[ARC5] BC-453/Q5er Converter

Sun Sep 26 04:50:15 EDT 2010

Hi Henry,

If one were to design the XTAL osc with a tuned tank whose resonance is band
switched, there is usually enough second harmonic energy in a Colpitts to
generate the doubling level needed by a diode mixer.  But that's extra
swtiched circuitry.  I built a Colpitts without any tank and took the signal
off a 50 ohm resistor in series with the ground side of the crystal.   The
signal at that point is pure and the resistor provided the needed source Z
for the passive diode mixer.  Likewise, the mixer requires a 50 ohm IF
termination that holds that Z at all possible mathematical freq
outputs.  Properly driven and terminated, a double-balanced diode mixer like
the SBL-1 does an awesome job.  I mounted the FT-243 socket where it was
easy to drop in the rock of my choice. If one were to add an additional cap
switch on the preselector, this converter would have a third band with the
mere choice of another rock.  The double-tuned preselector is the only tuned
circuit used.

The 453 has a small cap in series with the input stage.  The coupling is
fairly light and the Z high.

There is a navy version of the 453 that has balanced inputs for a loop.

Dennis AE6C
On Sat, Sep 25, 2010 at 11:07 PM, Henry Mei'l's <meils at get2net.dk> wrote:

> Dennis,
>
> Do you/can't you use the 3.5 MHz xtal's 2nd harmonic for 40M
> in a doubler circuit switched via a ganged toggle or wafer switch?
> Why should the mixer have 50 ohm termination when the ant. input of the
> BC-453
> probably is not that  (maybe to match available coax feeder line)?
> -- surely doesn't really matter because of ample converter output.
> ( BTW  what is the specified/aprox. actual input Z of a BC-453 and the
> higher freq.
> receiver units in the ARC-5 series? -- I would guess, in the same range as
> the xmtrs.
> But the BC-453 could also be used with a loop: I have one unit with an "A
> L"
> switch)
>
> Henry, Cph.
>
>
>
> ----- Original Message -----
> From: "Dennis Monticelli" <dennis.monticelli at gmail.com>
> To: "Discussion of AN/ARC-5 military radio equipment."
> <arc5 at mailman.qth.net>
> Sent: Sunday, September 26, 2010 6:32 AM
> Subject: Re: [ARC5] BC-453/Q5er Converter
>
>
>  > Harvey,
> >
> > I designed and build a two-band (80/40M) solid state converter for my
> > BC-453-B.  I built it over a piece of PCB acting as both the ground plane
> > and substrate. It was mounted over the Dyno area and fed with the same
> > 12VDC
> > that powers the filaments (this ARC-5 was converted when I got it).  I
> > used
> > a double-tuned front end preselector in the form of a two-section air
> > variable with a torroid for each section.  A small toggle swtich threw in
> > extra C for use on 80M.  A JFET Colpitts XTAL osc served as the LO.  Plug
> > in
> > a 3.5 rock for 80M or 7.0 for 40M and the dial remains calibrated.  The
> > mixer is a Mini-Circuits SBL-1 feeding the source of another JFET
> > that serves as the mixer's 50 ohm termination and outputs to a choke load
> > in
> > the drain.  A piece of RG-174 skinny coax runs from the converter to the
> > front antenna terminal.  I also added a 5K to 8 ohm transformer on the
> > board
> > to convert the audio impedance.
> >
> > It works FB without image, overload or stability problems.  There is some
> > conversion gain so the noise of the BC-453 is not a concern.  I've used
> it
> > by itself and also with a T-22 for on-the-air work.
> >
> >
> > Dennis AE6C
> >
> > On Mon, Sep 20, 2010 at 11:23 AM, <hmitchell3 at comcast.net> wrote:
> >
> >>
> >>
> >> I am looking for circuits for an 80 or 80/40 meter converter for the
> >> BC-543. I have several old circuits but they involve coils and IF
> >> transformers that are not readily available. Solid state is OK, I just
> >> want
> >> to finally have a working Q5er.
> >>
> >>
> >>
> >> Thanks,
> >>
> >>
> >>
> >> Harvey, K5YU
> >> ______________________________________________________________
> >> ARC5 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/arc5
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:ARC5 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> > ______________________________________________________________
> > ARC5 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/arc5
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:ARC5 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.856 / Virus Database: 271.1.1/3158 - Release Date: 09/25/10
> 08:34:00
>
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>