Re: [time-nuts] OT favorite signal generator?
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 > Hey everyone > > Sorry for the off topic post. I have received great advice in the past > with items for my little shop and I can't resist to ask again. > > I am thinking about buying a signal generator. I suspect that I will > mostly use it to inject low uV/mV signals into the amplification stages > of the laboratory instruments I service. > > Any feedback you have would be greatly appreciated-Patrick > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
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: > 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 > > > >> Hey everyone >> >> Sorry for the off topic post. I have received great advice in the past >> with items for my little shop and I can't resist to ask again. >> >> I am thinking about buying a signal generator. I suspect that I will >> mostly use it to inject low uV/mV signals into the amplification stages >> of the laboratory instruments I service. >> >> Any feedback you have would be greatly appreciated-Patrick >> >> > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
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. 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 wrote: > Hey everyone > > Sorry for the off topic post. I have received great advice in the past > with items for my little shop and I can't resist to ask again. > > I am thinking about buying a signal generator. I suspect that I will > mostly use it to inject low uV/mV signals into the amplification stages > of the laboratory instruments I service. > > Any feedback you have would be greatly appreciated-Patrick > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
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: 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. 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 wrote: Hey everyone Sorry for the off topic post. I have received great advice in the past with items for my little shop and I can't resist to ask again. I am thinking about buying a signal generator. I suspect that I will mostly use it to inject low uV/mV signals into the amplification stages of the laboratory instruments I service. Any feedback you have would be greatly appreciated-Patrick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
No distortion at low levels will occur with any signal generator worth owning. Nothing from HP will do that. -- john, KE5FX > -Original Message- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on > Behalf Of optoma...@rogers.com > Sent: Friday, June 19, 2009 6:39 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] OT favorite signal generator? > > > 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: > > 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. 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 wrote: > > > > > >> Hey everyone > >> > >> Sorry for the off topic post. I have received great advice in the past > >> with items for my little shop and I can't resist to ask again. > >> > >> I am thinking about buying a signal generator. I suspect that I will > >> mostly use it to inject low uV/mV signals into the amplification stages > >> of the laboratory instruments I service. > >> > >> Any feedback you have would be greatly appreciated-Patrick > >> > >> ___ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > >> > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
How accurate? What frequency range? What spectral performance (harmonics, spurs)? One thing to watch out for on testing with very low level signals is leakage out of the signal generator and into the unit under test via a path other than the coax. When we test deep space transponders at work at very low levels (-160dBm), we actually use a signal generator at a different frequency and multiply it up externally (partly that's also because historically, the signal generator didn't go high enough (7.15 GHz).. But when you use a modern signal gen that does work at 7GHz, you've got to be more careful). .. In any event, it doesn't take much to turn your careful and precise -160 into -159 or -161. On 6/19/09 5:04 AM, "Patrick" wrote: Hey everyone Sorry for the off topic post. I have received great advice in the past with items for my little shop and I can't resist to ask again. I am thinking about buying a signal generator. I suspect that I will mostly use it to inject low uV/mV signals into the amplification stages of the laboratory instruments I service. Any feedback you have would be greatly appreciated-Patrick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
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" 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. 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 wrote: > Hey everyone > > Sorry for the off topic post. I have received great advice in the past > with items for my little shop and I can't resist to ask again. > > I am thinking about buying a signal generator. I suspect that I will > mostly use it to inject low uV/mV signals into the amplification stages > of the laboratory instruments I service. > > Any feedback you have would be greatly appreciated-Patrick > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
On 6/19/09 6:38 AM, "optoma...@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? > 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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Hi James Thanks for your feedback on this. My needs are probably very privative compared to those of the people on this list. I service a lot of the time without a schematic so I spend a lot of time figuring out how the circuit works. I was thinking that if I injected a signal with a known waveform I could follow it around the amplification circuits and such. My only real need is to create something that does not appear to already be there. For instance I don't see many triangle waves, if I produced one I could following it around with my oscilloscope. So in terms of frequency just a few hertz would do, heck even 1 would probably be fine. My only concern is that some of the circuits are high impedance and have low voltages. It might be a good idea if I could get down somewhere into the uV range. Thanks again!-Patrick Lux, James P wrote: On 6/19/09 6:38 AM, "optoma...@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? 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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
I took a look at the phase noise of a 3325B and as Jim said, the phase noise is not great -- about -60 dBc at 1 Hz offset. An external reference cleans up the close in (<10 Hz) signal, but beyond about 10 Hz the synthesizer noice drowns out the reference; from the noise from 10 Hz to about 3 kHz is about -115 dBc, then it drops off to a floor of around -135 dBc at 100 kHz. Some plots are at http://www.febo.com/pages/hp3325b/ That said, they are awfully nice boxes for audio and low HF use. John Lux, James P wrote: 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" 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. 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 wrote: Hey everyone Sorry for the off topic post. I have received great advice in the past with items for my little shop and I can't resist to ask again. I am thinking about buying a signal generator. I suspect that I will mostly use it to inject low uV/mV signals into the amplification stages of the laboratory instruments I service. Any feedback you have would be greatly appreciated-Patrick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Hello Pat, Ebay could be your friend in locating a signal generator, as well as researching availability and pricing. My perspective is that Ebay is the big flea market in the ether and you do not know what you got, till you get it on your test bench and exercise it. Bid accordingly, most dealers are simply junk/scrap dealers who buy the stuff by the pallet load and hope for a quick sale. There are some used equipment dealers that will provide calibration and a guarantee. I have had decent luck selectively bidding on older obsolete HP/Agilent/Fluke/TEK test gear. Many manuals and other documents are available at the HP/Agilent website, a tremendous resource. Consider buying a second of a unit for a parts unit. Get them while you can. The stuff I buy is clearly obsolete and not logistically supported by the manufacturer. I am happy with 80's and 90's vintage commercial test equipment. Stan, W1LECape Cod ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Patrick, If signal tracing in a "mystery" circuit is important, I would look for a generator with external FM input. This feature is common in upscale units. Using a basic audio function generator on the FM input, you can supply 2 tone FM, switching at 1 or 2Hz which is easy to identify in the device you're testing. Pete Rawson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Patrick, Using a large fixed attenuator should work fine. I learned the attenuator trick when dealing with some variable gain amp chips from Analog. Instead of varying the gain, they run at some fixed level that produces a clean output, and vary the attenuation level to prevent non-linear effects and distortion. HP might be doing this, then again, maybe not. Some of my instruments are very sensitive to input overloading and I just got in the habit of using a step attenuator between the signal source and the VNA or spectrum analyzer, or what have you. It helps to prevent stupid mistakes that seem to happen at all the wrong times. As John Miles said, no HP signal generator should produce a distorted output at low level. My Tektronix does! -Bob On Fri, Jun 19, 2009 at 7:38 AM, 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: > >> 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. 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 wrote: >> >> >> >>> Hey everyone >>> >>> Sorry for the off topic post. I have received great advice in the past >>> with items for my little shop and I can't resist to ask again. >>> >>> I am thinking about buying a signal generator. I suspect that I will >>> mostly use it to inject low uV/mV signals into the amplification stages >>> of the laboratory instruments I service. >>> >>> Any feedback you have would be greatly appreciated-Patrick >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Robert Darlington wrote: As John Miles said, no HP signal generator should produce a distorted output at low level. My Tektronix does! It depends on how they lower the signal level. If the signal level is lowered using a traditional attenuator, the distortion will be unchanged, but if the signal level is lowered by biasing a pin diode attenuator, or by changing the bias on a gain stage, it will change the distortion all over the place. Basically, if there is a pot to adjust the signal level, you can expect the distortion to change too. If there is a selector switch like mechanism, the distortion will probably not be affected. -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Hi Patrick: There are a bunch of signal sources that could be used. The rack sized HP signal generators that weigh 50+ pounds were designed to have very low phase noise and although now many years old are still very good for that. The HP 3325() is the only signal generator that has adjustable amplitude that's calibrated to a small fraction of a dB. They still are the specified instrument for amplitude calibration of many other pieces of lab equipment and there is no newer instrument to replace them. They don't have good specs in the frequency domain. The HP 8648() series are reasonably small and light synthesized signal generators. I got the 8648A Option 1EP which is specific for pager testing and includes many modulation enhancements. The prior versions of the 8648 did not have good enough specs to test pagers. http://www.prc68.com/I/HP8648.shtml A problem with injecting a signal into operating equipment is you may burn out the signal generator. For example just touching a DC point feeds a step change back into the sig gen. So it's good to have a series resistor and blocking cap to protect the sig gen. You might be able to use a probe that generates something like narrow pulses at an audio rate as a universal signal source. Have Fun, Brooke Clarke http://www.prc68.com Patrick wrote: Hey everyone Sorry for the off topic post. I have received great advice in the past with items for my little shop and I can't resist to ask again. I am thinking about buying a signal generator. I suspect that I will mostly use it to inject low uV/mV signals into the amplification stages of the laboratory instruments I service. Any feedback you have would be greatly appreciated-Patrick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
Patrick wrote: Thanks John With regard to frequency and price, low frequency is fine for me and I am hoping to buy something for < $250-Patrick The HP 3336 (A,B,C) is similar to the 3325 but somewhat lesser capabilities and can be a bit cheaper. There is one on eBay "in working condition" for $150. Frequency range is 10 Hz to 21 MHz. Frequency is settable to uHz or mHz steps and it has frequency sweep capability. The output attenuator has 0.01dB steps and the output goes down to about -71 dBm. It is sine wave output only. If you want square or triangle, this won't do. If you need to go below about 10 Hz you will need a function generator. My impression from your description is that you do not need the capabilities of a synthesized signal generator. Perhaps an old analog test oscillator such as the HP 654A would be adequate. This is just an analog oscillator combined with a step attenuator that goes down to about -90dBm in 1 dB steps. There is one on eBay for $85 OBO, "tested". Or, for function generator capabilities (square, triangle, lower frequencies) an HP 3310A with an external attenuator. RF attenuators can be somewhat expensive, but audio ones are usually much less. I'll let others comment on whether anything that old might have too many problems. One advantage of the old analog stuff is that they are acoustically quiet (no fan). 73, Gary ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT favorite signal generator?
In a message dated 19/06/2009 15:42:15 GMT Daylight Time, optoma...@rogers.com writes: I was thinking that if I injected a signal with a known waveform I could follow it around the amplification circuits and such. My only real need is to create something that does not appear to already be there. For instance I don't see many triangle waves, if I produced one I could following it around with my oscilloscope. So in terms of frequency just a few hertz would do, heck even 1 would probably be fine. My only concern is that some of the circuits are high impedance and have low voltages. It might be a good idea if I could get down somewhere into the uV range. -- Then forget distortion specs and HP kit, nice as it is, etc etc, all you really need is the cheapest function generator you can find. Most, if not all, will go down to a few Hz and all should give you a triangular waveform. Frequency calibration is often poor, and output level accuracy too, but that shouldn't matter for what you need. Most do have relatively high outputs compared to decent signal generators but a fixed attenuator to bring it into the range you need, easily knocked up with a few resistors, should fix that and you can then adjust using the built in level control. Building something to match your stated requirements wouldn't be difficult either and shouldn't require anything more than a handful of components costing just a few dollars. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
