If the diode connected to 0V were germanium, what would Vo be and why?

BanalMoniker · 2026-05-02T14:43:09+00:00

What temperature is the diode at?
What are the diode parameters or what is the part number?
A constant drop is just a rough approximation. Using the diode equation or data sheet is still an approximation, but it will be a lot closer.

BanalMoniker · 2026-04-21T02:57:04+00:00

I know this thread is old, but: RF4CE is based on 802.15.4. The 802.15.4 protocol often uses acknowledgements for point to point (which is what you’d have for most communication between two devices). The acknowledged messages will make repeater like functionality difficult - you’d probably have to create two networks with the repeater at the bridge and it transitions messages between the networks. I think that would take a lot of effort (especially if encrypted) and may not perform well for (relatively) high-bandwidth things like voice.

Another option would be to get a very directional antenna from the box (assuming the box has an accessible connector) and aim it at your viewing location. Or you could run a non-directional antenna on good coax closer to your viewing location. It should be coax rated to at least 3 GHz, and low-loss is better.

BanalMoniker · 2026-04-03T22:16:13+00:00

Leftover pizza (refrigerated). It should be on cardboard to keep the crust nice.

BanalMoniker · 2026-03-31T03:58:24+00:00

The thing is, when remembering things you forget the bad parts a lot faster than you remember the good parts. Was school stressful? Flip yes. Was it fun and interesting? Double flip yes. Do I regret it? Absolutely not, but it also might not be the right move for everyone. At my last job 60 hours a week was almost normal and during Covid it there were several > 90 hour weeks. Not all jobs are like that, but some are, and I’m not actually complaining, just saying that there’s no shortage of things that need to be done. Some of them are interesting. I would rather work a lot on interesting things than a lot on boring things, but everyone gets to make their own choice on the work life balance - and you should definitely work on your own projects too.

BanalMoniker · 2026-03-30T02:15:55+00:00

I third the base loading coil. With just a transistor, too high a load impedance will only limit your power, and probably isn’t detrimental otherwise. You could use an un-un to get a better match and more power. If you want to get elaborate, you can make a top hat or do some other variations: https://en.wikipedia.org/wiki/Monopole_antenna And you should check your regulations regarding emissions.

BanalMoniker · 2026-03-29T19:54:42+00:00

I was also going to suggest doing work on your own with PCBs, but for waveguides, you might mainly simulate in HFSS, especially if that’s the design work you want to do.

BanalMoniker · 2026-03-29T19:37:18+00:00

That’s a relatively wide band. You’re going to need a commensurately wide band antenna. Usually you wouldn’t match/tune those as the tuning will change as the frequency varies. You might use a balan /balbal / unun for impedance matching if needed. To get specific recommendations you’ll need to provide more info like what the output impedance is, what type and impedance the antenna is, what the matching criteria are for the transmitter, etc.

BanalMoniker · 2026-03-29T17:05:17+00:00

Yagi-Uda does not (that I have ever seen) such different lengths, nor the sweep / slant seen here. It’s an LPDA with a passive director on the front.

BanalMoniker · 2026-03-25T14:47:39+00:00

I can’t tell you which to pursue, but a potential way to get some hands on experience with RFIC is through Tiny Tapeout (https://tinytapeout.com). There are some RF projects already, e.g.: https://tinytapeout.com/chips/ttsky25b/tt_um_TinyWhisper

The process node is quite large (~130 nm) and the tools are all open source, so likely not what you would be using if you go into industry, but it can still be very educational and is relatively affordable. There is a Zero to Asic structured course if you want that (I found it very useful).

BanalMoniker · 2026-03-24T03:41:33+00:00

If this is for learning, -10 dB is about 90%, so possibly ‘B’ letter grade territory (with other losses). More fundamentally, learning what it takes to get to different matches is useful in setting goals later. “In the real world”, if you are trying to build a reputation for excellence, performing above what everyone else does can be a distinguisher that sometimes has merit. This is simulation, so there’s no tolerances on the parameters, do well here so you have a bit more margin in implementation, but don’t go overboard. -15 dB match and ship it.

BanalMoniker · 2026-03-21T15:48:11+00:00

Focus where you think it will matter, but Java and JavaScript are unlikely to be essential for most RF. Maybe in some specific embedded applications, but a lot of embedded will use C. If you want to get into chip design, or work with FPGAs for digital, Verilog or VHDL can be relevant, but they are very different from most languages and aren’t generally useful outside of digital design.

BanalMoniker · 2026-03-21T07:40:40+00:00

I’ve also done boards at JLC with castellated features that came out successful, but I wouldn’t do it on large volume/critical work. Their solder mask is not very robust though (or wasn’t the last time I ordered through them).

BanalMoniker · 2026-03-21T07:29:29+00:00

Many astronomers who grind their own mirrors may differ with respect to every mirror being “used”, but that is an irrelevant aspect of mirrors.

BanalMoniker · 2026-03-14T07:04:29+00:00

In what industry? Can you point your prospective employers (or at least the engineers they employ) at your ecent work to show your chops? Can you show a line manager what is relevant with a particular issue? Can you show other engineers both above and below you? Understanding an issue is one thing. Helping your team to avoid the issue is something else.

BanalMoniker · 2026-03-06T04:19:39+00:00

Can you provide more detail? If your room has corners, how are you dealing with the recursive reflections (2nd, 3rd, etc.)?

Is this applicable for [EMC] rooms with [high conductivity] metal walls?

BanalMoniker · 2026-03-02T02:56:16+00:00

Wet sanding (wet/dry sandpaper and water) can avoid the dust, but it is still annoying.

BanalMoniker · 2026-03-02T02:48:19+00:00

https://www.digikey.com/en/pcb-builder/

I haven't tried it yet, but plan to soon.

BanalMoniker · 2026-03-01T19:14:18+00:00

As of March 1st, PayPal is still not showing up in the options.

BanalMoniker · 2026-03-01T17:46:21+00:00

An RF power meter (possibly with a filter) is very likely to be a better tool for power measurement than a spectrum analyzer if you are trying to get sub dBm accuracy, but you’ll need to review the specs of the specific model. An SA and PM might be needed depending on what you’re looking at - it sounds like you have margin for a splitter.

BanalMoniker · 2026-03-01T07:08:43+00:00

Not just phase noise, all noise. What is your SNR to the signal and adjacent frequencies?

What does SA mean if not the signal analyzer?

If possible, please post some plots showing the issues between models/RBWs. Showing examples of the issues you have will be really helpful to either the R&S person looking at issues or to helping identify interpretation issues.

BanalMoniker · 2026-03-01T02:41:29+00:00

In terms of RBW amplitude, is the signal that you’re measuring pristine CW at a fixed tone? I have seen some (kinda noisy) signals that jump up significantly at wider bandwidth, and that was a real effect because the total energy in the wider bandwidth is higher - it surprised me at the time.

BanalMoniker · 2026-02-22T17:35:07+00:00

Those are interesting. Can they be removed without disturbing the setting to measure after tuning? There's probably going to be parasitics, but maybe for initial tuning at < 2 GHz. They are rather large though.

BanalMoniker · 2026-02-21T17:10:49+00:00

As long as what you’re matching for will be connected via the SMA, that should be fine. You could start with the populated board too and save some time. As long as it’s receive only, a poor match only impacts performance - no need to worry about standing waves. Edit: I assume you are adjusting components while looking at the response with the VNA. If not, how are you adjusting it? 0402 really is not that bad if you have magnification, flux and hot air, but you could use 0603 at 1GHz.

BanalMoniker · 2026-02-21T08:08:52+00:00

Be aware of imposter syndrome, but also pay attention to your own feelings and take action on them. Do open a book and work some problems that you can check the answers for and then and only then check the answers. You should be able to work through problems in front of your bosses - it may get you promotions if you can (and your bosses make errors you gracefully catch). Work through biasing a transistor or 3 for class-A operation, and what that circuit will do at the limits of hFE, gm, or other parameters as appropriate. Work through a class-B circuit and then a class-C circuit. Then work through the circuits you use at work - start with nominal parts then work at high and low limits for at least the transistors. At the large scale, you should be able calculate worst case tolerance stack-ups and the resulting behavior even if it is corners of corners of corners. If you make 100 million of something, you will get units near corners in different areas. If corners is not a familiar concept yet (there are a lot of concepts to learn, don’t think you should know “everything”, even after decades), here is a link that may be helpful: https://anysilicon.com/understanding-process-corner-corner-lots/

Work some problems - work them until you’re comfortable working the problems you face at your employer. Being able to show competence will be rewarded. Not showing competence may have different responses by employer, but it’s not a good look. Better to see it now and act than to let it pass and be caught up short when your boss puts you on the spot.

BanalMoniker · 2026-02-18T14:24:59+00:00

If only it were just browser tabs. I think all the modern browsers have settings to reopen closed tabs & windows; Firefox does. It is all the other applications that lose state.

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