LNB Offset Testing (sorry, no more free LNBs)

good idea , and with the over-the-air update feature that was proven last fall, this will make it more turn-key user friendly.

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It would be useful, at least to me, to have even a short list of approved/tested LNBs for my own experimentation as well as a spares or local replacement buys considering mine might end up out in blistering heat.

Any standard FTA/universal LNB can work, but the frequency offset needs to be measured. LNBs usually support offset/stability of 1 MHz, which is larger than our carrier bandwidth. Unfortunately, I don’t know of a good way to measure the offset without specialized equipment.

First you need to power the LNB. And then you need to generate a 12 GHz signal (strong harmonics of a lower frequency also work). I guess an RTL-SDR could be used to measure this.

Well, so far any pll LNB worked just fine.
If it can 4K UHD it mostly has a decent enough PLL inside in my experience.

I’m overthinking this. If you don’t mind trial-and-error, then it’s possible to do a manual search by changing the frequency by +/-200 kHz increments.

But @Tysonpower is correct: Most of the newer LNBs should work fine.

I think it is important to note that in version skylark 5.5 in the tuner setup, there are two
options for predefined lnbf
the Maverick1 with a 10.750 GHz LO offset
the Othernet dual band with a two alternative local oscillator frequencies, 9.75 GHz and 10.6 GHz
(note that a the 22khz tone on the feedline to shift to the higher LO)
(thus I think ??? when selecting Othernet dual band it is running at the 10.6 GHz L.O.)

what gets confusing is to try and use custom frequencies or as syed says manual search
if we are given a satellite frequency… what do you enter in the custom frequency setting.

It is not the satellites frequency, but is adjusted for the L.O. differences from the ‘pre-defined lnbf’

what confounds me is how both
Americas 11.90240 - offset 10.600 = 1,302.4 MHz into the dreamcatcher
Europe 11.681242 - offset 10.600 = 1,081.242 MHz into the dreamcatcher

or using the maverick that also works for both
Americas 11.90240 - offset 10.750 = 1,152.4 MHz into the dreamcatcher
Europe 11.681242 - offset 10.750 = 931.242 MHz into the dreamcatcher

You’v stumbled upon a sort of a “easter egg” in Skylark: if you enter a custom freq much below Ku-band, skylark assumes you’v given it the IF output from the LNB. Thats how entering 1.3024 etc works the same as entering 11.90240.

You can enter 11.90240 as well in the custom frequency, in which case Skylark knows this is too high to be IF and adjusts it by the correct LO of the LNB.

Either way is fine. I’d recommend sticking with the Ku-band frequencies, as that means you are not relying on undocumented behaviour. The one scenario where entering the IF is more convenient is if you are using an LNB with a different LO than the official ones.

I think you all are overthinking it. Just use a decent LNB and you will not need any offsets. just enter the frequency of the sat and you are done.

I tested 5 or 6 LNBs and they where all fine. Just get one with PLL / Stable frequency.

@Tysonpower Are you able to use a standard LNB on QO-100?

Of course. Tested all of them on QO100 as well and all where fine. The need to warm up a bit, but then they are fine. But even on a cold start i had no Problem with Othernet getting a lock.

Good point, my cheap lnbf are not all pll locking, but they fit into the boom of my dish (rectangular), some drift with ambient temperature by as much as 400KHz which put’s them out of ‘lock’.

but you are right I am overthinking this… what works is important

@Tysonpower Are you using SDRs for QO-100 or analog radios?

Of course SDRs, for a normal Ham Transreceiver you would need a quite expensive converter from ~1ghz LNB Output to the 2m/70cm band.

Even a normal rtlsdr for 20€ works great.

How expensive are those converters?

well something between 100€ and 500€ or so. But ehy using that when you can have a waterfall with a 20€ rtlsdr :grin:

What rig are you using for uplink, I have not had the $$ or the time for quite a while and I have an older IC-706 from before kids and before they added 70cm to them. I spent a few years playing with the FM sats before they all died and hunting for a cheap 440 ssb rig or kit as the bent pipe sats came back into vogue. I just used an old Alinco DJ580t and a stick and wire DIY Arrow yaggi for the FM sats, my favorite was AO-27. I remember back in AO-40 days someone banging out CW on 440 with an FM HT and using a downconverter to another rig for the downlink.

I use a Pluto SDR for Uplink with a cheap wifi Amp, not soo much power but enough.

Just to be clear, there are some FM Sat’s in the Air. I had QSOs over AO-92, AO-95 as well as SO-50 and that all worked well with a Baofeng handheld (5w) and an Arrow Yagi.

Also build myself an Carbon Arrow Yagi :slight_smile:

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Nice, were you able to get it as a sample? I have an inactive account but used to get all kinds of engineering samples from Analog. Never requested a complete assembly though, but between them and a friend being the regional rep for Atmel though it was like raiding a candy store.

I just bought it when it was released over digikey. Well worth the 100€. Had a lot of fun so far with many different applications and the Pluto.

I was going to make an Al arrow style yaggi years ago but arrows where I can find them are really expensive despite being about the best grade aluminum without paying for aerospace certification same for carbon.
Perhaps now I can find a better deal on carbon composite dowels as I was surprised the low price I got on a carbon wing spar for my kid’s model airplane project.
My poor boy arrow was I think steel fence wire reflectors/parasites and a Cu ground wire(3-4mm?) jpole on a drilled broomstick, I made a bandpass splitter with some caps and coils to send the UHF to the UHF antenna and VHF to VHF.