Here is some prep work I have done on building a sweep generator to display IF response curves.
I did some practical work on getting some valves to work as a frequency generator with easy to get parts.

Being a sort of lab tech experiment only i'll put this essay in tech talk and later on the whole instrument will go into special projects where I normally stick stuff.

Any comments welcome!

Cheers Fred.

Frequency Modulator

File uploaded.

As a BTW:

A wobbulator using 6AC7 and 6SN7 valves was published in the May 1961 issue of Radio Television and Hobbies.

These alternative valves were suggested for that particular design: 6BX6 for the 6AC7 and 12AU7 for the 6SN7.

Later, in December 1963, RT&H published a wobbulator based on a varactor and using 12AT7 and 12AU7 valves.

Both designs rely on a sawtooh signal from the CRO for the timebase.

Thanks GTC I should have known I was re-inventing the wheel!

Its funny I used the same valves but then again the 6SN7 is a common thing and I had a choice of 6SJ7, 6SH7 but I picked the 6AC7 because it was the highest slope. I have a box full of metal RCA valves and just use them up in projects.

I wont look at the RT&H designs yet. I'll keep going back to basics and learn and work out a completed oscillator on my own.
I think you only really learn by getting into trouble and then working your way out.

When it works then I'll take a peek and see how I should have done it!

Thanks again, Fred.

I think you only really learn by getting into trouble and then working your way out.

Absolutely!

I mentioned those mainly as a result of your mulling over alternative valves for the job.

Further back in March 1957, RT&H published an FM sweeper for TV servicing based on a mechanical modulator sourced from a war surplus American radio altimeter.