Thursday 18 March 2010

Portable auto ATU

I've just ordered an LDG Z-11ProII auto tuner. I was wondering whether to get the Z-817 instead but you can fit an internal battery to the Z-11 so the Z-11 is better because it can handle more power.
My other tuners are an LDG AT-7000 which only works with my Icom IC-7000 and a Zetagi M27 CB matcher (it works above 20 MHz).
Below is a view inside the M27:

I've also got a Zetagi B150 CB amplifier, had it for many years but not used it for a while. It never worked well on SSB, the original circuit is actually running in Class C (there's a DC short between base and emitter of the MRF455 power transistor, through a ferrite bead inductor, in parallel with a 10 ohm resistor). Mine now has some bias current because the ferrite bead has been removed and the bottom of the switching relay coil has been connected to the base of the MRF455. This gives some bias current only when transmitting.
Circuit diagram for the B150
Why build an amp with an AM/SSB switch (changes the delay on tx/rx changeover) if it won't work on SSB? The B300 uses a totally different circuit, still using MRF455s but in a pair.

No comments: