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?
2. Is this a good combo?
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.

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.

Thanks
Rock

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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you might be using cheap coax
(never use foam!

foam diaelectric is actually the better coax. it's velocity factor is
higher, less loss.
ron

Wow, there is alot more to this than I thought. I have alot to learn but now I
know where to start. Thanks

On Mon, 19 Jul 2004 14:30:11 GMT,
wrote in :

you might be using cheap coax
(never use foam!

foam diaelectric is actually the better coax. it's velocity factor is
higher, less loss.
ron


The velocity factor has nothing to do with performance, and the
difference in loss is insignificant unless you plan on running several
hundred feet. What -is- significant is that foam is easily ruined by
mild heat, moderate bending or crimping, and humidity that gets
trapped inside. Foam is a poor choice for mobile installations.





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Ok im going to ground the radio and the amp tonight. starting with the antenna,
what should I replace the wilson mag mount with. I went with the mag mount due
to parking in a car port. that way i could pop it off and set it in the bed of
my truck. I wont lose any sleep over dumping the wilson but what shoud I get. I
plan on upgrading every thing now but I would like to start with tha anyenna
and then move on to radio. one thing at a time $$. It looks like I wasted money
the first time around I would like to get it right this time.

thank agan

Rock
by the way I was stationed in Miomar San Deigo and 29 palms.

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.

Most "tune-ups" involve stretching the coils that make up the low-pass filter.
A watt meter reads all wattage, no matter what it's frequency.

Now your amp and antenna reject the second harmonic and reflect it back to the radio.

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?
2. Is this a good combo?
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.


What you failed to mention was the SWR with the amp out of line.

-Scott, with the KW-7 really mounted to the rear bumper, and a 1.5:1 SWR that TALKS.
I still prefer resonance to perfect SWR! Oh yeah, 7 feet of coax...enough to make it from
the box to the antenna mount. No crimped connectors here. 2x455 box fed by #6.

On 19 Jul 2004 21:52:47 GMT, (ROCH USMC) wrote in
:

Ok im going to ground the radio and the amp tonight. starting with the antenna,
what should I replace the wilson mag mount with. I went with the mag mount due
to parking in a car port. that way i could pop it off and set it in the bed of
my truck. I wont lose any sleep over dumping the wilson but what shoud I get. I
plan on upgrading every thing now but I would like to start with tha anyenna
and then move on to radio. one thing at a time $$.


If you have a roll-bar or utility rack you can weld a bracket at the
top, then use just about any type of whip with a quick-disconnect
mount. For top-mounted antennas I prefer center-loaded whips, but
others like fiberglass and they work fine, too. Or, if you really want
top-notch performance (in -both- Tx and Rx) you might try a full-sized
9' whip on the rear bumper and tie it down when not in use. I have a
9' whip mounted on the center of my roo-guard in the front and tied
back so it doesn't catch on the brush. Anywayz, the 9' whip shouldn't
cost you much more than $20-$30 for both the whip and mount. On the
places where the antenna mount contacts the metal of the vehicle, make
sure it's contacting clean, bare metal and makes a GOOD connection.
For coax, get some RG-8 or better and avoid crimp connectors. If you
have a soldering gun, learn to solder them yourself. It's ok to use up
some coax to practice soldering these connectors because the results
are worth the effort.


It looks like I wasted money
the first time around I would like to get it right this time.


Nothing was wasted. It's always good to have a backup. Keep the old
mag-mount for emergencies.


thank agan

Rock
by the way I was stationed in Miomar San Deigo and 29 palms.


Far out! I was in Stumps for C&E from late '81 to early '83!






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"Scott in Baltimore" wrote:
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.

Most "tune-ups" involve stretching the coils that make up the low-pass
filter. A watt meter reads all wattage, no matter what it's frequency.

Now your amp and antenna reject the second harmonic and reflect it back
to the radio.

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?
2. Is this a good combo?
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.

What you failed to mention was the SWR with the amp out of line.

-Scott, with the KW-7 really mounted to the rear bumper, and a 1.5:1 SWR
that TALKS. I still prefer resonance to perfect SWR! Oh yeah, 7 feet of
coax...enough to make it from the box to the antenna mount. No crimped
connectors here. 2x455 box fed by #6.


Rock on!

Steve with his Wilson 1000, two pill, and 2510 hard wired to the roof
of his truck..all connections soldered all the way to the battery.

Can't beat -good- hardware.

(ROCH USMC) wrote:
Ok im going to ground the radio and the amp tonight. starting with the
antenna, what should I replace the wilson mag mount with.

Did you just buy the Wilson mag, or did you have it already?