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Author Topic: ic-718 and rtty  (Read 723 times)
K7MDO
Member

Posts: 325




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« on: July 01, 2007, 10:31:50 AM »

I am trying to hook my IC-718 up for RTTY using its FSK internal modulator.  I have MMTTY (a great program in my mind because it received first time I installed it and it seems pretty easy)....

I guess what I don't understand is the sequence of internal events in the -718.... when I look at the MMTTY instructions they only have me hook up (through a transistor) the FSK line and a ground...

In my musings on this I expected to have to hook up a send wire as well.... the way I pictured it was that when I would press TX in the software, it would first gnd the send wire (move the receiver to transmit), then through the FSK wire it would tell the icom internal modulator to go steady mark with space being the "keyed" function coming over that line.... thus when the TX key is first pressed (and the buffer is empty) there would only be a continuous 2250 hz tone being transmitted and only when a character came down the line would I get any keying of the FSK line to drive the spaces.??

I can't see how the single wire will turn on transmiter from receive and then also provide the imput for mark and space??

I have researched some but all I come up with is a reference to a current loop that simulates the old mechanical teletype drive...

Any help out there??  Tom
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WA4MJF
Member

Posts: 1003




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« Reply #1 on: July 01, 2007, 01:57:30 PM »

Not sure what a MMTTY is, but anyhow
FSK is shifting the frequency 85, 170,
425 or 850 Hz.  No tones, that is AFSK.
The transistor may be taking the place of the
polar relay and is simply operating the
shifting mechanism which I'm sure is not the
ceramic trimmer cap that I'm familiar with,
in and out of the circuit to change the
frequency the requiste amount.

73 de Ronnie
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K7MDO
Member

Posts: 325




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« Reply #2 on: July 01, 2007, 03:41:37 PM »

MMTTY is just a software package in my shack computer...

The problem for me is the wiring from the "D" connector or serial port on the clone computet.  The MMTTY software suggests only that the GND and the FSK line (through a transistor) need to have connections and I am pretty sure I would still need to turn the -718 to its "ON" state for transmit...

I suspect I am wrong but I thought the sequence would be:

When ready to transmit a line of text from the computer buffer:

1: hit the computer TX tab
2: This would flip a pin on the "D" connector and the serial port would GND the "SEND" lead of the -718 and start a continuous transmitted tone at say 2150
3: then the FSK pin on the "D" connector would start going from 0-1 or whatever the character code requires through the transistor and then this would trigger the -718 FSK line to "shift" the output from the steady mark tone to the space tone as required.

I guess what I am asking is what happens in RTTY mode in the -718?  Does grounding the SEND terminal have a function while in RTTY mode or is the entire operation of sending RTTY conducted through the FSK and GND lines only on the accessory connection ?

?

73, Tom
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K7MDO
Member

Posts: 325




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« Reply #3 on: July 05, 2007, 08:28:46 AM »

This topic didn't generate much interest but further research has headed me in the direction of using AFSK rather than FSK for now.

I am certain that eventually for RTTY I will use FSK but the kits and stuff I see available to get things rolling all seem to aim toward AFSK.  

Add this to the opportunity to try PSK using the soundcard also makes the decision easy.

Take care, Tom

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NJ2E
Member

Posts: 35




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« Reply #4 on: July 09, 2007, 11:26:40 AM »

Hello Tom, First of all have you connected the serial port to the acc socket properly? I don't have a 718, but reviewed the manual on line. You need only three connections to the radio (AF out for MTTY, which appears correct from your posting. FSK keying and Ground). When not sending anything you should have a steady tone or an idle switching from mark to space (sometimes called diddling). Have you selected the RTTY mode on the radio? It won't send unless you do. The MTTY help section talks about a steady tone heard using FSK and how to turn it off. I would suggest connecting the rig to a dummy load and turning the power level down ( This should be done anyway, since rtty is a 100% duty cycle mode and will over stress your 718), monitor your signal on another radio (ssb mode) and play with the software and radio. Also go to the MTTY group on yahoo.com, I sure someone has already asked your questions. There is no difference between AFSK and a FSK signal once it escapes from your radio. The big differnce is having to remove you microphone to supply audio to your radio when using AFSK vs. using the Acc jacket in the back for FSK and leaving it alone. Also you will require some form of interface to your soundcard with AFSK. Hope I was of some help, 73s Don
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KV9U
Member

Posts: 166




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« Reply #5 on: July 09, 2007, 01:07:45 PM »

I have an ICOM 756 Pro 2 which I use on AFSK only. I have it connected with line audio in and out from the rear connector on the rig to the sound card through a homebrew interface which is really a radio shack line isolator used for car stereo. This is nothing more than a pair of transformers potted in a container.

Then I have the CI-V port connected through a homebrew interface to a USB to serial adapter to the computer.

This allows me to key the rig through the CI-V without having to come up with another USB to serial adapter for keying.

If I wanted to do FSK, I would have to use another USB to  serial adapter with a very simple interface to provide the FSK keying. This would enable me to use the excellent RTTY filters in the rig. I am not very interested in RTTY anymore so have not done this since most all other sound card modes are AFSK.

It is my understanding that ICOM did not include PTT with the 718. This is most unfortunate and it requires that another COM port or USB to serial adapter for PTT keying be used in addition to the CI-V.

You could then operate without the CI-V, but it is such a nice feature to have rig control, that once you use this with programs such as DXLab Commander with Multipsk or Ham Radio Deluxe with Digital Master 780, you would not want to give up this feature.

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KV9U
Member

Posts: 166




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« Reply #6 on: July 09, 2007, 01:18:06 PM »

I have an ICOM 756 Pro 2 which I use on AFSK only. I have it connected with line audio in and out from the rear connector on the rig to the sound card through a homebrew interface which is really a radio shack line isolator used for car stereo. This is nothing more than a pair of transformers potted in a container.

Then I have the CI-V port connected through a homebrew interface to a USB to serial adapter to the computer.

This allows me to key the rig through the CI-V without having to come up with another USB to serial adapter for keying.

If I wanted to do FSK, I would have to use another USB to  serial adapter with a very simple interface to provide the FSK keying. This would enable me to use the excellent RTTY filters in the rig. I am not very interested in RTTY anymore so have not done this since most all other sound card modes are AFSK.

It is my understanding that ICOM did not include PTT with the 718. This is most unfortunate and it requires that another COM port or USB to serial adapter for PTT keying be used in addition to the CI-V.

You could then operate without the CI-V, but it is such a nice feature to have rig control, that once you use this with programs such as DXLab Commander with Multipsk or Ham Radio Deluxe with Digital Master 780, you would not want to give up this feature.

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