Preparing a Norsat 9000LDF LNB for maser work with 1.2m dish at LRO
Andrew Thornett
Marcus D. Leech
You may find that little horn has too much gain for your dish, significantly under-illuminating it. A 2" horn at 12GHz has a gain around 14-16dBi. A dish in the
Sent from Outlook for Android--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/sara-list/AS8PR06MB81175316786FC31AB97B6E25FFF92%40AS8PR06MB8117.eurprd06.prod.outlook.com.
0.35-0.4 F/D range needs a feed with 9-10dBi gain. I'd try your Norsat LNBF "naked" first and see how it goes.
Andrew Thornett
Sent: Tuesday, 14 July 2026 15:55:16
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Preparing a Norsat 9000LDF LNB for maser work with 1.2m dish at LRO
Marcus D. Leech
Thanks for the advice Marcus - I have attached the horn to a plate.and the horn can slide easily on and off the plate so I can test as you suggest.
ChatGPT suggests I can test the setup by pointing up at 90 degrees to zenith ans comparing this to sigbal at 20 degrees elevation where the amount of atmosphere and henfe water vapour is greater. Is that a good idea? How long do I need to integrate for to perform the test?
Marcus/Eduard/ anyone else - best software options for masers? I have dish mounted on NEQ6 so can track - so should I be using SDR Sharp/IF Average and taking 3 minute integrations and then combining them in Excel over some period of time? How long? Or using different software?
Above - for atmospheric test and also for pointing at masers themselves best methods?
To view this discussion visit https://groups.google.com/d/msgid/sara-list/AS8PR06MB81179E16701030318C6E7ADFFFF92%40AS8PR06MB8117.eurprd06.prod.outlook.com.
Eduard Mol
To view this discussion visit https://groups.google.com/d/msgid/sara-list/d2943614-95c6-4cf1-950c-8eec462388df%40gmail.com.
Andrew Thornett
Thanks Eduard – see capitals below
Andy
From: sara...@googlegroups.com <sara...@googlegroups.com>
On Behalf Of Eduard Mol
Sent: 14 July 2026 20:09
To: sara...@googlegroups.com
Subject: Re: [SARA] Preparing a Norsat 9000LDF LNB for maser work with 1.2m dish at LRO
Hi Andrew,
Great work, good to see the progress on this project!
I made a horn because of two reasons. first of all my dish has a relatively long focal length, so I had to somehow reduce the spillover. Secondly, I did a cold sky/ ground noise test with just the bare waveguide output of the LNB and with a horn in front. The bare waveguide resulted in a much poorer cold sky/ ground noise figure compared to when the horn was attached (I don't remember the exact numbers but it was something like 1.5 dB versus 2.7 dB). I have not measured the radiation pattern, but I guess the bare, open waveguide of the LNB probably has significant sidelobes/ backlobes and is therefore picking up much more thermal radiation from the ground and nearby buildings/ trees.
However, if you have a very deep dish it may still work well, otherwise you could make a shortened version of the horn and see if that works well.
I also made a few horns in different sizes, then measured cold sky/ ground noise and cold sky/ sun noise and stuck with the one that gave me the best results.
I CAN TRY EASILY WITH AND WITHOUT THE HORN TO SEE WHICH WORKS BEST.
Is there a gap between the horn and the LNB waveguide? if so, it may reduce the performance of the horn. Remember the wavelength you're trying to receive is only 13.5 millimetres, so even a gap of a few mm matters!
GOOD POINT – NO GAP – THE PLATE HOLDS THE HORN DOWN ONTO THE PLATE OF THE LNB.
I don't understand what the point is of the measurement comparing 90 degrees with 20 degrees elevation. Yes, you will see more thermal noise from the atmosphere at 20 degrees, but it will depend on the atmospheric humidity, clouds, etc... it's also not that much, when I point my dish to 20 or 30 degrees elevation I usually see an increase in the order of 0.5 - 1 dB. Doing a cold sky/ ground noise measurement just like what you would do with a "regular" L-band telescope is a much more convenient way to quickly check your system performance. Assuming a "typical" sky brightness temperature of around 30 - 40 K at 22GHz when doing your "cold" measurement pointing towards zenith, you can even make a rough estimate of the system temperature.
CHATGPT WAS SUGGESTING THAT CHANGE DUE TO HUMIDITY DIFFERENCES MEANT YOU ARE PICKING UP A DIFFERENCE AT THE SAME WATER MASER FREQUENCY AND THEREFORE DOING A GOOD CHECK OF SYSTEM PERFORMANCE AT THE REQUIRED OBSERVING FREQUENCY – BUT I AM LOOKING FOR ADVICE NOT STATING ANYTHING I BELIEVE TO BE FACT SO THANKS VERY MUCH FOR YOUR THOUGHTS. I GUESS I ASKED THE QUESTION OF CHATGPT IN THE FIRST PLACE BECAUSE WITH OUTHER RT SYSTEMS (E.G. H-LINE) IT IS VERY HELPFUL IF SYSTEM COMPONENTS CAN BE CHECKED WITH SOME SORT OF SIGNAL GENRATOR…..AND SIGNAL GENERATORS AT 22 GHZ ARE NOT READILY AVAILABLE!
As for software I use SDR# with IFaverage, same as with hydrogen line. Because the LO frequency of the norsat LNBs have a tendency to drift over time I usually keep the individual integrations short (1 minute or less) so that the maser lines are not smeared out in each individual recording, and frequency drifting can be compensated afterwards.
To view this discussion visit https://groups.google.com/d/msgid/sara-list/CAFcm1Q4Tmp_ATN_t%2B9LsPrxSszZ%3DsAt6-V%2B-MJjEjr3jbcttTw%40mail.gmail.com.