From: Joseph Ruggieri [jruggieri3@***.com]
Sent: Tuesday, November 13, 2007 8:28 PM
To: Didier Juges; Mark Donaldson
Cc: microwave@lists.valinet.com
Subject: Re: [Mw] Fwd: Brick Oscillator Question, MUD Proceedings articles
Well I can't help with all PLO brands but I can with the Macom/Magnum Microwave oscillators.
They will work down to 12v with reduced output power.
As for most power oscillators the L band oscillator in these units will have an output power fairly proportional to supply voltage and current.
One of my tower mounted transverters has been using a Macom PLO operating on 12.0 volts for a year without loosing lock.
Even the alarm relay still works with 12v on the supply.
However you must readjust the phase voltage as you lower the supply.
The phase voltage on most of these bricks is centered at 40% of the supply voltage so at 20V it should be centered at 8.0v and at 12v centered at 4.8v etc.
This is because most bricks use only a voltage divider to develop the reference to the error amplifier reference input.
I only remember finding one brick which used a regulated reference.
Typical power out of the brick is reduced by between .6 and 1dBm for one volt on the supply.
This also is true when increasing the supply between 20 and 24v. This is because the cavity transistors are biased at a constant current so power is increased as the supply increases. From what I have seen all positive supply Macom bricks were designed to operate up to 24v.
In my transverter application I still had over 7dBm at 12v, enough for a low power mixer.
Macom bricks also have a variable bias current adjustment for the cavity transistor array.
This can be used to adjust the required output power if needed.
Another way to increase the power to the multiplier is to screw the SRD pick-up probe further into the cavity.
As you do so remember to also adjust the phase voltage since moving this probe also changes the cavity volume.
Also as someone mentioned it is best to peak the post SRD filter for your desired frequency.
This can be done using only a power meter.
To get the best performance you should also adjust the matching adjustment between the pick-up probe and the SRD.
Doing this requires a spectrum analyzer.
Hope this helps.
Joe KI4NPV