The signal source I mentioned is ERASynth Micro ESM-1206
I purchased it on a Croud sourced deal about 2021. May not be available now.
I sent ERA asking about availability and will pass along if they respond.
https://www.crowdsupply.com/era-instruments/erasynth-micro [erasynth-micro-main-clipped_jpg_open-graph.jpg] ERASynth Microhttps://www.crowdsupply.com/era-instruments/erasynth-micro crowdsupply.comhttps://www.crowdsupply.com/era-instruments/erasynth-micro
This is open source so in theory you could make your own.
Bob
On Mar 7, 2025, at 7:59 AM, Corey Minyard via pacsat-dev [email protected] wrote:
On Fri, Mar 7, 2025 at 7:34 AM Corey Minyard via pacsat-dev [email protected] wrote:
I realized a problem with the AGC design I talked about: The output impedance will vary a lot with gain. I'm not sure how much of a problem that is, I guess it depends on what it's driving, but it's definitely an issue. I'll have to simulate that.
One other thing I forgot to mention was that the transistors I was using are switching transistors, not RF amplifiers. So they aren't going to perform very well as amplifiers, but I can't find any suitable RF amplifier MOSFETs or JFETs with simulations available. They have poor amplification characteristics. I didn't show the curves, but the ones I used start to lose gain at about around 10MHz; they were 6dB down at 40MHz. Unless it's something about the circuit design, but that's pretty straightforward.
And apparently you have to know device geometry to create simulation models.
Another question on that: the input to that MOSFET is obviously going to be high impedance, but it's coming from a filter that's going to be low impedance. (high impedance LC filters don't seem to be feasible). Normally you would put a resistor to ground to terminate the connection, but then you are introducing noise. Is that an issue? Since the frequency is fixed, could you put an inductor of the right value there?
Also, Bob, you mentioned building boards for testing. How do you do that? Do you put a zero-ohm resistor between sections and an SMA connector on each side of it? You probably want some way to enable power per section. Anything else I need to worry about?
As far as building boards, getting the board itself isn't that expensive, but how much does it cost to populate the board? The processor is a BGA; I'm not sure I can solder that, and having someone else handle all the soldering would be nice.
Also, there's the signal generator you mentioned. I found a couple, like https://www.amazon.com/Seeku-WB-SG1-Signal-Generator-1hz-8ghz/dp/B082WBZ9S3 but I'm not sure which you are talking about.
Thanks,
-corey
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