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Old April 21st 04, 06:40 AM
zeno
 
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Hi Richard,

You remind me that I do not understand something. Let's say the
characteristic impedance of this 540' loop is in the neighborhood of 140
ohms in free space, or even as you say closer to even 35 ohms in reality.
Your point was, if I understand correctly, that this is in the ballpark
of 50ohm coax and you suggest it can just as easily be fed into the coax.

But I thought that coax is unbalanced and the point was to go with a
balanced feed line?


I guess I am not understanding the relevant differences between balanced
vs. unbalanced feedlines, and getting the impedance of the the
transmission line close to the impedance of the antenna.

I thought the point of my striving to use balanced ladder line was to
somehow gain something that would be compromised by using coax. I thought
that the the ladder line which might be 488 ohms say is still going to be
a better feedline than using the 50ohm coax. The coax would still then
require a balun, correct? (a 1:1 banlun?).


It is sites like this: http://www.cebik.com/par.html that tend to get
one thinking about this whole diy approach.

My reading and gleaning of websites has me of the opinion (at this point)
that the balanced line with this long loop is better (multi band) than to
feed it with coax.

I believe Cecil has already explained this in terms of the wide range of
actual resistance that may be encountered multi band. (hey, I am just now
learning to talk this lingo....just barely know what I am talking
about....operating intuitively, and with the kindness of strangers.......



Zeno (aka Bill) KG6UHM for the moment.....



Richard Clark wrote:

On Tue, 20 Apr 2004 06:23:13 GMT, zeno wrote:

Any recommendations on a specific type of commercially made window
(ladder) line? I see that it comes in a variety of configurations
and slight differences in Z.

This feed line will be for a full wave 160m loop.


Hi Bill,

You repeatedly characterize this as 160M and given the size and height
- Why do you think you need ladder line when it will in all
probability fit quite nicely into a coax?

In free space, it may show as much as 140 Ohms R; however, within the
cold embrace of earth only 50 feet away, you will barely muster 35
Ohms at resonance.

73's
Richard Clark, KB7QHC


  #62   Report Post  
Old April 21st 04, 06:41 AM
Cecil Moore
 
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zeno wrote:
So you have come to the
conclusion that this wire is the best way to go for balanced feed
line all things considered?


Not the best, but hard to beat for the price and convenience.

So you are predicting eventual unhappiness with #10 bare copper wire
ladder line ...


The solid copper wire usually breaks at the antenna where there
is lots of lateral movement. That can probably be cured by a
rigid center support.
--
73, Cecil http://www.qsl.net/w5dxp



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  #63   Report Post  
Old April 21st 04, 07:36 AM
Richard Clark
 
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On Wed, 21 Apr 2004 05:40:11 GMT, zeno wrote:
You remind me that I do not understand something. Let's say the
characteristic impedance of this 540' loop is in the neighborhood of 140
ohms in free space, or even as you say closer to even 35 ohms in reality.
Your point was, if I understand correctly, that this is in the ballpark
of 50ohm coax and you suggest it can just as easily be fed into the coax.

But I thought that coax is unbalanced and the point was to go with a
balanced feed line?


Hi Bill,

True, but easily answered with a feed line choke (1:1 BalUn) at the
drive point that will render the coax balanced if the load is - being
that close to ground there is every chance that may be debatable.
Again, there is no getting it right the first time out of the box -
you can only put it up and test to see how much you need to change it.

You were planning pulleys right?

I guess I am not understanding the relevant differences between balanced
vs. unbalanced feedlines, and getting the impedance of the the
transmission line close to the impedance of the antenna.


You can build a twin line of 50 Ohms. Takes pretty close spacers, and
you will need a lot if you use bare wire. The wire pairs would be as
close as zip cord. Twisted pair, insulated could do the trick (might
even match the 35 Ohms).

I thought the point of my striving to use balanced ladder line was to
somehow gain something that would be compromised by using coax. I thought
that the the ladder line which might be 488 ohms say is still going to be
a better feedline than using the 50ohm coax.


Well.... Only if you use this as a monobander. As a multibander it
will ALWAYS have SWR, the point of big wire twin lead is that the loss
will be less than if you used the same antenna with coax feeding it.
Coax with big center wire is HUGE and COSTLY for the same loss figures
at the same SWRs met by multiband use.

For 160M band, I would REALLY look for the Archer and put my effort
into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
unbalanced, SWR, no SWR hardly counts for diddly.

The coax would still then
require a balun, correct? (a 1:1 banlun?).


ibid.

It is sites like this: http://www.cebik.com/par.html that tend to get
one thinking about this whole diy approach.

My reading and gleaning of websites has me of the opinion (at this point)
that the balanced line with this long loop is better (multi band) than to
feed it with coax.


True enough. I simply responded to you describing it as a 160M loop.
If it was a dedicated monobander, twin lead is extravagant and forces
unnecessary SWR into the picture.

I believe Cecil has already explained this in terms of the wide range of
actual resistance that may be encountered multi band. (hey, I am just now
learning to talk this lingo....just barely know what I am talking
about....operating intuitively, and with the kindness of strangers.......


Stella! (Oops, wrong "Streetcar").

73's
Richard Clark, KB7QHC
  #64   Report Post  
Old April 21st 04, 08:12 PM
zeno
 
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Richard Clark wrote:

You were planning pulleys right?

yes indeed, lots of pulleys, I only want to be putting up these masts once.


For 160M band, I would REALLY look for the Archer and put my effort
into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
unbalanced, SWR, no SWR hardly counts for diddly.


I am going to meet the archer this weekend at the hamfest in Sonoma. Another
friend is giving me a homebuilt house trailer (quaint gypsy wagon) which I
can park out in the back 40 as an alt. shack which will be close to the
antenna up in the 200' Eucalyptus tree. It is not that I am particularly
excited about 160m (although good to be able to operate there when necessary
I guess), but HEIGHT is everything, right?


I believe Cecil has already explained this in terms of the wide range of
actual resistance that may be encountered multi band. (hey, I am just now
learning to talk this lingo....just barely know what I am talking
about....operating intuitively, and with the kindness of strangers.......


Stella! (Oops, wrong "Streetcar").


Wow, a cinematically (literary) erudite ham, cool....I feel like I am
home.....


Zeno (aka Bill) KG6UHM (until further notice.....)

  #65   Report Post  
Old April 21st 04, 08:33 PM
zeno
 
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Richard Clark wrote:
For 160M band, I would REALLY look for the Archer and put my effort

into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
unbalanced, SWR, no SWR hardly counts for diddly.


OK, the 540' loop will be up as high as I can get it with these telescoping
masts, somewhere between 45-55 feet at each corner. How will this be for
bands other than 160m (either with the Johnson or my Kenwood ATU (+current
type balun)? As mentioned I have the real estate to try several antennas
here. I am curious to find out how the loop will work. I only call it 160m
because of the length of the wire. There were a handful of websites
expressing enthusiasm about this antenna.

Another plan is some kind of antenna on a rotator. Any ideas of how to
engineer some kind of beam (light-weight) or something similar atop one of
these 50' telescoping tv masts? If I am to telescope 4 - ten foot sections,
the antenna and rotator would have to be light. I would have to engineer this
with a crew of buddies holding the guy ropes as the stong person is up ten
feet trying to push up this whole thing into the air a section at a time.
Anyone done this? The motivation here is 1) I have the 50 mast, so economy is
a factor, and 2) the result will look more like some kind of elaborate tv
antenna. A tower out in the front yard might be a bit much in the
neighborhood at this point. I need to test these waters first.



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Old April 21st 04, 09:20 PM
Richard Clark
 
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On Wed, 21 Apr 2004 19:33:03 GMT, zeno wrote:
OK, the 540' loop will be up as high as I can get it with these telescoping
masts, somewhere between 45-55 feet at each corner. How will this be for
bands other than 160m (either with the Johnson or my Kenwood ATU (+current
type balun)? As mentioned I have the real estate to try several antennas
here.


Hi Bill,

Above 80M it should be gangbusters. However, you may wish to look
into Rhombic designs given the vast footprint available to you to
experiment with. This will be more directional, more gain for the 30M
bands and above, so you will want to investigate what direction that
should be (don't guess using a flat map either). It would be roughly
the same shape, only more diamond than haphazard square. Such a
design shouldn't hurt your 160M loop prospects, but would optimize the
higher bands (where formerly you were just going to take what came
with the turf).

With a lot more wire (and work), you could get into the Fish Bone
Array, or a wire Log Periodic Array. Both would, again, be fixed
direction so planning ahead is again seen in the XTAL ball.

I am curious to find out how the loop will work. I only call it 160m
because of the length of the wire. There were a handful of websites
expressing enthusiasm about this antenna.


What choice did they have? Such is the fallacy of testimonial. As
the saying goes, if all you have is a hammer, everything looks like a
nail.

Another plan is some kind of antenna on a rotator. Any ideas of how to
engineer some kind of beam (light-weight) or something similar atop one of
these 50' telescoping tv masts?


That would have to be WARC bands and 10M, probably; otherwise you are
dreaming in technicolor and surround-sound.

73's
Richard Clark, KB7QHC
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Old April 21st 04, 09:43 PM
Cecil Moore
 
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zeno wrote:
Another plan is some kind of antenna on a rotator. Any ideas of how to
engineer some kind of beam (light-weight) or something similar atop one of
these 50' telescoping tv masts?


Check out Worldradio's SD-20 systems at http://www.wr6wr.com
--
73, Cecil http://www.qsl.net/w5dxp



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Old April 21st 04, 09:47 PM
zeno
 
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Hi Richard,

Above 80M it should be gangbusters. However, you may wish to look
into Rhombic designs given the vast footprint available to you to
experiment with. This will be more directional, more gain for the 30M
bands and above, so you will want to investigate what direction that
should be (don't guess using a flat map either). It would be roughly
the same shape, only more diamond than haphazard square. Such a
design shouldn't hurt your 160M loop prospects, but would optimize the
higher bands (where formerly you were just going to take what came
with the turf).


Although I have the acres (7) there are a lot of buildings (old barns etc.),
trees, etc. My antenna planning has to dodge many many obstacles actually. This
is an old chicken ranch and there are building everywhere, then all the trees.
Are you saying that a rhombic could be put up on the same masts more or less
(only one of the masts is potentially moveable, meaning that it would only be
diamond like at one end of the trapezoid. This rhombic would be instead of the
540' loop?

I will look up rhombic in the books and see what gives.



With a lot more wire (and work), you could get into the Fish Bone
Array, or a wire Log Periodic Array. Both would, again, be fixed


I will look these up as well. I don't want to get so complex and over my head
that I will be overwhelmed. Now that I have the call sign of choice, I am ready
to rock and roll.....

-Bill (aka Zeno)

Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet. The old bongo drummer morse
code tapper in me is tickled DAH, DI-DAH, DI-DAH-DAH-DAH is so cool for me for
a variety of esoteric reasons, aside from the fact that it is fun to tap out.
My second choice was my 1953 call K6CCG (also fun to tap, but not as fun as
TAJ, the new call is shorter as well), also I like tango alpha juliet more than
charlie charlie golf.....I don't really own any checkered pants.....

I actually found myself listed in an old 1958 call book, which actually was the
year my old Tech ran out.....

Hopefully I can make up for lost time......

73

Bill, K6TAJ

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Old April 21st 04, 09:52 PM
zeno
 
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roger, tnx Ceece.

I apologize for the Beany reference....I am just elated at getting k6taj.

Cecil Moore wrote:

zeno wrote:
Another plan is some kind of antenna on a rotator. Any ideas of how to
engineer some kind of beam (light-weight) or something similar atop one of
these 50' telescoping tv masts?


Check out Worldradio's SD-20 systems at http://www.wr6wr.com
--
73, Cecil http://www.qsl.net/w5dxp

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Old April 21st 04, 10:12 PM
Cecil Moore
 
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zeno wrote:
Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet.


Now we will have an endless thread of words to match your
TLA (three letter acronym). Transmitting All Joules?
--
73, Cecil http://www.qsl.net/w5dxp



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