SXA portophone is a 6 channel VHF handy available in junk for approximately Rs.300. I bought 2 nos recently. It needs 2 crystals. I have been looking for information on crystals and tuning information of SXA.
Recently Allen Antony, SWL, provided with me all the necessary information.
Tx crystal frequency= f/8
where f is the desired transmission frequency
Rx crystal frequency = (f – 10.7) /3
It seems there are 2 versions of SXA available one with 2 watt and the other with 5 watt power output.
These set were used by Kerala police ( probably some 10 years back). I am yet to trace the manufacturer.
I have scanned and made a jpeg from the sheets Allen has provided. He has also given me detailed handwritten notes on tuning the set for Amateur band. I am yet to try it. I will post details as soon as I do it.
A big thanks to Allen for the help.
The transmitter layout is here and the receiver here
Update: 27 April 2008
The original design of SXA portaphone is by design. There is an article on SXA in the Elektor magazine December 2007 issue. The handies that I have , are manufactured by West Bengal electronics corporation.
My friend Allen (VU3AUZ) has successfully converted the SXA to cover the entire 144-146 band with a DDS VFO.
I have seen service manual of SXA during once of the hamfests. I would love to get hold of a copy.