Bill,
I may have exaggerated when I said the noise needs to be quite loud,
but what I meant was the it should be loud enough to be easily heard,
or else the desired signal won't be easily heard. (I do think I can copy
a signal that is about equal to the noise level.) Probably when you
copy a very weak signal, you also have it right at the noise level?
We may differ on what is a comfortable signal level of course.
The bottom line w.r.t. the FT-1000 (D) was that I could not without
straining copy through the Heil headset (but could copy through
speaker) with dual 250 Hz xtal filters and the audio cw filter on,
and the audio volume control at max. I sent the Heil headset back
to the store. I got this equipment back around 92/93, and think at
that time Heil may have had only one headset model available
(neglecting any variations in attached microphones). Do you know
what the model designation might have been on that headset?
Maybe they have changed ones manufactured later to be more
sensitive?
Thanks for the specific information on the K3 settings. My K3
is not here yet, and I am trying to understand if I need to plan
to get an outboard speaker/amp in order to get sufficient
audio volume for those weak cw signals on 10m and 6m
where the band noise is low.
Erik K7TV
----- Original Message -----
From: "Bill W4ZV" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, July 14, 2008 11:35 AM
Subject: Re: [Elecraft] K3 audio output v headphone sensitiviy
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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