[TowerTalk] Telrex rotator

[Shawn Donley]

Synchros have been around for years.  Those that run on 400 Hz were typically found in aircraft systems whereas the 60Hz variety were found shipboard in gun fire control and radar systems.


The link below has probably more info than you need.


http://www.moog.com/literature/MCG/synchrohbook.pdf


If you don't what to jump to a modern solution, one possibility is to find an old surplus I-82-A Radio Compass Indicator.  They can often be found on eBay.  The dial on the indicator (I believe) uses a 115vac 400Hz synchro that's inside the unit.  Pin out can be found at http://aafradio.org/docs/docs.html (look for the schematic for the AN/ARN-7 schematic and find the I-82-A indicator on the schematic).  Another nice feature is that the little knob on the corner rotates the compass readout so you can adjust any error in the setup without going up the tower.


As Jim mentioned, you can run 400 Hz synchros at 60 Hz if you reduce the voltage.  Half the frequency, half the voltage.  See paragraph 3.1 in the Moog link above.


I'm not sure what the 57.5 - 57.5 marking means on your rotator synchro.  Never heard of a 57.5 vac synchro.    I think it's just a 115 vac unit (2*57.5 = 115).   I'd try using the output of a 12v or 6.3 volt transformer if you're running on 50Hz or 60 Hz.


I've successfully used the larger 60Hz synchros to remotely adjust an L-network antenna tuner capacitor.  A pair of gears between the synchro and the capacitor for mechanical advantage and a turns-counting knob on the synchro at the operation position.  The 60 Hz unit generates enough torque to turn the capacitor.  "Motor" and readout all in one.


Shawn

N3AE