[R-390] R390A Turns Counter BFO option?

[nryan at mchsi.com]

Fellow Mavens,

The BFO range can be expanded by removing the rotation limiting tang under the BFO knob.  Be advised that doing so risks damage to the very fragile powdered iron core inside Z502.  Turn it too far and it will break.

A broken powdered iron core sometimes can be repaired with careful application of JB weld.  Check that the repaired core is straight and true inside the coil.

If a MicroDial is added, zero it on 455 kHz and don't force it against the core's travel limit.

73 de Norman, KG4SWM

-----------------

On 3/13/2011 2:08 PM, Nick England wrote:
> FWIW -From "Cryptologic Collection Equipments" NAVEDTRA 10251 (1977)
> http://www.navy-radio.com/manuals/crypto-equip.htm
>
> BFO PITCH.-The BFO PITCH control
> varies the output frequency of the BFO above
> and below 455kHz. The normal R-390A BFO is
> designed to vary by 3kHz above and below
> 455kHz. Many of the R-390A receivers with
> which you will come into contact have a
> modified BFO pitch control, called a
> MICRODIAL. This modification enables the
> BFO to be varied over a 26kHz range (13kHz
> above and below 455kHz.)
>
> cheers,
> Nick K4NYW
> www.navy-radio.com

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