A search on here throws up a few mentions of using EME on a SOTA activation. Historically, it was considered you needed a lot of power and multiple, long Yagis to make it work. More recently QSOs have been completed with powers as low as 25W. These have been achieved by all the “heavy lifting” being done by one station in the QSO which can receive the weak station and transmit with sufficient power to be heard by the low power station.

So I thought I would give it a go today from my home QTH. Equipment was a Diamond 10 el 70cm Yagi, IC-705 and MS Surface Go 2 tablet.

I wasn’t expecting much but after a while I managed to decode a CQ from Frank NC1I!

The mode was Q65-60B.

The attempted QSO was coordinated on HB9Q’s EME logger site:

Frank thinks if I can up my power to 50W a QSO might be on the cards. I think I may look at a better antenna first, if only to put off the expense of an amp or new radio - I would love an IC-9700 but they are not cheap.

Today’s little experiment showed that with a SOTA portable rig it is at least possible to receive an EME signal. The challenge is replying!

There is a lot to learn, even if I do upgrade my equipment. The moon was quite high in the sky today at about 30° and EME is supposed to be better if it is nearer the horizon. There is also a thing called EME Degradation which takes into account, as I understand it, several factors including how noisy the sky is. For example if the moon is in front of the Milky Way it isn’t good due to radio noise from our galaxy. Conditions today for EME Deg were rated only as “Fair”.

So I haven’t cracked SOTA EME but I think it can be done, as @K7ATN and others described on this thread. The trick will be doing it with the minimum of equipment, 50W and a better antenna may just be enough. :slight_smile:


Good effort :slight_smile:

Instead of upping the transmit power , you could increase the beam size, which would help a bit on receive too. I have a 17ele for 70cm that is eminently portable (for easy walk in summits). Perhaps someone in a local club has one that can be borrowed.

The issue would be balancing the mounting for elevation. If the moon were close to the horizon then this wouldn’t be a problem. Being on a summit would also mean that there would be less likely to be any obstructions between you and the moon, even if it were on the horizon.

Good luck with future attempts.


I agree the first step is a better antenna. The Diamond 10 element I have works but it’s hard not to describe it as anything but a “cheapie”. They make a 15 element version which is less than £70 and I guess I could carry two of those up a summit.

But I suspect there are other options. :slight_smile:

Suggestions welcome!

1 Like

And they’re a bit of a pig to carry up a summit (although I take mine sometimes).
An alternative option would be your IC-705 and a portable amplifier.

Good luck, look forward to the updates.


That antenna is a very, very old design. Which is a polite way of saying very heavy and very low gain. You should be able to make something which will easily out perform it for not much effort that is the same size. Or make something bigger that seriously outperforms it. Then you wont need so much uplink power to complete your 1st EME QSO.

Go and look at the designs on Martin’s page at DK7ZB Yagi - Homepage


You’re right of course. Something built around a fibre tube could be much better and lighter but they do have to made accurately I think.

You should be able to make the parts with hand tools. A pillar drill is a big help. If you are talking 2m or 70cms then errors of mm don’t make that much difference. 23cms is more critical.

1 Like

Or a very old idea - a rope-boom roll-up yagi. I think most of the published designs were for 2 mtrs, including a Brendan Trophy attempt between VO1 & EI, but no reason it could not be adapted to 70 cm.


Martin’s 28 Ohms designs are perfect for a common SOTA station - maximum forward gain on a short boom.
For EME you rather want a clean pattern, i.e. a low noise antenna. I’d recommend DG7YBN. His site is interesting to read and somewhat encouraging if you want to try low-power EME.



What 17el portable 70cm antenna is that?

Tom, N2YTF

Thinking outside the box a little, I remember years ago a ham in, I think, New Zealand, having success using a rhombic antenna aimed at the part of the horizon where moonrise took place. A wire antenna would be inexpensive but needs space and the trade off is that the moon would be in the window for a limited time.

To be honest i couldnt tell you the make as its a shared resource with my friend M1BZJ (well its his but lives in my garage).

It has a partner in a 9 element tonna for 2m so i assume it maybe a tonna beam. It splits into 2 or maybe 3 sections and isnt that heavy.

I wouldnt reccomend it for harder summits and positioning the thing on a backpack so as not to get skewered in the head is fun :slight_smile:




In the mid 70’s Alex GD6IA (alias GM(D)3UMW) - on a visit to his GD QTH (he had not long moved from GM and an ex Member of WoSARS) a farm cottage outside Peel, along with the usual stacked & bayed 2M yagi array, he had a phased 2el 2M rhombic in a field adjacent to his cottage (on supports about 2.5M off the ground). The rhombic took up the whole length of the field. The field I reckoned was about 4 acres? The rhombic was centred on GM.

Running a wee bit of ‘welly’ at each end, I had nightly skeds with him from my parents QTH in the East End of Glasgow. Likewise Graham GM8FFX in Aberdeen. The only problem I had was Graham was off the back of my array. Alex had to QSP - hi!

Interesting times.


1 Like

Ray VK3ATN (SK) of Birchip had a 4 wire stacked Rhombic Array. I saw it in about 1970 a decade after his first EME QSOs. He used the legal limit of 150 W DC input, CW (of course). The band used was 2 m. The supporting towers were circa 50 ft high as the array crossed a public road and the council mandated a lot of clearance. He owned property on both sides of the road. It was as large as some HF Rhombics. Maybe 100 wavelength per side.

There is no way it could be made portable even with several trucks.

Ray was the first VK EME operator.



My 2022 SOTA EME Station consisted of a Cushcraft A719B 19 Element 70cm Yagi (15.5dBd 13.75 feet in three sections), a speaker tripod, 100W KLM amplifier, a FT-857d w/ TXCO, Signalink, and a ARR preamp and laptop. Power was provided by a 12Ah LiFePO4 battery for the transceiver, and a 32Ah LiFePO4 plus a voltage stabilizer to power the amplifier. Altogether it was about 32kg and quite unwieldy but I could carry it short distances.

I made the following SOTA activation QSOs with this station:
K7ATN on W7W/LC-164 (Prune Hill), 06 Mar 2022
17:30 DL9KR 70cm CW EME: JO40-CN85
18:18 PA2V 70cm DATA EME: JO22-CN85
18:46 NC1I 70cm DATA EME: FN32-CN85
K7ATN on W7O/WV-099 (Cooper Mountain), 10 Feb 2022
22:02 NC1I 70cm DATA EME: FN32-CN85
K7ATN on W7O/NC-051 (Bald Peak), 14 Jan 2022
22:30 HB9Q 70cm DATA EME: JN47-CN85
22:51 NC1I 70cm DATA EME: FN32-CN85
23:34 PA5Y 70cm DATA EME: JO21-CN85
73, Etienne-K7ATN


I found an interesting article from Chris VK5MC at detailing his EME Rhombic.

Sure, it is too big for SOTA but given the advancement in digital modes for EME, such a huge antenna may no longer be required.


I’m thinking KL7R might do an attempt. He was the first activator in Alaska, and he used the FO29 satellite for that.

Elliott, K6EL

Hi Peter, thanks for putting up that link, a great read.

cheers, Geoff vk3sq

1 Like

Reading that document was a fantastic way to start the morning, thanks Peter.


In 2011 a team of Vk3KH, Vk3xpd, Vk4uh and Vk1da activated 2m eme from Norfolk Island using a 19 el yagi built by Vk7mo and a 300w amplifier by TE systems.

Signal levels were not high. A large array at the other end and 1kw+ made a signal that was about -15db s/n at our end.

In my view dreaming of doing eme using SOTA gear is just that - a dream.

Andrew vk1da