[ARC5] A.R.C. T-25A and T-27A Transmitters

[zakariya.abu at yandex.com]

I got interested in the A.R.C. T-25A and T-27A Transmitters from the 
early 1960s, which seem to be relatively obscure. Both covered ca. 360 
channels in the VHF air band at the 50 kHz spacing. The latter was 
slightly bigger and powerful, while the former had a slim ARINC-alike 
enclosure.

The T-25C version seems to have covered both VOR navigational and VHF 
COM air bands offering dual use in a NAV/COM combo.

Were these transmitters interchangeable? Have both used tubes? How was 
the frequency mixer implemented to achieve the 360-channel coverage, 
particularly in the T-27A?

73,

Jan SP5XZG