Vinnie S. wrote:
Hi, I was looking to buy one of these. But running ground radials will be a
problem because the area is woods. I was looking to not using ground radials. I
do have a small running stream in the woods. Would a ground rod in the stream,
offer a good counterpoise that would eliminate the need for radials?

A ground rod would result in rather high ground losses.
With woods all around, why not put up a multi-band dipole?
--
73, Cecil, http://www.qsl.net/w5dxp

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On Thu, 01 Sep 2005 12:31:06 -0500, Cecil Moore wrote:

Vinnie S. wrote:
Hi, I was looking to buy one of these. But running ground radials will be a
problem because the area is woods. I was looking to not using ground radials. I
do have a small running stream in the woods. Would a ground rod in the stream,
offer a good counterpoise that would eliminate the need for radials?

A ground rod would result in rather high ground losses.
With woods all around, why not put up a multi-band dipole?

That was my first choice. I am not strong on antenna theory, so I and afraid to
build one. I was looking at a Alpha Delta DX-CC, but they have been on backorder
sonce March. I emailed them 3 weeks ago, and they said 7-10 days. I emailed them
again today, and they said 2 weeks. I liked that antenna because of the coax
feed. I was trying to sta away from the other dipole that use ladder line.

Vinnie S.

Vinnie S. wrote:

wrote:
A ground rod would result in rather high ground losses.
With woods all around, why not put up a multi-band dipole?

That was my first choice. I am not strong on antenna theory, so I and afraid to
build one. I was looking at a Alpha Delta DX-CC, but they have been on backorder
sonce March. I emailed them 3 weeks ago, and they said 7-10 days. I emailed them
again today, and they said 2 weeks. I liked that antenna because of the coax
feed. I was trying to sta away from the other dipole that use ladder line.

A 130 ft. dipole fed with 450 ohm ladder-line through a good
choke is hard to beat as an all-HF-band antenna and costs
about $25.
--
73, Cecil, http://www.qsl.net/w5dxp

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On Thu, 01 Sep 2005 13:56:12 -0500, Cecil Moore wrote:

Vinnie S. wrote:

wrote:
A ground rod would result in rather high ground losses.
With woods all around, why not put up a multi-band dipole?

That was my first choice. I am not strong on antenna theory, so I and afraid to
build one. I was looking at a Alpha Delta DX-CC, but they have been on backorder
sonce March. I emailed them 3 weeks ago, and they said 7-10 days. I emailed them
again today, and they said 2 weeks. I liked that antenna because of the coax
feed. I was trying to sta away from the other dipole that use ladder line.

A 130 ft. dipole fed with 450 ohm ladder-line through a good
choke is hard to beat as an all-HF-band antenna and costs
about $25.


I have to do a inverted V config. I would be unable to run it horizontal. Can I
build one using simply a coax feed?

Vinnie S.

In article ,
Vinnie S. wrote:

A 130 ft. dipole fed with 450 ohm ladder-line through a good
choke is hard to beat as an all-HF-band antenna and costs
about $25.

I have to do a inverted V config. I would be unable to run it horizontal. Can I
build one using simply a coax feed?

A single dipole, fed with coax, configured as an inverted V, will
serve well on its resonant frequency and is also usable on its odd
harmonics. For example, a dipole cut for 40 meters (nominally 66 feet
in length for a horizontal, and perhaps 60 feet in length as an
inverted V) can usually be used on 15 meters as well since that's
close to the third harmonic.

Such an antenna will not serve well as an "all-band" antenna. Its
feedpoint impedance will be too high, or too reactive, on non-resonant
bands (e.g. on 20, the above dipole will have a very high feedpoint
impedance). You may be able to tune it on non-resonant bands using a
wide-range external transmatch, but the losses in the coax and
transmatch due to the high VSWR will likely be prohibitive.

Several solutions to this:

- Feed the dipole with ladder line or open-wire line, use a good choke
or balun and a good tuner/transmatch, and if necessary tune the
length of the wire so that the impedance seen at the transmatch is
acceptable.

- Build a multi-wire "fan" dipole, with one set of wires cut for each
band of interest. These are somewhat easier to trim (less
interaction between the wires) if the wires are fanned apart at a
broad angle, but it's quite possible to get them to work with each
wire simply hanging 6" below the next-longest one using simple
insulators of some sort. I use a three-wire fan dipole of this
sort, cut for 40/20/10, fed with coax, and it works quite respectably.

- Use a trap dipole (feeding with coax should be fine).

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Thu, 01 Sep 2005 22:24:56 -0000, (Dave Platt)
wrote:

A single dipole, fed with coax, configured as an inverted V, will
serve well on its resonant frequency and is also usable on its odd
harmonics. For example, a dipole cut for 40 meters (nominally 66 feet
in length for a horizontal, and perhaps 60 feet in length as an
inverted V) can usually be used on 15 meters as well since that's
close to the third harmonic.

However, although it may "match" on 15-meters it will not work all
that great as the effective antenna height will be substantiality
lower. (Been there done that!).

Danny, K6MHE

On Thu, 01 Sep 2005 22:24:56 -0000, (Dave Platt) wrote:

In article ,



- Build a multi-wire "fan" dipole, with one set of wires cut for each
band of interest. These are somewhat easier to trim (less
interaction between the wires) if the wires are fanned apart at a
broad angle, but it's quite possible to get them to work with each
wire simply hanging 6" below the next-longest one using simple
insulators of some sort. I use a three-wire fan dipole of this
sort, cut for 40/20/10, fed with coax, and it works quite respectably.

Can I use inulated 14 AWG wire and not use the fan method? Can I run them tied
together?

- Use a trap dipole (feeding with coax should be fine).


Vinnie S.

In article ,
Vinnie S. wrote:

Can I use inulated 14 AWG wire and not use the fan method? Can I run them tied
together?

The closer the wires are together, the greater the amount of
electrical coupling between them. As the amount of coupling
increases, the wires' ability to behave independently decreases... one
effect is that the useful SWR bandwidth of the wires becomes narrower.
The presence or absence of insulation won't have too much effect on
this change... some, but not a lot.

Eventually, if the wires are close enough together, they'll tend to
behave pretty much like one wire (the longest one) which is "fatter"
near the feedpoint, and you'll lose the ability to tune the
higher-frequency bands properly.

A separation of 4-5" inches seems to work pretty well. There are
plans in one of the ARRL handbooks which show a "fan" dipole made from
300-ohm twinlead, with one wire cut off short (and a second 300-ohm
section with two even shorter wires hung an inch or so below). I'd
expect this to have a narrower useful bandwidth on the shorter-wire
bands than one with a 4" separation.

I've even heard of people making these sort of fan dipoles out of
computer-type ribbon cable, in which the wires are only about a tenth
of an inch apart! I have no personal experience with this particular
version and don't how well this actually works in practice, but I have
a feeling it might be difficult to get to tune properly.

I suppose you could try making one with insulated wire, with the wires
tied together every few feet, and the shorter (lower) wires being tied
in loosely so that they sag downwards a few inches in between the
ties. This might separate 'em enough to allow for independent tuning.

If you can use insulators, do so, is my advice. You can make
insulators very cheaply from short lengths of 1/2" PVC irrigation
tubing.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Vinnie S. wrote:
I have to do a inverted V config. I would be unable to run it horizontal. Can I
build one using simply a coax feed?

If you go with coax, you probably should use multiple dipoles (fan)
or a trapped dipole to obtain a low feedpoint impedance on your
bands of choice.
--
73, Cecil http://www.qsl.net/w5dxp


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