[MRCA] Pondering Crystals for the BC-620 radio

[Mark K3MSB]

Mark

Graph the crystal frequency vs  BC-620 output frequency for several
crystals.

If they are all on a line then a linear relationship exists.  Knowing two
points on a line you can then determine the general equation of the line
and thus compute the BC-620 output frequency for any crystal frequency and
vica versa.

73 Mark K3MSB

On Tue, May 29, 2018, 11:36 PM WW2RDO via MRCA <mrca at mailman.qth.net> wrote:

> Something to ponder:  The BC 620 radio is a 2 frequency, crystal
> controlled FM radio operating phone  between 20.0 to 27.9 MHz FM.  CB radio
> frequencies are set on specific frequencies between 26.9650 MHz to 27,4050
> MHz FM.   Unless I'm missing something, if the crystals are cut correctly,
> the BC-620 should be able to operate on 2 CB channels if the crystals are
> cut precisely and correctly..  Here's the rub - the crystals made for the
> BC - 620 operate in an oscillator circuit. Is there a formula to cut
> crystals for the BC-620 to have the radio work on specific CB channels ?
> Crystal # o in the radio set is actually rated at 5.7067 MHz, but when
> installed in the oscillator circuit in the BC-620, transmits and receives
> on 20.0 MHz.  Crystal # 79 is actually cut for 8,3400 MHz, but when put in
> the oscillator circuit in the BC-620, operates on 27.9 MHz.
>
> Has anybody actually had custom crystals cut for a BC-620 to allow it to
> work on CB Frequencies?  If so, is there a formula used to determine what
> frequency the crystal should be cut for?  I know that running CB
> frequencies isn't exactly in anybodies wheelhouse, but if this could be
> figured out, perhaps the BC-620 becomes a popular player in the vintage
> military radio world, along with perhaps other vintage radio sets.
>
> Mark D.
> WW2RDO
> ______________________________________________________________
> MRCA mailing list
> Home: http://mailman.qth.net/mailman/listinfo/mrca
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:MRCA at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/mrca/attachments/20180530/e5c32252/attachment.html>