Fw: [R-390] 4KHZ filters

Mon, 12 Apr 2004 19:35:38 +1000

----- Original Message -----
From: "Bernie Nicholson" <[email protected]>
To: "D. ball" <[email protected]>
Sent: Monday, April 12, 2004 11:59 AM
Subject: Re: [R-390] 4KHZ filters


> Hi agn not sure of ur name but the only problem with newer and ceramic
> filters will be the matching the newer collins filters have gone over to
> peizo transducer [more efficient ] and the ceramic filters I have used
> [Murata ]are also different impedence to the original which are quiet low
> the filters on chuck R s site are very expensive abt 250 $ from memory ,
> I used murata filters in my home brew copy of the Racal Ra17 my rx is
solid
> state but the same basic block diagram , u can hear stations close in with
> the 390a because of the steepness of the filters and because of the superb
> dynamic range of the tracking preselector and tunable IF system , abt the
> PTO there are a number of cams in the vfo that u adjust to linearize the
> unit it tunes 1 mhz in ten turns and the linearity can be brought back
into
> line each turn, I use the dial from the ten turn pot and draw a graph
using
> the hp5245 to check the out of linearity amount on each turn ,I then
scribe
> a mark across all the cams so I can put them back to square one if I have
to
> start agn after a few adjustments it gradually gets more and more linear
> then u have to put the covers back on and I had to adjust the end stop
> adjustment slightly -, I power up the unit in a jig that I have made and
the
> ten turn pot dial  does the job very well , I can assure u that the
problem
> is not in the gears , The PTO I like best is the COSMOS which has a linear
> tracking ajistment every 25khz there are 40 adjustments and u can adjust
it
> in situ whithout taking of the covers my telydyne rx has one of these I
also
> have capehart and a stewart electronics and a imperial electronics, all
> lovely sets nothing to choose between them , I also have 51S1 75S1 75S3
KwT6
> ARC58 ArT13 and much more all going and a lot of fun ---- Original
> Message -----
> From: "D. ball" <[email protected]>
> To: <[email protected]>
> Sent: Sunday, April 11, 2004 8:47 PM
> Subject: RE: [R-390] 4KHZ filters
>
>
> > well getting the filter apart was easy, i used a hot air rework station
to
> > do it, I could find nothing to indicate what the failure was. i even re
> > assembled the filter, sweep it, then decided to take it apart again
> > determined to find the fault but ended up breaking one of the little
wires
> > spot welded inside.. this filter case will get stuffed with ceramic
> filters,
> > or maby a modern collins filter..   people have said the most used
filter
> > goes bad, ??   something took out my filter, not sure what it was..
sure
> > was no foam to go bad, this collins filter had rubber inside.
> >
> > as far as the PTO. it really make me question what causes that..  if you
> cal
> > the PTO with the dial adjust at .000 and then move 300kc you notice you
> are
> > off right?  ok, I move up to .700 and readjust, same result, dead on fo
> > about 300kc either way.  because of this i question the the gear train,
I
> > think a pencil mark on the shaft of the PTO will tell me what is going
on,
> > it is very possable that this is the gear box and that the adjustment in
> the
> > PTO makes up for that..  just a thought..  something like this does not
> > bother me.. I can always re-cal the pto then tune in. but the filter
> really
> > bugs me, the most amazing thing about the r390a is it's ability to hear
a
> > station a few kcs away from a powerful one, i have never heard a radio
do
> > that.. not like this thing, plus you can hear the flat top of the
collins
> > filters, it really sounds good, I have found pleanty of replacements,
just
> > bums me out the 4kc filter is gone..  i just bought this radio..   great
> > shape..  just out one filter..
> >
> > ok,
> > thanks
> >
> > >From: "Bernie Nicholson" <[email protected]>
> > >To: <[email protected]>
> > >Subject: [R-390] 4KHZ filters
> > >Date: Sun, 11 Apr 2004 16:12:25 +1000
> > >
> > >I think that it would be a very difficult job to repair filters a jig
> would
> > >have to be made also the parts internally are SPOT welded together .
the
> > >smallest welds I have seen ever . to remove the ends off the filters I
> used
> > >a Jewlers gas torch you have to be quick and when the solder melts you
> > >remove the ends abt 1/8 inch so as not to break the fine wires, BUT to
> get
> > >the filter assy. out you have to  cut the wires to the end cap on one
end
> > >then you can slide out the resonator assy. the filters transducers DC
> > >resistance is 48 ohms  , I think the cheapest way out would be to fit
> > >Murata ceramic filters which are available in various bandwiths at
455khz
> ,
> > >on a different subject I have just linearized a PTO by making a little
> jig
> > >and using the dial from a ten turn pot to draw graphs untill I got a
> > >straight line response It took abt 5 hours and when I put the cover on
I
> > >only had to make a slight ajustment to the end stop and it is within
300
> hz
> > >from one end of the dial to the other , A win for me anyway regards to
> > >everyone Bernie Nicholson VK2ABN
> > >
> > >
> > >--- StripMime Report -- processed MIME parts ---
> > >multipart/alternative
> > >   text/plain (text body -- kept)
> > >   text/html
> > >The reason this message is shown is because the post was in HTML
> > >or had an attachment.  Attachments are not allowed.  To learn how
> > >to post in Plain-Text go to: http://www.expita.com/nomime.html  ---
> > >_______________________________________________
> > >R-390 mailing list
> > >[email protected]
> > >http://mailman.qth.net/mailman/listinfo/r-390
> >
> > _________________________________________________________________
> > Persistent heartburn? Check out Digestive Health & Wellness for
> information
> > and advice. http://gerd.msn.com/default.asp
> >
>