Minima Mixer

The mixer is now on the board. I start winding the two BN43–2402 5,5 turn. Then select 2 off the 10 pcs J310 fet, with the closest Ids current. Mounted all mixer components on  the pcb. First try to adjust the bias to the fet. I have seen youtube video saying there is no difference in output, but I could see 3 dB change in amplitude on IF signal at 20MHz and also around 5dB in change of Noise-Flore best on 3,5 MHz was 2,5V and best on 28 MHz was 3,5V so I set bias in middle 3,0 V.

The spectrum is, what coms in coms out.

This measurement give me the conversion loss. Input 3,75, 17,2 and 28,4 Mhz around -52 dBm, this result in around 7 dB conversen loss, i also check @ 144 MHz input around 12dB loss.

The Isolation on IF port and RF port.  Lo is +16 dBm

Isolation @ IF port23,75 around 44 dB 37,2 around 41 dB 48,4 MHz around 38 dB.

it is worse on RF port.

Isolation @ RF port 37,2 MHz around 17 dB, its better at lower and higher freqv. 27 dB. 

After that I check impedance on the port.

Lo Port

 IF Port

RF port 

Perhaps it possible to get better figures more close to 50 ohm, but life is not always perfect!

I am glad that its time for X-Tal filer Test……….

73 de Leif SM4HNG