Best frequencies for masers?

[Andrew Thornett]

Can I ask what are the easiest frequencies for amateurs to observe masers?

I know 22 GHz for water masers.

What other frequencies?

When I say easiest, I mean in terms of practicability - ease of obtaining relevant LNB, whether RFI is major problem, etc.

Andy

[Eduard Mol]

Hi Andrew, 

That’s a question I have been trying to answer for a few years. I will try to summarise what I’ve learned about this below…

The OH masers at 1.6 - 1.7 GHz may seem good candidates for “easiest to observe” because their frequency is relatively close to the 1420 MHz hydrogen line. You can use the same SDR, same feed (maybe with some minor tweaks like adjusting the probe length and position), and similar filters & LNAs. No LNBs or downconverters are necessary. 

However, OH masers are not that bright, typically a few hundred Jy at most. From my experience I would say that you need a 3 metre dish for good results. Perhaps it’s possible to detect with a 2 metre or 1.5 metre aperture, but anything less would really be pushing the limits. And there’s often RFI at L-band, as you have probably experienced yourself with your hydrogen line observations. 

Next up are the methanol masers at 6.7 GHz. They’re quite strong, sometimes up to a few thousand Jy so you can detect them with small (1 metre) dishes. Unfortunately they are at a very inconvenient frequency: out of reach of almost all SDRs (even the more expensive options like the HackRF one). As far as I’m aware there also aren’t any readily available options for LNBs that cover this frequency. Dimitry managed to cobble together a downconverter for 6.7GHz from off the shelf parts but it required a fair amount of DIY- you can ask him about the details. 

There is also a methanol maser transition at 12.2 GHz. The 12GHz methanol masers are about 5 times weaker than their 6.7 GHz counterparts. The brightest ones are in the order of 800- 1000 Jy. I have detected two of them with my 1 metre dish, but it’s very challenging. 

On the other hand, 12.2GHz is well within the frequency range of those cheap and widely available sat TV LNBs. Unfortunately radio astronomy at this frequency band is becoming increasingly difficult due to all the RFI from those pesky “muskquitos”.

Of course there are the water masers at 22GHz for which you are building a setup right now. Very bright (up to tens of thousands of Jy) but there is not a lot of good off-the-shelf equipment available for 22GHz. 

There’s plenty of other maser transitions, but those masers are very rare, very weak and/or at mmWave frequencies for which there is very little off-the-shelf equipment available.

Long story short, there is not really a straightforward answer. If you have space for a 3 metre dish, the OH masers at 1.6- 1.7 GHz may be the most practical option. If you are restricted to small apertures, then I think the water masers are still your best option despite the technical challenges. 

Best regards,

Eduard

Op ma 13 jul 2026 om 12:44 schreef Andrew Thornett <andrew....@googlemail.com>

[Andrew Thornett]

Thanks

Sent from Outlook for Android

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From: Eduard Mol <eddiem...@gmail.com>
Sent: Monday, 13 July 2026 17:01:42
To: Andrew Thornett <andrew....@googlemail.com>
Cc: 'Don Latham' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: Best frequencies for masers?