HF is Smokin
 

20m is especially good. I have a 20m dipole and I answered a CQ from
Eastern Russia (4200+ miles) and Viktor RU0ZM, came right back to me. Then
I noticed I was on tune power, 10W. Great night.

"Sal"

HF is Smokin
 

On Sat, 28 Apr 2012 21:11:30 -0700, "Sal" wrote:

20m is especially good. I have a 20m dipole and I answered a CQ from
Eastern Russia (4200+ miles) and Viktor RU0ZM, came right back to me. Then
I noticed I was on tune power, 10W. Great night.

"Sal"

Thanks. I turn on my ancient Icom IC-735, tune around 20 meters and
hear nothing. Transmit and I get infinite VSWR. Ok, something is
wrong. After 15 minutes of juggling coax cables, spinning knobs,
pushing buttons, and head banging, the light comes on in my head.
After a nasty wind storm in January, I a tree had destroyed most of my
antenna farm, which I haven't repaired. Rebuild antennas now added to
the things to do list.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

HF is Smokin
 

"Jeff Liebermann" wrote in message
...

After a nasty wind storm in January, I a tree had destroyed most of my
antenna farm, which I haven't repaired. Rebuild antennas now added to
the things to do list.


--
Jeff

Luckily,in SoCal we don't contend with that very often -- Santa Ana winds in
the canyons being the occasional exception. I feel for you.

Meanwhile, just hang up any old thing and agitate some 'trons. A 20m dipole
at 15 feet (one end tied off to my chimney and the other end to a branch in
my neighbor's macadamia nut tree) is all I have or apparently need. Yes, 1
KW into a SteppIR on a 50 foot tower is better, but at a cost of several
thousand dollars per S-unit.

Really, it's all good. Maybe you heard my long-ago story about my 20m
first-ever QSO with Hawaii. I got a 5-9 but the antenna was primitive: an
existing 10m vertical dipole, with one end clipped to an extension ladder
laying on the ground. True.

"Sal"
(KD6VKW)

HF is Smokin
 

On Sun, 29 Apr 2012 12:13:28 -0700, "Sal" wrote:

Luckily,in SoCal we don't contend with that very often -- Santa Ana winds in
the canyons being the occasional exception. I feel for you.

The winds wasn't that bad. I live in a redwood, fir, oak, and madrone
forest, which blocks most of the wind. The problems are caused by
falling trees and limbs. I have a fair size ding in my car hood, and
had an oak tree land on my flat roof, destroying most of my antennas
and trashing in a skylight. Most of the shock was absorbed by my
neighbors roof.
http://802.11junk.com/jeffl/pics/2011-12-03-Storm/
So much for the idyllic life in the forest.

Meanwhile, just hang up any old thing and agitate some 'trons. A 20m dipole
at 15 feet (one end tied off to my chimney and the other end to a branch in
my neighbor's macadamia nut tree) is all I have or apparently need. Yes, 1
KW into a SteppIR on a 50 foot tower is better, but at a cost of several
thousand dollars per S-unit.

There's no way I can rotate a horizontal antenna without hitting a
tree or the hillside behind my house. A tower might help, if it were
200ft high, and the swaying trees won't hit the antenna. I'm stuck
with using wire antennas and verticals.

Really, it's all good. Maybe you heard my long-ago story about my 20m
first-ever QSO with Hawaii. I got a 5-9 but the antenna was primitive: an
existing 10m vertical dipole, with one end clipped to an extension ladder
laying on the ground. True.

Yep, RF is magic. I managed to make a QSO into a Heathkit Cantenna,
but that's about the limits of my non-traditional antenna experiments.
One of these days, I'm going to build an NEC2 model of an aluminum
ladder and see what can be done to use it on VHF or UHF.

So, I climbed up on my roof with a balun and some wire, intending to
make a dipole. Normally, this is a trivial exercise. However,
there's a problem. All the labels have peeled off my multitude of
coax cables. The labels were UV proof but apparently not water proof.
Almost all of my coax cables came off the same roll of RG6a/u and look
identical. This is going to be a problem.

I did manage to find all the parts to a Radio Shock discone antenna,
which is now simulating a wet noodle on top of a 10ft 3/4" PVC pipe.
That's because I can't find a single 10ft mast section that doesn't
have a fatal dent or bend.

The 12ft(?) long VHF/UHF Comet fiberglass antenna survived the tree
fall, but will need to come down for some cleaning. The outside is
covered with green slime. Experience has shown that when the outside
is covered with green slime, so is the inside.

Maybe I should give up for the day, and just clean up the workbench.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

HF is Smokin
 

On Sat, 28 Apr 2012 21:11:30 -0700, Sal wrote:

20m is especially good. I have a 20m dipole and I answered a CQ from
Eastern Russia (4200+ miles) and Viktor RU0ZM, came right back to me.
Then I noticed I was on tune power, 10W. Great night.

"Sal"

20m was good yesterday as well, I made several European contacts in just
a few minutes on PSK31 (from 4 land).

HF is Smokin
 

On Sun, 29 Apr 2012 14:07:22 -0700, Jeff Liebermann
wrote:


I did manage to find all the parts to a Radio Shock discone antenna,
which is now simulating a wet noodle on top of a 10ft 3/4" PVC pipe.
That's because I can't find a single 10ft mast section that doesn't
have a fatal dent or bend.

The 12ft(?) long VHF/UHF Comet fiberglass antenna survived the tree
fall, but will need to come down for some cleaning. The outside is
covered with green slime. Experience has shown that when the outside
is covered with green slime, so is the inside.

Maybe I should give up for the day, and just clean up the workbench.

Scale back a little....
I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.
I hardly ever use 80m, no particular reason, I just don't.
The ends droop to whatever was convenient. I did not bother to
consider anything permanent. Most of the ends are secured at the
perimeter of the yard via nylon braided line attached to military
surplus fiber glass mast sections leaning into convenient trees. I
only worried about keeping the ends high enough to avoid contact with
people, tractors and deer in the yard.

It seems to work well on all bands I have tried. Although I prefer my
manual MFJ tuner, the internal tuner in my TenTec Jupiter seems to do
OK. I am not a contester, a DX hound or a perfectionist but I do like
to spend a little time on the air.

I would make up a coax balun of about 8 turns of coax on a milk jug
with connectors appropriate to the roof connections. The Dollar Store
here sells black vinyl tape for about $1 for two rolls so wrap the
balun up well enough to not become a future problem. Pick any cable
handy on the roof, assuming that they all go to the shack. When you
get to the shack, use the cable that has signals on it.

I don't know which direction is favored on any band nor do I really
have any idea which elements are active under any given circumstance.

It will keep you on the air and give you time to decide where you want
to go from here with out undue pressure!
John Ferrell W8CCW

HF is Smokin
 

On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:

I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).

It seems to work well on all bands I have tried. Although I prefer my
manual MFJ tuner, the internal tuner in my TenTec Jupiter seems to do
OK.

Antenna tuners can be quite lossy. Have fun with this Java app:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html

Do you have a field strength meter? Find a location in the pattern
and as far away as practical. View the meter from your operating
position using binoculars or a telescope. Try your fan dipole
directly to the 50 ohm output of your transmitter. Hopefully, the
VSWR will be less than what it takes to trip the VSWR protection
circuitry. Now, install the antenna tuner and try again, keeping the
RF power at the same level. If you have problems leveling the RF
power, use an AC powermeter, such as a Kill-a-Watt, to measure the AC
input power consumption. When I did the same test, the antenna tuner
always had noticeably less TX signal strength.

I am not a contester, a DX hound or a perfectionist but I do like
to spend a little time on the air.

I spend more time inside the radios than in front of them.

It will keep you on the air and give you time to decide where you want
to go from here with out undue pressure!

The answer for me was supplied by outside influences. A mess of work
arrived at my shop, so I'll be too busy to do antennas for a while.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

HF is Smokin
 

Jeff Liebermann wrote:
On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:

I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).


FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

That appears to be also true for trap antennas from some limited EZNEC
modeling.

Of course, there is always the alternative of throwing technology and
money at the problem and just put up whatever wire you can and put an
autotuner up.

HF is Smokin
 

"Jeff Liebermann" wrote in message
...

On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:

I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).
snip

I have antenna challenged yard, with no available supports for horizontals.
So I've been experimenting with vertical radiators mounted on a 12 by 30
foot metal patio cover.

Initially, I used a CB whip, fed with RG-58 to a tuner in the shack, quite
successfully on 24 and 28 MHz. After a few more tests, (and more tests are
planned) I settled on a 14 foot radiator that works well on 20-10 meters.
It did a good job on all those bands during the recent DX contests, but
obviously won't bust a full fledged pileup without some operational cunning.

The antenna is fed with 25 feet of RG-8 to an RF ammeter in the shack and on
to a tuner. The ammeter is used to get the most current with various tuner
settings/configurations, but without changing anything from the ammeter to
the antenna.

So, a tuner in the shack feeding a single dipole might fit your band
coverage and real estate requirements. Play around a bit with EZNEC and try
a few things.

HF is Smokin
 

On 1 May,
wrote:

FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

I've got 12 and 10 working fine together, seperated by about 8" giving a
decent match. It also works fine on 15 although no wires for 15, but a short
coax (20') to an ATU. It has a "pawsey stub" balun cut for about 17m (modeled
with NEC for best match with fan dipoles for all bands 20 -10, but I haven't
as yet got round to dipoles for 15 and below).

--
BD
Change lycos to yahoo to reply

HF is Smokin
 

HF is Smokin
 

On 3 May,
wrote:

I was refering to the case where there is nothing to adjust the match and
getting something under 3:1 at the end of the feed line.

It was well within 1.5:1 within (part of) 10 and 12m bands.



Given an ATU, you can usually match anything and there is no need for the
physical complexity of a fan dipole.

Very true The ATU is only used for 15,17 and 20, but my (larger) doublet
with tuned feeders is better for 20 and 17, and about the same for 15.

I'm currently debating whether to add additional dipoles to the fan or
replace it with a smaller doublet (about a half wave on 20), which would be
about half the size of the existing doublet.

I may end up trying both, I doubt if there will be much difference apart from
a slight change in directivity.

--
BD
Change lycos to yahoo to reply

HF is Smokin
 

wrote in message ...

wrote:
On 1 May,
wrote:

FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length
adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

I've got 12 and 10 working fine together, seperated by about 8" giving a
decent match. It also works fine on 15 although no wires for 15, but a
short
coax (20') to an ATU. It has a "pawsey stub" balun cut for about 17m
(modeled
with NEC for best match with fan dipoles for all bands 20 -10, but I
haven't
as yet got round to dipoles for 15 and below).

# I was refering to the case where there is nothing to adjust the match and
# getting something under 3:1 at the end of the feed line.
#
# Given an ATU, you can usually match anything and there is no need for the
# physical complexity of a fan dipole.

An open wire fed dipole would give pretty good performance. But, feeding
such an antenna with RG-8 and living with a high VSWR (maybe up to 10:1)
shouldn't be discarded.

A dipole of about 18 feet would cover 24 and 28 MHz with about 5:1
VSWR....not bad.

HF is Smokin
 

HF is Smokin
 

Wayne wrote:


wrote in message ...

wrote:
On 1 May,
wrote:



# I was refering to the case where there is nothing to adjust the match and
# getting something under 3:1 at the end of the feed line.
#
# Given an ATU, you can usually match anything and there is no need for the
# physical complexity of a fan dipole.

An open wire fed dipole would give pretty good performance. But, feeding
such an antenna with RG-8 and living with a high VSWR (maybe up to 10:1)
shouldn't be discarded.

A dipole of about 18 feet would cover 24 and 28 MHz with about 5:1
VSWR....not bad.

My transmitter gives up at about 5:1.

Your milage (and transmitter) may vary.

HF is Smokin
 

wrote in message ...

Wayne wrote:


wrote in message ...

wrote:
On 1 May,
wrote:



# I was refering to the case where there is nothing to adjust the match
and
# getting something under 3:1 at the end of the feed line.
#
# Given an ATU, you can usually match anything and there is no need for
the
# physical complexity of a fan dipole.

An open wire fed dipole would give pretty good performance. But, feeding
such an antenna with RG-8 and living with a high VSWR (maybe up to 10:1)
shouldn't be discarded.

A dipole of about 18 feet would cover 24 and 28 MHz with about 5:1
VSWR....not bad.

# My transmitter gives up at about 5:1.

# Your milage (and transmitter) may vary.

Yes. My Yaesu ATU gives up at 5:1, so I have been using a more robust
homebrew tuner.

A VSWR of up to say 10:1 (perhaps 15:1) shouldn't be a deal killer, if you
can match the coax and are willing to accept 2-3 dB of loss. This opens up
a lot of antenna possibilities that might be otherwise discarded.

Out in the YARD, on top of 30' of 1.25 inch semi rigid conduit I have a Solorcon A99 that looked like a fussy Popsicle stick that a friend of mine gave to me that I painted with some dollar general store paint - which tunes up with the internal antenna tuner in my Kenwood TS 590S - which is below 2:1 on 10 / 12 / 15 / and 17 even without the tuner - as long as you stay within the bands - 28.300 - 28.500 etc.... And will tune up beyond that - 26.950 / 29.690 MHz with the internal tuner...

HF is Smokin
 

Wayne wrote:


wrote in message ...

Wayne wrote:


wrote in message ...

wrote:
On 1 May,
wrote:



# I was refering to the case where there is nothing to adjust the match
and
# getting something under 3:1 at the end of the feed line.
#
# Given an ATU, you can usually match anything and there is no need for
the
# physical complexity of a fan dipole.

An open wire fed dipole would give pretty good performance. But, feeding
such an antenna with RG-8 and living with a high VSWR (maybe up to 10:1)
shouldn't be discarded.

A dipole of about 18 feet would cover 24 and 28 MHz with about 5:1
VSWR....not bad.

# My transmitter gives up at about 5:1.

# Your milage (and transmitter) may vary.

Yes. My Yaesu ATU gives up at 5:1, so I have been using a more robust
homebrew tuner.

A VSWR of up to say 10:1 (perhaps 15:1) shouldn't be a deal killer, if you
can match the coax and are willing to accept 2-3 dB of loss. This opens up
a lot of antenna possibilities that might be otherwise discarded.

Well, my trap inverted vee for 40-30-20-15-10 has a SWR of less than 2:1
where all my interests lie, and less than 1.5:1 on most bands.

Then there is the vertical that currently covers 160-10 at less than 1.3:1
on all frequencies for the days when I want to do something different.

It started out as about 33 feet of tubing for 40.

Wanting more, I built an enclosure containing a pair of relays and loading
coils so it was less than 2:1 on the areas of interest on 160 and 80.

Wanting more, I mounted a SGC autotuner at the base so it is always 1.3:1
or less on all bands.

EZNEC analysis says the lobes are low, and actually have some low angle
gain on 15 and 17, until I get to 12 and 10, where the lobes start pointing
to the sky.

The next modification will likely be finding a 10 M trap at a swap meet
and installing it at about 5/8 wavelengths to push the 10 M lobe down.

I can live without perfection on 12.

HF is Smokin
 

wrote in message
...
Jeff Liebermann wrote:

snip


FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can

I had a 10-20 fan dipole laying on a roof for a while. Matched OK after a
bit of pruning but I abandoned it when I found both bands were better with
antennas that were clear of the roof.

I wonder something (and I suppose I'll have to try it, now) : Say I had a
20m horizontal dipole up at 30 feet, could I feed it through a coax that had
a Tee-connector located 22 feet up and simultaneously feed a 15m antenna
from that Tee-connector?

Just as they would be in parallel as a true fan dipole with a common feed
point, so also would they be in parallel -- just not sharing a common feed
point.

Normally I avoid Tee-connectors because they introduce the Evil Mismatch but
this time ...

I can see one problem already; some of the 15m energy that divides at the
Tee-connector would go up to the 20m antenna and be partially radiated and
partially reflected. Standing waves. The coax length would alter the
effect.

"Sal"

HF is Smokin
 

On 5/1/2012 12:43 PM, wrote:

FYI I spent an afternoon with EZNEC exploring fan dipoles.

I've used those for many years.. Probably my #1 most used antenna.
I have them here at the house, and also up in the country at
the recreational living center.


What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

Yep, and if at right angles, there is virtually no interaction at all.
I've had cases with dipoles at right angles where one leg broke off,
and the SWR for the unbroken intact dipole did not change.


From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

yep, and it can get weird.. IE: the tuning appears to work backwards
from the norm.. It will almost always be one of the higher bands that
is effected. Rarely the lower band. And in many cases, you will end
up adding wire to the higher band dipole, to come up the band. A bit
peculiar, but I've seen it many times.


It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

Not sure if I agree with that. I would think it *should* work if the
two dipoles are at right angles. And likely good nuff for gov work,
even if at a closer angle.
But it's not something I've really tested, as I generally don't worry
about the higher bands, and tend to load the lower band wires on the
higher bands. I rarely ever string dipoles for 17,15,12,or 10..
The 40 meter legs pretty much cover 15m for instance.. I've never added
15m legs, as I always have 40 legs.. I have often added 20m legs though,
as the 40m as a half wave on 20 is the pits when coax fed.. :(



That appears to be also true for trap antennas from some limited EZNEC
modeling.

Of course, there is always the alternative of throwing technology and
money at the problem and just put up whatever wire you can and put an
autotuner up.

Yep.. But I've always like the parallel fed dipoles.
It's almost a perfect system. When tuned and operated correctly, the
dipoles function pretty much the same as single band dipoles, with
no tuner needed, and pretty much the same efficiency as a single band
dipole fed with coax. For multi band use, it's more efficient than
most any other scheme I can think of as far as the bands that have
dipoles, or have a good match for other reasons. IE: 3/4 wave resonance.
The one here at the house is 80/40/20. The one up in the country is
80 and 40. I did also have 160m legs on that one at one time, but a
storm whacked it out, and when I rebuilt it, I didn't bother with the
160m legs.
If I want to use a higher band, I use a tuner and accept the small
loss.. I actually don't get on the higher bands much.. I'm on 40 in
the day, and 80 at night most all of the time. Also 160 at night if
I have it, but that is a bit seasonal.. You won't see me on 160 much
in the summer.. So much noise, you really need an amp, and none of the
amps I have work 160m.

HF is Smokin
 

On 3 May,
wrote:

wrote:
On 3 May,
wrote:

I was refering to the case where there is nothing to adjust the match
and getting something under 3:1 at the end of the feed line.

It was well within 1.5:1 within (part of) 10 and 12m bands.

After spending several hours with EZNEC trying to get that combination
under 5:1 with no success, I find that hard to believe unless something in
the system is really lossy (like the feedline) and masking the SWR or the
length of the feedline just happens to be at a length to help the match.

Well I modelled it and matched it fine on the two bands The ends of the
feeder are about 4" apart and effectively the inner ends of the longer dipole
are an 8" length of 600 ohm line, so that length comes off the 12m dipole
elements. I couldn't get it to match with it as a genuine fan (inner ends
paralelled) with any small spacing at the ends of the dipoles, so I made them
about 8" apart.

Then they matched up nicely. The feeder is short, and low loss, as seen by
the out of band (mis)match.

The trick is to make the dipoles far enough seperated so as to be seen by the
feeder as seperate elements. This lost me much time.



--
BD
Change lycos to yahoo to reply

HF is Smokin
 

On Thu, 3 May 2012 00:37:47 -0000, wrote:

wrote:
On 3 May,
wrote:

I was refering to the case where there is nothing to adjust the match and
getting something under 3:1 at the end of the feed line.

It was well within 1.5:1 within (part of) 10 and 12m bands.

After spending several hours with EZNEC trying to get that combination under
5:1 with no success, I find that hard to believe unless something in the
system is really lossy (like the feedline) and masking the SWR or the length
of the feedline just happens to be at a length to help the match.

EZNEC lacks an optimiser. Try 4NEC2 and let the optimiser tweak the
wire lengths for best VWSR in the various bands.
http://www.youtube.com/watch?v=kYy6Yur127A 25min
The bad news is that since the fan dipole works on several bands, the
optimizer has to be run individually for each band. Fortunately, it
is easy to limit the parameters that it changes to just the wire
length for that band in question. I'm tempted to build an NEC2 model
and see what happens. Maybe this weekend.

I blundered across this article on fan dipole construction:
http://www.hamuniverse.com/multidipole.html
http://sstowers.com/aa4cv/
If I can find a long straight location, that doesn't come too close to
a tree, I might try a fan dipole again.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

HF is Smokin
 

On 3 May,
wrote:

The next modification will likely be finding a 10 M trap at a swap meet
and installing it at about 5/8 wavelengths to push the 10 M lobe down.

Why not put a quarter wave stub for 10metres about half wave down from the
top to make it radiate as two half waves in phase on 10? That would also
guive a little loading on the more LF bands increasing efficency slightly.
I'm not sure without checking what the effect on the bands below 20 would be.

--
BD
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HF is Smokin
 

HF is Smokin
 

HF is Smokin
 

Sal wrote:

wrote in message
...
Jeff Liebermann wrote:

snip


FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can

I had a 10-20 fan dipole laying on a roof for a while. Matched OK after a
bit of pruning but I abandoned it when I found both bands were better with
antennas that were clear of the roof.

I wonder something (and I suppose I'll have to try it, now) : Say I had a
20m horizontal dipole up at 30 feet, could I feed it through a coax that had
a Tee-connector located 22 feet up and simultaneously feed a 15m antenna
from that Tee-connector?

Just as they would be in parallel as a true fan dipole with a common feed
point, so also would they be in parallel -- just not sharing a common feed
point.

Normally I avoid Tee-connectors because they introduce the Evil Mismatch but
this time ...

I can see one problem already; some of the 15m energy that divides at the
Tee-connector would go up to the 20m antenna and be partially radiated and
partially reflected. Standing waves. The coax length would alter the
effect.

If I were going to do that, I would use ladder line between the elements
and connect the coax to the bottom.

It would be easy to model this with EZNEC, even the free demo version, so
I would do that first.

HF is Smokin