Both Shirley and myself hold amateur radio callsigns
- Shirley holds callsign G7BUZ
- I hold callsign G6IXE
A term describing heavy pieces of junk which really do not deserve
anything more than being used as scrap metal.
I was given two items
which had once been used for analogue cellular radio R&D and
which had proven to be unrepairable. An HP141T Spectrum analyser and a
Schlumberger Solartron Stabilock 4040 communications test set. I
decided to go for the spectrum analyser first as it was likely to be
useful in repairing the communication test set.
HP141T spectrum analyser restoration
This is technologically a 1970's piece of kit but I think it remained
in production for quite a time as it it did its job well. It was
eventually superseded by the kind of computer controlled analysers I
was using at Philips Research in the mid to late 1980's. I
Schlumberger Solartron Stabilock 4040 communications test set
This is more mid-1980's and is for testing out pre-digital radio
communications kit. It came to me with a failed self-test and lots of
treble-beep error messages when I tried to control it from the keypad.
I describe fixing the problem here
Seavoice RT225 Marine
When I bought a yacht, it came fitted with a 1980-ish Seavoice RT225,
which is about one model newer than the type which has crystals for
each channel. It contains an interestingly designed synthesiser board
which relies on minimalist techniques to implement a PLL.
Inside are a set of CMOS divider chips , a prescaler and a phase
comparator chip. Channel programming is via a pair of 2716
It relies on the limited tuning range of a bandswitched VCO to minimise
the number of bits required to program in the frequency of
synthesiser for each channel.
It also uses one of the bandswitch diodes as a transmitter
modulation varicap (discovered when I replaced it with a PIN
diode and lost all of the modulation on transmit)
This type of design is capable of losing single channels over time due
to EPROM bit aging, or DIP switch creeping.
On the front panel is a 24 way 1 pole rotary switch, the position of
which is converted to a binary address and connected to some
the address pins of the EPROMS. In addition, the switch position is
directly used to enable a diode and dip switch 'ROM' which allows the
user to choose one of 16 marine channels for each position of the
The channel 16 override is provided for by having an additional address
pin and half of the contents of the ROM are programmed with
identical values for channel 16
The channel change switch appears to use Letraset to allow the user to
change the indicated channel number . These days one uses DTP or Corel
Draw or similar to place lettering on laser film.
The channels chosen were such that certain combinations of channels
As this I started this conversion in the days of
telephone calls and gunnery ranges in Plymouth Sound using channel 11,
I realised that for a cruise along the south coast of England
that I would need more than 24 channels , in fact more like
cover all of the channels that were used by Coastal Radio
So I sketched out the schematic of the radio synthesiser and then
proceeded to decode the ROM contents. After a bit of work the meaning
of all of the bits became clear. I even found a mistake in the original
programming of the EPROMS (or maybe they had faded away, after all the
radio is over 10 years old)
I then decided to fit an extra inner/outer toggle switch and use this
in place of the diode + switch ROM to define 2 different
groups, giving me the 48 I wanted.
I wrote a program in Acorn Basic to define new ROM contents and
re-programmed the EPROM
I then replaced the single LED illuminating the back of the channel
switch dial with a pair of rectangular LEDs connected also to
inner/outer switch with a piece of plastic between them, and
out a new dial in an Acorn DTP package. The result is that I have an
inner and outer set of channels and no more missing channel problems.
The only real issue is that the 'special UK' channel M2 is too high in
frequency for the set to transmit but it can be adjusted to recieve on
that frequency. The transmitter is disabled if the PLL fails to lock.
Of course now I only ever need to use less than 12 channels in total.
For all other traffic I use GSM900.
If anybody is interested in changing the channel assignments or
refreshing the EPROMS for this radio, please email.
Problems in 2006
I took a DSC course and then ...
The radio started jumping channels, and would tend only to receive a
channel for about 10 seconds.
I took the radio off the boat and looked for evidence of problems.
Of course the jumping problem only happened on some channels and these
were generally quiet in the evening (channel 72).
So I reprogrammed the EPROMS, converting the channel programming code
from BBC BASIC to C (and repaired the EPROM programmer which
eaten by a leaking NiCd memory backup battery) and the problem
I eventually traced the problem to a ribbon cable from the channel
change switch to the main PCB that has plugs at both ends. The end
nearest the channel change switch had been vibrated off the connector.
So I pushed the cable back on and put a cable tie round a loop in the
cable to keep tension on the cable to hold the cable plugged in. Back
to the boat for the fourth try ....
Hacking the Yaesu FT411
In 1998, I had the misfortune to drop my FT-411 in the sea,
myself with it.
I got over the near hypothermia in about 3 hours and then I noticed the
radio was wet and not working. Although it was in a waterproof bag,
this had split.
The radio was bought in Andorra as a European version. It came
After I had washed it thoroughly, totally dismantled evey module from
the motherboard, and replaced the odd component eaten away by leaving
the battery connected for three hours, I again had a working handheld.
The emitter lead on the low-battery detector transistor was the most
elusive to find and repair, as it was thin, vanished , and connected to
rail. All I did was connect a Zetex E-line device in parallel with the
Solder Jumper Settings
Within the FT411 there are 11 numbered solder jumper
The positions 3,5,7,9, and 11 are connected in my version.
These are accessed via removal of the screw holding down the screening
can over the microcontroller and desoldering the two joints holding it
down. Then carefully lifting the 24 way flex cable, while keeping a
finger on the soldered end.
- If connected in place of 3, the dial tunes the American
band (wont work, wrong RF module).
- If connected in place of 3, the dial tunes the 430-440MHz
(wont work, wrong RF module).
- If disconnected, unit powers up on 144-146MHz only.
- If connected in place of 3, the dial tunes the 1296MHz band
work, wrong RF module).
- One of these jumpers is connected for continous tone or
- If connected, the lithium cell is in circuit. It is
a series resistor that stops you blowing things when the unit is reset
Full Reset Procedure
Turn off unit.
- Short out both ends of the component at upper left of
microcontroller (marked 475 with a white band).
- Power up unit. If the jumpers are as in my unit, the
show 1.000 and a flashing 1 in the top LHS.
- Type in lower receive frequency limit (1440) to 0.1MHz
, Rx/Tx in range 140MHz to 174MHz seems to work.
- Press VFO. (upper left changes to flashing 2)
- Type in upper receive frequency limit (1460) to 0.1MHz
- Press VFO. (upper left changes to flashing 3)
- Type in lower transmit frequency limit (1440) to 0.1MHz
- Press VFO. (upper left changes to flashing 4)
- Type in upper transmit frequency limit (1460) to 0.1MHz
- Press VFO. (Get VFO A indicated)
If you mess up, power down, reset and start again.
I have just replaced the batteries in 2006 as I have started
it again. I went from 10x 700mAH 2/3 AF NiCd to 8x1800mAH AA NiMH in
the same volume battery pack (well actually the Dremel tool was used to
thin down the casing of the pack to make it easier to fit the cells.)
Page © Mike James 25th November 2006