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Projects, Designs, and Technical Stuff / Re: Schematic/PCB Review
« Last post by teletypeguy on Today at 03:53:15 pm »
Well the rf reception game is all about signal-to-noise ratio (snr).  Boost the signal with a low-noise-amp (lna), and it boosts the signal, and, duh, has low noise to boot, so snr goes up.  It can't boost the signal so high that it overdrives the receiver front end, of course.  Typical lna gets dc power through the coax center conductor, fed through a choke inductor (hi-z at rf freqs) at the receiver end.  The lna also has a choke to get the dc off the cable, and a cap to couple the amplified rf back onto the cable.

I use neo-6 daughterboards from ebay, which have a uFL connector, and also have the dc choke to power an active antenna, should one be connected.  Attached pic shows patch stuck to top of neo-6 board with double-sided foam pad and uFL connected.  I have amplified gps puck antennas with sma connectors (they are usually sma, not uFL) like this, and sma-to-uFL adapter cables like this  Don't get a reversed-polarity sma -- those goofy things were a work-around so router manufacturers could use an "external" antenna that was not a "common" connector so users could not easily change to a high-gain yagi or such and violate their fcc/ce/ce testing.  Patch antennas usually have a uFL and that is a good option for your board (and leave the choke circuitry so you can power an amplified antenna).  Remember that if you solder a patch to the board, it must face up, but an antenna with a bit of wire allows your pcb to be mounted however you want.

So I start testing with the amplified puck, in my electromagnetically-noisy lab, with a roof attenuating the signal, and see low long it takes to lock and get up to four or more sats in view.  If I put the puck on the window ledge, it'll lock faster.  Faster still outside.  Then try the little passive patch.  Longer lock, but after a few minutes inside it seems quite good, and outside, no problem.  So try some tests with your proto.  If it works in the backyard it will only get better at altitude.  Mouser UK has these molex parts, with some nice little peel-n-stick antennas

If you want something outside the payload (magnetometer...) you can put it on a boom or hang it above on the string that goes up to the chute (a hassle if it is i2c or such that needs care with long runs) but it will be in bitter cold so get a part spec'd to -40C if you can.  It might hit -60C or lower out there.
 Crystals are easily found to -25C (inside the insulated payload will be warmer).

I hang my tracking tx antennas (three 2m dipoles on a wood dowel jack) below the payload.

I lost an expensive payload once since I only had one gps/track-tx, and I now always have two systems (separate batteries/gps/tx/antenna).  Keeping the tracker simple/small/light/low-power is nice.  That's why I use an stmF0 part.  You might want to offload camera stuff to a separate board.  I like these mobius cameras and have had three facing different up/down/sideways  Then if one craps out (it has) I still have video.  If one tracker dies I have a backup.  And some fox-tx sort of signal to rdf with a yagi if the final gps coords are not super close.

I have use ST's standard-peripheral library for F0/F3/F4, which they stopped developing, so I have not tried any L parts.  I don't use HAL or that goofy cube bloat.  Yes, parts have been impossible to find for a year, and are still looking bad.  Sometimes you need to take a chance on an ebay or amazon seller, but watch for china counterfeits.

Ahh, must get to work, sigh.

For me it's clear now that Artix US is not the replacement for Artix, for some applications US suits much better, but for others Artix is fine.
Well it could be a good replacement for higher end Artix devices, as long as you don't require massive IO count some of those old Artix'es have.

But what is interesting is that they effectively undercut their low-to-midrange Kintex-7 devices (again, provided that you won't require an extra IO of Kintex'es). If you look at AU25P vs K325T, in appears that the former is better in just about any metric, and, importantly, it's available with a free license (you have to buy a license to use K325T devices). Similarly, AU10P seems superior to K70T, as is AU20P to K160T - new devices are faster, cheaper, support modern and faster memory and IO standards, and more power-efficient.
Power & Renewable Energy / Re: My Bullsh*t Sensor is Pinging
« Last post by TimFox on Today at 03:50:07 pm »
It still is common to add "silicone" to the confusion of terms.
FPGA / Re: Ring Oscillator on an fpga
« Last post by dolbeau on Today at 03:48:35 pm »
Depending on what you do, you might try to reuse an existing open-source design (e.g. the betrusted project has a TRNG TRNG characterization and Migen source code as they are Litex-based)
Repair / Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Last post by JohnAH on Today at 03:48:18 pm »
I don't know what is going on with my posts but a lot of them are getting truncated.

Yes found it. R105 had a cracked solder joint. It is passing everything now.

Thank you Dr Frank.
Beginners / Re: Capacitor parasitics
« Last post by TimFox on Today at 03:47:56 pm »
Yes, "impedance" in this discussion is the magnitude of the complex variable, which can be expressed as the hypotenuse of a right triangle with reactance and resistance on the other sides.
A problem with capacitors is that the ESR is not constant with frequency:  part of it is "parasitic", due to lead resistance and resistance of the electrodes, and part of it is "dielectric loss".
Very, very roughly, dielectric loss for a plastic film has a somewhat constant Q = 1/D value, which gives a strong dependence of ESR on frequency.
I don't believe Spice allows a straightforward capacitor model given by a constant Q.
RF, Microwave, Ham Radio / Re: NanoVNA Custom Software
« Last post by ALW on Today at 03:46:47 pm »
Forgot to mention that I am using a Surface with 2160x1440 resolution. The unmodified / standard magnified window was blurry and difficult to read. With the settings above it is crisp and clean.
Projects, Designs, and Technical Stuff / Re: German datasheet notation?
« Last post by TimFox on Today at 03:41:27 pm »
The English abbreviation "IC" for "internal connection-do not use" (per RCA tube manuals) is very common on vacuum-tube data sheets.
The pin through the "button" base is a convenient place to support one of the internal bits of the tube, and that pin on the socket should not be used as a connection lug. 
Unused pins where the socket pin may be used are abbreviated "NC-no connection".
What is the literal meaning of the abbreviation "iV" in German?
Got the fault?
From the webinar today, see the attached image for the performance comparison between Artix UltraScale+ to Artix7.
Thanks for the news.

For me it's clear now that Artix US is not the replacement for Artix, for some applications US suits much better, but for others Artix is fine.
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