[Elecraft] KAT500 Tuning issue

[Vic Rosenthal]

If the feed line happens to be near an even multiple of a half wavelength the impedance will be very high and there will be a voltage loop (HV point) at the tuner. As someone else noted, losses would also be very high, so using a 40m coax fed dipole on 20 is a poor idea.

Vic k2vco

On Dec 8, 2012, at 12:37 PM, "hawley, charles j jr" <c-hawley at illinois.edu> wrote:

> Now that I think about it, if you have a different feedline length depending on tuning from the output of the KAT or tuning from the output of the K3 with both in line, that may make enough difference in the required values to tune.
> 
> Chuck, KE9UW
> Lionel Trains, TCA, LCCA, LRRC
> aka Jack, BMW Motorcycles BMWMOA #224
> 
> ________________________________________
> From: elecraft-bounces at mailman.qth.net [elecraft-bounces at mailman.qth.net] on behalf of hawley, charles j jr [c-hawley at illinois.edu]
> Sent: Saturday, December 08, 2012 2:33 PM
> To: Jerry Weisskohl; Elecraft at mailman.qth.net
> Subject: Re: [Elecraft] KAT500 Tuning issue
> 
> One thing I ran into with an automatic "hi powered" tuner is that the firmware does not allow all the otherwise available values of the components on certain bands. This is done in the case of the MFJ tuner I am using (now until the KAT arrives) on 40 Meters so that the voltage and current limits are not exceeded when handling full rated power. I don't know if the KAT500 has this implemented or if in the case of the higher power capability, it just doesn't have quite the range of the 100 watt tuner in the K3.
> As was mentioned in a similar thread, you might experiment by changing your feedline a few feet plus or minus to find a more satisfactory matching situation on some bands.
> 
> Chuck, KE9UW
> Lionel Trains, TCA, LCCA, LRRC
> aka Jack, BMW Motorcycles BMWMOA #224
> 
> ________________________________________
> From: elecraft-bounces at mailman.qth.net [elecraft-bounces at mailman.qth.net] on behalf of Jerry Weisskohl [jweisskohl at gmail.com]
> Sent: Saturday, December 08, 2012 1:57 PM
> To: Elecraft at mailman.qth.net
> Subject: [Elecraft] KAT500 Tuning issue
> 
> I believe I have run into a problem with the KAT500 tuner and wanted to
> mention it to see if anyone else is experiencing the same issue. I just
> received the KAT500 tuner  and the KPA500 amp and got it up and running
> with my K3. The KPA500 works great but I am finding that the KAT500 is
> unable to tune my 40 meter wire dipole on 20 meters. The best it can do is
> 3.75 - 1 swr which trips the FAULT light on the KAT500. The internal tuner
> in the K3 has been able to tune this antenna on all bands without issue.
> Also the KAT500 is unable to tune 28400 below 2.5 - 1 while the internal
> tuner in the K3 has no problems tuning that frequency. I have two antennas,
> my other one is a 80 meter vertical so I switch to that for 20 meters but I
> don't understand why the KAT500 is unable to tune certain frequencies when
> the internal tuner on the K3 is able to do so.
> 
> I called Elecraft and spoke to David who had me take the KPA500 out of the
> picture by connecting the KAT500 directly to the K3. I had the same
> results. David then sent me the latest unofficial KAT500 firmware 1.18
> which I installed. It did not make any difference.
> David had me try tuning using the utility, again no difference and still
> unable to tune 20 meters below 2.75 - 1 on my 40 meter wire dipole.
> 
> In general I am finding that the internal tuner does a much better job
> tuning my antennas then the KAT500. I wonder if anyone else is experiencing
> the same problem.
> 
> As far as the settings on the K3 I am using the following:
> COnfig:PWR Set = Per Band
> COnfig:Tune PWR = 15
> 
> I guess I will hope that this can be addressed through a later firmware
> release. Meanwhile, the KAT500 is the weak link in my system. The KPA500 is
> fantastic, just need to resolve this tuner issue.
> 
> Jerry - AC4BT
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