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[Articles Home]  [Add Article]  

FT-840 CAT/PTT interface

Igor Anisimov (NN1I) on December 2, 2001
View comments about this article!

A Computer RS-232 port requires voltages between +5 and +15 volts for logical 0, and voltages between -5 and -15 volts for logical 1. However, the FT-840 CAT output voltages are TTL standard between 0 and +5 volts only. This radio requires FIF-232C interface that cost about $100. In addition, the FIF-232C requires AC power (not good, if you want to use this radio from a portable location).

You can make your own interace under $25, plus you can add computer controlled PTT option for use with PSK31, RTTY, SSTV and other digital modes sharing the same RS-232 port, and with no AC source required.

There was an article a while back on eHam.net about a similar interface for a Kenwood radio. However, that design did not work with Yaesu FT-840. I found out that the Yaesu radio TTL/RS232 converter did not need a logical inverter. Also, the FT-840 is not always listed in the configuration options for many computer programs. I will discuss some more details on that at the end of this article. I like the FT-840 radio because it is affordable and simple in operation. You can have even more fun with it, if you build this interface.

The heart of this interface is a MAX232A. You can use any similar chip MAX203, MAX232, or MAX233, but check their documentation for proper connections. The Power supply's +5 volts comes from voltage regulator 78L05 that takes +13.5 volts from the back of the FT-840 radio (RCA connector). PTT is controlled via optocoupler 4N33 by the RTS signal from RS-232. I used a DB9 serial port. If you use a DB25, then you have to change pin numbers according DB25 assignments. The Yaesu CAT plug is 6 pin Mini DIN.

The PTT circuit is optional. You don't need it if you just want to read radio frequencies and modes into your logging software. However, it is a good idea to share one serial port for CAT and PTT, if you use your computers' soundcard for digital modes. Make sure that you have configured your software to share the PTT and radio port, and set PTT control by RTS. Of course, you will also need a Rx audio cable to your soundcard, and a Tx microphone cable with an attenuator or an isolation transformer. More detailed information can be found on the web (www.qsl.net/soundcardpacket/cables.htm)

This interface was tested with Logger 6.11 (freeware by K4CY, www.qsl.net/kc4elo/logger.htm). It did not work with Zakanaka 1.24 stand-alone, because this software had limited number of radio types in configuration, but it could read the frequency from the Logger (www.qsl.net/kc4elo/). If your software does not have FT-840 listed in configutration of radio type, then try to use the FT-900 settings. It may also work with FT-890 settings, but with a slow polling rate. Besides radio type, you must set baud rate to 4800; 8 data bits; 2 stop bits; no flow control; no parity; and echo off.

73 Igor NN1I

Member Comments:
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FT-840 CAT/PTT interface  
by KJ6ETL on December 3, 2001 Mail this to a friend!
Great article :-)

Any idea how long the cable to the pc may be?
I would like to controll my rig from an other room.

Do I need seperate lines for audio?

73

Roger
 
FT-840 CAT/PTT interface  
by KQ2P on December 3, 2001 Mail this to a friend!

I have a home brew program for the FT-840 written in VB6 would be happy to pass along the source code to anyone that may want's to do there own custom program.
Lots of cool stuff, some of it half baked and BUGS included, but it's a good starting point for somthing better. contact me at gary_kq2p@msn.com
 
RE: FT-840 CAT/PTT interface  
by NN1I on December 3, 2001 Mail this to a friend!
I tried this unit with 6 feet RS232 cable. And it was OK for CAT. However, I could not make audio cables too long, especially microphone cable. I made a switch box for my microphone and the computer soundcard output. And I had a lot of interference in my audio, when I made the microphone cable 6 feet long. Later I had to use a short coiled cable instead. This switch box is only one foot away from the rig now. Of cause, all cables must be shielded. So, I did not have luck controlling the rig from more than 6 feet away, due to FRI in my shack.

73 Igor NN1I
 
RE: FT-840 CAT/PTT interface  
by NN1I on December 3, 2001 Mail this to a friend!
I meant RFI (Radio Frequency Interference)

Igor
 
RE: FT-840 CAT/PTT interface  
by NB6Z on December 3, 2001 Mail this to a friend!
The FT840 makes a nice little rig for the sound card digi modes! I own one of the first ones shipped from Japan and used it on the digi modes exclusively for 8 years until I upgraded to a FT920. See photo here: http://www.eham.net/data/profile/nb6z/photo.jpeg
If you have the CAT option working, you might as well get a copy of MixW V2.0 program to control the 840 and to operate all the popular digi modes. It is useful even if you don't plan to operate digital... You can use the built-in CAT macros and/or you can create new macros using the opt codes for the 840 found in the manual. You end up never needing to touch the radio except to turn it on (if you have an auto tuner installed). If you use the CAT for PTT, you don't need the PTT circuit shown in the article...
One NOTE about the FT840 for digi mode operation:
The main XTAL for the synthesizer is located too near the final PA. You will experience excessive drift when the internal fan comes on. To fix this, just add a some styrafoam, or other material, around the XTAL... No need to buy the optional TCXO ;-)

MixW is at: http://tav.kiev.ua/~nick/mixw2/
 
RE: FT-840 CAT/PTT interface  
by NN1I on December 3, 2001 Mail this to a friend!
I intended to build this interface, so my logging and soundcard software can read the frequency from the radio. Actually I am not using CAT program. Some soundcard programs must use PTT or VOX in order to transmit.

I recommend to use Logger by K4CY (check www.eHam.net reviews for this software). It has built in PSK31 and RTTY. K4CY also wrote Zakanaka for PSK31 and RTTY. Zakanaka may work as stand alone or it may be integrated with Logger. Actually Zakanaka is using MMTY engine for RTTY. MMTY is another piece of art by JE3HHT who also wrote MMSSTV (see QST August, 2001 p.61). It is all FREEWARE.

73 Igor NN1I
 
FT-840 CAT/PTT interface  
by KQ2P on December 4, 2001 Mail this to a friend!
Am Happy that there are other FT-840 users out there, itís a good radio, by the way my program
letís you control the frequency from the screen has up/down button and a nice fat VFO dial.
Still no takers for the source code, OH Well.
 
RE: FT-840 CAT/PTT interface  
by N4HRA on December 5, 2001 Mail this to a friend!
Does anyone have the same type of interface for the Icom 817?

Lew
N4HRA@mindspring.com
 
RE: FT-840 CAT/PTT interface  
by N4HRA on December 5, 2001 Mail this to a friend!
Sorry I ment Icom 718

Lew
 
RE: FT-840 CAT/PTT interface  
by NN1I on December 5, 2001 Mail this to a friend!
I am not familiar with ICOM IC-718. Some radios do not require this interface at all. Manufacturers can add an extra IC in the schematics of the radio. However, some radios need TTL/RS232 conversion, and manufacturers sell an optional inerface for about $90-140. This home brewed interface may work for this radio. The only way to find out is to build one. Of cause, you will have to figure out from the manual connections to the radio, and you will have to find 12 VDC sourse (may come from the radio also).
 
RE: FT-840 CAT/PTT interface  
by K0HZI on December 6, 2001 Mail this to a friend!
Re Icom 718. The CI-V level converter can be built using the same chip MAX232 or a few transisitors.
A lot less expensive than the Icom CT-17, CI-V level converter. See DF4OR web site:
http://www.plicht.de/ekki/civ/index.htm
 
RE: FT-840 CAT/PTT interface  
by NN1I on December 6, 2001 Mail this to a friend!
So, ICOM IC-718 has only one DATA pin on the radio side for data in and out. Interesting! Also as you can see some designs on the website

http://www.plicht.de/ekki/civ/index.htm

have +5VDC coming from the computer RS232 port (RTS, CTS, and DSR connected together). I have seen it before. MAX232 requires very little power, and it can be powered from other RS232 pins as soon as one of them has +5V state at least half of the time.
 
RE: FT-840 CATinterface  
by NB6Z on December 10, 2001 Mail this to a friend!
A low cost commercial alternative for CAT interface is at: http://home.att.net/~k1nu/k1nu/Products/control.html
 
RE: FT-840 CATinterface  
by NN1I on December 10, 2001 Mail this to a friend!
When I was looking for this interface long time ago, I did not know about the webiste

http://home.att.net/~k1nu/k1nu/Products/control.html

So, I had to make my own. It is true though that this interface may fit inside of RS232 connector, if MAX233 chip is used, because that IC does not require external components.

I don't understand why they said that their interface will work with FT-100 (Wow!). I always thought that FT-100 does not require FIF232C or similar one for CAT, and the manual does not say it.

73 Igor NN1I
 
RE: FT-840 CAT/PTT interface  
by KB5CCA on January 7, 2002 Mail this to a friend!
I would be interested in your CAT software program.
You can send it to me at kb5cca@hotmail.com.


Thanks,

KB5CCA
 
FT-840 CAT/PTT interface  
by VE3TMT on March 27, 2002 Mail this to a friend!
I just finished building this interface last night and aside from having the serial lines to the radio backwards all works fine. Really neat to change frequency and modes from the computer. Total parts not including case came to about $14 Canadian, less than $10 US. I used a ps/2 mouse extension cable for the CAT plug into the back of my FT900, and a length of the same cable for the RS232 -> DB9 side. What a slick little interface. I almost forked out $150 to buy the Yaesu model!!! Thanks Igor.
 
RE: FT-840 CAT/PTT interface  
by N0VJC on June 4, 2002 Mail this to a friend!
I have a good handle on the electrical interface and had thought of making my own as well. Can anyone recommend good (and cheap or free) CAT software that will control a Yaesu FT-980?
Thanks and 73,
-Steve Weidman
N0VJC
 
FT-840 CAT/PTT interface  
by KB8LFA on August 19, 2003 Mail this to a friend!
Has anyone built this simple interface?

http://www.orbitessera.com/html/body_doppler_compensation.html

It has 2 2n2222's and 5 resistors. No circuit board needed, just solder onto the db9 or db25, put the cover on and go.

I will be building one soon and was just curious of your input.

73, KB8LFA
 
FT-840 CAT/PTT interface  
by LU1LS on February 28, 2004 Mail this to a friend!
is possible use this interface in ft-80c (idem FT-747)???please sen email
sth@ciudad.com.ar
lu1ls
 
FT-840 CAT/PTT interface  
by LU1LS on February 28, 2004 Mail this to a friend!
is possible use this interface in ft-80c (idem FT-747)???please sen email
sth@ciudad.com.ar
lu1ls
 
RE: FT-840 CAT/PTT interface  
by VA2MJT on March 19, 2004 Mail this to a friend!
There is an old dos program at:
http://home.nordnet.fr/~llabourie/soft990f.htm
The name iof the program is: SOFT990
SOFT990 is a freeware designed for the transceiver YAESU FT-990. It is also running also with FT-840 FT-890 FT-900 FT-920 FT1000MP FT-1000D. MS-DOS real-mode or Win 3.1 are recommended.
Good luck!
Martin,va2mjt
 
FT-840 CAT/PTT interface  
by PA3HHO on October 11, 2004 Mail this to a friend!
I have the LCU-3Y CAT interface by www.wimo.com (with a conversion cable from 6 pin DIN to FT-840's mini DIN plug). This interface seems to be very similar to waht is described here, unfortunately I can't get it to work with e.g. MixW software and I don't have any other CAT software I can use with my FT-840. Does anybody have any suggestions / links to CAT software for my FT-840? Thanks! 73 de PA3HHO (pa3hho@amsat.org)
 
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