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Author Topic: Do I have to worry about SWR on a moblie 2 meter rig?  (Read 3916 times)
WALTERB
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Posts: 528




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« on: May 15, 2011, 08:26:33 AM »

I just set up my two meter Yaesu in my car and the reports were wonderful. Everyone said it was hitting the repeater fine.

I scanned the .pdf manual and can't find anything about SWR.  I assume its nothing to worry about??

thanks
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KE3WD
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Posts: 5689




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« Reply #1 on: May 15, 2011, 10:14:48 AM »

Well, you don't have to *worry* about it, but it is nice to know information. 

If your radio is presently showing full output power into your antenna system, it is a safe bet that your SWR is below two-to-one anyway. 


73
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WB6BYU
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Posts: 13341




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« Reply #2 on: May 15, 2011, 07:01:52 PM »

That partly depends on how far away the repeater was.  I have some I can hit on a dummy load: even
if the antenna has broken off I'm still full quieting, but that doesn't mean my signal will hold up for any
distance.

It's a good idea to make sure your antenna is working properly.  Some have tuning adjustments so you
can vary the length for minimum SWR.  I always make sure that the SWR is reasonably low on my 2m
mobile antennas - a cheap CB SWR meter is usually adequate for this.  If it is, then I connect the
cable straight to the radio and don't bother checking again unless I have problems. 

Then see what repeaters you can hit at the different power levels you have available.  I rarely use the
full available output power unless I'm in a very marginal location.  But if you used to be able to hit a
repeater at 5 watts and you get reports of a scratchy signal, it's time to check the antenna rather than
increasing power.  Running the rig at full power into a bad SWR can cause them to overheat, and
overheating (running too much power for too long into a poor SWR or with poor air circulation around
the heatsink) is the only way I've ever damaged the finals in a radio.
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WALTERB
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Posts: 528




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« Reply #3 on: May 15, 2011, 10:07:32 PM »

ok, thanks!
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KI4SDY
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Posts: 1452




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« Reply #4 on: May 18, 2011, 04:40:16 AM »

You don't have to worry about SWR unless you are concerned about transceiver performance or whether or not you will burn up your transmitter!  Shocked

Modern transceivers have protection circuits, but they can fail or may not be able to prevent a bad match or dead short from damaging your radio. If that happens, it will cost as much as the radio is worth to fix it, if it is not under warranty  Cry

I was giving a speech on Elmering a few years ago at the local ham club and when I asked how many members had burned up a transmitter. About a third of them raised their hands ( those were the ones that would admit it and yes my hand was up).

One of the first things you need to buy is a SWR meter for all the radios that you use!  Grin
« Last Edit: May 18, 2011, 04:42:01 AM by KI4SDY » Logged
W8AAZ
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Posts: 348




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« Reply #5 on: May 30, 2011, 05:35:56 PM »

I always check and tune antennas for optimum performance.  With some of them, like say, a mag mount quarter wave antenna, it will probably come from the factory with a reasonable match if it is represented as a two meter antenna, not tunable for all over.  Lot of antennas will require adjustment though.  I have checked match from the beginning of my 2 meter experiences, even if it was with a cheaper RS or equivalent type old fashioned SWR meter.  I use a Bird meter now.  But spend a few bucks and get a meter, even the bare minimum to check antennas, you will use it more than once.  I would not dream of doing otherwise. Maybe not on an HT factory made antenna.
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KM3F
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Posts: 509




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« Reply #6 on: May 31, 2011, 12:17:06 PM »

Worried?
No but concerned enought to put an SWR meter in line at the radio to see what you have.
Suppose the transmission line is shorted or open?
It can damage the last amplifier no matter the protection built into the radio even testing so don't take any more chances than you need to.
There was a thread about  losing two radios, on one of these boards.
Come to find out the antenna was made out of a coat hanger and all rusted.
Did it make sense to ask why two radios were lost and be concerned about the cost of repaires and finding parts?
Good luck.
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KI4SDY
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Posts: 1452




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« Reply #7 on: June 01, 2011, 05:35:46 PM »

"Come to find out the antenna was a coat hanger and all rusted."

That was a joke post by a ham that was pulling your legs, right?  Cheesy
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K1CJS
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Posts: 6045




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« Reply #8 on: June 03, 2011, 06:29:22 AM »

Worried?
No but concerned enought to put an SWR meter in line at the radio to see what you have.
Suppose the transmission line is shorted or open?
It can damage the last amplifier no matter the protection built into the radio even testing so don't take any more chances than you need to.

You still don't need a SWR meter for that.  A simple ohmmeter will suffice to let you check continuity and for shorts.

With that being said, a simple test will suffice.  After you've been transmitting for a short time, feel the case of the rig toward the back.  If the rig is hot (not just warm, but hot) then you may have a problem with SWR. 

Another thing you may try is to ask another ham if they would check the SWR for you, or let you borrow their meter.
« Last Edit: June 04, 2011, 07:29:19 AM by K1CJS » Logged
KC8OYE
Member

Posts: 297




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« Reply #9 on: June 23, 2011, 06:31:03 PM »

"A cheap CB swr meter will work fine"

not usually... I've yet to see a 'cheap cb' swr meter that was even close to accurate on 2m.


i was just a buddies house using his meters, and his Diamond Antenna SWR meter for HF said I was putting out 15w on high power into a dummy load... his 2m/70cm specific SWR meter showed a full 50w which is the correct number. and 35w on 70cm..
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N6AJR
Member

Posts: 9910




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« Reply #10 on: July 08, 2011, 05:08:59 PM »

see if you can borrow a MFJ 259 b antenna analizer and check it out several ways with that.  is there a local club, ask some one on the repeater for some help.  be sure.
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