EME: Earth Moon Earth Communications

[Mr Simpleton]

To get started I would choose 144 MHz... the antennas are not that big and cable losses are fairly low, plus the stuff you buy are fairly cheap.
Now, EME usually means there are two stations involved... i.e. the bigger set up on one side means you can reduce it on the other side. It all comes down to path loss. When they run this w/o computer a basic station for 144 MHz (2meter) would be 1kW output power and 20 dB antenna gain. This would allow you to hear your own echos off the moon. Now some do have a "Slightly Large Array" which means you can hear them off the moon using just a single yagi with 13 dB gain and hear the signal in your receiver. Contacting W5UN should be a walk in the park, and have a look at his antenna: http://www.w5un.net/EME%20Array.JPG


Contacting KP4AO Arecibo station should be even easier:

Using JT65 means you have some excotic coding and sophisticated processing to pick up the signal, and allows for very weak signals to be decoded. Ultimately this allows you to down size the station, 14-16 dB antenna gain, and 200 watt o/p may give you 2-way contact.

BTW I have heard the big guns calling on CW using a single yagi and a normal receiver with-out a LNA... guess I was a bit lucky.
Making a random 2-way contact over the moon, now its getting a bit more complicated

[eneuro]

Contacting W5UN should be a walk in the park, and have a look at his antenna: http://www.w5un.net/EME%20Array.JPG

Nity concept with roling whole construction along ring path ucing classic aka vehicle wheels

The same way decent side dish can be rotated around vertical axis... with all equipment, but longer distance might be needed between front and rare wheels, since dish can have significant stronger air drag, but in the case of strong winds it can move automaticaly with wind direction itself and all we have to do is protect center of this circle to prevent damage, but it can be done quite cheap with decent amount of concrete, so not such a big deal 

[Electro Fan]

I get that if one station has a relatively bigger antenna the other station can have a smaller antenna. 

I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon.  I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.

Guess I need to start building a link budget with specifics.  If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see.  Thx

[AG6QR]

I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon.  I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.

Note that a JT65 transmission is 46.8 seconds long, so you're not going to hear the entire transmission echo off the moon.  It's a highly structured protocol.  Part of the reason the transmissions are somewhat long is to be able to pull signals out of the noise.  A detailed explanation is here:

http://www.arrl.org/files/file/18JT65.pdf

Also notice from that paper that a JT65 exchange with another station is essentially self-documenting, and the audio .wav files are saved.  Some operators may trade their .wav files via e-mail as a form of QSL after the QSO.  It's not quite the same thing as hearing your own voice echo off the moon a couple of seconds after you speak, but it is a form of hearing your own transmission, as received by another station, after it made the round trip to the moon.

Anyway, JT65 is a way to make EME contacts with more modest equipment than would be required for voice or CW.

[Electro Fan]

I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon.  I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.

Note that a JT65 transmission is 46.8 seconds long, so you're not going to hear the entire transmission echo off the moon.  It's a highly structured protocol.  Part of the reason the transmissions are somewhat long is to be able to pull signals out of the noise.  A detailed explanation is here:

http://www.arrl.org/files/file/18JT65.pdf

Also notice from that paper that a JT65 exchange with another station is essentially self-documenting, and the audio .wav files are saved.  Some operators may trade their .wav files via e-mail as a form of QSL after the QSO.  It's not quite the same thing as hearing your own voice echo off the moon a couple of seconds after you speak, but it is a form of hearing your own transmission, as received by another station, after it made the round trip to the moon.

Anyway, JT65 is a way to make EME contacts with more modest equipment than would be required for voice or CW.

Thanks for the link - I'll read it but..... Question:  JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period?  (Can JT65 add value for shorter transmissions, such as 2 seconds?)

[AG6QR]

Thanks for the link - I'll read it but..... Question:  JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period?  (Can JT65 add value for shorter transmissions, such as 2 seconds?)

The minimum, maximum, and only length of a JT65 transmission is 46.8 seconds.  An exchange (QSO) via JT65 involves several back-and-forth 46.8 second transmissions by the two stations involved.  You can't just send a couple seconds of JT65.

[TSL]

Guess I need to start building a link budget with specifics.  If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see.  Thx

The best link budget calculator is from Doug VK3UM here...

http://www.vk3um.com/eme%20calculator.html

This screen shot enclosed is from a recent experiment where NASA were lighting up the moon with their ranging RADAR and some of us in Australia were trying to receive it.

As you can see you can calculate everything that might effect your link budget.

regards

Tim

[Electro Fan]

Thanks for the link - I'll read it but..... Question:  JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period?  (Can JT65 add value for shorter transmissions, such as 2 seconds?)

The minimum, maximum, and only length of a JT65 transmission is 46.8 seconds.  An exchange (QSO) via JT65 involves several back-and-forth 46.8 second transmissions by the two stations involved.  You can't just send a couple seconds of JT65.

Roger that,  Thanks

[Electro Fan]

Guess I need to start building a link budget with specifics.  If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see.  Thx

The best link budget calculator is from Doug VK3UM here...

http://www.vk3um.com/eme%20calculator.html

This screen shot enclosed is from a recent experiment where NASA were lighting up the moon with their ranging RADAR and some of us in Australia were trying to receive it.

As you can see you can calculate everything that might effect your link budget.

regards

Tim

Wow, on a scale of 1 to 10 this looks like about a 12  ; after looking at it further maybe a 15
- I'm used to seeing link budget calculators in spreadsheets, and I've never seen a link budget with Planet Path loss and Delay, or a Background Sky Temperature Map, not to mention the integrated antenna database.... This think must have been a labor of love.

I've got the home tab all filled in - the rest looks like it will cause a fair amount of research and learning 
Thanks!

[Electro Fan]

a little off topic but looks like Beethoven has been to the Moon
http://www.katiepaterson.org/eme/

[Electro Fan]

Ok, an update on my quest to figure out what the smallest direct up and down EME system configuration might be.

I was hoping a single yagi might possibly do it but I think the answer is "not even close", ie, 4 yagis appear unlikely to get the job done, and probably something in the vicinity of 8-16 yagis would be required - which would freak out my neighbors, I'm sure.

I came across some very good posts by VE2ZAZ. 

System Overview (excellent video)


Project Log
http://ve2zaz.net/EME_Log/EME_Log.htm

Project Overview
http://ve2zaz.net/3.2m_Dish/3.2m_Dish.htm

VE2ZAZ's take is this:

A single yagi will always be very borderline, no matter what you do or how much power you put into it. A single long boom yagi will have you going on digital modes with the largest stations, but it will not really cut it on CW. Even 4 yagis like mine are a small setup. Do not expect to hear (or see) yourself with 4 yagis. 8 or 16 yagis will make this happen, but this is a large array! This is why I went to 1296 and a 3.2m dish on the ground. With 100W at the feed, I could see and hear myself under good moon conditions. But I never saw my own signal on 432 with my four 13-element yagis and 300W. My four yagis allowed to work CW with larger stations and JT65 with many.

A very low noise preamplifier right at the antenna will always be the single most important thing to have (except on 6m, where to level of ambient noise is high).

But you will not be able to really compensate for too small antenna(s). On TX, you can go KiloWatt, but that will not improve your RX. Even the best preamp will not help if there is too little energy picked up by the antenna...

So, assuming you want to work/with other stations it looks like the entry level for EME can be a single Yagi similar to what K4MSG built:
http://www.k4lrg.org/Projects/K4MSG_EME/

But to go straight up and down (to hear or see your own signal without relying on other stations) requires more antenna resource, something along the lines of what VE2ZAZ built.

PS, I'm not saying all this is 100% iron clad and there aren't other answers, configurations, and solutions - but I think K4MSG and VE2ZAZ have pushed hard on what can be done with physics, technology, budget, and ingenuity and so far these are the best data points I've found.  Happy to hear other ideas.

[w2aew]

It all comes down to tradeoffs.  At 144MHz, path loss is a tad more than 250dB typically; at 432 the loss is more like 260dB, and at 1296MHz it is more like 270dB.  So, you need more antenna gain (and power) as you move up in frequency.  The good thing is that antennas are proportionally smaller as the frequency goes up for a given amount of gain, so it's "easier" to have higher gain antennas in a given physical space when operating at the higher frequencies.

Here are some references that I got from a colleague - some of which have probably been referenced earlier in the thread:
http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf
http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf
http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf
http://www.qsl.net/n1bwt/chap6-2.pdf
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf

[Marco]

I'm not a HAM but a while back I looked at crystal filters ... and I found this hear say account of someone doing it with 4 Yagi's and 500 Watt (with a 20 Hz bandwidth).

[Electro Fan]

It all comes down to tradeoffs.  At 144MHz, path loss is a tad more than 250dB typically; at 432 the loss is more like 260dB, and at 1296MHz it is more like 270dB.  So, you need more antenna gain (and power) as you move up in frequency.  The good thing is that antennas are proportionally smaller as the frequency goes up for a given amount of gain, so it's "easier" to have higher gain antennas in a given physical space when operating at the higher frequencies.

Here are some references that I got from a colleague - some of which have probably been referenced earlier in the thread:
http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf
http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf
http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf
http://www.qsl.net/n1bwt/chap6-2.pdf
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf

Thanks.  The challenge with going up in frequency is that while it brings shorter wavelengths and therefore potentially a smaller antenna is that the electronics and ancillary equipment are likely to go up in price, I think - but it's worth looking into. 

One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations

[Electro Fan]

I'm not a HAM but a while back I looked at crystal filters ... and I found this hear say account of someone doing it with 4 Yagi's and 500 Watt (with a 20 Hz bandwidth).

Thanks, this is a cool article and it does seem to indicate that with 4 yagis the system described goes "up and down" without a need to go "across" for help from another station.  This is why I put my disclaimer about my findings not being 100% iron clad.  It's not too hard to envision something that sits in the gaps between these first couple benchmark systems (excellent as they are), but even at 4 yagis unfortunately it doesn't address the original objective which is to get the size down to 1 manageable yagi (that could be somewhat temporary/portable) in an effort to meet the neighborhood aesthetics constraint.  This project is making the suburbs look disadvantageous to rural settings....  And I'm sure people in rural settings could come up with some other good reasons to live farther from cities beyond just the ability to do some Moonbouncing

[C]

A different Idea

For receive,
have you looked at combining an active antenna with a traveling wave amplifier.

The electronics of an active antenna allows a large range of input impedance so you could have many taps on one dipole. There would be a signal time difference between taps.

The traveling wave amplifier or Distributed amplifier uses a time difference to build the signal.
http://en.wikipedia.org/wiki/Distributed_amplifier
Add in the active antenna preamp in where the gates are in the figure or use dual gate transistors.

You could also use a Distributed amplifier to add many dipoles.

In place of the many dipoles, I think it would work with a long wire( a pipe ).

Will it work, No idea
C

[Howardlong]

Path loss is also proportional to the square of the frequency, so it's swings and roundabouts.

Think of it more in terms of antenna aperture size. The more metal you have in the air, irrespective of frequency, the louder the signal will be.

Higher frequencies means it's also harder to accurately align your antenna because the beamwidth is narrower for the same antenna area. Receiver noise figures also tend to increase as you go up in frequency, although these days even at 10GHz you can achieve sub 0.5dB noise figures reasonably easily.

I remember trying to pick up a satellite in near Molniya orbit about 15 years ago on K band with a 60cm dish, giving about a 1.5 degree beamwidth. Picking it up and tracking by hand was very hard!

[Electro Fan]

Path loss is also proportional to the square of the frequency, so it's swings and roundabouts.

Think of it more in terms of antenna aperture size. The more metal you have in the air, irrespective of frequency, the louder the signal will be.

Roger that, my problem/challenge is that once something starts to look like more than a DirecTV dish (about 1 meter or less) or like a regular old-fashioned (yagi) TV antenna it won't pass the aesthetic judgment.  In fact, of the two, a 1 meter dish might be easier to camouflage than the yagi.  If it weren't for the appearance constraint the idea of a 3 meter dish seems like a winner - works at a reasonable frequency, not too hard to point, works with a reasonable amplifier and receiver.  I think the answer is live without straight up and down or find another place to implement the system, or find another project , but I'm not there yet... 

[retrolefty]

One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations

 Well even before EME and HOA expectations, some wise Ham once coined the phrase "If your antenna didn't fall down last winter then it's too small." 

[Electro Fan]

One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations

 Well even before EME and HOA expectations, some wise Ham once coined the phrase "If your antenna didn't fall down last winter then it's too small." 

That is a good one  

Sometimes empirical evidence can lead the way even ahead of math.

If anyone interested in EME link budgets (or link budgets in general) hasn't take the opportunity to download vk3um's EME Calculator you might want to check it out - it is an impressive program.

http://www.vk3um.com/eme%20calculator.html

But someone may have to contact vk3um to let him know that he needs to add another tab that accounts for this ("If your antenna didn't fall down last winter then it's too small.") variable. 

[cdev]

Horn..

A horn made out of chicken wire or even a discarded cardboard refrigerator box or foam core covered with aluminum foil would have enough gain. You could fold it up when you weren't using it.


Seriously. The first radio telescope was a horn. Balance it on its center of gravity so you can steer it by hand..then sit out on your lawn with a deck chair and wait for the moon to rise..  It might be funny looking but it would get the job done.

[VK5RC]

Most horn configured antennas are typically used to irradiate the dish as their gain is too low i.e. they are too broad an angle often 30degrees. The dish is just a reflective structure not the real 'antenna'. Horns also allow relatively easily rotary polarisation (helps with Faraday rotation effect) but also typically include the ability to have reverse polarity on receive as compared with transmission.
Currently on of the better designs appears VE4MA Super, the recent publication of DUBUS Vol 44 2/4 (the German radio Society's VHF technical publication) has an excellent article by Paul Wade W1GHZ (he also has an excellent website like VK3UM) on gain/temp noise of the various commonly used feed horns.
EF if you get it up and going I might be there as well, currently I have about 300W at 1296MHZ PA going OK, some PSU and computer interface issues at present.

[Electro Fan]

Most horn configured antennas are typically used to irradiate the dish as their gain is too low i.e. they are too broad an angle often 30degrees. The dish is just a reflective structure not the real 'antenna'. Horns also allow relatively easily rotary polarisation (helps with Faraday rotation effect) but also typically include the ability to have reverse polarity on receive as compared with transmission.
Currently on of the better designs appears VE4MA Super, the recent publication of DUBUS Vol 44 2/4 (the German radio Society's VHF technical publication) has an excellent article by Paul Wade W1GHZ (he also has an excellent website like VK3UM) on gain/temp noise of the various commonly used feed horns.
EF if you get it up and going I might be there as well, currently I have about 300W at 1296MHZ PA going OK, some PSU and computer interface issues at present.

VK5RC,

Looks like your design has some similarities to VE2ZAZ in terms of dish size and operating at 1296 MHz.  Any other similarities or differences between his design and yours that you see as notable?  At the time you posted the other day I was pretty focused on a yagi antenna but now that it seems like the conclusion is that 1 yagi isn't going to go straight up and down I guess I have to consider a parabolic antenna.  It looks like you have done a nice job of making it movable - but I can't tell from your photo where you might be moving it to?  Does it fit through your garage doors and live in the garage when not in operation?  Thx, EF

[VK5RC]

Hi EF,
Unfortunately it does not fit through the garage doors, it is about 3.8m tall, when the dish is vertical. I store it around the side of the house and to do so must remove the coax, feed horn, the feed horn support (actually a bit of bent motor car exhaust pipe) and the extension pieces for the front legs of the Engine mount/dish support. It takes about 10-15 mins to set it up and another 15 to take down. It has to go through a 1.3m wide gait and stores down the side of the house, chained to the house wall for wind issues. I have only fired it up a couple of times as it does take a bit of organising with my work and the moon needs to be in a position where I can see it (to aim the dish)The moon can't be too close to the sun and I don't really want to be doing this at 3am local time.

One of the more useful exercises was to look for sun noise, this involved experimentally confirming that the focal point of the dish was where it should be and the equivalent of the feed horn similarly. 2cm off can be 3dB difference. It also allows you to know if the dish has a 'squint' i.e. does it look electrically where it is pointed  physically. I built a 3 pole 1296MHz  band pass filter and used a USB dongle radio, the FunCube Pro2+ and Spectrum lab to average the noise. I am a few dB down on what it should be (cold sky to sun noise)according to VK3UM calculator. I have taken about 18months to get where I am but am not in a great rush as then I will have to think of something else! Actually thinking of looking at some ionosphere RF pulse responses, using the dish and power amps etc.

 Below is the dish stored. Note it is a 3m dish not 4m as photo labelled.

Remember the fun is the process of getting there! I have learnt a lot along the way.

[Electro Fan]

Hi EF,
Unfortunately it does not fit through the garage doors, it is about 3.8m tall, when the dish is vertical. I store it around the side of the house and to do so must remove the coax, feed horn, the feed horn support (actually a bit of bent motor car exhaust pipe) and the extension pieces for the front legs of the Engine mount/dish support. It takes about 10-15 mins to set it up and another 15 to take down. It has to go through a 1.3m wide gait and stores down the side of the house, chained to the house wall for wind issues. I have only fired it up a couple of times as it does take a bit of organising with my work and the moon needs to be in a position where I can see it (to aim the dish)The moon can't be too close to the sun and I don't really want to be doing this at 3am local time.

One of the more useful exercises was to look for sun noise, this involved experimentally confirming that the focal point of the dish was where it should be and the equivalent of the feed horn similarly. 2cm off can be 3dB difference. It also allows you to know if the dish has a 'squint' i.e. does it look electrically where it is pointed  physically. I built a 3 pole 1296MHz  band pass filter and used a USB dongle radio, the FunCube Pro2+ and Spectrum lab to average the noise. I am a few dB down on what it should be (cold sky to sun noise)according to VK3UM calculator. I have taken about 18months to get where I am but am not in a great rush as then I will have to think of something else! Actually thinking of looking at some ionosphere RF pulse responses, using the dish and power amps etc.

 Below is the dish stored. Note it is a 3m dish not 4m as photo labelled.

Remember the fun is the process of getting there! I have learnt a lot along the way.

I'm with you, it's a journey as much or more than a destination.

I think what you are building is along the lines of something I'd really enjoy attempting and hopefully doing but I'm not sure if I have the skill and knowledge to figure it all out.  I have a hunch with time it might be possible and it sure would be a great accomplishment - so I definitely admire what you and others are doing.

You mentioned you are a few dB down; is that extra margin you will have when you find those dBs or do you need to find them to get it fully operational?  Have you been able to get a signal up to the Moon and directly back to your station?  If so, that is spectacular in my book and even to be on the doorstep is very cool.

As for the storage arrangement I might have to look for an even more modular approach to get it all in the garage when not in operation - the antenna diameter seems to be the gating factor.