That of course is true, however, there could be potential for a problem
that some might well encounter. 915 x 2 is 1830 and 915 x 3 = 2745 so
the potential for one and possibly two images could occur and pass
through the transmitter under certain conditions.
That is of course one of the reasons why the original 2125 - 2295 was
chosen fits but harmonics don't go through as easily. Seems also that
88 mH torroids might have played a role as well.
Interesting thing playing with rtty signals. I have been messing with
the DM 780 and trying 23 Hz shift out on a MARS frequency. From 850 to
425 to 170 and now to 23 Hz. Lots of fun.
Oh, and for the FSK purists a little story from a few years back.
One day Hal and I were fired up operating the SARTG contest, We were
using some old Hal Keyboards for typing on and I believe an old Flesher
TU-170 for the terminal unit. Hal had a pair of Kenwood Twins which
were as I always told him, poor man's Drakes. The Kenwoods were driving
an old Johnson "Thunderbolt" amp which was a amp that ran class AB1/AB2
on teletype.
Anyway we were doing a Multi-single and I was logging the contacts as
Hal worked the stations. We swapped off this from time-to-time.
Hal in those days worked for the Newspaper and was the head of
production so was often taking calls during a contest and solving
problems at work.
Anyway the phone rang and I answered it. The voice on the other end
said, "Is this Howard Blegen", I replied no he is on the radio, hold on
and I'll get him. The voice replied, fine, tell him it's the FCC.
Oh might fine....I grabbed Hal and told him that he had a call from the
FCC. He thought of course that I was pulling his leg. He answered the
phone tho, this is Hal.
The FCC guy as Hal related a little bit later said, "Are you on the air,
and Hal replied you bet we are on 14.085."
The monitoring guy said hold on a sec, and evidently moved his dial up.
FCC dude sez oh yeah you are real strong on 14.085. About 47 dB over
S9, only problem is that you are also on 13.990 and that just happens to
be Air Force Transcon MARS and you are covering most of there stations
as you are S9 down there.
Hal had me double check on another received with no antenna and sure
enough....
FCC dude was understanding and sent Hal a little letter, Hal had the
pleasure of explaining that his jim dandy FSKing of the fine Kenwood
Twins using the standard Irf Hoff 3-12 pF trimmer and diode in the
Cathode pin of the VFO tube was a little suspect using this radio. The
amp didn't help as it was broad as a barn as well.
Hal took the fine Kenwoods to the next Hamfest in Puyallup, after having
removed the FSK circuit. They went down the river.
The letter back to the FCC was brief. Disposed of lousy radios and
bought a Yaesu. Thus Hal came into the modern world (sort of). Yaesu
FT[-757 was next.
W0MU Mike Fatchett wrote:
> I also recently learned that you can set the receive freq to 915hz so you
> don't have to listen to that very high pitch at 2125. Just tell MMTTY you
> are running 915 and everything works great.
>
>
> "A slip of the foot you may soon recover, but a slip of the tongue you may
> never get over." Ben Franklin
> -----Original Message-----
> From: rtty-bounces@contesting.com [mailto:rtty-bounces@contesting.com] On
> Behalf Of Bob
> Sent: Wednesday, March 04, 2009 7:26 PM
> To: RTTY Reflector
> Subject: Re: [RTTY] Calibration Check with W1AW RTTY Bulletin
>
> Thanks to Dick AA5VU and Richard VE3IAY for taking the time to answer my
> question. I was thinking there was something magical about a 2125 Hz tone
> but that just sets the location of the Mark Freq in relation to your rigs
> freq readout. I guess that's why it doesn't really matter if you use LSB or
> USB just as long as you set the mark freq and then shift in the right
> direction. I guess that's why there is a reverse button in most of the AFSK
> RTTY SW.
>
> So if I want to set up a QSO on RTTY I just need to tell the other station
> what freq my Mark will be on and let them do the addition or subtraction
> depending of their SW or rig.
>
> Thanks again
>
> Bob
> K4QHH
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>
>
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