[Elecraft] KAT500 Performance Clarification

[hawley, charles j jr]

I think the MFJ 998 which I used prior to getting the KAT500 limited the selection of values for the L network based on the band and the assumption that 1500 watts was the possible power. I am able to tune much more of the 160M and 40M bands with the KAT500 than with the MFJ. Since I was using 100 to 400 watts and not the 1500 the MFJ was supposedly rated for, I found it's limits very restrictive to no good purpose.
Good for the KAT500 in the smart programming it has.

Sent from my iPad
Chuck, KE9UW 
(Jack for BMW motorcycles)

On Jan 23, 2013, at 12:06 PM, "Phil Hystad" <phystad at mac.com> wrote:

> Dick,
> 
> Thanks, this is exactly the kind of clarification I was looking for.  Now, if you
> or someone says this was described in the manual I will be ashamed and
> embarrassed.   I already knew about the higher power at lower bypass
> SWR.  But, I did not realize the lower power at higher bypass SWR.
> 
> phil
> 
> PEH's iPad
> 
> 
> On Jan 23, 2013, at 9:58 AM, Dick Dievendorff <dieven at comcast.net> wrote:
> 
>> Hi, Phil.
>> 
>> Although the KAT500, like most tuners, will attempt to find a match whenever
>> it can, it protects itself from the very high voltages and currents that can
>> appear on internal components when the match is poor. We rate the tuner for
>> 500 watts at 10:1 SWR.  When you use an antenna that shows 17:1 SWR (the
>> "untuned" or "bypass" VSWR), the ATU measures the forward power and computes
>> the power it can safely handle with the high mismatch.  It's less than 500
>> watts.  You should be able to operate safely at 250 watts or so with that
>> high a bypass VSWR.  If you exceed the ATU's safety values, it should
>> illuminate the red FAULT led, make a fault log entry, and put the ATU into
>> BYPASS at the next opportunity.  It should also interrupt the amplifier key
>> line.
>> 
>> Dick, K6KR
>> 
>> 
>> 
>> 
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Phil Hystad
>> Sent: Wednesday, January 23, 2013 8:48 AM
>> To: elecraft at mailman.qth.net List
>> Subject: [Elecraft] KAT500 Performance Clarification
>> 
>> Gang, I was surprised last night when I got a descent low SWR tuning my
>> 80-meter (ladder-line fed into 4:1 balun) dipole on 160 meters.  I have had
>> the KAT500 for a couple of months and I never bothered trying it on 160
>> meters because on all previous attempts with other manual tuners I have
>> failed to get a good match.
>> 
>> But, last night, just as a lark, I switched up to 160 meters and gave the
>> KAT500 a try.  Sure enough it found a match of 1.05:1 at 1900 KHz with the
>> Bypass VSWR reading about 17:1.  Given I have most of the transmission line
>> in lower-loss ladder line helps with the losses to the antenna with that
>> high bypass SWR.
>> 
>> This was at 100 watts out from the K3.  Now, I decided to give a try with
>> the KPA500 in-line at about 475 watts and the best I could get is about 4:1
>> tuned SWR.  Now, I am not quite sure I understand the dynamics of the KAT500
>> with higher power.  This is what I did.  I tuned at 20 watts to the 1.05:1
>> SWR (bypass was ~17:1).  At 100 watts, my LP-100A was still reading about
>> 1.1:1 SWR.  But, when I turned on the KPA500 (switched out of standby) the
>> reading was roughly 4:1 with a fault on the KPA500.  Question, how does the
>> higher power affect the match of the KAT500.  I understand how higher power
>> might stress the KAT500 with maybe arcing or something but I don't
>> understand why the match actually changed unless that higher power caused
>> some change in the KAT500 capacitor or inductor components.
>> 
>> 
>> 73, phil, K7PEH
>> 
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> 
> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html