[Elecraft] KX3 PSK-31 IMD on Low Batteries

[Don Wilhelm]

Kevin,

As you noticed, the IMD of any transceiver is degraded when operating at 
a voltage below its design point.
That fact is independent of the mode.
Certainly, the KX3 will "work" down to 8 volts, but not without 
consequences.

I do not know the design point for the KX3 PA, but I would figure it is 
11 volts based on using fully charged NiMH batteries.

73,
Don W3FPR

On 8/9/2016 11:00 AM, Kevin - K4VD wrote:
> I probably should have expected this and took action before anyone had to
> mention it.
>
> I was using a KX3 on internal battery. I was running PSK-31 using DATA-A at
> 3 watts. I use an external soundcard (ASUS Xonar U7) and the laptop is an
> HP Spectre running Win10 and DXLab suite. Rig control and the sound card
> run off a USB hub. Antenna is a 160 meter OCF and I was on 40 meters.
>
> The last QSO was with Eric KB3CNK. He's a few hundred miles from me. He
> reported my signal was strong but that he saw some harmonics or splatter on
> his waterfall.
>
> I immediately backed down on the audio a little bit (5th bar flickering to
> 4th bar flickering) but he said it made no difference. My next thought is
> some RF getting back into the audio which, with an OCF, wouldn't be unheard
> of. I wasn't looking forward to tracking that down. I've got puka beads at
> the feed and rig ends of the coax.
>
> Then I noticed my internal battery voltage was down to 8.8V key down. I put
> on the external battery which brought it up to 12.1V key down and he said
> the signal looked beautiful (still 4th bar flickering).
>
> The panic subsided. I'll need to be a little more aware of my battery
> voltage in the future. Viva la simple fixes.
>
>