The KW204 Transmitter is designed for Single Sideband Suppressed Carrier
- upper or lower sideband (SSB) operation.
It can also be used with inserted carrier for AM, or on C.W. (Morse
Code). A Tone Oscillator is provided for sidetone generation during C.W.
operation. John purchased the KW204 new from the manufacturers in October
1973. It is still
being used (2004), and has given excellent service.
The Transmitter operates on Top Band (160m), Eighty, Forty, Twenty,
Fifteen and Ten metre bands. When the KW204
Transmitter was designed, the new WARC bands hadn't been allocated.
The power input is 180 watts PEP on SSB (80 - 10metres), 75 watts on
AM and 150 watts on CW.
On Top Band (160m), the output is reduced to 40 watts by open circuiting
the cathode of one 6146 valve in circuit.
On the other bands, full output power is produced by using a pair of
6146B power amplifier valves.
KW Electronics Ltd. produced the KW1000 Linear
Amplifier which could be driven by the KW204 to give a power
output of 400 watts (26dBW). John built his own
Linear Amplifier, but later found that high power wasn't really required.
Below is the circuit diagram for the KW VOX (voice
operated transmit/receive) unit. This was an optional attachment
which John fitted to his KW204. He soon discovered
that the contacts of relay 'RL1a' welded together after a short
period of operation. Having replaced the
relay on several occasions to find the same problem, he modified the circuit
of the KW204 Transmitter, by wiring a diode in
reverse bias across both Relay coils RL1 and RL3. This modification
was appreciated by KW and they gave John a KW
Balun for his efforts. This is currently used on his Inverted 'V' Tri-
band Trapped Dipole Antenna. Pins
7 and 8 of the VOX unit switch the relays in the KW204 which are highly
inductive.
|
