[RTTY] IC 756 Pro II and rtty

[Jerry Pixton]

All who have followed my previous tests,

I made one of those embarrassing discoveries yesterday after looking at 
Don's report on the Pro III. From his pictures it looked like a filter 
equal to the "data" filters was now available for RTTY. I started to write 
out several questions for Don to check for me.

When I looked at my rtty filter with RTTY FIL ON, I discovered that the 
filter looked pretty good.

I had already switched all my rtty operation of this radio down to 1415 Hz 
in order to use the LSB-D steep sloped filters, when the radio had to go in 
for repair. Of course when it came back all the menu settings were cleared 
to defaults. I reset some of them but have never gone completely though all 
of them again (you play with a new radio and all its options but after that 
you forget most of the bells and whistles).

After investigating what was going on, I discover there are TWO settings 
that involve the filters that are available in RTTY mode. In previous 
tests, I was seeing the bad triangular shaped filters for rtty with RTTY 
FIL OFF and the Twin Peak Filter with its excessive processing noise with 
RTTY FIL ON which seemed to have sharp slopes but unbearable noise in the 
earphones.

It turns out that there is a menu setting for the rtty filters described on 
page 28 on the manual RTTY filter/Twin Peak filter. Once you know what 
happens you can understand the instructions! There are 5 additional 
bandwidths for this filter, and they have steep slopes (just like the data 
filters) and you can have the Twin Peak feature on or off in each 
bandwidth! So if you select the 250 hz bandwidth and turn the Twin Peak 
filter OFF you have a nice steep slope filter centered at 2210 hz. From the 
measurements I did yesterday with Analysis 2000, this filter is the same as 
the data filters and it is in the right place for rtty!

I think this is the fresh-from-the-factory setting so I suspect many of you 
wondered what I was talking about last year when I decided to move down to 
1500 hz for rtty.

Now to return to normal and run some tests during the Sprint.

Thanks to Don for the impetuous to look once again at my rtty filters.

Jerry, W6IHG
------------------------------------------
Dr. Jerry R. Pixton, PIXOS Designs LLC
http://www.pixos.com/designs/RadioTuner/
jpixton at shentel.net
------------------------------------------