KIT FAULTS
& MODIFICATIONS
1/ 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.
2/ 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.
3/ 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.
4/ 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.
5/ 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.
Thursday
9th July 09 
