[AMRadio] RE: new home brew receiver progress

Wed Oct 22 19:22:07 EDT 2003

Eddy,
http://www.kiwa.com

There filters are the cats meow, the one I used was a 5.5Kc
filter, very good overall for AM.

They make filters every .5 Kc, like 3.5, 4, 4.5, 5,5.5, etc.

The filters are very small, and have wires out to connect to
the IF in, IF out, and power (5 to 30 volts dc).
Its easy to rectify some filament voltage to power the filter,
and its easy to tack the wires into the if, say after an IF transformer,
and into an IF amp grid.
They work VERY well, very sharp, close to a good mechanical
filter.
Cost is about $50.00.

Brett
N2DTS

> -----Original Message-----
> From: amradio-admin at mailman.qth.net
> [mailto:amradio-admin at mailman.qth.net]On Behalf Of Eddy Swynar
> Sent: Wednesday, October 22, 2003 3:39 PM
> To: amradio at mailman.qth.net
> Subject: Re: [AMRadio] RE: new home brew receiver progress
> 
> 
> Hi Brett,
> 
> I sure would appreciate some more info re. those "Kiwi" IF filters...!
> 
> Where do you buy them...? What are their different 
> bandwidths...? Do they
> have a website...?
> 
> Hope to hear from you soon, with thanks in advance!
> 
> ~73~ Eddy VE3CUI - VE3XZ
> 
> 
> 
> 
> 
> 
> ----- Original Message -----
> From: "Brett Gazdzinski" <brett.gazdzinski at mci.com>
> To: <amradio at mailman.qth.net>
> Sent: Tuesday, October 21, 2003 2:39 PM
> Subject: [AMRadio] RE: new home brew receiver progress
> 
> 
> > I am making good progress on the new receiver.
> > I have tried lots of circuits for the local oscillator,
> > and have come up with a good circuit.
> > Its very hard to build a good stable oscillator without
> > complex coils with feedback windings.
> >
> > I found a circuit in the Bill Orr handbook, out of the C-W 
> man's receiver
> > that uses one untapped coil, one side goes to ground, a variable cap
> across
> > the coil to ground, an RF choke in the cathode, and a pair of caps
> > in series from the grid to ground, the center (between the caps)
> > goes to the cathode for feedback.
> >
> > I tried various coil types, various size ceramic slug tuned forms
> > with various gauge wire on them, pre made phenolic slug tuned forms
> > that I unwound some wire from till I got to the correct frequency,
> > large ceramic coil forms, and B+W coil stock.
> >
> > The best results are from the B+W coil stock, a much higher
> > Q coil, gives less harmonics out.
> >
> > I changed the design some, instead of using the 6U8, I used a 6C4,
> > since the ARRL handbook says a separate oscillator tube results
> > in a more stable receiver.
> > 2nd harmonics are down more than 45 DB with the B+W coil, 
> much less with
> > some of the others, some generate harmonics out to 60 Mhz
> > or so!
> > The oscillator keeps working down to as little as 10 volts 
> on the plate,
> > and I may run it at 75 volts.
> > I just tack parts together on the workbench, hooked up to
> > the old heathkit variable high voltage power supply,
> > so the finished product should actually work better, with
> > short wires and a sensible layout.
> >
> > To switch between 80 and 40 meters, all I need to do is
> > short part of the coil to ground.
> > One end is always connected to ground, and a tap to
> > ground will give 40 meters, I tested it, and it works well,
> > no drop in output, no increase in harmonics.
> > I plan on putting the coil and switch in a small box to isolate
> > it.
> >
> > I think the mixer tube will be a 6AH6, and I will try to inject
> > the osc into the cathode.
> > If that does not work well, I can inject it into the grid.
> > The ARRL 1967 handbook has lots of good info about
> > this sort of mixer stuff on page 99.
> >
> > I think the IF amps will be 2 or 3 6BZ6 tubes.
> > The same handbook gives circuits and values for various tubes.
> >
> > I have a circuit for the low distortion detector, and the S meter
> > amp, but have to change from octal tubes to 7 or 9 pin
> > tubes, from a 6SN7 for the S meter circuit, and the detector needs
> > a diode, and a triode, like the 6SN7.
> >
> > I may be able to drive the S meter directly with an IF
> > amp plate current, like the Gonset G76 does.
> > I found a nice S meter from an old heathkit receiver
> > on E bay a while ago. It can be lit up from the back, a nice touch,
> > and its only an S meter, not out of a transceiver with plate current
> > and so on..
> >
> > I have the chassis, the side supports and front panel,
> > the IF transformers, the digital frequency display, the tuning cap
> > and various reduction drives, nice ceramic tube sockets, the antenna
> > tuning coil forms, loads of VR tubes, and all the other tubes.
> >
> > The Kiwi filters have not arrived yet, and I may need to buy a
> > power transformer, to give 200 volts out with choke input,
> > and filament windings.
> >
> > Its really getting to be ham radio season, with building and
> > operating, and I am having FUN!
> >
> >
> > Brett
> > N2DTS
> >
> >
> > _______________________________________________
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> > AMRadio at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/amradio
> >
> 
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