[Elecraft] [K2]Crystal filters

[Bill Coleman]

On Feb 28, 2009, at 11:41 AM, R. Kevin Stover wrote:

> I'm going to setup and use my RTTY filters for digi modes and need  
> some
> guidance on suggested bandwidths and center frequencies.

First thing to consider is if you have enough BFO bandwidth to go with  
standard tones. I opted to use 1500 Hz as the center frequency for my  
RTTY tones (eg 1415 mark, 1585 space). My thinking is that this would  
allow me to use the DSP and have the signals centered in the passband,  
since you can only adjust the frequency center on 100 Hz boundaries.

I had to make a minor modification by adding a couple of pF to the BFO  
crystals to get enough range.

I've set my filters to OP1, 1000, 500 and 300. 1000 makes a pretty  
nice filter for tuning, 500 is great for crowded contest conditions.  
300 is for when the going really gets tough.

The K2 is a good radio for RTTY, but it isn't great. Biggest  
limitation is that the KPA100 can't take the full duty cycle, so you  
have to back off. I run about 50 watts with supplemental cooling on  
the heat sink. Second limitation is that the frequency display doesn't  
correct for the mark frequency, so you have to do it in your head.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901