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Author Topic: ANTENNA ANALYZER QUESTION  (Read 2094 times)
KD8GLK
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Posts: 19




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« on: January 13, 2018, 06:53:58 AM »

Correct me if I am wrong, but from what I am reading about antenna analyzers, you can eliminate the use of an antenna tuner,SWR meter and a radio to key it up.   Just plug your feed line into the analyzer, balance your antenna to the proper band ( in my case 40m) unscrew the feed line from the device  and into your radio and your good to go. 

Am I correct on this assumption?

Carl
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WB6BYU
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Posts: 17482




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« Reply #1 on: January 13, 2018, 07:25:00 AM »

That depends on the antenna...

If you are using a dipole, or other antenna that can be adjusted to 50 ohms, then, yes, you can
use the antenna analyzer to tune the antenna for minimum SWR, then plug it into the rig and it will
still have a low SWR (assuming you have an effective balun so there is no common mode current on
the feedline.)

Of course, if that is all you need, you can do it with the rig and an SWR meter.  (Before the advent
of the hand-held SWR analyzer, I used to drag my rig up onto the roof to adjust my antennas.  It
was much easier once I switched to a solid-state rig.)


But the analyzer will do much more as well.  For example, if you have an end-fed wire, a loop, or
antenna fed with ladder line, it can measure the impedance at the feedpoint so you can choose an
appropriate tuner to match it.  In that case you can also use it to adjust the tuner.  In that situation
it doesn't eliminate the tuner, because the antenna by itself can't be adjusted to a low SWR.
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AB4ZT
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Posts: 30




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« Reply #2 on: January 13, 2018, 07:29:08 AM »

Yes, but:

 - You would not use an antenna tuner to trim an antenna to a particular frequency anyway.

 - If you are using the antenna on a particular band, you may not need the tuner in operation either, if your antenna is broadbanded enough.

 - You would not need the SWR meter to trim the antenna, but you do want to keep one in line during operation - a significant change in SWR would let you know something has gone wrong (connector failure, feedline issue, antenna fell down (!)).

So you are correct, just need to connect analyzer to antenna and trim away.  I do not know what analyzer you are using, but some units (mine for example - MFJ 259B) are quite susceptible to static charges, and a disconnected antenna can hold a static charge.  For that reason, I always short the antenna terminals before connecting to the analyzer.

73, and have fun with your antenna!

Richard, AB4ZT
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WY7CHY
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Posts: 840




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« Reply #3 on: January 13, 2018, 10:42:29 AM »

The only thin I would add, is that I come from the school that the antenna and feed line are not separate pieces. They are part of the antenna “system”. As such, I wouldn’t connect an analyzer directly to an antenna to adjust or trim it. I would connect it to the feedline in the shack that is connected to the antenna. The feedline, will affect the resonance of the antenna. BYU is correct that you do need to ensure that you are using the appropriate balun if needed. Again, you need to look at the entire antenna “system”.

A tuner shouldn’t be in line with an analyzer. Yes, it too is definitely part of the antenna system, but it’s an adjustable component to that system. It adds and subtracts capacitance and inductance to the antenna system to reduce reactance and match the antenna system to the rig. But a tuner isn’t a magic box. It isn’t designed to match a 10 foot piece of wire to your rig and have you talking around the world on 80 or 160 meters. But for a loop, dipole, or similar and matching wavelengths/fractions of, to fine tune or to use for multi band, they work great.

But for the analyzer, connect just it with the feedline and antenna; and appropriate balun/unun if necessary. Remember too, an analyzer can do so much more than just tuning for a low swr. Low swr doesn’t always mean the antenna is properly resonant. The analyzer will help you find true resonance.
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Born Wild - Raised Proud: 73
Cheyenne, Wyoming
W9IQ
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Posts: 1845




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« Reply #4 on: January 13, 2018, 11:27:07 AM »

The only thin I would add, is that I come from the school that the antenna and feed line are not separate pieces. They are part of the antenna “system”. As such, I wouldn’t connect an analyzer directly to an antenna to adjust or trim it. I would connect it to the feedline in the shack that is connected to the antenna. The feedline, will affect the resonance of the antenna. BYU is correct that you do need to ensure that you are using the appropriate balun if needed. Again, you need to look at the entire antenna “system”.

...

But for the analyzer, connect just it with the feedline and antenna; and appropriate balun/unun if necessary. Remember too, an analyzer can do so much more than just tuning for a low swr. Low swr doesn’t always mean the antenna is properly resonant. The analyzer will help you find true resonance.

The feedline will typically transform (change) the impedance that is present at the antenna to a different impedance at the transmitter end of the feedline when the antenna impedance does not match the feedline impedance. Thus the notion that the analyzer can be used at the transmitter end of the feedline to adjust the antenna for resonance is often fraught with difficulties.

A few of the new analyzers can back out the feedline transformation; you could manually do it with a program like TLDetails; or you could use a feedline that is electrically a half wavelength long. But short of those types of options, it is always more informative to have the analyzer at the antenna when taking readings or making adjustments.

- Glenn W9IQ
« Last Edit: January 13, 2018, 11:34:03 AM by W9IQ » Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
WB3CQM
Member

Posts: 219




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« Reply #5 on: January 13, 2018, 11:37:57 AM »

The only thin I would add, is that I come from the school that the antenna and feed line are not separate pieces. They are part of the antenna “system”. As such, I wouldn’t connect an analyzer directly to an antenna to adjust or trim it. I would connect it to the feedline in the shack that is connected to the antenna. The feedline, will affect the resonance of the antenna.
Well I will disagree with the above statement . I was taught by one of the greatest antenna man in the world  to tune the Vertical T I have and find Xf= 0 by connecting the analyzer directly  to the vertical wire . Then add the matching then add section of  coax to Balun  then coax feed line to transmitter . The balun is to separate the antenna from the feed line so the feed line Is Not radiating. Any length of coax was used and had no effect on my swr from what i could see. I think feed line   is part of the system per say  but should  Not effect the antenna  is my understanding  .

Now I ref. Array of Light by Tom Schiller N6BT Page 14 . He has hooked up a 150 watt light bulb to be  a antenna and down the paragraphs go's to say - The light bulb is fed through a current  balun with 3'' leads  and the feed line is 9913 Flex, to minimize loss . A balun was used to insure feed line would not radiate.

When I check all my Beverage receive antenna I do so at the transformer with a AA-230 Zoom Rig Expert to scan the swr. I would Not use my transceiver to do so, though i guess I could just lower power less than 1 watts. But I will not do such, my coax is not the receive part of the antenna the Beverage is the antenna .

When my antenna beam antenna were installed by a professional they were raised with crane and in the air with short lead of coax tested. Not at the shack for the feed line is Not  part of system from what i understand but when I use SWR at the transceiver it is clear the SWR is 1.1-1 on resonant freq. All my beams have balun to separate antenna from feed line.

Now if I am wrong some one needs to explain this to me where I am wrong.
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G8HQP
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Posts: 682




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« Reply #6 on: January 13, 2018, 12:53:15 PM »

You are both right. The feeder is part of the antenna system, but by careful adjustment it is possible to arrive at a situation where the feeder does very little apart from getting energy from A to B. It is helpful to know whether this is the case for your particular antenna system, as assuming that it is the case when it is not the case can lead to confusion.

It is, of course, also possible by careful adjustment to arrive at a situation where the feeder is an important part of the impedance matching of the antenna system. Finally, it can also be the case that the feeder is an important part of the antenna counterpoise - although users may sometimes be unaware of this, and may even deny it.

In any case, it is helpful to know what you are actually measuring when you put a measuring instrument in the system. Where you put the instrument is part of this, and what you had to disconnect to make way for the instrument is another part of this.
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K1VCT
Member

Posts: 186




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« Reply #7 on: January 13, 2018, 05:02:16 PM »

Correct me if I am wrong, but from what I am reading about antenna analyzers, you can eliminate the use of an antenna tuner,SWR meter and a radio to key it up.   Just plug your feed line into the analyzer, balance your antenna to the proper band ( in my case 40m) unscrew the feed line from the device  and into your radio and your good to go. 

Am I correct on this assumption?

Carl

Not sure exactly what you're asking, but... if you're asking if an analyzer can be used in place of a transmitter for tuning purposes, the answer is yes.   Not a bad way to go actually, to get initial settings close for your tuner. 
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WA7ARK
Member

Posts: 51




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« Reply #8 on: January 14, 2018, 05:29:07 AM »

Not sure exactly what you're asking, but... if you're asking if an analyzer can be used in place of a transmitter for tuning purposes, the answer is yes.   Not a bad way to go actually, to get initial settings close for your tuner. 

I substituted my RigExpert analyzer for my transceiver. My tuner is connected between the RigExpert and my antenna.

I set a frequency. I set the RigExpert to display a "real-time" SWR bar-graph.  I diddle the capacitors and roller inductor settings on the tuner to get a 1:1 match. I record the frequency and tuner settings on paper.

I repeat the process at steps of ~25kHz across the entire band in question. I enter the numbers into Excel, and make a nice plot of settings vs freq for that antenna for that band.

Having the plot makes it easy and fast to get to a new frequency or new band... Much less wear-and-tear on the rig and tuner because the tuning is done at mW; not Watts of RF. Much less QRM, too.
« Last Edit: January 14, 2018, 05:31:30 AM by WA7ARK » Logged
AC2RY
Member

Posts: 452




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« Reply #9 on: January 14, 2018, 06:15:19 PM »

Correct me if I am wrong, but from what I am reading about antenna analyzers, you can eliminate the use of an antenna tuner,SWR meter and a radio to key it up.   Just plug your feed line into the analyzer, balance your antenna to the proper band ( in my case 40m) unscrew the feed line from the device  and into your radio and your good to go. 

Am I correct on this assumption?

Carl

Analyzer will help you adjust antenna so that it would be easier for your tuner to work with it (and thus less power lost in it). Of cause you need analyzer that can scan though the whole band and report not only SWR, but R and X impedance components. Advanced analyzer that has TDR option is also useful to check integrity of your feed line.
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WY7CHY
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Posts: 840




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« Reply #10 on: January 14, 2018, 08:19:27 PM »

Antenna tuners have insignificant loss. Not if tuned properly. The only significant loss is in the feedline. And if you use low loss coax, or better yet balanced feedline, the loss isn’t significant. Either way, loss isn’t in the tuner. At least none to speak of.
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Born Wild - Raised Proud: 73
Cheyenne, Wyoming
KM3F
Member

Posts: 817




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« Reply #11 on: January 15, 2018, 10:56:01 PM »

To be more specific on two points, an internal tuner in a radio can offer a loss of as  much as 10 watts out of 100 and more as the band frequency goes up from the compact space the tuner section resides in..
External tuners offers much less loss and is dependent on design.
.
Use of an Analyzer can fine tune a Tuner's  setting that you cannot see or do with just an SWR meter.
The reason is when the reflected voltage falls below a certain level the diode detectors stop conducting at between .3 and .7 volt.  This results in the meter going to Zero and cannot detect the very small return power left from a very small mismatch still possible in the system or the setting.
It's just a technical point that makes no measureable difference in transmission performance at the very small mismatch..
Of course this all changes with a movement in frequency and where Antenna Q rules.
Good luck.
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N4MQ
Member

Posts: 206




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« Reply #12 on: January 16, 2018, 06:12:41 AM »

I use my analyzer to resonate -tune my remote 12' magnetic loop.  With an antenna switch I transfer the antenna to the analyzer , tune the variable cap and then switch it back to the rig.  Fast clean and does not put carrier signal on the band.  Enjoy Woody

https://sites.google.com/view/n4mq-site/home Grin
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