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Author Topic: Basic question re HF beam antennas  (Read 2180 times)
2E0ILY
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Posts: 131




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« on: May 23, 2012, 02:05:13 AM »

Forgive  the elemental (sorry.... Smiley) question, but I am thinking of putting up a sixty foot tower and getting a SteppIR 3 element beam for it. Now, I have zero experience of beams at HF, will I only be able to receive and Tx in the direction it's pointing, or do they have useful reverse and side efficiency, too? Thanks.
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Best regards, Chris Wilson.
KC4MOP
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Posts: 731




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« Reply #1 on: May 23, 2012, 03:36:22 AM »

Never a problem on eHam. This is a very nice forum and very little flaming.
60 feet is probably the best height for an HF beam. I envy you!!!
Now the SteppIr is a very expensive antenna. I would look at any reviews about it before purchasing. And remember that Internet type reviews have to be taken carefully. If you read enough of them, you pick out the folks that are acting like they just bought the best antenna ever made.
I do not know of the reliability of a SteppIr with motors and control circuits 60 feet high.
Cushcraft is in the questionable area also.
Mosley and one or two other long-time makers might be a better antenna. There were some threads about other antenna manufacturers elsewhere......
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K2MK
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Posts: 391




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« Reply #2 on: May 23, 2012, 04:13:24 AM »

All HF beams are optimized for the direction they are pointing. But it's a lobe, not an arrow point. So you will still easily work stations to which you are not specifically pointed. SteppIR has a unique feature unavailable to any other manufacturer of being able to electronically modify the antenna to quickly reverse direction (180 mode) or to lower its gain and operate in opposite directions (BI mode) without actually rotating the antenna.

SteppIR antennas with their motorized components "could" require more maintenance than others that are strictly aluminum so it is highly recommended that you have a convenient way of accessing the antenna. This generally requires a crank down tower with a tilt-over capability.

73,
Mike K2MK
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K3VAT
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Posts: 704




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« Reply #3 on: May 23, 2012, 10:37:30 AM »

All HF beams are optimized for the direction they are pointing. ... SteppIR has a unique feature unavailable to any other manufacturer of being able to electronically modify the antenna to quickly reverse direction (180 mode) ... 73, Mike K2MK

Not true Mike.  N6BT Antenna Systems (Founder of Force12) makes a 180 deg switchable (bi-directional) 2-el HF yagi.  See http://n6bt.com/n6bt-Q52-p1-1.htm.  73, Rich, K3VAT

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AD4U
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Posts: 2156




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« Reply #4 on: May 23, 2012, 10:39:55 AM »

SIMPLY put - a HF beam antenna sends and receives most RF energy in one direction (gain).  In all other directions the RF energy is attenuated (front to back ratio and front to side ratio) with respect to the gain end of the beam.

In order to effectively use a HF beam in all directions it will have to be rotated so the front end (gain end) of the beam is pointed toward the station you want to hear or talk to.  Remember that the gain pattern of a typical three element tri-band HF beam antenna is rather broad and you do not have to point the beam precisely at the station you want to talk to.  The radiation pattern of any typical theee element tri-band HF beam is not like that of a flashlight.

This is not to suggest that you cannot hear stations in directions off the side and rear of the beam.  You can hear them if they are stong enough, but the signal will be greatly attenuated from what you would hear if the HF beam were pointed directly at them.

Dick  AD4U
« Last Edit: May 23, 2012, 03:27:29 PM by AD4U » Logged
K2MK
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Posts: 391




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« Reply #5 on: May 23, 2012, 11:28:27 AM »

All HF beams are optimized for the direction they are pointing. ... SteppIR has a unique feature unavailable to any other manufacturer of being able to electronically modify the antenna to quickly reverse direction (180 mode) ... 73, Mike K2MK

Not true Mike.  N6BT Antenna Systems (Founder of Force12) makes a 180 deg switchable (bi-directional) 2-el HF yagi.  See http://n6bt.com/n6bt-Q52-p1-1.htm.  73, Rich, K3VAT

I stand corrected.

73,
Mike K2MK
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N3DF
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Posts: 252




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« Reply #6 on: May 23, 2012, 12:09:26 PM »

SIMPLY put - a HF beam antenna sends and receives most RF energy in one direction (gain).  In all other directions the RF energy is attenuated (front to back and front to side) with respect to the gain end of the beam.

In order to effectively use a HF beam it will have to be rotated so the front end (gain end) of the beam is pointed toward the station you want to hear or talk to.  Remember that the gain pattern of a HF beam antenna is rather broad and you do not have to point the beam precisely at the station you want to talk to.  The radiation pattern of any typical HF beam is not like that of a flashlight.

This is not to suggest that you cannot hear stations in directions off the side and rear of the beam.  You can hear them if they are stong enough, but the signal will be greatly attenuated from what you would hear if the HF beam were pointed directly at them.

Dick  AD4U

Incidentally, this is usually regarded as a good feature of directional antennas.  If you're eager to work a weak DX station you want to attenuate the signals on the same or adjacent frequencies from stations in other directions. 
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Neil N3DF
WB6BYU
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Posts: 13112




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« Reply #7 on: May 23, 2012, 12:34:23 PM »

Many companies and/or designers publish radiation patterns for their antennas.
For example, here is a 3-element yagi from DK7ZB:

http://www.mydarc.de/dk7zb/3-Ele-Kurzwelle/10m-28Ohm.htm

If you scroll down you'll see a plot that looks somewhat like a yellow scollop shell
outline on a brown background:  that shows that radiation is maximum across a fairly
wide forward lobe (about +/- 30 degrees from the way the antenna is pointed), with
relatively little radiation off the sides and back (the lower part of the diagram.)

That's a fairly typical radiation pattern for a 3-element yagi.  You can often get
higher gain at the expense of more radiation to the rear.  Adding elements will
make the main lobe narrower, but you'll still hear a lot of signals from +/- 60 degrees
from the main beam, as well as some off the rear if they are strong enough.
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WA4FNG
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Posts: 162




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« Reply #8 on: May 23, 2012, 03:31:51 PM »

Basil,
Am I to understand you plan to put that antenna on a tower -without- a rotator? That seems like a lot of work and expense to not be able to turn it.
73 Milt
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