![]() Most probably, such a power supply is used in HW 101, manufactured by Heathkit. Transformer, made available to me by my good old friend Debu, VUPB and the transformer was designed &constructed by grand OM of Amateur Radio Ganeshda, VU2LL(now silent key). My set-up is based on a circuit for such a However, arrangements can be made for supplying the requisite voltages & current from an alternative source. The transformer shall not be available off the shelf and it has be to ordered with somebody. The power supply uses a single transformer for I supplying the filament supply, plate &screen voltages &also the I bias supply. The Power Supply: The power supply for the PA stage is straight forward &as shown in the diagram. While dealing with vacuum tubes, please remember all safety aspects &go through very carefully the standard literature. It is needless to say that antenna must be switched between Tx & Rx as shown in the circuit diagram. Similarly for the valve stage, only screen supply shall be disconnected during receive mode. However the 12 V supply must be switched. The 25V collector supply need not be switched while going to AM mode. The transistor has to be biased at 20 mA &must be heat-sinked properly. Here is the circuit diagram with values marked: The transistorized linear driver is expected to swing up to 60 to 70 mA with signal (AF) input. The circuit is straight forward &generated from available literature. Prospective constructors should refer to Radio Handbooks & other standard literature for more information & confidence. The least, the valves &associated circuitry must also be shielded appropriately with no possible interaction between the grid & Separate well-shielded cabinets- one for the low voltage (12V& 25 Vdc &the other for the HV supply for the valves. ![]() Premixing technique, the associated circuitry also should be adequately shielded. Both the NR60 board & VFO must be shielded. Must be tested on-the-air with local hams for quality & acceptability. However, before you start please make certain that the basic NR60 board is working absolutely OK without any problem. If you are convinced that those are good enough reasons for a little tactical move backward, may perhaps switch on the soldering iron. Simplicity of construction, switching etc. ![]() Good possibility of taming for multi-band operation without elaborate &dedicated filters for different bandsĥ. Ruggedness-cannot be immediately damaged because ofmismatchģ. However my choice of such an amplifier aheadof NR60 was based on the following considerations:Ģ. Guess lot many hams, now-a-days, are not at all aware ofsomething called vacuum tubes &hence there would be no takersįor such a recipe. Ashutosh, VU21F suggested publication of information on my vintage valve type amplifier for NR60, I was hesitant. VU2ATN - Linear Amplifier Using 807 Valves - QRO When Dr. ![]()
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