Equipment suppliers

[Qacer]

Hi all,

Do you have any links as to where I can get purchase some equipments?

I already have the following:

http://www.blii.com/
http://elexp.com
http://www.tequipment.net/
http://www.testequipmentdepot.com
...and most of the other sites that pop up on Google.

Also, are there any other things I should look for when purchasing a digital oscilloscope? I'm already aware of bandwidth, sampling rate, memory depth, etc.

Pretty much, I'm interested in measuring FM (89 to 110MHz) signals for a receiver. I think an oscope with the following will suffice: 200MHz bandwidth, 1GSa/s (realtime), 25k memory depth, etc.

Comments?

Thanks!

 

[f95toli]

Cheap digital oscilloscopes are not very good and should be avoided. There are of course some very good digital scopes but they tend to cost a lot of money (probably >$4000 new).
Unless you really need a digital oscilloscope (for e.g. looking at pulses etc) I would suggest a good analog or mixed-mode scope instead, you get better performance at a fraction of the cost.
Some people like Tektronix cheaper models (I think they are called TDA2000) which probably costs $2000, I use models from that series from time to time but I can't say I really like them. Only 8-bit and the displays are not very good.

 

[Qacer]

I actually read at least two Buying an Oscilloscope guide. Both said that analog scopes are getting replaced by digital ones.

Also, I was doing some searching and found the following link: http://www.tequipment.net/TektronixOscilloscopes.html. I find that the GDS-2202 seem to fit my requirements; although, it only has an 8bit vertical resolution.

 

[tex1138]

http://www.testequity.com

This is where I got my Tektronix TDS1002. Nice website because almost all of the prices are posted, so you can window shop to your heart's content

Overall, I've been quite satisfied with this scope. My employer has test equipment that is much better, due to their ability to put another zero behind the amount on the check. Still, this gets the job done for any hobby project I have ever done.

 

[bobsmith1492]

We were looking at a nice 4ch 500MHz Wavetek (or something like that?) scope at work; they're on sale now for like 2800 down from >4000. They advertise an extended memory range so you can sample a long signal then zoom in at high resolution. Might be worth looking into.

EDIT: Sorry, Lecroy Wavejet.

 

[CycloWizard]

For signal generation, the only ones that I've used are Grass Stimulators, which are the benchmark for neurological research (and have been for some time), but I'm not sure how they stack up to other suppliers. My guess is that they're high quality, but expensive.

I've also used the TDA200 series from Tektronix that f95toli suggested. They work for everything I do, but I'm probably not the most discerning electronics guru in the house. Right now, I use it to pick up very noisy neurological signals (maybe 3:1 signal to noise ratio) and use another to test motor control circuits.

 

[JPSJPS]

Originally posted by: QacerPretty much, I'm interested in measuring FM (89 to 110MHz) signals for a receiver. I think an oscope with the following will suffice: 200MHz bandwidth, 1GSa/s (realtime), 25k memory depth, etc.

Comments?

Thanks!

You need to use Google to learn a little about RF and specifically FM receivers.
The test instrument you need is a spectrum analyzer but they cost a bunch of bucks. An oscilloscope is basically useless for "measuring FM (89 to 110MHz) signals". The important FM signal processing takes place after down conversion which is typically at 10.7 MHz and then at baseband. An oscilloscope has very limited uses for these signals as well.

 

[Qacer]

Originally posted by: JPSJPS
You need to use Google to learn a little about RF and specifically FM receivers.
The test instrument you need is a spectrum analyzer but they cost a bunch of bucks. An oscilloscope is basically useless for "measuring FM (89 to 110MHz) signals". The important FM signal processing takes place after down conversion which is typically at 10.7 MHz and then at baseband. An oscilloscope has very limited uses for these signals as well.

Actually, I have used a spectrum analyzer before. With an oscope, I am hoping to see the frequency deviation using a 1kHz test signal at the carrier frequency when I capture and record it. I can then send the data to Matlab to do an FFT. If I had the cash for a spectrum analyzer, then I would go for it. Care to make a donation? ;-)

 

[f95toli]

In theory that might work, but I suspect the accuracy of an ordinary oscilloscope is not nearly good enough for that to work IRL. I would suggest you try to checl if it is even possible, the simplest way to do that would be to generate a waveform in Matlab with the same parameters as the waveform you would get from an oscilloscope (i.e. the same resolution in time and voltage) and then try an FFT.

I am not quite sure what you are trying to do. Why not simply use a mixer and a a LO to down-convert the signal? Then you could even use a relatively cheap 12-bit DAQ to do the measurement, that would give you the waveform and the spectrum in real-time.

 

[JPSJPS]

Originally posted by: QacerActually, I have used a spectrum analyzer before. With an oscope, I am hoping to see the frequency deviation using a 1kHz test signal at the carrier frequency when I capture and record it. I can then send the data to Matlab to do an FFT. If I had the cash for a spectrum analyzer, then I would go for it. Care to make a donation? ;-)

HaHa - My advice of using a spectrum analyzer is probably not what you want if you are trying to play with Matlab to do the spectral analysis.
Before I retired 10 years ago Matlab was powerful program way back then and I used it for FFTs and DFTs of radar signals to analyze the doppler modulation. The job is much easier if you use some form of detection or better synchronous I/Q detection to remove the 100Mhz carrier and then A/D the resultant baseband modulation signals (maybe with a digital scope) and send that to Matlab. But that is not your goal.

Before you blow big money on a 200MHz digital oscilloscope (maybe $1-2K used) maybe you need to re-analyze your requirements. Think about the sample time/number of samples you will require at RF and the dynamic range ("memory depth") required to sort out the modulation from the carrier. But maybe with a very high modulation index you can do what you want.
Good luck!

 

[Qacer]

Well, there are other uses to scope. An FM receiver is just one of them. I also looked at the manual for the scope mentioned above and it can supposedly do FFT. Another use for the scope is to observe the proper operations of a CMOS SPDT switch. My simulation seems to have convergence problems that does not allow me to view the signal past a certain time.

 

[Qacer]

Originally posted by: JPSJPS
HaHa - My advice of using a spectrum analyzer is probably not what you want if you are trying to play with Matlab to do the spectral analysis.
Before I retired 10 years ago Matlab was powerful program way back then and I used it for FFTs and DFTs of radar signals to analyze the doppler modulation. The job is much easier if you use some form of detection or better synchronous I/Q detection to remove the 100Mhz carrier and then A/D the resultant baseband modulation signals (maybe with a digital scope) and send that to Matlab. But that is not your goal.

Before you blow big money on a 200MHz digital oscilloscope (maybe $1-2K used) maybe you need to re-analyze your requirements. Think about the sample time/number of samples you will require at RF and the dynamic range ("memory depth") required to sort out the modulation from the carrier. But maybe with a very high modulation index you can do what you want.
Good luck!

That's actually what I'm doing right now. I'm trying to find out as much as possible regarding the oscope that I'm interested in. So far, with the given real-time sampling rate and memory depth, I don't think I'll be able to see the signal deviation for an FM signal at 100 MHz. However, if I can shift it to a lower frequency and increase the frequency of the baseband signal, then I'll probably be able to see it.

My budget is actually less than $2K, so I need to find a decent oscope and a function generator. If only I could've snag a PS3 and resell it on Ebay, then maybe I can get better equipments.

 

[JPSJPS]

While I was posting f95toli's post about down conversion idea is *very good* because you will have more dynamic range and the ability to sample for longer periods of time but you will probably have to do some custom hardware design. You will still need a lot of dynamic range to handle the carrier and sort out the modulation unless you use a high modulation index so you have a lot of high amplitude Bessel sidebands and a small 100Mhz carrier.

 

[Qacer]

Yep, f95toli's suggestion is very good. But for an initial test I can simply change the carrier frequency to something lower.

 

[Biftheunderstudy]

ebay? I know when I was working over the summer in a research lab using a spectrum analyzer, I looked at some on ebay--they can be had for fairly cheap.

Another good place is dovebid

 

[Molondo]

i have been working with oscillioscopes for a year now, crist i never realised oscillioscopes were so much.