[Amps] Powering 400w mobile amplifier...

[jeff millar]

Gerry...

Definitely run two wires to the battery.  Also ground the Amp solidly to the
car frame at it's mount point.  Also fuse _both_ power wires near the
battery.  Several scenarios to worry about.
    1. Battery ground to frame loses connection and you go to start it...all
starter motor current goes through Amp ground lead
    2. Amp ground lead opens, all amp current goes through coax to antenna
ground

If you try to return the amp current through the frame, it generates voltage
drops across various frame to body joints and interferes with radios,
computers, sensors, etc.

Most cars have a hole in the firewall above the brake pedal with a rubber
grommet, about 2 inches diameter, slit it and run the wire through
there...careful route it and tiewrap it off to not interfere with brake and
gas operation.

A 400 W amp PEP amp at 60% efficiency will draw about 50 amps on voice
peaks.  A 1F cap will drop 1/2V per 10 milliseconds at 50 Amps...sounds
helpful, but expensive

15 Ft of #8 wire (x2 for + and -) will drop about 1 V at 50 Amps
15 Ft of #4 wire (x2) will drop about 0.38V at 50 Amps.

FET amplifiers have rather little sensitivity to supply voltage, a 1 V
ripple under load due to wire seems reasonable.

Conclusion:

    #4 wire probably adds .62V to the amp on peaks, which gives about 0.4 dB
more PEP, not really worth it
    The 1 F cap probably adds a bit less than that, even less worth it...but
very cool.

jeff, wa1hco


----- Original Message ----- 
From: "Gerry Hull" <windev at inetmarket.com>
To: <amps at contesting.com>
Sent: Monday, July 28, 2003 10:38 AM
Subject: [Amps] Powering 400w mobile amplifier...


> Hey Folks,
>
> I just purchased a TE Systems 1454 400w 2m amplifier, which I am going to
use
> both mobile and in fixed-station use. My question is about DC
> power wiring in my '03 Chevy Suburban.  I believe I will have aprox. 12
feet
> from the battery to the amp.   Is #8 going to be large enough, or should I
go
> with #4?  Is it better to run both + and - to the battery, or find a
ground
> somewhere near the amp?    I notice the high-power audio amp people use
1-farad
> caps near the power input of their amps... anyone used this in an amateur
amp
> configuration?  Seems like it would help on those current peaks.
>
> Finally, the Suburban is the "family" car, and the amp will not be there
> permanently... any suggestions on how to get the wire through the
firewall,
> without ticking off the XYL?
>
> 73,
>
> Gerry Hull, W1VE
> Hull Computer Consulting
> Custom Solutions for Broadcast Automation
> POB C, Greenfield, NH 03047
> Home Office/fax:    603-547-8327
> Toll Free:          866-823-5473
> email:              windev at inetmarket.com
>
>
>
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