[AMRadio] RE: Another receiver update...

Fri Mar 1 12:25:22 EST 2002

Brett,  that is  what  Heath did in the apache TX-1  vfo. Hammarlund
also did it in the HQ-110.  HQ170 also?   As for the 6J5 how  many types
are there?  Metal or glass?   Russ

>From: Brett Gazdzinski <brett.gazdzinski at wcom.com>
>Reply-To: amradio at mailman.qth.net
>To: amradio at mailman.qth.net
>Subject: RE: [AMRadio] RE: Another receiver update...
>Date: Fri, 01 Mar 2002 08:30:56 -0500
>
>Bacon,
>Its possible I could install a small filament transformer
>and have it powered all the time...the 6j5 is only .3 amps I think.
>
>I also thought of RF chokes as soon as you pointed out the cathode was 
>above
>RF ground.
>
>2kc after 10 minutes is not bad, but that sort of depends on the
>particular 6j5 I use, so I would like to try some things
>so as to be able to use any 6j5 tube there.
>
>I will try the RF chokes...
>
>The receiver is really working well, last night I listened
>to 80 meters, conditions were quite weird, with fast flutter,
>and long skip, and I heard stations in New England working
>w5 stations in Texas, and I could hear both sides quite well,
>100% copy plus, while they had a rough time copying each
>other, likely due to the added distance between them,
>but the home brew receiver did a fine job pulling
>everything out.
>It still strikes me as odd that the receiver seems to work better
>than the r390a I have (yes its been aligned)....
>
>
>The next project is a home brew exciter.
>Since I have two big rigs to drive, I figure I will actually
>make two separate output stages, so I can tune one up on
>80, the other on 40, and run different (pre set) power outputs.
>That way, I wont have to tune anything when going between
>80 and 40 meters except for the frequency...
>
>A pair of 6146's, one for each rig should do nicely....
>
>I found a nice national dial on ebay, but some scum outbid
>me at the last moment!
>
>Matching dials would be the cats meow!
>Or maybe I should think about a digital readout for both
>the receiver and the exciter....
>I think kits are available to do this...
>
>
>Brett
>N2DTS
>
>
>
> >
> >
> > Hi Brett,
> >
> > On my VF-1, I ran the 6AU6A filament all the time, although I had it
> > on reduced voltage when the unit was off.
> >
> > I didn't do this, but you might float the 6J5 filament leads with
> > some kind of RF chokes, and RF-bypass them to the cathode.  Consider
> > any DC drop to the filaments and any heat in the chokes when doing
> > this, though.
> >
> >   Bacon
> >
> >
> > ----- Original Message -----
> > From: "russ dworakowski" <wb3fau at hotmail.com>
> > To: <amradio at mailman.qth.net>
> > Sent: Wednesday, February 27, 2002 11:47 AM
> > Subject: RE: [AMRadio] RE: Another receiver update...
> >
> >
> > > Hey Brett,  you can use a separate  filament transformer  for the
> > 6J5
> > > and  leave it running  all the  time.  That will  solve the  warm
> > up
> > > problem.  Russ
> > >
> > >
> > > >From: Brett Gazdzinski <brett.gazdzinski at wcom.com>
> > > >Reply-To: amradio at mailman.qth.net
> > > >To: amradio at mailman.qth.net
> > > >Subject: RE: [AMRadio] RE: Another receiver update...
> > > >Date: Tue, 26 Feb 2002 20:36:51 -0500
> > > >
> > > >Bacon,
> > > >I think you are right on the money.
> > > >Looking at the oscillator design I used, the cathode is
> > > >above ground for rf, but the filament is bypassed to ground.
> > > >(RF choke to ground)
> > > >
> > > >There is another way to do it with a grounded cathode,
> > > >I found a good design in the October 1957 QST, but it
> > > >would require a lot of changes, the tuning cap
> > > >has to come off ground along with the coil.
> > > >
> > > >I am not sure I want to start over with making coils,
> > > >trying caps, etc, so I will see how it acts with the NPO
> > > >caps.
> > > >As it is, with the glass 6j5 in there, it drifts
> > > >about 2 kc from a cold start...
> > > >Not unreasonable for a home brew receiver, I just need to
> > > >let it warm up for 10 minutes before its accurate...
> > > >
> > > >Thanks for the tip,
> > > >Brett
> > > >N2DTS
> > > >
> > > >
> > > > >
> > > > > Hi Brett,
> > > > >
> > > > > I once read about internal cathode interface resistance in
> > > > > oxide-cathode vacuum tubes.  Evidently the various layers of
> > > > > the cathode can make intermittent internal contact, and this
> > > > > can cause frequency shifting and drift.
> > > > >
> > > > > Try adding a low value resistor in series with the cathode,
> > > > > maybe a few hundred ohms to 1.5K or so, and see if it
> > > > > helps...  assuming it does not stop oscillation altogether!
> > > > > I did this with the 6AU6A in my Heathkit VF-1, and it helped.
> > > > >  But I still had to select tubes for best performance.
> > > > >
> > > > >   Bacon, WA3WDR
> > > >
> > > >_______________________________________________
> > > >AMRadio mailing list
> > > >AMRadio at mailman.qth.net
> > > >http://mailman.qth.net/mailman/listinfo/amradio
> > >
> > >
> > > _________________________________________________________________
> > > Get your FREE download of MSN Explorer at
> > http://explorer.msn.com/intl.asp.
> > >
> > > _______________________________________________
> > > AMRadio mailing list
> > > AMRadio at mailman.qth.net
> > > http://mailman.qth.net/mailman/listinfo/amradio
> >
> > _______________________________________________
> > AMRadio mailing list
> > AMRadio at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/amradio
>
>_______________________________________________
>AMRadio mailing list
>AMRadio at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/amradio

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.