Hi All,
I got the MLA-30 that Matt provided working on the bench, but quite a lot of the components were damaged during the "de-gooping" process.
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However, I've manged to measure all the component values and have been able to work out the circuit.
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The input low pass filters were particularly badly damaged and I've had to by-pass those for the time being.
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Unfortunately the 30MHz input low pass filters are designed for a 50 Ohm input and output impedance, and when used in this circuit with a low value of source impedance and a high value of output load impedance, the response curve is anything but flat.
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I also noticed that while testing the common mode rejection by shorting the two inputs together, the circuit would oscillate and produce a -10dB signal at around 160MHz. So it isn't unconditionally stable, but this may not happen (or it may happen at another frequency) if the low pass filters were in circuit.
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Gain?
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Max 30dB
Min 10dB
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Input impedance
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1.5K Ohm at 1MHz
1.4K Ohm at 10MHz
600 Ohm at 20MHz
450 Ohm at 30MHz
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OIP2 approx +46dBm
OIP3 approx +20dBm
PSAT approx -3dBm
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Common mode rejection
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PCB ground as reference approx 20dB
Coax screen as reference? ? ? ? ? ?>55dB
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Noise figure approx 12dB
Bottom line
I don't understand why they added a 5V to 12v DC to DC converter in the bias tee, other than to try and physically copy the Nti loop, so that folks think they are getting the same design.
However, you do get a lot of hardware for your money, but the overall performance is pretty mediocre.
I think the very simple two transistor "Improved M0AYF" is likely to be a better performer (though not 'stellar'), as the MLA-30 IMD figures are dire.
Circuit to follow
Regards,
Martin - G8JNJ
