Gentlemen, I and a few other guys are working on a project to get a very high quality set of crystal filters built for the Yaesu FT2000. The rig is an otherwise very fine unit but the front end is a
Glenn, Many thanks. Now that reply - that's what I like. A man with an unambiguous position! I guess you are saying, "any filter is fine, as long as it's 300 hz." :) 73/jeff/ac0c ____________________
250Hz I use 250Hz roofing filter on my K3 and it works super. -- OV1A Jens Good decisions come from experience. Experience comes from making bad ones _______________________________________________ R
ORIGINAL MESSAGE: REPLY: According to the math experts (I am not one), a 170 Hz shift RTTY signal actually occupies about 350 Hz when you include the sidebands. As you probably know, RTTY is a form o
Simple maths for this used to be shift plus twice the baud rate; 170 + (45 x 2) = 260Hz I have used 250, 300 and 400Hz for contesting at various times. 250 is fine almost all the time; never found th
250 Hz is really too narrow unless one has a high s/n and the interference is from a strong adjacent signal that is activating the AGC. As a first approximation the RTTY signal can be thought of as a
You're right most 455 Khz filters are like this one and have a 1.8 shape factor. http://www.inrad.net/product.php?productid=157&cat=105 That of course works perfectly fine in the final IF of a Yaesu
But why did you use 45 * 2? The fundamental RTTY keying waveform is 45.45/2 Hz, not 45 Hz. (Imagine a signal that switches between mark and space at 22 millisecond intervals; the period of the square
Thanks Joe for that great detail. I did not realize the 250 hz K3 filter ran close to 370 @ -6db. The 400 hz is only 50 hz wider at the -6db point - quite close to the named value. The SSB filters lo
HI Jeff Any 300 cycle filter is good as long as it's 250 cycle :-) I have an Inrad 250 cycle filter in my TS-450SAT and I love it for contesting. Especially RTTY. I have a 500 cycle filter in my Yaes
John, Thank you. Today we have been looking at the actual widths vs. the named widths on some of these filters. There is a lot more disparity on the low bandwidth end than on the wider filters which
Chen, You are right about the ideal DSP being able to handle the selectivity processing. But for our project, we are not assuming that is the case at all. The filter specifications are under our cont
Jeff, The radios are FT1000D. One has 250Hz Yaesu filter, the other has 250Hz Inrad! It's a good point to consider a wider option for S+P, but both the above are fine for run in a test. I do fine tun
The skirts of the stock K3 filters are not especially tight. But they don't need to be. They are basically roofing filters to keep the A/D converter of the "real" software (DSP) filters from clipping
John, That's great to know. Looking at the -6db point, I want to say that Inrad filter runs close to 300 hz or so. Thanks for your comments 73/jeff/ac0c ______________________________________________
Chen, Thanks for pointing me to Jim's site on this filter comparison. I have used his RFI white paper and RF choke design recommendations before. He really is one of the masters. K3 400 is 425. I thi
Jeff, bear in mind when you select filters the following two points: 1) optimal receive filtering has nothing to do with FCC 47 Part 2.202 definition of occupied bandwidth (which is over 400 Hz in th
Hi Jeff. Take a look at the Icom IC756Pro3 RTTY filter scheme. It is the best that I have used.Here is a link to some info. http://www.rttycontesting.com/icom756proiii/icom_ic756proiii_index.htm Also