Joe Subich, W4TV wrote: > > > For those reasons I would support 250Hz because it would meet > > the needs of more users, but would vote against 200Hz (and in > > this, I do literally mean "vote with my pocketbook"). > >I agree with Ian here ... a filter with a reliable 270 Hz bandwidth >would be nearly ideal for RTTY and far better than the so called >"250 Hz" 8 pole filter. I would almost certainly replace the >5-pole 200 Hz filters with 8-pole 250-270 Hz filters. >
Agreed. 250-270Hz would be the "sweet spot" for an 8-pole filter, to guarantee good sales for the manufacturer *and* good performance for a range of users in heavy QRM. Now let's see if Inrad or Elecraft take the bait :-) 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek >On 7/14/2010 5:05 PM, Ian White GM3SEK wrote: >> Bill W4ZV wrote: >>> >>> >>> Gary Hvizdak wrote: >>>> >>>> If instead you think that there might be a greater demand for some other >>>> bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to >>>> let me know that width and include your reasoning for desiring that other >>>> width. >>>> >>> >>> I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250" >>> is actually 370 Hz BW and I don't want that). >> >> Yes, the real gap in the available range of roofing filters is an 8-pole >> with a *true* 6dB BW of 250Hz. >> >> As for the choice between 250Hz and 200Hz, I have tried both bandwidths >> by modifying a stock 200Hz 5-pole filter (with design help from Wayne). >> >> In real-life contest QRM there is no noticeable difference between the >> two bandwidths on CW, but there is a huge difference for RTTY. With >> 170Hz shift, a 250Hz filter is very close to the lower limit of usable >> bandwidth, but definitely on the right side of the line - in heavy RTTY >> QRM, a 250Hz filter can be a game changer. But 200Hz is below that >> limit, not usable at all. >> >> For those reasons I would support 250Hz because it would meet the needs >> of more users, but would vote against 200Hz (and in this, I do literally >> mean "vote with my pocketbook"). >> >> -- ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
