FTDX9000D - PA switching according to VFO-coupled transmitter

 

 

Hallo all FTDX9000D users.

 

FTDX9000D has unique possibility to works in duplex mode.

One can listen on two different bands, on two separate receivers of FTDX9000D and transmits on frequency of VFO A and simultaneously receive on different band, on VFO-B. It is close to SO2R station using only one transceiver. In SO2R (that can be an abb. of Single Operator Two Receivers) an operator should transmit only one signal - using first or second radio (2R). FTDX9000D transmitter may be coupled with VFO A (main receiver) or VFO B (second receiver). It can be done manually or by software like N1MM logger. Unfortunately there is no separate PTT or BAND DATA outputs for both VFO's so if one would like to use two power amplifiers for two VFO's (for two different bands and antennas, for example - VFO A at 7MHz/ant. port 1/PA and VFO B at 21MHz/ant. port 2/PA) using PTT and/or BAND DATA cables, both amplifiers will go TX when transmitter become active on VFO A and simultaneously receiving ability on VFO B will be disabled.

To solve this problem one needs an information for which one VFO transmiter is coupled. The easiest way is to use a signal from TX status LED located close to VFO knob of VFO B. TX VFO B LED has a easy access. When LED is OFF (transmitter is coupled to VFO A) there is 3,7V on its cathode. When LED is ON (transmitter is coupled to VFO B) signal goes to 0V.

Using 10k resistor, signal may be conducted to rear panel and used to switch PTT and/or BAND DATA 1/2 information for amplifiers.

Use transoptor and NPN transistor-key for relays switching or any other switching circuit.

I find out that chain of transoptor, then npn-key and relays for BAND DATA 1 (A,B,C,D) is fast enough to inhibit QUADRA band change when transmitter goes from VFO-A (location of QUADRA) to VFO-B (second PA). Really nice :-)

This mod works with fully loaded FTDX9000D and Quadra amplifier (Quadra on VFO A) and any other ptt-keyed PA on VFO B (or BAND DATA 1/2 controlled PA).

Documents related:

FTDX9000 service manual p. 9 (SW-J pcb location)

FTDX9000 service manual p. 359 (SW-J pcb schematic diagram)

FTDX9000 service manual p. 362 (SW-J pcb view) TX VFO-B diode - D9764.

D9764 is powered by R9764 and +5V. LED become active when LED driver Q9957 leg-6th (p. 379, LINK pcb) grounds its cathode. To conduct this mod one has to remove all walls of transceiver cover, unscrew front panel (four screws at sides of device - FTDX9000 service manual p. 3, screws no. 3) and remove some white wire tapes/other cables carrefully to get free access to rear side of SW-J pcb.

There is no need to remove any knobs from front panel.

Solder mask has to be removed from trace at rear SW-J pcb side (top left corner, close to pcb mounting screw), it is a point where copper path goes through a pcb to the TX-VFO-B LED cathode on front side of SW-J pcb (close to R9764).

It is a really small point of copper so good soldering skills are needed and use a small-end-tip of soldering device.

A good way is to use 10k SMD resistor to sample LED-cathode voltage and 10n ceramic capacitor soldered to ground. Usable current of signal from 10k resistor is high enough to power a diode inside a most popular transoptors without any changes in operation of TX-VFO-B red-coloured LED.

Back side of SW-J unit, arrow shows a place where solder mask should be gently removed and 10k should be soldered to sample a LED voltage, capacitor should be soldered to ground and 10k resistor.

Now - using ptt and/or band data 1/2 switching circuit, good pass-band filters and two independed power amplifiers connected to different antenna ports of transceiver one can listen two different bands, switch transmitter to desired VFO, calling CQ on VFO A and searching for multiplayers on VFO B. If an multiplayer is found on VFO B just move TX from vfo-A to vfo-B and call him using second amplifier keyed by switching circuit. Unfortunately there is no posibility to RX on VFO-A when transceiver is transmitting on VFO B but anyway it is a huge improvement of any contest station and it is just impossible to focus on receiver at VFO-A when transmitting short exchange at VFO-B :-)

FTDX9000D has some disadvantages related to some birdies and little elevated noise level when simultaneously TX and RX but it is not a big deal in contest enviroment, especially on lower bands. Other irritating issue is that internal voice keyer used in duplex mode blocks sub-receiver (VFO-B) and blocks SO2R at all ! It looks that Yaesu enginers didn't know what SO2R is when radio was in project phase. Due to this problem, one has to use logger-voice keyer. Remember about separation of audio patch from line-out of computer's sound card and mic-in (or patch) of radio or RF clipper if used.

 

If one decides to perform described mod -
will do it on own risk.

 

Idea of small pistol contest station using big toys.

 

BUT ...

 

Two power amplifiers are not necessary. Because only one of them is active during transmision, I designed simple coaxial relays net to use one amplifier and two radios (or one FTDX9000D). My point was to keep the same antennas connected to radio (radios) at particular band. If RADIO 1 uses 160/80m vertical and RADIO 2 uses tribander - thes same antennas should be used when RADIO 1 or RADIO 2 transmits using the same power amplifier. It is clear that in one PA version of station showed above, BAND DATA 1/2 shouldn't be switched but an information about TX-VFO (A/B) coupling is essential for antenna switching box. It is true for real two radios operation but here one needs information where PTT is active (RADIO 1 or RADIO 2). For best ports separation in PA-SO2R box, coaxial relays should be used and best shielded coaxes like semirigid or double-shielded teflon ones. There is just one dissadvantage of it - short intterupt of receiving when box is switching antennas. It happens when one changes TX-ready between radios or VFO's. It is short time and depends of switching-time of relays (10-20ms for most of relays). This is not a solution for top-contest RTTY/CW SO2R station. It may be good for SSB. I didn't test it in RTTY/CW but for a speed of qso I saw, real SO2R should be better. It is OK for somebody who has full duplex radio and wants to try use it in SO2R mode at phone contests. There are amplifiers on the market ready for SO2R like Prometeus or Expert 1K-FA. Fast switching (virtually immediate) may be done by PIN diodes suitable for high power switching.
After first test I can say that moment of switching is hard to notice. Works great ! If you want one - click on picture below.

SO2RBOX for you

Matt SQ7D (ex SQ7DQX)

FTDX9000D, SO2R with single radio, yaesu FTDX9000D so2r