Keep in mind that Eric (K3NA) typically operates with AGC off, especially in the presence of strong signals.
Ed - W0YK ---------------------------------------- Ed Muns Muns Vineyard - www.munsvineyard.com Facebook - www.facebook.com/munsvineyard Dick, WC1M, wrote: > > I had exactly the same experience as Bill (and I'm an ex-Orion user as > well.) While Eric is correct that, in theory, roofing filters > with tights skirts aren't necessary in a down-conversion > design, the K3's hardware AGC threshold requires tighter > roofing filters when the band is crowded with loud signals. I > had the 5-pole 500 Hz filters, but quickly found that HAGC > pumping was a real problem in big CW contests. I was > routinely bothered by loud stations just above my passband > (using CW NOR). I subsequently replaced the 5-pole filters > with 8-pole 400 Hz filters and the problem pretty-much > disappeared. Like Bill, I think the HAGC threshold is still a > bit too low. > Alfred Frugoli wrote: > > > > I remember reading a comparison by I think K3NA on the > differences between > > 5 > > pole and 8 pole filters that eventually lead me to stick > with the 5 pole > > filters. > > Bill, W4ZV, wrote: > > Eric and I are both ex-Orion users, which worked well with > 4-pole filters so > I concluded 5-poles would be sufficient in the K3. After > receiving my first > K3 I discovered it had a much lower hardware AGC threshold. > This led to the > "HAGC mod" which was implemented around S/N 350, but I still > don't think the > threshold is as high as Orion's. Therefore the steeper > skirts in the 8-pole > filters are necessary to prevent AGC pumping from close-in > strong signals. > I've since switched from all 5-pole 500s to all 8-pole 500s > (Inrads) in both > of my units. > > I suspect the K3 could be improved without other harmful > effects by raising > the AGC threshold a little more. Someday when I have nothing > better to do I > may try some experiments to see. The DSP filters in both > rigs are probably > similar but the lower AGC threshold in the K3 makes it more > susceptible to > strong adjacent signals if you only use 5-pole filters. > However if you > don't operate in extreme environments like 160 contests you > may never notice > any difference. ______________________________________________________________ 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
