ZL3TDW
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What height tower is appropriate for EME? Does it have to be 100’ or 25’?
EME
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All you need is a clear shot at the moon so any tower height that achieves this would work.
...or no tower at all if you don't need to clear any obstacles.
RFI-EMI-GUY
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The height needs to accommodate mechanical clearance for the rear of the yagi (or whatever antenna array) at the desired elevation, often straight up.
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This works for me !
Lauri
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What frequency? What antenna or antenna array are you planning for? Will you have elevation control, or will you be setting the antenna to a fixed elevation angle (probably to leverage ground gain)?
In general, really high is not needed. You really want as low as you can that clears obstacles and works mechanically, this shortens feedline runs, which is important when you are counting every tenth of a dB of system gains and losses.
T!
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There are more than just the high power-brute force way to get into EME.
The digital age has put it into the budget of many an average ham. The use of the mode JT65 has changed this frontier dramatically.
I have a friend who is trying to get me into a project with her where we will do 2 metre EME. It hasn't gone anywhere as of today; its still early-- but this is a little of what caught her interest;
______________________________________________________________________________________________
As an aside---- as graduate students we had access to some niffty toys--- one was a 20 metre dish with a blow torch of a 900MHz transponder/transmitter. It was intended for serious things by the University of California...... but try telling that to some physics students.
When is was not booked we would often swing that dish at the moon and "ping" it. It was neat to realize it took ~2.5 seconds for the RF's round trip.
Hearing the return echo was an experience that cemented in my body-gestalt just what is the true science of the "speed of light."
Another interesting aside--- if you modulate the signal with voice, it will return with a haunting ghost-like quality.
"Follow the Yellow Brick Road, Follow the Yellow Brick Road......................"
*********
Wonder what was happening here ?
Hint: the moon is spherical....think reflection off a sphere +2000 miles in diameter.
Lauri
.
There are more than just the high power-brute force way to get into EME.
The digital age has put it into the budget of many an average ham. The use of the mode JT65 has changed this frontier dramatically.
I have a friend who is trying to get me into a project with her where we will do 2 metre EME. It hasn't gone anywhere as of today; its still early-- but this is a little of what caught her interest;
______________________________________________________________________________________________
As an aside---- as graduate students we had access to some niffty toys--- one was a 20 metre dish with a blow torch of a 900MHz transponder/transmitter. It was intended for serious things by the University of California...... but try telling that to some physics students.
When is was not booked we would often swing that dish at the moon and "ping" it. It was neat to realize it took ~2.5 seconds for the RF's round trip.
Hearing the return echo was an experience that cemented in my body-gestalt just what is the true science of the "speed of light."
Another interesting aside--- if you modulate the signal with voice, it will return with a haunting ghost-like quality.
"Follow the Yellow Brick Road, Follow the Yellow Brick Road......................"
*********
Wonder what was happening here ?
Hint: the moon is spherical....think reflection off a sphere +2000 miles in diameter.
Lauri
.
Or, use mast-mount pre-amps.
Unfortunately completely different. In EME you want every bit of transmit power you can get too.
Or transverters at the antenna and then less feedline loss on a lower frequency band back to the shack.
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EME is not for the feint of heart. It is achievable for many hams today using JT65 digital protocol- but it requires a good understanding of the science involved.
The distance to and from the moon, coupled with very low reflective index of 5-7% places the circuit loses at +250-some dB's at 144 MHz.
Throw into the equation factors like Faraday rotation, libration fading, whether the moon is at perigee or apogee, the Doppler shifts and changing signal polarizations -- all make for a colourful mix (ie: 'a challenge.')
As one who has actually bounced signals off the Moon, I'd suggest anyone interested in trying it digest this article first--- but, bon appetit !
Lauri
EME is not for the feint of heart. It is achievable for many hams today using JT65 digital protocol- but it requires a good understanding of the science involved.
The distance to and from the moon, coupled with very low reflective index of 5-7% places the circuit loses at +250-some dB's at 144 MHz.
Throw into the equation factors like Faraday rotation, libration fading, whether the moon is at perigee or apogee, the Doppler shifts and changing signal polarizations -- all make for a colourful mix (ie: 'a challenge.')
As one who has actually bounced signals off the Moon, I'd suggest anyone interested in trying it digest this article first--- but, bon appetit !
Lauri
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View attachment 124518
EME is not for the feint of heart. It is achievable for many hams today using JT65 digital protocol- but it requires a good understanding of the science involved.
The distance to and from the moon, coupled with very low reflective index of 5-7% places the circuit loses at +250-some dB's at 144 MHz.
Throw into the equation factors like Faraday rotation, libration fading, whether the moon is at perigee or apogee, the Doppler shifts and changing signal polarizations -- all make for a colourful mix (ie: 'a challenge.')
As one who has actually bounced signals off the Moon, I'd suggest anyone interested in trying it digest this article first--- but, bon appetit !
Lauri
A friend of mine has DXCC via 2 meter EME, he had a pretty large array at the time. It’s been quite a few years ago since I’ve been at his station but EME wasn’t that difficult for his set up. He’s retired now and I believe his antenna farm is gone. He only operates remotely in multiple states and grids. He already has DXCC via Satellite too, I guess he’s still operating for the enjoyment 😊
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