My typical IMD workflow.

Test configuration

Two tone test source feeding stepped attenuator, feeding DUT, feeding fixed value power attenuator, feeding switched notch filter, feeding SA.

Set stepped attenuator to give output of DUT at approx 10 to 20dB below saturated output level

Measure output level with SA via fixed attenuator, with notch filter off.

Setup SA to track test tone peak levels, and add level offset for value of external fixed power attenuator.

Switch in notch filter and note level reduction of test tones, compensate for notch attenuation as additional offset in calculations and displayed values.

As the SA should track the test tones in frequency and level, any drift in test sources should be continuously compensated for.

The test tone frequencies and compensated levels can then be used to accurately and automatically set and track the IMD component measurement markers in a narrow bandwidth, in order to maximise the dynamic range.

The IMD traces will be at a lower level than the test tone level, even though these are notched for measurement purposes, so the SA noise floor with the DUT running may have to be used to determine the optimum reference level for these measurements.

The marker information can then be used to directly calculate the IP2 & IP3 values and display them.

As a confidence check an extra 3dB can be switched in to the SA input and the calculated values should not vary by more than approx +/-1dB from the previous measurement without the extra 3dB.

The stepped attenuator on the DUT input can also be varied to determine the effect on IMD values at different power levels up to the DUT saturation point.

I hope this makes sense.

Regards,

Martin

Trying to install TinySASaver on my Mac/OSX. Python 3.11. When I run the app, I get the following error. Is there an easy way to fix it?

?? tinysa-saver git:(master) TinySASaver

I forgot to add.

The ability to switch in an attenuator quickly as part of the test, to check for any SA contribution (hopefully none) would ?be very useful and save a lot of menu hopping.

Hi Erik,

Yes I think X+Y and either 2X+Y or X+2Y would be ideal.

Maybe allow selection of one or the other of the latter pair, or separate out IP 2 & IP3 measurements ?

Personally I like to see both IP2 & IP3 (either pair) at the same time, as I often use these whist adjusting amplifier bias current in order to find the best compromise between the two.

Regards,

Martin

WiKi updated

Thank you so much Eric for updating that quickly !
Jos

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That makes sense, of course. ;-)

On Tue, Feb 28, 2023 at 06:12 PM, Terry Perdue wrote:

* LOCK DISPLAY: Once locked, there's no way to unlock. Then the only way to access the LOCK DISPLAY menu again is to press the jog wheel, but the menu items don't respond.

You have to activate the unlock menu with the jog switch: down, right, right, down
This to prevent accidental unlock

Thanks for the other bug
?
--

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Yeah, that's the same cell that Batteryhookup.com is selling for $0.99 each (like I said, the shipping is the killer, you can order more to stay within the shipping limits and you'd still be CHEAPER than that one on ebayism.)

Mike C.

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The yellow wire can just be clipped,i.e. not used. 2nd thing is unsolder the the existing wires and use the plug from the 3000mahr cell and use it on the 4500mahr cell, simple, yes.

Mike C.

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Nope, here's the link:? Look carefully at the picture, it's there. They did give the dimensions but in English units.

Mike C. Sand Mtn GA

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I like the way this works, but I have some observations...

* LOCK DISPLAY: Once locked, there's no way to unlock. Then the only way to access the LOCK DISPLAY menu again is to press the jog wheel, but the menu items don't respond.

* Recalling a MULTI BAND file from the memory card doesn't start the MULTI BAND function. It has to be switched off and back on first.

* The BIG NUMBER and WATERFALL do work when MULTI BAND is on, as long as MULTI TRACE is off.

This has a three wire connector.

Larry

I haven't done the math on the dissipation of each resistor in the qrpkits attenuators, but I think John Gord is probably correct that they won't do 5 watts continuously, unless you pick which end is driven and which stages are engaged.? Note that a lot of the high power attenuators (even fixed attenuators) like the ones I suggested above and included a link to on ebay, and the much more expensive ones that the cheaper ebay attenuators look like are the same: one end will take high power, and one end absolutely will not.? One of the high power attenuators I bought on ebay was labeled as to which end was the high power end.? I assumed the other one was the same, and so far I haven't burned it up.? For critical applications, I would avoid the pushbutton attenuators like those Evan linked to.?? Note that the 30 dB attenuator can have as much as 3.5 dB insertion loss besides the selected attenuation, and I went to the website for the BECEN 60 dB attenuator, it can have as much as 3 dB insertion loss.? I would also be concerned with the life of the pushbutton switches.? Pushbutton and toggle switch attenuators certainly are convenient, though.? The MiniCircuits stuff Dave recommended is indeed more expensive than the stuff you buy on ebay, but it's top notch and less expensive than the other "high end" brands.? I recently needed a coaxial DC block to protect a spectrum analyzer that will tolerate zero DC at the input and the MiniCircuits unit I bought, while sold as an 18 GHz model, has been swept to 26.5 GHz, and it's fine all the way up and again, cheaper than the other "high end" brands.? I will absolutely agree with Evan's recommendation for fully shielded attenuators, in fact, just in general RF equipment should be well shielded.? I recently was called upon to find a transmitter with a stuck mic, and several hams that came to observe noted that the signal was full scale on their radios even with the antenna disconnected, and this problem is often seen during hidden transmitter "bunny hunts."? It doesn't matter how directional your antenna is or how much attenuation you have inline if the signal can leak directly into your radio, or past your attenuators.

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Just a heads up, but if you need a battery for your ULTRA. Batteryhookup.com (no, I'm not affiliated) has a 4.5Ahr cell for $0.99 ea. Size is 755275 and yes it fits like a glove. That'll give you 50% more power than the 3Ahr presently installed. Buying the cell singularly will cost the same as 20, so buy many. That's about the min to stay within the shipping minimum w/UPS. Yes, they are new cells. I've bought many with no problems. It'll work out to $1.61/cell (shipping included)

Mike C. Sand Mtn GA

Okay after PAUSE SWEEP, you can cycle through the MULTI TRACES? after repeatingly hitting SINGLE SWEEP

I hope you read through and checked that wiki page update for correctness! I am not an expert.
--

Steve Johnson

? ? ? K0OIL