Notices by ftg (ftg@mastodon.radio)

@whitequark
Oooh, that's a better way to approach it than trying to use search engines to figure out what SoC they have this time.

@f4grx @whitequark
Single balanced mixer with BAT15-099.
The "U" shape on the side of with two pins of the SOT23 package is the transformer that does the 180 degree phase shift. And does the balanced part of single balanced mixer.

@whitequark
And it's a rather straightforward centimetric-wave (10.525 GHz nominal) doppler radar at that.
Single transistor DRO oscillator, couple of radial stubs, one power splitter and a single balanced diode mixer.

@azonenberg @rubylith
This thing has 47 - 860Mhz analog BW with around 30 to 35dB dynamic range
https://www.aliexpress.com/item/1005007993191807.html
So might do what is desired with some mods.
And the bare TX diodes with a fiber pigtail are around 35eur in single quantities on ali as well:
https://www.aliexpress.com/item/1005004962580681.html

But I wonder if some FM modulated, free running 4 - 6 GHz VCO would be enough.
All my surplus 4GHz band VCO's have less than 200MHz of good tuning range.
You might have to downmix two high band osc's.

Btw ever seen an antenna installed like this?

#hamradio #shortwave #antenna

@whitequark @AMS
No, it's because the Analog Devices supplied gateware for the FPGA is fundamentally flawed form what I understand.
Conveniently that means Pluto never competed with their customers, unlike what LimeMicrosystems did to theirs.

@AMS @whitequark
It's not about the frequency accuracy, even if that also helps.
But about time stamping the samples and being able to tell the SDR " I want these samples to go out at this point in time".
LimeSDR and BladeRF can do that.
Adalm-pluto and it's derivates cannot.
This functionality is required for GSM and especially LTE.

@whitequark
srsLTE and I think Yate has made the LTE side easy.
srs used to advertise that you could set up a GSM base station with three lines in the terminal on Ubuntu. I think they can now do the same with LTE?

The limited equipment part is unfortunately hard, as LTE really does need an SDR with proper sync, so that the TX and RX are in tight sync.
So it's not currently possible to do cellular with two hackRF's or even cheaper, with an rtl-sdr and osmo-fl2k.
Except maybe some 1g stuff.

@whitequark
Very likely, depending on your definition of cheap.
I have been dreaming of GSM base stations with 20eur BOM, outside of a linux SBC to run the high levels of the stack.
But current day it's still BladeRF/LimeSDR territory, so +500eur for the radio and something in the raspberry pi 4 scale to run the GSM/LTE stuff.

It works!

#122GHz #VK3CV #mmW #microwaves

The problem with harmonic mixers is all the harmonics and images.
It does not help that the mixer I'm using to receive this 122.8GHz transmission is the 50-75GHz model, so I'm using it out of spec as well.

@BrucePerens_K6BP
Could be that.
And with the small loops the selectivity and ease of nulling out local interference also helps.

@BrucePerens_K6BP
Most use the coax feeding it, as apparently 0.05 wavelengths is optimal (according to some simulations I cannot make google find right now), so doing it with the coax feedline is easy.
The end-feds people build here in Finland all seem to include a ferrite choke in the feedline a slight distance from the antenna impedance transformer.

@Nixie
Things like Rothman lenses are proper magic.
But they sure are not as visually complex.

@ret @Nixie
I guess?

900MHz or 700MHz duplexer btw?

@gigabecquerel
Where did you buy the micrometer mechanism?
I might have a use for a few small one's and I'm interested in what they usually cost.

Well, what the one's that are not from Puuilo or Lidl.

@gigabecquerel
Excellent, thank you!
My potential use a little bit different. As I want them for fine tuning some mmW Gunndiode oscillators I plan on building at some point in the future.
When I get better at machining.

If some of you have not noticed, Valve is giving out Half-Life 2 (and episodes 1 and 2) for free this weekend.

https://store.steampowered.com/app/220/HalfLife_2/

A handy indicator

Whee!
Been a good while since I bought a new game on release.