizing, consider using 2125 kHZ for the MARK frequency for both 170 & 850 shifts; use 2295 kHZ and 2975 kHZ for SPACE respectively.
Condition:
Excellent physical condtion.  This sale includes a copy of the original manual.  An experienced teletype person should have an enjoyable time with these.  As you see in the photos, the right lower unit no longer has it's AC cord grommet and the right front decorative panel bumper is missing.  These are aluminum but you should, if you have any experience working with materials, be able to fashion a suitable replacement.
Terms:
Sold as described but strictly as is.  We do not accept returns as we are downsizing and not retailing.
Shipping:
We are estimating the single shipping.
Teletype Enthusiasts:
The best way to support the teletype interests of amateur radio is to put a RTTY or AFSK or FSK signal on the air.  It does not matter if anyone comes back to you right away it only matters that signals start populating the teletype areas.  Get other amateurs used to hearing teletype as well as honoring the traditional teletype spaces.  Use prearranged schedules to QSO with other teletype stations when you can.  Eventually the mode will catch on and use will increase.
If you need transmitting equipment to do this, I have several vintage tube based units that will work fine.  You know the rule:  use it or lose it.  Let's not let it die without an effort to keep the real machines on the air.