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DC coupled 2.7 GHz Active Probe Project - Now Available!
nctnico:
First of all I think it is fantastic to get to such a nice probe at this price level. With a lower input resistor, the attenuation also gets lower if I'm not mistaken. In my view having a 100k Ohm input impedance is still great for many purposes. Maybe it is an option to have 2 versions. One high impedance version with a slightly higher pickup of external noise (which can be eliminated by testing inside a shielded chamber, room or tent) and one lower impedance version more suitable for looking at high speed signals in typical 50 Ohm systems.
joeqsmith:
For the three sweeps shown in my previous post, both the signal tip and ground tips are floating. The only electrical attachment was to the spectrum analyzer. The 10dB attenuator was inserted for all three sweeps. Note RBW was changed (set to auto).
I think the noise level is fine, depending on the application. Same for the higher DCR. If you do decide to change it, you may want to consider offering two separate products. Personally, I would rather the lower noise, lower dynamic range, lower DCR but can certainly see wanting what you have as well.
I think the biggest contributors of noise in my lab are the 2 & 5GHz and my PC. Of course, then there is the device I am trying to measure. If you do come up with a new design and you would like me to provide feedback, I'm certainly willing to try and help out.
lasmux:
--- Quote from: nctnico on May 29, 2024, 07:42:07 pm ---First of all I think it is fantastic to get to such a nice probe at this price level. With a lower input resistor, the attenuation also gets lower if I'm not mistaken. In my view having a 100k Ohm input impedance is still great for many purposes. Maybe it is an option to have 2 versions. One high impedance version with a slightly higher pickup of external noise (which can be eliminated by testing inside a shielded chamber, room or tent) and one lower impedance version more suitable for looking at high speed signals in typical 50 Ohm systems.
--- End quote ---
Thanks for the kind words!
Having two versions with different input impedances is an interesting suggestion. It makes the manufacture process a bit more difficult/expensive, but ultimately, different people have different needs, so maybe it's worth it.
--- Quote from: joeqsmith on May 29, 2024, 07:52:46 pm ---For the three sweeps shown in my previous post, both the signal tip and ground tips are floating. The only electrical attachment was to the spectrum analyzer. The 10dB attenuator was inserted for all three sweeps. Note RBW was changed (set to auto).
I think the noise level is fine, depending on the application. Same for the higher DCR. If you do decide to change it, you may want to consider offering two separate products. Personally, I would rather the lower noise, lower dynamic range, lower DCR but can certainly see wanting what you have as well.
I think the biggest contributors of noise in my lab are the 2 & 5GHz and my PC. Of course, then there is the device I am trying to measure. If you do come up with a new design and you would like me to provide feedback, I'm certainly willing to try and help out.
--- End quote ---
Okay, I'll have a look and see where I end up with a new alternate version. In general, thank you for your support in this process so far. I really appreciate the interest you've taken in this project.
lasmux:
Announcement time! We've teamed up with SJL Instruments, creator of the GigaWave 6GHz sampling oscilloscope, to offer a US$300 voucher for an SJL oscilloscope when you buy a probe 8). Given the price of the probe is only $225, and the oscilloscope (which is excellent) was already really well priced at $2295, this is a great deal! In general, the two devices really complement each other given their pricing and bandwidth/performance range, so this collaboration was a no-brainer for us.
As the Gigawave scope has SMA inputs, there’s now a new version of the probe available with an SMA-SMA cable. This is selectable on the site. If you’re wanting to use the probe for connection to a spectrum analyser of VNA, this is also more convenient.
lasmux:
To add, if you've already purchased a probe and want a voucher code, let me know and I'll send you one.
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