EME173-Rev3 Preamplifier Kits

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EME173-Rev3 Description:

The EME173 PC board was updated in September 2020 due to the film trimmer capacitors being no longer available, and to improve the input matching circuit for a lower noise figure. The board was designed to suit the construction of receive only Pre-amplifiers for the 30 to 500MHz bands. All Kits use the low cost BF998 MesFET from NXP that has a low noise figure and were designed for television tuners. The output of the BF998 is matched to 50ohms using a tapped transformer ensuring stable operation. The Pre-amplifiers can all be adapted for frequencies outside the ranges specified for each product, by simply changing the turns on the input inductor. The upper range of the EME173-70CM Kit however is around 500MHz maximum.

Kit Constructors Alert:

1/ There are no current alerts for these products.

EME173-6M-Rev3 Kit Notes:

Currently there is no 6M Rev3 Pre-amplifier.

EME173-2M-Rev3 Kit Notes:

The Pre-amplifier has been designed to be easy to construct, and can be centre frequency tuned for use between 120 and 170MHz, and is suitable for the 144-148MHz Amateur Band. A low cost BF998 MesFET has been used as it has very good characteristics on the VHF to UHF bands. The BF998 was specifically designed for television tuners, and has a low 0.7dB NF at 145MHz along with high cross modulation performance. The BF998 incorporates integrated gate input protection diodes to help prevent damage to the device from static. The Pre-amplifier design is essentially a tuned input MesFET, with a wide band 50ohm matching transformer on the output. The Pre-amplifier however can also be used on a 75ohm antenna, or coaxial cable systems. BUY THIS PRODUCT

  • EME173-2M-Rev3 Preamplifier Top View
    Top view of the EME173-2M-Rev3 2m Pre-amplifier
  • EME173-2M-Rev3 Preamplifier Bottom View
    Top view of the EME173-2M-Rev3 2m Pre-amplifier
  • How to connect CT1 to the L1 Inductor
    Shows the connection of the 10pF capacitor CT1 to inductor L1
EME173-70CM-Rev3 Kit Notes:

The Pre-amplifier has been designed to be easy to construct, and can be centre frequency tuned for use between 400 and 500MHz, and is suitable for the 420-450MHz Amateur Band. A low cost BF998 MesFET has been used as it has very good characteristics on the VHF to UHF bands. The BF998 was specifically designed for television tuners, and has a low noise 1dB NF at 435MHz along with high cross modulation performance. The BF998 incorporates integrated gate input protection diodes to help prevent damage to the device from static. The Pre-amplifier design is essentially a tuned input MesFET, with a wide band 50ohm matching transformer on the output. The Pre-amplifier however can also be used on a 75ohm antenna, or coaxial cable systems. BUY THIS PRODUCT

  • EME173-70cm-Rev3 Preamplifier
    Top view of the EME173-70cm Rev3 Pre-amplifier
  • EME173-70cm-Rev3 Bottom View
    Bottom View of the EME173-70CM Rev3 showing the orientation of the BF988 MesFET.
EME173-Rev3 Performance Tests:

  • EME173-2M-Rev2 S21 Bandwidth
    EME173-2M Pre-amplifier Gain and Bandwidth Test.
  • EME173-2M-Rev3-S22
    EME173-2M Pre-amplifier output return loss S22.
  • EME173-70CM-Rev3-S21
    EME173-R3-70CM Pre-amplifier Gain and Bandwidth Test S21. For the lowest noise figure @ 432MHz, the gain should be tuned to maximum at 420MHz.
  • EME173-70CM-S22
    EME173-R3-70CM Pre-amplifier output return loss S22.
Mounting into a Die cast Enclosure:

This is for advanced constructors that have experience and access to a workshop with metal working tools. The basic tool requirements are a drill press, Vice, M1.5, M3, M6, and 1.4 inch drill bits, scriber, metal punch, and a hammer.

  • EME173 in a 1590A Enclosure
    The picture shows the basic EME173-70CM Kit mounted into a Hammond 1590A Enclosure.
  • 1590A Front Drilling Guide
    Alignment for drilling the 1/4" holes for the SMA connectors. Also shows the use of a nickel plated M6 shake proof washer.
  • 1590A Drilling Guide
    Drilling guide for the Hammond 1590A enclosure.
  • 1590A SMA Output connector
    How the SMA connector and extra nut are used to fit the enclosure.
  • DC Connector and 1N4007 Diode
    How to solder the1N4007 Diode from the DC connector to the board.
Mounting Procedure:

There can be some variations with connectors, and mounting hardware thicknesses that may require some experimentation when mounting boards into enclosures. Recently some SMA panel mount connectors may require additional washers due to the female thread not going all the way to the mounting flange. Many of the shake proof washers that are being supplied with SMA connectors are very flimsy and easily deform when tightening, so one picture above shows the use of a M6 shake proof washer that was used to securely hold the SMA connector to the enclosure.

  • Solder an extended SMA female, ( SMA49 ) to the input of the PC board making sure that it is at right angles to the board. Take your time here to make sure that the SMA connectors on both the input and output of the PC board are straight in both planes.

  • Solder the SMA50 Male connector to the top of the PC board making sure that it is at right angles to the board. See the picture above to see how it is then soldered to the bottom ground plane of the PCB.

  • Mark and drill the two 1/4 inch holes in the die cast enclosure as shown in the picture above. If you are fitting the optional 2.1mm DC connector, then also mark and drill a 8mm hole to suit.

  • Near the input of the PC board cut the corners away using a nibbling tool so that they clear the corners of the enclosure. Refer to the picture above on how this is done.

  • Fit a extended SMA female to female bulkhead mount ( SMA42 ) through one end of the enclosure, and screw a nut and washer on only by couple threads to allow enough clearance to then get the PC board into the enclosure. Refer to the picture above on how two nuts and a washer are used to take up the clearance on the outside of the enclosure. Some experimentation with the washer may be required to fit the SMA42 adapter. Sometimes Mini-Kits mounts the washer inside the enclosure, or if its too tight a fit it is then mounted on the outside.

  • Slide the PC board into the enclosure and pass the input SMA49 connector through the hole in the enclosure, and lightly screw on the SMA nut and washer to hold it into place. In many cases a M5 nickel steel shake proof washer maybe used to secure the connector better.

  • Lightly tightened up the output SMA50 male to the SMA42 bulkhead adapter.

  • Finally carefully tighten the input SMA49 nut using a suitable SMA spanner. Finally the nuts on the output SMA bulkhead adaptor can be tightened ensuring that there is not excessive stress placed on the board and connectors.

  • Fit the 2.1mm DC connector to the enclosure and rotate it and tighten the nut as shown in the picture above. Fit the 1N4007 diode as shown in the picture to protect the Pre-amplifier from reverse polarity.

  • Place the lid onto the enclosure and check that the Pre-amplifier is stable and does not oscillate.

Changes and Updates:

EME173-70CM KIT

1/ There are no current changes to these Kits