These modifications of ancient Mobira radios are meant for licensed radio
amateur use.
In addition to this modification you also need the ham software
forthe radio.
If you don't know where to find it, tough luck...
These modifications are given as an example of a modification.
Your rig
may have different components, their tolerances may be somewhat different and so
on.
Please do not blame me if this doesn't work in your radio.
Make the
stub a little bit longer.
I used a minidrill and an exacto-knive.
Second
photograph, just that you get the picture...
There is a
feedthrough hole, that you must drill open.
After this modification, the TX
PLL lock range was 428-443 MHz.
The same method is
used for RX PLL as well.
There is no need of changing any components.
Cut away as indicated with red lines and
connect a PLL voltage test lead
as indicated with yellow.
To measure the
correct in operation PLL voltage,
you must close the cover.
This seems ok...
...and this is also normal.
To enable sending of
CCIR tones cut the trace indicated with red
and connect it to the next trace
on the board.
This modification is necessary only if you want to emit CCIR
tones.
The second part of
the CCIR modification involves cutting a trace
between two pins of a diode
as indicated in the picture,
adding 100k and 1k resistors and a 100n
capasitor. As you see
the component values are not exact, but who cares.
The yellow lead goes to the middle pin of the IC.
This modification is
necessary only if you want to emit CCIR tones.
This jumper is to
activate external PTT.
There is a +12V and
open collector output
for a relay that will pull when TX is active.
You
may want to remove the 1nF capasitor as I did.
The place where the capasitor
was is circled in the picture.
You must also cut the lead in the handset
connector
which is connected to the collector of the
transistor as the
handset pulls the line to 8V.
To change the TNC
connector to BNC you must open one screw.
I used double sided tape to fix
the TX/RX relay to the rig.
Remeber that the
power hybride is not linear.
Install a low pass filter (better than this
one) to get rid of the harmonics.
© 2000 OH3NWQ (both the photos and the text)