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Old 08-31-2013, 05:34 PM   #1
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SWR - When do I say good enough

I'm tuning my antenna and wonder if I really need to be all OCD about getting an SWR as close to 1 as possible. How big a difference will it make if I settle for 1.8? It's driving me nuts tweaking the antenna. As I understand it, anything under 2 is OK.

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Old 08-31-2013, 07:54 PM   #2
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Over 3 may well start causing damage to your radio. between 2 and 3 is generally safe but will severely limit performance. under 2 is getting good and performance will increase.
You need to understand what SWR is. It's a fraction of the RF energy your radio puts out being reflected back at your radio. In other words, not being sent out to be received by another radio. Your CB is already pretty weak at 5 watts so the more power you get to actually leave the antenna the better.
The question becomes, what do you want your radio to do? Just talk to folks running in a group? You'll probably be fine with what you've got. Want to get out and touch someone? get it as close to 1:1 as you can.
Then again, a guy with 102 inch stainless whip and an SWR of 1.8 will walk all over a guy with a 1:1 and a 3' Firestick.
You're 1.8 will work. no way to know how well it will work or how much you're limiting yourself without seeing the setup.

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Old 08-31-2013, 08:40 PM   #3
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Quote:
Originally Posted by hayhonker View Post
I'm tuning my antenna and wonder if I really need to be all OCD about getting an SWR as close to 1 as possible. How big a difference will it make if I settle for 1.8? It's driving me nuts tweaking the antenna. As I understand it, anything under 2 is OK.
Under 2 is typically "good enough" but with a little tweaking, usually at the mount, it's usually possible to get down below 1.5:1.

You're not using an NGP (no groundplane) type of antenna are you? That type of antenna does not work very well on a Jeep (or anywhere for that matter) and it can make getting a low SWR difficult.

What type of antenna mount are you using? Is the antenna mount getting a good sold bare metal-to-metal connection to its body mount? Is the body mount getting a good solid bare metal-to-bare-metal connection what it is attached to on the Jeep? A good solid bare metal ground connection between the right part of the mount & the Jeep is critical to getting a good low SWR.

Can you take a good close-up photo of your antenna mount? One additional photo from the underside of it would be helpful.
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Old 09-01-2013, 08:59 AM   #4
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Thanks for the replies guys. Ahhh a good night's sleep made the difference. I was able to dial in <1.5 on ch 1 and 40. I read somewhere to adjust the antenna in 1/4" increments. That wasn't working so well so this morning I adjusted in 1/4 TURN increments and got below 1.5 in about 4 tries. Now I need to research how to minimize noise when the engine is running.

Uniden 520xl, 18' firestik coax, spring and 4' firestik antenna. Wired to spod. Would going straight to the battery be better?

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Old 09-01-2013, 12:03 PM   #5
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Powering a 2-way radio should always be directly from the battery. The battery is, by far, the cleanest source of DC power which means it won't have electrical noise on it from the alternator, fuel pump, etc. like can be found if you pick up power for the CB somewhere else like the fuse panel behind the glove box. 2-way radios can pick up that type of electrical noise which will make its way into the transmitted and received signals.

Using noise producing parts like low-resistance spark plug wiring and non-resistor type spark plugs can introduce spark noise into a CB that can be very difficult to eliminate without replacing those items with the correct resistor-type parts. Resistor ignition wiring and resistor spark plugs are what the factory installed and due to how Ohm's law works, the added resistance (which eliminates ignition noise) does not appreciably reduce the voltage delivered to the spark plug electrodes.
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Old 09-01-2013, 02:02 PM   #6
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Well....that gives me an excuse to heat up the solder station. The power leads won't reach the battery. I thought the spod was supposed to provide clean power/ground but it's been over a year since I installed it and I forget. Maybe that is the issue.
I've got stock plugs/wires so no problem there.

I have to laugh-I'm researching this noise issue on a few different forums (but only posted here) and see that you have been answering these questions for many years. Thanks for continuing to reply, and not just copy-n-pasting something your wrote in 2009 that is still correct
I now have a few ideas from other forums that I will try too.
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Old 09-01-2013, 02:48 PM   #7
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If you do extend the wires to reach the battery, fuse both the pos and neg preferably near the battery - someday if a chassis ground corrodes or works loose you don't want to sink a ground path through the radio. It will cook the smallest path usually the tiny copper traces inside the radio.

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