Hi all,
The question of how sensitive/insensitive the K3 is on 10m or higher
intrigued me enough to do a little testing. The bottom line is that I
did not find a great sensitivity loss on 10m or higher . I did see a
nominal sensitivity loss of maybe 3-4 dB on 10m and 6m relative to the
sensitivity on lower bands.
Here are some details of what I tested. I have an HP 8640 signal
generator with an outstanding decade attenuator that can reduce the
signal out down to nominally -130 dBm. So with this generator feeding
into a Kay attenuator unit, I could attenuate the signal down by
increments of 1 dB as far down as I would like. I calibrated the 8640 to
0 dBm when the 8640 attenuator was set to 0 dBm. I used a Yamaha headset
and listed to the CW signal out of the 8640 with the K3 set to SSB. The
internal preamp and attenuator in the K3 were turned off. The ATU was
bypassed. The audio bandpass was nominally 3 Khz. NB, NR, and NTCH were
turned off. I listened to the audio out of the K3 while adding
attenuation until I could not hear the signal. The attenuator setting
where I last heard the signal is the value in the table. The absolute
signal level at -130 dBm may not be exact, but the relative values
should be quite good.
Freq Receive threshold
1900 -135 dBm
3800 -135
7100 -136
14100 -135
18100 -137
21200 -135
24940 -137
28400 -132
50125 -133, with internal preamp on = -138, with external preamp on = -142
For my personal interests, I also tested an FT817 which was close at hand.
Freq Receive threshold
1900 -95 dBm
3800 -103
7100 -106
14100 -113
18100 -117
21200 -120
24940 -115
28400 -120
50125 -148 ( this one is very interesting )
Don, N0YE
On 12/13/2010 11:24 AM, Al Lorona wrote:
> This morning I got up and turned on the K3. I was shocked to find RFI from my
> Eveready flashlight on 7040, a birdie on 7160.1850192827354637, and with the
> noise blanker on I could hear splatter from my nextdoor neighbor's kilowatt at
> the bottom of the band. So I decided to update the firmware.
>
> The K3 locked up during the update. I had to power cycle everything four
> times.
> After the update, I could swear that the AFX started acting differently than
> before the update. Somebody told me it was my AGC settings. I started to try
> to
> measure the AGC response when I noticed that my filters were shifted and
> tilted.
> I phoned Inrad and exchanged my filters ten or eleven times until I got one
> that
> was flat with zero frequency shift.
>
> Something was still bothering me, so I hooked up my spectrum analyzer. Aha!
> Audio artifacts! These were solved easily by purchasing a pair of $9.95
> headphones at Pic 'n' Save.
>
> While troubleshooting this, I happened to notice that my
> RS232-to-USB-to-waveguide-to-banana plugs-to-RS232 adapter was acting up. A
> search of the archives told me that the driver and the chips used in this
> adapter were the wrong kind. Why in the world can't the K3 have an X-band horn
> in the back instead of that antiquated serial connector?
>
> When I tried to transmit, the guys on the net complained about the K3's key
> clicks, and its ATU wouldn't tune my 0.1 -j 4570 ohm antenna impedance
> properly.
> However, when I boosted the lower two TX EQ bands by +16 dB these problems
> seemed to go away. Well, that, and re-writing the K3's firmware to implement a
> windowing function that takes 2 GB of external memory to implement.
>
> With some of this extra memory I wrote a Yaesu receiver personality that makes
> my K3 distort exactly like my old FT-757. It's just like having that rig back
> in
> the shack.
>
> During this testing, I did have some trouble with FSK-D VOX without QSK in
> DATA-A Dual PB AFX BIN TEXT DEC NR 1-4 mode, but switching to AFSK with APF,
> PTT
> DVR N1MM through the soundcard with DTR always on and CONFIG:MON turned down
> seemed to help. However, I plan to ask Wayne for a high-priority firmware
> update
> to do this automatically.
>
> (By the way, it's a good thing I have this short call sign... I can say my
> call
> 15 times in one ten second DVR memory! Thank goodness for the vanity call sign
> system.)
>
> I *think* everything's okay now except for there's still something wrong with
> the receiver which I can't quite pinpoint, and I know it couldn't possibly be
> related to all of those years touring with The Who and standing in front of
> their amplifiers night after night.
>
> Happy Holidays,
>
> Al W6LX
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