Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Edward R. Cole
ld be fun listening into all the stations. I have a 1296/28 transverter to use with the K3. 73, Ed - KL7UW -- Message: 11 Date: Wed, 09 Feb 2011 08:13:19 -0800 From: Vic K2VCO Subject: Re: [Elecraft] adding 250Hz filer, any improvement? To: elecraft@mailman.qth.net M

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Joe Subich, W4TV
The "250 Hz" filter has a nominal -6dB bandwidth of 350 to 370 Hz (see plots at http://www.elecraft.com/K3/filter_plots/250.gif and www.inrad.net). The 400 Hz filter has a nominal -6dB bandwidth of 430 - 450 Hz (plots at the same sites). Since the ultimate selectivity is generated by the DSP, *

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Jim Brown
On 2/9/2011 8:23 AM, Scott Ellington wrote: > The additional noise reduction of a narrow crystal filter is negligible. Right. While a narrower filter reduces the noise bandwidth, the ringing of a filter with steeper slopes may increase the effects of impulse noise. > (QRM is another matter.)

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Jessie Oberreuter
I've noticed this effect myself. At super narrow bandwidths, the signal and remaining noise are both essentially on the same frequency. With nothing else around to provide a base-line reference, discrimination becomes a function of real-time delta power measurement rather than tone dete

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Scott Ellington
I agree with both Don and Bill. There are really two issues: In the presences of just noise, the DSP with a wider crystal filter is adequate. The additional noise reduction of a narrow crystal filter is negligible. (QRM is another matter.) The brain/ear system, at least for many operators, i

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Vic K2VCO
I see that others have told you that you can narrow the DSP and it will be just as good as long as there are no nearby signals greater than about S9+20. Let me add that a huge improvement in copyability of weak CW can be gained by using the APF in current firmware. It has a bandwidth (I believ

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Don Wilhelm
Ed, If there are no strong signals on the band or nearby your receive frequency, then any filter, even the stock 2.7 kHz is sufficient. The only purpose of the roofing filter is to keep strong signals out of the receiver passband so they do not activate the AGC and de-sense the receiver for

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Bill W4ZV
Edward R. Cole wrote: > > Let me ask a filter question for a different situation. I am > interested in receiving very-weak CW and currently have the 2.8 KHz > and 400-Hz 8-pole filters. Will narrowing the DSP bw down to 200-Hz > work as well as using a 200-Hz filter? There are no strong st

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-09 Thread Edward R. Cole
Let me ask a filter question for a different situation. I am interested in receiving very-weak CW and currently have the 2.8 KHz and 400-Hz 8-pole filters. Will narrowing the DSP bw down to 200-Hz work as well as using a 200-Hz filter? There are no strong stations either nearby or on the ban

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Robert Bajuk
I found 8 pole 400 Hz and 5 pole 200 Hz as a great combination in last CQ 160m. 400 Hz filter was to wide most of the time. 73 Robert, S57AW Sent from iPhone Na dan 9. feb. 2011, ob 02:30, Wayne Burdick je zapisal: > On the other end of the spectrum: If the going is really tough, you > mig

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread David Gilbert
The waterfall in CW Skimmer is extremely accurate for that sort of thing. Whether you mouse click on a "decoder" (station) or use the Up/Down arrow keys to jump from one to the next, the zero beat is very, very accurate. So much so that when I was using CW Skimmer in 3 KHz audio mode simply

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Bill W4ZV
wayne burdick wrote: > > On the other end of the spectrum: If the going is really tough, you > might consider our 200 Hz, 5-pole filter. It's a favorite of CW and > data-mode operators who routinely have to dig for weak ones between > monster signals in CW and data modes. > I operated mo

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Wayne Burdick
On the other end of the spectrum: If the going is really tough, you might consider our 200 Hz, 5-pole filter. It's a favorite of CW and data-mode operators who routinely have to dig for weak ones between monster signals in CW and data modes. 73, Wayne N6KR On Feb 8, 2011, at 11:07 AM, Scott

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Dave Hachadorian
d the K3's that the filters were 400's, so they switch in at that dsp bandwidth. Dave Hachadorian, K6LL Yuma, AZ -Original Message- From: Scott Ellington Sent: Tuesday, February 08, 2011 12:07 PM To: Elecraft Reflector Subject: Re: [Elecraft] adding 250Hz filer, any impr

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Scott Ellington
QRM levels are generally much lower outside EU or NA. Years ago, I did a CW contest from ZL with a TS-50 and a single 500 Hz filter. That would have been woefully inadequate in NA, but it was fine there. So, the question I would ask is whether anyone in a non-EU or NA QTH has compared the K3

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Jim Brown
On 2/8/2011 9:49 AM, Jorge Diez - CX6VM wrote: > If I add a KFL3A-250 (250 Hz 8-pole) filter I will notice it better to use > in contests? Or with the 400Hz is enough? Jorge, I find that the 250 Hz filter helps a lot when there are strong signals very close to a weak station. I bought one a yea

Re: [Elecraft] adding 250Hz filer, any improvement?

2011-02-08 Thread Rex Lint
If you have strong stations closer to your frequency than 400 hz, then the 250 hz filter will get rid of them down to 250 hz of your frequency. If the stations that are near you are not strong, the DSP filter will handle it OK. -Rex-   K1HI   Rex Lint   Merrimack, NH