[AMRadio] RE: Receiver update.

[Gary Schafer]

Brett,

When you are done with that build a crystal controlled converter for the
higher bands to go in front of the receiver.

73
Gary  K4FMX


Brett Gazdzinski wrote:

> Hello all AM,ers.
>
> I got the electrical design and building parts done on the homebrew
> receiver today, that just leaves the front panel to do.
>
> The receiver works very well indeed.
> I ordered a Kiwa filter module, and received it in two days
> along with nice hand drawn diagrams on how to incorporate it
> in various tube receiver setups.
>
> These things are very nice...three ceramic filters
> and an input and output amp.
> They come with pig tail cables that you patch into
> points on the IF strip.
> It runs off 4.5 to 36 volts, has zero loss
> (as long as you re-tune the IF transformers)
> and they work well indeed.
> I got the 5.5 KHz filter, and tried it in various spots in the IF.
> Its best to put it at the mixer output, otherwise, strong signals
> out of the filter pass band, but in the IF pass band run amuck
> and cause all sorts of overloading.
> I did not notice this while listening on 40 meters, but
> 80 meters turned into a distorted mess!
> Moving the filter to the mixer output solved this problem.
>
> These filters can take an old boat anchor receiver and turn it into
> a nicely selective receiver.
> 5.5 KHz seems a good bandwidth to pick, especially if you have
> less than perfect hearing and cant hear the real high stuff anymore.
>
> The RF amp gain control works great, the IF gain control took
> some playing with, otherwise the scope output got distorted.
>
> I did the muting circuit with a small relay that opens up the last IF
> amp B+ feed.
> Its run off 7 volts of rectified and filtered filament power,
> that also does the Kiwa filter.
>
> Tuning rate is nice, fidelity seems very good, it seems very stable
> in frequency and all other respects.
>
> I compared it to the r390A over and over, and to me, it seems
> like the homebrew works as good or better under most conditions.
> The homebrew only does 80 and 40 meters, and they are easy
> frequencies to get working well without a lot of special
> design.
> The filter really made a big improvement in the way the
> receiver works.
>
> Now its onto drilling holes in the front panel, paint, labeling, etc.
>
> While its been a LOT of cut and try, building a receiver
> that works as good as what you are likely using is not
> hard or impossible as long as you don't want lots of
> bands or real high frequencies.
>
> Brett
> N2DTS
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