[GreenKeys] Mark Question

Sat Jan 15 13:35:04 EST 2022

Eugene,

RF-3466A !  Kinda overkill for 45 baud RTTY, but if that is what you 
have, I can understand your desire to make it work.  Maybe it was not 
designed for manual keyboard operation.

Maybe you can kludge in a fast-attack, slow-delay on the RTS line.

Good luck,

Duncan
KL2OEQ

On 15-Jan-22 11:49, W2HX wrote:
>
> Thanks to everyone for their input here. To clarify, the modem is a 
> Harris RF-3466A. It has many options that are configurable. One option 
> is a Mark Hold option. This option can be set to “OFF, ON, SWITCHED” 
> switched means that the mark tone is produced whenever the RTS 
> (request to send) signal is asserted. On means on all the time. The 
> way I have this setup was an attempt to avoid needing to manually 
> switch between TX and RX with some switch or some such.
>
> I set it up so that the exciter is set to VOX and the mark hold is set 
> to SWITCHED. In this way the TX will automatically switch between RX 
> and TX when the typing starts and stops and no other intervention is 
> required. Kind of like a QSK for RTTY.
>
> In addition, there is a device (Black Box CAP) before the modem that 
> does ascii-baudot conversion as well as 9600 bps to 45.45 baud 
> conversion. This allows me to use a standard PC with a usb-serial 
> dongle and a standard terminal program and not have to worry about 
> getting down to 45.45 baud or using a terminal program that supports 
> baudot. This also lets me connect this 9600 baud/ascii channel to my 
> serial console server which allows me to telnet to any serial device 
> in the shack – including this RTTY modem. Just very convenient.
>
> This Black Box CAP device will buffer the data coming in a 9600 and it 
> is set up to assert the RTS line to the harris modem when there is 
> data present. So whenever a character comes from the terminal program, 
> the CAP asserts the RTS line and the modem produces audio for the 
> character. When the character is done being sent, the audio drops and 
> the transmitter reverts to receive mode (VOX). Works really well! But 
> apparently won’t work for RTTY QSO (sad face).
>
> One current workaround is if I type faster than 45.45 baud. The CAP 
> device will buffer up to (I think) 8K of data. As long as there is 
> data flowing on the 45 baud side, RTS will stay asserted and the audio 
> will flow as expected.
>
> If you want to see/hear how it is working currently, here is the end 
> of a longer video showing it in operation:
>
> https://youtu.be/2qJhX7wah_Y?t=1069
>
> the whole Part 3 video that goes into the setup is 
> https://youtu.be/2qJhX7wah_Y
>
> and there are two earlier parts of the project also available you in 
> the link below if you’re interested.
>
> So, based on everyone’s feedback, it looks like I have to figure out a 
> secondary, out-of-band method to manually initiate the RTS when 
> starting a transmission and manually release the RTS line when ending 
> my transmission.
>
> I have some ideas on this. But thanks everyone for their wisdom on 
> this. I had a sneaking suspicion that my setup would not be good on 
> the other side of the QSO.
>
> 73 Eugene W2HX
>
> Subscribe to my Youtube Channel: 
> https://www.youtube.com/c/w2hx-channel/videos
>
> *From:* W2HX
> *Sent:* Friday, January 14, 2022 10:00 PM
> *To:* 'GreenKeys at mailman.qth.net' <GreenKeys at mailman.qth.net>
> *Subject:* Mark Question
>
> Hi all,
>
> I’m still working on getting set up for RTTY at my QTH. I am planning 
> to start with a glass tty set up, then get my M28s wired into the set 
> up. I am using a 1980’s vintage Harris modem that converts RS-232 to 
> audio tones and vice versa. The way it is setup, when I type, I hear 
> the mark/space transitions for each character. However, no audio is 
> produced between the characters. Meaning no mark tone would be 
> transmitted between characters.
>
> Question: How big of a deal is this when doing RTTY? I know that some 
> TUs might not recognize that there is neither a space nor a mark audio 
> frequency present, and may produce garbage on the screen/printer. Or, 
> do most operators use a mark-hold function while receiving that would 
> prevent (reduce) the garbage?
>
> Bottom line, should I go with what I have? Or work hard to make sure a 
> mark tone is present at all times between characters?
>
> 73 Eugene W2HX
>
> Subscribe to my Youtube Channel: 
> https://www.youtube.com/c/w2hx-channel/videos
>
>
>
>
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