FT-1000D Subreceiver Antenna Modification
Note: this modification was developed by K0FF and shared with the Yaesu reflector
The goal with this mod is to modify the FT-1000D (or FT-1000 w/ BPF-1 option) for
independent operation of both receivers on unrelated bands and/or modes using the
main antenna and retain the ability to use a Beverage antenna on the RX ANT jack.
Of course, the 1000D already has the BPF option, it's just not hooked up right.
A little history:
The FT-1000D has 2 receivers, 2 audio channels, a common squelch and an S-meter
on the main receiver only. When an internal switch (S1001) is in the RX ANT
position, the main receiver can pick up it's signal from the antenna hooked up to the
transmit antenna jack (SO-239) or a separate receive only jack (RCA pin-type), and
can be switched between the two via a front panel switch marked "RX ANT". The
Sub receiver listens in on whichever antenna the Main one is hooked to, and also
must use the Main receiver's BandPassFilter (MainBPF). This limits frequency
excursions to the same band.
The sub-receiver has it's own Band Pass Filter section, which has it's own antenna
input jack (SO-239), but can only use those when you take the radio apart, and
operate a slide switch "S-1001" to the "F BPF" position. Of course this means you
must ALWAYS use a different antenna to receive on or you can still operate the RX
ANT switch, and it will listen on the Beverage hooked to the RCA jack. You lose the
ability to listen on the transmit antenna. Also you lose the ability for the Main
Receiver to pick up the Beverage!
The mod moves the control of relay RL1004 the front panel, brings the TX antenna
on the receive side of the TR switch out the back, and ties that back into the BPF via
a small jumper. This way you can listen to 2 separate bands on the transmit antenna
(say 10 and 20 on a triband beam), and not lose the RX Ant (BEV) function.
Fortunately these functions are all controlled by relays, and they can be split, and
operated independently. In the old days we would get out the soldering iron (gun,
actually) and an electric drill, and just do it. Today we have to preserve resale value,
so no extra holes please!
Mod consists of adding 2 Jumpers, remove one plug, and remove one resistor. You
will also need a 6" coax cable with PL-259 one end, RCA plug opposite.
You lose the DIM (display dim) button function on the front panel , and also the
Monitor scope 73Mc IF output jack function on the rear apron. (do they even make a
monitor scope??) No functional loss to the radio at all, and you gain the ability to:
A) Use the sub-receiver with a separate antenna connected to the BPF option's SO-
239 on any band. (great for "Antenna Diversity Reception" - I use this approach on
6M with transverters).
B) Use the sub-receiver on any band/mode using the main TX-RX antenna,
independent of main receiver's band/mode.
C) Connect a different receiver to the FT-1000D, outboard style, using the main TX-
RX antenna. (an adaptation to the mod would allow the outboard RX to share the RX
antenna too, if desired)
D) Use the main receiver on either the TX antenna, or RX antenna while doing any
of the above.
The reason I did it was to listen to the 28.885-6 meter liaison frequency concurrent
with the 14.345 EME circuit. You may want to run a VHF/UHF receiving converter
into the sub-receiver as a 14 Mc i.f. to monitor some important calling frequency, or
propagation indicator, while chasing DX on 2M EME via a transverter with a 28 Mc
i.f. .....the possibilities are endless.
WHAT you are doing is freeing the wiring from the DIM button, rewiring the DIM
button so as it will operate relay RL1004 on the "RF UNIT" board, effectively panel
remoting switch "S-1001", and providing a connection to the outside world for the
main antenna from the receive side of the TR relay, via the abandoned IF jack on the
rear apron.
HOW:
First lets get at the DIM switch on the front panel.... Remove both top and bottom
covers. Remove all the screws holding the front panel/display in place. Remove the
small circuit board that contains the MOX-VOX-DIM switches. There is a socket
and plug going there for the switch marked DIM (has 2-pins 1-red wire, 1-white
wire). Remove the plug, and tape it back out of the way. We won't use it for
anything, just save it there for retro. This leaves the switch free, and it already has
one side going to ground through the pcb wiring. Leave all that alone, and solder a
long lead to the other terminal. The one that switches to ground when you toggle the
button. This wire gets routed all the way to the bottom rear of the radio to the corner
near the grounding lug. The board we are working on is the one in that corner, and
has a large flat, silver box on it. That's the "RF UNIT".
In the far back corner on the top of the board are some relays. The one we want is
marked RL1004 and there is a diode across the coil, D1050. Solder our wire to the
anode end (the end opposite the line). Be careful here. The other side goes to +13, so
check this out carefully beforehand. Simply pushing the DIM switch in will now
activate the relay, and releasing the switch will deactivate the relay. Not Rocket
Science but be careful.
At this time make certain that "S1001" is in the R ANT position where it will always
remain.
Next we have to loosen the "RF UNIT" board and turn it over to do the jumpers. You
will have to remove some screws, and take a few plugs loose. Label everything or
make a chart so it gets back in the right place. Not everything needs to come loose to
do this. Turn the board over and examine the area around J1013-1, the IF jack, in
The cluster of four RCA pin jacks on the rear of the board. On the solder side of the
board it series connects to a chip capacitor, and then a zero ohm chip resistor.
Remove the chip cap and store it for retro. This effectively frees the jack up so we
can run a short jumper wire from the center pin of it, to the center pin of the little
coax jack J 1005, which is next to RL1001. That's how we bring the main antenna
out of the set and send it to the outboard receiver, or in our case to the sub BPF filter
unit.
That's all, very carefully put it all back together again. Install coax cable jumper
between the (old) IF jack and the SO-239 on the BPF filter. Now you can experiment
with the functions.
The panel switch RX ANT continues to take the main receiver between the T-R
antenna and the RX (Beverage) antenna as before. The DIM switch now puts the sub
receive between being slaved to the main BPF or it's own BPF. The coax jumper on
the back brings T-R antenna back out for the sub BPF if desired (and it will be most
of the time). Note that you can still use the sub-receiver on the Beverage also, but
only when the main is too (stock condition). This is the place where you could add
the adaptation I mentioned in step (C) above, but I see no scenario where you would
want the sub on Bev without the main on Bev also. If you have an individual need
for this, contact me.
This effectivly puts the 2 receivers in parallel across one, antenna, and though some
loss might be inroduced by double loading, signal generator tests show that they are
negligible.
I have tried this and it works but make no recommendations as to the suitability of
this mod. I have tried to be precise but it is up to you to check for errors in
application or omission..
Throughout this and other tech notes that I write, I use the unit Mc/s or Mc. If you
can only deal in MHz, multiply by 10 to the minus 1, or I will Be glad to provide a
free conversion chart for an SASE to my callbook address.
This simple change should unlock the full potential of this fine radio., which was
arguably already the finest I.F. for VHF/UHF transverting.
Geo, K0FF
Note: A version of this mod was also posted by Barry Williams to the Yaesu reflector
One other change you may want to make to your FT-1000 is to add an
external antenna switch as suggested in the QST review of this radio.
This will be useful if you have the BPF-1 option. With this
modification you will be able to select the either the main antenna or
the BPF-1 antenna for the second receiver by using the front panel
switch. The switch added in this mod will allow you to select either
the main antenna or the antenna connected to the phono jack for the main
receiver, this is useful when using receive loops or converters. I
connect a Butternut HF-6V to the BPF-1 and my KLM LPDA to the main
receiver. I also plan to add a receiving loop for 80 and 160 connected
to the phono jack. This allows diversity reception by polarity,
frequency or mode.
In order to do this you must select the "E BPF" position on switch S1001
on the R.F. unit and add a switch between one end of S1001 and a pad on
J-1007. Remove the covers from the radio and access the R.F. Board as
in the manual for setting switch S1001. Remove the three screws holding
the connectors for the R.F. board to the rear panel, the six screws
holding the R.F. Board down, and unplug the three coaxial cables which
go to the R.F. Board. Remember where these cables were connected. Put
S1001 in the E-BPF (Enable BPF-1?) position. Lift the board so you can
access the bottom. Cut two twenty inch lengths of number 24 wire (or
smaller) and solder one end of one wire to the pad under S1001 opposite
the switch handle when it is in the E BPF position. Solder one end of
the other wire to the pad under J1007 which is near S1001, and is not
connected to the center of S1001. Route these two wires through the
hole near the center of the rear of the radio. These can then be
brought out through the grill on the rear of the radio. I mounted a
miniature SPDT switch in the grill, and connected the wires to it. When
these wires are shorted the main receiver is switched to the antenna on
the phono jack. Replace the screws and connectors, and try everything
out. You can then replace the covers.