[Elecraft] K1 build alignment.

[Dominic Baines]

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 <w3fpr at embarqmail.com>
> To: Dominic Baines <dombaines at yahoo.com>
> Cc: elecraft at mailman.qth.net
> 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
> 
>