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Radio1950 · 8th Oct 2021, 12:25 am

Marconi TF1066B

“Am I right thinking that?”.

If your SG has the “two cal lines” on the attenuator dial, one for EMF and one for Volts in 50 ohms load, then if the output is set for 100mV EMF, this is so called 50mV PD (Potential Difference) in Marconi speak.

This is RMS.

These diode detectors don’t work well for small signals, as the detection efficiency falls off with input amplitude, as well as frequency.

They are useful as relative meters, but dont expect too much at higher freqs.

Only use your CRO at the very lowest freqs in this type of test, and only if the CRO bandwidth with probe, is at least twice the SG operating freq, or you will have to derate the measurement, which is possible but troublesome.

An indicated SG level of 100mV EMF into 50 ohms load will be (50x2.828) 141 mV P-P on a suitable CRO.

Apologies if I am preaching.

Good work with your restoration.

8th Oct 2021, 12:25 am	#15
Radio1950 Hexode Join Date: Apr 2017 Location: Buderim, Queensland, Australia. Posts: 428	Re: Marconi TF1066B/1 Marconi TF1066B “Am I right thinking that?”. If your SG has the “two cal lines” on the attenuator dial, one for EMF and one for Volts in 50 ohms load, then if the output is set for 100mV EMF, this is so called 50mV PD (Potential Difference) in Marconi speak. This is RMS. These diode detectors don’t work well for small signals, as the detection efficiency falls off with input amplitude, as well as frequency. They are useful as relative meters, but dont expect too much at higher freqs. Only use your CRO at the very lowest freqs in this type of test, and only if the CRO bandwidth with probe, is at least twice the SG operating freq, or you will have to derate the measurement, which is possible but troublesome. An indicated SG level of 100mV EMF into 50 ohms load will be (50x2.828) 141 mV P-P on a suitable CRO. Apologies if I am preaching. Good work with your restoration.