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member-projects:g4klx-23cms-eme [2025/04/14 15:33] – g4klxmember-projects:g4klx-23cms-eme [2026/08/07 20:58] (current) – Mort upgrade: tighten emphasis markers so they parse again 0.0.0.0
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-** The Power Amplifier **+**The Power Amplifier**
  
 I wanted to have at least 200 Watts for EME, but with the use of digital modes where the transmission time can be up to two minutes, I really needed a much larger amplifier that I could underrun to ensure that it would survive the long overs of continuous carrier. I wanted to have at least 200 Watts for EME, but with the use of digital modes where the transmission time can be up to two minutes, I really needed a much larger amplifier that I could underrun to ensure that it would survive the long overs of continuous carrier.
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 Roger G4BEL was a well known operator in the Cambridge area, unfortunately he became a silent key in early 2024 and his equipment was disposed of. Amongst it was a 600 Watt DB6NT amplifier already built into a rack case with fans and all of the required DC switching. Just provide 28 Volts at lots of Amps and some RF and off you go. For full output about 18 Watts is required so my IC-905 at 10 Watts will never push it to full power. The amplifier was bought, along with some other bits and pieces. Roger G4BEL was a well known operator in the Cambridge area, unfortunately he became a silent key in early 2024 and his equipment was disposed of. Amongst it was a 600 Watt DB6NT amplifier already built into a rack case with fans and all of the required DC switching. Just provide 28 Volts at lots of Amps and some RF and off you go. For full output about 18 Watts is required so my IC-905 at 10 Watts will never push it to full power. The amplifier was bought, along with some other bits and pieces.
  
-** The Preamplifier **+**The Preamplifier**
  
 I had hoped to buy a G4DDK preamplifier which are state of the art, but Sam has stopped making them. I therefore sourced a WD5AGO preamp which promised to have similar performance, typically a noise figure of between 0.2 and 0.3 dB and a nice high gain from a two stage design. I also bought an old DB6NT preamplifier from the G4BEL SK estate which has a noise figure of around 0.7 dB as a standby. I had hoped to buy a G4DDK preamplifier which are state of the art, but Sam has stopped making them. I therefore sourced a WD5AGO preamp which promised to have similar performance, typically a noise figure of between 0.2 and 0.3 dB and a nice high gain from a two stage design. I also bought an old DB6NT preamplifier from the G4BEL SK estate which has a noise figure of around 0.7 dB as a standby.
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 At the dish end this pre-amplifier is fed through an isolating relay, which switches the pre-amplifier over to a dummy load on transmit to protect it. This relay is energised on receive rather than on transmit to give fail-safe operation. At the dish end this pre-amplifier is fed through an isolating relay, which switches the pre-amplifier over to a dummy load on transmit to protect it. This relay is energised on receive rather than on transmit to give fail-safe operation.
  
-** The Dish Rotator **+**The Dish Rotator**
  
 There aren't too many options for actually pointing the dish. Many people use Slew Drives which are apparently very good, and some create completely homebrew systems and use some form of encoder to accurately measure the pointing angles. Since a 2.4m dish isn't particularly heavy, relatively speaking, and doesn't have a particularly narrow beamwidth, I went for an easy option. I bought a [[https://thedxshop.com/product/spid-ras-azimuth-elevation-rotator/|SPID RAS]] which does both azimuth and elevation control. The controller has a USB input which allows for easy software control of the positioning. There have been reports of losing alignment under normal operation, but I haven't seen that. There aren't too many options for actually pointing the dish. Many people use Slew Drives which are apparently very good, and some create completely homebrew systems and use some form of encoder to accurately measure the pointing angles. Since a 2.4m dish isn't particularly heavy, relatively speaking, and doesn't have a particularly narrow beamwidth, I went for an easy option. I bought a [[https://thedxshop.com/product/spid-ras-azimuth-elevation-rotator/|SPID RAS]] which does both azimuth and elevation control. The controller has a USB input which allows for easy software control of the positioning. There have been reports of losing alignment under normal operation, but I haven't seen that.
  
-** The Dish Mount **+**The Dish Mount**
  
 This was purpose designed by Dave G0LBK. It is similar in design to the ones used to hold a satellite dish on flat roofs and weighed down with slabs. This one was designed to be much heavier duty and is fabricated out of 50mm steel scaffold pole and angle iron, and weighed down by almost 360 kg of concrete slabs. It is very stable. My wife painted it in green Hammerite. The mount is designed to be "temporary" with no permanent mounting into the ground for move to a later location, and maybe to help with planning permission issues should they arise. This was purpose designed by Dave G0LBK. It is similar in design to the ones used to hold a satellite dish on flat roofs and weighed down with slabs. This one was designed to be much heavier duty and is fabricated out of 50mm steel scaffold pole and angle iron, and weighed down by almost 360 kg of concrete slabs. It is very stable. My wife painted it in green Hammerite. The mount is designed to be "temporary" with no permanent mounting into the ground for move to a later location, and maybe to help with planning permission issues should they arise.
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 The dish feed is hung in front of the dish on the end of two glass fibre square section poles, and with ropes holding the end for stability. The dish feed is held firmly by cut and carved (!!) wooden blocks and lengths of M6 threaded rod. All of these threaded rods have been kept away from being a multiple of a quarter wave in length to remove any interaction with RF. Therefore the only bits of metal in the view of the dish are the Septum Feed and the co-ax, and nothing else. The dish feed is hung in front of the dish on the end of two glass fibre square section poles, and with ropes holding the end for stability. The dish feed is held firmly by cut and carved (!!) wooden blocks and lengths of M6 threaded rod. All of these threaded rods have been kept away from being a multiple of a quarter wave in length to remove any interaction with RF. Therefore the only bits of metal in the view of the dish are the Septum Feed and the co-ax, and nothing else.
  
-** The Sequencer **+**The Sequencer**
  
 This was my own design, and is in many ways the heart of the EME system. It's based on an Arduino Uno and the four relay Arduino shield, the [[https://github.com/g4klx/Sequencer|sketch]] is available from my GitHub. It has two transmit inputs and controls three relays, with timings of around 30ms between each. This was my own design, and is in many ways the heart of the EME system. It's based on an Arduino Uno and the four relay Arduino shield, the [[https://github.com/g4klx/Sequencer|sketch]] is available from my GitHub. It has two transmit inputs and controls three relays, with timings of around 30ms between each.
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-** Sundry Bits and Pieces **+**Sundry Bits and Pieces**
  
 Another 2U case holds the main amplifier power supply, 28V at up to 70A, and a 15V 10A power supply to power the SPID RAS mentioned above. All of the power supplies for the system, except for the IC-905, are from Meanwell. Another 2U case holds the main amplifier power supply, 28V at up to 70A, and a 15V 10A power supply to power the SPID RAS mentioned above. All of the power supplies for the system, except for the IC-905, are from Meanwell.
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-** The Software **+**The Software**
  
 In this modern world, a PC or similar is required for operation in most parts of the hobby, and EME is included. Indeed it is the development of WSJT-X that has allowed many people to try EME who would not have been able to put out a useful signal before, or would have worked very few stations otherwise. In this modern world, a PC or similar is required for operation in most parts of the hobby, and EME is included. Indeed it is the development of WSJT-X that has allowed many people to try EME who would not have been able to put out a useful signal before, or would have worked very few stations otherwise.
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 Feedback on operation is done via the [[https://logger.hb9q.ch/|HB9Q EME Logger]]. Other EME software is available, most notably from [[https://www.vk5dj.com/doug.html|VK3UM]] (SK). Feedback on operation is done via the [[https://logger.hb9q.ch/|HB9Q EME Logger]]. Other EME software is available, most notably from [[https://www.vk5dj.com/doug.html|VK3UM]] (SK).
  
-** Connecting it All Up **+**Connecting it All Up**
  
 Due to the complexity of the system, it is better to show the connections between the various parts by type. These are: RF Connections, Sequencer Control, and Software Links. I do not claim any originality in the way my system is connected, but it probably reflects many others. I know that the sequencer control is very close to that used by Dave G0LBK although the hardware used is substantially different. Due to the complexity of the system, it is better to show the connections between the various parts by type. These are: RF Connections, Sequencer Control, and Software Links. I do not claim any originality in the way my system is connected, but it probably reflects many others. I know that the sequencer control is very close to that used by Dave G0LBK although the hardware used is substantially different.
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-** The Results **+**The Results**
  
 The results have been spectacular. I expected EME to be a struggle, and it sometimes is, but not a lot of the time. I started on my first evening running 150 Watts, the old pre-amplifier, and a linear dish feed. This latter item means that I started with a 3dB penalty immediately compared to most other operators. As was right, my first EME QSO was with Dave G0LBK, with no stress whatsoever. The sked was arranged via WhatsApp, but all information was exchanged via the moon. On that first night I worked 13 different stations! The results have been spectacular. I expected EME to be a struggle, and it sometimes is, but not a lot of the time. I started on my first evening running 150 Watts, the old pre-amplifier, and a linear dish feed. This latter item means that I started with a 3dB penalty immediately compared to most other operators. As was right, my first EME QSO was with Dave G0LBK, with no stress whatsoever. The sked was arranged via WhatsApp, but all information was exchanged via the moon. On that first night I worked 13 different stations!
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-By the next night I had replaced the pre-amplifier with the lower noise one, and proceeded to work a total of 65 unique stations in my first week of operation with my compromised system. For the next period of operation I had replaced the dish feed with my Septum Feed and slowly increased my power to 300W or so. By April 2025 I had worked 154 unique stations off the moon (known as initials), in all continents, in 115 grids, and in 39 DXCC entities. I think I have worked 15 US states.+By the next night I had replaced the pre-amplifier with the lower noise one, and proceeded to work a total of 65 unique stations in my first week of operation with my compromised system. For the next period of operation I had replaced the dish feed with my Septum Feed and slowly increased my power to 300W or so. By August 2025 I had worked 191 unique stations off the moon (known as initials), in all continents, in 142 grids, and in 45 DXCC entities. I have worked 20 US states.
  
 {{:member-projects:23cms-march-europe.png?200|}} {{:member-projects:23cms-march-na.png?200|}} {{:member-projects:23cms-march-europe.png?200|}} {{:member-projects:23cms-march-na.png?200|}}
  
-WSJT-X incorporates an Echo mode which transmits short pulses and detects the echo, and I can usually see returns of around -19dB (in a 3kHz bandwidth) which is more than enough to be able to work myself, if that were possible. Indeed I have worked many people running systems similar or smaller than mine. The smallest station that I have worked is G0HIK with two 33 element yagis, OE3JPC who uses two 56 element yagis is also regularly worked when the path loss is low.+WSJT-X incorporates an Echo mode which transmits short pulses and detects the echo, and I can usually see returns of around -19dB (in a 3kHz bandwidth) which is more than enough to be able to work myself, if that were possible. Indeed I have worked many people running systems similar or smaller than mine. The smallest stations that I have worked have been G0HIK with two 33 element yagis, KB2SA using a 1m dish, and OE3JPC who uses two 56 element yagis is also regularly worked when the path loss is low.
  
 An invaluable resource for EME operations above 2m is the 432 and Above EME Newsletter. The [[https://eme.radio/|eme.radio]] site is more than just the home of this newsletter and its archives and is highly recommended. An invaluable resource for EME operations above 2m is the 432 and Above EME Newsletter. The [[https://eme.radio/|eme.radio]] site is more than just the home of this newsletter and its archives and is highly recommended.
  
-** The Future **+**The Future**
  
 I have numerous changes that I want to make to the station, all of which are to do with ease of use and not in improving capabilities. Of course I would like a larger dish, but it already dominates the garden and my wife, who has been very accommodating of my hobby, has said no to that idea. I don't want any more power, and I think that my receive side is about as good as it can be. I would like to make some changes to the mechanical side to make the mount for my dish feed a little more firm, and the dish/feed counterbalance currently uses a four litre container of car screen wash in addition to the counterweight to make the system more balanced. I have numerous changes that I want to make to the station, all of which are to do with ease of use and not in improving capabilities. Of course I would like a larger dish, but it already dominates the garden and my wife, who has been very accommodating of my hobby, has said no to that idea. I don't want any more power, and I think that my receive side is about as good as it can be. I would like to make some changes to the mechanical side to make the mount for my dish feed a little more firm, and the dish/feed counterbalance currently uses a four litre container of car screen wash in addition to the counterweight to make the system more balanced.
  
-A potential problem is the results of WRC-23 which may have a huge impact on EME operation on 23cms, but at this time no-one knows for sure what it may be. In the extreme case I, and many others, may have to pack up on 23cms and look at getting going onto 13cms. This wouldn't be the most difficult change, the IC-905 can easily accommodate it, and the sequencer and relays would operate on 13cms without modification, but it would be an unwelcome termination of activity on 23cms, a band I have been active on since 1985.+A potential problem is the results of WRC-23 which may have a huge impact on EME operation on 23cms. OFCOM in the UK have decided that they will not implement the technical side of WRC-23 so restrictions on power, antenna gain, and elevation will not affect us, and the FCC in the US will not implement it either. However other administrations in Europe may take a different view, and this may affect EME operation for them, and hence 23cms EME activity. It already looks like we will be moving weak signal operation on 23cms to either 1298 or 1299 MHz which can be accommodated by most modern radios. It will be interesting to see how this will play out over the next few months. 
 + 
 +I have bought a 250W amplifier pallet for 13cms, and once built, and added a suitable dish feed and low noise amplifier, I should be able to be active on 13cms EME. I also bought a Pluto Plus as a suitable SDR for use on 13cms so I could keep using the QMAP program for spotting stations. It has also been suggested that I should look into 10 GHz EME operation, my dish has a very fine mesh on it which is suitable although the surface isn't the most accurate. However despite this, it will operate to some extent on that band, and it'd be fun to try.
  
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member-projects/g4klx-23cms-eme.1744644787.txt.gz · Last modified: by g4klx