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David G4EBT · 12th Jan 2018, 1:42 pm

Attached are pictures of the waveform and frequency of the injector. As noted in the fist post, due to variances in some of the resistor and cap actual values, the waveform isn't quite square, but it's unimportant what shape it is. It's 3V peak to peak, so certainly makes its presence known in a working radio from the front end to the speaker. (As well as their fundamental frequency, injectors of this type generate harmonics up to goodness knows what frequency, so are useful for signal injecting in the RF/IF stages as well as AF).

I've attached some pics of the replacement I made for the now obsolete Number 8 3V torch battery. I used a CR132A 3 Volt lithium battery (typically £1.50 - £2.00), which fits snugly in a piece of 20mm OD plastic conduit tube (16.75mm I.D.). The CR132A is 33mm long, and the No 8 battery is approximately 73mm overall (2.875"). I used a piece of dowel as a spacer, with a cheese head 2BA brass bolt through the centre to make up the length. The attached self explanatory pictures illustrate this.

The last pic shows the waveform of the Vellman K7000, which is a sine wave, the spec of which is 'approx' 1kHz, but is actually 1.25kHz, which is of no consequence. As with the 'ESTON' it's approximately 3V peak to peak, but the K7000 amplitude is adjustable.

Hope that's of interest.

12th Jan 2018, 1:42 pm	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,763	Re: 'ESTON' 236 Signal Injector Attached are pictures of the waveform and frequency of the injector. As noted in the fist post, due to variances in some of the resistor and cap actual values, the waveform isn't quite square, but it's unimportant what shape it is. It's 3V peak to peak, so certainly makes its presence known in a working radio from the front end to the speaker. (As well as their fundamental frequency, injectors of this type generate harmonics up to goodness knows what frequency, so are useful for signal injecting in the RF/IF stages as well as AF). I've attached some pics of the replacement I made for the now obsolete Number 8 3V torch battery. I used a CR132A 3 Volt lithium battery (typically £1.50 - £2.00), which fits snugly in a piece of 20mm OD plastic conduit tube (16.75mm I.D.). The CR132A is 33mm long, and the No 8 battery is approximately 73mm overall (2.875"). I used a piece of dowel as a spacer, with a cheese head 2BA brass bolt through the centre to make up the length. The attached self explanatory pictures illustrate this. The last pic shows the waveform of the Vellman K7000, which is a sine wave, the spec of which is 'approx' 1kHz, but is actually 1.25kHz, which is of no consequence. As with the 'ESTON' it's approximately 3V peak to peak, but the K7000 amplitude is adjustable. Hope that's of interest. Attached Thumbnails __________________ David. BVWS Member. G-QRP Club member 1339.