Active Probe

[olsenn]

I don't get it.  Why recommend that someone go out and buy a 1152A instead of a 54701a for a SA with an N connector? It's just not very good advice.  The 1152A really only makes sense if you have an infiniium.  I love my lecroy active probes, but I'm not going to recommend them here, either.  Now, if someone gets one free and wants to use it with another system, that's another story. . .

Considering as I've already ordered the 1152A (and paid $150) I was a little scared to read this comment, haha, but after looking up the 54701a, I see that it costs 3x or more than the 1152A, so I guess everything is okay afterall. I will aggree though that it does suck that my soon to arive active probe isn't ready out of the box (doesn't have an N type connector and I need to hack together a power source for it).

To be honest, I don't really know the pros and cons of an active probe vs a Z0 passive probe, all I know is that I recently purchased a $1500 spectrum analyzer with the primary intention of using it to test the frequency responce of filters etc, and it doesn't seem to work well when I just plug it in directly; after looking at the most recent video on "theSignalPath", it shows an active probe being used to do precisely what I want to do.

[free_electron]

I don't get it.  Why recommend that someone go out and buy a 1152A instead of a 54701a for a SA with an N connector? It's just not great advice.

because :
1) the TS ( topicstarter ) has a RIGOL spectrum analyzer with tracking generator that does NOT have the HP probe power interface connector.
2) the 1152a is 1/3 of the price than the 54701a for the same probe ...
BNC to N adapters are 2$ in your local dustbin store.

So , 1152 + homebrew three regulators ( stuff any hobbyist has laying around ) + adapter = still 1/2 of the 54701A.

And if someone makes a nice PCB layout for this power supply it will allow a trove of people to use the 1152A..

The reason the 1152 A is so cheap is because lots are avaialble and there is no demand. Very few people have infiniiums , and there is a newer generation of these probes for the new infinivision machines.

[dfnr2]

The reason the 1152 A is so cheap is because lots are avaialble and there is no demand. Very few people have infiniiums , and there is a newer generation of these probes for the new infinivision machines.

I see your point.  But looking through Ebay, the cheapest working 1152A is $250, while a working 54701a is $350.  Not that much of a savings.  And a proper 50 ohm BNC to N adapter is going to eat up a chunk of that savings.  The $2 BNC to N adapter belongs in the dustbin for a reason.  To start with, it will--almost certainly--damage the N connector on the SA, sometimes after just one cycle. 

[olsenn]

I see your point.  But looking through Ebay, the cheapest working 1152A is $250, while a working 54701a is $350.  Not that much of a savings.  And a proper 50 ohm BNC to N adapter is going to eat up a chunk of that savings.  The $2 BNC to N adapter belongs in the dustbin for a reason.  To start with, it will--almost certainly--damage the N connector on the SA, sometimes after just one cycle. 

The 1152A I purchased cost me $150USD + $20 shipping. I already own a BNC to N adapter, and I can't imagine something like that causing any harm to my device. The only real beef i have with it is that i am going to have to figure out how to power it and properly use it (bias its offset pins etc)

[dfnr2]

There's nothing about a BNC to N adapter that would intrinsically damage your SA.  In fact, it's a very good idea to put some kind of adapter on the SA--even a N-N adapter (which some people call a "connector saver"), and leave it there for good, so any connections you make will be on the adapter.  That way, if/when you manage to damage the threads, you just have to replace the adapter, and not repair the SA.

That said, it's worth the investment to get decent quality adapters.  The difference is that the cheap adapters have imperfect tolerances on the threads, and sometimes rough threads, and can scratch the high quality N adapter on the SA.  If you buy even good adapters on Ebay, you should try to look carefully at the pics for nicks or damaged threads, and look for some kind of return policy.

When going to be using the SA for an extended period, I leave a high quality 10 dB attenuator on the input.  This not only protects the connector, but also protects the input against ESD damage.

[dfnr2]

... I recently purchased a Rigol DSA815-TG spectrum analyzer which is rated for operation between 9KHz and 1.5GHz.

By the way, I was just recently looking at the datasheet on that generator.  It looks like a really nice piece of kit at a fantastic price.  This particular device looks like a perfect machine for precompliance, plus a ton of RF stuff applications.  I think Rigol is gunning to bring the middle market to the masses.  What are your impressions of this device?  It would great if you posted a blurb in the reviews forum.

Dave

[ejeffrey]

Remember, I need this for a spectrum analyzer, not an oscilloscope, and my SA has an input impedance of 50ohms; thus a passive probe won't work.

They make passive probes designed to work with 50 ohm inputs.  They are often called 'low Z' probes or 'transmission line' probes.  In the simplest form they are a 450 ohm SMD resistor soldered to the end of a coaxial cable which makes a 10:1 voltage divider with the source.  You can easily make one yourself that is good to 1GHZ, if you are careful you can do a lot better.

[olsenn]

By the way, I was just recently looking at the datasheet on that generator.  It looks like a really nice piece of kit at a fantastic price.  This particular device looks like a perfect machine for precompliance, plus a ton of RF stuff applications.  I think Rigol is gunning to bring the middle market to the masses.  What are your impressions of this device?  It would great if you posted a blurb in the reviews forum.

You can follow the discussion on this item here: https://www.eevblog.com/forum/product-reviews-photos-and-discussion/spectrum-analyzer-rigol-dsa815/

I promise to do a full review on it after a couple of months of getting used to how everything works. So far I am very pleased with it, and I don't imagine there are any alternatives that come close to the performance specs and functionality of the Rigol DSA815-TG.

[free_electron]

i found the original paten tthat describes the autoprobe !

Patent 5939875

http://www.google.com/patents?id=X4cYAAAAEBAJ&pg=PA6&source=gbs_selected_pages&cad=4#v=onepage&q&f=false
It has the entire lookup table and the full decoded matrix as well as schematics.

[olsenn]

free electron: Dont play around with it. I will hook it up to my scope tonight and measure the voltage on pins 1 and 2 . Then well know for sure.

Did you ever manage to figure out what the voltages need to be for the 1152A? I'm assuming it's +4V, 0V, -12V, and +12V??? Also, do I need to add any resistors between pins or do any weird things (or actually anything other than just applying power) to get the probe to work?

[plesa]

The voltages and other useful information for Autoprobe interface are in the thread
https://www.eevblog.com/forum/projects/agilent-probe-interface-(-autoprobe-and-probe-id)/msg43788/#msg43788

[KJDS]

out of interest, what impedances are the filters that you want to test designed to work with?