The amazing National SW-3 – selective, sensitive and with a great signal to noise ratio for a “three tube job” . . .
The first “mystery” was which power supply to use – there are three versions of this receiver and each has a different voltage configuration. I purchased what was supposed to work (the “Doghouse”) – and while I got the tubes and dial light to light up – I couldn’t hear a thing.
The National 5886 “Doghouse” power supply . . .
Turns out – the Doghouse supply was the right supply. It was operator error.
Radio Shack “Minimus” Bookshelf Speaker . . . its black “wrinkle” finish looks quite good with the SW-3
“Field Coil” so I could use the Minimus speaker with the SW-3 . . .
The biggest mystery was the audio circuit in the SW-3. Besides getting a shock (there’s pretty high voltage on the audio output terminals!), you cannot just plug a pair of high impedance headphones in the output terminals. You MUST use a “field coil” – or you will hear nothing and – like me – assume there is something wrong with the power supply. I added a field coil to the Minimus speaker – and the receiver came to life!
The other thing about this receiver – its dead quiet until you get it to oscillate. Then you back off on the oscillation – and the signals come in so loud and clear. The most bizarre thing about this receiver is how you hear nothing or a signal. Its not like modern receivers – you have noise and tune for a signal. I almost gave up on the receiver – but stuck it out and solved the mysteries. And I am sure glad I did:
That swoopy shrieky regenerative receiver sound is hard to beat, and is classic.