Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

On 4/23/2014 10:47 PM, Walter Underwood wrote: The usual approach is to choose a filter with steep skirts that is wider than you need, so you can use the middle of the passband where the phase response is not so bad. Then do additional filtering in DSP, where you can have good amplitude and

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

I ordered from Inrad 6KHz AM filter. I bought on ebay a Astron RS-35M Power Supply I figure even if it has something wrong with it, it will be easy to fix. Thank you for all the help. It's been mind bogglingly interesting. Larry -- View this message in context:

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

It turns out that the Elecraft 2.7 KHz 5 pole filter is the winner according to: http://www.qsl.net/gm3woj/k3filtertestssn2203.pdf which makes me want to make my own filter. Still, I'm going to keep the 400Hz 8 pole filter which is coming with my S/N 27xx Elecraft Radio !!! -- View this

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

And just for the record. If you are going to optimize for bandpass shape then you are going to have non constant group delay. If you add more crystals you can have both and the filters would be more expensive. It's a compromise and we demand this compromise. A phase linear filter looks bloody

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

Some of the wider filters in that paper are pretty good. The narrowest filters are not so good. The flat part of the passband has constant group delay. The skirts are awful For narrow filters it starts going weird. Larry Lopez [via Elecraft] wrote: It turns out that the Elecraft 2.7 KHz 5 pole

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

In analog filter design, you get to choose between good phase performance and good amplitude performance. You can't have both. If you want a flat passband and steep skirts, you'll get wonky phase. The Chebyshev filter is a good example of controlling amplitude response. If you want good phase

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

On 4/23/2014 10:13 PM, Larry Lopez wrote: Some of the wider filters in that paper are pretty good. The narrowest filters are not so good. The flat part of the passband has constant group delay. The skirts are awful Nothing at all surprising. In general, phase distortion (group delay) goes

[Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

I'm wondering if any digital filters exist for the K3. I'm wondering which common filters work best on the K3. I'm interested in JT65 and JT9 linear phase delay and constant group delay means that the signal of different frequency take the same time to go through the filter so that the waveform

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

On 4/21/2014 1:08 PM, Larry Lopez wrote: I've been using the filters on my FT1000D and I do notice the 250 Hz one doesn't seem to help JT65HF as much I would have expected. Any ideas, Read previous posts about this from W4TV and myself this morning. 73, Jim K9YC

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

Thank you Jim, I read all your posts. I'll quote your quote of K1JT again here: K1JT says that it is best to run the radio broadband and let the WSJT software provide the needed selectivity in its decoding algorithm. The reason is simple -- phase shift can cause decoding errors,

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

Now with EME this isn't much of a problem I would think. If no strong signals are present then the DSP wold be able to shrink the bandwith just fine. Even though a wide filter lets in a lot of noise the DSP can get rid of it. -- View this message in context:

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

This is wrong: Even though a wide filter lets in a lot of noise the DSP can get rid of it. The WSJT software is a DSP. It has it's own filters and the DSP on the K3 is not needed. So the only job of the K3 is to produce a clean wideband signal for the WSJT. You would still have to prevent

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

On 4/21/2014 1:59 PM, Larry Lopez wrote: But what about: very weak signals reducing the bandwidth increases the signal to noise ratio. very strong signals reducing the bandwidth can prevent the DSP chain from desensitizing the receiver and/or saturating the a/d converter. Joe is well aware of

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

I've already recanted on S/N ratio. I was an idiot. I kept skipping the part where the PC is also a DSP. Sven's post on the other thread also brought my attention to it. The only thing left is strong carriers overloading the receiver. I'll go find WSJT and learn some more. Thanks again Jim.

Re: [Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

Joe is well aware of the issue. Hiss answer that the phase distortion issue trumps S/N ratio. K1JT is correct as it relates to EME where one does not generally have strong interfering signals. Remember the detection bandwidth in WSJT-X is on the order of a few Hertz - not the 2.8 to 5 KHz