[GreenKeys] question on interfacing an ST8000

[eugene at hertzmail.com]

Thanks for note, Dino. Here are my responses (consolidated here).

The exciter is a harris RF-1310. It requires RS232 input for the FSK.
However, I suspect instead of +/-12V 0/+5 or 0/+8 would do fine. 

For the data terminal, I will likely use my PC (sacrilege!) So hyperterm
etc.  Or maybe MMTTY using com port instead of audio, I have to figure
it out.

Good point on the PTT function.  This could be very convenient. I assume
that once I start typing it will key the exciter etc.

I hadn't realized that the ST-8000 will convert from ascii to ITA-5. If
that is the case, then I can see a real nice benefit in using the
ST-8000 when transmitting. Sounds like I probably could use hyperterm if
that's the case.

I fully agree with you. On receive the ST-8000 is indispensable.  I was
trying to better value the transmit side when a transmitter natively
supports FSK keying with rs232 as input.

Thanks, Dino. Much appreciated!

Eugene
 


-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Dino Papas
Sent: Monday, February 23, 2009 8:54 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] question on interfacing an ST8000

Eugene -- some thoughts.  My ST-8000 is interfaced to my TS-940S via  
the 4-pin "Xmtr" rear-panel jack on the ST-8000; it's strapped for  
FSK (pins 1/4) and PTT (pins 2/3) [page 30].  It operates in the  
"open collector" FSK keying mode.

73 -- Dino KL0S

On 23Feb2009, at 8:17 PM, <eugene at hertzmail.com>  
<eugene at hertzmail.com> wrote:

> I've been reading the manual on the ST-8000 and planning for its
> interconnection in my station.  My question concerns the use of  
> FSK.  My
> exciter has an RS232 input for FSK data.  When it receives RS232 data,
> it will transition between mark and space frequencies as defined in  
> the
> exciter using dip switches to define the shift.

What kind of rig are you running?  A lot of the rigs with a "FSK" jack
only require a dry contact switch closure to toggle between Mark and  
Space
tones.  The ST-8000 will provide open collector, +5 V or +8 V keying  
and you
set the dip switches (S2 and S4) accordingly (Page 29).

> My question is this. If a transmitter already supports FSK as in  
> input,
> then why wouldn't I just connect my RS232-TxD line from my data  
> terminal
> to the FSK line of the transmitter? Why would I need the ST-8000 to  
> take
> the data input of the terminal and output the FSK data to the
> transmitter?

What kind of data terminal are you using?  Computer serial port or a  
dedicated
terminal device?  One reason to consider is that the ST-8000 will  
accomplish
the PTT function for you.

> Now, there are some reasons that I could envision. For example, if the
> data terminal only spoke 7 bit ascii and I needed to key the  
> transmitter
> for ITA-5. That would make sense. But I do not believe that the  
> ST-8000
> provides such a translation function of codes.  My understanding is  
> that
> my terminal software running on a PC (for example) needs to toggle the
> RS232 port in a 5-bit fashion for the ST-8000 to then toggle its FSK
> line in a 5-bit fashion. Right?

> Now, I know there are other reason why I might want to send my output
> data through the ST-8000 instead of connecting the RS232-TxD line  
> to my
> FSK input line on my receiver, for example if I were changing  
> speeds. I
> know the ST-8000 can do that (regeneration?).

Yes, the regeneration feature will convert Baudot to ASCII and vice  
versa
and do speed conversion as well.

>
> Bottom line though. Assuming I am not using any speed change function
> and assuming my PC terminal software can support toggling the RS232- 
> TxD
> line in 5-bit words (using the appropriate ITA-5 code) then am I right
> that the ST-8000 isnt doing much for me?


Well, if you're using the ST-8000 as your modem (for both receive and  
transmit)
then it in fact is doing everything for you.....again, need to know  
more about the rest
of your setup.  On receive you need the ST-8000 obviously to do the  
conversion
from audio tones to pulses to be decoded by whatever application  
you're using.


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