PC based DIY Oscilloscopes, logical analyzers, spectrum analyzers, etc...

[Joel Kolstad]

Say Joerg,

Could you give us a more complete set of specs? I think a lot of people are
kicking around the idea of building something like this as a hobbyist
project...

Stuff like...

Frequency range: 100kHz-1GHz
Dynamic range: 80dB
IF bandwidths (realizing that software can make it arbitrarily narrow so
long as the analog front-end isn't overloaded)
Resolution bandwidth
Maximum power input (i.e., are you planning to use this with an antenna or
at the output of a transmitter!)
Any need for built-in switched attenuators? Or will you just bring a
handful of SMC or BNC in-line fixed attenuators and mount as needed?
Were you expecting it could run off of the 2.5W you can (legally) pull from
a USB port? Or a wall-wart?
Sweep time? (I think you said 1s before...)
Price target? (My own opinion is that ~$500 is the threshold of pain... I
know you might be miffed to find $43 worth of parts in a $500 piece of
equipment, but realistically for the kind of volumes I think a small company
initially could build, $500 seems quite reasonable ...)

I took a look at Tektronix's 8GHz "real-time" spectrum analyzer today...
it's a really nice piece of work, approaching something more like a combined
oscilloscope/spectrum analyzer hybrid that anything else out there. The
group at Tek that designed it picked up a bunch of the Agilent spectrum
analyzer guys who were laid off a couple years ago, and this seems to have
really helped them (since historically Tek SAs didn't seem particularly
competitive to me). The guy in charge of engineering has been doing
microwave RF for a number of years and seems to know his stuff... even has a
little bit (but not too much) of an arrogant air about him (that translates
into, "What? You want me to build a warp core? What do you think I am -- a
kindergardener?"); this probably does him more good than harm

But of course that SA runs into the high 5 digit $$$ and won't even qualify
as carry-on luggage, much less something you can stick in your laptop's
bag...

---Joel

 

[Joerg]

Hello Joel,

Could you give us a more complete set of specs? I think a lot of people are
kicking around the idea of building something like this as a hobbyist
project...

Ok, have to get back to the barbie (steaks tonight) but you basically
got it very close:

Stuff like...

Frequency range: 100kHz-1GHz

150kHz - 1GHz is fine.

Dynamic range: 80dB

As much as possible without breaking the bank.

IF bandwidths (realizing that software can make it arbitrarily narrow so
long as the analog front-end isn't overloaded)

9kHz is typical, more is ok above 100MHz

Resolution bandwidth

This needs to be variable and go down to a few Hz, when you are hunting
wee noises. But it isn't a large cost factor.

Maximum power input (i.e., are you planning to use this with an antenna or
at the output of a transmitter!)

No high power, only hooked up to antennas and near-field probes. Should
have a couple "angst diodes" in case somebody has the audacity to hook a
circuit to it.

Any need for built-in switched attenuators? Or will you just bring a
handful of SMC or BNC in-line fixed attenuators and mount as needed?

No attenuators. Have never needed one in 20 years.

Were you expecting it could run off of the 2.5W you can (legally) pull from
a USB port?

Yes.


Or a wall-wart?


No, unless there is no other way.

Sweep time? (I think you said 1s before...)

A few secs is ok.

Price target? (My own opinion is that ~$500 is the threshold of pain... I
know you might be miffed to find $43 worth of parts in a $500 piece of
equipment, but realistically for the kind of volumes I think a small company
initially could build, $500 seems quite reasonable ...)

You can get a handheld one for $200-300 already. With display,
rechargeable battery, the whol nine yards.

I took a look at Tektronix's 8GHz "real-time" spectrum analyzer today...
it's a really nice piece of work, approaching something more like a combined
oscilloscope/spectrum analyzer hybrid that anything else out there. The
group at Tek that designed it picked up a bunch of the Agilent spectrum
analyzer guys who were laid off a couple years ago, and this seems to have
really helped them (since historically Tek SAs didn't seem particularly
competitive to me). The guy in charge of engineering has been doing
microwave RF for a number of years and seems to know his stuff... even has a
little bit (but not too much) of an arrogant air about him (that translates
into, "What? You want me to build a warp core? What do you think I am -- a
kindergardener?"); this probably does him more good than harm

But of course that SA runs into the high 5 digit $$$ and won't even qualify
as carry-on luggage, much less something you can stick in your laptop's
bag...

That's way too expensive....

 

[Joel Kolstad]

Good specs, Joerg... now we'll see if this goes anywhere!

You can get a handheld one for $200-300 already. With display,
rechargeable battery, the whol nine yards.

Yeah, but I bet it was designed & manufactured in somewhere like China or
Korea!

This thing --> http://www.tti-test.com/products-tti/rf/spectrum-analyzer.htm
<-- from the UK strikes me as a better "yard stick" of what a US company
could realistically sell such a product for and actually stay in business...
note it goes for $1500. Granted what we're discussing deletes the display &
various other spendy items.

---Joel

 

[Joerg]

Hello Joel,

Yeah, but I bet it was designed & manufactured in somewhere like China or
Korea!

Nope, in Germany:
http://www.aaronia.de/

Click on "Digitale HF & NF-Messgeräte", top right. You can switch the
site to English as well. Then download the PDF price list for the RF
spectrum analyzers. Pretty amazing. Now imagine what would happen if
they'd make a "faceless" version. Unfortunately in a discussion on the
German equivalent of s.e.d. they seem not to be intent on doing that. If
not I guess someone else will. Some day.

 

[Joel Kolstad]

Hi Joerg,

Nope, in Germany:
http://www.aaronia.de/

Fair enough; I'll take a close look there.

Still -- from the point of view of, "What is this worth to you?," surely
$500 for a faceless SA box is a decent bargain when you're going to spend
more than that just on a plane ticket & hotel for pretty much anywhere you
take it to, no?

---Joel

 

[Joerg]

Hello Joel,

Fair enough; I'll take a close look there.

Still -- from the point of view of, "What is this worth to you?," surely
$500 for a faceless SA box is a decent bargain when you're going to spend
more than that just on a plane ticket & hotel for pretty much anywhere you
take it to, no?

The client pays for ticket and hotel, not for the analyzer ))

Sure $500 would be ok if performance is on par. But if I can buy an
analyzer that's good enough, has a display and costs $250 then no, it
would be too much. Why would I want to spend $500 in that case? For
business people this is stuff that has to be factored into "overhead".
Got to keep the lid on those costs.

Anyhow, cost is secondary. What I (and certainly lots of others) need is
some little USB pod that can do EMI analysis and tolerates being banged
around on rough flights. Little LCD displays don't always survive that
and when you arrive and the LCD has that big blue or yellow splotch in
the middle the best analyzer behind it isn't going to do any good.

Regards, Joerg