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Rtty loop

Marc /. Leavey M.D., WA3AJR 6 Jenny Lane Baltimore. MD 21208

Back to the Beginning

With appropriate ruffles and flourishes, (am pleased to note thai this monlh begins the I5lh year of "RTTY Loop"! Raiher than wax nostalgic, as I often do at anniversaries, Jet me |usl say thai this column has covered a loi of ground these many years, and has evolved in more waysihan one.

This month, to start out. I'd like !o drop back to a basic quesiion This was prompted by a letter from Gregory Mclniire KE0UV of Belle Fourcfte. South Dakota, that surfaced from the stack on my desk, it s one of the ' Oh.' know the answer to this" questions that soon becomes mired in too many answers.

Gregory would like to know how to determine I he exact frequency thai a RTTY, AMTOR, or packet station is operating on.

Exploring the Question

To quote KE0UV: "When operating CW : think there is little quesiion of what the operating frequency is Whether the digital display of a transmitter is accurate or not, I think {hat it is understood that the frequency ol operation fs the actual and exaci radio frequency which is radiating from the an lenna When operating SSB phone, the actual frequency radiating from the anienna varies WFlh the modulating audio. So, we designate the operating frequency1 as the frequency of the suppressed carrier. This "suppressed carrier' frequency does not ever radiate from the antenna during an SSB phone transmission, though Nevertheless, we specify the particular sideband along ™th the suppressed carrier frequency as the frequency of operation But when comes to the FSK modes, there ^eem to be differing opinions.

Some rigs use two audio rones generated by a modem (TU)t fed into the nuke jack, rn SSB mode (usually LSB) to generate FSK al radio frequency. When this method is employed, and using LSB, the two RF frequencies radiating irom the antenna are the 'suppressed earner' frequency minus the two audio frequencies This means that the higher audio tone will create the lower RF frequency, and vice versa if the two aucJ^o tones used are 2295 Hz ana 2125 Hz. and the suppressed carrier frequency is set at 100 MHz (LSBi then two Rc frequencies will be 097705 MHz and 1 J 097875 MHz. If we use the LSMFT rule |Low Space Weans Fine Teletype] the higher audio tone generated in the modem causes the lower RF, or space frequency, to radiate from the antenna

1 'Other rigs use a direct FSK scheme which does not use SSB The modem or terminal unil simply sends a high or

Amateur Radio Teletype fow voltage to determine whether to transmit the higher or the lower radio frequency. This would be the same as two different CW signals transmitted alternately. U is my understanding that some transceivers, in FSK mode, display the lower RF at Itie digital readout, while others display the higher frequency as the frequency of operation.

"It has been my persona) experience that many, if not most, hams determine their frequency of operation to be that which the digital readout is displaying durng transmission, regardless of which of the two types of signal generai-on is employed Using the two audio tones into LSB' (often referred to as AFSKj method, the actual frequency radiating from tfv;.' antenna could be 2.295 kHz for more) lower than what the readout is displaying. Conversely, using the so-called "direct FSK1 method, the readout should dispiay one of the two RF frequencies correcily.

"Anyway, back to my quesiion. What is th& correct designation of a two-tone, RTTY, AMTOR. Or packet operating frequency? The lower radio frequency, ihe higher radio frequency, the suppressed earner frequency, or none of these?"

Gregory. I really think this is a landmark quesiion Jt has advocates on all sides I turn it over to the readership— to ail of you—for input, and look forward to forming some kind of consensus. Who knows, maybe we will even turn this into some form of necessary standard I At any rate, readers are invited to send their votes and opinions to me, at the designated address, for in-elusion in a fulure column.

More Questions and Answers

Aiways looking forward to a view ol another ham's messy shack, i appreciate the photo of Michael Freedman VE3BGE, hailing from Toronto which \ share *th you all herewith. His station sports an impressive assortment of radio gear Looks good, Michael and thanks for the photo. Sure folks, go ahead and send me photos of your junk, too. You never know just what you'll find in "RTTY LoopT'!

Back in February 1991, I passed along Norm WJSZ's requesi for a Morse code copying program for the Color Computer. Ed Tyson N5JTY of Alamogordo. New Mexico, reached back into his memory cells for the answer. in December 1982, the late SO Micro published an article called "CC CQ.J" by Michael Chuck of Severna Park, Maryland In ths article, a transmitting and receiving Morse terminal for the CoCo ts desc rrbed

The article, which also inctudes a complete lisiing for a program to accomplish the lask. is far too long to reprint here, tf you insist, and cannot dredge up a copy anyplace else, I can be persuaded to send you a copy, for

Ihe customary S2 and a LARGE self-addressee. stamped envelope with two ounces' worth of postage.

Last for this month thanks to Do-menic M Uallozzi NiOM of Water-town, Massachusetts, for a comment he sent me Dom recalls my quesiion regarding rnechanrcaJ teleprinters and states that his station is a Model 15 page printer ¡he has both a commercial and a military version), a HAL ST5K demodulator, and a home-brew AFSK running into an old Heath HW-101 transceiver,'1

Dom also notes that he has "about 100 QSOs on RTTY from W1 AW over the pasi ten years Don't know if the visitor's RTTY position exists in the new station, but I hope so One of the operators there told me that very few visiiors ask to operate RTTY. He said he could only rememoer two others in the fast five years."

I'm fairly caught up with responses to your questions, and wrth requests for copies of the programs recently described if you have not heard from me within a month or so of your letter, edds are lhat I did nol receive ihe initial question. As always, direct your comments, questions, suggestions, and barbs to me at the above address, or via CompuServe {ppn 75036,2501) or Delphi (usemame MARCWA3AJR). I look forward to hearing from you in this, the 15th year of RTTY Loop H

Gregory Lask

Mtchze! Freedman VE38GE from Toronto

Number 21 on your Feedback card

Mtchze! Freedman VE38GE from Toronto

Number 21 on your Feedback card

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