b97 Shinwa (Zodiac) MA452 70cm mods
Troubles to cure. It is also a reliable UHF rig - with only one exception. After some time (probably a year)
the squelched audio on my 3 transceivers fucked off. So when you know it, it is a good idea to take out the audio
at at earlier stage, as shown on the circuit diagram.
Receiver insensitivity: The receiver isn't so sensitive, but it is easy to improve. You just remove one section
of the input VHF filters. This improves the sensitivity from 1ÁV @10dB quieting to better than this for 0.5ÁV.
Xtals. TX xtals are around 36MHz. I used LO above RX since it is easier to retune the circuits, but it may cause
image interference from the NMT-band, so it must be considered, RX xtals are around 49MHz.
How to calculate xtal frequencies:
RX alternative 1: (433 -10.7)/9 = 46.92222MHz
RX alternative 2: (433+10.7)/9 = 49.3000MHz
TX: 433/12 = 36.08333MHz
see the following
article in Norwegian:
SHINWA MA-452 UHF Pakkeradio med- LA8AK AR 90-04-142