EME: Earth Moon Earth Communications

[Electro Fan]

eneuro - I'm betting a parabolic dish antenna would be a good choice; it won't work for me because of my neighborhood setting but I think you should pursue it if you can.  It would be great if we could get a few experimenters as well as experienced  advisors and others to give it a go.  We might need some similar but different approaches depending on everyone's interests and requirements. 

[Electro Fan]

First know that EME can be a real time and cash sink. You have to figure out what total budget you want to invest then put 50% into the antenna/rotator/low loss feedline and the rest goes into good low noise preamp and then either a transceiver or separate receiver/transmitter.

Yep, that's one of the key reasons I'm in the Phase 0 (Feasibility Assessment) step.

[Electro Fan]

As you may have surmized, there are a LOT of tradeoffs.  Antenna size scales inversely with operating frequency.  Path loss depends highly (and non-linearly) on operating frequency.  etc. etc.

Roger that - it's all a "link budget" for sure.  Seems like I have to stick with a modest size antenna, which I think may dictate frequency, amp, and LNA considerations.  After the RF section we get to what type of signal is going to ride on the RF.  It's probably an iterative process. I'm open to whatever the good Moon guides here might suggest.  Once I can itemize what the overall system looks like I can see if there is a sufficient "business case".

PS, I've said it before and I'm happy to say it again, and again.  Your teaching videos are fantastic.  It's an honor to receive your advice.  Thanks

[retrolefty]

What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project. 

 Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.

[Electro Fan]

What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project. 

 Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.

Cool, Technician Class is doable (knock on wood) 

Now we're down to finding an antenna that blends in with the neighborhood, the rest of the configuration, and the budget 

[w2aew]

What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project. 

 Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.

Actually, full legal limit for VHF and above is 1500Wpep, and all possible for a Tech licensee in the U.S. 

[Alex Eisenhut]

You can learn a lot by going to the penultimate Australian EME website of VK3UM...

Why would you rate his site the second to last?

[VK5RC]

You lucky buggers,  we get 400W max and if eirp over a certain amount we have to do and keep copies of safety calculations!  Nice calculator on vk3um website.
EF re the license,  I don't think it will be difficult, gee I passed! HiHi.
If you can find a local ham club,  they do the exam usually and can be a great resource for gear and know how.

[Electro Fan]

Ok, after reflecting (no pun intended for this EME project) on the replies posted here it seems like the initial article I tripped across might have been reasonably on the mark:

http://www.k4lrg.org/Projects/K4MSG_EME/

The design calls for:

144 MHz SSB (this falls in the realm of 2 Meters?)

recommends a high stability reference oscillator (something I've been thinking about for another project); I think to be an EEVer you have to be at least a little project hungry

Yagi antenna (14.5' boom is pushing it on my aesthetics constraint but maybe it can be set up and taken down reasonably easily on a tripod)

Power Amp (150 watts?), preamp/LNA, and power supply designed to be somewhat portable/temporary

Transceiver (suggested Icom IC-706MkIIG)

What I'm still not clear about with this design is whether K4MSG has been able to hear his own signal comeback from the Moon or whether this design requires him to receive "QSOs" from other listeners around the world.  He does point out that "when you are running a single-Yagi, low-power station for EME you cannot expect to successfully achieve two-way communications via the Moon except under the best of conditions."  Perhaps with a bit more resource thrown at the design it might be possible to send and receive your own transmission?

If anyone has any comments on how to enhance/improve K4MSG's design I'm open to suggestions - but it looks like a pretty good starting point. 

Still not sure about exactly what the preferred signal type is to try to bounce off the Moon in order to be able to clearly confirm it was a specific signal that hit the Moon and came home...  Maybe tones of some type?

This seems like a pretty definitive type of signal:
http://www.vk3um.com/1296_CW_Feb06.wav

[djacobow]

Ah, John and Martha King. I did not know they did ham training classes. They are very well known in the pilot community for their pilot training videos. I think I sat through 12 hours of them on VHS once for my private certificate. They are so thorough and boring, that you just want them to go faster. :-)

The mounts for the radar antenna that was used are still in the ground outside of the building.  Cool stuff!

Even in this ARRL Amateur Radio Technician Class Training Course they mentioned EME communication at UHF/VHF and said something about Yagi antenas and... parabolic dishes.

Why parabolic dish is in my interest-that is simple-during the day use it for solar thermal in CSP, but at night if it could be used for radio communication it could be even more fun, so trying to estimate if 3m-5m parabolic dish could be usable for EME? 

[TSL]

You can learn a lot by going to the penultimate Australian EME website of VK3UM...

Why would you rate his site the second to last?

My bad use of an adjective, should have been "ultimate"

regards

Tim

[VK5RC]

Be a bit careful with a IC706 as an IF rig prior to other gear eg transverters,  it's a great general rig (i own one)  but it uses - ve feedback for power control,  so it can give a spike at higher power before settling.  For transverter use the yaesu ft817 is popular.

[AG6QR]

You lucky buggers,  we get 400W max and if eirp over a certain amount we have to do and keep copies of safety calculations!  Nice calculator on vk3um website.
EF re the license,  I don't think it will be difficult, gee I passed! HiHi.
If you can find a local ham club,  they do the exam usually and can be a great resource for gear and know how.

Yes, the US exam for a technician is not difficult.

My local club has a 10-year-old who has held his technician license since he was 8.  He's about to be joined by another 10 year old who will be taking the test shortly.  Based on my conversations with second kid, I'm very confident he's going to pass.  Yes, both of these kids are bright, but I think most 10-year-olds are bright enough to get a license if they want to.  Most of them take harder tests in school already.  The thing that's most unusual about these kids is that they have the motivation and interest to study for this test.  Of course they have parents who are hams, too.

It does bother me somewhat that an eight year old has the legal authorization to go beaming a kilowatt and a half of RF energy around.  That seems crazy.  But that's the way the rules are written here.  In the particular cases I know, mom and dad limit kids to 5w handhelds, or occasional 50 watt mobile, and the kids are very well supervised.

[AG6QR]

I'm pretty sure the delay from Earth to Moon and back has to be at least a couple seconds.  In standard Geosynchronous satellite communications the delay up to a satellite and back down is about 270 milliseconds and GeoSats are only about a tenth of the way to the Moon.  Even so with a 2-3 second delay it would seem tricky to be continuously transmitting on one frequency and then trying to tune to another frequency to catch an iffy transmission.   Maybe this would require one transceiver or transmitter for send and another transceiver or receiver for monitoring/receiving?

Yeah, the delay is around 2.5 seconds, or thereabouts.  It's roughly a 384,000 km,  * 2 for a round trip, or 768,000 km round trip, divided by the speed of light, 300,000 km/s.

When working a manmade satellite, the uplink frequency is deliberately separated from the downlink frequency.  But for EME, the frequency doesn't change as you bounce a signal off the moon, except for a slight change due to doppler effect.  But the doppler effect isn't large, because the distances aren't changing rapidly.  It's hard to make a receiver selective and sensitive enough to receive well when it has a nearby powerful transmitter transmitting at very nearly the same frequency it's trying to listen to.  So simultaneous transmission and reception of moonbounce at one site using one antenna is pretty much out of the question.  But you don't need to do simultaneous transmission and reception to hear your own signal.  If you transmit for two and a half seconds or less, you can listen to your echo come back.  If you transmit for longer, you'll hear the last two and a half seconds of your transmission.

For making longer transmissions, yeah, it's easier if the transmitter and receiver are far enough apart that the receiver doesn't hear the transmitted signal directly, but only hears it via moon bounce.

[Electro Fan]

I'm pretty sure the delay from Earth to Moon and back has to be at least a couple seconds.  In standard Geosynchronous satellite communications the delay up to a satellite and back down is about 270 milliseconds and GeoSats are only about a tenth of the way to the Moon.  Even so with a 2-3 second delay it would seem tricky to be continuously transmitting on one frequency and then trying to tune to another frequency to catch an iffy transmission.   Maybe this would require one transceiver or transmitter for send and another transceiver or receiver for monitoring/receiving?

Yeah, the delay is around 2.5 seconds, or thereabouts.  It's roughly a 384,000 km,  * 2 for a round trip, or 768,000 km round trip, divided by the speed of light, 300,000 km/s.

When working a manmade satellite, the uplink frequency is deliberately separated from the downlink frequency.  But for EME, the frequency doesn't change as you bounce a signal off the moon, except for a slight change due to doppler effect.  But the doppler effect isn't large, because the distances aren't changing rapidly.  It's hard to make a receiver selective and sensitive enough to receive well when it has a nearby powerful transmitter transmitting at very nearly the same frequency it's trying to listen to.  So simultaneous transmission and reception of moonbounce at one site using one antenna is pretty much out of the question.  But you don't need to do simultaneous transmission and reception to hear your own signal.  If you transmit for two and a half seconds or less, you can listen to your echo come back.  If you transmit for longer, you'll hear the last two and a half seconds of your transmission.

For making longer transmissions, yeah, it's easier if the transmitter and receiver are far enough apart that the receiver doesn't hear the transmitted signal directly, but only hears it via moon bounce.

Excellent - this is what I was looking for, now I just need to understand it

Seriously, what I think you pointed out was:

1) Unlike a manmade satellite that has a transponder receiver and a transponder transmitter which operate on different frequencies EME is just passively bouncing the signal off the Moon so there is no frequency change. 
2) But further to your point it's hard to make the receiver selective and sensitive enough to receive well when the system is transmitting at the same or nearly the same frequency (given the modest Doppler effect that occurs in a very short period).

So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back?  If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval?  Does this mean that signals are limited to the 2.5 second duration?  (I thought I heard a longer signal message in this:  http://www.vk3um.com/1296_CW_Feb06.wav ?  Maybe there is something fundamentally different going on here?)

On a different topic, what are the tradeoffs between VHF/UHF and HF for EME?  Looks like WSJIT-X uses JT9 for HF and gives 2dB more sensitivity with only 10% of the bandwidth of JT65A.  What is the practical advantage of using less bandwidth - less likely to hit interference, or something else? 

Or is there an advantage to using JT65 with VHF/UHF?  (Smaller antenna?)

Then there's WSJT-X "bi-lingual mode" that supports JT65 and JT9 - maybe this is the winner (and the frequency decision is a separate decision)?

Thanks, EF

[G7PSK]

How about a rope yagi, you put it up when you want it then take it down afterwards, If your negbours complain tell them its a washing line.
http://www.bigskyspaces.com/w7gj/longyagi.htm

[eneuro]

The problem of dual use parabolic dishes is in swapping the hardware out of the focal point,  not an insoluble problem though.  The dish surface obviously needs to be both rf and light reflective.

Dish and feed for 1296 MHz (23cm) from this link http://www.ok1dfc.com/peditions/ymk2012/dl1ymk2012.htm

Probably it is smaller than 3m, however I'd like make my parabolic dishes for CSP using fiberglass mold and glue inside hundreds of triangle mirrors, so unsure if small gapes between mirrors will affect somehow reflection of those 23cm/70cm radio waves 
Something like this below comes from my CAE and ~15cm mirror triangles were entered there and system divided whole 3m dish to cover it automatically, so now it is possible output CNC G-code to cut needed mirrors and also output STL 3D dish geometry to make molds needed for fiber glass.


Those 15cm triangles will be of course good for solar thermal CSP, but I have no idea what happends when I will try reflect 432Mhz (70cm) or 1296 MHz (23cm) radio waves-maybe it could work with 10GHz (3cm).
If this surface were solid probably it could work, however more knowledge needed how those "umbrella" dishes for EME are made-some kind of netting like for satelite transparent dishes to let them operate at stronger winds regardless of huge diameter disk?

[Howardlong]

Those 15cm triangles will be of course good for solar thermal CSP, but I have no idea what happends when I will try reflect 432Mhz (70cm) or 1296 MHz (23cm) radio waves-maybe it could work with 10GHz (3cm).
If this surface were solid probably it could work, however more knowledge needed how those "umbrella" dishes for EME are made-some kind of netting like for satelite transparent dishes to let them operate at stronger winds regardless of huge diameter disk?

I have some experience on making dishes for 23cm and 13cm (1296 and 2300/2400MHz) but this was 15 years ago,during the days of the AO-40 satellite which was in an elliptical orbit with apogee at about 60,000km (to give you an idea of what's achievable, you could hear and just about decode the FEC telemetry at apogee with either a simple monopole or a patch antenna at 2.4GHz).

There are a number of mechanical engineering issues, mostly to do with weight and wind load. You can make a reasonably good parabola by stressing spars much like an umbrella, however it should be noted that to keep the shape reasonably parabolic, you may need to have a fairly shallow dish, so that will affect the f/D can making the feed point distance quite long, meaning you need to take care with the feed to illuminate the dish sufficiently. Over-illumination means you're going to receive ground noise from behind the dish. Under-illumination means you're wasting some of that valuable antenna real estate. For transmit, a -10dB taper at the edges is a reasonable rule of thumb but for receive -20dB might be more appropriate to reject ground noise. This is one of the few times where antenna reciprocity doesn't always work!

The general synopsis is that you're aiming for aberrations away from a parabola of less than lambda/10, and the same applies to the use of any mesh used for the reflector. Small aperture (~1cm) chicken wire works, but it's surprisingly heavy, however it does reduce wind load to some degree. Aluminium fine mesh is light weight but the fluid dynamics means that wind load will be high, almost as bad as a solid dish. There is a school of thought which says that mesh lets in noise from behind the dish, I don't know if that's the case, I am sure that someone will have some info on that.

You will also need to consider how to mount and move the dish mechanically.

[VK5RC]

I used a 3m diameter satelite dish , which comes with reasonable ability for azimuth movement, and a bit of bodging made for elevation control. I used two satellite actuators. The dish mount (it is mobile! as I have to use it in my driveway!) is a modified engine support/frame with extension spars.
I have generally found one of the easiest and best methods is to find a popular (i.e. cheap) product and modify it for your needs. Building something from scratch will cost a lot more in dollars and time.

[Theboel]

This is my 2 cent opinion,

I belive 2m band (144Mhz) is good start point why :
1. the size of antena is "manageable"
2. the cost for accesories (LNA, down converter, Antenna switch, PA) is fair enough
3. The activity is among the EME enthusiats is good
I will not suggest to try EME with a wet string type station but many-many report with 12 element single yagis can made some 2 way contact and if You can not transmit cause You do not have licence maybe You can contact some "big gun station" like W5UN, DG9MAQ (germany), VK3GY(Australia) and many more to made schedule to try to listen to them.
if I start again from zero my EME station here list I like to have (remember this is a list for 2 way contact)
1. Decent HF transceiver like TS850, FT950, etc
2. Down converter (antenna mount style with LNA)
3. Low loss cable like heliax LDF5
4. 1Kw Solidstate PA
5. Antena switch relay with sequencer
6. 2 X 12 Element optimized yagis (K1FO etc or You can buy from cushcraft, M12 etc)
7. PC for sofware logging, Moon Position, cluster monitor)
seem many thing but honestly in my Country with almost 300 milion people there is no more than handfull people can hear their sound whats like after travel 600,000km away.

[Dragon88]

A couple random points:

I agree that 2M is the way to go. The 2M band is very straightforward for new hams, and the antenna sizes are reasonable. Also, you can use your radio to talk on local repeaters and such, which is important for building all of your other ham skills and knowledge.

To study for the exam, I highly recommend buying The ARRL Ham Radio License Manual. It's currently listed at $27 on Amazon. Yes you can study for and get the license without buying any book. Heck, they post the entire question bank with answers online to study from. However, to me the tech exam is not just about getting your license, but also learning. The ARRL license manual does a great job of teaching many important concepts.

[LaserSteve]

Ok, if you wish to do EME, you should start by subscribing to this list and listening about two weeks before you post. You need to do that to understand the culture of the list.

The LIST is HIGHLY MODERATED, moderated to a level that most EEV users would never stand for. And it is moderated that way for good reason due to the high  level of technical discussion that occurs.  Beginners are welcome, but it is NOT a general ham radio chat, its VHF and above, and a few seti and satellite monitoring guys also  post. Non-hams just looking for entertainment  would generally be asked to be "monitor only". All posts are highly moderated, and off topic stuff just vanishes. Wasting the moderators time is well, probably highly to very  fatal to your list access.

 To give you an idea of the level of sophistication, when these guys have a conference, Rhode and Schwartz or Agilent usually send two sales guys and a few 100,000$ instruments on loan for noise figure measurement.

You can see anything from the best waterproofing for an outdoor connector to subtle errors being found in Y-Factor noise measurement papers.  Some of these folks build systems at 78 to 120 Ghz and go mountain-topping with them. Others consider wire bonders in the basement a minimum level of tooling. Others just go out with two modified radar detectors and have some short range fun. :-)

http://lists.eclectechs.com/cgi-bin/mailman/listinfo/microwave

The archives are golden.

The list would help you find a EME capable ham near you...

Steve

[Howardlong]

Regarding the exams, the technical side really is pretty simple for your average EE, just do a bit of brushing up using example papers and you should be sweet. Not so easy are the regulations, and you need to know them, and unlike the technical side they're pretty much a memorising thing regrettably. Personally, with those sorts of things I find it easiest to read a text on the subject and then do a couple of dozen example test questions, referring back to the text when I'm unsure. Reiterate the test until you're achieving 100% (or whatever your target is). While it may seem like a chore, most hams are fiercely defensive of their bands and take pride that they have gone through a couple of hoops to gain the right to use them.

There are a few non-hams who don't seem to think it's necessary to go through those hoops, and enjoy their lives indulging in spectrum abuse. As a ham myself, I find it a little irksome as the exams are not exactly hard, I did them when I was 16, passed the technical side with distinction, and got a credit on the regulations. This was on the full exam, not the introductory levels we have now, so if a 16 yo can do that, it can't be that difficult!

There are a few things that you may find irrelevant, in particular HF propagation. I think if I had to take the exams again I'd not do well in that section as I've only transmitted on HF about half a dozen times! Almost everything I do is at VHF and above.

[AG6QR]

So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back?  If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval?  Does this mean that signals are limited to the 2.5 second duration?  (I thought I heard a longer signal message in this:  http://www.vk3um.com/1296_CW_Feb06.wav ?  Maybe there is something fundamentally different going on here?)

That's a nice recording, and it illustrates the concept well.  The high pitched clear sounds, at low volume, are the transmitted morse code.  The lower pitched sounds with a little bit of noise behind them are the received code. He transmits a couple of letters, and then waits to hear them come back.  Note the pitch changes, probably due to doppler.  The echo comes back about two and a half seconds after the original transmission, according to my wristwatch.

Notice he can't send his entire call sign in one go.  He breaks it up into chunks of a couple of letters at a time.

[Electro Fan]

So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back?  If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval?  Does this mean that signals are limited to the 2.5 second duration?  (I thought I heard a longer signal message in this:  http://www.vk3um.com/1296_CW_Feb06.wav ?  Maybe there is something fundamentally different going on here?)

That's a nice recording, and it illustrates the concept well.  The high pitched clear sounds, at low volume, are the transmitted morse code.  The lower pitched sounds with a little bit of noise behind them are the received code. He transmits a couple of letters, and then waits to hear them come back.  Note the pitch changes, probably due to doppler.  The echo comes back about two and a half seconds after the original transmission, according to my wristwatch.

Notice he can't send his entire call sign in one go.  He breaks it up into chunks of a couple of letters at a time.

Yes, it is simple and clear but when you think about what's involved and what is happening it's very inspiring!  So just to confirm, even this example is one in which the transmission duration doesn't / can't exceed the round trip propagation time (about 2.5 seconds) - otherwise the outgoing signal would be stomping on the incoming signal, correct?

So - it does seem possible for an EME transmitter to receive his own signal without hoping that someone else hears it and reports it, correct?

If the answer to both is yes, this would be the functionality I'd like to duplicate.    The objective is getting clear, so it's now down to the design and determining if it's feasible to get from here to there, literally and figuratively.