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Author Topic: Need a better 80 meter antenna  (Read 9191 times)
N7GCO
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Posts: 144




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« on: October 28, 2013, 11:50:58 PM »

I have a full size 80 meter dipole up 75'. It is tuned properly for SSB with near 50 ohms. I am not at all getting the results I would like on DX.

I would use a full size 1/4 wave vertical, but I have a small lot, so very little room to run radials and they could not be the proper length. I have thought about running elevated radials (for I have read you can get by with less), but again I can't find any way to do it the correct lengths from any location I could put the antenna.

Any suggestions on what antenna to use to get better DX?

PS. I have 10-40 meters covered with a SteppIR antenna on a 45' tower than does excellent.
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KQ6Q
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Posts: 978




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« Reply #1 on: October 29, 2013, 12:51:16 AM »

right now the sunspots are good, the higher bands are open. Expect better results on 80m when the higher bands are NOT so good.
You might try a less than perfect vertical - even a sloper with some loading from your tower...
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M6GOM
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Posts: 914




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« Reply #2 on: October 29, 2013, 03:42:15 AM »

The vertical will work. There is no "proper length" for ground level radials as the ground detunes them. Many short ones are better than a few long ones so put in as many as you can as long as you can. The difference between the most optimal and what you can do will be maybe a S point.
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N3HEE
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Posts: 117




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« Reply #3 on: October 29, 2013, 03:59:34 AM »

I am on a small quarter acre lot.  I use a resonant inverted L for transmit on 80.  The antenna is 33 feet vertical and about 37 feet horizontal.  I have about 1000 feet of radial wire randomly laid out in different lengths wherever I could run them.  I add more as I get time.  The antenna is connected to the feed point of my 160 meter inverted L.  The antenna is probably far from optimum but works surprising well.  I can work almost any DX I can hear.  I use a separate 3 element phased vertical array for a RX antenna.  That makes all the difference for RX on the low bands.  -Joe N3HEE
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W1VT
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Posts: 829




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« Reply #4 on: October 29, 2013, 05:37:12 AM »

I have an 80 meter vertical with elevated radials that does very well--I easily got my 80M DXCC in half a season after putting it up in the middle of a New England winter.  Shocked  

My radials are only 55 long--dictated by the size of my back yard.  You want symmetry, so that the current divides more or less equally into them.  This isn't so important with lots of ground mounted radials, but is important if you want to get by with just a few of them.

A top loaded vertical is superior to an Inverted L--it will have a overhead null that will make it easier to hear the DX stations.  My location is suprisingly quiet for the suburbs of Hartford--I've worked lots of Pacific stations with the vertical and 100 watts--got 5W1SA tuning around one morning.  Grin

Zack Lau W1VT
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AD4U
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Posts: 2166




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« Reply #5 on: October 29, 2013, 06:05:12 AM »

Even though your 80M dipole is up 75 feet, it is only around 1/4 wavelength high.  At this electrical heighth much of your radiated signal goes "up" which is good for local and medium distance DX contacts, not "out" which is better for long range DX. 

I don't know what kind of performance you are expecting on 80M, but typically distant DX signals on 80M are usually rather weak (very weak) when compared to the same DX signals on the higher bands.  Most long range DX on the lower bands is near the noise level.  Only rarely do 80M DX signals from 10,000 miles away come in "arm chair copy" at S9+20.

If you are not happy with the 80M dipole, you could try a 1/4 vertical or an L.  Both require radials.  Ideally radials should be the "proper" length, but IMO it is much more important to have a lot of shorter radials than a few long ones of the "proper" length.  If you install a 1/4 wave vertical, keep the dipole for receive.  Most verticals pick up a lot more "noise" than horizontal antennas.  DX signals picked up on an 80M vertical may be stronger than on a dipole, but often the noise picked up by the vertical is even stronger than the signal.  Often the DX signal on the dipole may be 2-3 S units less than on the vertical, but the noise may be 5-6 S unitl less.  S/N often makes or breaks low band contacts. 

When trying to work DX on the lower bands, IMO running the legal limit is important.  When running 1500 watts I can usually work any DX station I can hear on 160M and 80M.  That is not the case when running 100W.  I am not a DX hound but I have worked around 275 DX countries on 80M with just casual operating, and the best 80M antenna I ever used was an inverted V with the apex at 80 feet and the ends much lower.

Dick  AD4U
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K1DA
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Posts: 507




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« Reply #6 on: October 29, 2013, 08:12:59 AM »

Try CW.
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WB6BYU
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Posts: 13283




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« Reply #7 on: October 29, 2013, 10:25:40 AM »

Short the coax at ground level and feed your dipole+coax against ground
as a vertical using a tuner at the base.  Impedance will be somewhat high,
which means you don't need a huge radial field for good efficiency.
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KU3X
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Posts: 142




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« Reply #8 on: November 01, 2013, 05:30:19 AM »

I could not agree more that an inverted L or a 1/4 wave vertical with a massive ground radial system would be one of the best choices, but......consider a full size Delta Loop fed either in the bottom corner or 1/4 wave down from the apex.
I am in PA, live 100 feet below average terrain and have worked VK’s long path on 80 meters CW and SSB from this location. I had to run 1500 watts to do, but did it.
When I worked the VK’s, I used a shortened Delta Loop that was only 80% of a full size Delta Loop.  I now use a full size Delta Loop fed in the bottom corner and the base of the antenna is only 10 feet above the ground.

Barry
www.ku3x.net
.
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N1UK
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Posts: 1457




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« Reply #9 on: November 01, 2013, 10:27:50 AM »

Take a look at the Alpha Delta half wave sloper. I put one up and have been very pleased with it. I have modified mine by adding extra wires and on 80m it is resonant from 3.5 to 3.85.

It puts a loud signal into Europe on 80m. I have worked Europe on 160m with it as well. It was recommended to me by a friend. I was dubious but glad that I installed it on my tower.


http://www.dxengineering.com/parts/alf-dx-a/


Something for you to consider. Mine now covers 160, 80, 60 and 30m



Mark N1UK
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NV2A
Member

Posts: 115




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« Reply #10 on: November 08, 2013, 05:40:00 PM »

Don't seek perfection in an installation.  Just do the best you can and see how it plays.  Most of what we read on antenna design is for an ideal lot size devoid of trees and buildings and near salt water!!  I have a HFv9 Butternut with 32 30 foot radials and snagged Hawaii two mornings ago with 100 watts.  It should play well but it seems to do okay.
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K3VAT
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Posts: 715




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« Reply #11 on: November 09, 2013, 08:42:00 AM »

I have a full size 80 meter dipole up 75'. It is tuned properly for SSB with near 50 ohms. I am not at all getting the results I would like on DX.
... <snip> ... Any suggestions on what antenna to use to get better DX? PS. I have 10-40 meters covered with a SteppIR antenna on a 45' tower than does excellent.

If the 45' tower is located where you could have at least a 180 degree coverage with a radial field, then what I would consider extending the mast by adding a section of aluminum or fiberglass (with wire inside or outside), bonded to the mast.  The Steppir will add only a bit of top loading so you'll still need the extension - but you'll have to experiment on finding the proper length of the add-on.  Then just shunt feed the tower and as many have pointed out install as many ground radials as practical.  Don't worry too much about covering 360 degs (see the article by N6LF on 'partial radial fields' http://www.rudys.typepad.com/.

GL, 73, Rich, K3VAT
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NO9E
Member

Posts: 405




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« Reply #12 on: November 09, 2013, 01:51:03 PM »

I have a flattop for 80m fed by ladderline at about 70ft. Also full size vertical to a tree with 8 tuned elevated radials.  With a dipole I can work almost anything on 80m. The vertical is usually 10db down including DX, except in a direction where the dipole has a null.

I also have a shortened 80m dipole with a coil at 50ft. This dipole is at least 5 db down from the flattop.

Ignacy, NO9E
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AA5WG
Member

Posts: 497




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« Reply #13 on: November 09, 2013, 02:50:17 PM »

NO9E has the best idea.  Feed the 80 meter dipole with ladder line.  I suggest using a link antenna coupler with your
ladder line and then you will have flexibility in tuning your antenna system along with high efficiency.  Home brew ladder line is by far the most efficient feed system available.  The commercial stuff gets has much loss when it gets wet.

73,
Chuck
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KB6HRT
Member

Posts: 110




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« Reply #14 on: November 10, 2013, 07:41:21 AM »

My take,
 You can take it with a grain of salt, but have 4 antennas on a small lot an all have been optimized for the best results over the past 7 years, a 43' vertical with 3000' of radiates, a tuned 20-40-80m dipole a G5RV and a 6-20 beam and can switch
between them all to 4 different radios an A/B the receives. The beam is at 36' an the G5RV at 36' and the 20-40-80m tuned dipole is at 38' to the apex, changing the apex on the G5RV from 36 to 38' made a negative difference on how the G5RV received and also worked on 40m when using my small 500w amplifier. With condition changing all the time can pick the antenna that works best for the contact I am trying to make, on the upper bands the beam winds 85-90% of the time, for Gray Line the vertical on 80m pull in signals in well a lot of the time, but the G5RV give me the best signal to noise ratio an hears very well to about 3000' miles on 75m at night but so does the vertical but with more noise, about 15% of the time my 20-40-75m trapped dipole will come out on top! I don't have the technical knowledge of a lot of my brother HAMS any more but when I did this is what I came up with that worked best on my 6500'
for me, hope this is of value to ya.............KB6HRT
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