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K1 build alignment.

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Dom M1KTA

K1 build alignment.

Ok this has me a bit stumped...

First I could get 40m working on RX and TX, but 20m was deaf as a post and no TX, now it's the other way around. I needed to tweak L7 and L8.

40m is band 1 and 20m is band 2.

Anyone else had this got any ideas? Yes been through 62 and the relays do switch.
None of L1, L2 L5 and L6 seem to be open circuit.
C's all still C and not shorted (lifted leads, tested and resoldered).
I reset the 40m L completely withdrwaing the cores and then going through testing with the screwed in with various turns but the signal generator signals are not detected now. But are on another radio.
I have checked continuity and for solder bridges etc... and the filter board default without power is band 1.

Short of sticking the filter board on a VNA as J7 pin 1-8 should be the BPF, J6 pin 1-7 should be the pre-mix BPF and J8 ping 1 and 8 should be the LPF (No ATU so J2 bridged). Interested in ideas.

BTW FT817 will easily pick out a 1uV signal but the K1 cannot seem to manage anything until about 2.5uV but the spec sheet says 0.15uV which seems something is wrong is this usual?
How am I measuring the signal: callibrated 50uV signals from xtal oscillator, step attenuator and an oscilloscope.

72

Dom
M1KTA

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Don Wilhelm-4

Re: K1 build alignment.

Dom,

Yes, that K1 would appear to be deaf - most can hear a -130 dBm signal
well above the receiver noise floor.
To troubleshoot it, use your oscilloscope (with a 10X probe). First
check the crystal oscillator output on each band You can check that at
the 2 band board P1 pin 4. You should have at least 200 mV peak to peak
on each band.
If that test is successful, put the oscilloscope probe on P1 pin 6 and
tune the PreMix Bandpass Filters for maximum deflection on the 'scope.
Note, that will give you an "almost correct" setting of the inductors,
but you will want to peak them during transmit while monitoring the RF
output with your scope across the dummy load.

OK, the PreMixer bandpass is adjusted close enough to go on to the next
step - this time you will have to be in TUNE.
Monitor the 2 band board P2 pin 8 with your scope and adjust the
inductors for maximum RF. If the power output goes above 3 or 4 watts,
tap the WPM- Button to bring it down - you cannot observe the peak if
the power level is anywhere near the maximum because the transmit stages
hit their maximum gain, so keep the power output low.

If you find output at the antenna in the step above, connect the
oscilloscope across the dummy load and re-peak the inductors - you will
then be done tuning the bandpass filters - if there is subsequent
trouble, have faith in the tuning of those filters and look for another
problem.

I believe what you will find in the end is a bad solder connection
somewhere. If it worked at one time and then stopped working, that is
usually an indication of an intermittent solder joint.

73,
Don W3FPR

Dominic Baines wrote:

> Ok this has me a bit stumped...
>
> First I could get 40m working on RX and TX, but 20m was deaf as a post and no TX, now it's the other way around. I needed to tweak L7 and L8.
>
> 40m is band 1 and 20m is band 2.
>
> Anyone else had this got any ideas? Yes been through 62 and the relays do switch.
> None of L1, L2 L5 and L6 seem to be open circuit.
> C's all still C and not shorted (lifted leads, tested and resoldered).
> I reset the 40m L completely withdrwaing the cores and then going through testing with the screwed in with various turns but the signal generator signals are not detected now. But are on another radio.
> I have checked continuity and for solder bridges etc... and the filter board default without power is band 1.
>
> Short of sticking the filter board on a VNA as J7 pin 1-8 should be the BPF, J6 pin 1-7 should be the pre-mix BPF and J8 ping 1 and 8 should be the LPF (No ATU so J2 bridged). Interested in ideas.
>
> BTW FT817 will easily pick out a 1uV signal but the K1 cannot seem to manage anything until about 2.5uV but the spec sheet says 0.15uV which seems something is wrong is this usual?
> How am I measuring the signal: callibrated 50uV signals from xtal oscillator, step attenuator and an oscilloscope.
>
> 72
>
> Dom
> M1KTA
>
>

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Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Dom M1KTA

Re: K1 build alignment.

Thanks Don.

Will run through the suggestions.

I'll take a peek at the filters through a VNA too.
Is there an 'ideal' freq vs transmission plot anywhere?

Two other suggestions off list for the 'deafness' points at the RX RP resistor banks so I expect a dry joint might explain some of this.

72

Dom
M1KTA

----- Original Message ----
> From: Don Wilhelm <[hidden email]>
> To: Dominic Baines <[hidden email]>
> Cc: [hidden email]
> Sent: Thu, 27 May, 2010 21:14:02
> Subject: Re: [Elecraft] K1 build alignment.
>
> Dom,

Yes, that K1 would appear to be deaf - most can hear a -130 dBm
> signal well above the receiver noise floor.
To troubleshoot it, use your
> oscilloscope (with a 10X probe). First check the crystal oscillator output
> on each band You can check that at the 2 band board P1 pin 4. You
> should have at least 200 mV peak to peak on each band.
If that test is
> successful, put the oscilloscope probe on P1 pin 6 and tune the PreMix Bandpass
> Filters for maximum deflection on the 'scope. Note, that will give you an
> "almost correct" setting of the inductors, but you will want to peak them during
> transmit while monitoring the RF output with your scope across the dummy
> load.

OK, the PreMixer bandpass is adjusted close enough to go on to the
> next step - this time you will have to be in TUNE.
Monitor the 2 band board
> P2 pin 8 with your scope and adjust the inductors for maximum RF. If the
> power output goes above 3 or 4 watts, tap the WPM- Button to bring it down - you
> cannot observe the peak if the power level is anywhere near the maximum because
> the transmit stages hit their maximum gain, so keep the power output
> low.

If you find output at the antenna in the step above, connect the
> oscilloscope across the dummy load and re-peak the inductors - you will then be
> done tuning the bandpass filters - if there is subsequent trouble, have faith in
> the tuning of those filters and look for another problem.

I believe what
> you will find in the end is a bad solder connection somewhere. If it
> worked at one time and then stopped working, that is usually an indication of an
> intermittent solder joint.

73,
Don W3FPR

Dominic Baines

> wrote:
> Ok this has me a bit stumped...
>
> First I could
> get 40m working on RX and TX, but 20m was deaf as a post and no TX, now it's the
> other way around. I needed to tweak L7 and L8.
>
> 40m is band 1
> and 20m is band 2.
>
> Anyone else had this got any ideas?
> Yes been through 62 and the relays do switch.
> None of L1, L2 L5 and L6
> seem to be open circuit.
> C's all still C and not shorted (lifted leads,
> tested and resoldered).
> I reset the 40m L completely withdrwaing the
> cores and then going through testing with the screwed in with various turns but
> the signal generator signals are not detected now. But are on another
> radio.
> I have checked continuity and for solder bridges etc... and the
> filter board default without power is band 1.
>
> Short of sticking
> the filter board on a VNA as J7 pin 1-8 should be the BPF, J6 pin 1-7 should be
> the pre-mix BPF and J8 ping 1 and 8 should be the LPF (No ATU so J2 bridged).
> Interested in ideas.
>
> BTW FT817 will easily pick out a 1uV
> signal but the K1 cannot seem to manage anything until about 2.5uV but the spec
> sheet says 0.15uV which seems something is wrong is this usual?
> How am I
> measuring the signal: callibrated 50uV signals from xtal oscillator, step
> attenuator and an oscilloscope.
>
> 72
>
> Dom
>
> M1KTA
>
>

Dom M1KTA

Re: K1 build alignment.

In reply to this post by Don Wilhelm-4

Don,

Thanks.

Premix LO signals look fine for both 40m and 20m bit more than 200mV P-t-P
http://m1kta-qrp.blogspot.com/2010/05/k1-build_28.html has the oscilloscope plots and a spectrum plot from both too.

Using the oscilloscope to adjust the filters nice suggestion thanks.
Video, bit shaky on that blog post I mmight improve that but need a 3rd and 4th hand!

Onto the tune.

K1 RX still deaf anything less than 2.5uV not heard.

72

Dom
M1KTA

----- Original Message ----
> From: Don Wilhelm <[hidden email]>
> To: Dominic Baines <[hidden email]>
> Cc: [hidden email]
> Sent: Thu, 27 May, 2010 21:14:02
> Subject: Re: [Elecraft] K1 build alignment.
>
> Dom,

Yes, that K1 would appear to be deaf - most can hear a -130 dBm
> signal well above the receiver noise floor.
To troubleshoot it, use your
> oscilloscope (with a 10X probe). First check the crystal oscillator output
> on each band You can check that at the 2 band board P1 pin 4. You
> should have at least 200 mV peak to peak on each band.
If that test is
> successful, put the oscilloscope probe on P1 pin 6 and tune the PreMix Bandpass
> Filters for maximum deflection on the 'scope. Note, that will give you an
> "almost correct" setting of the inductors, but you will want to peak them during
> transmit while monitoring the RF output with your scope across the dummy
> load.

OK, the PreMixer bandpass is adjusted close enough to go on to the
> next step - this time you will have to be in TUNE.
Monitor the 2 band board
> P2 pin 8 with your scope and adjust the inductors for maximum RF. If the
> power output goes above 3 or 4 watts, tap the WPM- Button to bring it down - you
> cannot observe the peak if the power level is anywhere near the maximum because
> the transmit stages hit their maximum gain, so keep the power output
> low.

If you find output at the antenna in the step above, connect the
> oscilloscope across the dummy load and re-peak the inductors - you will then be
> done tuning the bandpass filters - if there is subsequent trouble, have faith in
> the tuning of those filters and look for another problem.

I believe what
> you will find in the end is a bad solder connection somewhere. If it
> worked at one time and then stopped working, that is usually an indication of an
> intermittent solder joint.

73,
Don W3FPR

Dominic Baines