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Author Topic: checking my antenna  (Read 619 times)
K5BDJ
Member

Posts: 18




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« on: May 01, 2013, 03:54:26 PM »

I have an Autek RF-1 antenna analyzer.   

I'd like to do a check on each of the elements in my antenna system.

They are:

   a.  Dentron RT-3000 tuner

   b.  Coax (RG-8X)

   c.  An Ugly Balun (air choke)

   d.  MFJ G5RV

With the Dentron RT-3000:   When reflected is 0 on your operating freq, it should show 1:1 on the RF-1 (input).  Is this correct?

Coax:   simply ohm it.  Be sure it conducts in the middle, the braid has continuity, and no shorts from the braid to the inner conductor.   

With the Ugly Balun:   I have no idea what to do with it.   You can simply ohm it, and see if anything is in coax steps above.  Are there any other steps you can do with it.   What about losses (if any)?   Any way to see if losses occur?

I guess you could try it on your freq of choice, and see if it shows 1:1 SWR.  Theory being if you have losses, it should show more than 1:1 SWR.....

With MFJ G5RV:  connecting to the input on it should show SWR at low values on band of choice.

Any thoughts on these topics will be appreciated.   Keep it simple, for the simple minded (Watash)....
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K0ZN
Member

Posts: 1536




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« Reply #1 on: May 01, 2013, 06:46:52 PM »

OK.... I will try to be brief.  Problem with that is some people will "attack" the post due to lack of details...but here goes:

a.   Yes.  If your rig shows no reflect power, the RF-1 should show 1:1, but may NOT !!  I have an RF-1 too. It may or may not exactly agree due to
      calibration issues, etc. in both pieces of equipment. The RF-1 can tell you quite a few things if you understand the data from the various functions.

b.   Many ways to check coax. Use of the ohmmeter tells you a few things. It does not measure loss caused by aging, water, etc. It is a DC check
      and a transmission line operates at RF. It could be good at DC but bad at RF frequencies. See the ARRL Antenna Book.

c.  I am not familiar with that balun. Baluns can be designed to give DC ground or not. Just depends on the design. Checking a balun is
     more complex since it is an RF transformer. You wanted a short reply. Do a Google search on how to do that. A balun should not cause
     SWR if it is terminated into its designed impedance load.

d.  The SWR you see at the input of the line from the G5RV will vary radically by band. A G5RV, regardless of commercial manufacturers wild claims will not match well
     on all bands. Again, see the ARRL Antenna book. My guess is that since your RF-1 is set up based on a 50 ohm coax reference, you will get "crazy"
     readings if you hook it up directly to the line from the antenna. If you have a band where the SWR directly from the antenna is low, I would just
     log that reading. As long as you get close to the same reading, then in all probability the antenna is fine electrically. Mechanically, you must pull
     it down and inspect it now and then.

Very Respectfully, Amateur Radio is a technical hobby and because of that "short answers" can often (usually?!) omit information or create myths. Some times
there are no short answers! I would strongly suggest you pick up a copy of the ARRL Antenna Book and put in a little study time. There is no substitute for knowledge in this hobby. The more you know the better your results and signal will be and you will avoid a lot of frustrations. This is a communications hobby but it is also involves electronics and it is not "consumer" electronics.

I suspect you will get some other good answers.

73,  K0ZN
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N4CR
Member

Posts: 1655




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« Reply #2 on: May 02, 2013, 06:05:16 AM »

  Theory being if you have losses, it should show more than 1:1 SWR.....

SWR is not a measurement of loss. It is a measurement of how well your load accepts the power you are sending to it.

A dummy load has a very low SWR. It is all loss. But it accepts the power you send it very well and thus has a low SWR.

Read this:

http://forums.qrz.com/attachment.php?attachmentid=36468&d=1267550097
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
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