20 GHz LNB teardown (and test)

[@BalticLab]

First! 16:50 no, that's where it's still ~10 GHz. The grounded 1/2 wave stub (thicker trace above your screwdriver) then shorts the 10GHz out but lets the 20 GHz pass. 17:02 right above the screwdriver is the 1/4 stub to short out the residual 20 GHz, be it the harmonic from the mixer or the input signal. That's why the trace below is so thin (=high impedance); So that the stub doesn't affect the input side of that segment. 16:25 The two black things are going to be mixing diodes. That's where the mixing happens.

[@perjorgenson1835]

That seems like a very standard frequency range for a Ka receiver. In my work we usually consider 17.7-20.2 GHz for space-to-earth (typically the higher end), and then 27.5-30.0 GHz for earth-to-space (also typically the 29-30 GHz end of it for remote terminal uplinks)

[@gorak9000]

In north America, all the fss satellites (C and Ku up to 12.2ghz) are linear, and all the dss satellites (ku above 12.2 ghz) for direct to customer services are circular. Ka is mostly circular everywhere. The AOR sats (atlantic ocean region) and POR (pacific ocean region) tend to be circular in cband and linear in fss ku. I've been meaning to do a better survey of ka band in NA, but other projects keep getting in the way. I have a ku dish and a collection of ka lnbs that cover the different ka bands. PLL ka lnbs are stupidly expensive in NA as they are only for special use. Pretty sure all consumer LNBs are dro as the frequency stability isn't that important for receiving wide TV and internet transponders, and dro is cheaper to manufacture.

[@MSM5500]

Circular polarisation was used by Soviets/Russki as they were not capable to build 3-axis stabilised GS satellites but 2-axis only so they continuously spun around the axis pointed towards the Earth. So for the sake of keeping continuous compatibility with the reception equipment they still use the custom made circular polarised transponders on French Eutelsat satellites. The dielectric depolariser is the cheapes yet the worst solution in terms of losses among the others. In my collection I've got two more types of Ku-band C120 flange prime focus combined feed horn circular de-polarisers such as *_"Squeezed Tube"_* & *_"Pin Pipe"_* depolarisers. Both are quite expensive in manufacturing.

[@gorak9000]

at ka band, they tend to use ribbed depolarisers - the waveguide has a series of bumps on the walls along the length of the guide. They are die cast in 2 halves and bolted together, so pretty cheap to mass produce

[@MSM5500]

@@gorak9000 _"a series of bumps"_ Yeah, I'm familiar with that. That's pretty much the same as "pin pipe" where the pin height varies along the path. The components I have are from late 80's & early 90's so they were made at the precision level as EIRP from old generation satellites was quite low and the dishes were 1.8m and up. _"pretty cheap to mass produce"_ There are lots of shortcuts in cheap consumer grade integrated LNBFs like, for instance, a receiving probe is simply sticking out just in the middle of a round wave guide without any quarter wave length impedance transformer in between as it should be.

[@zmarssojourner7435]

@13:02, you were talking about the squiggly trace which was a filter. How can any signal pass through, if the traces are broken? Isnt the continuity broken there? No electricity can pass though it, correct?!! Ty for the answer.

[@AxelWerner]

Do you know what a capacitor is? Two plates of conductor not touching. DC can't flow through a cap. However AC signals can. Same here. Since all this GHz black magic is so much higher frequency every length, width, distance of a trace becomes a capacitor and an inductor. Now simple shapes suddenly become whole filters, coils, caps, etc. This GHz magic really is black magic. Somehow it works.

[@dereksgc]

As the other comment says, alternating current can effectively "pass" through a small enough air gap, or other dielectric that normally wouldn't be conductive at DC. In this case the size and shape of the traces and gaps is chosen so they would specifically resonate at a certain frequency like little tuning forks, letting that frequency through while attenuating others

[@Max_Marz]

if that were true zmars, how would radio work at all?

[@Tadesan]

Magic

[@graealex]

@@AxelWerner These effects are already present with your mains frequency 50/60Hz. It's just that they are so small we never think about them, we just assume the electricity stays inside the designated paths, usually copper strands in isolated cables. Although recently, with the introduction of power-efficient LEDs, we see some of those effects, like light bulbs not fully turning off despite the switch being in the off position.

[@fsphil]

Fun fact, you may be able to use your hackrf to generate a signal for this and universal LNBs. If you transmit at say 5 GHz a useable amount of signal is leaked at 10, 20 GHz, and various other frequencies. I've used this trick to transmit analogue FM video across my house. At 20 GHz the signal is quite weak but it does work over about 5 metres. maybe more with a largerdish. Not sure if your hackrf case is metal, that might block it - mine just has the plastic GSG case. This matters as the signal is emitted from within the hackrf itself, not the SMA port.

[@markusm.lambers8893]

Don't you think the LNB was made in "08th of December 2021" ? I think the new regulations for giving the correct date, is that the date is strictly falling, from the year, ... over the month, ... to the day, ... ! (Example: 2021-12-08 = 8th of December 2021) Maybe that's right? Please go on, we all are interessted what is going on! I am working on QO100, I am an HAM-radio OP ! Happy new year 2025 and merry x-mas to you, ... ! 73 de Markus - db9pz - JN39fq - 3miles/5km east of LX - ----- P.S.: See the date on this second and older LNB, it is 2011 ! - How much was the price for the 'Irish-LNB' ? Where do you purcased it ? Thanks in advance, ... -----

[@dereksgc]

It is possible that it was 2021, maybe just utilizing old DRO stock because the Saorsat market isn't big enough to warrant production of 21 GHz PLL chips for these... I got both of mine from eBay from Vortex Satellite, you should probably just search "saorsat LNB" and see which offer is the cheapest for you, it depends on location

[@mifak666]

DIky. Stejne nechapu, jak muze byt tak divny oscilator vlastne tak stabilni.)) Pekny novy rok!

[@DoktorZhuzhyk]

Может из за параметрической платы?

[@canalcomentario]

Voce está nos EUA ou na Europa?

[@dereksgc]

czech republic

[@canalcomentario]

@dereksgc UAU, eu jurava que VC estava nos EUA, saudações do Brasil.

[@HA7DN]

Great teardown. I am wondering what you ment about DRO LNBs being more useful for ham purposes? Another note: I am revisiting some work I did this year, and checked your helical antenna calculator on your blog. I have reported this spring that your formulas there are wrong, but now I see you left them that way. You can see the details in the github issue I created, please fix it sometime!

[@dereksgc]

Thank you for the reminder, honestly I just forgot. I've had a few more people ask so I'll try to get to it this weekend. DROs are easier to repurpose for ham experiments, for example you can modify a DRO LNB to transmit instead of receive, and you can even modulate it relatively easily, impossible with PLL. There are also no filters or narrowly matched circuits that would otherwise be inside of the PLL mixer IC that you can not access

[@rawexploiterp6951]

Oh no! My brand new mouse pad!

[@shemmo]

Krásne Vianoce prajeme zo Slovenska 🎁🎄

[@enilenis]

Have one of those waveguide assemblies off a satellite dish I threw out. Looked like the most expensive part, so I kept it, even though I never found any alternative use for it. I've seen Jerri Ellsworth on youtube build a microwave scanner with it, but that's not something I'd replicate. I remember studying the Egyptian pyramids and noticing things like the Grand Gallery in the main Giza Pyramid having steps, and looking like a a waveguide. If I were to guess the purpose of those things, it would be to do something with radiowaves.

[@jplacido9999]

Not really. It is only to climb to the upper part of the pyramid. I know because I've climbed those and I was not cooked by microwaves....😂😂😂😂

[@Janktzoni]

Well that is somewhat funny: My dad gave me the same caliper about 40 years ago 😄

[@KimJones-xd5bt]

1

[@inseries5494]

you say "whatever" alot and I am mad

[@inseries5494]

you dont know rf basics! whatever!

[@dereksgc]

sucks

[@canalcomentario]

Quanta arrogância da sua parte ou seria somente inveja?🤔. Seria interessante ver o que você produz.