[Boatanchors] Receiver Filter Adaptor and Thoughts on ProjectsIn Genera

[Gary Schafer]

Hi Dave,
Have you looked at the Kiwa filters? They have some nice ceramic filters
with amps built in with a small package. Made to drop right in.
http://kiwa.com/index.html

Years ago I added a tandem mechanical filter to my 75S-1. I used a small
transistor amp with a gain pot to compensate for the insertion loss. Very
simple, a couple of resistors and capacitors and a choke to isolate the
filter from voltage. Put it in a small mini box with a slide switch on the
input and output so the filter could be switched in and out. Remoted it to a
convenient mounting place with short lengths of small coax.

73
Gary  K4FMX

> -----Original Message-----
> From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf
> Of David Stinson
> Sent: Tuesday, February 16, 2016 9:41 AM
> To: boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] Receiver Filter Adaptor and Thoughts on
> ProjectsIn Genera
> 
> Taking all the good points into consideration and working on a
> "version 1.1" of the filter adaptor for the TCS receiver. The
> hard part is not the circuit; it's figuring out where to put the
> parts on the board so it can be wired most efficiently and with
> least feedback/leakage between the two stages. Will pass that
> along once I puzzle it out, Bill. I'd be embarassed for your
> readers to see photos of this cobbled-up "Version 0.9 Beta" of
> the thing. ;-)
> 
> Also looking for alternatives. Yes, I know- I feel a little like
> a prostitute for even thinking of a "sand state" solution, but
> dang-it Mechanical filters can be expensive. Saving money is a
> good cure for uneasy feelings ;-).
> Come on "smart people:" By now there ought to be some
> single-chip active filter thingie that can do this without trying
> to build a mini-computer in that space.
> 
> Some thoughts on these projects in general:
> 
> I do them for my own curiosity and satisfaction. I write them up
> to share the idea and hope some generous person smarter than me
> will suggest improvements (and they almost always do, Lord bless
> them). I also write them in hopes someone else will build the
> thing and, together, we can make it work even better.
> 
> There's an important reason I try to keep any solution very
> simple and basic. It's an iron, unbreakable law of ham radio
> tinkering.
> 
> ****
> The Law of Pernicious Parts Count:
> For every additional part in a project beyond eight,
> the number of people building the project will be halved.
> ****
> 
> IMHO, there's no point in writing-up some mini-computer DSP thing
> with 100 parts and needing a Masters in digital engineering to
> understand, just to address the bandwidth issue in a boatanchor
> receiver; no one is going to build the thing or even read to the
> end of the piece once they see the diagram. No matter how great
> a solution it might be, it's a waste of precious time and effort
> to write-up such a contraption. If you want to build one for
> your own satisfaction, that's great. Go for it. Just don't
> expect anyone else in our community to build one. Most of us are
> older now. Our time, patience and resources are very limited.
> We aren't going to attempt a college course in digital
> engineering this late in the game just to improve a vintage
> radio. "If it ain't easy, it ain't happening."
> Just one man's musings. YMMV of course.
> 
> GL OM ES 73 DE Dave AB5S
> 
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