FT-1000D Rx Ant Mod
The goal>>>To modify the FT-1000D ( or FT-1000 w/ BPF 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 receivers 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 tou 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 Monitorscope 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.
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.
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.