Budget?  Freq range?

HP 8657As are good general-purpose SGs.  Reliable, serviceable, and
reasonably clean.  Avoid 8656s and 8660s IMHO unless you can get one for
next to nothing.

If you don't mind getting your hands dirty there have been some inexpensive
8662As on the surplus market lately.  They are cleaner than most, have an
actual tuning knob, and include sweep capability.  They are complex,
sometimes maintenance-intensive, and very hard to ship safely, and many of
the ones you find on eBay have lived hard lives.

-- john, KE5FX

Thanks John

With regard to frequency and price, low frequency is fine for me and I
am hoping to buy something for < $250-Patrick

John Miles wrote:

I just bought an HP 3325A synthesizer/function generator that I really like
(for some things anyway) in about that price range.  What you get is
probably dependent on what YOU need though.  This thing is pretty limited
but this particular one has the high voltage option so the output goes up to
40 volts up to 1MHz.  It only goes to 20.99999999 Mhz (at up to 10V I
think) but for 99% of what I do that's just fine.  It has a 10MHz external
reference which I hook to either an Rb osc or a Thunderbolt depending on
what I'm doing.  It's pretty neat to see all the digits match between the
3325A and the 5335A counter.  Of course, that's being clocked by the same
oscillator too.

Also, I noticed on some signal generators, dropping the output down to a few
mV distorts the signal.  What I learned to do was send my signal out at
about 1 volt ((RMS or p2p, doesn't matter) and go through a step attenuator
to drop it back down so it comes out clean.

-Bob, N3XKB

On Fri, Jun 19, 2009 at 6:04 AM, Patrick optomatic@rogers.com wrote:

Hey Robert

Great tip about the attenuator.

I looked up some models on the internet and some look fairly expensive.
I know that I will always be injecting low voltage signals, do you think
it would be wise to buy a cheaper fixed attenuator, let's say 20dB?, and
then just depend on the variable rate that the signal generator?

Thanks-Patrick

Robert Darlington wrote:

No distortion at low levels will occur with any signal generator worth
owning.  Nothing from HP will do that.

-- john, KE5FX

We use a lot of 3325As in the lab at JPL (they used to have dozens of them at the deep space network, so there are lots of them around).  Some have the rear panel option that puts out a sine wave up to 60MHz, which is fairly convenient.
The settability with lots o' digits is nice (that's why they were used in DSN..).. Really a function generator with sine square triangle, and some modulation capability. You can also lock multiple 3325s together which is nice for generating things like I/Q signals with known errors in phase/amplitude, or with frequencies offset by 0.1 Hz (so it sweeps through all relative phases in 10 seconds), or clock signals with known skew (although something like an 8110 or it's newer brethren is nicer).
They're not super quiet

Depending on your needs, there might be better solutions.  For a bit more money($600), you can get the TAPR Vector Network Analyzer from TenTec, which has a calibrated signal generator mode.  In the few hundred dollar range, I've used a lot of eval boards from one source or another.  Analog Devices has a whole bunch of DDS eval boards that take an external reference (always important for timenuts use) and with a small amount of work, you can calibrate them. National Semi has a whole bunch of PLL eval boards, if you need GHz kinds of frequencies.

On 6/19/09 6:13 AM, "Robert Darlington" rdarlington@gmail.com wrote:

I just bought an HP 3325A synthesizer/function generator that I really like
(for some things anyway) in about that price range.  What you get is
probably dependent on what YOU need though.  This thing is pretty limited
but this particular one has the high voltage option so the output goes up to
40 volts up to 1MHz.  It only goes to 20.99999999 Mhz (at up to 10V I
think) but for 99% of what I do that's just fine.  It has a 10MHz external
reference which I hook to either an Rb osc or a Thunderbolt depending on
what I'm doing.  It's pretty neat to see all the digits match between the
3325A and the 5335A counter.  Of course, that's being clocked by the same
oscillator too.

Also, I noticed on some signal generators, dropping the output down to a few
mV distorts the signal.  What I learned to do was send my signal out at
about 1 volt ((RMS or p2p, doesn't matter) and go through a step attenuator
to drop it back down so it comes out clean.

-Bob, N3XKB

On Fri, Jun 19, 2009 at 6:04 AM, Patrick optomatic@rogers.com wrote:

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On 6/19/09 6:38 AM, "optomatic@rogers.com" optomatic@rogers.com wrote:

How precise does your level have to be? How stable?
There are surplus attenuators available all over the place, some variable
ones too.
MiniCircuits has VAT-nn attenuators which are relatively inexpensive (not by
"found it at a ham-fest 30 years ago" standards, though)

Building your own attenuator using chip resistors is another possibility.