Lee,
That is better, but I normally expect 3.5 watts with a true 13.8 volt
input. Measure the voltage at the KX1 end (remove the insulating handle
from the power cord to gain access). Then try a TUNE and measure the
voltage again. If it drops substantially, check the connections at the
power source to be sure they are tight. I normally recommend using #18
wire or larger to reduce the voltage drop.
You did not mention the wattmeter that you were using. Many analog
wattmeters are only accurate to 20% of the full scale reading - that
means if using a 20 watt scale, the reading could be incorrect by as
much as 4 watts at any point on the scale, making them not reliable for
low power work. It is more accurate to connect a god 50 ohm dummy load
and measure the RF voltage across that load and 'do the math' to figure
the power output. There are a few accurate wattmeters available, and
most of them are digital - the Elecraft WM1, W2, or the Telepost LP-100
and LP-200 are ones I know I can trust.
You may be able to move the 40/20 power output relationship by changing
the spacing on the turns of L1 and L2. Try spreading the turns as well
as squeezing them. The most important factor when spreading or
squeezing the turns is the spacing between the wires at the ends of the
winding - spreading or squeezing the middle of the winding will not do much.
73,
Don W3FPR
On 6/17/2015 4:08 PM, M L Hooper wrote:
Don,
I installed the .1 microfarad capacitor at C30, but this didn’t change the
output.
After testing the C30 fix, I subsequently changed R30 to 33 ohms and R11 to 4.7
ohms. This did change things, but did not entirely resolve the problem.
At 13.8V input, my power meter shows 3.0 watts on both 20M and 40M.
When I lower the input voltage to 9.0 volts, the meter shows 1.4 watts on 40M
and 1.7 watts on 20M.
I guess this is within or nearly within specs, but it’s odd that there is more
output on 20M than on 40M.
Anything else I should try, or should I just use it like this for a while?
Thanks again,
Lee
KG5VU
On Jun 17, 2015, at 1:02 PM, Don Wilhelm <w3...@embarqmail.com> wrote:
Lee,
Yes, I would change that capacitor - there is a chance that it will increase
the output of the DDS and solve your power output problem.
There is a difference in some KX1s due to care during construction, component
tolerances, and a host of other factors.
Make certain you counted the toroid turns correctly - a straight wire through
the core is one turn, a full wrap around the core is 2 turns.
Count the turns that go through the core center.
If all else fails, you can install the KX1 power mod. If you have a good stock
of 1/4 watt resistors you may not need to order the kit. Change R11 to 4.7 ohms
and R30 to 33 ohms.
If those steps do not solve the power output situation, send me an off-list
email and we can make comparison measurements with my KX1.
The KX1 audio is not 'earbusting', but is normally adequate. Yes, you may want
to try headphones or earbuds with a higher SPL rating.
The "Quick Reference" is the only place in the KX1 manual where SLO, SHI, and
CAL are mentioned - I guess someone overlooked updating that portion of the manual since
the VERY early days of the KX1. Look at the listing of menu items on page 65 and you will
see DDS, BFO, and SIG to make those settings.
This has been true since firmware rev 1.01. 1.02 is the latest version.
73,
Don W3FPR
On 6/17/2015 10:58 AM, KG5VU wrote:
Hi,
I just finished building KX1 Serial Number 2879 which is the standard
20M/40M version. It's a great little rig but, I have a few issues, one
major and two minor:
A) On final testing I only had about 2.5W on 20M and 2.0W on 40M with power
supply at 13.8V. I tried to compress the winding on L2, as suggested, but
this only degraded the output slightly (2.2W on 20M and 1.8W on 40M).
Checked the components on the board against the schematic and everything
checked out OK. Any ideas on what else I should try? Any idea what RF
voltage levels I should see at each stage? (I have several decent
oscilloscopes for testing if need be.)
B) The receiver is sensitive (I can hear 0.1 microvolt RF signal on 20 & 40)
but the audio level (particularly for weak signals) is pretty low unless I
advance the AF Gain control to full clockwise. Is this normal? Do I just
need to experiment with different sets of ear-buds?
C) The firmware on my KX1 is version 1.02. The Menu on my unit is different
than the Manual. It does not include SLO, SHI or CAL. Instead there are
SIG, DDS and BFO. Are support documents for revised version available?
For background, I had no difficulty during assembly. The KX1 passed all
tests except the transmit power output.
I did make one mistake during assembly however. I mistakenly inserted a .1
microfarad capacitor at C30 instead of a .01 microfarad capacitor. Since
everything seemed to be working, so I have not corrected this issue. Think
this could be significant?
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