That is exactly why it's important that the ATU of a solid state
amplifier maintain a low SWR.
Scott K9MA
On 11/29/2018 21:59, Victor Rosenthal 4X6GP wrote:
There IS a reason to be fanatical about a 1:1 SWR, although it doesn't
apply to an amp like the KPA1500.
If you are running a tube
There IS a reason to be fanatical about a 1:1 SWR, although it doesn't
apply to an amp like the KPA1500.
If you are running a tube amplifier that requires tuning, and the tuner
always provides the identical load, you can tune the amplifier once,
record the dial settings, and quickly reset the
Now that you mention it, that sounds right. I SHOULD have the key line
set up properly; I did at one time. Guess it's time to accept the pain
of pushing the radio desk out from the wall and seeing what's really
there. I might have accidentally screwed things up the last time I did
some station
"However, since the amp is being keyed while the tuner is changing presets, the
amp immediately faults and goes off line. This is very annoying, and probably
not so good for either the amp or the tuner."
That should not happen. The KAT500 should open the amp keying line before
changing the
Need to have recent firmware in both the KAT500 and KPA500 also. The KPA500 for
this was updated shortly after the KAT500 was created. In any case, the latest
firmware for both devices is strongly recommended.
73!
Jack, W6FB
> On Nov 29, 2018, at 6:48 PM, Don Wilhelm wrote:
>
> Randy,
>
>
Randy,
That indicates that you do not have your KAT500 and amplifier properly
connected.
The KEYOUT line from the transceiver should go first to the KAT500, and
then from the KAT500 to the amplifier.
When the KAT500 needs to tune, the amplifier will not be keyed and
tuning will take place
Lots of important stuff here, most of which I agree with. See comments
interspersed.
On 11/29/2018 5:22 PM, Bob McGraw K4TAX wrote:
I think in general we fret too much over values of SWR which are 1.5:1
or less at the station end i.e. between the tuner and the amp or
transceiver.
I paid a
It's true that the effect a given SWR has on an amplifier output depends
on the actual impedance presented. That 2:1 SWR can be anywhere from 25
to 100 Ohms, plus various reactive impedances in between. On
simple-minded way to look at it is to imagine an amplifier as a
low-impedance source.
In checking my K3S into an antenna that presents a 2:1 SWR as indicated
on my external Power/SWR meter, my KPA500 in STBY, and my KAT500 in
bypass mode, it does deliver 100 watts. Although, I prefer not to
operate in that configuration if not necessary.
I think in general we fret too much
I've had difficulties with my KAT500 / KPA500 combo (only) on 160
meters, apparently due to the tuner relying on RF sensing. I've
carefully "trained" my KAT500 all across the 160 meter band. Since the
manual states that the tuning bins are 10 kHz wide below 3 MHz, I do a
tune at 1805, 1815 ...
>
> I wish Elecraft would give serial data frequency priority over RF detected
> frequency until a difference threshold is exceed.
+1
73 de AI6KG
On Thu, Nov 29, 2018 at 2:43 PM ANDY DURBIN wrote:
>
> "In addition the tuner may not always be in the segment you think it is.
> This is due to
On 11/29/2018 16:57, Don Wilhelm wrote:
Since the typical driving transceiver can tolerate an SWR of at least
2:1 without power foldback or damage, setting that 1.3:1 limit is
reasonable -
That certainly is not the case with the KPA1500. An SWR of 1.4:1 can
cause it to fault well below 1500
"There is also a limit to how far the firmware will go to reducing SWR. In the
interest of minimizing tuning time (and relay wear and tear). If the match is
less than 1.3:1 or so, tuning will be declared adequate and will be stopped.
Since the typical driving transceiver can tolerate an
Andy and all,
The KAT500 and KAT1500 tuner band segments are divided into frequency
band segments - 25kHz wide on the lower bands and 50kHz wide on the
upper bands if I recall correctly, so an 8kHz shift will not be
significant unless the frequency shift moves the tuning into the
adjacent
"In addition the tuner may not always be in the segment you think it is. This
is due to the 8KHz resolution of the internal counter, that wins over you
sending it a more accurate frequency, and also the hysteresis algorithm that
can require a 2 segment frequency change before the tuner
In the link I provided earlier (including some references) I point out some of
the pitfalls and error sources so that is a possibility. But I still contend
that, with a lossless line anyway, the impedance of a load, resistive or
otherwise, is the same at either end of a 1/2 wavelength line, or
I think the point Mike is trying to make is that many SWR meters don't
actually measure SWR all that accurately as impedance changes. While the
length of transmission line doesn't affect SWR (other than the effect of
loss), the impedance at a given SWR does change with line length, and
that
I fail to see what that will prove. The only length that will do anything
exciting is the 1/4 wavelength line and even that doesn't affect the SWR. The
other two will just repeat (less loss) on the input side, what terminates the
load side.
Wes N7WS
On 11/27/2018 3:51 PM, Michael Walker
> On Nov 27, 2018, at 12:02 PM, Bill Johnson wrote:
>
> If one thinks about it, no auto tuner can be expected to get an exact match
> unless it is adjusted manually (that would be a PITA).
When I think about it, it seems pretty obvious that an autotuner could get at
least as good a match as
Interesting! I just ran some tests on my station into Bird load; tuner bypassed:
At 50.1 mHz:
LP-700 1.06
K3 1.5
KPA1500 1.0
At 9.56 mHz (geometric mean freq)
LP-700 1.05
K3 1.1
KPA1500 1.0
At 1.825 mHz:
LP-700 1.05
K3 1.1
KPA1500 1.0
My KPA1500 looks good but K3 is off on 6m.
73, Roger
The ATU in the K3, which should work exactly like the one in the
KPA1500, seems to consistently find a very good match, at least on the
lower bands where the L/C resolution is very good. Why the KPA1500 often
fails to find such a good match is a mystery to me. The only difference
should be the
Mike,
I don't know if that really explains SWR, but with the different loads,
I "get" what you are alluding to.
One comment is that those feedline lengths should be electrical lengths
- they will be shorter than the physical length by the amount
contributed by the feedline velocity factor.
If you truly want to understand SWR, I recommend you pick a frequency and
make up a 1/4, 1/2 and 1 wavelength sections of 50ohm coax.
Then measure the SWR at those points into various different resistive
loads, like 10, 25, 50, 75, 100, 150 and 200 ohms.
I think you will find the results very
A few months ago I wrote about the potential errors in measuring SWR with
amateur grade equipment. See my comments in this thread:
http://elecraft.365791.n2.nabble.com/K3-SWR-Numerical-Indication-td7643839.html
I imagine "the best they can do" is accurate.
Wes N7WS
ps. I also said that if I
If one thinks about it, no auto tuner can be expected to get an exact match
unless it is adjusted manually (that would be a PITA). And if done manually,
that doesn't mean that the match is perfect. It just appears that way.
Consider what goes on with feedline, connections and the antenna
There is definitely room for improvements in the
tuning algorithm. Because of this I have tuned
all my segments manually. I find if the SWR is
not adjusted to be close to 1:1 in all segments
of a band then the drive requirements vary across
that band, which would be very annoying.
In
I've experienced some of these same issues with my KPA-1500. In addition,
sometimes the amp will switch to stand-by for no apparent reason, on 6 meters
the AT won't tune a 1.7 to 1 SWR under 1.5 to 1, and one of the exhaust fans
got a good deal noisier after about 25 hours of operation. My
27 matches
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