The FT-736 with SDR Console or Pocket RXTX

All the FT-736 enthusiast know, that this old radio from the 80’s of the last century is not able to do all the fancy stuff from today. But it is a very good satellite radio and I still use it for that.

Even though I use also the the IC-9700, I was curious, if I can do some workarounds to put the FT-736 in a “modern” environment.

The FT-736 with a panadapter

Ok, this is not a new one, but that is the first step to get more flexibility with this radio.

The radio has an 13,69 IF frequency. I found a mod on Mike, DK3WN, wonderful webside. The surgery at the open heart on the FT-736 looks a little bit awful – but hey, there are no smd and a lot of wires.

I connected an SDR Play RSP-2 at the IF from the FT-736. So I have also the Panoramic view over the whole IF spectrum -  30kHz bandwith… For some satellites, it is ok, but not really enough.

The RSP-2 has an second antenna connector. Over an antenna matrix, I can switch between direct RX on the FT-736 (with the panadapter) or I switch the RX antenna to the second antenna port of the RSP-2, where I have a huge bandwith. (In case of transmit, you have to know what you do…!)

This solution is ok. But not usable with doppler correction to turn the TX VFO on the right frequency. The main requirement is: Click on the signal in the sdr console, and the FT-736 switch on the right TX frequency including the doppler correction.

 

FT-736 Sat mode with the SDR Console

So this was the bigger challenge that I expected.

 

The main problem is, that just a few of applications use the protocol to “talk” with the FT-736 - the SDR Console not.

 

So I had to find a way, to send the frequency from the SDR-Console to the FT-736 with the right uplink/downlink combination including doppler correction.

 

I explored my pc and try to figure out, how the different applications talk together. And yes, there is a way to manage my requirement with all the stuff. Following Software ar needed: SDR Sonsole, VSPE, SatPC-32, Wisp DDE (all links see below at the end)

 

The concept is like this:

• The SDR Play and the FT-736 use the same RX antenna simultaneous (be very carefull with that!)

• I use the modul “external radio” in the sdr console. This modul use the integrated Omni-Rig and submit the RX Frequency 

• In Omni-Rig, you have to select the FT-847 radio

• Omni-Rig sent the RX QRG via a vitual serial cable (Pair in VSPE) to SatPC-32

• In SatPC-32 is only 1! Radio selected: The FT-847. SAT-PC32 means, that the RX frequency is from the VFO of the FT-847 and calculate the right Uplink frequency

• This frequency pair sent SatPC-32 via the DDE Interface to WISP-DDE

• WISP-DDE communicate via the CAT Interface to the FT-736 radio.

 

So you can select a signal on the sdr console and the FT-736 switch to the right frequency in Uplink and Downlink. Keep care with this solution (Read DK1TB, Erich’s warnings in the help file for the FT-736)

 

 

Before we look deeper in the configurations, here is the concept, how I integrated the SDR receiver in the 2m/70cm system. (Before I got the IC-9700. No I use the FT-736 in a similar configuration for QO-100)

 

 

 

Some important Settings:

Omni -Rig

In my computer, the lowest Poll interval is 200 ms. Shorter intervals trigger a “spooky” behavior on the SDR Console.

Really important: The Baud rate have be the same in the SatPC-32 application.

VSPE (Virtual Serial Port Emulator)

 

I tried the connector. It works, but triggered also the same “spooky” behavior in the SDR Console like the short Poll interval.

So the best way is to use a “pair” between two virtual com ports to connect SDR-Console (Omni-Rig) with SatPC-32.

 

SatPC-32

 

In the radio setup, please ensure that you use the same baudrate which you set in Omni-Rig. You have to use only "Radio 1" with the FT-847 radio. Please leave "Radio 2" blank

 

An important setting is also in the CAT tab from SatPC-32.

Set the Speed at “x10”. That set the latency on a minimum.

 

WISP DDE

 

I’m so happy, that this old interface still works perfectly on win10.

The Ft-736 is set up as Radio 1

   

 

WISP DDE Radio Settings

 

In the Radio settings, it’s important that the maximum baud rate is not higher than 4800 (Back in the 80s, it was an amazing speed…)

To get the latency down, set the command delay on a minimum. On my pc it is 20ms.

 

 

Remote the FT-736 in SAT mode with Pocket RXTX

YO3GGX wrote an app, which allowed to remote several RIG’s. Unfortunately, the FT-736 is not in the repository. But now you know, there is a way with the FT-847.  ;-)

 

Instead of the SDR Consol with the Omni Rig, we use now JAReC for communicate with the SatPC-32 and the Android App Pocket RXTX on you phone or tablet.

In addition, JAReC is also the audio interface between Pocket RX/TX and the FT-736 and control the PTT.

For the common settings in JAReC and Pocket RXTX, please read the online manual on YO3GGX webside.

The handicap of this solution is, when you will change the sat in SatPC-32, there is no remote solution for this software. Except via Remote Desktop, but then it’s not possible to change from mode U(V to V/U or contrariwise. (It’s a manual switch on the radio).

 

What's next?

I use the FT-736 exclusively for the QO-100 satellite. For the others, I have the IC-9700 in use

Now I search a way to use SDR-Console and the Pocket RXTX simultaneously. But there is no way to get a data stream from two different COMport in to one COMport (From SDR-Console and JAReC to SatPC-32) A minor solution is, that I steer the SDR-Console direct over CAT with JAReC (pocket RXTX). It works up to 999MHz with the TS-2000 protocol. But there are some “spooky” behavior. Maybe someone have an other idea.
Further I observe, that WISP DDE is sometimes not stable. I don't know, from where it is.

 

Conclusion

Yes it works! The radio was designed over 30 years ago. It is a little wonder, that it will running in this enviroment. It is really a great solution. But yes, the bottleneck is the long way over the several applications. In fact: The latency is sometimes to long.

Thanks to Erich , DK1TB who gave me some hints to optimize the system.

 

References