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Author Topic: Phase Verticals - Two Bands  (Read 1039 times)
K4MIA
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Posts: 7




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« on: March 22, 2010, 09:34:45 AM »

Hello,
I am going to do my 1st attempt at phasing verticals. I have 2 Butternut HF2V verticals. I would like to have the phasing work on both bands. If I have them 66 feet apart can I phase them 1/4 wave on 80 meters and 1/2 wave on 40 meters. I know that it would be better phasing them on only one band. But could I do it without distorting the radiation patterns to bad. Get a good SWR in the phone DX windows and do without a tuner? Or if not, can it be setup for 80 and using tuner get good results on 40? I have done reading in ARRL Antenna Book, Low-Band DXing and Internet sights. But really could not find an answer.

Tnx and 73 Mike K4MIA
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WB6BYU
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Posts: 13149




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« Reply #1 on: March 22, 2010, 09:40:47 AM »

Do you want them to radiate in the same direction on both bands?
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WX7G
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Posts: 5975




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« Reply #2 on: March 22, 2010, 10:10:35 AM »

Yes it will work and quite well. Sounds like a fun project.

If used with a 90 deg difference on 80 meters it will always have a 180 deg difference on 40 meters. That makes the pattern end-fire. Add 180 deg to one antenna to bring them in phase and now it's a broad side on 40 meters.

On 40 meters the antenna interaction is small and the feedpoint impedance remains high. On 80 meters there is much interaction and there will be increased GND current. So, a good ground system is needed or the phase array gain is negated.
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K4MIA
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Posts: 7




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« Reply #3 on: March 22, 2010, 12:36:35 PM »

Yes I would like them to radiate the same on both bands. TNX Mike
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K4MIA
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Posts: 7




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« Reply #4 on: March 22, 2010, 01:58:13 PM »

Hello WX7G Dave,
   Thanks for the reply and information. Sounds like the project is a go. I have a couple more questions. The phasing lines (approx lengths). If verticals are spaced 66 feet apart. Can one phase line be 33 feet the other 66 to be feed out of phase and the add 33 feet to make them in phase. Or do I need to start out 1/4 wave on 80 ( 66 feet) and add 66 more feet to make it out of phase? Second question, in the future can I also use this setup as a Cardioid array? I live in Florida. Currently I have a Carolina Windom and running a KW I get into Europe and South, Central America  fine. But I need some help (gain) to improve the Pacific. Thats the reason for the additional antenna system.  
Mike
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NH7O
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Posts: 126


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« Reply #5 on: March 22, 2010, 06:21:39 PM »

In case your reading didn't include this site, it is relevant to your plans:

http://w8ji.com/phasing_systems.htm
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KL7AJ
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« Reply #6 on: March 22, 2010, 07:14:52 PM »

Yep, this will work.  Just be aware that wider spacing gives you more sidelobes....probably not a major concern.  

A bit trickier to get a cardioid pattern with the wider spacing, too...but you can fake it reasonably enough. Smiley

Sounds like fun indeed.

By the way...do you have a wayu of MEASURING the phasing accurately?

Eric
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K4MIA
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Posts: 7




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« Reply #7 on: March 22, 2010, 09:36:06 PM »

"By the way...do you have a wayu of MEASURING the phasing accurately? "

No Eric. Do you have a suggestions. Also, anyone out there know a NEC program that could model phasing of verticals. Hopefully a cheap or free one. Hi Hi

Thanks guys for all the reply's.

Mike
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KL7AJ
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« Reply #8 on: March 22, 2010, 10:18:44 PM »

MIA:

   Modeling phaese verticals is pretty simple with NEC.  IN fact a lot of phased vertical patterns area available from A.M. broadcast "pattern catalogs" so you don't have to reinvent the wheel.

ON4UN's Low Band DXing has a great section on antenna phase and amplitude monitoring.

Did you know you can get adjustable phasing with two T-match antenna tuners?  You can steer the antenna all over creation...but you need some phase monitoring to tell you where. Smiley

Eric
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W8JI
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« Reply #9 on: March 23, 2010, 11:44:48 AM »

Hello,
I am going to do my 1st attempt at phasing verticals. I have 2 Butternut HF2V verticals. I would like to have the phasing work on both bands. If I have them 66 feet apart can I phase them 1/4 wave on 80 meters and 1/2 wave on 40 meters. I know that it would be better phasing them on only one band. But could I do it without distorting the radiation patterns to bad. Get a good SWR in the phone DX windows and do without a tuner? Or if not, can it be setup for 80 and using tuner get good results on 40? I have done reading in ARRL Antenna Book, Low-Band DXing and Internet sights. But really could not find an answer.

Tnx and 73 Mike K4MIA

If you want them to have essentially the same end-fire pattern on both bands, they have to be spaced about 35 feet apart and you have to use a 90-135 degree delay on 40 and a 135-145 degree delay on 80.

You could use cross-fire phasing and use one delay line for both bands, but antenna impedances are an issue.
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WX7G
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Posts: 5975




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« Reply #10 on: March 23, 2010, 12:41:08 PM »

EZNEC can be used to model the antennas. This will account for the unequal antenna impedances and the effect this has on antenna current. The currents will not be equal in amplitude but you can decide if the antenna pattern is still ok.

More complex feed circuits can be used to set the amplitude and phase perfectly. But you might find (in NEC) that you obtain the performance you need with a simple transmission line phasing method.

Remember when you build the phasing lines to account for the velocity factor. This can be measured with an MFJ-259B or similar device.
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