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KAT100: Strange K2/100 Behavior During Tune

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Jonathan Taylor, K1RFD

KAT100: Strange K2/100 Behavior During Tune

I have a K2/100 with a KAT100. For the most part, all works well as
expected.

Intermittently, though, when I press the TUNE button, the KAT100 will
chatter briefly as if finding a match, and then it suddenly stops and the K2
acts as if its CPU has been re-set; the bargraph and the LCD go blank
briefly, then the ELECrAFt sign-on message appears briefly and finally the
frequency is re-displayed. During this time, however, the power supply
indications are normal and the LCD backlight remains on.

This problem seems to be frequency-dependent and seems to happen more often
at high power, which leads me to think it is an RF feedback issue.

However, I've noticed that turning the power down to bottom end of the
high-power range (approx 12 W) usually doesn't help, yet turning it slightly
lower than that, to get into the low-power range (approx 10 W), does.

Any advice on how to solve it?

Thanks

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Don Wilhelm-3

RE: KAT100: Strange K2/100 Behavior During Tune

If it is RF feedback, the proper way to deal with it is at the source - in
your antenna system.

An easy way to check it is to cut a quarterwave wire for each band that is
troublesome - attach one end of the wires to the ground terminal on your
tuner and the other end just stretches out and attaches to nothing excpet an
insulator. There will be high RF Voltage on the open end of the wires, so
keep them clear of human and pet contact and keep them far enough away from
objects to prevent arc-overs (treat the far ends sort-of-like the end af an
antenna).

If these wires correct the problem, then you do have work to do on the
antenna system. If they do not help, then you can look further for a K2/100
or KAT100 problem.

>From your description, I would think something is causing a very high
current draw (even for a very short time) - your power supply may be going
into foldback limiting and the K2 powers off momentarily. The other
possibility is that the resettable fuse in th ebase K2 is tripping and
causing the power off condition (yes - it is powering off since you see the
ELECrAFt on the display).

Is this by any chance happening most frequently on 40 meters?

73,
Don W3FPR

> -----Original Message-----
>
> I have a K2/100 with a KAT100. For the most part, all works well as
> expected.
>
> Intermittently, though, when I press the TUNE button, the KAT100 will
> chatter briefly as if finding a match, and then it suddenly stops
> and the K2
> acts as if its CPU has been re-set; the bargraph and the LCD go blank
> briefly, then the ELECrAFt sign-on message appears briefly and
> finally the
> frequency is re-displayed. During this time, however, the power supply
> indications are normal and the LCD backlight remains on.
>
> This problem seems to be frequency-dependent and seems to happen
> more often
> at high power, which leads me to think it is an RF feedback issue.
>
> However, I've noticed that turning the power down to bottom end of the
> high-power range (approx 12 W) usually doesn't help, yet turning
> it slightly
> lower than that, to get into the low-power range (approx 10 W), does.
>
> Any advice on how to solve it?
>
> Thanks
>

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Jonathan Taylor, K1RFD

Re: KAT100: Strange K2/100 Behavior During Tune

In this case the antenna is a simple coax-fed 40M dipole with a balun at the
feedpoint. Without the KAT100 in line the SWR is approx 1.2 to 1 at 7100
where the problem occurs.

A quick check shows that yes, the problem seems to occur only on 40m. I
also noticed that other accessories on the same power supply re-set
themselves when it happens, supporting the foldback limiting theory and the
work-around that Tom posted and Mark pointed out. However, it happens only
when the KAT100 is in line; I cannot reproduce it at any frequency or power
level when the KAT100 is disabled.

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Jonathan Taylor, K1RFD" <[hidden email]>; <[hidden email]>
Sent: Saturday, September 16, 2006 4:47 PM
Subject: RE: [Elecraft] KAT100: Strange K2/100 Behavior During Tune

> If it is RF feedback, the proper way to deal with it is at the source - in
> your antenna system.
>
> An easy way to check it is to cut a quarterwave wire for each band that is
> troublesome - attach one end of the wires to the ground terminal on your
> tuner and the other end just stretches out and attaches to nothing excpet
> an
> insulator. There will be high RF Voltage on the open end of the wires, so
> keep them clear of human and pet contact and keep them far enough away
> from
> objects to prevent arc-overs (treat the far ends sort-of-like the end af
> an
> antenna).
>
> If these wires correct the problem, then you do have work to do on the
> antenna system. If they do not help, then you can look further for a
> K2/100
> or KAT100 problem.
>
> From your description, I would think something is causing a very high
> current draw (even for a very short time) - your power supply may be going
> into foldback limiting and the K2 powers off momentarily. The other
> possibility is that the resettable fuse in th ebase K2 is tripping and
> causing the power off condition (yes - it is powering off since you see
> the
> ELECrAFt on the display).
>
> Is this by any chance happening most frequently on 40 meters?
>
> 73,
> Don W3FPR
>
>
>> -----Original Message-----
>>
>> I have a K2/100 with a KAT100. For the most part, all works well as
>> expected.
>>
>> Intermittently, though, when I press the TUNE button, the KAT100 will
>> chatter briefly as if finding a match, and then it suddenly stops
>> and the K2
>> acts as if its CPU has been re-set; the bargraph and the LCD go blank
>> briefly, then the ELECrAFt sign-on message appears briefly and
>> finally the
>> frequency is re-displayed. During this time, however, the power supply
>> indications are normal and the LCD backlight remains on.
>>
>> This problem seems to be frequency-dependent and seems to happen
>> more often
>> at high power, which leads me to think it is an RF feedback issue.
>>
>> However, I've noticed that turning the power down to bottom end of the
>> high-power range (approx 12 W) usually doesn't help, yet turning
>> it slightly
>> lower than that, to get into the low-power range (approx 10 W), does.
>>
>> Any advice on how to solve it?
>>
>> Thanks
>>
>
>
>

Rajiv Dewan, N2RD

Re: KAT100: Strange K2/100 Behavior During Tune

Here is another simple explanation. Perhaps it is voltage drop on
your power supply. You probably have the best match and most power
output on the 40m band, Is your power supply up to it? A simple way
to test this is to turn the power out down by 30W or so. Not enough
db wise to make a difference if it is an rf interefence issue but
will considerably reduce the demand on your power supply.

Raj, N2RD

On Sep 16, 2006, at 5:20 PM, Jonathan Taylor, K1RFD wrote:

> In this case the antenna is a simple coax-fed 40M dipole with a
> balun at the feedpoint. Without the KAT100 in line the SWR is
> approx 1.2 to 1 at 7100 where the problem occurs.
>
> A quick check shows that yes, the problem seems to occur only on
> 40m. I also noticed that other accessories on the same power
> supply re-set themselves when it happens, supporting the foldback
> limiting theory and the work-around that Tom posted and Mark
> pointed out. However, it happens only when the KAT100 is in line;
> I cannot reproduce it at any frequency or power level when the
> KAT100 is disabled.
>
>
> ----- Original Message ----- From: "Don Wilhelm" <[hidden email]>
> To: "Jonathan Taylor, K1RFD" <[hidden email]>;
> <[hidden email]>
> Sent: Saturday, September 16, 2006 4:47 PM
> Subject: RE: [Elecraft] KAT100: Strange K2/100 Behavior During Tune
>
>
>> If it is RF feedback, the proper way to deal with it is at the
>> source - in
>> your antenna system.
>>
>> An easy way to check it is to cut a quarterwave wire for each band
>> that is
>> troublesome - attach one end of the wires to the ground terminal
>> on your
>> tuner and the other end just stretches out and attaches to nothing
>> excpet an
>> insulator. There will be high RF Voltage on the open end of the
>> wires, so
>> keep them clear of human and pet contact and keep them far enough
>> away from
>> objects to prevent arc-overs (treat the far ends sort-of-like the
>> end af an
>> antenna).
>>
>> If these wires correct the problem, then you do have work to do on
>> the
>> antenna system. If they do not help, then you can look further
>> for a K2/100
>> or KAT100 problem.
>>
>> From your description, I would think something is causing a very high
>> current draw (even for a very short time) - your power supply may
>> be going
>> into foldback limiting and the K2 powers off momentarily. The other
>> possibility is that the resettable fuse in th ebase K2 is tripping
>> and
>> causing the power off condition (yes - it is powering off since
>> you see the
>> ELECrAFt on the display).
>>
>> Is this by any chance happening most frequently on 40 meters?
>>
>> 73,
>> Don W3FPR
>>
>>
>>> -----Original Message-----
>>>
>>> I have a K2/100 with a KAT100. For the most part, all works well as
>>> expected.
>>>
>>> Intermittently, though, when I press the TUNE button, the KAT100
>>> will
>>> chatter briefly as if finding a match, and then it suddenly stops
>>> and the K2
>>> acts as if its CPU has been re-set; the bargraph and the LCD go
>>> blank
>>> briefly, then the ELECrAFt sign-on message appears briefly and
>>> finally the
>>> frequency is re-displayed. During this time, however, the power
>>> supply
>>> indications are normal and the LCD backlight remains on.
>>>
>>> This problem seems to be frequency-dependent and seems to happen
>>> more often
>>> at high power, which leads me to think it is an RF feedback issue.
>>>
>>> However, I've noticed that turning the power down to bottom end
>>> of the
>>> high-power range (approx 12 W) usually doesn't help, yet turning
>>> it slightly
>>> lower than that, to get into the low-power range (approx 10 W),
>>> does.
>>>
>>> Any advice on how to solve it?
>>>
>>> Thanks
>>>
>>
>>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> 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

Don Wilhelm-3

RE: KAT100: Strange K2/100 Behavior During Tune

Raj,

Fine analysis, but consider that the K2/100 has more gain and better
efficiency on 40 meters than on most of the other bands, so the current
drain on 40 meters should be less for any given power output level, and
under normal operating conditions, the current drain should be at a minimum
on 40 meters.

I fear that the power supply shutdown may be a result of some kind of
parasitic that happens when the KPA100 is set for 40 meters. For some
unexplained reason, this shows up most commonly with the KAT100 attached.

There may be more later, I understand that the design engineers at Elecaft
are currently working on this, so patience is called for - it will likely be
corrected when all the "I"s are dotted and the "T"s are crossed (soon). In
the meantime, Tom Hammond has compiled information on this behavior - see
www.n0ss.net - look for the file on 'KPA100 40M Parasitic circumvention'.

73,
Don W3FPR

> -----Original Message-----
>
> Here is another simple explanation. Perhaps it is voltage drop on
> your power supply. You probably have the best match and most power
> output on the 40m band, Is your power supply up to it? A simple way
> to test this is to turn the power out down by 30W or so. Not enough
> db wise to make a difference if it is an rf interefence issue but
> will considerably reduce the demand on your power supply.
>
> Raj, N2RD
>
> On Sep 16, 2006, at 5:20 PM, Jonathan Taylor, K1RFD wrote:
>
> > In this case the antenna is a simple coax-fed 40M dipole with a
> > balun at the feedpoint. Without the KAT100 in line the SWR is
> > approx 1.2 to 1 at 7100 where the problem occurs.
> >
> > A quick check shows that yes, the problem seems to occur only on
> > 40m. I also noticed that other accessories on the same power
> > supply re-set themselves when it happens, supporting the foldback
> > limiting theory and the work-around that Tom posted and Mark
> > pointed out. However, it happens only when the KAT100 is in line;
> > I cannot reproduce it at any frequency or power level when the
> > KAT100 is disabled.
>