low tune power with SSB module

[Chris-488]

Hello,

I posted a couple of days ago regarding a strange problem I had with low
power output when testing my KPA100. Well I soon discovered that the low
power was due to low drive from the K2.

Whilst investigating this I removed the SSB to access U10 etc., inserted
the links and the cap. Pressed Tune to investigate and my power was back
to normal. Re installed the SSB module and Power is down again.

The symtoms are that I can get about 2W on 40m rolling of to a 100mW, or
so, on 10m.

Mike, VP8NO, lent me his spare SSB module and that gives full power on
tune. His had firmware 1.07 mine is 1.08.

I started checking voltages around my module and discovered that you
have to press PTT to get the Tx readings that are listed in the voltage
table in the manual (it doesn't specifically tell you that so I thought
that Tune would do!). Whilst doing this I discovered that SSB is
delivering full power so it is only in tune mode that power is being
limited.

What exactly does tune do that interacts with the SSB module?

I read somewhere, in the archives for this list I think, that tune power
may be limited to 2W by some SSB firmware versions. Is that correct?

If there is a 2W limit on tune (20W I guess with KPA) what would be
causing this 2W to roll off to almost nothing at 10m?

Without the SSB module installed I can get good power on all bands. With
the SSB module installed and using the whistle test I can get good power
on all bands. So it's definitly only the tune mode that is affected.

Tune power override, doesn't make any difference.

I'm still using a manual ATU and I need a bit more juice to able to get
a good indication on my meter!

The good news from this is that there is nothing wrong with my KPA100 :-)

Cheers
Chris VP8BKF

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[Don Wilhelm-3]

Chris,

You may have a problem with CW as well as TUNE.  Check voltages at SSB board
Q3 during TUNE or keydown on CW.  You should have 7.5 to 8 volts on the
collector and near 2.4 volts on the base - the emitter should be about 0.2
to 0.3 volts lower than the base.
If there is no voltage on the collector, check D5 for proper orientation.
Also check capacitor C39 for good soldering and a proper path to P1 pin 7.
The path from P1 pin 12 through C42, Q1 and C39 is the route for the BFO
signal through the SSB board during CW (or TUNE) operation.

73,
Don W3FPR

> -----Original Message-----
>
> I posted a couple of days ago regarding a strange problem I had with low
> power output when testing my KPA100. Well I soon discovered that the low
> power was due to low drive from the K2.
>
> Whilst investigating this I removed the SSB to access U10 etc., inserted
> the links and the cap. Pressed Tune to investigate and my power was back
> to normal. Re installed the SSB module and Power is down again.
>
> The symtoms are that I can get about 2W on 40m rolling of to a 100mW, or
> so, on 10m.
>
> Mike, VP8NO, lent me his spare SSB module and that gives full power on
> tune. His had firmware 1.07 mine is 1.08.
>
> I started checking voltages around my module and discovered that you
> have to press PTT to get the Tx readings that are listed in the voltage
> table in the manual (it doesn't specifically tell you that so I thought
> that Tune would do!). Whilst doing this I discovered that SSB is
> delivering full power so it is only in tune mode that power is being
> limited.
>
> What exactly does tune do that interacts with the SSB module?
>
> I read somewhere, in the archives for this list I think, that tune power
> may be limited to 2W by some SSB firmware versions. Is that correct?
>
> If there is a 2W limit on tune (20W I guess with KPA) what would be
> causing this 2W to roll off to almost nothing at 10m?
>
> Without the SSB module installed I can get good power on all bands. With
> the SSB module installed and using the whistle test I can get good power
> on all bands. So it's definitly only the tune mode that is affected.
>
> Tune power override, doesn't make any difference.
>
> I'm still using a manual ATU and I need a bit more juice to able to get
> a good indication on my meter!
>
> The good news from this is that there is nothing wrong with my KPA100 :-)
>
> Cheers
> Chris VP8BKF
>

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