Author Topic: All band no tuner needed antenna (This is and endfed antenna)  (Read 8208 times)

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Lamewolf

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All band no tuner needed antenna (This is and endfed antenna)
« on: October 15, 2014, 12:26:04 PM »
First let me give an intro.  I'm a 58 year old geezer from Southern Ohio and been licensed since 1995 and fooling with radios of some kind since I was about 9 years old.  I love building and experimenting with radios, equipment, and antennas.  This is my first post here, and I'll try to answer any questions about it as I get time to do so.  With that:

Anyone here ever experimented with a Vertical Half Rombic antenna ?  Its basically and end fed antenna that is fed with a 9:1 unun on one end and has a 450 ohm non inductive resistor termination on the other end and can cover 160 thru 10 meters without a tuner and is configured like an inverted V.  Getting the materials together to build one, once I get it together and tested will post the results here.  Actually I have it built, just been too rainy to get outside and set it up and test it.

This antenna requires no tuner for all band operation and can be setup quick in the field.  Needs only one support too - very easy to setup.

Hers a link to a pdf with the info I am using to build mine: http://www.korpi.biz/hr.pdf
« Last Edit: October 15, 2014, 12:38:53 PM by Lamewolf »

unseenone

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #1 on: October 15, 2014, 02:52:45 PM »
Welcome

It sounds interesting, and a similar concept to the Chameleon antennas, though they require a tuner.

How efficient would this be when completed?

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #2 on: October 15, 2014, 03:13:16 PM »
Welcome

It sounds interesting, and a similar concept to the Chameleon antennas, though they require a tuner.

How efficient would this be when completed?

Efficiency depends on the band in use and the length of the wire used between the balun and terminator.  In actuality, the efficiency figures can show fairly low due to the attenuating factor of the termination resistor.  With any "broadband" antenna, you will have losses that lowers the efficiency, so efficiency isn't what this antenna is really about.  The main idea is to be able to use it on all bands without a tuner - just a quick setup, field expedient antenna.  But, on the higher bands, or with longer lengths of wire the efficiency can be increased with this one.  When you think of efficiency of an antenna system, think of them as a teeter totter.  In other words, as bandwidth goes up, efficiency goes down and vice versa - a narrow band antenna will be much more efficient any day, but you will be restricted to the main design frequency the antenna is cut for.  Now to get to the meat of your question, the efficiency of this design can be as little as 1% or less and as good as 50% or more depending on the frequency verses length ratio.  But remember, some folks have made contacts over hundreds of miles using nothing more for the antenna than a 50 ohm dummy load !

spacecase0

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #3 on: October 15, 2014, 08:57:53 PM »
I have wanted to build one for years,
getting the 450 ohm non inductive resistor in any power range close to required seems to be the trick.
receive versions are easy as you don't need much power rating on your resistor

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #4 on: October 16, 2014, 06:28:21 AM »
I have wanted to build one for years,
getting the 450 ohm non inductive resistor in any power range close to required seems to be the trick.
receive versions are easy as you don't need much power rating on your resistor

You can use a 50 ohm/50 watt resistor but feed the resistor with another 9:1 unun to convert it to 450 ohms.  Or just use any 50 ohm dummy load fed with a 9:1 unun.  And by the way, the resistor only needs to be rated about half the power of the transmitter's output.  So a 50 watt resistor will work for a 100 watt transmitter.   I am using a 50 ohm/50 watt non inductive resistor connected to a 9:1 unun to upcovert it to 450 ohms.  I ordered the resistor from Mouser Electronics for around 8 bucks.  But again, if you use a 50 ohm resistor, fed with the unun, you can use an ordinary 50 ohm dummy load.  An old Heathkit Cantenna dummy load will handle up to 1500 watts ! :)
« Last Edit: October 16, 2014, 10:56:40 AM by Lamewolf »

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #5 on: October 16, 2014, 11:56:31 AM »
Here's a pdf of the Vertical Half Rombic that shows how to use the 50 ohm resistor fed by a 9:1 unun along with some efficiency figures of the various lengths verses frequency.

BTPost

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #6 on: October 17, 2014, 01:20:47 PM »
What you get is a very nice Radiating Dummy Load... and it radiates about as well.... There was an outfit, that used to advertise in QST, that sold a dipole Center Appliance that was 50 Ohms, across the HF Spectrum, and you could attach ANY length of wire, to each side. They would never say what was inside it, but someone cut one in half and it was a BIG 50 Ohm 100 Watt Resistor. Worked on the same principal. Equally BAD Radiation Efficiency, on ALL Bands.....  Just say'en...
Bruce in alaska AL7AQ

spacecase0

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #7 on: October 18, 2014, 12:44:19 AM »
What you get is a very nice Radiating Dummy Load... and it radiates about as well.... There was an outfit, that used to advertise in QST, that sold a dipole Center Appliance that was 50 Ohms, across the HF Spectrum, and you could attach ANY length of wire, to each side. They would never say what was inside it, but someone cut one in half and it was a BIG 50 Ohm 100 Watt Resistor. Worked on the same principal. Equally BAD Radiation Efficiency, on ALL Bands.....  Just say'en...
at least the Rombic antenna has a chance to radiate before it gets to the resistor,
not that it helps to much

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #8 on: October 18, 2014, 07:17:01 AM »
at least the Rombic antenna has a chance to radiate before it gets to the resistor,
not that it helps to much

That's true, and remember, some folks have made contacts over thousands of miles using nothing but a dummy load and even light bulbs !  Another local ham here and I that live about 12 miles apart used to work each other on our dummy loads quite often.  Signals were very weak, but there was no noise at all !  Also, for an experiment once I installed a T fitting to the top of my old Heathkit Cantenna dummy load with the radio connected to one side of the T and my outside antenna connected to the other and made contacts all over the country on 20 and 40 meters with it. So, even though the resistor is absorbing some of the power, some of the RF does get radiated.

BTPost

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #9 on: October 18, 2014, 12:44:14 PM »
Yep, absolutely right... When the band is open, you can make a contact with a "Wet Noodle" antenna, using 10 watts... HOWEVER if the band is closed, you can call and call al day long, with 1Kw, and a Quad Stack of MonoBanders at 120 Ft, and still not get a contact.... band conditions far outweigh and Antenna/Power considerations, ALWAYS.... This is why ALE was invented, for Outfits that use HF for Mandatory Comm links that MUST work, 24/7/365.... As the bands change for Point to Point Comms the Radio Gear automatically switch Frequencies, and Power Levels to keep the Link open, and up.... I used to maintain one such link that used an RF Comm Exciter/Receiver, driving a 5Kw Gates Amp, into a 3-30Mhz Log Periodic Array, that ran a 5000 Mile link between what is now FEMA Sites. Sure wish I had all that Gear, in my shack, these days.....
Bruce in alaska AL7AQ

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #10 on: October 20, 2014, 06:25:20 AM »
Yep, absolutely right... When the band is open, you can make a contact with a "Wet Noodle" antenna, using 10 watts... HOWEVER if the band is closed, you can call and call al day long, with 1Kw, and a Quad Stack of MonoBanders at 120 Ft, and still not get a contact.... band conditions far outweigh and Antenna/Power considerations, ALWAYS.... This is why ALE was invented, for Outfits that use HF for Mandatory Comm links that MUST work, 24/7/365.... As the bands change for Point to Point Comms the Radio Gear automatically switch Frequencies, and Power Levels to keep the Link open, and up.... I used to maintain one such link that used an RF Comm Exciter/Receiver, driving a 5Kw Gates Amp, into a 3-30Mhz Log Periodic Array, that ran a 5000 Mile link between what is now FEMA Sites. Sure wish I had all that Gear, in my shack, these days.....

Yes, this Vertical Half Rombic is used a lot for field ALE operations where a frequency agile antenna is need.  Finally got a chance to stet it up yesterday afternoon and try it out and it works faily well running only 5 watts from my Yaesu FT-817 SSB.  On the MFJ 259B it shows below 2:1 on most bands except 30 meters where its about a 2.5:1 but on 160, 80, 60, 40, and 20 meters the needle barely moves.  Next time I tri it I will be running about 30 watts from and old Yaesu FT747GX that I have internally set to a max output of 30 watts to use as a field rig.  I set the power down to conserve batteries and changed all the dial and meter lamps to LEDs to save a little current - shaved a couple hundred mA that way.  But anyway, it worked well at 5 watts and I made several contacts with it on 17, 20, 40, and 75 meters and everyone was amazed that I was running only 5 watts !

spacecase0

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #11 on: October 20, 2014, 03:36:03 PM »
just so you know,
at a 2:1 SWR the FT817 backs off power down to about 3W when it is set to 5W

so I always use a tuner to match down to 1:1 for the 817 so that it will not back off on power when I have a less than absolutely perfect antenna

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #12 on: October 21, 2014, 06:16:27 AM »
just so you know,
at a 2:1 SWR the FT817 backs off power down to about 3W when it is set to 5W

so I always use a tuner to match down to 1:1 for the 817 so that it will not back off on power when I have a less than absolutely perfect antenna

Yeah, I know it backs power down to protect the rig but I wanted to see how the antenna would work without a tuner which was the core of the test in building this antenna.  It will probably not be used with the 817 most times as it gets paired with an LDG Z11 Pro 2, a homebrew 4:1/1:1 switchable balun, and two 88' lengths of wire that wound on  Coleman camping clothesline reels. One wire used for the antenna and the other is a counterpoise.  This antenna will be paired with an old Yaesu FT-757GX that I have set internally to 30 watts but is fully capable of 100 watts.  With it set to 30 watts I'll have ample power for field operations and a 2:1 swr will not bother this old rig.  Anyway, I figured if this antenna works well with the flea power of the 817, it will work great at 30 watts !

Captain Crunch

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #13 on: October 24, 2014, 05:36:55 PM »
Those type of antennas are heavily used by the military. Sure you'll lose some efficiency with the resistor but the idea is to get the transmission out. Terminated antenna can be very efficient, directional and easy to use.

Someone was talking about Chameleon Antenna earlier: They're indeed manufacturing an EXCELLENT civilian version of the military antenna system:



http://chameleonantenna.com/PORTABLE%20ANTENNA/CHA%20TD/CHA%20TD.html

http://chameleonantenna.com/resources/CHATD-Operator-Manual-1.4.pdf

I saw that antenna system in action during the Field Day 2014. The whole kit is top notch!

Like most antennas, efficiency gets lower at lower frequencies. The antenna operator told me that this antenna system was perfect for ALE.

CC

Lamewolf

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Re: All band no tuner needed antenna (This is and endfed antenna)
« Reply #14 on: October 27, 2014, 01:16:33 PM »
Those type of antennas are heavily used by the military. Sure you'll lose some efficiency with the resistor but the idea is to get the transmission out. Terminated antenna can be very efficient, directional and easy to use.

Someone was talking about Chameleon Antenna earlier: They're indeed manufacturing an EXCELLENT civilian version of the military antenna system:



http://chameleonantenna.com/PORTABLE%20ANTENNA/CHA%20TD/CHA%20TD.html

http://chameleonantenna.com/resources/CHATD-Operator-Manual-1.4.pdf

I saw that antenna system in action during the Field Day 2014. The whole kit is top notch!

Like most antennas, efficiency gets lower at lower frequencies. The antenna operator told me that this antenna system was perfect for ALE.

CC

At $479 I think I'll pass on the Chameleon !  I only have about $25 in mine and it works great........