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I did simulate this, with tapped capacitor transformers before and after the filter, going from 50 to 75, and back again. As impedance increases, the inductor values increase, which results in a lower saturation threshold, and only modest current reduction.. IE, the series coil went from 47 uH...
I clearly hadn't considered fully how the core would react as amplitude increased, especially the nonlinear response.
I haven't tried an iron toroid for the 47 uH... unfortunately I don't have one on hand that's big enough, but am going to order a couple to play with. The only "big" toroid I...
Yes... I did find a bigger toroid (3/4" OD) and wound a 50 uH inductor on it, and the effect was less, but still had an effect nonetheless
^ this occurred to us (myself and coworker) this morning. Simulation shows current through the 47 uH to be quite a bit higher than I though, but not to...
The filter was laid out on both a boardhouse-made pcb, as well as a hand made one:
The standalone one has been swept with two separate NA's, as well driven with a 1MHz source and output measured on a Spec An. It exhibits the same issues on all setups, so I don't think it's test equipment...
Hi All,
While not technically RF frequency, the 1 MHz signal in question is my IF output of my RF system, and I thought I might have a bit better response posting this here, rather than in the analog section.
I'm mixing together 1497 MHz and 1496 MHz to get a 1 MHz output IF, filtering and...
I can have the cable TDR'ed; I assume that it's imperfect though. There's at least one "splice" in it... pretty sure it was about 150ft too short, so the last 150 is an extension.
I hate to ask you to spell something out, but I'm confused as to how you arrived to 5 to 10 ohms from that...
Yeah the end is literally a mile away... it's part of a system that's installed in an accelerator, so it's got quite a distance to travel. That's why the IF is 1 MHz and not something higher... they usually use 15-30 MHz but the attenuation across the heliax is too great.
I'm obviously not...
I feel like I'm being stupid about this, but I need a sanity check.
In my attached schematic, my amplifier is driving a heliax cable approximately 1 mile in length, IF = 1 MHz, output power up to 20 dBm, must be linear within 0.1 dB. The heliax is connected on the other side to a 50 ohm load...
Thank you all for the responses, sorry I didn't get a chance before now to respond.
@ Borber's question about driving the transistor into a nonlinear region, the answer is I don't know? To be brutally honest, up to this point I've been a digital design guy and haven't touched a transistor prior...
I should explain the application...
RF input is 1497 MHz, level is -80 dBm to +20 dBm. There's two configurations for the receiver:
1) 4 dB conversion gain, relevant input level is -60 to +4 dBm, output signal level must not drop below 13 dBm for inputs 10 dBm and higher, noise figure <= 16...
Not sure if this belongs here or in the RF section.
Looking for a little advice from Analog/ RF Engineers:
My IF coming out of my circuit is 1MHz, and I'm using approximately the following amplifier circuit to amplify it:
It's taken from this paper...
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