[RTTY] Off Frequency Stations.

[Phil Sussman]

I do not know if this was mentioned previously, but shift
also plays a part. Some stations run a 200 Hz shift
while others run 170Hz. This will cause discrepencies 
when tuning.

73 de Phil - N8PS

----------

Quoting "Bill, W6WRT" <dezrat1242 at yahoo.com>:

> ORIGINAL MESSAGE:
> 
> On Thu, 23 Sep 2010 06:55:07 +0000 (GMT), Mick Mc Grory
> <mi0grg at ymail.com> wrote:
> 
> >
> >When taking part in the BARTG 75 Sprint last weekend,a lot of Stations who 
> >answered my CQ call were slightly off my Frequency,so I had to fine tune
> their 
> >signal with my RIT control.
> 
> REPLY:
> 
> Hi Mick, welcome to RTTY.
> 
>   It could be you or it could be them. The culprit is usually incorrect
> use of AFC. The problem happens when AFC causes your (or his) TX and RX
> frequencies to be different. When running FSK, as you are, AFC only
> changes your RX frequency. Your TX frequency is set by the transceiver's
> VFO and AFC has no effect on it. 
> 
> There are two ways this frequency mismatch can happen. 
> 
> if you run MMTTY with AFC on and you are S&Ping, what happens is you
> will be tuning across the band and when you come near a station, the AFC
> will reach out and capture the station and tune it in correctly
> according to the tuning indicator. The problem is that as soon as AFC
> captures the station, you naturally stop turning the VFO and as a
> result, your TX frequency is slightly off the RX frequency. This is
> usually the cause when you are answering a CQ and you think you are
> right on his frequency but actually you are not. 
> 
> The other way the mismatch can happen is if you turn AFC off while the
> mismatch exists. You can correct the mismatch by always clicking the HAM
> button after turning off AFC. If you look at the MARK frequency in
> MMTTY's main window, it should be 2125 whenever AFC is off. Clicking the
> HAM button sets it to 2125 if it is off. 
> 
> I realize this is a little bit arcane, so here are some simple rules you
> can follow to make things work right:
> 
> 1 When you are CQing, have AFC on and do not touch your VFO knob. Let
> AFC do all the tuning-in.  Generally, MMTTY has enough range on the AFC
> that you should not have to use your RIT unless the calling staion is
> really way off. 
> 
> 2. When S&Ping, turn AFC off, click the HAM button at the start of the
> S&P session and verify that the MARK window says 2125. Doing this will
> assure that your TX and RX frequencies are exactly the same and will
> stay that way until you turn AFC on again when you go to CQ mode. 
> 
> If you are running MMTTY standalone, you will have to do the above
> button-clicking manually, but if you are running N1MM Logger and using
> the MMTTY engine, there are two check boxes in the digital interface
> Setup>Settings window that will do both 1 and 2 for you automatically.
> The two boxes are the ones where the text next to the box starts with
> MMTTY in parentheses. Check both boxes. 
> 
> I realize this is a little confusing at first, but once you get it
> right, it never changes. If you have any questions, feel free to ask. 
> 
> Incidentally, the NET button has no effect while running FSK. It can be
> either on or off, doesn't matter. I leave it off. 
> 
> Hope to work you in the CQWW this weekend. 
> 
> Bill, W6WRT
> _______________________________________________
> RTTY mailing list
> RTTY at contesting.com
> http://lists.contesting.com/mailman/listinfo/rtty
>