EME72B 23CM TRANSVERTER KIT
Saturday 31st September 2011

EME72B 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 onwards are now being supplied with the NEC NE3210S01 HJ FET & some minor changes have been made to the active bias circuit. The 150ohm resistor has changed to a 220ohm, & the 2k7 resistor has changed to a 1.2k. No other changes are needed & performance is the same. No attempt has been made to retune the input circuit for a better noise figure.

COMPLETE 23CM TRANSVERTER BLOCK DIAGRAM

Shows how to wire all the kits together including the EME66 Sequencer wiring. Download

CONSTRUCTION IMAGES OF THE EME72B PROTOTYPE KIT

The above image shows how the components are soldered to the EME72B board. A 25mm wide Tinplate strip is soldered around the board to make it easy to mount the SMA09 connectors. The 4 x mounting lugs on the SMA09 connectors are broken off with a pair of pliars, & then the backs are filed flat & soldered to the Tinplate box.

The Transverter above uses 2 x Hammond 1444-12 Aluminium Chassis Boxes ( 178x127x51mm ) Bolted together. RS Components do not stock the Hammond covers ( 1434-12 ) to suit the 178mm long boxes, but do stock the larger size 1434-14 ( 229x127mm ) which can be cut to length. The front panel ( 127x101mm ) was cut from 1mm Aluminium sheet, or you can buy another 1434-14 cover & cut to size. The heatsink & fan is a P4 Pentium which was a surplus 12 volt unit from a PC, but is now stocked by Mini-Kits.

Please Note: The EME162-1200MHz 1Watt driver amplifier is not shown in the above picture & is required to drive the 20Watt Mitsubishi RA18H1213G amplifier to 20Watts or more.

Download a complete list of parts in Excel format to work out what you require & email us your list when ordering. The list includes most parts that are shown in the above picture excluding the boxes.

BELOW SHOWS THE TESTED RESULTS OF THE PROTOTYPE KITS 

KIT CHANGES & MODIFICATIONS

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 HJ FET & some minor changes have been made to the active bias circuit. The 150ohm resistor has changed to a 220ohm, & the 2k7 resistor has changed to a 1.2k. No other changes are needed & performance is the same. No attempt has been made to retune the input circuit for a better noise figure.

2/ This applies to all Kits using the NE3210S01. 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 & lowers the noise figure.

	The Picture Left shows how L1 was connected to the input of the NE3210S01.		The Picture left is a EME103 preamplifier but is essentially the same as the EME72 transverter. L1 has been changed 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 & 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 to us in December were in fact 6.2 volt Zener diodes. The Transistor should have a 3H marking on the case. Please email us if you have the problem & we will post a replacement BC857 transistor to you.

4/ Instability of the MGF1302 or receiver taking off. This is due to a problem on the Local Oscillator input to the ERA3 Amplifier. A small square piece of ferrite absorb can be placed on the circuit board between the preamplifier section & the ERA3 multiplier shown below. You might find some ferrite absorbmaterial in an old 12GHz Satellite LNB. I think its a 50ohm mismatch problem but these are difficult problems to fix.

5/ A number of constructors have had to replace the ADE11X mixer. I am still unsure if it is due to manufacturing problems or if it has been overheated when it is soldered to the board. Symptoms are low TX output & low gain receiver. Driving the Mixer with excessive 144MHz power can also damage it.

6/ The TX output from the EME72 is not really enough to drive a RA18H1213G module to full power, ( 20 Watts ). Recent tests on the RA18H1213G modules gain has been around 23dB, where as earlier batches we were getting 27dB, but I am unsure if Mitsubishi has changed the modules internally. Along with this the EME72 has lost some gain in current transverters which may be due to extra losses in the mixer & gain stages that only allows around +10dBm output compared to around +13dBm on older Kits. So total loss could be around 7dB with current Kits. A new 1 Watt driver Kit EME162 is now available from Mini-Kits to drive the RA module to full output power.

7/ The EME72 23cm Transverter can be used for FM repeater operation with the addtion of an extra EME65 local oscillator & two new crystals. No wiring details are available at this time. A number of other components including pin diodes & switching is required.

The crystals chosen give a 20MHz split & cover the following ranges with a 144 to 148MHz I/F.

EME65 LO1. 95.750MHz crystal x2 x3 = 574.500MHz x2 = 1149MHz mix with 144-148MHz = 1293 to 1297MHz

EME65 LO2. 94.08333MHz crystal x2 x3 = 564.500MHz x2 = 1129MHz mix with 144-148MHz = 1273 to 1277MHz

This allows for coverage of the 1296MHz SSB segment plus the 1273/1293 MHz Repeater segment.

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