connection consideration of a 500W RF amplifier

[bjbdts]

Hi, everyone:
We recently got a 500W Power amplifier.My job is to set it up. From instructions we need a power supply that gives 30V, 80A, This PA has four 30V bias inputs, we are instructed to connect these four inputs individually to the power supply through 4 feedthrough capacitors, and connet 4 at least 1800uF capacitors as well to the 4 PA inputs. Do you think it's really necessary? I mean all these capacitors? I don't have much experience on this. The max. power I even handled on PA is 200W, and I didnot need capacitors at 200W level to operate it.
Thanks in advance!

bj

 

[VEBill]

"Do you think it's really necessary?"

Yes.

Follow the vendor's instructions carefully. It's common for amplifier modules and subassemblies to be damaged during the intial stages of integration.

 

[itsmoked]

I concur with VE1BLL. 80A hookup may mean 120A spikes or something. The wire run could cause a lot of drop on those spikes which could distort the output or damage something. You could probably reduce the capacitors if the PA is within 2 feet or so of the supply.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[VEBill]

I'm more worried about the amplifier deciding to oscillate at some random frequency until it destroys itself. I'm so paranoid that, during initial power-up, I'd probably have a oscilloscope AND a spectrum analyzer both running with max gain with small wire antennas placed around the amplifier and/or tapped into the output (suitably attenuated). I'd believe the new amplifier is stable when I see that it's stable.

Problems are more common during initial integration because the bench test setup probably isn't as well bypassed as would be a final product. Long ground wires etc.

 

[Warpspeed]

All of the above.

The suppliers of that module have obviously done some pretty thorough testing, and have perhaps discovered certain instability problems can sometimes arise. If they say these precautions are required, do it without hesitation.

Also make sure your feedthrough capacitors are physically large enough to carry considerable RF and dc current without overheating or self destructing. They may be able to advise you on a suitable supplier and part number.

 

[itsmoked]

See you guys have jumped to the RF realm....I thought audio... Both can have PAs..

hmmmm.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[waross]

Hi keith;
I thought that I had the franchise on this kind of confusion.
I wondered a little until I realized that PA was Power Amp, not Public Address. Check the title of the post.
respectfully

 

[itsmoked]

[highlight]DOH![/highlight]


Now where were those apology forms...

Hey, my son's room is filled with audio power amplifiers..

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[Warpspeed]

It was the mention of feedthrough capacitors that convinced me this was a 500 watt "brick" wideband RF amplifier we were discussing.

Still..... A wideband power amplifier is still a wideband power amplifier, and the problems do not just all go away because it is built for audio frequencies.

I believe all the above comments are still most appropriate dispite the confusion.