I’ve recently upgraded the Amplifier for our 2m EME station to one that can provide full-duty cycle operation at 1500 watts. The digital modes used for EME on 2m (JT65 and Q65) require an amplifier that can sustain full output for periods of 1 minute or more as well as sustain full power operation at a 50% duty cycle over an extended period of time.
Construction and Setup
Jim does an excellent job with the design and construction of his amplifiers. The parts are top-notch and the quality of construction and attention to detail are second to none. Jim provides components and sub-assemblies as well as some turn-key amplifiers.
He hand-builds each amplifier to his customer’s specifications and there is usually some wait time to receive a completed amplifier. The results are absolutely worth the wait!
The connection and setup of the amplifier was straightforward. It is well worth the effort to hook up an ALC feedback connection from the amplifier to your exciter. In our case, we are using an Icom IC-9700 to drive the amplifier. This radio does not have a positive sequencing control input for the power stage of the transceiver. Our setup uses an external sequencer to manage transmit and receive changeover and protect our tower-mounted preamplifiers. We have had numerous problems where sequencing errors damaged our preamps.
One of the unique features of Jim’s Amplifier Control Board is the inclusion of an ALC hold-back capability. The amplifier can be configured to send an output limiting ALC voltage to the driving transceiver to prevent any power from being applied until the sequencer completes the final Tx changeover step by keying the amplifier. This feature requires additional amplifier adjustment (the adjustment procedure is well covered in the documentation). This capability has eliminated the issue of sequencing problems causing damage to our preamplifiers!
The recommended power supply for this amplifier is a 48-volt, 62.5-amp switching design from Meanwell (Model RSP-3000-48). Jim set up the supply and provided the cabling to connect it to the amplifier. The supply is 240 VAC powered and is quite efficient. Jim adjusted the power supply’s output voltage and tested the amplifier with it with the amplifier before shipping.
Controls and Operation
The operation of the amplifier is straightforward. It is best to set the driving transceiver for a watt or so and perform some initial test transmissions to ensure that the antenna system is presenting a low SWR and that your station’s sequencing system is operating correctly. Note the LNA and Amplify Controls must be turned on for the ALC holdback feature to work correctly.
The amplifier provides PA Voltage and PA Current meters as well as bar-graph displays for Forward and Reflected power.
More Articles on EME
We are very pleased with our new amplifier! I’ve used it for quite a few contacts, and it performs great. It provides a full 1500 watts output with the digital modes used for EME work.
You can read more about our EME station project via the links that follow:
- EME Station 2.0 Part 1 – Goals and Station Design
- EME Station 2.0 Part 2 – Excavation, Footings, and Conduits for New Tower
- EME Station 2.0 Part 3 – Phase Tuned Receive Coax Cables
- EME Station 2.0 Part 4 – New EME Tower Is Up!
- EME Station 2.0 Part 5 – Control Cables and Rotator Controller
- EME Station 2.0 Part 6 – Tower Grounding System
- EME Station 2.0 Part 7 – Building Antennas
- EME Station 2.0 Part 8 – Elevation Rotator Assembly and Sub-System Test
- EME Station 2.0 Part 9 – H-Frame Assembly
- EME Station 2.0 Part 10 – Antennas On The Tower
- EME Station 2.0 Part 11 – Station Hardware in Shack
- EME Station 2.0 Part 12 – Station Software
- EME Station 2.0 Part 13 – H-Frame Enhancements
If you’d like to learn more about How To Get Started in EME, check out the Nashua Area Radio Society Tech Night on this topic. You can find the EME Tech Night here.