Help tuning DRFS-150 RF Amplifier with DRFS06 V2.1 Driver

[nimrod86]

Hi everyone, new to the forum but seems a great resource!

I'm building the DRFS06 V2.1 Driver and DRFS-150 Amplifier kits from the Dutch RF Shop at the moment. I have the driver working happily on the bench at between 6-8W and an SWR around 1.0-1.5 depending on the height I can have my aerial with wind! (When using a 50 Ohm dummy load the SWR is 1.0)

I'm now starting to add in the 150W DRFS-150 amplifer, and my SWR is at around 2.0 at 40W power. If I bring it to 60W power then SWR hits 3.0. I know this is where tuning the oscillator coils comes into play, but would anyone have any tips on how to go about this as I'm quite new to all this! I have no idea how to tell if I want to be tightening or expanding the spacing between my coils. The parts list from Dutch RF Shop mentioned a particular coil to adjust for best input SWR on the amplifier, and then two coils to adjust max output power.

As far as I know, the SWR from the driver is fine, so do I need to adjust the coil for input SWR on the amplifier? Or am I just now concerned with the output power coils?

Any thoughts appreciated

Cillian

[manxbiker]

Hi building one myself - have you found any more info please Cillian

Mike GD6ICR

[rigmo]

Why you not see with nanoVNA smith chart? pass antenna analyser? . I had an experience similar to the one described, but I turned off the system in time. I didn't have adequate protection then. the non-PTFE plastic began to melt. Power 300w. check it out coax connection connectors insulation.. ..

[sinus trouble]

Hello Nimrod86

firstly i would recommend using a spectrum analyser and a Bench or lab PSU!

I have never used the items in question? However, I would align the DRFS06 to have a roughly flat (equal) response output across the band (88-108) on a fixed 50 ohm resistive dummy load!

You could add SWR meters between your amplifier and driver? But this can sometimes give false reactance in circuit!

I would connect the amplifier direct to the driver with SWR meter on the output and align whilst keeping an eye on the current consumption (Amps) and temperature of the amplifier device!

The bench PSU will allow you to keep control of any failures that may arise!

Good luck!