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K2 IF adapter

This page is work in progress and will be updated frequently. 

I wanted the qrpproject.de K2 ZF adapter for my Elecraft K2, but unfortunately they stopped at the end of 2022. Bummer (I really liked there website). 

So there was nothing else to do then looked for other IF adapters or build my own (a simple FET buffer could do the trick). 

When I got my hands on the construction manual (thanks Google) it was clear that the ZF adapter was also a simple FET buffer. So I decided to build one based on there design.
Instead of using SMD parts, I went for the Through Hole components because it looked much better in the all-Through Hole K2.  

I used 2 SMA footprints so you can solder the a coax to the top or bottom of the PCB.

The cool thing from KiCad is that is also has a 3D viewer which gives you a nice 3D rendering showing a glimpse of the final product. 
To bad that I didn't see the L1 silkscreen on top of the footprint :-( (but in wasn't printed on the prototype PCB's).

I had to ordered other PCB's, so I also ordered a small prototype batch of the IF adapter. And then I had to wait.

Protype PCB's in the house. 

After 2 weeks the PCB's got delivered and I had all the parts I needed in stock.

Installation

The IF adapter can be inserted on the NoiseBlanker PCB socket, or when you have the NoiseBlanker PCB installed, a female header strip can be soldered on the header connector. 

The IF adapter installed on top of the NoiseBlanker PCB. 

I used a SMA angle adapter and added a of the self 30dB attenuator inline to prevent overdrive of the RTL-SDR stick.

My RTL-SDR stick has a 100MHz up-convector so there was no problem going down to the IF frequency of 4914 KHz, as the SDSR application I used Gqrx. 

By default Gqrx shows a inverted frequency scale (LSB = USB, High = low etc). Also we show the IF frequency instead of the real frequency. Maybe Gqrx can use a serial connection to correct that, but for now it's ok. 

With adjusting the LNB LO the center frequency is set 0 for 4914 KHz and with swapping I&Q the direction of the dial and mode is logical.

 

Installation continues

Instead of the of the shelf attenuator I used one of my 1206 SMD attenuator PCB's which I configured with a 20dB attenuator setup (with 30dB ATT I had to up the gain on the RTL-SDR). A simple SMA male to SMA female chassis cable allows to hook up the SDR.

The K2 IF buffer works and for a test I used my TinySA Ultra as a pan adapter. It's a kind of slow-tv and proves that a real SDR works much better. Maybe I have to design a compact SDR based PAN adapter (modern microcontrollers have much power and even DSP functions now a days). 

 

 

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