EME103 23cm Pre-Amplifier Kit

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EME103 Description:

The EME103 Kit was one of the most popular Kits that we ever sold. The first verson of this Kit was produced in the mid 1990's and continued until around March 2011. The preamp used the Mitsubishi MGF1302 GasFET and was able to be used with minor changes on both the 13 and 23cm bands. There were a few changes in late Kits around 2010 due to the MGF1302 becoming obsolete, so the Kit was then sold with the NEC NE3210S01 and some small improvements were made to the input inductor.

For a complete description of the Kit before it was discontinued please download the Complete EME103 KIT Notes

Kit Constructors Alert:

This applies to all Kits sold after October 2010 Due to the Mitsubishi MGF1302 no longer being manufactured, we have decided to change the device to a more modern PHEMT device that are mass produced. Kits late September 2010 on wards are now being supplied with the NEC NE3210S01 HJ FET and some minor changes have been made to the active bias circuit. The 150ohm resistor has changed to a 220ohm, and the 2k7 resistor has changed to a 1.2k. No other changes are needed and performance is the same. No attempt has been made to re tune the input circuit for a better noise figure. The NE3210S01 is no longer manufactured and has been replaced with the CE3512K2.

Kit Construction Notes:

  • EME103B Top View
    Top view of the later model EME103B with the changes to the input inductor
  • EME103B Top View
    Top view of the EME103B with the original input inductor
Changes and Updates:

1/ This applies to all Kits sold before October 2010. Due to the Mitsubishi MGF1302 no longer being manufactured we have decided to change the device to a more modern PHEMT device that are mass produced. Kits late September onwards are now being supplied with the NEC NE3210S01 or CE3512K2 HJ FET and some minor changes have been made to the active bias circuit. The 150ohm resistor has changed to a 220ohm, and the 2k7 resistor has changed to a 1.2k. No other changes are needed and performance is the same. No attempt has been made to re tune the input circuit for a better noise figure.

2/ This applies to all Kits using the NE3210S01 or CE3512K2. Please note that the input inductor hoop L1 used in early Kits has now been changed to a 3.5 turn coil. This provides a better match the input of the HEMT and lowers the noise figure.

  • Original EME103 Input Inductor
    Fitting of the input inductor L1 for a NE3210S01 or CE3512K2
  • Replacement EME103 Input Inductor
    L1 changed in later Kits to 3.5 turns of 0.315mm ECW on a 2.5mm drill bit spaced 1.5 turns.

3/ This applies to all Kits between January and June 2008. A number of constructors have reported that the voltages around the MGF1302 GasFET have been incorrect. Some have found the BC857 transistor to be faulty. We have in fact found that the complete batch of BC857 Transistors supplied in December were in fact 6.2 volt Zener diodes.

2/ Any instability problems are usually caused by the RF connections in and out of the board. Only connectors like SMA can be used and have to be soldered very directly to the board. Mounting the PC board inside an enclosure can also cause instability as they can act like Microwave Waveguides. Enclosure sizes that are close to a Waveguide size for 1200 to 2400MHz should be avoided.