Dear Bob,
We cannot hear any sound from the transmitter set that can be connected to the keying. The transmitter set is equipped with two Bartlett Hayward flexible couplings between drive motor/gearbox and gearbox/high frequency generator. According to the RCA description of the transmitter, a special lubricant is needed to these couplings ”to absorb the chock in telegraph service”.

However, the keying is easily heard in the transmitter hall, as four huge relay-switches are operating for the speed compensation. Moreover, these relay-switches are cooled with compressed air in order to blow out arcs and cool the contact surfaces. The sound from the cooling air is very aggressive and varies with the keying, so use of ear protections is recommended.

Ola Hernvall / AlexanderSAQ