[CQ-Contest] band-pass filtering -- a new approach?

[Mike Gilmer - N2MG]

Their use is not anything new - perhaps they were more 
effective with "pre-phase-noise" radios.

BTW, often there's no need to "bypass" the RX filters 
during transmit. Just wire them up so that they are in 
the radio's receive path.  Many radios (with some 
notable exceptions) have some way of accessing this 
path at the rear panel.  If not, you can open up the 
radio and "break into" the rcv path (useful for 
Beverages as well).  Let the radio do the T/R 
switching.

Mike N2MG

On Fri, 09 November 2001, Pete Smith wrote:

> 
> 
> I've been researching band-pass filtering for SO2R, and it has occurred to
> me to try a different approach if the peer review sounds favorable.
> 
> What I'm planning is to build a box for each of my transceivers, containing
> a receiver protection circuit (diodes and a resistor), receive-level
> bandpass filters and a relay switching matrix to select the filters AND
> bypass them on transmit.  This would seem to offer several advantages --
> 
> I can use W3LPL's 3-pole receive filter circuit, which uses standard cap
> values and delivers performance that is probably superior to any commercial
> alternative except for W3NQN's expensive transmit filters.
> 
> I avoid issues with burning out the filter components from transmit power,
> particularly with a messy amplifier input SWR on some bands.
> 
> I avoid the reduction in drive to my SB-220, which really needs its 120 watts.
> 
> I can be fairly relaxed about the physical layout, since SWR is not the
> issue it is on the transmit side.
> 
> I realize that having a bandpass filter on the transmit side offers
> advantages too, in particular reducing harmonic output and wideband noise.
> But on balance, this seems like a good idea, plus it'll give me a project
> for the winter.  Comments? 
> 
> 73, Pete N4ZR
> www.qsl.net/n4zr
> 
> 
> --
> CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
> Administrative requests: cq-contest-REQUEST at contesting.com

________________________________________________
PeoplePC:  It's for people. And it's just smart. 
http://www.peoplepc.com 


--
CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
Administrative requests: cq-contest-REQUEST at contesting.com