[Boatanchors] Fw: kinda OT but related

[Roger Ruszkowski]

Dick,

Down load a couple off application notes for the 7812
7809 7805 regulators off the web pages.

You want a couple of caps and of different types on both the input and output.

You would think that if you just had a pair of caps in parallel the values would
add up and then so what and more is good.

But different caps have different impulse ratings and thus grab the
noise spike in different ways. Lots of detail in some of the application notes.

Mostly you are going after ignition noise then alternator noise and then 
the infrequent spikes as sensors switch on and off.

wire length from the lighter socket ground to the regulator will also pick up
some power line hum as you drive by large offending sources.

You should be able to easily get a good noise limiting circuit together.

Roger AI4NI


-----Original Message-----
From: Dick KF4NS <kf4nsradio at verizon.net>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Tue, Jul 31, 2012 7:02 pm
Subject: [Boatanchors] Fw: kinda OT but related


| Need some advice guys. I am assembling a power adapter for my ICOM HT using a 
gutted battery pack and a
| cigar lighter plug. Before I put this thing together I would like to know your 
opinions on using some
| sort of input filter ahead of the 7812 regulator and it's in and out caps.
|
| I have referred to the ARRL RFI manual chapter on automobile interference. 
Going through several other
| books I have, I still have not made any conclusions regarding exactly what 
type of filter to use if 
any.
| I use the HT in my 2003 Honda Accord with a trunk mag mount. Using the rig 
with the standard battery 
pack
| there is no noise whatever. Of course the batteries act as a filter 
themselves. Have not tried a direct
| 12vdc hookup yet.
|
| Let me know of your experiences and any advice. It would be appreciated.
|
| 73, Dick KF4NS
| St Petersburg, FL 33714 USA
| Keep The Glow!
| 

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