[Elecraft] Re: start without ANY extra roofing filters....
SM2EKM: I´m eagerly waiting for measurement figures on the K3. Beats me why they can´t be presented, that I don´t understand at all, after all it´s no rocket sience. I'm surprised that so many roofing filters (and the K3 itself) have been designed and offered for sale before the specifications are known/posted. Seems like the reverse order would have been more appropriate. John Harper AE5X http://www.ae5x.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Re: start without ANY extra roofing filters....
AE5X: I'm surprised that so many roofing filters (and the K3 itself) have been designed and offered for sale before the specifications are known/posted. Seems like the reverse order would have been more appropriate. I was also concerned about so many filters until I realized Elecraft has actually leveraged the Inrad 7XX series of filters offered for the 8.215 MHz IF of the FT-1000 family. I suspect they may even use the same mechanical configuration, so hopefully they have not invested RD and inventory resources in providing the large number of 8-pole filters. http://www.qth.com/inrad/ft1000mp.htm The 5-pole and variable BW filters are apparently proprietary designs. I will be especially interested in seeing IMD/BDR measurements for the variable filters since *variable* also may imply *variable* IMD/BDR results (depending on BW). I feel it's still important to see in radio IMD/BDR results before selecting any filters. If the 8-pole 2.8 kHz should have better results than the stock 5-pole 2.7 kHz, I hope Elecraft will consider making the 8-pole standard with for an additional charge of $41 ($120-79) to K3's base price. IMD/BDR measurements should take most of the mystery out of the filter choice process for most of us, but IMD measurements are not totally straight-forward as KC1SX (ARRL), W2VJN (Inrad) and NC0B (Sherwood) can tell you. Let's QRX and give Elecraft a chance to do the measurements carefully. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Re: start without ANY extra roofing filters....
If my CAD computer design days don't fail me, I recall 8-pole type filters - had much steeper skirts, but not so hot passbands, sort of ripply. Having already forgotten the spec on group-delay (phase?) - I'll have to look that up. Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: start without ANY extra roofing filters....
Passband ripple is more a function of the filter design parameters--was it designed as a Chebyshev with 1 dB passband ripple, or a Butterworth with a flat passband, or a Gaussian with a rounded passband, etc. And, of course, those parameters govern also how fast the skirts roll off and, of great importance in many applications, how the group delay looks. All else being equal (e.g., two filters, same nominal 3 dB bandwidth, same design parameter, e.g., Chebyshev) the one with more poles will have better passband roll off, or shape factor. I can show you some four pole crystal filters I've designed and built with essentially perfectly flat passbands and others with lumpy passbands. Jack K8ZOA Fred (FL) wrote: If my CAD computer design days don't fail me, I recall 8-pole type filters - had much steeper skirts, but not so hot passbands, sort of ripply. Having already forgotten the spec on group-delay (phase?) - I'll have to look that up. Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: start without ANY extra roofing filters....
I was also concerned about so many filters until I realized Elecraft has actually leveraged the Inrad 7XX series of filters offered for the 8.215 MHz IF of the FT-1000 family. I suspect This is an interesting point! Makes me wonder about the 1.8kHz filter for SSB contesting. designs. I will be especially interested in seeing IMD/BDR measurements for the variable filters since *variable* also may imply *variable* IMD/BDR results (depending on BW). Especially, as it would seem to me, if the diodes used to tune the filters cause any problems. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
