SV: Re[elecraft] K2/KPA100 problem

[Henrik Tuxen]

Hallo Bryan,
I have had a problem with my KPA-100 oscillating around 7 MHz, and I
sent of a question to support and go this answer within 6 hours:

For oscillation problems when a tuner or reactive antenna is installed,
the
KPA100 must have the latest engineering changes:

1) KPA100SHLDKT
2) KPA100MODKT
3) New KPA100 f/w version 1.1 (requires 1 and 2 above).
4) All paint must be removed where the 2D fasteners and shield grounding
clips contact.
5) All cables must be in good condition. Do not more than 5" of RG-174/U
between K2 and KPA100.
6) All screws must be tight. The KPA100 shield must be grounded well by
both
the 3 spring clips, and 2 solder lugs between the SO-239 antenna
connector
and corner shield screw.
7) The power supply must not be affected by RF.
8) See the attached KPA100 errata for changes in the KPA100 t-r switch.
Be
sure to check and do the last 2 steps. This clears up KPA100 kits that
do
not have sufficient t-r switch isolation at high power on the lower
freq.
bands.

My personal comments on the above list:
Ad 4) An absolute must and cannot be emphasized enough.
Ad 5) This cable can be shortened down to around 4" without any
problems, and you can still install the KPA-100 without removing the
sides.
Ad 6) An absolute must.

If you look at my home page www.qslnet.de/dk1htx you can see some
pictures taken during my work, and there you can also see how much paint
I have removed from the heatsink.

Based on input from Tom Hammond I mounted about 30 toroids on the
coaxcable leading to my antenna, and my oscillating (and RFI) problems
were gone.

Best regards
DK1HTX, Henrik Tuxen
Henrik.Wagner.Tuxen at gmx.net
 

-----Oprindelig meddelelse-----
Fra: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] På vegne af Bryan
Sendt: 11 February 2005 16:20
Til: Elecraft
Emne: Re[elecraft] K2/KPA100 problem

Hi All,

The K2 appears to work on all bands, albeit only 6 to 8watts out on
15/12/15m, which I presume is ok, but maginal.  When I connect up my
KPA100, output is 100w plus on the lower bands, but on 15/12/10 m it is
very low, and the system is self-oscilating around 100MHz and the
frequency is unstable.

I would think that there was a problem in the KPA's LPF for those bands,
but I can't find anything wrong.  I use Toroidguys inductors, and all
seems well as far as I can check.

Has anyone had a similar experience I wonder.  Does the low output from
the K2 cause this problem

Thanks

73 Bryan  G3AKF
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