Calibrating my RF meter and some Input vs Output Amp results

A project log for 45W RF SSB CW AMP (EBAY) DIY Build = 55W Upgrade

This is a guide to build & improve this $14 DIY Ebay kit as the OEM docs (also incl. here) are borderline Chinglish.

mosaicmercmosaicmerc 08/28/2017 at 17:580 Comments

When testing the output of the Amp into the 50Ω load, I discovered my Coaxial Dynamics 100W, 2-30Mhz Slug for my Bird 43 was reading 30% hi.

This is how to dismantle a stock bird slug:

BUT..a Coaxial dynamics Slug leaves NO room to leverage the top metal disc off. I had to drill the edge of the knurled grip & label disc with a 2.5mm PCB bit and then use a small flat  'trimmer' screw driver to raise it after heating it with my hot air gun to 300C, the glue was quite soft/tacky by then.

Then removing a hex nut gave full access to the trimmer pot.

Now my 100W slug can be tuned to 100W or 50W just with the trimmer pot!

I set it to 50W as that is best for the power range I am working with right now.

So as an FYI using a 14Mhz signal @14.5Vcc. Wattage measure via the Bird 2-30Mhz 50W slug.

10:1 scope probe, scope to 100Mhz bandwidth.

3.75Vpp =  50W out as per the Bird 43.(138Vpp on the Oscope, 50 Ω load), 4.82A draw

3.22 Vpp = 40W out as per the Bird 43.(126Vpp on the Oscope, 50 Ω load), 4.43A draw

2.74Vpp = 30W out as per the Bird 43. (111Vpp on the Oscope, 50 Ω load) , 3.93A draw

2.23Vpp = 20W out (Bird 43)  (92Vpp on the Oscope, 50 Ω load) , 3.31A draw

1.42Vpp= 10W out (Bird 43) ( 68Vpp on the Oscope, 50 Ω load) , 2.52A draw

1.12Vpp=5W out (50.4Vpp on the Oscope, 50 Ω load) , 1.96A draw

Pls note the 3rd harmonic is about 20dBc down. Even harmonics are reduced  as this is a push pull amp.