Marconi wattmeter. What's this feature here??

[Chris Wilson]

I bought a used Marconi TF2503 Wattmeter a while ago, and have been using it fine for some time. it has a feature that I am not familiar with though, and I would like to know what it is, an what it's for. The bes way to see it is via a photo. I am talking of the secondary meter that's marked "diode detection", and the "insert probe" knob. There's also a jack socket marked "MOD OUT". Can anyone explain what these are for and if they might be something I should be using? Thanks

[jimmc]

If you are measuring the power of an amplitude modulated signal then you can use the diode detector to look at the modulation.
No a great deal of use but handy to check if what you think is a CW signal has any unwanted AM on it or if you want to look at the rise and fall times as the RF is keyed

The probe part is effectively how tightly the diode is coupled to the signal.
I'm not sure but I would suggest, set it for 100% on the meter to measure modulation.
Set to zero when not using the diode to avoid overload and diverting power from the main wattmeter.

Jim

[Chris Wilson]

Is it a bit like a built in circuit similar to part of the one w2aew shows here:   which I am about to build? If so I'll try scoping the output at the "mod out" jack and see what's to be seen! Cheers, thanks for the reply.