[RSM] Serial Port Testing Question

Thu Feb 5 16:51:44 EST 2026

Hi, Ed:

Thanks for your suggestions. I did look closely at all menu/functions 
settings and the only thing relating to the com port is for data 
transfer from one rig to another. It's an on/off function but has no 
effect on computer control. I've never seen mention of firmware upgrade 
by anything but replacement of the ROM chip in the TS-570D. It's not 
mentioned in either the user or service manuals for the rig.

I did pursue the problem further and got deeper into command strings  
than I ever desired. 😉 When using a serial port monitor program I can 
see commands sent to the rig and the rig responds. When the rig in on 
14.245000MHz I can send the command "FA00014230000;" and the rig changes 
VFO A frequency. It reacts to any other commands I send but never 
returns any strings in response. The VFO A frequency query "FA;" results 
in silence and any, similarly, changes made on the rig's control panel 
are not sent to the serial port.

I did try to see what data is sent by the rig when it is powered up. I 
was not able to monitor the serial port and have N1MM running 
simultaneously (port conflict) so monitored the port assuming it's 
behaviour doesn't change. When monitoring the port at the moment the rig 
is turned on I see a  "command string" (generous description) ".." which 
is two periods and nothing else.

All that effort simply verifies my suspicion of a failed RS-232 port but 
it is interesting that the failure is one way. On the groups.io TS-570 
site I have seen mention of people replacing the serial port chip but 
have not dug into that possibility. I see nothing in either the TS-570D 
user or service manuals that even mentions the location of the chip on 
the rig's circuit board.  If it is an LSI chip I probably would not 
trust myself to attempt the repair.

We do have another rig that we could put in service if we really had no 
choice. It is a KN-990C, which is a multi-mode, open-source, Chinese DSP 
HF rig. It worked beautifully in both the RAC Winter contest and the 
NAQP SSB Sprint but it is just QRP and has a tiny display that I can no 
longer see easily. 🙁

Thanks for the input and I'll keep investigating my possibilities.

73,

On 2/3/2026 8:15 AM, ve4ear at gmail.com wrote:
> Hi Jack   I am sure you have considered this, but I will throw this out there.
> 	1. Is there a menu setting to enable/disable the com port?
> 	2. Has there been a firmware update for the radio?
>
> Would you be able to monitor that PC's rx data through a terminal program and see what is dumped on power up of the radio?
>
> Ed
>
> -----Original Message-----
> From: RSM <rsm-bounces at contesting.com> On Behalf Of Jack Parker
> Sent: February 3, 2026 7:23 AM
> To: Jessy Blanchette <ve4jbb at gmail.com>
> Cc: rsm <rsm at contesting.com>
> Subject: Re: [RSM] Serial Port Testing Question
>
> Hi, again, Jessy:
>
> I was finally able to acquire the bits and pieces needed to build the loop-back plug and verify my USB/serial adapter is functioning. The adapter and extension cable are fine but when I attached the cable to the TS-570D serial port it did not respond as expected. In looking at the data sent to and received back from the TS-570D ("FA;" sent and should have received the '570s frequency back) I saw there is no reply to the query. That sure does point to a non-robust RS-232 port on the TS-570D! 🙂 I tried data rates set to 4800/8/N/2 and 9600/8/N/1 with both DTR and RTS set to "handshake" but that did not help.
>
> There was one curious thing found when N1MM logger was configured for my rig. As expected, N1MM did not see the rig upon boot-up of the program.
> The frequency displayed was the default 14200.00 for 20-meter SSB. I decided to turn the rig off and back on while N1MM was running and, to my great surprise, I saw the correct rig frequency displayed even though N1MM still said it did not detect the rig. When the frequency of the rig was changed no update was sent to N1MM but the frequency was refreshed if the rig was turned off and back on. It appears I may have diagnosed the nature failure in the serial port. That would be the "FA;" command not being received by the rig while the rig automatically sends the frequency data string when powering up verifying the  data line from the rig to the computer is functioning when there is a command to send. That is not of much assistance because it's doubtful the serial port could be repaired in the field, especially by someone who no longer has the tools to do the job. At this point about the only thing I could hope to do is figure out a way to manually tell the '570 to send frequency data like it does on power-up.
>
> That's where matter stand at present. Thanks for your assistance!
>
> 73,
>
> On 1/26/2026 3:35 PM, Jessy Blanchette wrote:
>> 100% correct on a straight through cable.  If you have a null modem
>> cable (crossover) it's for connecting PC's to each other (DTE data
>> terminal equipment).
>>
>> If you do have a null modem cable in the junk box you can test serial
>> ports between serial ports on a PC (like COM1 to COM2)  with putty on
>> each comm port.
>>
>> I would be very surprised if the serial port on the rig isn't working
>> -- rs232 is pretty robust.
>>
>> On Mon, 26 Jan 2026 at 14:20, Jack Parker <vhfplus at gmail.com> wrote:
>>
>>      Tried PuTTY and it did not work. I must find a DB9 connector and
>>      build a loop-back test jig. AFIK the radio/PC cable should be a
>>      straight-through. Lots of bad info on the "interweb". ;)
>>
>>      I'll keep plugging away at this and hope the TS-570D's serial port
>>      is okay.
>>
>>      Thanks and 73,
>>
>>      On 1/25/2026 2:47 PM, Jessy Blanchette wrote:
>>>      Your welcome!
>>>
>>>      Another quick tip,  on the rs232 adapter or physical serial port
>>>      on the PC you can also do a "loopback test" jumping the TX and RX
>>>      lines together.  When the rx / tx serial lines are looped
>>>      ,whatever you type in Putty will echo back right away -- then you
>>>      know the host/pc serial port working ;)   If it's a one wire
>>>      test, make sure hardware flow control is disabled in Putty.
>>>
>>>      https://www.instructables.com/DB-9-RS-232-Loopback-Plug-Windows-and-OS-X/
>>>       overkill tutorial, but explains this in more detail.
>>>
>>>      73 es GL!
>>>
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--
Jack, VA4JP/K0JP
Steinbach, MB
EN19pm