On 19 Jul 2004 05:01:36 GMT, (ROCH USMC) wrote in
:

Hi
Here is what I just got, Cobra 29 LTD Classic that was bumped up a bit, a new
Palomar Elite 300 amp (ebay) , Diesel (?) noise canceling mic and a Wilsom
5000 mag mount ant.

I cant get the SWR down below 2.5. I ran a new 18' cable and a ground wire to
the frame of the truck but ever time i key up the ANT light lights up on the
radio.

My questions a

1. How can I get the SWR down?


Just three words: Grounding, grounding, and grounding. You need to
ground the radio AND the amp AND the antenna. By "grounding" I mean an
"RF ground". At 27MHz, this means mounting the radio and amp directly
to the chassis and/or using grounding straps that are no more than a
few inches long. Only after your system is properly grounded can you
address any other issues. And those other issues can be many. For
example, your 'bumped' Cobra may have been 'bumped' by a moron; your
Palomar may have a detuned input or output, a bad power transistor, or
even worse it might be self-oscillating; you might be using cheap coax
(never use foam!); you might have a bad antenna; etc. But regardless
of the problem, it's always easier to troubleshoot if the system is
properly grounded.


2. Is this a good combo?


Not really. The makers of these cheap linears (that usually aren't
very linear at all) don't tell you that the power rating is for -peak-
power. IOW, a 300-watt amp will do 300 watts PEP, which translates to
a maximum of 75 watts RMS (AM carrier power). Push it any harder and
you will get a bigger carrier, but you start clipping well below 100%
modulation, splattering your signal across the spectrum. You should
have had your Cobra 'dumped' instead of 'bumped'. As for a mag-mount,
personally, I wouldn't waste my money. But you have, so you should
know that 18' of coax isn't a reliable substitute for the terrible
grounding characteristics of mag-mount antennas. If you want real
power you need a real antenna, not a glorified refrigerator magnet.


3. on my amp it has a ON/OFF , HIGH, MED, LOW and a PRE-AMP on and off.
What is with the PRE- AMP.


The pre-amp is used to amplify the received signal. They are mostly
worthless because the signal-to-noise ratio of modern radios is
usually much better than the S/N ratio of the pre-amps. IOW, they will
just make the noise louder. However, they work great for older and
low-end transceivers, and simple homebrew receivers.


Ok I know I will take a beating from some of you and that is part of the game
but any help or any suggestions would be great.


Here's your beating: If you want to play 'hammie', get a license. If
you can't afford a license (about the price of a happy-meal), or if
the test is too difficult (even when you are allowed to memorize the
questions and answers before the test), then at least get yourself a
book on the subject and learn what you are doing.


Thanks
Rock


Where were you stationed?





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