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Thanks for the info Patrick. So what about a signal generator?

On Dec 6, 2014, at 22:54, patwong3@... [TekScopes] <TekScopes@...> wrote:

HP 3325A is a good synthesized function generator, with highly stable frequency. Sine wave production to 20 MHz; square wave production to 10 MHz. Triangle and tooth waveforms to 10 kHz.

Tek FG 504 operates up to 40 MHz but the frequency is not synthesized like the HP 3325A hence is not as stable. The sine, square and triangle waveforms in principle are all produced up to 40 MHz but in practice the waveforms don't look great at higher frequencies.


Remember that a function generator is not a substitute for a signal generator with respect to the following attributes:


- a signal generator typically offers AM, FM, PM, and maybe pulse modulation choices at minimum
- a quality signal generator will produce high quality modulated signals. When you look at the AM waveform with a spectrum analyzer you will see both sidebands have the same amplitude and the carrier does not decrease in amplitude relative to an unmodulated carrier. A lesser signal generator will show one sideband stronger than the other which indicates incidental FM on the waveform and/or may show carrier amplitude reduction at higher modulation percentages
- a quality signal generator has a calibrated attenuator down to - 130 dBm or better which you need when working on receiver front-ends. If you are using a function generator, the minimum output typically is 1 mV so you would need an external attenuator to bring down the signal level.


Good luck with your choice. You may end up with multiple signal and function generators as you gain experience with their use.


Patrick Wong AK6C
---In TekScopes@..., <kcrossett@...> wrote :

So does anyone have a good recommendation for a used function generator? I have been searching for a signal generator and have been saving my pennies for one, but I think a function generator may prove more beneficial since, as I understand it, a function generator has more waveform options.






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I'll tell you the units that I currently own, I would recommend any of these models depending upon your intended use:

HP 8642B, 100 kHz to 2.1 GHz, extremely high quality signals produced. Perfect with regards to frequency display resolution, amplitude control, and modulation signal quality, excellent frequency sweep capability


HP 8665A, 100 kHz to 4.2 GHz, same as above except the frequency sweep is not continuous, it consists of the frequency hopping from one frequency to the next in a bunch of steps moving from the low to high frequency in the sweep. You can set up a continuous sweep only within a fairly limited frequency range. This may not be good depending upon what you are doing with your device under test. This is a newer model.


HP 3335A, 200 Hz to 80 MHz, precise frequency and amplitude control, specified for use in aligning some HP spectrum analyzers at lower frequencies. There is no modulation capability and the attenuator range does not go down to the same low levels as typical HP signal generators. But this is not a function generator because it does not produce signals other than sine waves. So consider this to be a very specialized signal source.


HP 8782B, 1 - 250 MHz, vector signal generator, interesting to play with various digital signals such as various QAM and PSK modulation choices. This is fun if you have a spectrum analyzer that can display I/Q constellation displays.

Back to function generators for a moment. If you can get your hands on an arbitrary waveform generator, you might find that to be fun. The idea is that in theory, you can produce any weird (i.e., arbitrary) signal that you can imagine. I have a LeCroy LW410A which among its features, can produce signals based upon a mathematical equation that you enter. It has a CRT display so that you can see the waveform that the unit plans to produce.


Have fun,


Patrick Wong AK6C

---In TekScopes@..., <kcrossett@...> wrote :

Thanks for the info Patrick. So what about a signal generator?

Thanks Patrick. I'll take a look at them.

On Dec 6, 2014, at 23:18, patwong3@... [TekScopes] <TekScopes@...> wrote:

I'll tell you the units that I currently own, I would recommend any of these models depending upon your intended use:

HP 8642B, 100 kHz to 2.1 GHz, extremely high quality signals produced. Perfect with regards to frequency display resolution, amplitude control, and modulation signal quality, excellent frequency sweep capability


HP 8665A, 100 kHz to 4.2 GHz, same as above except the frequency sweep is not continuous, it consists of the frequency hopping from one frequency to the next in a bunch of steps moving from the low to high frequency in the sweep. You can set up a continuous sweep only within a fairly limited frequency range. This may not be good depending upon what you are doing with your device under test. This is a newer model.


HP 3335A, 200 Hz to 80 MHz, precise frequency and amplitude control, specified for use in aligning some HP spectrum analyzers at lower frequencies. There is no modulation capability and the attenuator range does not go down to the same low levels as typical HP signal generators. But this is not a function generator because it does not produce signals other than sine waves. So consider this to be a very specialized signal source.


HP 8782B, 1 - 250 MHz, vector signal generator, interesting to play with various digital signals such as various QAM and PSK modulation choices. This is fun if you have a spectrum analyzer that can display I/Q constellation displays.

Back to function generators for a moment. If you can get your hands on an arbitrary waveform generator, you might find that to be fun. The idea is that in theory, you can produce any weird (i.e., arbitrary) signal that you can imagine. I have a LeCroy LW410A which among its features, can produce signals based upon a mathematical equation that you enter. It has a CRT display so that you can see the waveform that the unit plans to produce.


Have fun,


Patrick Wong AK6C

---In TekScopes@..., <kcrossett@...> wrote :

Thanks for the info Patrick. So what about a signal generator?







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