Test Equipment: Oscillocopes

[MarkE]

So what DDS chip would you recommend?  I've read a good bit that more or less said that the best ones to go with are the AD series, particularly AD9914.  Also the 5932, 9833, and 9959...  oh, and also the XR2206. What are your thoughts, MarkE?

I f I were going to build something I like the AD9857 because it is 14 bits.  But there is lots of stuff that you can buy that is cheaper than the one chip alone.  $20. gets you something like Pirate Bill found and $60. gets you something that is packaged in a half way decent case that does 5MHz.

[Brian516]

That said, I'd recommend saving up for a good used FG or buying one of the 2MHz units on Ebay for $60 or so.

PW,
That goes right along with what I was just thinking about asking - If, being at the stage I am at, it would be reasonable to buy a DDS chip and build a FG, and if I would be able to obtain comparable features and same or better signal quality.   Sometimes when I think of something, I immediately dive in the deep end as far as ideas/plans go, and then as a few hours or so goes by, I think a little more into whether I'm being reasonable or not. Most of the time, it's not.

You can use the powerful audio editing applications Audacity (linux) or GoldWave (windows) to generate all kinds of audio frequency waveforms to look at, output from your computer's sound card, one or two channels as you like.
Audacity is freeware and so are versions of GoldWave.

And don't forget about the venerable GenRad 1330-A, which covers the RF range from 5 kHz to 50 MHz with a sine wave output that can also be partially modulated by the fixed audio frequencies from the unit's audio oscillator section ( at the higher frequency ranges of the RF signal).

If I had a hundred dollars to spend I'd buy this right now:

http://www.ebay.com/itm/Interstate-IFC-F-74-F74-20Mhz-Sweep-Function-Generator-/301529989757

I'll have to go to storage and dig out my old Dell dimension 8250 and get it up and running with Linux, and download some software on it.  I don't feel like buying any cheap-o USB sound cards, and I have 4 or 5 good 5.1 sound cards in storage I can use.  I did read up on sound card based FG's a little bit, and got the jist that I will most definitely be needing to build a limiter unit so I don't fry them up crispy. I don't know if that PC will support installing more than one sound card, but it would be pretty nifty if I could install two, run a PC scope on one, and FG on the other, or have several FG/scope channels.     I know I already have a real scope and everything, but there should be some math/charting features along with other digital scope features on the PC based scope.   But instead of using a cheap 3.5mm home-made probe for it, maybe I can build a little BNC interface box - or if I can get that dongle, maybe I can make something with that.  or even the arduino.  I'm probably getting a little bit ahead of myself here though.  Just some ideas. 
I'll just start with the sound card FG, though.
Hopefully some of my stuff on ebay sells soon, and then maybe I can scoop up that FG you linked to before it's gone...

I recommend this PC based O'scope and sig gen combo software for the beginner.
Many features including sweeps of audio, spectrum, etc
http://www.zeitnitz.eu/scope_en
There are other good ones out there, I just happen to like this one.
Do build a limiter protection box for your soundcard.

Vortex -
That definitely seems like a good one to start with once I get my desktop out of storage.  I'm running out of room to put all of this stuff!  Going to have to do some re-organizing and add some more shelves to my ikea wall unit...


Brian

[picowatt]

Brian,

Why would you need a dedicated computer or two sound cards to start using a software based FG and your scope?

What are you posting on this forum with?

PW

[Brian516]

Brian,

Why would you need a dedicated computer or two sound cards to start using a software based FG and your scope?

What are you posting on this forum with?

PW

My laptop, and as far as sound card goes, all it has is a combo jack. Now that you've asked...
What is the real difference between using FG software out the headphone jack to a modified cable and a FG off of a dedicated sound card?
Is it really only the PC based scope that needs a dedicated sound card??  I'm confused.  going to have to do a search and read a few articles again..
I have FG software. There is an FG built into Visual Analyzer, and "Function Generator" by Cognaxon. From what I remember, the only issue with using PC based FG's is the amplification. Is this correct? (That is, amplification for using the FG for more than just running it to the scope, I'm sure using it without amplification is fine for only that aspect. Maybe this is where I am confusing people.....)
I may have confused some of you when speaking of this, because I was referring to having a PC based FG and possibly scope w/ extras for future projects as well.   Sorry.... I need to just stick to talking about specifically using it for learning functions on the scope.   My fault...

Brian

[Brian516]

Ok, so what I have done here is this:
I have a standard 3.5mm stereo audio cable ran to a jack that I pulled off a board.  I figured out what was left, right, and ground, and soldered red, white, black to it.  I'm about to connect another jack into the setup so I can listen in to the signal.
Do I need to be on AC or DC? This is what I am unsure of as far as when I connect to something... what qualifies for an AC signal and what qualifies as DC? and what do I use ground for? Is that ground setting also to be referred to as "reference"? meaning that, on that setting, I would be seeing what my AC or DC signal would be in reference to?

Also, I would only need a limiter protection box if I were running my signal to an amp and/or using it for anything other than putting the signal to the scope, right?

Brian