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Author Topic: Tuner at the base for G5RV 80/40 Meters  (Read 1594 times)
KF7NUA
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Posts: 153




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« on: October 12, 2013, 06:33:11 AM »

Is it worth the effort to put a auto tuner outside at the base of the mast for a G5RV, my only use for the G5 is for 80 and 40m?
Also I am having difficulty getting it up as a flat top, the best I can do as of today will be 35ft at the apex and 17 to 20ft on the ends.
I am concerned about this after reading many threads on never using a G5 has an inverted V.

As a suggestion would you recommend any other antenna for 80/40 instead of the G5, but please do not suggest 1/2 wave dipoles for each as I do not have the room for the 80m version.
Thank you
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W5DXP
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« Reply #1 on: October 12, 2013, 07:23:38 AM »

Is it worth the effort to put a auto tuner outside at the base of the mast for a G5RV, my only use for the G5 is for 80 and 40m?

What kind of coax are you using and how long is the coax? I doubt that an autotuner will have much effect on those two bands since they are already two of the G5RV's best bands.

Quote
I am concerned about this after reading many threads on never using a G5 has an inverted V.

For 80m and 40m, the inv-V configuration is OK because the maximum antenna currents are at the feedpoint which is the highest point. It is on the higher frequency bands where the inv-V has problems with the current maximum points being lower than the center of the antenna.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KF7NUA
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Posts: 153




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« Reply #2 on: October 12, 2013, 08:15:38 AM »

Quote
What kind of coax are you using and how long is the coax? I doubt that an autotuner will have much effect on those two bands since they are already two of the G5RV's best bands.

I have the option to use LMR400, RG213U, and RG8x, the coax run will about 75ft.

Quote
For 80m and 40m, the inv-V configuration is OK because the maximum antenna currents are at the feedpoint which is the highest point. It is on the higher frequency bands where the inv-V has problems with the current maximum points being lower than the center of the antenna.

This is good news, thank you

Because of it being in an Inverted V and at a lower than ideal height should I be concerned with orienting the antenna to favor the NE and E part of the country? I am in the SW, in lower part of Arizona and the easiest position I can install it is broadside to NW & SE.
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W5DXP
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« Reply #3 on: October 12, 2013, 09:20:11 AM »

I have the option to use LMR400, RG213U, and RG8x, the coax run will about 75ft.

If cost is no object, I would recommend either LMR400 or RG213. Hope you realize that you will need a good tuner.

Quote
Quote
For 80m and 40m, the inv-V configuration is OK because the maximum antenna currents are at the feedpoint which is the highest point. It is on the higher frequency bands where the inv-V has problems with the current maximum points being lower than the center of the antenna.

This is good news, thank you

I'm sorry, I misspoke while thinking about radiation patterns. Since the G5RV is longer than 1/2WL on 40m, the current maximums on 40m will be about 34' away from the feedpoint which is probably not enough to notice - just wanted to be accurate.

The radiation on 80m and 40m is broadside so put it broadside to wherever you want your radiation to go. (But why would you want to talk to a bunch of yankees who talk funny and don't know what I mean when I say, "Ahh reckon Ahh'm gonna amble over yonder directly"?)Smiley
« Last Edit: October 12, 2013, 09:25:22 AM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K7KBN
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Posts: 2813




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« Reply #4 on: October 12, 2013, 05:02:49 PM »

If that's as high as you can get it, you won't be seeing too much directionality on 40 and 80 (and probably other bands).  It'll be pretty omnidirectional.
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73
Pat K7KBN
CWO4 USNR Ret.
W5DXP
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« Reply #5 on: October 13, 2013, 07:35:50 AM »

It'll be pretty omnidirectional.

You're right - at an elevation angle of 45 deg, there's a 1dB difference on 80m and a 3dB difference on 40m. 3dB (double the power) might occasionally be noticeable.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KB6HRT
Member

Posts: 113




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« Reply #6 on: October 13, 2013, 09:52:45 AM »

Been using the G5RV for about 7 years now, the reason for using it is at my location it worked out best for what I was doing with it. Did direct comparisons A/B testing with a straight 80m dipole, Maypole, DB a coiled dipoles that were single banded an multi banded, why the G5RV, because it was [quieter on receiver] so with the right radio can hear more an with the proper amount of power can be heard well. Most radios built in the last 20 years have more than enough built in gain to take care of insertion loss of meters, amps, an tuners with out a problem an still reach out far enough to hear 97% of all signals out there. Found a long time ago that 100' of new coax RG-8, RG213 or even RG-8X will do the job nicely for the G5RV, then if you want to tune your G5RV for a low SWR on 40m or 80m you have a little extra coax to play with to find the null for your frequncy of choice. Using the tuner in my Yaesu VL-1000 the SWR is less than 3 to 1 on 75m-40m-20m-15m- ?m an the low part of 10m where I do talking, also have a LDG PRO 1000 tuner where it can be used with the same G5RV for 10-80m. A Maypole will give a better 360 Deg pattern on 80-40m but you will have less gain on 75m in the direction I want to talk most. For most of us HAMS there is so much to learned, has taken me most of my life to learn what I know, by reading, trying different things, then figuring out what works, by doing A/B testing then making the antenna strong and fast so it will last a long time, for me my fascination with radio is the same today as it was when I was 8 an built my first Crystal set, now thats a BLESSING! Hope I live a long life, because I have so much more to learn in HAM RADIO!..........73s.........KB6HRT Smiley
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