[Elecraft] K3 audio output v headphone sensitiviy

[Bill W4ZV]

K7TV wrote:
> 
> What is adequate headphone sensitivity may be highly dependent on
> operating mode and rig selectivity.
> Case in point: Many years ago I ordered an FT-1000 and a Heil headset
> (forget which model). Headset volume was fine for voice, and for CW using
> a wide filter. But the FT-1000, like the K3, can be set to very narrow CW
> filtering. This brings down the noise to far below what you have at more
> "normal" bandwidth. On a quiet band one can then work CW stations that are
> extremely weak. In my case, that is where the Heil headset became
> unuseable, because of inadequate volume. In my opinion, when trying to
> copy the weakest possible CW signal for a given bandwidth, the gain needs
> to be high enough that the noise level is quite loud. I sent the Heil
> headset back to the store. This episode begs the question: The K3 being
> famous for its "quiet" receiver, does it have enough rx audio gain to
> provide a loud background noise level in CW mode using the 50 Hz
> bandwidth, for an average speaker or for a reasonable headset (not Heil!)?
> 

I don't agree that's the best way to copy weak signals...but that's another
issue in itself.

http://www.eham.net/articles/9982  (A few days I broke that record at 26
uW).

The sticker on my BM-10 states "IMP 32 OHM", which is what I measure for
each side.  Using it:

50 Hz BW, max RF Gain, AGC-Fast and CONFIG: AF GAIN HI (default setting). 
AF GAIN is set to 12 o'clock for a comfortable level listening to a dummy
load (i.e. strictly RX background noise).  With any sort of band noise I
would need even less AF GAIN.  The 1 uV output (-107 dBm) from an XG1 is
uncomfortably high and I backed off AF GAIN to ~10 o'clock for that.  Both
of my Heil ProSet headsets measure >200 ohms per side and they also have
plenty of output with the K3.  BTW I normally have CONFIG: AF GAIN set to LO
for all my headphones.

I can't explain others' problems but all 3 of my Heil headsets have plenty
of AF gain with the K3...even for very weak signals buried in noise.

73,  Bill







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