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[K2] Low sensitivity with variable-bandwidth filter

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Bill Coleman-2

[K2] Low sensitivity with variable-bandwidth filter

OK, I have a K2/100 w/ KAT100 that may have recently suffered from a static discharge event. I had to replace D16 & D17 in the KPA100, and I’m likely to do the same to the SWR bridge diodes in the KAT100 (since I can’t get the bridge to null properly).

The other thing I noticed is that the receiver sensitivity is substantially lower when using the CW filter. Using OP1, it seems to receive normally. I have three filters for CW 1.0, 0.4 and 0.16. When switching to 1.0 from OP1, signal levels drop by about 2-3 bars on the S-meter.

Anything in particular I should troubleshoot?

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Don Wilhelm

Re: [K2] Low sensitivity with variable-bandwidth filter

Bill,

First try removing the KSB2 - put bent wire jumpers between pins 1 and 3
of J9 and J10. Then see if you get a good response in CW.

Oh BTW, make sure the CW filters are centered at your sidetone pitch
first - use an audio spectrum analyzer and if you have one, a broadband
noise generator (if not, use band noise, but make sure there are on
signals on the band segement used).

If the CW filters work OK with the KSB2 removed, the troubleshooting
should start with the switching diodes on the KSB2 option.

73,
Don W3FPR

On 6/11/2019 2:53 PM, Bill Coleman wrote:
> OK, I have a K2/100 w/ KAT100 that may have recently suffered from a static discharge event. I had to replace D16 & D17 in the KPA100, and I’m likely to do the same to the SWR bridge diodes in the KAT100 (since I can’t get the bridge to null properly).
>
> The other thing I noticed is that the receiver sensitivity is substantially lower when using the CW filter. Using OP1, it seems to receive normally. I have three filters for CW 1.0, 0.4 and 0.16. When switching to 1.0 from OP1, signal levels drop by about 2-3 bars on the S-meter.
>
> Anything in particular I should troubleshoot?
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Bill Coleman-2

Re: [K2] Low sensitivity with variable-bandwidth filter

I own a set of Rework Eliminator modules, so that should be easy.

I just have to find them….

> On Jun 11, 2019, at 3:09 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> First try removing the KSB2 - put bent wire jumpers between pins 1 and 3 of J9 and J10. Then see if you get a good response in CW.
>
> Oh BTW, make sure the CW filters are centered at your sidetone pitch first - use an audio spectrum analyzer and if you have one, a broadband noise generator (if not, use band noise, but make sure there are on signals on the band segement used).
>
> If the CW filters work OK with the KSB2 removed, the troubleshooting should start with the switching diodes on the KSB2 option.
>
> 73,
> Don W3FPR
>
> On 6/11/2019 2:53 PM, Bill Coleman wrote:
>> OK, I have a K2/100 w/ KAT100 that may have recently suffered from a static discharge event. I had to replace D16 & D17 in the KPA100, and I’m likely to do the same to the SWR bridge diodes in the KAT100 (since I can’t get the bridge to null properly).
>> The other thing I noticed is that the receiver sensitivity is substantially lower when using the CW filter. Using OP1, it seems to receive normally. I have three filters for CW 1.0, 0.4 and 0.16. When switching to 1.0 from OP1, signal levels drop by about 2-3 bars on the S-meter.
>> Anything in particular I should troubleshoot?

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Don Wilhelm

Re: [K2] Low sensitivity with variable-bandwidth filter

Bill for receive, you only need the jumpers at J9 and J10 - it is quick
and easy to do with bent wires if you do not find the rework eliminators
is short order.
Those jumper wires will not complete the transmit path - only receive.

73,
Don W3FPR

On 6/11/2019 5:03 PM, Bill Coleman wrote:
> I own a set of Rework Eliminator modules, so that should be easy.
>
> I just have to find them….
>
>

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Bill Coleman-2

Re: [K2] Low sensitivity with variable-bandwidth filter

Fortunately, I found the Rework Eliminators easily.

Swapping out the KSB2 for the eliminators didn’t evidence a change in the CW variable bandwidth filter.

It’s weird, it appears to be working OK at the moment, but the CW 1.0 filter sounds weird. LSB and USB sound a little weird, too.

I wonder if the BFO calibration may be off. Perhaps I should do a CAL FIL and see where it leads me. Indeed, I probably should re-align the whole rig, it’s been several years since I’ve last done it. Ah, yes, September 2015 was the last time.

I’ve also had an issue with INFO 080 occasionally. When the rig is first turned on, I’ll get this. Earlier when this happened, I tore into the rig and removed every module. Still got INFO 080 on power-up. After the rig is on a while, however, it generally starts behaving.

> On Jun 11, 2019, at 5:37 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill for receive, you only need the jumpers at J9 and J10 - it is quick and easy to do with bent wires if you do not find the rework eliminators is short order.
> Those jumper wires will not complete the transmit path - only receive.
>
> 73,
> Don W3FPR
>
> On 6/11/2019 5:03 PM, Bill Coleman wrote:
>> I own a set of Rework Eliminator modules, so that should be easy.
>>
>> I just have to find them….
>>
>>
>

Bill Coleman-2

Re: [K2] Low sensitivity with variable-bandwidth filter

Yeah, this is looking more like a calibration problem.

I’m listening to W1AW code practice on 14.0475. As I cycle through the filters the S-units are roughly the same through OP1, 0.4 and 0.16. But on the 1.0 bandwidth, it is often 1-2 S-units lower. If I tune about 200 Hz lower, I get the same number of bars.

I’ll update you when I have a chance to do the calibration.

> On Jun 12, 2019, at 8:07 PM, Bill Coleman <[hidden email]> wrote:
>
> Fortunately, I found the Rework Eliminators easily.
>
> Swapping out the KSB2 for the eliminators didn’t evidence a change in the CW variable bandwidth filter.
>
> It’s weird, it appears to be working OK at the moment, but the CW 1.0 filter sounds weird. LSB and USB sound a little weird, too.
>
> I wonder if the BFO calibration may be off. Perhaps I should do a CAL FIL and see where it leads me. Indeed, I probably should re-align the whole rig, it’s been several years since I’ve last done it. Ah, yes, September 2015 was the last time.
>
> I’ve also had an issue with INFO 080 occasionally. When the rig is first turned on, I’ll get this. Earlier when this happened, I tore into the rig and removed every module. Still got INFO 080 on power-up. After the rig is on a while, however, it generally starts behaving.
>
>
>> On Jun 11, 2019, at 5:37 PM, Don Wilhelm <[hidden email]> wrote:
>>
>> Bill for receive, you only need the jumpers at J9 and J10 - it is quick and easy to do with bent wires if you do not find the rework eliminators is short order.
>> Those jumper wires will not complete the transmit path - only receive.
>>
>> 73,
>> Don W3FPR
>>
>> On 6/11/2019 5:03 PM, Bill Coleman wrote:
>>> I own a set of Rework Eliminator modules, so that should be easy.
>>>
>>> I just have to find them….
>>>
>>>
>>
>
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>

Don Wilhelm

Re: [K2] Low sensitivity with variable-bandwidth filter

Bill,

Yes, do the CAL FIL calibration first. If that does not cure anything,
then proceed with the rest of the alignment, but I doubt if that will
help much - the K2 alignment is usually quite stable over time.
The bandpass filter and other alignments are not going to change the
relationship between the SSB filter and the CW filter - only CAL FIL
will do that.

If you still have a problem after the full CAL FIL, you will usually
find a problem in the CW filter bank - like a bad crystal (but that does
not happen often). Reflowing the soldering on the IF crystals on the RF
Board may help.

73,
Don W3FPR

On 6/12/2019 8:23 PM, Bill Coleman wrote:
> Yeah, this is looking more like a calibration problem.
>
> I’m listening to W1AW code practice on 14.0475. As I cycle through the filters the S-units are roughly the same through OP1, 0.4 and 0.16. But on the 1.0 bandwidth, it is often 1-2 S-units lower. If I tune about 200 Hz lower, I get the same number of bars.
>
> I’ll update you when I have a chance to do the calibration.
>
>

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Bill Coleman-2

Re: [K2] Low sensitivity with variable-bandwidth filter

Well, I think I finally got it sorted.

I replaced D1 and D2 on my KAT100. One of the diodes was good, the other was likely bad since I couldn’t get the SWR bridge to null, but I destroyed it while extracting it from the board.

New diodes are in machined socket pins, which will make them easy to replace (or test) later, if need be. SWR bridge calibration went swimmingly.

As for the filter problem, I did a CAL FIL and checked OP1 on LSB and USB, All four filters on CW and RTTY.

Other than a few minor tweaks, the only thing I ran into was FL1 on CW (which is a 1.0 filter) was about 200 Hz low. FL3 (0.16) was about 30 Hz high.

After the CAL FIL, the radio sounds normal again. I don’t believe I’ll do a full alignment.

Thanks for your assistance.

> On Jun 12, 2019, at 10:09 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> Yes, do the CAL FIL calibration first. If that does not cure anything, then proceed with the rest of the alignment, but I doubt if that will help much - the K2 alignment is usually quite stable over time.
> The bandpass filter and other alignments are not going to change the relationship between the SSB filter and the CW filter - only CAL FIL will do that.
>
> If you still have a problem after the full CAL FIL, you will usually find a problem in the CW filter bank - like a bad crystal (but that does not happen often). Reflowing the soldering on the IF crystals on the RF Board may help.
>
> 73,
> Don W3FPR
>
> On 6/12/2019 8:23 PM, Bill Coleman wrote:
>> Yeah, this is looking more like a calibration problem.
>>
>> I’m listening to W1AW code practice on 14.0475. As I cycle through the filters the S-units are roughly the same through OP1, 0.4 and 0.16. But on the 1.0 bandwidth, it is often 1-2 S-units lower. If I tune about 200 Hz lower, I get the same number of bars.
>>
>> I’ll update you when I have a chance to do the calibration.
>>
>>
>

Don Wilhelm

Re: [K2] Low sensitivity with variable-bandwidth filter

Bill,

Congratulations, it sounds like you have achieved success.

Once set the K2 alignment usually remains stable for a long time. If it
ain't broke, don't fix it!

Don W3FPR

On 6/17/2019 10:36 AM, Bill Coleman wrote:

> Well, I think I finally got it sorted.
>
> I replaced D1 and D2 on my KAT100. One of the diodes was good, the other was likely bad since I couldn’t get the SWR bridge to null, but I destroyed it while extracting it from the board.
>
> New diodes are in machined socket pins, which will make them easy to replace (or test) later, if need be. SWR bridge calibration went swimmingly.
>
> As for the filter problem, I did a CAL FIL and checked OP1 on LSB and USB, All four filters on CW and RTTY.
>
> Other than a few minor tweaks, the only thing I ran into was FL1 on CW (which is a 1.0 filter) was about 200 Hz low. FL3 (0.16) was about 30 Hz high.
>
> After the CAL FIL, the radio sounds normal again. I don’t believe I’ll do a full alignment.
>
> Thanks for your assistance.
>
>> On Jun 12, 2019, at 10:09 PM, Don Wilhelm <[hidden email]> wrote:
>>
>> Bill,
>>
>> Yes, do the CAL FIL calibration first. If that does not cure anything, then proceed with the rest of the alignment, but I doubt if that will help much - the K2 alignment is usually quite stable over time.
>> The bandpass filter and other alignments are not going to change the relationship between the SSB filter and the CW filter - only CAL FIL will do that.
>>
>> If you still have a problem after the full CAL FIL, you will usually find a problem in the CW filter bank - like a bad crystal (but that does not happen often). Reflowing the soldering on the IF crystals on the RF Board may help.
>>
>> 73,
>> Don W3FPR
>>
>> On 6/12/2019 8:23 PM, Bill Coleman wrote:
>>> Yeah, this is looking more like a calibration problem.
>>>
>>> I’m listening to W1AW code practice on 14.0475. As I cycle through the filters the S-units are roughly the same through OP1, 0.4 and 0.16. But on the 1.0 bandwidth, it is often 1-2 S-units lower. If I tune about 200 Hz lower, I get the same number of bars.
>>>
>>> I’ll update you when I have a chance to do the calibration.
>>>
>>>
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
>

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