Don,
Thanks for the tips. Here are some comments...
XG-1: Well, when I hook it up to my vintage Yaesu 757, besides
showing signal strength difference (S-0 and S-9 respectively), the tone
audio volume is very noticeable. Also, on 40 and 80 with the KX-1, I can
hear a marked difference between the two settings. When I say that there
is no difference, there isn't even a "switch-click" between the two
settings. Very, very weird. Also, the relative position of the XG-1 to
the KX-1 seems to have no affect (which, if the signal was somehow being
directly coupled, bypassing the antenna lead, I would expect). Also, I
expect that the signal at 50 uv should be blasting in. It only sounds
like a moderate level at this time.
Touching pre-mixer: I did notice that once my "crossed" wires on the
LFP board were fixed, I could get a "noise only" increase on at least
one other band (don't remember which) when touching the area, but on 20,
it was a true signal volume increase (confirmed with the PC's band scope
on the audio).
I'll dig up the old yellow core toroids and put them in for now.
Pre-3080: Since everything was built at the same time, its existence
as a "straight" KX-1 was a very short time and some months ago. I can't
remember most of yesterday, so who knows? {'-)
It may come down to actually measuring components or finding someone
willing to take a look at it for me (maybe who already has the proper
test equipment or has a known good KX-1 for a side-by-side comparison?).
Anyway, it's all I can do for right now. Thanks again for your help.
Regards,
kurtt
Kurt Pawlikowski, AKA WB9FMC
The Pinrod Corporation
[EMAIL PROTECTED]
(773) 284-9500
http://pinrod.com
Don Wilhelm wrote:
Kurtt,
Forget the 'scope, the levels from the XG2 are too small to drive a
'scope. The levels will be even less than the output of the signal
generator.
Do you have a crystal around that is somewhere in the 40 meter or 20
meter band? Plus a few parts in your junkbox? If so, you can build
up the crystal oscillator that is shown in the Troubleshooting section
of the K2 manual (download the manual from Elecraft website). And if
the oscilloscope is old, you probably do not have a 10X probe for it,
so also build the RF Probe.
At this point, I don't know what else to tell you - you will need some
basic test equipment to go much further. You can do some more visual
investigation.
Make certain the PC Trace cut is really cut. Be certain the added
wire is correct and that there is no contact of that wire with the end
of L6 nor point 'A'. Check and recheck the soldering of all the
capacitors in the LPF area as well as C1.
How strong is the actual signal from the XG2? Could it actually be
that the KX1 AGC is making the signals sound about equal? The fact
that they sound the same may not be a problem at all.
You will be better off putting the yellow core L1 and L2 in place for
the time being.
One thing that you can check with the 'scope is the Local Oscillator
injection to the mixer. You must have at least 200 mV peak to peak at
U6 pin 6 for the mixer to work correctly.
Remember that touching a probe to the area of T2 will always pick up a
lot of noise which results in an apparent increase in the signal being
picked up, but the actual signal strength usually does not increase.
Did this KX1 work well before you added the KXB3080? If not, then you
may have a problem somewhere other than just the front end of the
receiver.
73,
Don W3FPR
Kurt Pawlikowski wrote:
Don,
Still frustrated...
I removed the LPF board and removed both L1 and L2. I then "hard
wired" them in, just the way they would be with the board and the
relay "off." This had no affect on the symptoms: The XG-2 signal
still seems to be being coupled direct to the board (1 uv 50 uv
switch does not change tone volume). The next step is to drag down my
boat anchor oscilloscope and take some measurements. I expect the
signal level before T2 to be too small for my old equipment to see (I
don't think it'll do micro volts - I'll have to check though.).
Anyway, with the XG-2 on 20 meters, what signal strength (p-p) should
I be seeing at different points of the circuit? I'm thinking of
several points between the antenna up to the mixer with both the 50
and 1 uv output (I may have a hard time measuring the 50 uv level,
much less the 1!). Any other ideas are welcome...
Regards,
kurtt
Kurt Pawlikowski, AKA WB9FMC
The Pinrod Corporation
[EMAIL PROTECTED]
(773) 284-9500
http://pinrod.com
Don Wilhelm wrote:
Kurt,
From all you have said, I would believe that the problem is in the
KXB3080 low pass filter.
While I agree that your continuity test indicates no apparent
problem with the toroid lead tinning, check all the connections to
be certain there is a bit of solder on both sides of the board - if
not, view that connection with suspicion.
Make certain there is no contact with the green wire from L2 to the
lower connection of the red wire. The green wire must wrap around
to the back side of the LPF board and can inadvertently contact the
#4 termination of the wire for the red winding.
The best LPF testing is visual - look for any suspicious solder
connections. Yes, you will see a 17 MHz cutoff on the LPF if you
measure it without regard to disconnecting it from the rest of the
circuit and failing to properly terminate the filter (it is not 50
ohms at the PA transistor side, but I have not ever calculated the
proper termination).
Perhaps it is helpful if I tell you that the green winding is the
only active portion on 40, 30 and 20 meters. The red winding is
used for 80 meters and SWB band below about 6 MHz only.
Caution: The sensitivity of the KX1 is not as great on 20 meters as
it is on 30 or 40 meters. Bringing a finger (or antenna) close to
T2 or many of the receiver tuned circuits after the LPF will
normally result in an increase in receiver total output, but that is
actually an increase in broadband noise - under careful measurement
conditions, the desired signal strength will not increase even
though the overall noise level does. Spectrogram will show that is
true.
73,
Don W3FPR
Kurt Pawlikowski wrote:
Hi,
First, thanks for reading. Hopefully, it won't be boring for those
lucky K3 guys and gals...
CONFIGURATION
KX-1, 3080 upgrade. ATU currently removed and antenna jumper
installed for testing.Using XG-2 as a signal source. I have confirmed
the XG-2 seems to be working about as expected with another receiver
(about S-10 at 50uv and S-0 (but still in the speakers) at 1uv).
SYMPTOM
With normal operation, receive levels appear normal on 80 and 40 (I
can make contacts), but the XG2 is not peaking the KX-1's meter (I
used
the XG-2 to calibrate the meter). 20 meters has always seemed deaf to
me. I don't remember how well the XG-2 was received on 20 when I
calibrated it. Here's the real "kicker": On 20 meters, with the XG-2
attached, I hear *no* volume difference between 50 and 1uv (which
means
the KX-1's receiver is picking up the signal by proximity, not through
the antenna connection). If I touch the RX antenna connection almost
anywhere between the low-pass filter and the input of the Rx Mixer
(U6,
pin 1), 20 meters comes way up (from nothing to receiving moderately
weak signals and noise). Touching the RX antenna line on 80 and 40
appears to have little or no affect. Output power on 20 meters does
not
register full power, but I'm not sure if this is a calibration problem
as I don't have an accurate power meter. Also, when I couple a grid
dip
meter into the RX, when tuned to 30 or 20 meters, I get a marked "dip"
just at about 17 MHz.
------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.21/1456 -
Release Date: 5/20/2008 6:45 AM
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
