|
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
DO NOT dump your 1-watt HT directly into the TInySA or any of the NANOVNAs!! ? 1-watt is +30 dBm.? The designer strongly recommends a maximum input of -26 dBm for a faithful measurement/rendition of the input signal.? That would require a total of 30 + 25 dB of attenuation, 55 dB of total attenuation.? For safety, I would not assume the internal attenuator could handle a full+30 dBm, or 1-watt.
Dave - W?LEV?
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
You will need a bit more attenuation than that. And still more if you want the most accurate measurements possible.
The math is simplest if you do the calculations in dBm (dB referenced to 1 milliwatt). 1mW = 0 dBm. 1W =?+30 dBm. 10W =?+40 dBm. For HTs and QRP rigs, perhaps the most important number is that 5W =?+37 dBm.
The maximum permissible input to the tinySA Ultra is?+6 dBm (4 mW). If you are applying a?+37 dBm signal, you need 31 dB of attenuation to decrease that to?+6 dBm, more than the 25 dB external attenuator that you proposed, and a tad more than the 30 dB attenuators that are popular surplus items. And you want a bit more in case your HT produces more than 5W; I'd recommend starting with at least 34 dB, which would make you safe for up to 10W.
The internal attenuator in the tinySA Ultra is an active device, and as such it causes some distortion. That will make the device under test (DUT) look a bit worse than it actually is. For best measurement accuracy, you want the internal attenuator to be inactive, which means you need an additional 30 dB of attenuation to get down to the range where it's not used. That theoretically comes at -24 dBm, but the auto mode of the tinySA is a bit more conservative about using the attenuator; you'll get down close to -30 dBm before it turns off.
For my measurements, I use a 30 dB fixed attenuator with a 20W rating, plus a step attenuator. For testing higher power radios I also have a 20 dB fixed attenuator with a rating of 150W that I can add to the chain. It's often difficult to find the rating of surplus step attenuators; it's safest to treat them as having a maximum input rating of?+17 dBm (50 mW). Some fixed attenuators specify an input end and an output end; make sure to heed those, or else you can burn out your attenuator. If you buy a used attenuator, you should test it for accuracy, which you can do with the tinySA itself using its signal generator as the source signal (procedure at ) or with another instrument such as a NanoVNA. The NanoVNA is nice because it can easily produce a display of attenuation over a range of frequencies.
For testing an HT, I would start with the 30 dB fixed attenuator plus a setting of 40 dB on the step attenuator. That would reduce the expected +37 dBm input signal from the HT to -33 dBm. Then I would reduce the amount of attenuation in steps until the internal attenuator turns on, then back off from that until it turns off again. That procedure gets maximum dynamic range and minimum distortion from the tinySA. The actual output of "5W" handhelds varies a bit, but I'd typically end up with about 35 dB on the step attenuator. Once you have dialed in the needed amount attenuation, you can set that in the tinySA so that it will directly display the actual signal levels.
ALWAYS start with at least as much attenuation as you need, adding a bit more for safety if possible. You can then reduce it to the optimum point. If you start with an inadequate amount you can destroy the front end of the tinySA, and you don't want that.
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
Oops, sorry, you said a 1W input. 25 dB of attenuation would be just adequate for that. But most HTs produce more than 1W except on their lowest output setting.
On Mon, Jan 20, 2025 at 1:45?PM Shirley Dulcey KE1L via <mark= [email protected]> wrote: You will need a bit more attenuation than that. And still more if you want the most accurate measurements possible.
The math is simplest if you do the calculations in dBm (dB referenced to 1 milliwatt). 1mW = 0 dBm. 1W =?+30 dBm. 10W =?+40 dBm. For HTs and QRP rigs, perhaps the most important number is that 5W =?+37 dBm.
The maximum permissible input to the tinySA Ultra is?+6 dBm (4 mW). If you are applying a?+37 dBm signal, you need 31 dB of attenuation to decrease that to?+6 dBm, more than the 25 dB external attenuator that you proposed, and a tad more than the 30 dB attenuators that are popular surplus items. And you want a bit more in case your HT produces more than 5W; I'd recommend starting with at least 34 dB, which would make you safe for up to 10W.
The internal attenuator in the tinySA Ultra is an active device, and as such it causes some distortion. That will make the device under test (DUT) look a bit worse than it actually is. For best measurement accuracy, you want the internal attenuator to be inactive, which means you need an additional 30 dB of attenuation to get down to the range where it's not used. That theoretically comes at -24 dBm, but the auto mode of the tinySA is a bit more conservative about using the attenuator; you'll get down close to -30 dBm before it turns off.
For my measurements, I use a 30 dB fixed attenuator with a 20W rating, plus a step attenuator. For testing higher power radios I also have a 20 dB fixed attenuator with a rating of 150W that I can add to the chain. It's often difficult to find the rating of surplus step attenuators; it's safest to treat them as having a maximum input rating of?+17 dBm (50 mW). Some fixed attenuators specify an input end and an output end; make sure to heed those, or else you can burn out your attenuator. If you buy a used attenuator, you should test it for accuracy, which you can do with the tinySA itself using its signal generator as the source signal (procedure at ) or with another instrument such as a NanoVNA. The NanoVNA is nice because it can easily produce a display of attenuation over a range of frequencies.
For testing an HT, I would start with the 30 dB fixed attenuator plus a setting of 40 dB on the step attenuator. That would reduce the expected +37 dBm input signal from the HT to -33 dBm. Then I would reduce the amount of attenuation in steps until the internal attenuator turns on, then back off from that until it turns off again. That procedure gets maximum dynamic range and minimum distortion from the tinySA. The actual output of "5W" handhelds varies a bit, but I'd typically end up with about 35 dB on the step attenuator. Once you have dialed in the needed amount attenuation, you can set that in the tinySA so that it will directly display the actual signal levels.
ALWAYS start with at least as much attenuation as you need, adding a bit more for safety if possible. You can then reduce it to the optimum point. If you start with an inadequate amount you can destroy the front end of the tinySA, and you don't want that.
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
I put 80dB attenuation between 1 Watt and the SA! Very good signal resolution. I do NOT like to use the internal attenuator because using it means you CANNOT use the LNA and the LNA is your friend!
?
Matthew KD6KVH
|
How do you figure 80 dB of attenuation from a 10-watt radio?? 80 db might be appropriate for a 100-watt radio, but he didn't mention that.? I may have misread.
However, yes, don't rely on the internal attenuator.? You burn it out and you must replace it.? Attenuators are a good insurance policy.
Dave - W?LEV
On Mon, Jan 20, 2025 at 10:19?PM Matthew Rapaport via <quineatal= [email protected]> wrote: I put 80dB attenuation between 1 Watt and the SA! Very good signal resolution. I do NOT like to use the internal attenuator because using it means you CANNOT use the LNA and the LNA is your friend!
?
Matthew KD6KVH
|
Never connect a transmitter directly to the tinySA, an external 60dB 10 watt attenuator would be a good place to start. Can get cheapies at Aliexpress and like someone else said check with a nanoVNA. Ham swap meets is another place to check, often able to pick up a directional coupler as a lot of people don't understand their function. The other potential problem is DC, not sure if the frontend of the tinySA has a cap to stop DC, but on HP and other Spec Analy it's common to use a DC blocker at the input. Eric would be able to answer this one.
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
Oh if you do use a directional coupler, you will need to terminate it with a dummy load.
On Tue, 21 Jan 2025 at 11:39, Dave < davepm@...> wrote: Never connect a transmitter directly to the tinySA, an external 60dB 10 watt attenuator would be a good place to start. Can get cheapies at Aliexpress and like someone else said check with a nanoVNA. Ham swap meets is another place to check, often able to pick up a directional coupler as a lot of people don't understand their function. The other potential problem is DC, not sure if the frontend of the tinySA has a cap to stop DC, but on HP and other Spec Analy it's common to use a DC blocker at the input. Eric would be able to answer this one.
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
Not 10 watts, 1 Watt! Yes it's much more than the minimum needed to protect the unit, even to get a decent undistorted signal. I can only say try it--what have you got to lose?--and see what nice signals, esp with LNA on, (measured harmonics and all) you get.
|
If you have a 1W transmitter, make sure the attenuator is at least double the power. Most handhelds are 5W so plan that you may accidently output the max. What lots don't know is attenuators can change when they heat up, if the resistor(s) to ground disconnects or goes open then you potentially?can overload your tinySA.? This is why in a lab directional couplers are used.? Attenuators are either a T or pi configuration 1 or 2 resistors to ground. For HAM use either is OK as long as it can safely dissipate?the power.
On Tue, 21 Jan 2025 at 12:44, Matthew Rapaport via <quineatal= [email protected]> wrote: Not 10 watts, 1 Watt! Yes it's much more than the minimum needed to protect the unit, even to get a decent undistorted signal. I can only say try it--what have you got to lose?--and see what nice signals, esp with LNA on, (measured harmonics and all) you get.
|
OK, I ordered the following:
Now as I understand it from the previous responses, I should be using the LNA in conjunction with these two,?correct?
Thanks, Joe
If you have a 1W transmitter, make sure the attenuator is at least double the power. Most handhelds are 5W so plan that you may accidently output the max. What lots don't know is attenuators can change when they heat up, if the resistor(s) to ground disconnects or goes open then you potentially?can overload your tinySA.? This is why in a lab directional couplers are used.? Attenuators are either a T or pi configuration 1 or 2 resistors to ground. For HAM use either is OK as long as it can safely dissipate?the power.
On Tue, 21 Jan 2025 at 12:44, Matthew Rapaport via <quineatal= [email protected]> wrote: Not 10 watts, 1 Watt! Yes it's much more than the minimum needed to protect the unit, even to get a decent undistorted signal. I can only say try it--what have you got to lose?--and see what nice signals, esp with LNA on, (measured harmonics and all) you get.
|
On Tue, Jan 21, 2025 at 07:29 AM, Joe Tomasone wrote:
Now as I understand it from the previous responses, I should be using the LNA in conjunction with these two,?correct?
No, to measure harmonics of a transmitter you need the highest possible dynamic range of the tinySA and that is without LNA
You only use the LNA when signals are barely/not visible
--
Designer of the tinySA
For more info go to
|
Erik, et al:
I share in Joe’s confusion / need for good, practical, well-described information. ?I’ve yet to read clear “connections” between theory / concepts and the equipment / devices needed to use these cheap and delicate tinySAs. ? Please bring the conversation down to earth.
73, Bill AI5RP ++++++++++++++++ Bill Blodgett (former senior technical writer at Vought Aeronautics)
Arlington, Texas
toggle quoted message
Show quoted text
On Jan 21, 2025, at 10:05?AM, Erik Kaashoek via groups.io <erik@...> wrote:
? On Tue, Jan 21, 2025 at 07:29 AM, Joe Tomasone wrote:
Now as I understand it from the previous responses, I should be using the LNA in conjunction with these two,?correct?
No, to measure harmonics of a transmitter you need the highest possible dynamic range of the tinySA and that is without LNA
You only use the LNA when signals are barely/not visible
--
Designer of the tinySA
For more info go to
|
On Mon, Jan 20, 2025 at 01:45 PM, Shirley Dulcey KE1L wrote:
The internal attenuator in the tinySA Ultra is an active device, and as such it causes some distortion.
It uses FET switches and measuring the tiny amounts of distortion produced by them is a very difficult undertaking involving carrier phase and amplitude cancellation techniques.? It will not be an issue in any normal measurements.
Use the attenuator it is an essential part of the instrument.?
Use of any LNA will decrease the dynamic range of the analyzer, only use it when other techniques (less attenuation, more averaging, narrow IF bandwidth) are not enough to dig your signal out of the noise.
73, Don N2VGU?
|
Another good method to ease measurement of harmonics is to build a simple diplexer (a highpass filter behind a 10dB or greater attenuator will also work) and separate out the fundamental from the harmonics; this will greatly reduce the dynamic range requirements on your spectrum analyzer.? If you put the diplexer on the low-power side of an attenuator its power requirements are reduced, so cheap components will work..
Of course this is impractical for a 160-6 meter radio, but for a single band rig is simple.? Of course you will need to calibrate out the losses but you would do that anyway.
73, Don N2VGU
|
I'm having a hard time squaring all the different calculations proposed in this thread.?
Let's say that for starters, I want to view/compare the harmonics from several HTs.? ?The 40db attenuator has arrived, the step attenuator has not yet.? ?
What power levels from the HT are safe to use with the TinySA Ultra both using and not using the internal attenuator?
The lowest power HT I have is the Yaesu FT-2D, which outputs 100mw on the lowest power setting.?
Joe
On Mon, Jan 20, 2025 at 1:45?PM Shirley Dulcey KE1L via <mark= [email protected]> wrote: You will need a bit more attenuation than that. And still more if you want the most accurate measurements possible.
The math is simplest if you do the calculations in dBm (dB referenced to 1 milliwatt). 1mW = 0 dBm. 1W =?+30 dBm. 10W =?+40 dBm. For HTs and QRP rigs, perhaps the most important number is that 5W =?+37 dBm.
The maximum permissible input to the tinySA Ultra is?+6 dBm (4 mW). If you are applying a?+37 dBm signal, you need 31 dB of attenuation to decrease that to?+6 dBm, more than the 25 dB external attenuator that you proposed, and a tad more than the 30 dB attenuators that are popular surplus items. And you want a bit more in case your HT produces more than 5W; I'd recommend starting with at least 34 dB, which would make you safe for up to 10W.
The internal attenuator in the tinySA Ultra is an active device, and as such it causes some distortion. That will make the device under test (DUT) look a bit worse than it actually is. For best measurement accuracy, you want the internal attenuator to be inactive, which means you need an additional 30 dB of attenuation to get down to the range where it's not used. That theoretically comes at -24 dBm, but the auto mode of the tinySA is a bit more conservative about using the attenuator; you'll get down close to -30 dBm before it turns off.
For my measurements, I use a 30 dB fixed attenuator with a 20W rating, plus a step attenuator. For testing higher power radios I also have a 20 dB fixed attenuator with a rating of 150W that I can add to the chain. It's often difficult to find the rating of surplus step attenuators; it's safest to treat them as having a maximum input rating of?+17 dBm (50 mW). Some fixed attenuators specify an input end and an output end; make sure to heed those, or else you can burn out your attenuator. If you buy a used attenuator, you should test it for accuracy, which you can do with the tinySA itself using its signal generator as the source signal (procedure at ) or with another instrument such as a NanoVNA. The NanoVNA is nice because it can easily produce a display of attenuation over a range of frequencies.
For testing an HT, I would start with the 30 dB fixed attenuator plus a setting of 40 dB on the step attenuator. That would reduce the expected +37 dBm input signal from the HT to -33 dBm. Then I would reduce the amount of attenuation in steps until the internal attenuator turns on, then back off from that until it turns off again. That procedure gets maximum dynamic range and minimum distortion from the tinySA. The actual output of "5W" handhelds varies a bit, but I'd typically end up with about 35 dB on the step attenuator. Once you have dialed in the needed amount attenuation, you can set that in the tinySA so that it will directly display the actual signal levels.
ALWAYS start with at least as much attenuation as you need, adding a bit more for safety if possible. You can then reduce it to the optimum point. If you start with an inadequate amount you can destroy the front end of the tinySA, and you don't want that.
I just received the TinySA Ultra.? ?As a first practical use, I want to measure spurious emissions from my various transmitters.? ?However, I understand that there is a maximum of -25dbm on the low input, and a maximum 30dbm internal attenuator.? By my calculations, this falls far short of even a 1w transmitter.??
?
Am I correct in assuming that connecting a 1w transmitter (an HT, say) to the TinySA via SMA cable to the low input will be definition require a minimum of a 25dbm attenuator plus the internal 30dbm attenuator to get a 1w signal under the -25dbm low input threshold?
?
?
?
?
|
On Tue, Jan 21, 2025 at 06:30 PM, Joe Tomasone wrote:
The lowest power HT I have is the Yaesu FT-2D, which outputs 100mw on the lowest power setting.?
When figuring power levels, assume that something will go wrong and it will transmit at full power.? To do otherwise is to court disaster.? You can tweak levels once you have a working, stable setup.
Learning to think in dBm for power levels (100mW=+20dBm) will help you do the calculations more readily.? Power is in dBm, gain or attenuation are in dB; watts just don't work well.??
?
There are also different power limitations on your analyzer.?
The damage level is the highest one.?
There is a power limitation to the input attenuator.
?
Then there is the power going into the input mixer, which determines the level of internally generated distortion products.?
Many commercial analyzers specify their attributes (internal IM, harmonics, etc.)at -30dBm or -40dBm into the mixer.?
So you need to understand how much power is going into the input connector and what attenuation you have dialed in between it and the mixer.
This working level will be much lower than the damage or mixer overload level, and you may need to adjust your levels via external and/or internal attenuation to optimize performance.? If you can remove a step of attenuation without changing the distortion levels you are still in a linear range and are not overdriving the mixer.? If the distortion gets worse, add attenuation back.? Some commercial units have 1dB or even smaller attenuation steps to more finely adjust the attenuation for finding the sweet spot between noise and distortion.
It is good practice to use at least 10dB of front end attenuation to present a good VSWR at the analyzer input.? Many analyzers default to this value and make you type the number in (no up-down keys or knob) to select 0dB.?
?
You should only engage the LNA when your other efforts to pull a signal out of the noise have failed.? Try lowering attenuation, narrowing the IF bandwidth or use/increase averaging first.? An LNA will always reduce your dynamic range and will be more prone to distortion than the mixer.??
?
These are powerful instruments but it takes some work and study to make the most of them.? ?
?
Here's a good intro to spectrum analyzers from Keysight: ?
Of course Alan Wolke, W2AEW, always has great videos: ?
?
73, Don N2VGU
?
?
?
?
|
?"You should only engage the LNA when your other efforts to pull a signal out of the noise have failed..."
?
You don't know what signals are there *unless* you try the LNA. You can always turn it off again. In any case if you use the MEASURE menu I believe the SA takes control of such things anyway...
?
?
|
Shirley Dulcey KE1L
Donald S Brant Jr