Current (and final) Shortwave Transmitter

This is truly a 'Rig-in-the-Box'! Because I only use it during holidays the rig itself is placed in a well rugged cabinet for field operations.

The VU meter (left) is available on the chassis that shows the peak modulation. (0VU = 100% modulation) On the right metering is provided for Grid current and Kathode current on the 807s, I really do like the ex-Marconi front panel meter, very 1960's I thought!

Inside the valve rig; 12BY7 Crystal Oscillator, 2 x 807 Power Amplifier, PL84 clamp tube to protect the 807s in case of drive failure. Crystal on the right is the standard HC-6/U type.

Seen from the bottom.....

Seen from above......

Tank circuit and 2 x 807 Power Amplifier, HT Power Supply is 525 volt / 300 mA.

35 Watts minimum if desired... maximum 50 Watt carrier and with Anode and Screen AM PEP will be well over 75 Watts.

Part of the audio section; the Internal MOSFET (BUZ900/905) 100W RMS into 4 Ohms solid-state Maplin modulator/amplifier. Audio driven by a Band Pass filter; bass cut at 6dB per octave below 200Hz and then flat till 2kHz then rising at 6dB per octave to 5.5kHz then cuts to -40dB by 9 kHz. Of course High Level Anode and Screen Amplitude Modulation with 100% positive and negative peaks available.