[RTTY] Novice question, re TS-850 filtering & FSK

[Joe Subich, W4TV]

> Does anyone have a TS-850 that they're running with CW filters? If
> so, are your MMTTY markers centered in the spectrum display when
> tuning noise?

Are you sure the TS-850 is in the LSB RTTY (normal) mode and the menu
set to transmit MARK when the FSK line is closed (shorted)?

Also make sure to turn AFC *OFF* in MMTTY and click "HAM" to make
sure than MARK is set to 2125 Hz.  If AFC is on, it is possible that
MMTTY has moved the MARK/SPACE frequencies and it only appears that
the CW filter is not centered on the proper frequencies.

Note: the center frequency of some filters may not be well controlled.
For example, the measurements for the INRAD 400 Hz/ 2nd IF (455 KHz)
filter shown on the INRAD web site, shows that the -6dB points are
not "balanced" around the center frequency.   The same is true for
the 400 Hz/1st IF (8.830 MHz) filter.  The "center frequencies" seem
to be 50 to 90 Hz high.

73,

    ... Joe, W4TV


On 9/12/2011 6:38 PM, wyc wrote:
> Thanks to the many people who responded - off list - to my below inquiry.
>
> I confess, however, to still being stumped.
>
> The TS-850 doesn't have passband tuning (or IF shift tuning) - at least as I
> understand those terms.  It has "slope tuning" controls.  This allows the
> upper and lower edges of the IF passband to be shifted - but only towards
> each other.  It does not allow the upper end of the passband to be shifted
> higher (nor the lower end of the passband to be shifted lower).
>
> With a broader filter, I can see the noise in the passband encompass both
> the space and mark markers in the MMTTY spectrum display, and I can use the
> slope tuning controls to attenuate some of the too-high-frequency and
> too-low-frequency noise, and center the resulting passband on the RTTY
> tones.  However, the slope tuning controls don't yield the shape factor that
> the CW filter has.
>
> Does anyone have a TS-850 that they're running with CW filters?  If so, are
> your MMTTY markers centered in the spectrum display when tuning noise?
>
> (The error I'm dealing with isn't much - 100 Hz or so.  But with 250/400 Hz
> filters, that's a bunch.  Perhaps it is an alignment issue...)
>
> tnx/73,
>
> /Bill, K2PO
>
> ++++++++++++++
>
>> From AA5AU's page http://www.aa5au.com/rtty_radios.html#TS-850 I see several
> people have used a narrow (250 or 270 Hz)  CW filter on RTTY.  (I understand
> there are drawbacks in hearing off-frequency signals...)
>
> I can't seem to get it to work.  (I've got a Kenwood YG-455CN1 250 hz filter
> installed in the 455 Khz IF).  When I switch that filter in, the noise
> spectrum drops way down for the right-most marker in the MMTTY UI.  (I can
> send screen shots if it'd help.)
>
> I've tried both high tones and low tones, with the same result.
>
> I'm using the rig's true FSK - not AFSK.
>
> I wonder if I'm missing something - why are the RTTY tones not equally
> spaced within the filter passband?
>
> (I've also got a 400 Hz filter.  It's broad enough to pass both tones.  But
> for it, too, the tones don't seem to be centered in the passband.
>
> Any help would be welcome.
>
> tnx/73,
>
> Bill, K2PO
> _______________________________________________
> RTTY mailing list
> RTTY at contesting.com
> http://lists.contesting.com/mailman/listinfo/rtty
>