Checking Signal Generator Accuracy With A Frequency Counter and Scope

[jr_tech]

I may have stated the question poorly... I was not asking for a definition of period, but rather for the number that you measure. If the waveform on the 'scope does not change when you change the frequency of thr SG-8, what is the period of the unchanging waveform (in seconds or milliseconds or microseconds) of the waveform that you observe?

jr

[Notimetolooz]

Just to set the record straight, I wasn't taught tube circuits in school it was pretty much solid state stuff. Field Effect Transistor circuits are somewhat similar to tube circuits. I looked at information on several other RF generators like EICO 324 and Heathkit IG-42 and IG-102.
I took some pictures of the output of my modified generator.
The first shows the modulated RF output as well as the 400Hz signal.
The second shows output at about 500KHz on the lowest range, some distortion.
The maximum output amplitude varies from about 1Vpp at the top of the lowest range A, to about 40 mVpp at the top of range D (25 MHz). Range E never worked and couldn't find a fix.

[jr_tech]

Wow! that looks pretty decent... might have to do some work on mine, although the output waveform gets better in the higher ranges.

thanks,
jr

[Notimetolooz]

The lowest range does have the worst wave shape. The oscillator section has almost 100V peak-to-peak on the plate at some settings. I think the distortion is mostly due to the large signal there hitting the limits of the tube operating range with the supply voltage. I am puzzled why they chose a audio tube (12AU7) rather than something that works better at high frequencies (12AT7,12AV7).

[Tubejunke]

Originally Posted by jr_tech

If the waveform on the 'scope does not change when you change the frequency of thr SG-8, what is the period of the unchanging waveform (in seconds or milliseconds or microseconds) of the waveform that you observe?

jr

I did a lot of things based on all the great information given here. I am fairly satisfied with my results. The first good result was found when I isolated my frequency counter from line voltage with the modulation of the generator off. I was able to obtain a steady frequency. Oddly, (self hi five; lol) my UN-calculated guess of the generators output based on 455Khz ACTUALLY being 460 or so on the dial was spot on.

Also, I hadn't used my scope for obtaining specific information like frequency in so long I first had to realize the whole 1/time formula 10ms. For simplicity the UN-triggered waveform I obtain a sine wave in which a cycle takes 5 divisions of the graticule. So I can calculate for the reciprocal 1/.010 x 5 and I get 500 or 500Hz. Honestly, I was again making my own problems by forgetting the proper use of the reciprocal function of my TI36X calculator. I was multiplying .010 x 5 and then using 1/X. Duh! This has been a great thread for me and I hope helps someone in the future. Thanks to all!!!

These are things that I would only do at home working on communication devices. We never use bench equipment on the job keeping automation equipment going. When I quits, we try to locate it on the planet (Siemens) and then replace and test. It either works or it doesn't. Pretty basic. But they require some sort of undergraduate degree to do it.