using an MFJ-941E tuner on all bands?
 

Hi, I was just reading the user's manual for the MFJ-941E antenna
tuner,
http://www.mfjenterprises.com/produc...rodid=MFJ-941E and on page
5, there is a warning, which reads:

"WARNING: To avoid problems, a dipole antenna should be a full half-
wave on the lowest band.
On 160 meters, an 80 or 40 meter antenna fed the normal way will be
extremely reactive with only
a few Ohms of feedpoint resistance. Trying to load an 80 meter (or
higher frequency) antenna on
160 meters can be a disaster for both your signal and the tuner. The
best way to operate 160 with
an 80 or 40 meter antenna is to load either or both feedline wires (in
parallel) as a longwire. The
antenna will act like a "T" antenna worked against the station
ground."

Half wave for 160 meters is around 264ft. So, it sounds like even with
a tuner (or at least this tuner), I would need at least this much wire
to transmit on 160 meters.

My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands. What bands can I reasonable expect
to transmit on using a 100ft dipole and a tuner?

That last part of the warning about using an 80 meter dipole as a
longwire has me totally confused. Are they saying to snip off the
coax connector and plug the ends into the longwire connector in the
back of the tuner?


Jim

P.s. I finally have the 21st edition of the ARRL Antenna book. I'm
only on chapter 2, so please feel free to point out page numbers or
chapters that would probably answer my questions.

using an MFJ-941E tuner on all bands?
 

On Mon, 26 Nov 2007 10:47:15 -0800 (PST), James barrett
wrote:

I'm
only on chapter 2, so please feel free to point out page numbers or
chapters that would probably answer my questions.

Hi Jim,

That would be too simple.

However, as to the practicality of the warning from MFJ. It is a
useful point to depart from, and it is more an issue of insurance
against their having to explain why the tuner melt down when you
didn't follow their advice. However, even as a common guideline, it
fails when compared to other points such as don't load into a full
wave antenna. It follows whatever is halfwave in one band must be
fullwave in another (or nearly so, or even twice so).

So, as undoubtedly all the correspondence that will flow from your
simple question will prove: a simple answer does not satisfy your
need.

Just sit back and follow the reactions your question will elicit, and
read other threads as well. Give this a month and you will begin to
discover the borders to the last frontier of design.

Meanwhile, put up as much wire as you can. Try to tune up. There are
no one antenna solutions, so anticipate having more than one.

73's
Richard Clark, KB7QHC

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands. What bands can I reasonable expect
to transmit on using a 100ft dipole and a tuner?

Make that "all HF bands". 160m is not an HF band.
Also, the dipole must be fed with parallel-line,
ideally open-wire line, for all HF band operation.

W2DU's rule-of-thumb is that a dipole should be
at least 3/8 wavelength on the lowest frequency
of operation.

A 100 ft. dipole can usually be used on 160m,
not as a dipole, but as a Marconi-style fed
system with the transmission line conductors
shorted together and fed against a good radial
ground system.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

On Nov 26, 2:21 pm, Cecil Moore wrote:
James barrett wrote:
My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands. What bands can I reasonable expect
to transmit on using a 100ft dipole and a tuner?

Make that "all HF bands". 160m is not an HF band.
Also, the dipole must be fed with parallel-line,
ideally open-wire line, for all HF band operation.

W2DU's rule-of-thumb is that a dipole should be
at least 3/8 wavelength on the lowest frequency
of operation.

A 100 ft. dipole can usually be used on 160m,
not as a dipole, but as a Marconi-style fed
system with the transmission line conductors
shorted together and fed against a good radial
ground system.
--
73, Cecil http://www.w5dxp.com

I keep reminding myself about the articles I've read about people
using window screens and rain gutters as antennas. ;-) I'll keep
reading and eventually I will understand Antennas. But (there's always
a but) I have to remind myself that my goal is to be able to make
contacts (CW, and eventually phone when I get my General class
license) and for now that means 10m, 15m, 40m and 80m. With that in
mind should my thinking be to put up a dipole for 80m and tune it down
to 10, 15 and 40, or should I go with some other length? Being that we
are near the bottom of the sun spot cycle, which band has the best
chance for making contacts? Maybe I should put up a dipole for that
and then tune it for the others.

If tuning for 160 meters is different than for the HF bands, then I'll
wait until I actually have my General class license before I start
thinking about that.

Jim

using an MFJ-941E tuner on all bands?
 

James barrett wrote:

I keep reminding myself about the articles I've read about people
using window screens and rain gutters as antennas. ;-) I'll keep
reading and eventually I will understand Antennas. But (there's always
a but) I have to remind myself that my goal is to be able to make
contacts (CW, and eventually phone when I get my General class
license) and for now that means 10m, 15m, 40m and 80m. With that in
mind should my thinking be to put up a dipole for 80m and tune it down
to 10, 15 and 40, or should I go with some other length? Being that we
are near the bottom of the sun spot cycle, which band has the best
chance for making contacts? Maybe I should put up a dipole for that
and then tune it for the others.

If tuning for 160 meters is different than for the HF bands, then I'll
wait until I actually have my General class license before I start
thinking about that.

Hey Jim,

Using one of those tuners is very simple. (mostly)

Assuming you are using ladder or window line,(not only a good
assumption, but a good idea) put up as much wire as high as you can.

The "mostly" part is that you don't want the wires to be 1/4 wavelength
total on any of the bands you are going to operate. I think the MFJ
manuals point out some lengths you don't want to use.

All this is to say that if you can put say 96 feet of wire in the air,
that is what you put up. Such an antenna will work a treat on 40 and up,
decently on 80 meters, and almost so-so on 160.

You are ready. Get a couple buds, your slingshot or favorite method of
launching fishing line into the air, and put up that dipole. Run the
window line to the house, avoiding running it too near to metal objects,
say keep it around 4 inches away. Connect it to the balanced line input
on the tuner, go coax to the rig, and there you have it. Make sure you
do the grounding thing correctly, but that's another subject.

- 73 de Mike N3LI -

using an MFJ-941E tuner on all bands?
 

On Mon, 26 Nov 2007 10:47:15 -0800 (PST), James barrett
wrote:

[snip]
My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands. What bands can I reasonable expect
to transmit on using a 100ft dipole and a tuner?

That last part of the warning about using an 80 meter dipole as a
longwire has me totally confused. Are they saying to snip off the
coax connector and plug the ends into the longwire connector in the
back of the tuner?


Jim

P.s. I finally have the 21st edition of the ARRL Antenna book. I'm
only on chapter 2, so please feel free to point out page numbers or
chapters that would probably answer my questions


Jim,

Check this one out.

http://www.degendesigns.com/Downloads/TheEasyWay.PDF

Danny, K6MHE

using an MFJ-941E tuner on all bands?
 

Here's the basic problem: Somewhere along the line you've got to match
the impedance seen at the input of the feedline to the 50 ohm resistive
(50 + j0 ohm) load your transmitter needs to see. (You don't actually
have to get it exact, but reasonably close.) The impedance of a half
wave dipole is in this ballpark all by itself, but other antennas (and
even the dipole if not resonant) usually need some kind of matching. The
farther the impedance at the feedline input is from 50 + j0, the harder
the job for the matching network -- voltages across and/or currents
through the matching network components increase and can become
downright awesome, if the impedance to be matched is far from 50 + j0.

If you start shrinking a dipole to a shorter length than a half
wavelength, or a monopole to shorter than a quarter wavelength, the
resistance drops and the amount of reactance increases. See Fig. 7 on p.
2-5 of the Antenna Book, which shows that a quarter wave dipole has a
feedpoint impedance of around 15 - j1000 ohms. Shorter dipoles have even
lower resistance and larger reactance.

Matching an extreme impedance involves, as I mentioned, high voltages
and/or currents, which is why the MFJ caution. These high voltages and
currents also result in increased loss, sometimes to the point where
most of your power is going to heating the matching system components.

It's entirely possible to use electrically small antennas, but there are
tradeoffs involved. Here are some ways you can do it:

1. Split the matching chore between the tuner and other external
components, such as a loading inductor to reduce the amount of reactance
the tuner has to deal with.
2. Use transmission lines to accomplish some or all of the matching.
This isn't usually the most efficient possible way (contrary to
folklore) but it distributes the heat and voltage gradient. Often you
can use the transmission line to transform an extreme impedance to
another impedance that might also be extreme but within the range a
tuner can more comfortably handle.
3. Use relatively lossy components, even possibly an intentional
resistor, as part of the matching network. This reduces voltages and
currents and increases bandwidth at the expense of some reduction in
radiated power.
4. Reduce power if necessary to keep your tuner from self destructing.

If you make an efficient matching network for an extreme impedance
transformation, it will be very narrow banded, so will require frequent
retuning as you QSY. Lossier systems have broader bandwidth (in
general). Trading loss for bandwidth might be worthwhile depending on
your circumstances. B & W has sold an antenna for decades which
incorporates a resistor, and it's widely used. Browse through the QRP
sites and you'll see that large numbers of QSOs are routinely had by
people running a watt or less. Countless others are undoubtedly made by
people with 100 watt transmitters who are radiating 10 watts without
realizing it. So don't stay off the air just because you can't make an
efficient antenna system. Any radiated power is better than none.

If you have a decent ground system, connecting the two transmission line
conductors of a short dipole together and feeding it against ground
(that is, connect the shorted dipole to the "hot" side of the tuner
output and the ground to the "cold" side) is a good suggestion. What you
have then is a top-loaded vertical, with the radiating vertical being
the feedline and the dipole being the largely nonradiating top hat. But
I wouldn't consider this unless you can bury at least a few radial wires
or lay them on the surface of the ground.

Roy Lewallen, W7EL

using an MFJ-941E tuner on all bands?
 

"James barrett" wrote in message
...

I keep reminding myself about the articles I've read about people
using window screens and rain gutters as antennas. ;-) I'll keep
reading and eventually I will understand Antennas.

Take comfort from the knowledge that sub-optimal antennas, including rain
gutters, are still OK. Until I get a tower up, I am contenting myself with
sub-optimal. Heck, I loaded up an aluminum extension ladder and had a QSO
with Hawaii from San Diego.

This NG had a recent thread on multiband fan dipoles. I made one and it
works fine. I started with a 10m copper pipe dipole a few feet over my
garage roof, coax-fed through a balun. It is parallel to the peak of the
roof.

I added two 20m elements of #16 insulated stranded wire (lamp cord,
actually) and ran them downslope toward opposite corners of the garage roof.
They make about a 45-degree angle with the 10m antenna. Construction
articles encourage separating elements of different bands. The first
measured 20m elements were too long and the SWR dipped at 12-something MHz.
I trimmed them to 14.1 MHz, SWR = 1.1:1 at the radio. The only change to
the 10m performance was a very slight increase in SWR (1.5:1 vs. 1.7:1 per
MFJ-269).

I output only 100 watts and have logged 20m QSO's to Canada, Alaska, Hawaii
and the US East Coast on those hunks of lamp cord laying on my garage roof.
I plan to add some 40m elements and see what happens. ("Let's see what
happens if ... " is one of the very best things about ham radio.)

"Sal"
(KD6VKW)

using an MFJ-941E tuner on all bands?
 

My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands.

I find that set up extremely lossy on 10GHz

Jeff

using an MFJ-941E tuner on all bands?
 

If tuning for 160 meters is different than for the HF bands, then I'll
wait until I actually have my General class license before I start
thinking about that.

Tuning is no different on 160 compared to anywhere else. It is just that the
very long wavelength makes short antennas difficult to match, and be outside
of the range of that particular tuner.

I have about 45' of end-fed wire that I can match on 160m to a low swr with
the auto atu that I have. Of course that does not mean that it makes an
effective antenna, but I can work people on at a push.

73
Jeff

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
... should my thinking be to put up a dipole for 80m and tune it down
to 10, 15 and 40, or should I go with some other length?

An 80m dipole works well on all HF bands. I tune my
80m dipole system by varying the length of the ladder-
line so I don't even need an antenna tuner.

http://www.w5dxp.com/notuner.htm

My favorite bands are 40m and 17m.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

On Nov 26, 7:22 pm, "Sal M. Onella"
wrote:

I added two 20m elements of #16 insulated stranded wire (lamp cord,
actually) and ran them downslope toward opposite corners of the garage roof.
They make about a 45-degree angle with the 10m antenna. Construction
articles encourage separating elements of different bands. The first
measured 20m elements were too long and the SWR dipped at 12-something MHz.
I trimmed them to 14.1 MHz, SWR = 1.1:1 at the radio. The only change to
the 10m performance was a very slight increase in SWR (1.5:1 vs. 1.7:1 per
MFJ-269).



Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

Jim

using an MFJ-941E tuner on all bands?
 

On Nov 27, 3:43 am, "Jeff" wrote:
My naive understanding was that I could hang up a 100ft dipole and use
a tuner to transmit on all bands.

I find that set up extremely lossy on 10GHz

Jeff

Yikes, I don't have anything higher than a 2 meter HT.

using an MFJ-941E tuner on all bands?
 

On Nov 26, 5:16 pm, Danny Richardson wrote:

Jim,

Check this one out.

http://www.degendesigns.com/Downloads/TheEasyWay.PDF

Danny, K6MHE

Hi, I like the article. One question about feed lines. If coax is 50
ohms and twin lead has 300 ohms. Why is the twin lead consideres less
lossy than coax? I had thought that higher ohms meant higher impedance
and I thought higher impedance means higher loss. Obviously I have not
read the chapter on transmission lines yet ;-), so I may have that all
wrong.

Also, in the article, I liked the part about before 1950, no one even
heard about swr, and that antennas with high swr were working just
fine. But I make 2 assumptions: 1) I'm thinking, even if they didn't
know or care about swr, they still had to cut their dipoles for the
band they were transmitting on. 2) I still would not want to use a 10m
dipole and transmit 100 watts on 80 without at least using a tuner. Am
I correct in these assumptions?

using an MFJ-941E tuner on all bands?
 

I just read this article from ARRL:

http://www.arrl.org/tis/info/pdf/9312070.pdf

This is exactly what I want to do. Put up a single dipole that I can
use reasonably well on HF bands. The thing I haven't figured out yet
about ladder line yet is how to bring it in to the house.
My current setup is a 10m dipole with RG58 coax feed line shoved under
the back door. Obviously I can't do that with ladder line (aluminum
door). I think I might get away with drilling two holes in the wall
and putting in connectors, then attach the ladder line to the
connectors. On the other side of the wall.... would I still want to
use ladder line to continue on into the tuner? Or would would I want
to attach a coax at that point from the wall to the tuner? Or maybe I
need to hang my tuner on the wall. :) I'll google around and see
what other people are doing, but I'd like to hear some ideas if anyone
here is using ladder line. (should I change the topic for this
thread?)

Cecil, I love your no tuner ladder line idea. I think someday I'll try
that when I have more experience with feed lines and antennas.


jim

using an MFJ-941E tuner on all bands?
 

On Tue, 27 Nov 2007 07:35:07 -0800 (PST), James barrett
wrote:

Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

Hi Jim,

Adding a new band's element will likely disturb the performance of an
existing one. However, it will be slight, and if you anticipate this,
you can construct a two band antenna and tune both. Similarly, you
can construct three, four, five.... band antennas using similar
principles. There is, of course, the compounding of difficulty as you
increase this count, but that doesn't preclude it being done
successfully.

73's
Richard Clark, KB7QHC

using an MFJ-941E tuner on all bands?
 

On Tue, 27 Nov 2007 07:55:57 -0800 (PST), James barrett
wrote:

Why is the twin lead consideres less
lossy than coax?

Hi Jim,

All loss is in the bulk of the conductor. When comparing the two,
twin lead usually has more bulk = less loss.

I had thought that higher ohms meant higher impedance
and I thought higher impedance means higher loss. Obviously I have not
read the chapter on transmission lines yet ;-), so I may have that all
wrong.

You do. Impedance restricts energy, it doesn't consume it (loss).

Also, in the article, I liked the part about before 1950, no one even
heard about swr, and that antennas with high swr were working just
fine.

This is much the same illusion of climbing into a car with the
speedometer exclusive marked in kM/h and thinking it has great 0-60
acceleration. Everything is just fine (ignorance is bliss).

But I make 2 assumptions: 1) I'm thinking, even if they didn't
know or care about swr, they still had to cut their dipoles for the
band they were transmitting on.

You don't even have to do that now, much less before 1950. Resonance
merely simplifies things and gives you a benchmark for performance. If
you don't have resonance, you accommodate to re-achieve that benchmark
for performance (this is how it is done now, and how it was done
before 1950).

2) I still would not want to use a 10m
dipole and transmit 100 watts on 80 without at least using a tuner. Am
I correct in these assumptions?

That would be a pretty good intuition to proceed along. In this
specific case, you may even stand to lose power with the best of
tuners. Further correspondence will reveal those pitfalls.

73's
Richard Clark, KB7QHC

using an MFJ-941E tuner on all bands?
 

On Tue, 27 Nov 2007 08:54:24 -0800 (PST), James barrett
wrote:

I think I might get away with drilling two holes in the wall
and putting in connectors, then attach the ladder line to the
connectors.

Hi Jim,

Good plan. Check to make sure you don't have foil backed insulation
in the walls that might provide a short circuit path.

On the other side of the wall.... would I still want to
use ladder line to continue on into the tuner?

You can do that.

Or would would I want
to attach a coax at that point from the wall to the tuner?

You can do that too, but it is not a matter of "wanting to."

Or maybe I
need to hang my tuner on the wall.

Only if you can reach it as part of your typical operating behavior.

73's
Richard Clark, KB7QHC

using an MFJ-941E tuner on all bands?
 

On 2007-11-27, James barrett wrote:
I just read this article from ARRL:

http://www.arrl.org/tis/info/pdf/9312070.pdf

This is exactly what I want to do. Put up a single dipole that I can
use reasonably well on HF bands. The thing I haven't figured out yet
about ladder line yet is how to bring it in to the house.
My current setup is a 10m dipole with RG58 coax feed line shoved under
the back door. Obviously I can't do that with ladder line (aluminum
door). I think I might get away with drilling two holes in the wall
and putting in connectors, then attach the ladder line to the

Have the ladder line go to a ferrite bead balun (converts balanced to
unbalanced) and a short piece of coax into the house and directly to the
tuner. (Walt Maxwell's idea) I use this on my 80m loop and it tunes 80-10m
easily.

....Edwin
--
__________________________________________________ __________
"Once you have flown, you will walk the earth with your eyes
turned skyward, for there you have been, there you long to
return."-da Vinci http://bellsouthpwp2.net/e/d/edwinljohnson

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
I just read this article from ARRL:

http://www.arrl.org/tis/info/pdf/9312070.pdf

This is exactly what I want to do. Put up a single dipole that I can
use reasonably well on HF bands. The thing I haven't figured out yet
about ladder line yet is how to bring it in to the house.

Lots of ways. In my house, I made a hole below the window that I can
cover with a plate if I move. Some folks use Plexiglas for one of their
windows and drill holes and make jumpers. IIRC Cecil's web pages have a
nice illustration of that. You won't need as many holes if you make a
regular dipole of course.



My current setup is a 10m dipole with RG58 coax feed line shoved under
the back door. Obviously I can't do that with ladder line (aluminum
door). I think I might get away with drilling two holes in the wall
and putting in connectors, then attach the ladder line to the
connectors.

Yep, that will work.



On the other side of the wall.... would I still want to
use ladder line to continue on into the tuner? Or would would I want
to attach a coax at that point from the wall to the tuner?

Run the ladder line the whole way to the tuner. Some folks put a balun
in line and run coax for the last few feet, but the mfj has a balun
built in.


Or maybe I
need to hang my tuner on the wall. :)

heh, that would be good for excercising!



I'll google around and see
what other people are doing, but I'd like to hear some ideas if anyone
here is using ladder line. (should I change the topic for this
thread?)

Nah, it's pretty much still on topic.

One of the first things though is that there is ladder line, and there
is window line. Most of us use window line, although ladder line has
some advantages. Window line is easier to handle, and should work just
fine for you. It is the poly coated stuff with cut out windows in it-
hence the name.

Cecil, I love your no tuner ladder line idea. I think someday I'll try
that when I have more experience with feed lines and antennas.

My xyl won't let me put one of those in - says it's visually challenged.


- 73 de Mike N3LI -

using an MFJ-941E tuner on all bands?
 

Using one of those tuners is very simple. (mostly)

Assuming you are using ladder or window line,(not only a good
assumption, but a good idea) put up as much wire as high as you can.

The "mostly" part is that you don't want the wires to be 1/4 wavelength
total on any of the bands you are going to operate. I think the MFJ
manuals point out some lengths you don't want to use.

All this is to say that if you can put say 96 feet of wire in the air,
that is what you put up. Such an antenna will work a treat on 40 and up,
decently on 80 meters, and almost so-so on 160.

You are ready. Get a couple buds, your slingshot or favorite method of
launching fishing line into the air, and put up that dipole. Run the
window line to the house, avoiding running it too near to metal objects,
say keep it around 4 inches away. Connect it to the balanced line input
on the tuner, go coax to the rig, and there you have it. Make sure you
do the grounding thing correctly, but that's another subject.
======================
Whatever the length of the dipole ,ensure the the length of 1 half of
the dipole + the length of the 'window feeder' is approx 1 quarter
wavelength of 160m . This will result is a reasonably low impedance at
the matching unit (tuner) , which that unit will happily accept.

Frank GM0CSZ / KN6WH

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

The RF source energy will follow the path of least
impedance. If we have dipole elements for 40m, 30m,
and 20m on the same antenna, when we are on 30m, for
instance, the 30m dipole has a low impedance while
the 40m and 20m dipoles both have high impedances
to the 10.125 MHz source signal. This configuration
can function without a tuner.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
I think I might get away with drilling two holes in the wall
and putting in connectors, then attach the ladder line to the
connectors. On the other side of the wall.... would I still want to
use ladder line to continue on into the tuner?

Some people use side-by-side runs of coax from the tuner
to the outside of the house. The center conductors of the
two runs of coax are used for the parallel lines. The
braids of the coax runs are tied together and grounded.
That alleviates any exposure to bare parallel wires.

Parallel side-by-side runs of 50 ohm coax have a Z0
of 100 ohms. Z0=150 ohms for side-by-side runs
of 75 ohm coax. For low power, side-by-side runs of
RG-62 has a Z0 of 186 ohms.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

On Nov 27, 1:40 pm, Cecil Moore wrote:
James barrett wrote:
Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

The RF source energy will follow the path of least
impedance. If we have dipole elements for 40m, 30m,
and 20m on the same antenna, when we are on 30m, for
instance, the 30m dipole has a low impedance while
the 40m and 20m dipoles both have high impedances
to the 10.125 MHz source signal. This configuration
can function without a tuner.
--
73, Cecil http://www.w5dxp.com

OH, I think I understand... is that what I have heard described as a
spider web antenna.. the elements go off in different directions from
center?

jim

using an MFJ-941E tuner on all bands?
 

Richard Clark wrote:
James barrett wrote:
Why is the twin lead consideres less
lossy than coax?

All loss is in the bulk of the conductor. When comparing the two,
twin lead usually has more bulk = less loss.

The Z0 of the feedline has a lot to do with the I^2*R
losses in the line, one of the main sources of feedline
loss. Ifor = Vfor/Z0, so the higher the Z0, the lower
the current.

Coax has Z0s less than 100. Parallel lines usually have
Z0s greater than 100. That's a major reason that parallel
lines have lower losses.

It is also easier to build parallel lines with lots of
air dielectric, thus reducing dielectric losses.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

Michael Coslo wrote:
James barrett wrote:
Cecil, I love your no tuner ladder line idea. I think someday I'll try
that when I have more experience with feed lines and antennas.

My xyl won't let me put one of those in - says it's visually challenged.

That was my problem in CA which I solved in 1986 by
moving to AZ and leaving the XYL behind. :-)
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

James barrett wrote:
OH, I think I understand... is that what I have heard described as a
spider web antenna.. the elements go off in different directions from
center?

This type of multi-band dipole antenna is called a "fan dipole".
I just did a Google search for "spider web antenna" and that
looks to be something else.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

James barrett wrote:

Hi, I like the article. One question about feed lines. If coax is 50
ohms and twin lead has 300 ohms. Why is the twin lead consideres less
lossy than coax? I had thought that higher ohms meant higher impedance
and I thought higher impedance means higher loss. Obviously I have not
read the chapter on transmission lines yet ;-), so I may have that all
wrong.

Yes, you do. If a line is terminated in a load equal to its
characteristic impedance, the current along the line is sqrt(P/Z0) where
P is the power and Z0 is the line's characteristic impedance. You can
see from this that for a given power, the current is less if Z0 is
greater. From HF through UHF, the loss in a transmission line is
predominantly due to the resistance of the conductors, resulting in loss
proportional to I^2 * R, where R is the RF resistivity of the conductors
including skin effect. So when you increase Z0, it decreases current,
and therefore decreases loss, all else (such as conductor size and
material) being equal. I used a matched line for simplification, but the
lower loss also holds when the line is mismatched.

Also, in the article, I liked the part about before 1950, no one even
heard about swr, and that antennas with high swr were working just
fine.

The beginning of the hams' fetish with SWR corresponds to the
availability of inexpensive meters to measure it. Once it could easily
be measured, it gained a perceived importance way beyond reality.

But I make 2 assumptions: 1) I'm thinking, even if they didn't
know or care about swr, they still had to cut their dipoles for the
band they were transmitting on.

No, they didn't then and they don't now.

2) I still would not want to use a 10m
dipole and transmit 100 watts on 80 without at least using a tuner. Am
I correct in these assumptions?

Yes, that's correct. One thing that *has* changed between then and now
is that rigs used to incorporate a tuner (pi matching network), so often
an external tuner wasn't necessary. Today's rigs don't have this
built-in impedance matching capability.

Roy Lewallen, W7EL

using an MFJ-941E tuner on all bands?
 

On Nov 27, 2:58 pm, Cecil Moore wrote:

That was my problem in CA which I solved in 1986 by
moving to AZ and leaving the XYL behind. :-)

would that be the xxyl? ;-)

using an MFJ-941E tuner on all bands?
 

On Nov 27, 3:06 pm, Cecil Moore wrote:
James barrett wrote:
OH, I think I understand... is that what I have heard described as a
spider web antenna.. the elements go off in different directions from
center?

This type of multi-band dipole antenna is called a "fan dipole".
I just did a Google search for "spider web antenna" and that
looks to be something else.
--

I think I've been doing too much reading, and got my terms confused.
yes, I meant to say fan dipole. :)

using an MFJ-941E tuner on all bands?
 

"Cecil Moore" wrote in message
. net...
James barrett wrote:
Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

The RF source energy will follow the path of least
impedance. If we have dipole elements for 40m, 30m,
and 20m on the same antenna, when we are on 30m, for
instance, the 30m dipole has a low impedance while
the 40m and 20m dipoles both have high impedances
to the 10.125 MHz source signal. This configuration
can function without a tuner.

.... and it does for me on 20 and 10. I don't know how many sets of dipole
elements can be connected at the same time, but I think it's more than the
two I have up there now. Richard gave the number five. That's why I said
I'm going to try a set for 40m.

using an MFJ-941E tuner on all bands?
 

On Wed, 28 Nov 2007 22:54:55 -0800, "Sal M. Onella"
wrote:

... and it does for me on 20 and 10. I don't know how many sets of dipole
elements can be connected at the same time, but I think it's more than the
two I have up there now. Richard gave the number five. That's why I said
I'm going to try a set for 40m.

You are going to give Art apoplexy by crediting me!

Better to back off from my 5 and instead consider:
http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm
which comes to the same thing, but not at the expense of forever
re-tuning each wire by band.

Either way, you have to love stringing wire....

73's
Richard Clark, KB7QHC

using an MFJ-941E tuner on all bands?
 

Sal M. Onella wrote:
... and it does for me on 20 and 10. I don't know how many sets of dipole
elements can be connected at the same time, but I think it's more than the
two I have up there now. Richard gave the number five. That's why I said
I'm going to try a set for 40m.

A fan dipole with elements for 40m and 15m doesn't
work well because of the resonant interaction
between those two elements of 0.5WL and 1.5WL.
Most hams I know use the 40m dipole also for 15m
operation with a tuner.
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

In message , Cecil Moore
writes
Sal M. Onella wrote:
... and it does for me on 20 and 10. I don't know how many sets of dipole
elements can be connected at the same time, but I think it's more than the
two I have up there now. Richard gave the number five. That's why I said
I'm going to try a set for 40m.

A fan dipole with elements for 40m and 15m doesn't
work well because of the resonant interaction
between those two elements of 0.5WL and 1.5WL.
Most hams I know use the 40m dipole also for 15m
operation with a tuner.

It may not work in the same manner as the paralleled dipoles for the
other bands do (ie where only one dipole is active at any one band).
But, of interest, do paralleled 40m and 15m dipoles actually work
'badly' on 15m? Obviously, the feed impedance and the radiation pattern
are likely to be a bit different, but (maybe with a tuner to help tune
things up a bit better) would the overall performance still be poor?
After all, the RF you put into the antenna has to go somewhere (even if
it's not where you expect it to be).
--
Ian

using an MFJ-941E tuner on all bands?
 

Ian Jackson wrote:
But, of interest, do paralleled 40m and 15m dipoles actually work
'badly' on 15m?

When I said it "doesn't work well", I meant that it doesn't
work like a single predictable dipole. If the 40m dipole
soaks up a lot of the RF energy on 15m, the radiation pattern
will not be the predictable figure-8 broadside 1/2WL dipole
pattern. It may be more of a multi-lobed cloverleaf radiation
pattern. If one aims a 40m dipole broadside to the desired
contact point and uses it on 15m, it "doesn't work well".
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

Cecil Moore wrote:
Ian Jackson wrote:

When I said it "doesn't work well", I meant that it doesn't
work like a single predictable dipole. If the 40m dipole
soaks up a lot of the RF energy on 15m, the radiation pattern
will not be the predictable figure-8 broadside 1/2WL dipole
pattern. It may be more of a multi-lobed cloverleaf radiation
pattern. If one aims a 40m dipole broadside to the desired
contact point and uses it on 15m, it "doesn't work well".


What would you consider the best direction to hang a long dipole? I will
be hanging about 135 feet with the ends at east and west. It's the only
direction I have enough room to hang a wire antenna that long.


Jim

using an MFJ-941E tuner on all bands?
 

James Barrett wrote:
What would you consider the best direction to hang a long dipole? I will
be hanging about 135 feet with the ends at east and west. It's the only
direction I have enough room to hang a wire antenna that long.

It depends upon what you want your radiation pattern
coverage to be from your particular QTH. I orient my
130 foot dipole so that my radiation lobes point toward
the world's large land masses on 20m. The free demo
version of EZNEC available from eznec.com will tell you
what direction your lobes are pointing.

The radiation patterns for an east-west 130 foot dipole
can be found on my web page under my notuner all-HF-band
antenna design. The 20m radiation pattern is at
http://www.w5dxp.com/20m.htm
--
73, Cecil http://www.w5dxp.com

using an MFJ-941E tuner on all bands?
 

http://stockton.craigslist.org/ele/488204046.html

JS

using an MFJ-941E tuner on all bands?
 

Cecil Moore wrote:
It depends upon what you want your radiation pattern
coverage to be from your particular QTH. I orient my
130 foot dipole so that my radiation lobes point toward
the world's large land masses on 20m. The free demo
version of EZNEC available from eznec.com will tell you
what direction your lobes are pointing.

I tried using the demo version of EZNEC, but haven't figured it out yet.
I don't really know yet what I want my radiation pattern to be because
I've had an HF radio now for three weeks, and only a 10 meter dipole.
(tuner to be delivered this weekend). Of course I have made no contacts
on 10 meters. I tried CW on 15 meters (yes, on my 10 m dipole with no
tuner, at low power) but no one has answered. Probably because of my
slow wpm. ;-)

Anyways, I'm not sure yet what to expect as far as making contacts.
Would I have a better shot from east or west, or would I have a better
shot north and south?

Well, before I go too far off topic, I read ch. 7 from the ARRL Antenna
book, and I think the best for me as far as antennas go, is the 135 foot
dipole fed with 450 ohm window line, and it will have to go east/west
which means I might be talking to Santa this year! ;-)

So, I guess what I should have asked was, what would be the best
orientation for a dipole in New England in order to make contacts at
this time of year and at this point in the sun spot cycle.

Ok, having said all of that, I have some ideas for shorter dipoles that
can hang north/south. So there is much experimenting in my future. :-D

Busy weekend, be listening for me on cw!


Jim
kb1odg

using an MFJ-941E tuner on all bands?
 

James Barrett wrote:
I tried using the demo version of EZNEC, but haven't figured it out yet.

Time to diagnose that problem. :-)

Anyways, I'm not sure yet what to expect as far as making contacts.

At this low of the sunspot cycle, don't "expect" anything
above 14.35 MHz to work. :-) 40m CW is my favorite band
right now.

Ok, having said all of that, I have some ideas for shorter dipoles that
can hang north/south. So there is much experimenting in my future. :-D

Hang your long dipole E/W. Hang another dipole in parallel
N/S as long as you can make it. Use an antenna tuner. Enjoy,
i.e. put something in the air and be patient.
--
73, Cecil http://www.w5dxp.com