Cecil Moore wrote in news:cIZSf.57484$Jd.33257
@newssvr25.news.prodigy.net:

Basil Burgess wrote:
It apparently tunes the antenna down to an SWR of 1.5, ...

An antenna tuner doesn't change the SWR between the tuner
and the antenna. If it's 100:1 before the tuner does its
thing, it is still 100:1 after the tuner does its thing.
The extra feedline losses are caused by that unchanging SWR.

Yep, though feedline losses are not usually so large as to preclude at
least SOME QSO's on 80 and 40 unless that SWR is AT LEAST 50 (especially on
80m). Of course poor quality coax and twinlead that is touching metal can
really increase those losses, even though they actually REDUCE the SWR that
the tuner is seeing.

A slinky is such a poor antenna to begin with (basically a coil of iron),
it's probably best to just feed it in the center with good quality 450 ohm
line (which you then dress properly all the way to the tuner's balanced
output--if the tuner has one or a balun located AT the tuner if it
doesn't). Next best would be to feed it with decent COAX like LMR400 or
better.

For example, my balcony whip gives an SWR of almost 6 on CW at 3652. I
could lower this by adding a capacity rig at the stinger end of the
hamstick, but I'm a bit too lazy to keep going out and taking it off and
the thing is resonant on 3729 where our phone net meets. But it's still 88
percent as efficient as it is at resonance when tuned up on 3652 with my
tuner, which can tune that SWR flat. (We won't talk about how inefficient
an 8ft antenna actually is on these frequencies, but you get the point).

And that's using RG8X (Belden 9258). Better coax would improve that some.
If the slinky actually has an SWR of 100, then 450 ohm ladder line would
introduce additional loss, due to SWR of 2.04 db per 100 feet.

Moral of the story, when using inefficient antennas with weird impedances,
then make sure you use good, low-loss feedline and keep it short as you
can.


--
Dave Oldridge+
ICQ 1800667

Owen, you know as well as I do his SWR meter does not indicate SWR on
the feedline where it might matter. So some of your comments don't
make much sense.
----
Reg.

Reg Edwards wrote:
Owen, you know as well as I do his SWR meter does not indicate SWR on
the feedline where it might matter. So some of your comments don't
make much sense.
----
Reg.


Just my two cents worth

For my first transmission aerial I made a three band trapped dipole of
split figure 8 mains cable(80,40 and 20) and fed it with coax, and
strung the centre about 25 foot in the air and falling to about 10 foot
at the ends. This has enabled me to work Britain, Spain, Italy and the
US with 40 odd watts SSB. SWR is not perfect and perhaps I should prune
it a little. The hardest part was tuning the traps. I believe this
design came from the arrl handbook.

I know that its not perfect and perhaps I should refine it, but for a
starter aerial I have found it very good. Having said that there are
things about it I want to experiment with.

One thing I have found invaluable is more experienced local hams who
will help.

There are people much more knowledgeable about antennas here than me,
but I am very happy with my home-brew antenna.

hth

73

Warren
ZL3LC

Thank you all for your help. The consensus seems to be that the overall
antenna is ill-conceived. I will revert the design to the original antenna
and work out how to rig it.

Thanks again for the information and education. I guess when one of you
hears me, you'll know I worked it all out :-)

73 to all
Basil Burgess, VE3JEB

On Sat, 18 Mar 2006 20:45:38 +0000 (UTC), "Reg Edwards"
wrote:

Owen, you know as well as I do his SWR meter does not indicate SWR on
the feedline where it might matter. So some of your comments don't
make much sense.

Reg,

If Basil measured the SWR at the ATU end of the RG8/X (either directly
or effectively with the ATU in bypass configuration if that is
possible), that would provide information that could be used to
estimate whether losses in the RG8/X were reasonable, and if
reasonable, how reasonable.

The RG8/X is probably the highest risk of serious loss in the antenna
system.

For clarity, I am not at all interested in the VSWR indicated looking
into the ATU unless the ATU is in the bypass configuration, in which
case the measurement is a valid indicator of the VSWR on the RG8/X.

The line loss of 50' of RG8/X at 3.6MHz with a source end VSWR of 8:1
is around 1dB, and probably quite acceptable. Beyond a source end VSWR
of 20:1, losses increase quickly to infinite loss at source end VSWR
around 28:1. If the indicated reflected *power* at the ATU end of the
coax is less than about 80%, or VSWR less than about 20, coax loss is
probably manageable.

Owen
--

Basil Burgess wrote:
Hello all

I've made a first attempt at installing an antenna. It's a 2 Slinky dipole
strung across my roof. I chose the Slinky dipole because it promised to give
good (if not excellent) results in a relatively short antenna. I strung it
between two 2' wood standards at the top of the roof. The roof is about
25-30' from the ground. I used the twin feedline, which is about 18', and
the insulators from a GSRV Mini antenna I bought. The twinline is connected
with a balun to a 50' RG-8X cable that runs across the roof and down to my
window. I've temporarily led it in through the window. The excess cable,
probably about 20 feet or so, is loosely coiled between the inner and outer
window.

The reception is great. I was picking up DX from Europe. However, I got no
answers to any attempt to call out. I wasn't expecting DX for my very first
QSO, but I was hoping for someone.

I think it may be because the feedline runs along the roof rather than
hanging in free space. Could this be the case? The SWR was terrible; it took
my automatic tuner a lot of work to get a match, but I was getting 1.5 or
less on 80 and 40.

Thank you for any advice you can offer.

73
Basil Burgess, VE3JEB

My email is basilb which is through hotmail

There is more to contacting DX then trying different antennas. You say
you are picking up DX from Europe so you obviously have a setup that
receives reasonably. How efficient it is transmitting is a different
issue. Can you make local contacts in Canada and the USA?

I was just trying to contact CN2R in Morrocco on 80 meters. I could
hear him fine but he doesn't seem to hear me. Well I am running 100
watts with a trap dipole. He probably can't hear me. He is also
probably running a kilowatt and I know he has great antennas. Much of
the DX you will hear may be running 10 times the power you are and that
is why you hear them and they don't hear you. Don't worry about the
antenna too much until you make local contacts and work your way out to
greater distances.
Also, you may have to call for a long time to get through the pileup
calling the DX (which you may not hear). Try calling CQ DX yourself and
see if anyone comes back.

Pete W6OP

Owen Duffy wrote:
On Sat, 18 Mar 2006 10:21:27 -0500, "Basil Burgess"
I've made a first attempt at installing an antenna. It's a 2 Slinky dipole
strung across my roof. I chose the Slinky dipole because it promised to give
good (if not excellent) results in a relatively short antenna. I strung it

There is nothing in your post to indicate how long or short your
antenna is. Perhaps it is a well known design and I just haven't heard
of it in my limited experience.

Owen and Basil,

The slinky dipole comes from the misplaced notion that packing a few
hundred feet of wire in a ten or twenty foot area makes an antenna a
few hundred feet long.

They totally miss the point of why an antenna radiates and how the
steel spiral affects the efficiency. There isn't any attempt to make
the antenna resoant either!

Overall it is a terrible system, unless you just happen through luck to
use it where the antenna has a low-order resonance and current maximum
at the feedpoint.

You could probably trim the slinky and make it work on a few bands
where it would be OK.

If you have enough room, just put up a dipole. Watch out for these
gimmick antennas. There isn't any magic bullet with antennas.

73 Tom

Hello

I'm sorry, though I tried to word that idea carefully, I left room for
confusion. I wasn't trying to work DX, I only meant that the antenna
received a clear signal from distant stations. I know that this is entirely
due to the sensitivity and selectivity of my receiver, and does not reflect
the ability to transmit to that distance. I had no expectation of getting
out to the rest of the world. I'd have been happy to talk to someone 3 miles
from me, for a first QSO.

Thank you for your ideas, though.

73
Basil VE3JEB
"pbourget" wrote in message
ups.com...

There is more to contacting DX then trying different antennas. You say
you are picking up DX from Europe so you obviously have a setup that
receives reasonably. How efficient it is transmitting is a different
issue. Can you make local contacts in Canada and the USA?

I was just trying to contact CN2R in Morrocco on 80 meters. I could
hear him fine but he doesn't seem to hear me. Well I am running 100
watts with a trap dipole. He probably can't hear me. He is also
probably running a kilowatt and I know he has great antennas. Much of
the DX you will hear may be running 10 times the power you are and that
is why you hear them and they don't hear you. Don't worry about the
antenna too much until you make local contacts and work your way out to
greater distances.
Also, you may have to call for a long time to get through the pileup
calling the DX (which you may not hear). Try calling CQ DX yourself and
see if anyone comes back.

Pete W6OP

Reg,

The type of antenna you describe is very useful and popular.

However, your assertion is much too sweeping as a generalization.
In no particular order, here are some caveats:
1. The qualifier "best" is largely meaningless, absent an agreed
set of weighted criteria for "goodness." (How important is:
size? weight? cost? visual profile? bandwidth? instant QSY?
gain? pattern? low-band performance vs. high-band performance?
power-handling capacity? need for tuner? etc., etc., etc.)
2. A good case can be made that choosing the "right" length is
"better" than a random length, within this type.
3. An excellent case can be made that center-fed is NOT always
the "best" option, within this type.
4. I'll let the fans of this antenna type chime in with why they
prefer balanced tuners and/or tuned feeders to the use of an
unbalanced tuner... if they want to. (I use more tailored antennas,
and don't need a tuner of any kind, most of the time.)

73, Ed


"Reg Edwards" wrote in message
...
The best, all round, all band, antenna is a high centre-fed dipole of
no particular length, fed with an open-wire feedline of no particular
length or impedance, all the way to the shack, used with a choke-balun
and an unbalanced tuner.

It is good down to the frequency at which the dipole is about
1/3-wavelength long.

Simplicity = efficiency.

Once tried you will never return to anything else.
----
Reg.

Old Ed wrote:
Reg,

The type of antenna you describe is very useful and popular.

However, your assertion is much too sweeping as a generalization.
In no particular order, here are some caveats:
1. The qualifier "best" is largely meaningless, absent an agreed
set of weighted criteria for "goodness." (How important is:
size? weight? cost? visual profile? bandwidth? instant QSY?
gain? pattern? low-band performance vs. high-band performance?
power-handling capacity? need for tuner? etc., etc., etc.)

I'm always hesitant to use words like "best" for all the reasons you
state, but I think that Reg qualified things pretty well. Within the
qualifications of all band dipoles, the ladder-line fed general dipole
is pretty darn hard to beat. I recommend them to any new hams that ask
me for advice on antennas.

My rationale is that most new hams these days buy rigs that are
all-band, transistorized units.These units are also sensitive to
mismatches between antenna and rig. Most new hams are not antenna gurus
either. So here is an antenna that will allow them to get on the air
without a lot of fussing. The only real measurement caveats are some
lengths that you don't want to use.

So we end up with an antenna that allows the newbie to get on the air,
allows them to learn some stuff by twiddling knobs and such, then when
they have a bit more experience, they can tackle that more "advanced
antenna" with it's more exacting design, trimming , and measurements.



2. A good case can be made that choosing the "right" length is
"better" than a random length, within this type.
3. An excellent case can be made that center-fed is NOT always
the "best" option, within this type.
4. I'll let the fans of this antenna type chime in with why they
prefer balanced tuners and/or tuned feeders to the use of an
unbalanced tuner... if they want to. (I use more tailored antennas,
and don't need a tuner of any kind, most of the time.)

As I do now. I've really been smitten with my OCF dipole, fed with
Coax, because in no small part, the feedpoint drops straight down to my
shack. That coupled with an automatic tuner in my radio , allowing me to
"plug and play.

But I still strongly urge newcomers to put up one of those ladder line
dipoles for the experience. They work okay, too! 8^)


"Reg Edwards" wrote in message
...
The best, all round, all band, antenna is a high centre-fed dipole of
no particular length, fed with an open-wire feedline of no particular
length or impedance, all the way to the shack, used with a choke-balun
and an unbalanced tuner.

It is good down to the frequency at which the dipole is about
1/3-wavelength long.

Simplicity = efficiency.

Once tried you will never return to anything else.
----
Reg.