Topics

Prepare for FSK help topic


Kenneth Williams
 

I have a question, or maybe a comment, about the 'Prepare for FSK' topic in the help contents.  Ultimately I would like to get some clarification and see the help file updated if appropriate. (I would even volunteer to do this)   Specifically, it is in regards to the polarity of MARK and SPACE with respect to the transistor circuit illustration.  What I read is:

With this circuit, when MMTTY sends a "space" (current off) the transistor switch is open and when it sends a "mark" (current on) the transistor switch is closed.

However my observation is that when MMTTY sends a MARK, the driver signal is low and the transistor in the illustration would be open.  This is opposite from what is stated.
Before I say that the help file is wrong, it is necessary to state that I made my observations on the line side of RS232 drivers and I do know that RS232 drivers invert the polarity of the signals.  For example, a logic '1' (5V or 3.3V, etc)  on the logic side becomes a negative voltage on the line side and a logic '0' on the logic side becomes a positive voltage on the line side.

So, I can see that statement about the transistor as being correct if referring to logic levels of MARK and SPACE, but the help file makes no mention about logic or line level inputs.

Am I reading the help file correctly?

Thanks


Kevin Rowett
 

as configured in this ckt, the transistor is an inventor.  Input polarity is opposite the output polarity.  (common emitter)


73, K6TD


On Apr 14, 2020, at 11:19 AM, ken.williams@... wrote:

I have a question, or maybe a comment, about the 'Prepare for FSK' topic in the help contents.  Ultimately I would like to get some clarification and see the help file updated if appropriate. (I would even volunteer to do this)   Specifically, it is in regards to the polarity of MARK and SPACE with respect to the transistor circuit illustration.  What I read is:

With this circuit, when MMTTY sends a "space" (current off) the transistor switch is open and when it sends a "mark" (current on) the transistor switch is closed.

However my observation is that when MMTTY sends a MARK, the driver signal is low and the transistor in the illustration would be open.  This is opposite from what is stated.
Before I say that the help file is wrong, it is necessary to state that I made my observations on the line side of RS232 drivers and I do know that RS232 drivers invert the polarity of the signals.  For example, a logic '1' (5V or 3.3V, etc)  on the logic side becomes a negative voltage on the line side and a logic '0' on the logic side becomes a positive voltage on the line side.

So, I can see that statement about the transistor as being correct if referring to logic levels of MARK and SPACE, but the help file makes no mention about logic or line level inputs.

Am I reading the help file correctly?

Thanks


Kenneth Williams
 

Yes, I also see it as that way.  To go back and parse the statement in the help file, I read it as:

"   when MMTTY sends a "space" [I observe a high voltage on space] (current off) the transistor switch is open [I read open as not conducting through C-E]" 

Since I see a high voltage on the line side during a SPACE, I would read the transistor switch as being closed, and not open as stated in the help file.  Am I confused (very possibly) or do I just have a different definition of open and closed?

Thanks for responding.

Ken


Joe Subich, W4TV
 

It depends on your transceiver. Some expect a low impedance to
ground on the FSK input for MARK, some expect a low impedance
to ground on the FSK input for SPACE. Most modern transceivers
(except some Ten-Tec and Kenwood) manufactured in the last
35 years or so have a normal/reverse switch or menu setting.

Given that, the exact polarity from MMTTY and whether the
RS-232 to FSK driver is inverting or not makes not one whit
of difference. It is simply a matter of understanding that
a typical serial port will generate +5 to +15V on Mark (0 to
-15 V on Space), knowing how the interface circuit modifies
that, and what input the individual's transceiver expects for
MARK.

The Help file in MMTTY can not be expected to provide specific
details for every transceiver manufactured in the last 35 years
nor for every variant of commercial and user constructed
interface/driver circuit - nor did I even attempt to do so in
the last revision of the help file.

73,

... Joe, W4TV

On 2020-04-14 2:19 PM, ken.williams@... wrote:
I have a question, or maybe a comment, about the 'Prepare for FSK' topic in the help contents.  Ultimately I would like to get some clarification and see the help file updated if appropriate. (I would even volunteer to do this)   Specifically, it is in regards to the polarity of MARK and SPACE with respect to the transistor circuit illustration.  What I read is:
With this circuit, when MMTTY sends a "space" (current off) the transistor switch is open and when it sends a "mark" (current on) the transistor switch is closed.
However my observation is that when MMTTY sends a MARK, the driver signal is low and the transistor in the illustration would be open.  This is opposite from what is stated.
Before I say that the help file is wrong, it is necessary to state that I made my observations on the line side of RS232 drivers and I do know that RS232 drivers invert the polarity of the signals.  For example, a logic '1' (5V or 3.3V, etc)  on the logic side becomes a negative voltage on the line side and a logic '0' on the logic side becomes a positive voltage on the line side.
So, I can see that statement about the transistor as being correct if referring to logic levels of MARK and SPACE, but the help file makes no mention about logic or line level inputs.
Am I reading the help file correctly?
Thanks


Hank Riley
 

If I get a chance I'll measure the serial output levels (others please do this sooner if you can), but if Ken is correct, I think the root of the problem with the help text is with its statements about what voltage levels come out of MMTTY, not with the transistor's switching action per se.  (be careful to keep the software switch under PTT & FSK called "Invert Logic" unchecked if you measure, even if you use that setting activated for your actual operating configuration).

No matter how you look at it, that part of the help file could be written more clearly and for that reason alone I would be in favor of reworking it.

I think people might be mostly concerned with just getting their RTTY setup to work and don't go into the details of inspecting carefully this part of the help file instructions to see if accuracy, clarity, and lack of ambiguity were achieved.

It would appear that total clarity and complete lack of ambiguity were not accomplished.

Hank


Kenneth Williams
 

Joe

Thanks for your responding and thanks again for your efforts that went into this because I know that a lot of effort goes into these things with absolutely no compensation.  But, you really put focus on  my confusion when you said "It is simply a matter of understanding that a typical serial port will generate +5 to +15V on Mark (0 to -15 V on Space)" since I am seeing a negative voltage on my serial port when a MARK is transmitted.

I put a scope on the serial port of my desktop computer (Old Dell 780) and I set MMTTY to drive both the FSK signal the audio out.  I then configured one of the macros to send a long string of '_' (MARK characters).  What I observed was a negative signal on the TXD pin of my serial port (-11V) and an audio signal of 2125 Hz (MARK).  This is different from you are saying I should expect so hence my confusion.  I will check my setup again this evening.

Regarding my rig, it is a Kenwood TS-570S so I know that I can change things around to get what I want, but I am just rooting around through all of the details to get a handle on things before I attempt to send.

Thanks

Ken  KC6PUQ

On Tue, Apr 14, 2020 at 1:50 PM Joe Subich, W4TV <lists@...> wrote:

It depends on your transceiver. Some expect a low impedance to
ground on the FSK input for MARK, some expect a low impedance
to ground on the FSK input for SPACE.  Most modern transceivers
(except some Ten-Tec and Kenwood) manufactured in the last
35 years or so have a normal/reverse switch or menu setting.

Given that, the exact polarity from MMTTY and whether the
RS-232 to FSK driver is inverting or not makes not one whit
of difference.  It is simply a matter of understanding that
a typical serial port will generate +5 to +15V on Mark (0 to
-15 V on Space), knowing how the interface circuit modifies
that, and what input the individual's transceiver expects for
MARK.

The Help file in MMTTY can not be expected to provide specific
details for every transceiver manufactured in the last 35 years
nor for every variant of commercial and user constructed
interface/driver circuit - nor did I even attempt to do so in
the last revision of the help file.

73,

    ... Joe, W4TV


On 2020-04-14 2:19 PM, ken.williams@... wrote:
> I have a question, or maybe a comment, about the 'Prepare for FSK' topic in the help contents.  Ultimately I would like to get some clarification and see the help file updated if appropriate. (I would even volunteer to do this)   Specifically, it is in regards to the polarity of MARK and SPACE with respect to the transistor circuit illustration.  What I read is:
>
> With this circuit, when MMTTY sends a "space" (current off) the transistor switch is open and when it sends a "mark" (current on) the transistor switch is closed.
>
> However my observation is that when MMTTY sends a MARK, the driver signal is low and the transistor in the illustration would be open.  This is opposite from what is stated.
> Before I say that the help file is wrong, it is necessary to state that I made my observations on the line side of RS232 drivers and I do know that RS232 drivers invert the polarity of the signals.  For example, a logic '1' (5V or 3.3V, etc)  on the logic side becomes a negative voltage on the line side and a logic '0' on the logic side becomes a positive voltage on the line side.
>
> So, I can see that statement about the transistor as being correct if referring to logic levels of MARK and SPACE, but the help file makes no mention about logic or line level inputs.
>
> Am I reading the help file correctly?
>
> Thanks
>





Joe Subich, W4TV
 

What I observed was a negative signal on the TXD pin of my serial
port (-11V) and an audio signal of 2125 Hz (MARK).
Are you using EXTFSK with the INV box checked?

I've been using MMTTY for nearly 25 years starting with two inverters
(resistor and 2N2222 (NPN transistor)) - one for FSK and an identical
one for PTT.

That configuration generally requires Kenwood and Yaesu transceivers
since the early 1990s (the FT-1000D/TS-940 era) be set to REV for FSK
transmit with Icom set to NORMAL. A couple transceivers - old Kenwood
TS-930 and Ten-Tec Omni V/VI - that do not have an "Invert" option
require a PNP transistor driver (non-inverting) for FSK. See:
<https://www.aa5au.com/rtty/fsk-interface/>

73,

... Joe, W4TV


On 2020-04-14 5:09 PM, Kenneth Williams wrote:
Joe
Thanks for your responding and thanks again for your efforts that went into
this because I know that a lot of effort goes into these things with
absolutely no compensation. But, you really put focus on my confusion
when you said "It is simply a matter of understanding that a typical serial
port will generate +5 to +15V on Mark (0 to -15 V on Space)" since I am
seeing a negative voltage on my serial port when a MARK is transmitted.
I put a scope on the serial port of my desktop computer (Old Dell 780) and
I set MMTTY to drive both the FSK signal the audio out. I then configured
one of the macros to send a long string of '_' (MARK characters). What I
observed was a negative signal on the TXD pin of my serial port (-11V) and
an audio signal of 2125 Hz (MARK). This is different from you are saying I
should expect so hence my confusion. I will check my setup again this
evening.
Regarding my rig, it is a Kenwood TS-570S so I know that I can change
things around to get what I want, but I am just rooting around through all
of the details to get a handle on things before I attempt to send.
Thanks
Ken KC6PUQ
On Tue, Apr 14, 2020 at 1:50 PM Joe Subich, W4TV <lists@...> wrote:


It depends on your transceiver. Some expect a low impedance to
ground on the FSK input for MARK, some expect a low impedance
to ground on the FSK input for SPACE. Most modern transceivers
(except some Ten-Tec and Kenwood) manufactured in the last
35 years or so have a normal/reverse switch or menu setting.

Given that, the exact polarity from MMTTY and whether the
RS-232 to FSK driver is inverting or not makes not one whit
of difference. It is simply a matter of understanding that
a typical serial port will generate +5 to +15V on Mark (0 to
-15 V on Space), knowing how the interface circuit modifies
that, and what input the individual's transceiver expects for
MARK.

The Help file in MMTTY can not be expected to provide specific
details for every transceiver manufactured in the last 35 years
nor for every variant of commercial and user constructed
interface/driver circuit - nor did I even attempt to do so in
the last revision of the help file.

73,

... Joe, W4TV


On 2020-04-14 2:19 PM, ken.williams@... wrote:
I have a question, or maybe a comment, about the 'Prepare for FSK' topic
in the help contents. Ultimately I would like to get some clarification
and see the help file updated if appropriate. (I would even volunteer to do
this) Specifically, it is in regards to the polarity of MARK and SPACE
with respect to the transistor circuit illustration. What I read is:

With this circuit, when MMTTY sends a "space" (current off) the
transistor switch is open and when it sends a "mark" (current on) the
transistor switch is closed.

However my observation is that when MMTTY sends a MARK, the driver
signal is low and the transistor in the illustration would be open. This
is opposite from what is stated.
Before I say that the help file is wrong, it is necessary to state that
I made my observations on the line side of RS232 drivers and I do know that
RS232 drivers invert the polarity of the signals. For example, a logic '1'
(5V or 3.3V, etc) on the logic side becomes a negative voltage on the line
side and a logic '0' on the logic side becomes a positive voltage on the
line side.

So, I can see that statement about the transistor as being correct if
referring to logic levels of MARK and SPACE, but the help file makes no
mention about logic or line level inputs.

Am I reading the help file correctly?

Thanks


Kenneth Williams
 

I connected my computer to a scope and I am seeing the same signals that I saw before; I am running a long sequence of MARK, the audio card is producing a nice 2125 Hz signal and the TXD line of  the serial port is low (-11V).  

- MMTTY version 1.70K
- 'PTT & FSK' of the TX tab is set to COM1.  This is a hardware serial port on the back of my computer.
       - Invert is NOT checked (Although, in experimenting with this, it seems to affect only the PTT signal)
       - The 'Radio Command' sub tab is configured to use port 'NONE'
- The 'Tx Port' selection of the Misc tab is set at 'Sound + COM-TxD (FSK)'
- The 'REV' button on the main window is NOT checked (Although I believe that this only affects AFSK)
- I verified that my scope channel was not set to inverted

Finally, I looked at the startup of a simple message (DE KC6PUQ ..)
  - TXD and DTR both start low (-11V)
  - RTS goes high
  - About 150 mS later, the audio starts with a constant tone as 2125
  - about another 250 mS later TXD goes high for the start of the first character

Thanks for taking the time to think about this.  Ultimately, this will not stop me from getting up and running as all I was really looking for was some consistency between the documentation and my observations.  I'm really just trying to get a handle on all of the pieces so that when I do start sending, I will be able to more quickly identify any problems.

Regards

Ken
KC6PUQ