Notices by ftg (ftg@mastodon.radio)

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.

Modern internet connections are nice. 160gb game and it takes 1hour to download.

In 2003 it took a day to download Half-Life 2 on my connection.
Had to run it all night and day.

@whitequark @mossmann @LaF0rge
I think it was by Jolly (sadly don't know their mastodon handle, if they have one). Excellent work in any case.

@mossmann @whitequark
And now there is also osmocom-analog, so the network side can also be done. With as little or as much SDR as desired.
http://osmocom-analog.eversberg.eu/

It also supports the 450MHz NMT450 and MPT1327, so no need to try to find a quiet spot on 900MHz either.

@ryanc
I'd say yes, for the 4x4 one.
TX and RX should be the same polarisation for the pair.

@azonenberg @dlharmon @g4dbn
Friend has simulated some stuff relating to that and it seems to simulate up to 20-30GHz with 0.086 semirigid at least.
The thing apparently is to get the launch really good.
So cutting a slot to the PCB for the coax and soldering it to the grounds was apparently critical for good return loss.
Our discussions and his simulations were mostly from the point of feeding LO to homebrew harmonic mixers.
Because I wanted to push 18GHz or preferably 38GHz to a 76GHz rig.

@azonenberg @dlharmon @g4dbn
I'll link this thread to him and ask for input :D

But bending the center over gives an impedance bump and that limits the performance.

The main reason for cutting the slot was get rid of that center conductor to PCB trace bend and impedance bump.

@azonenberg @dlharmon @g4dbn
3/x
- The problems are the same as with coaxial connectors, if the ground path only goes from the bottom of the coax to the microstrips ground plane, the propagation mode of the coax is badly matched to the microstrip.
Some connectors try to mitigate that by having a small "roof" over the center pin solder pad to match the strayfields from the coax end.

Stupidity inbound.
The sheer audacity of building and selling a radar based on a regenerative receiver-transmitter while also selling it as a 2.4GHz one while actually operating on 3GHz turned out to be irresistible in the long term.
So now there's ten of 'em.

#microwaves #RADAR #sband #regen #superregen

@ryanc
Rack pix?
Rack pix!