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K2 K60XV the hard way.

This page was last updated : 29-Apr-23 18:05:16

The used Elecraft K2 I got my hands on didn't have to 60m band option so when I wanted to buy the kit from Elecraft I found out that it was discontinued. 

Not giving up on that, and looking for a solution, I posted a message in the Elecraft groups.io. After some pointers I kept looking and found this page : http://boringhamradiopart.blogspot.com/2020/11/k60xv-hard-way.html 

The reason Elecraft didn't sell the K60XV any more is that they can't get there hands on some parts but they still have some PCB's, micro controllers etc in stock. 

So I send Elecraft a e-mail with my shopping list :

• 1 x U1 IC, microcontroller, PIC16C621A E610018
• 1 x Z1 Ceramic resonator, 4 MHz, 0.2% tolerance E660001
• 1 x MISC PC board, K60XV E100193
• 2 x K1,K2 Relay, DPDT latching 2 E640001 (2 extra because I want to make a DIY K160RX module)

I thought that the rest of the parts wouldn't be a problem because I have lots of components in stock and a very well packed electronics store in town . . . . . what was i thinking ? 

Getting the parts.

Well my stock of components was more then adjudicate for the more common parts and most of the other parts I could get at my local electronics store. But the NP0 capacitor values they have to order from there supplier which was no problmem,  minimum amount was 25 pcs. 

One of bigger problems was finding the variable capacitors and varicap diodes. But the DutchRFShop has a lot of special RF parts and although they didn't have the specified Cap., trimmer, 8-50 pF, bottom adj. I ordered from all values 10 pieces and start with the 120pF trimmer. And when it's sensitive to trim, I replace it with a 30pF one and add a 18pF NP0 in parallel. 

I also added  bunch of NP0 caps and after 2 days a envelop was delivered with my requested parts. but except the MV2109 varicap diodes. I thought I ordered them, but ordered a few MV209 varicap diodes.

Note to my self : check, double check, put on your reading glasses and double check again. So I need to hunt for som MV2109's.

 

Let's get starting

While waiting for some non stock parts, I started the assembly of the PCB. 

Here the 120pF variable capacitors are installed, which later on will be replaced with 30pF versions. 

Almost done and I had to wait for the LM358 OpAmp. 

So I used a piece of teflon coax to make the RF bridge as described in the manual. 

And when the LM358 arrived, I could finish the installation by trimming the way to long male headers. 

Putting everything back in its place like the K2 IF adapter but I think I'm going to make a new cable so I can use the lower 2 XVTR mounting holes for the K60XV .

Installed to K60XV 

And I could put it aside because I have to wait for the MV2109 varicap diodes. 

 

 

MV2109 no go, using the BB910 

The MV2109 is harder to get then expected, so I looked at other varicap diodes by comparing the datasheets. After looking at the datasheet of the MV2109 and comparing tit with BB910 (which I do have in stock), I found out that the curve has the same shape on the only difference is a aprx 16 to 18pF less capacity for the BB910 for the same voltages.

So I took 2 BB910 varicap diodes, installed them, put on each a 18pF NP0 capacitor in parallel, hooked up my 40dB RF sampler with a dummy load, and connected the sampler output to my frequency counter. 
Frequency was spot on, so this mod works. 

Tuning the 60m BPF 

I used my NanoVNA to align the BPF as I did before and found out that the 120pF variable capacitors where to big, so I replaced them with 30pF variable capacitors. And without adding a additional capacitor it worked out.

The setup I used to tune the 60m BPF. I had to solder a header on pin 4 and 5 of J13 (not shown in the image above).

All done, reception on the 60m is good enough and also TX is as expected. 

Next step, adding connectors so I can use the transverter option also (still want a 28/144MHz transverter some day). 

 

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