Note
QST, Aug 1963, p. 128.
QST, Jun 1965, p. 175.
QST, Dec 1965, p. 157.
QST, Sep 1966, p. 168. (could be NOS)
The LA-500-M “Spitfire”linear amplifier from P&H Electronics used six parallel 12JB6 tubes (television horizontal sweep tubes) in grounded grid. Power input was 1000 watts PEP. It was advertised for mobile operation and had an optional DC supply, but a 115 VAC home-station supply was also available. Requires PS-1000 AC power supply, or PC-1000B DC power supply.
The SPITFIRE uses six inexpensive type 12JB6 tubes in hi-mu triode connected grounded grid circuitry. A pad across the input circuit presents a more constant load impedance to the exciter. The pi network features pre-set antenna loading for each band, 80 thru 10 meters, permitting simplified tune-up of the amplifier.
VOX switching functions are built-in to connect the exciter to the amplifier input and the amplifier output to the antenna when transmitting and to connect the antenna back to the exciter or transceiver when receiving.
An 1/8 inch thick aluminum support plate for the tubes serves as a heat sink, keeping the tube base seal temperatures low. The unusual type construction of the Spitfire permits convection cooling of all components without the need for a cooling fan.
Amplifier bias is provided by a zener diode in the DC cathode path.
– Input and output Impedance: 50 Ohms.
– Frequency coverage: 80, 75, 40, 20, 15, 10 Meters.
– Plate power input: 1000 Watts PEP SSB.
– Drive power not stated ("easily driven with present day exciters")
Power Requirements:
Filaments: 13 VDC or 12.6 VAC
Plate: 900-1200 VDC at 1 amp peak (500 mA average)
