The Kenwood TS-820S is the next generation of Kenwood hybrids(solid state/tube) following the TS-520S. It is designed for SSB, CW and FSK modes in the 160 through 10 meter ham bands(excluding WARC) and reception of WWV on 15 MHz. This popular late 1970's era transceiver employed a single conversion heterodyne receiver that was quieter then the dual conversion of that of it's predecessor the TS-520. The TS-820S uses 3 tubes, 38 IC's, 31 FET's, 95 Transistors and 195 Diodes.
Both the receiver and transmitter use a balanced type mixer circuits with dual gate MOSFET's, thus minimizing spurious emissions during transmission and preventing the effects of strong signals and spurious signals during reception. This transceiver employs a conventional VFO, but uses a Phase Locked Loop(PLL) circuit in the local oscillator. The IF is 8.83 MHz. Taking full advantage of the PLL system, this transceiver offers an IF shift function(electronic pass band tuning) and permits one SSB filter to provide the same effect as obtained by using two different filters(LSB and USB).
Some of the main features include a RF attenuation, RIT, selectable AGC, Noise Blanker, Monitor, and IF shift. The transmitter has a VOX, speech processor and variable carrier level(CW only) circuitry.
The final amplifier uses 3 tubes, a 12BY7A as the driver and two 6146B's. This combination produced a power input of 200W PEP on SSB, 160W DC on CW and 100W for FSK. The built-in power supply requirements is 120VAC or 220VAC at 50/60 Hz and the power consumed is 292 watts on transmit and 38 watts on receive with the heater off.
As can be seen in the photograph on the right, this TS-820S has the DS-1A DC to DC converter installed. This item is the large black cage next to the fan. Having this item allows the transceiver to be ran from a 13.8 volt DC power source.
The size of this transceiver is 13.2" wide by 5.9" high by 13.2" deep and weighs in at just over 37.4 pounds. Which makes the TS-820S the heaviest hybrid transceiver that I know of that Kenwood produced for the Amateur Radio market.