help!

[Merlarts]

Yes help,
 
If it ain't one thing, it's another.  Having just fixed the AGC  problem in
my K2 (2631), enjoying the beautiful radio, weirdness has again  struck.  
 
I get high SWR on 40 meters after I cut the output down, to raise it again  
for full output.  When I back the power off to minimum, there's the high  
reflected power indication, about 9 to one.  When I run the power back up,  the SWR
again behaves.  Souns like antenna glitches, no?
 
The antenna is a big loop (240 feet) open at the top, fed with 450 ohm open  
wire line.  I use an SGC 230, and the combination with my K2-100 has been  
perfect.  When I back off the power, only on forty meters, the SWR goes  crazy.  
Only on forty.  All other bands tune thru the tuner just  fine.  So, thinking
still it must be the antenna, I ran the K2 into a dummy  load.  Same Thing
Happens !!!!!!!!!
 
Is there a bad solder joint in the low pass filter on the K2?; that lets it  
operate at some power levels but shows high levels of spurious transmitted  
signal sometimes?
 
I don't get it.  Any ideas?
 
Merlin, W3ICT,  [hidden email]
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[Don Wilhelm-3]

Merlin,

Yes, I would suspect a faulty solder connection before anything else.  Since
it is confined to 40 meters and happens with a dummy load, I would look in
the 40 meter low pass filter area first - especially for poorly tinned
toroid leads.

73,
Don W3FPR

> -----Original Message-----
>
> If it ain't one thing, it's another.  Having just fixed the AGC
> problem in
> my K2 (2631), enjoying the beautiful radio, weirdness has again  struck.
>
> I get high SWR on 40 meters after I cut the output down, to raise
> it again
> for full output.  When I back the power off to minimum, there's the high
> reflected power indication, about 9 to one.  When I run the power
> back up,  the SWR
> again behaves.  Souns like antenna glitches, no?
>
> The antenna is a big loop (240 feet) open at the top, fed with
> 450 ohm open
> wire line.  I use an SGC 230, and the combination with my K2-100
> has been
> perfect.  When I back off the power, only on forty meters, the
> SWR goes  crazy.
> Only on forty.  All other bands tune thru the tuner just  fine.
> So, thinking
> still it must be the antenna, I ran the K2 into a dummy  load.
> Same Thing
> Happens !!!!!!!!!
>
> Is there a bad solder joint in the low pass filter on the K2?;
> that lets it
> operate at some power levels but shows high levels of spurious
> transmitted
> signal sometimes?
>
> I don't get it.  Any ideas?
>
> Merlin, W3ICT,  [hidden email]
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> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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>  http://mailman.qth.net/mailman/listinfo/elecraft
>
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> Elecraft web page: http://www.elecraft.com
>
>

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[Don Wilhelm-3]

OK, I will now take back the content of my last post.  Re-reading more
carefully, since an autotuner is involved, a certain minimum power is
reqired to begin tuning - and if the power is set too low, 'strange things
will happen'.
Set the power for 2 watts or greater - it should tune with no problem.
After tuning the antenna, you can drop the power back if you wish to run
QRPp.

OTOH, since you indicate that the same thing happens with a dummy load
(hopefully with no tuner involved), you should still look at the KPA100 low
pass filter - and possibly the LPF in the base K2.

73,
Don W3FPR

> -----Original Message-----
> Yes help,
>
> If it ain't one thing, it's another.  Having just fixed the AGC
> problem in
> my K2 (2631), enjoying the beautiful radio, weirdness has again  struck.
>
> I get high SWR on 40 meters after I cut the output down, to raise
> it again
> for full output.  When I back the power off to minimum, there's the high
> reflected power indication, about 9 to one.  When I run the power
> back up,  the SWR
> again behaves.  Souns like antenna glitches, no?
>
> The antenna is a big loop (240 feet) open at the top, fed with
> 450 ohm open
> wire line.  I use an SGC 230, and the combination with my K2-100
> has been
> perfect.  When I back off the power, only on forty meters, the
> SWR goes  crazy.
> Only on forty.  All other bands tune thru the tuner just  fine.
> So, thinking
> still it must be the antenna, I ran the K2 into a dummy  load.
> Same Thing
> Happens !!!!!!!!!
>
> Is there a bad solder joint in the low pass filter on the K2?;
> that lets it
> operate at some power levels but shows high levels of spurious
> transmitted
> signal sometimes?
>
> I don't get it.  Any ideas?
>

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