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Author Topic: To what frequency do I tune my antenna?  (Read 1718 times)

KD4SBY

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To what frequency do I tune my antenna?
« on: June 04, 2019, 12:22:24 PM »


I live in a deed restricted neighborhood and managed to get permission to construct a vertical antenna. At the advice  of a Ham-friend of mine, I converted the vertical a few years later to a Inverted L, of which one of the sides is the original vertical (a alluminume 21 ft pole.) and for the other side I attached to the top a 22 gauge wire, which runs to a tree in the back of the property. This arrangement is tuned to the top of the 80m band, and works quite well with a 1.5 to 1 SWR by it self.
The question is, to which frequency shall I tune the antenna if now my main interests are changed from the 80m to the 40, 20 and 15 meter bands?  In anticipation of expanding the coverage range of the antenna, I am feeding the antenna now with a coax cable through an MFJ-927 remote tuner, which is located abt. 3ft from the base of the antenna.
(Also, besides the MFJ-927 Remote Tuner, some of the  radios I use have a build-in tuner, so if needed, I have a choice which one to use for different bands.)
Any suggestions are appreciated.
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K1VSK

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RE: To what frequency do I tune my antenna?
« Reply #1 on: June 04, 2019, 02:24:54 PM »


I live in a deed restricted neighborhood and managed to get permission to construct a vertical antenna. At the advice  of a Ham-friend of mine, I converted the vertical a few years later to a Inverted L, of which one of the sides is the original vertical (a alluminume 21 ft pole.) and for the other side I attached to the top a 22 gauge wire, which runs to a tree in the back of the property. This arrangement is tuned to the top of the 80m band, and works quite well with a 1.5 to 1 SWR by it self.
The question is, to which frequency shall I tune the antenna if now my main interests are changed from the 80m to the 40, 20 and 15 meter bands?  In anticipation of expanding the coverage range of the antenna, I am feeding the antenna now with a coax cable through an MFJ-927 remote tuner, which is located abt. 3ft from the base of the antenna.
(Also, besides the MFJ-927 Remote Tuner, some of the  radios I use have a build-in tuner, so if needed, I have a choice which one to use for different bands.)
Any suggestions are appreciated.
I would start simple. Rather than try adapting some hybrid of this configuration into a mutliband antenna, put up a fan dipole for 40 and 20. Fifteen is comparatively dead so not worth including at this time in the cycle. Doing this will allow you to keep what you currently use on 75/80 meters and erect something effective on 40 and 20.

Also, you might get better feedback by posting this in the antenna forum rather than this quagmire.
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KD4SBY

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RE: To what frequency do I tune my antenna?
« Reply #2 on: June 06, 2019, 08:33:49 AM »


To what frequency do I tune my antenna?

This topic was moved to eham forums/antennas, towers,...etc.
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LA9XNA

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RE: To what frequency do I tune my antenna?
« Reply #3 on: July 10, 2019, 12:20:56 PM »

If your limited to only using the whip and possibly a "hidden" top leg for a L-antenna I would start by trying to improve the counter poise.
The better counterpoise you get the more efficient the antenna will be.
Buy, borrow or build an field strength meter. When increasing the efficiency of the antenna you will get a higher field strength, so it is simple to see if its you are improving the antenna.
You have not written anything about how the antenna is installed so i would assume that it is installed on the ground.
Add some extra buried radials and see if your the antenna is getting any higher field strength. If there is limitation of how many radials you can put down its possible to add a hygroscopic material around your antenna. Bentolit (white cat sand) is very hygroscopic and will lower the radiation resistance in the counter poise.

You can also make a trap somewhere along the antenna. The trap can be tuned to about 10Mhz because this will be almost at the center between 20m and 40m. The length of the lower section of the antenna should be slightly under the reconance at the low end of the band 14Mhz (5.095m or 16.714ft)
https://www.qsl.net/on7eq/projects/coaxtraps.htm
http://www.arrl.org/hf-vertical

Another option is to put a thin parallel wire along the main radiator. The parallel radiator is kept at some distance 10-15cm from the main radiator by insulating spacers.
The parallel radiator is tuned by adjusting the length. When tuning the short radiator keep the long radiator disconnected but as it is suppose to be installed
The trap is placed between the main radiator and the parallel radiator. Feed point is on the short radiator.
https://www.qsl.net/g4aon/vertical/
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WA7ARK

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RE: To what frequency do I tune my antenna?
« Reply #4 on: July 11, 2019, 08:08:17 PM »

The entire premise of using a remote tuner is that you do not have to "trim" the antenna. The only exception is that if the length of the vertical plus horizontal happens to be one-half wavelength on any frequency of interest, then you may arc over the tuner and damage it.

Any vertical (or inverted-L) is only as good as its radial field (counterpoise), because half of the antenna is the counterpoise, as said by LA9XNA...

Horizontal half-wave antennas (dipole or end-fed) have always worked better for me than any vertical or inverted-L.
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Mike, WA7ARK

KD0REQ

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RE: To what frequency do I tune my antenna?
« Reply #5 on: July 12, 2019, 08:21:38 AM »

assuming you only work one mode, trim to the middle of that band plan.

if you don't have a broad-tuned antenna like a dipole, and have something with a narrow match like a mag loop, you have to diddle it every time you turn the dial.

if all you care about is the radio not safing out for being too mismatched, and you're not fixated on the most amps in the antenna, get an autotuner. all tuners protect the radio at the expense of buffering reflected power inside as heat. tuners are not linear amplifiers. they just make an antenna look matched, and do the suffering themselves. hey, it's hamming. it's not like you are an ad-funded commercial broadcaster wild to extend the A coverage into Dismal Junction.
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NO2A

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RE: To what frequency do I tune my antenna?
« Reply #6 on: July 17, 2019, 09:34:39 AM »

I've always had better luck tuning an antenna to the lowest part of the band,then an autotuner will make up the difference on the higher part of the band(s). If you do the opposite and tune the antenna to the middle of a band,and use a tuner for the lower part of the band, you'll get higher voltages. That may be too much for your tuner to handle, unless you have a high end manual tuner. I would still tune it for the lower part of the band.
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G4AON

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RE: To what frequency do I tune my antenna?
« Reply #7 on: August 10, 2019, 12:59:29 AM »

I would opt to make the antenna nowhere near a half wavelength on any band of interest. The feed impedance will be very high and could cause arcing over in the remote tuner.

SGC have a very good stealth antenna guide on their web site covering restricted antennas and remote tuners... they have been producing remote tuners for a long time, mainly for commercial use.

https://www.sgcworld.com/Publications/Books/stealthbook.pdf

73 Dave
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KH6AQ

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RE: To what frequency do I tune my antenna?
« Reply #8 on: August 14, 2019, 10:40:20 AM »


I live in a deed restricted neighborhood and managed to get permission to construct a vertical antenna. At the advice  of a Ham-friend of mine, I converted the vertical a few years later to a Inverted L, of which one of the sides is the original vertical (a alluminume 21 ft pole.) and for the other side I attached to the top a 22 gauge wire, which runs to a tree in the back of the property. This arrangement is tuned to the top of the 80m band, and works quite well with a 1.5 to 1 SWR by it self.
The question is, to which frequency shall I tune the antenna if now my main interests are changed from the 80m to the 40, 20 and 15 meter bands?  In anticipation of expanding the coverage range of the antenna, I am feeding the antenna now with a coax cable through an MFJ-927 remote tuner, which is located abt. 3ft from the base of the antenna.

If the MFJ-927 tunes the present antenna on 40, 20 and 15 meters you're good to go.
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AC2RY

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RE: To what frequency do I tune my antenna?
« Reply #9 on: August 14, 2019, 01:22:55 PM »


I live in a deed restricted neighborhood and managed to get permission to construct a vertical antenna. At the advice  of a Ham-friend of mine, I converted the vertical a few years later to a Inverted L, of which one of the sides is the original vertical (a alluminume 21 ft pole.) and for the other side I attached to the top a 22 gauge wire, which runs to a tree in the back of the property. This arrangement is tuned to the top of the 80m band, and works quite well with a 1.5 to 1 SWR by it self.
The question is, to which frequency shall I tune the antenna if now my main interests are changed from the 80m to the 40, 20 and 15 meter bands?  In anticipation of expanding the coverage range of the antenna, I am feeding the antenna now with a coax cable through an MFJ-927 remote tuner, which is located abt. 3ft from the base of the antenna.
(Also, besides the MFJ-927 Remote Tuner, some of the  radios I use have a build-in tuner, so if needed, I have a choice which one to use for different bands.)
Any suggestions are appreciated.

33 and 43 feet are two standard heights for multiband vertical with remote tuner. Just have antenna of that height and let tuner do the rest. You may try to add choke (unun) either between tuner and antenna or feed line and tuner.
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W9IQ

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RE: To what frequency do I tune my antenna?
« Reply #10 on: August 14, 2019, 02:22:34 PM »

33 and 43 feet are two standard heights for multiband vertical with remote tuner. Just have antenna of that height and let tuner do the rest. You may try to add choke (unun) either between tuner and antenna or feed line and tuner.

Please note that the unun, with a common ground connection, does not function as a "choke". It tends to have the opposite effect of promoting common mode current in the right circumstances.

The device of choice should be a 1:1 current balun - also called a choking balun. The better wide band designs tend to be based on one or more toroidal ferrite cores. Avoid the ugly baluns (coax wound in a loop) for a broadband antenna application.

- Glenn W9IQ
« Last Edit: August 14, 2019, 02:31:30 PM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W1AJO

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RE: To what frequency do I tune my antenna?
« Reply #11 on: August 15, 2019, 01:48:57 PM »

Do you have an antenna analyzer?  I finally bought one 6 years ago and it should have been the first HAM item I bought.  The analyzer will tell you where the antenna is resonant.   I use an MFJ 259B and now all my antennas work a whole lot better.  The 259B has been replaced with the 259C.  Best $300 you will spend.

https://www.mfjenterprises.com/Product.php?productid=MFJ-259C

I take it to Field Day and it greatly speeds up the time to get an antenna tuned to the frequency needed.
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