[Elecraft] Re: K1: Band 2 (15M) low audio and a steady tone on one frequency

[Mike Morrow]

>... the 15M receiver has very poor reception and a very loud,
> steady tone on one frequency.  The tone's bandwith is very narrow...
>
>...has anyone any idea what may be the cause of the steady tone?
>...initial hunch is that it is a symptom of a short, possibly in the
>crystal.

It would help if you state at what indicated frequency you hear the tone.  Anyway, **ignore** your hunch in this case.

No doubt you are hearing the seventh harmonic ("birdie") of the K1's VFO on 15m.  This frequency varies from unit to unit.  On my K1 it occurs near 21072 kHz, where my K1's VFO is just above 3010 kHz.  The tuning seems very sharp because as one tunes upward, the VFO frequency goes downward, which makes the reception of the VFO's seventh harmonic appear vary narrow as one tunes across it.  The receiver frequency is changing in one direction, while the received VFO signal frequency is changing in the opposite direction.  Thus, very "sharp" birdies are a dead give-away of reception of an internal VFO harmonic on the K1.

This harmonic near 21072 kHz is the worst case of a birdie that will be be found on any of the K1's official bands (80m to 15m).  Its actual frequency will vary a little from one K1 to another due to variations in the frequencies of the product detector and filter board heterodyne crystals.  The birdie will seem very strong if your receiver is working but you have no antenna connected, or the antenna signal isn't making it to the receiver front end.  Since it seems so loud on your set, that could indicate that the receiver is working fine (and picking up this harmonic), but you've lost connection to the external world (antenna) which normally provides noise and signals to compete with the harmonic.  Beware...sometimes, a very dead 15m band will almost duplicate the effect of an antenna disconnection.

What can be done about the birdie?  Not much.  Fortunately, most 15m activity is below the birdie, the birdie is narrow, and an open band with signals will diminish its perceived effect.

Mike / KK5F