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KPA-100 pop from TX to RX

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DaveVK

KPA-100 pop from TX to RX

Hello everyone,

I have just reconnected my KPA100 and I have a pop from the speaker when the transmit switches to receive. I checked most settings including that my 8r hold is set as per the manual. I do notice that when I set 8r normal the pop disappears. What's the go here?

The other issue I've noticed (not happened before) is I detects a mechanical buzzing sound coming from the kpa100 when in SSB mode. I think this may be just a torroid rattling but if anyone has some suggestions I'm open to hearing them.

Regards,

Dave
K2 - SN3222

Don Wilhelm-4

Re: KPA-100 pop from TX to RX

Dave,

What is the T-R delay set to? If it is set to zero you may hear a 'pop'
when going to receive. Why it is not heard if 8R is set to normal is a
mystery to me.
If you have the KDSP2 installed and your KPA100 is not up to date (blue
toroid cores at RFC1 and L16) that pop would appear on *some* K2s. The
cure for that is to update with the KPA100UPKT. If your shield is not
up to date add the KPA100SHLDKT. The new shield has clips to contact
the sides of the K2, a narrow notch at the SO-239 jack, solder lugs to
connect the outside of the shield to the SO-239 and a speaker shield.

I have no answer for the buzzing. Is it in sync with the speech
patterns? If so, then your assumption about something loose is probably
correct, but I would expect something other than a toroid - perhaps the
KPA100 shield.

73,
W3FPR

On 7/3/2013 7:06 AM, DaveVK wrote:

> Hello everyone,
>
> I have just reconnected my KPA100 and I have a pop from the speaker when the
> transmit switches to receive. I checked most settings including that my 8r
> hold is set as per the manual. I do notice that when I set 8r normal the
> pop disappears. What's the go here?
>
> The other issue I've noticed (not happened before) is I detects a mechanical
> buzzing sound coming from the kpa100 when in SSB mode. I think this may be
> just a torroid rattling but if anyone has some suggestions I'm open to
> hearing them.
>
> Regards,
>
> Dave
> K2 - SN3222
>

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DaveVK

Re: KPA-100 pop from TX to RX

Thanks Don,

I will check the parts mentioned. I also have a feeling I may have some common mode currents interfering a bit. I've recently put up a sloper under the hex beam. I need to play with this. The pop on switch to RX is more prominent on the lower bands. When I set the power to less than 10 watts (KPA100 bypassed) the pop is not present. Also... to confuse matters more.... when I bypass the DSP and set the power above 10 watts the pop when K2 switches back to RX disappears.

I've had this problem before and cannot remember how I cured it. I think it was by setting 8r to normal.

Many thanks... I'll keep this thread up to date with my progress.

Cheers,

Dave
VK2NA

DaveVK

Re: KPA-100 pop from TX to RX

Don,

I have fixed the mechanical buzz from the SSB tx on the KPA-100. The fault was mine. Across the RF Aux input between the PCB and the heatsink there seems to be a blue resistor with the colours Brn-Blk-Blk-Org-Brn with one leg that was touching the heat sink. The legs are long and so I just pushed it away with a screwdriver. I don't know what that part is doing there, or why it is installed like a hack did the job but the memory of it is lost in history.

I cannot find the part listed in the KPA instruction manual or any of the upgrade kits. So maybe it doesn't belong there??!! But anyway, that problem is fixed and the next time I'm in a position to remove the heatsink I'll install that part properly.

I seem to have the upgrade kit installed and the blue cores are in the KPA-100.

Now the popping is unsolved. It seems to be connected to the DSP. The popping is most prominent on bands below 20m. When the DSP is bypassed the popping disappears. I am still hunting this one down.

Don Wilhelm-4

Re: KPA-100 pop from TX to RX

Dave,

If it does not have the popping sound when you select 8R=nor, then run
it that way.

With the updated KPA100, there is one resistor on the bottom of the
board - a 22k from the +12 volt rail to the drain of Q7.
What a 100k resistor would be doing on the bottom of the board, I have
no idea. Perhaps it is contributing to your popping condition.

The KDSP2 has mute transistors and apparently the unmute time for them
(in addition to the audio delay through the DSP) is causing that pop to
be heard.

73,
Don W3FPR

On 7/3/2013 11:09 PM, DaveVK wrote:

> Don,
>
> I have fixed the mechanical buzz from the SSB tx on the KPA-100. The fault
> was mine. Across the RF Aux input between the PCB and the heatsink there
> seems to be a blue resistor with the colours Brn-Blk-Blk-Org-Brn with one
> leg that was touching the heat sink. The legs are long and so I just pushed
> it away with a screwdriver. I don't know what that part is doing there, or
> why it is installed like a hack did the job but the memory of it is lost in
> history.
>
> I cannot find the part listed in the KPA instruction manual or any of the
> upgrade kits. So maybe it doesn't belong there??!! But anyway, that problem
> is fixed and the next time I'm in a position to remove the heatsink I'll
> install that part properly.
>
> I seem to have the upgrade kit installed and the blue cores are in the
> KPA-100.
>
> Now the popping is unsolved. It seems to be connected to the DSP. The
> popping is most prominent on bands below 20m. When the DSP is bypassed the
> popping disappears. I am still hunting this one down.
>
>

DaveVK

Re: KPA-100 pop from TX to RX

I don't know. All issues seemed to have disappeared. Happy again but empty handed as to the reasons. I will ham on and be happy.