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Slim304

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Dec 31, 2019
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I'm running a president Richard doing around 45 watts the swr is saying on the radio 1.6 to 1.7 but on my analyzer it's saying the swr is 1.0 what should I believe?
 
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Captain Kilowatt

Professional Amateur
Staff member
Apr 6, 2005
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All the amateur gear I've used was always fairly close to my external meters. Cb and exports I gave seen some dissimilarities... especially if they had been "peaked and tweaked"

Agreed. once the golden screwdriver gets into the radio, all bets are off. Most of the time meters that are "self calibrating" and read SWR without the need to adjust full-scale then flip a switch, will read way off after being tweaked. Stock radios never seem to be of any concern when it comes to using the built-in meters.
 

The DB

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Aug 14, 2011
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think I read somewhere that the SWR will be different depending on where in the line you measure. Maybe that was for people who tune with different lengths of coax? So probably doesn't apply to a properly tuned system.

Yes and no. Lets start with the no.

It is common knowledge that if the load does not match the impedance of the feed line, then as you travel up said feed line X and R will change. Where a lot of people go wrong is they assume that just because X and R are changing along the length of the feed line, that SWR will also change. This is not the case. In fact, over an electrical half wavelength of feed line, every possible combination of X and R to make up that specific SWR will appear.

Typically in mobile installs, but sometimes can be seen in base installs as well, some people notice that as they change the length of the feed line that the SWR measured also changes. This is actually the sign of a problem, they just aren't aware of said problem. In most cases, this is caused by common mode currents, but can also be caused by other things such as ground loops. Some people, unaware of the problem that is right in front of them, actually think they are tuning the antenna by changing the length of said feed line, and this does hide but does not fix said problem. In fact, these setups tend to have various other problems caused by said hidden problem, such as finals getting blown early, or getting bitten by the mic on the radio when transmitting, ect.

Now the yes.

If I just leave the above as it is, someone is going to come along and say that there is losses in the feed line and those losses will change the SWR. This is both 100% true, and out of context of what is typically being discussed. Assuming you don't have a bad jumper cable between the SWR meter and your radio, the change in SWR from this loss over said jumper cable isn't enough to be picked up by a typical SWR meter or even many antenna analyzers, including the venerable MFJ-259 series. Because of this, very few people have the ability to even measure said SWR difference. If we were talking about a much longer feed line run than a simple jumper cable, it very well might come into play, but when this is typically discussed, we are taking about very short lengths of coax, so short that this fact doesn't come into play.


The DB
 

Captain Kilowatt

Professional Amateur
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Apr 6, 2005
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I think I read somewhere that the SWR will be different depending on where in the line you measure. Maybe that was for people who tune with different lengths of coax? So probably doesn't apply to a properly tuned system.

SWR does not change along the cable length but the impedance does change if the antenna is not a pure 50 ohms resistive load. I know that sounds contrary but it is true. If the SWR is 2:1 is the impedance 25 ohms or 100 ohm s? Both values will give you the same SWR. In fact there is an almost limitless combination of ohms, Xc and XL that will result in the same SWR reading. This is what you see along a transmission. The actual impedance changes but the SWR does not.
 

Marconi

Usually if I can hear em' I can talk to em'.
Oct 23, 2005
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I'm running a president Richard doing around 45 watts the swr is saying on the radio 1.6 to 1.7 but on my analyzer it's saying the swr is 1.0 what should I believe?

Slim304, if you are testing your SWR with your analyzer connected to your feed line, try changing the length of the feed line by adding a 1' - 6' jumper and compare these 2 results.

I hope I said this right.
 
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nomadradio

Analog Retentive
Apr 3, 2005
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Louisville, KY
www.nomadradio.com
And maybe the spectrum coming out of the radio contains some energy that's not exactly on the channel selected?

If it does, the SWR will read high, since all the RF energy at frequencies out in left field gets reflected. The radio's internal SWR meter just adds all those frequencies together into one reading.

Maybe. Or maybe the radio's internal meter lacks accuracy. A 50-ohm dummy load might reveal this. A 25-ohm or 100-ohm dummy load would show how close it comes to reading an accurate 2 to 1. Either resistor should represent that SWR reading.

73
 

Marconi

Usually if I can hear em' I can talk to em'.
Oct 23, 2005
7,082
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Houston
Amen Nomadradio, all of the above.

I recently bought a version 1 Stryker 955HP for a base radio setup and a new A99. I was banking on not needing to tune the A99 based on the words from Solarcon regarding changes in length and shipping and a guarantee to still work CB .:sick:

So, I did not try and tune the antenna, even though I found it to be 13" shorter than the older (say original type) A99's I've had over time.

The radio meter shows 1.5 SWR over most of the CB band, and about 75-80 watts peak modulated on sideband. I thought, "...could I be so lucky."

Later I got a new analyzer and the match and the power show what I report above, but the values of R,X,Z are no where near good. True enough, I have the antenna setup in a bad location, height at only 10' feet to the base of the antenna and close to the roof of my home. That was all done in a rush and for shear convenience.

I physically* can't do the work anymore, and the help was inexperienced with antennas. I also can't I say the analyzer is right or even close. IMO, this short A99 results are NOT good for a 2-way radio system in 11 meters and probably in 10 metters too. This looks like a compromise to the almighty SWR results.

From what I can tell, the A99 is resonant with settings as done by the factory. The analyzer shows the resonance is close to 27.5 MHz, also showing about 1.5 SWR just like it does in the CB band.

Resistance and reactance at 27 MHz are a mess.

Due to my *limitations, I will be ordering a no-tune-necessary Gain Master, and I sure hope Sirio has not changed the GM since the first one I bought...soon after that antenna was introduced some years ago.

Stay tuned!
 
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AudioShockwav

Extraterrestrial
Staff member
Apr 6, 2005
7,494
5,217
593
Sierras Near Yosemite National Park
Amen Nomadradio, all of the above.

I recently bought a version 1 Stryker 955HP for a base radio setup and a new A99. I was banking on not needing to tune the A99 based on the words from Solarcon regarding changes in length and shipping and a guarantee to still work CB .:sick:

So, I did not try and tune the antenna, even though I found it to be 13" shorter than the older (say original type) A99's I've had over time.

The radio meter shows 1.5 SWR over most of the CB band, and about 75-80 watts peak modulated on sideband. I thought, "...could I be so lucky."

Later I got a new analyzer and the match and the power show what I report above, but the values of R,X,Z are no where near good. True enough, I have the antenna setup in a bad location, height at only 10' feet to the base of the antenna and close to the roof of my home. That was all done in a rush and for shear convenience.

I physically* can't do the work anymore, and the help was inexperienced with antennas. I also can't I say the analyzer is right or even close. IMO, this short A99 results are NOT good for a 2-way radio system in 11 meters and probably in 10 metters too. This looks like a compromise to the almighty SWR results.

From what I can tell, the A99 is resonant with settings as done by the factory. The analyzer shows the resonance is close to 27.5 MHz, also showing about 1.5 SWR just like it does in the CB band.

Resistance and reactance at 27 MHz are a mess.

Due to my *limitations, I will be ordering a no-tune-necessary Gain Master, and I sure hope Sirio has not changed the GM since the first one I bought...soon after that antenna was introduced some years ago.

Stay tuned!

It would be good to hear you back on the air Eddie.

It's a crap move on road-pro, who are very aware of what they have done, to keep selling them without including the extension.

73
Jeff
 

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