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Maco brute 75
- Thread starter 238
- Start date
Typical setting is with a SWR meter and coax jumper between the radio and the amplifier. The slug is set for a low SWR when the amplifier is keyed.
73
73
Got the Brute working, but still have one more problem. Have moved the inside tune to the front. With a dead key it has two peaks, as nomadradio says it should. But when i do the mod tune, with modulation, it goes up as you turn. But it turns all the way clockwise an hits the stop,witch is no mesh at all. So what do i do to fix that? Jim/238
Ahhh, "mod tune"?
As in the Load control? The one on the far right?
Are the plates fully meshed together or all the way apart at the end where it peaks?
Makes a difference as to what you do next.
73
As in the Load control? The one on the far right?
Are the plates fully meshed together or all the way apart at the end where it peaks?
Makes a difference as to what you do next.
73
Ah, if you were to set the Load control at the halfway point, and then turn the plate-tune knob that's been moved to the front, will that knob show a peak at all?
It sounds to me as if the amplifier is being peaked not at 27 MHz, but at the second-harmonic frequency 54 MHz.
I would first try setting the Load control at the halfway point, and then turning the plate tune control to see if it will show a peak.
At least that should get the output circuit closer to 27 MHz.
The usual means of "fine-tuning" to get a proper peak on the plate-tune control is to tweak the output coil connected between the tune cap and the load cap.
First step is to determine which way to tweak it, for more or for less inductance.
The position where the tune control shows a peak is the guide for this.
Might have a look to see if any disc capacitors have been wired in parallel with the Load control. Would affect where that knob shows a peak.
73
It sounds to me as if the amplifier is being peaked not at 27 MHz, but at the second-harmonic frequency 54 MHz.
I would first try setting the Load control at the halfway point, and then turning the plate tune control to see if it will show a peak.
At least that should get the output circuit closer to 27 MHz.
The usual means of "fine-tuning" to get a proper peak on the plate-tune control is to tweak the output coil connected between the tune cap and the load cap.
First step is to determine which way to tweak it, for more or for less inductance.
The position where the tune control shows a peak is the guide for this.
Might have a look to see if any disc capacitors have been wired in parallel with the Load control. Would affect where that knob shows a peak.
73
That's the deal. Closer makes the coil's magnetic field stronger, raises the inductance of the coil. When the stretch or squeeze solution won't bring the tune control into range, jumpering around one or more turns is the next step, or moving an existing jumper the other way to put more turns in the circuit.
The old timers called this process 'cut and try'.
73
