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Author Topic: Installing a Multi-Band Wire Fan Dipole Question  (Read 1120 times)
KF7DS
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Posts: 190




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« on: November 12, 2012, 02:08:56 PM »

Currently I have a 6BTV ground mounted in the backyard, with about 24 ground mounted radials averaging about 20' each. Like many, the backyard is challenged with relatively moderate to steep slopes, lots of deciduous trees, etc...

The 6BTV does pretty well on 40-10, and narrow but ok on 80m. TX is pretty good, having reached AU, NZ, France, etc.... I could put down more radials, but it is not a level area, with some radials draped over rock walls, etc..

I may be able to get a Hy-Gain 18HT up, but the neighbors and xyl would prefer that to be the "last choice".

What I do have to my advantage is a lot of tall trees. Their height, combined with my sloping site, gives me the opportunity to get the center of an antenna like an Alpha Delta DXCC up around 55'-65'. I can probably get two up, one directed N-S and the other E-W.

Additionally, I am fortunate to be up 700' in elevation facing south, which helps a lot.

A few questions:

(1) Will such a dipole mounted at this height perform any better than a 6BTV as currently setup?

(2) For the DXCC I am thinking of running in a North-South direction...the slope goes downhill moderately from north to south. There is an elevation drop of about 20' over a 65'-70' distance. So, the north end of the dipole will be about 28' above ground, the center of the dxcc about 60' (though about only about 30' above the north leg).

What do I do with the south leg? Should it too be just like the north end, at 28' above the ground? Or, should it be on a horizontal line with the north leg, which would actually put the south end about 48' above ground at this point.

(3) Once the deciduous trees bloom, will the antenna get detuned? Does rain impact these antennas?

Any feedback would be appreciated.

Best,
Don KF7DS
« Last Edit: November 12, 2012, 02:11:25 PM by KF7DS » Logged
K1ZCY
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Posts: 3




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« Reply #1 on: November 12, 2012, 07:33:31 PM »

It's good to have both. At times one will work better than the other. Depending on the angle of radiation the signal is coming in.
I have both vertical dx88 and the alphadelta fan dipole. I have been using them for years. Right now I have the cobra antenna up and plan to put up my vertical cause i'm at a new qth. If you have tghe chance to put up the hy-tower go for it.
73's John k1zcy
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KF7DS
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Posts: 190




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« Reply #2 on: November 12, 2012, 09:35:25 PM »

Yes, I was down the slope this afternoon looking at the possibilities. I assume that I cannot have a part of the dipole over the radials for the vertical, which I would have to work around.

Actually, the best area was down slope away from houses, giving an e-w alignment to the ends, thus radiating n-s : am looking to get a nw-se alignment.

Any hints to rigging it up?

Don KF7DS
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K2DC
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« Reply #3 on: November 13, 2012, 03:21:11 AM »

I assume that I cannot have a part of the dipole over the radials for the vertical, which I would have to work around.

Why would you assume that?  I don't see why running the dipole over some of the radials shouldn bother much at all at that height.  If you can keep the south leg horizontal, it should help to have as much of the antenna as high as possible.

73,

Don, K2DC
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K3VAT
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« Reply #4 on: November 13, 2012, 04:49:21 AM »

Yes, I was down the slope this afternoon looking at the possibilities. I assume that I cannot have a part of the dipole over the radials for the vertical, which I would have to work around.  Don KF7DS 

K2DC is correct.  In fact, I purposely positioned one of my dipoles over the ends of the radial field.  Additionally, I have lots of sloping terrain and I positioned the other dipole to take advantage of the slope.  If you have ON4UNs book LowBand DX'ing, both of these topics are covered in depth.

Any antenna whether it be a dipole or vertical has nulls: places where both the recv and xmit signals are way down.  That's why you need to study both the antenna pattern and the affect of sloping ground when you want to position your antennas for max signals.  Having two or more antennas tends to compensate.  GL, 73, Rich, K3VAT

5BDXCC on wires
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KF7DS
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Posts: 190




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« Reply #5 on: November 13, 2012, 01:00:20 PM »

Thanks for setting me straight. I thought that the radials would absorb ground waves too much and attenuate the dipole.

And, I just purchased the book on low band dx'ing...that should be a good read.

Also, I have been thinking of having my tree guy over for a day to put up stainless pulleys in the three points the dipole will be mounted (each pulley would be hung from a limb) so that I can raise and lower any or all parts to my hearts content, which should make tuning and maintenance a whole lot easier. I am also going to have him trim branches from close-by trees to open up free space for the dipole.

This actually brings up another question

-I have a Rigexpert antenna analyzer which I will use to tune the DXCC. Do I raise the antenna ends to operating height to get an SWR read; lower and adjust; then raise again to take another reading and iterate the process until satisfied...? I would assume so...but, what length of coax should I use...just enough between the antenna connection and ground where I am standing with the analyzer?



Thanks,
Don KF7DS
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K3VAT
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Posts: 715




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« Reply #6 on: November 13, 2012, 05:41:12 PM »

...
And, I just purchased the book on low band dx'ing...that should be a good read.
...
Thanks,
Don KF7DS

Very Good! Excellent reference.

...
I have a Rigexpert antenna analyzer which I will use to tune the DXCC. Do I raise the antenna ends to operating height to get an SWR read; lower and adjust; then raise again to take another reading and iterate the process until satisfied...? I would assume so...but, what length of coax should I use...just enough between the antenna connection and ground where I am standing with the analyzer?
...

OK, which antenna are we talking about?  And what portion (CW or SSB) do you favor?

I'm uncertain if you're referring to a multiband OR a single band ... refresh my old memory.

73, Rich, K3VAT

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KF7DS
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Posts: 190




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« Reply #7 on: November 14, 2012, 06:42:51 AM »

Rich

Am a CW op.

I was thinking for my first foray into a dipole, I will try the Alpha Delta DXCC that was given to me as a Christmas gift last year, so a multi-bander. Was too busy and lazy to consider installing it, but the more I realized I could get it up 50'-60' in an area cleared by the tree guy, I became more interested.

My goal is to string one dipole n-s and the other e-w. And, they will be mostly out of view and 50' away from any house -pretty hard in the City, so I am fortunate. And, I can keep the vertical.

Don KF7DS
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