[Elecraft] Band pass filters

[CUTTER DAVID]

Hi Paul

Thanks for those thoughts.  I see your point re sharing a tri-bander and that looks like a severe case.

Looking at the number of filters already in place and the low spurii expected of Elecraft gear, it looks worth considering to down-grade the extra filters.  For instance, the KPA amplifier has low pass filters on its input and output, then the atu has a filtering effect.  I wouldn't know what this adds up to, but when the W3NQN filters were designed, things were very different.  
 
73 David G3UNA  

> On 27 July 2021 at 17:30 Paul GACEK <paul.gacek at me.com> wrote:
> 
> 
> Hi David 
> 
> I think any answer is dependent on the station configuration. 
> 
> For example, if the M/2 station is sharing a single tribander (i.e. one on 20m and another on 15m) then I imagine filters are still essential as a tri-plexer will only provide so much isolation.
> 
> Another example; If a less than optimal 2xn antenna switch is used (i.e. doesn’t provide excellent isolation) then filters can help to minimize interference. 
> 
> These observations are based on my limited experience building a portable SO2R station and separately a short time owning a Flex 6600M that had “state of the art” internal filters. Reading the Flex manual seemed to suggest that all bets are off when power exceeds 100w and you want to transmit on one port and listen on another.
> 
> Paul
> W6PNG/M0SNA
> www.nomadic.blog
> 
> > On Jul 27, 2021, at 9:09 AM, CUTTER DAVID via Elecraft <elecraft at mailman.qth.net> wrote:
> > 
> > Given the improved performance of modern transceivers, is there still a call for high specification W3NQN band pass filters in a 2-transmitter station?  For example on a Multi-2 contest environment.  For instance K3S + KPA + KAT. The filter fitted between radio and amplifier. 
> > 
> > I have the *feeling* that a receive-only filter (with tx bypass) might be all that is needed.  This is much easier to implement than a full transmitter-rated set making fast switching between bands (eg for a quick look around) very quick and easy from the keyboard, etc. 
> > 
> > David G3UNA