EME173 Series Receive Preamplifier Kits

EME173A6 KIT

EME173A6 6M Pre-Amplifier Kit

PLEASE NOTE: That this Product will gradually be updated to Rev2
that includes some improvements to the circuit.

Please Note: that all information including pictures on this web page are copyright to Mini-Kits and must not be used on any other web site, or reproduced in any publication.

The EME173 PC board was designed to suit the construction of receive only preamplifiers 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 inductor ensuring stable operation. The preamplifiers 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 EME173A70 Kit however is around 500MHz maximum.

Kit Constructors Alert:

1/ There are no current issues with these Kits.

EME173A6 Kit Notes:

The Preamplifier has been designed to be easy to construct, and can be centre frequency tuned for use between 45 and 65MHz, and is suitable for the 50-54MHz 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 and1dB NF at 800MHz along with high cross modulation performance. The BF998 incorporates integrated gate input protection diodes to help prevent damage to the device from static. The Preamplifier design is essentially a tuned input MesFET, with a wide band 50ohm matching transformer on the output. The Preamplifier however can also be used on a 75ohm antenna, or coaxial cable systems. BUY THIS PRODUCT

EME173A6 KIT
The picture shows the basic EME173A6 Kit with optional SMA connectors. The red toroidal inductor allows the amplifier to be powered via the coaxial cable as a masthead amplifier.
EME173A6B

Fitting of the input inductor L1 for 50MHz

EME173A6C

How to position the output matching transformer L2.

EME173A6DFitting of the optional inductor L3 for DC power via the coaxial cable.

SMA PCB TopHow to solder coaxial cable to the board when connectors are not required.

EME173A2 Kit Notes:

The Preamplifier has been designed to be easy to construct, and can be centre frequency tuned for use between 115 and 180MHz, 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 noise and1dB NF at 800MHz along with high cross modulation performance. The BF998 incorporates integrated gate input protection diodes to help prevent damage to the device from static. The Preamplifier design is essentially a tuned input MesFET, with a wide band 50ohm matching transformer on the output. The Preamplifier however can also be used on a 75ohm antenna, or coaxial cable systems. BUY THIS PRODUCT

EME173A2 KIT
The picture shows the basic EME173A2 Kit with optional SMA connectors. The yellow toroidal inductor allows the amplifier to be powered via the coaxial cable as a masthead amplifier.
EME173A2B

Fitting of the input inductor L1 for 144MHz

EME173A2C

How to position the output matching transformer L2.

EME173A2DFitting of the optional inductor L3 for DC power via the coaxial cable.

SMA PCB TopHow to solder coaxial cable to the board when connectors are not required.

EME173A70 Kit Notes:

The Preamplifier has been designed to be easy to construct, and can be centre frequency tuned for use between 350 and 500MHz, and is suitable for the 430-450MHz 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 and1dB NF at 800MHz along with high cross modulation performance. The BF998 incorporates integrated gate input protection diodes to help prevent damage to the device from static. The Preamplifier design is essentially a tuned input MesFET, with a wide band 50ohm matching transformer on the output. The Preamplifier however can also be used on a 75ohm antenna, or coaxial cable systems. BUY THIS PRODUCT

EME173A70B
The picture shows the basic EME173A70 Kit with optional SMA connectors. The yellow toroidal inductor allows the amplifier to be powered via the coaxial cable as a masthead amplifier.
EME173A70B

Fitting of the input inductor L1 for 430MHz

EME173A2C

How to position the output matching transformer L2.

EME173A2DFitting of the optional inductor L3 for DC power via the coaxial cable.

SMA PCB TopHow to solder coaxial cable to the board when connectors are not required.

Mounting In A Die cast Enclosure:

70CM Preamplifier Enclosure
The pictures show how to mount the EME173 PC board into a Hammond 1590A die cast enclosure.
EME173A70B

Alignment for drilling the 1/4" holes for the SMA connectors.

EME173A2C

Shown how the corners of the board are cut to fit the enclosure

EME173A2DHow the SMA42 connector and extra nut are used to fit the enclosure

SMA PCB TopHow the optional feed through capacitor is fitted to supply power directly to the preamp

Mounting Procedure:

  • Cut out the two corners of the PC board using a nibbling tool.

  • Solder an extended SMA socket with washer and nut ( SMA39 ), 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 preamp are straight in both planes.

  • Solder a SMA male PC board socket ( SMA12 ) to the output of the PC board making sure that it is at right angles to the board. This can be a bit more difficult to fit as it is a compromise as we could not get a male type with the same PC board mounting as the female socket.

  • Mark and drill the two 6.5mm holes in the die cast box as shown in the picture above.

  • Fit a extended SMA female to female bulkhead mount ( SMA42 ) through one end of the box and screw a nut and washer on only by couple threads to allow enough clearance to then get the preamp board into the box. Refer to the picture above on how two nuts and a washer are used to take up the clearance on the outside of the box.

  • Slide the preamp board into the box and pass the extended input sma connector through the hole in the box, and lightly screw on the nut and washer to hold it into place.

  • Lightly tightened up the output sma male to the sma bulkhead adaptor.

  • Fabricate a small piece of brass shim as shown for the input sma connector to take up the slack due to the sloping sides of the box, and solder it to the top of the input sma socket as in the picture.

  • Finally carefully tighten the input sma 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.

EME173 Performance Tests:

EME173A6 Gain Test

EME173A6 Preamplifier Gain and Bandwidth Test

EME173A2 Preamplifier input return loss

EME173A2 Preamplifier Gain and Bandwidth Test

EME173A2 Preamplifier input return loss

EME173A70 Preamplifier Gain and Bandwidth Test

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Kit Changes and Modifications

EME173 RX Preamplifier Kits

1/There are no reported problems with these Kits.

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