VF - yep, voice frequency, typically relates to 4 kHz wide audio channels, well the channel
bandwidths involved with the channels on the regular frequency division multiplex systems
used by the telcos.  The actual audio bandwidth was somewhat less, more like 300Hz to
3400Hz.

The slow speed AP circuits were 66WPM, again, which was handled by the Lenkurt 25A
system without any problems.   

As best as I remember, the 25A system at the Raleigh bureau had one circuit at a higher
speed, and memory is failing me at the moment, but I think it was the weather scroll data
for cable TV systems, the weather information displayed on the video of one of the
cable TV channels, maybe the channel guide?

What that Lenkurt specs indicate is that if the 25 channels were all 66WPM or maybe 24
channels at 66WPM and one channel was at 75WPM to 100WPM, it would work.   If all
of the channels were to carry 110 baud circuits, then the system had to have more space
between the channels, therefore the number of channels was reduced.

I had not thought about this for many many years.

Just dawned on me, while not totally applicable to the Lenkurt 25A system, check this
URL:

https://www.navy-radio.com/manuals/ics-vietnam/ICS-orientation-7009.pdf

Do a text search on FCC-19.   This is essentially the basis for the Lenkurt 
system.


Sheldon

On Sunday, February 5, 2023 at 09:49:15 AM EST, Jeffrey Golas <[email protected]> wrote:


This is awesome, thanks! So where I see a reference to "VF", like "VF Demodulator", is that "voice frequency"?

It also sounds like one they were using the Lenkurt gear they were using 110baud by then.

Jeff KC3GJX

On Feb 5, 2023, at 1:37 AM, Sheldon Daitch <[email protected]> wrote:


I can't speak for the UPI services, because I never worked for UPI, but I
did spend a year with the AP in the Raleigh bureau.

When my hometown radio station went on the air in 1960, the AP wirefeed
to the M-15 was a DC loop from the telco in town.  Just another copper pair.

Either in the late 1960s or early 1970s, the AP went from the DC loop system

The Raleigh bureau had the rack mount system for transmission, and as best as I remember, the
system had nearly all or all 25 channels populated.   Too far back for me to remember.

The AP had upgraded the slow speed wire circuits to 66WPM and the Lenkurt system didn't seem 
to have any problems with carrying those circuits at that speed.

Do a word search on the below link for a reference to the Lenkurt use by AP and UPI:



The AP typically used the stand alone Lenkurt box on the shelf below the M-15 or M-20.

UPI was a bit more modern as they typically used the Extel printers and the demodulator
was a card in the back section of the printer.  I don't remember seeing any Extel printers on
the AP circuits, but since it cost extra for the AP subscriber, maybe no one was willing to
pay.

The telco line was a standard voice grade circuit.  Far too many years ago, I was working at
a UPI station and the news director wanted to do live reporting from the county's election 
office and he also wanted the UPI feed.   I contacted the UPI and telco for the price to have
a second loop at that office and was, well, astonished at the price.  It dawned on me that the
UPI circuit was a simple tone multiplex system, I verified the audio with a telephone butt set
and decided the cheapest route was to simply have a copper pair from the telco from the 
radio station to the election office.  I took the UPI tone audio, back fed it to the telco loop, 
took the Extel to the election office for a test, it printed perfectly and I satisfied the need of the
news director for that election reporting.

Whether the tone demodulator was UPI or AP equipment, the unit was set up with one tone
filter card, with the frequency (or frequencies!) for the wire service the subscriber was paying for.

Sheldon

On Sunday, February 5, 2023 at 01:06:10 AM EST, Jeffrey Golas <[email protected]> wrote:


Were those demod units a particular make and model at all? Be curious to learn about them. Was it truely a standard pots line or a T1?

Jeff

> On Feb 4, 2023, at 9:55 PM, Harold Hallikainen via GreenKeys <[email protected]> wrote:
>
> When I worked in radio stations (1970s), the AP and UPI wire services had
> a bunch of different TTY channels on the single telco pair. The
> demodulator was tuned to whatever service you were subscribed to.
>
> I still plan on doing some experimenting with 850 Hz vs 170 Hz shift. I'm
> currently thinking that the error rate would be about the same on 170 Hz
> shift with use of either a limiter or dynamic threshold control. With 850
> Hz shift, I think dynamic threshold control would do better since the
> wider apart frequencies would fade differently (at least more differently
> than with 170 Hz shift). I think a fade of 170 Hz shift signal would
> frequently take both tones below the noise level while with 850 Hz shift,
> perhaps only one would go below the noise level at a time.
>
> My DSP TU ( https://w6iwi.org/rtty/DspTU/ ) has a simple error counter.
> The number of valid start bits is compared to the number of valid stop
> bits (in a software UART). With a high error rate, the ratio of valid stop
> bits to valid start bits will be lower.
>
> It would be interesting to also implement this on a computer for testing
> different terminal units under impaired channel conditions. I know the
> FTDI USB/UART bridge won't go down to 45.55 bps. It looks like hardware
> serial ports on PC compatible computers can hit 44.956 bps, so that would
> be something to try. The error rate would be the number of frame errors
> divided by the number of bytes received.
>
> Anyway, I think there may be advantages to 850 Hz shift with selective
> fading and dynamic threshold control.
>
> Harold
>
>
>> On Sat, February 4, 2023 7:30 pm, W2HX wrote:
>> Interesting idea. I'd be happy to test it. I can demodulate both shifts.
>> Very interesting experiment!
>>
>>
>> 73 Eugene W2HX
>> Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos
>>
>>
>> -----Original Message-----
>> <[email protected]> On Behalf Of Harold Hallikainen via
>> GreenKeys
>> Sent: Saturday, February 4, 2023 9:10 PM
>> To: Daniel Jones <[email protected]>
>> Cc: Greenkeys <[email protected]>
>> Subject: Re: [GreenKeys] ITTY 850 shift?
>>
>> I wonder if those tones (2 kHz +/- 425 Hz) are far enough away from the
>> 170 Hz shift tones that both could be sent on the same channel and the
>> terminal unit would demodulate the correct ones.
>>
>> Harold
>>
>>
>>> On Sat, February 4, 2023 6:57 pm, Daniel Jones wrote:
>>> As a fellow military user I concur.
>>>
>>>
>>>
>>> Daniel
>>>
>>> www.K6YIC.com
>>>
>>> HH#11973
>>>
>>>
>>>
>>>> On Feb 4, 2023, at 17:54, Nick England  wrote:
>>>
>>>
>>> Paul, definitely use these military tones and not the ham ones
>>> that
>>> Jim Haynes discussed. No one is running 850 shift any more except us
>>> guys running military gear. Our equipment is not retunable to the ham
>>> tones.
>>> Thanks
>>> Nick
>>>
>>>
>>>
>>>
>>>> On Sat, Feb 4, 2023 at 8:29 PM W2HX  wrote:
>>>
>>>        That would be cool! Center freq 2000 Hz, shift is +/- 425 Hz
>>> so that means the tones are 1,575 Hz and 2,425 Hz. Mark is low.
>>> Someone correct me if I’m wrong.
>>>
>>>
>>>
>>>
>>>
>>> 73 Eugene W2HX
>>> Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos
>>>
>>>
>>>
>>>
>>>  From: Paul Heller
>>> Sent: Saturday, February 4, 2023 7:58 PM
>>> To: W2HX
>>> Cc: Daniel Jones ; Greenkeys
>>> Subject: Re: [GreenKeys] ITTY 850 shift?
>>>
>>>
>>>
>>> Let me see what I can do. What are the frequencies for 850 shift,
>>> mark and space?
>>>
>>>
>>>
>>> Paul
>>> W2TTY
>>>
>>> ITTY:                      HTTP://INTERNET-TTY.NET:8000/ITTY
>>> ITTY100:              HTTP://INTERNET-TTY.NET:8010/ITTY100
>>>
>>>
>>>
>>> AUTOSTART: HTTP://INTERNET-TTY.NET:8030/AUTOSTART
>>> EUROPE:              HTTP://INTERNET-TTY.NET:8040/EUROPE
>>>
>>>
>>>
>>>
>>>
>>>
>>>>  On Feb 4, 2023, at 5:53 PM, W2HX  wrote:
>>>
>>>
>>> 
>>> Thanks, Dan. I can generate the tones ok. I was just hoping that I
>>> could get some news stores to print. It would be great if the ITTY
>>> powers that be could just pipe the same data to both a 170 Hz shift
>>> and an 850 Hz shift audio stream.  Dunno what is involved with that but
>>> just curious.
>>>
>>>
>>>
>>> 73 Eugene W2HX
>>> Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos
>>>
>>>
>>>
>>>  From: Daniel Jones
>>> Sent: Saturday, February 4, 2023 7:46 PM
>>> To: W2HX
>>> Cc: Greenkeys
>>> Subject: Re: [GreenKeys] ITTY 850 shift?
>>>
>>>
>>>
>>> I had a cast set up to broadcast tty over the internet.  Let me look
>>> this week and see if it’s still running on my site and the feed
>>> something into it at 850 shift.
>>>
>>>
>>>
>>>
>>> You can also change the settings on the itty software to the required
>>> tones to test it in-house.
>>>
>>>
>>>
>>>
>>>
>>> Daniel
>>>
>>> www.K6YIC.com
>>>
>>>
>>> HH#11973
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>>  On Feb 4, 2023, at 16:34, W2HX  wrote:
>>>
>>>
>>> 
>>> Anyone know if there is a URL for ITTY for 850 shift?
>>>
>>>
>>> 73 Eugene W2HX
>>> Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos
>>>
>>> ______________________________________________________________
>>> GreenKeys mailing list
>>> Post: mailto:[email protected]
>>>
>>>
>>>
>>>
>>>    Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>      2002-to-present greenkeys archive:
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>>>
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>>>
>>> ______________________________________________________________
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>>> Post: mailto:[email protected]
>>>
>>>
>>>
>>>    Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>      2002-to-present greenkeys archive:
>>>      1998-to-2001 greenkeys archive:
>>>      Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>>
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>>>
>>>
>>>
>>>  ______________________________________________________________
>>> GreenKeys mailing list
>>> Post: mailto:[email protected]
>>>
>>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>>>> 2002-to-present greenkeys archive:
>>>>>> 1998-to-2001 greenkeys archive:
>>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>>
>>> This list hosted by: http://www.qsl.net Please help support this
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>>> --
>>>
>>>
>>> Nick England K4NYW
>>> www.navy-radio.com
>>>
>>>
>>>
>>>
>>>
>>>
>>> ______________________________________________________________
>>> GreenKeys mailing list
>>> Post: mailto:[email protected]
>>>
>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>> 2002-to-present greenkeys archive:
>>> 1998-to-2001 greenkeys archive:
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>>>
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>>> Post: mailto:[email protected]
>>>
>>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>>>> 2002-to-present greenkeys archive:
>>>>>> 1998-to-2001 greenkeys archive:
>>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>>
>>> This list hosted by: http://www.qsl.net Please help support this email
>>> list: http://www.qsl.net/donate.html Message delivered to
>>
>>
>> --
>> FCC Rules Updated Daily at http://www.hallikainen.com Not sent from an
>> iPhone.
>> ______________________________________________________________
>> GreenKeys mailing list
>> Post: mailto:[email protected]
>>
>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:
>>>>> https://teletype.net/gksearch 2002-to-present greenkeys archive:
>>>>> 1998-to-2001 greenkeys archive:
>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
>>
>> This list hosted by: http://www.qsl.net
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>
>
> --
> ______________________________________________________________
> GreenKeys mailing list
> Post: mailto:[email protected]
>
>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html
>
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