In article , Richard Clark
writes:

On 10 Apr 2004 14:59:24 GMT, PAMNO (N2EY) wrote:
That's quite understandable, given that the original Lattin designed used
tubular Twin Lead and countd on a velocity factor of 0.8.

What sort of test gear and design methods did you folks use?

Hi Jim,

This hard to accept given the timelines offered by those who have
reported the references. For one, the antenna was invented in the
late 40's and patented 26 Dec. 1950, and reported in 1960. ALL such
dates precede the introduction of tubular Twin Lead in the mid 60s.

Hello again!

Direct quotes from the 1960 QST article:

"If open line with a velocity factor near unity is used for the stubs, the
over-all lenght for a two-band antenna would be nearly a full free-space
wavelength at the higher frequency and and the whole antenna would resonate at
something less than half that frequency. Very fortunately, the the velocity
factor of 300-ohm tubular Twin-Lead (0.8) gives such lenghts for the stubs that
that, in most cases, the adding the stub makes the antenna resonate at just
half the original frequency."

"Fig. 3 shows how tubular Twin-Lead can be used for the antenna itself as well
as the stubs and includes dimensions for 10- and 20-meter operation. The
foam-filled type of Twin-Lead is recommended to keep out moisture."

So it must have existed when W4JRW wrote the article, some time before the
December 1960 QST went to press.

In addition, my 1953-54 RESCO (Radio Electronic Service Company, once a great
source of all things radio and TV here in the Philly area) catalog lists
Amphenol "flat and tubular Twin Lead". The tubular stuff is number 14-271 and
was 5 cents a foot - less in quantities of 100, 500 or 1000 feet. And it wasn't
a new item.

All of this supports both your experiences and those of others. If the exact
characteristics of tubular Twin Lead are important to the design, it's no
wonder that the reported results cannot be obtained.

One more point. The SWR graphs shown for the 5 band version show quite narrow
SWR bandwidths. If anyone is interested I can report them in a future post.

73 de Jim, N2EY

N2EY wrote:
"Fig. 3 shows how tubular Twin-Lead can be used for the antenna itself as well
as the stubs and includes dimensions for 10- and 20-meter operation. The
foam-filled type of Twin-Lead is recommended to keep out moisture."

Jim, I haven't been following very closely. Is it possible to describe
this antenna with an ASCII diagram. Apparently on one band, the stub
is installed at the 1/50 conductance circle to SWR circle intersection.
--
73, Cecil, W5DXP



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Cecil Moore wrote:
Jim, I haven't been following very closely. Is it possible to describe
this antenna with an ASCII diagram. Apparently on one band, the stub
is installed at the 1/50 conductance circle to SWR circle intersection.

Never mind, I found the information at:
http://www.g3ycc.karoo.net/lattin.htm
--
73, Cecil, W5DXP



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On 10 Apr 2004 18:25:04 GMT, PAMNO (N2EY) wrote:
All of this supports both your experiences and those of others. If the exact
characteristics of tubular Twin Lead are important to the design, it's no
wonder that the reported results cannot be obtained.

One more point. The SWR graphs shown for the 5 band version show quite narrow
SWR bandwidths. If anyone is interested I can report them in a future post.

Hi Jim,

I stand corrected on the tubular twin lead (must've died in the
mid-60s then).

It offers nothing substantially different to the physics of design
however, just a different velocity factor which is scalable to suit
any implementation.

However, my data to this point confounds the "theory" of it all by
exhibiting stubs that do NOT resonate at their computed length
(complete with correction for ANY velocity factor commonly observed).

More data is always appreciated.

73's
Richard Clark, KB7QHC

In article , Richard Clark
writes:

On 10 Apr 2004 18:25:04 GMT, PAMNO (N2EY) wrote:
All of this supports both your experiences and those of others. If the exact
characteristics of tubular Twin Lead are important to the design, it's no
wonder that the reported results cannot be obtained.

One more point. The SWR graphs shown for the 5 band version show quite
narrow
SWR bandwidths. If anyone is interested I can report them in a future post.

Hi Jim,

I stand corrected on the tubular twin lead (must've died in the
mid-60s then).

No biggie. I did not expect to find it in the 1953 catalog, but there it was,
and not a new item either.

Probably unobtanium now.

It offers nothing substantially different to the physics of design
however, just a different velocity factor which is scalable to suit
any implementation.

Lattin seemed to think it was important. Do you have the 1960 QST article?

However, my data to this point confounds the "theory" of it all by
exhibiting stubs that do NOT resonate at their computed length
(complete with correction for ANY velocity factor commonly observed).

More data is always appreciated.


Well, here's the info from the 1960 QST article.

Dipole dimensions:

Innermost section (not a stub; shorted at both ends): 8'
Next section (stub; open at inner end): 6' 11" [resonant at 10 meters?]
Next section (stub, open at inner end): 13' 10" [resonant at 20 meters?]
Outermost section (stub, open at inner end): 27' 5" [resonant at 40 meters?]

Entire antenna 57' 2" per side (plus connections)

SWR, 50 ohm coax, coax length not given (all numbers guesstimated from graph):

80 meters:
Minimum SWR: 3725 kHz - 1.1:1
2:1 SWR points: 3625 & 3800 kHz (175 kHz)
SWR at 3500: 5:1
SWR at 4000: 4.5:1

40 meters:
Minimum SWR: 7225 kHz - 1.6:1
2:1 SWR points: 7150 & 7275 kHz (125 kHz)
SWR at 7000: Off end of scale (5:1 at 7075 kHz)
SWR at 7300: 3:1

20 meters:
Minimum SWR: 14250 kHz - 1.3:1
2:1 SWR points: 14100 & 14375 kHz (275 kHz)
SWR at 14000: 3.5:1
SWR at 14350: 1.8:1

10 meters:
Minimum SWR: 28600 - 1.6:1
2:1 SWR points: 28500 & 28750 kHz (250 kHz)
SWR at 28900: 3:1

Chart for 10 meters covers 28500 to 28900 only. No chart for 15 meters but text
says it will work there on 3/2 wavelength resonance of 40 meter section and SWR
of not less than 3:1.

Note how tight the 2:1 SWR points are, even on the higher bands.

--

Also described is an 80/40 dipole. Inner section is 28' and shorted both ends,
outer stub section is 27' 5". Interesting feature of this one is that in order
to achieve 40 meter resonance there are pieces of wire 2' 6" long hung from the
junction of the two sections. The text and diagram say the outer section
resonates on 40 but the inner section has to be kept at 28 feet or the 80 meter
resonance will be too low.

--

Seems to me that the classic W3DZZ trap dipole would be a lot less aggravation
to model and get working, plus more flexible in choice of minimum SWR points.
Particularly if additional "resonance wires" were added if needed. Certainly
easier to make mechanically strong traps than stubs, and adjusting single wire
lengths with Burndys is a lot easier than fooling with tubular Twin-Lead.

73 de Jim, N2EY

N2EY wrote:
Innermost section (not a stub; shorted at both ends): 8'

No wonder it didn't work on EZNEC. The web page I referenced
had that as a stub.
--
73, Cecil, W5DXP



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On 11 Apr 2004 00:59:23 GMT, PAMNO (N2EY) wrote:

Lattin seemed to think it was important. Do you have the 1960 QST article?

Hi Jim,

No, but hopefully Irv will rectify that.

Well, here's the info from the 1960 QST article.

I will keep those numbers close by, thanx.

73's
Richard Clark, KB7QHC

N2EY wrote:
Dipole dimensions:
Innermost section (not a stub; shorted at both ends): 8'
Next section (stub; open at inner end): 6' 11" [resonant at 10 meters?]
Next section (stub, open at inner end): 13' 10" [resonant at 20 meters?]
Outermost section (stub, open at inner end): 27' 5" [resonant at 40 meters?]

Is this just an attempt at a trapped antenna using stubs for traps?
It doesn't seem to model out to be very functional. The outermost
stub on 40m needs to have a very high impedance, i.e. 1/4WL shorted.
That works well to resonate the vertical on 40m, but 1/8WL on 80m
makes the antenna resonant at 3 MHz according to EZNEC.
--
73, Cecil, W5DXP



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Cecil Moore wrote in message ...
N2EY wrote:
Dipole dimensions:
Innermost section (not a stub; shorted at both ends): 8'
Next section (stub; open at inner end): 6' 11" [resonant at 10 meters?]
Next section (stub, open at inner end): 13' 10" [resonant at 20 meters?]
Outermost section (stub, open at inner end): 27' 5" [resonant at 40 meters?]

Is this just an attempt at a trapped antenna using stubs for traps?

That's exactly what it looks like to me, Cecil. That's also how its
operation is explained in the article. Why a stub that is excited
along its length should behave as a trap is not explained, nor how the
shortened sections act as loading coils (the entire antenna is only
112' 4" long, plus connections).

Note that the antenna works as follows:

10 meters: 6'11" sections act as open circuits so that 8' sections
function as dipole.

20 meters: 13'10" sections act as open circuits so that 8' plus 6'11"
sections function as dipole.

40 meters: 27'5" sections act as open circuits so that 8' plus 6'11"
plus 13'10" sections function as dipole.

80 meters: Entire antenna functions as dipole.

15 meters: 27'5" sections act as open circuits so that 8' plus 6'11"
plus 13'10" sections function as dipole on 3/2 wavelength resonance.

It doesn't seem to model out to be very functional.

Modeling the thing looks like a real challenge for a whole bunch of
reasons. The gaps between sections may be important, for example.

The outermost
stub on 40m needs to have a very high impedance, i.e. 1/4WL shorted.
That works well to resonate the vertical on 40m, but 1/8WL on 80m
makes the antenna resonant at 3 MHz according to EZNEC.

Lattin's results prove that it is *possible*, so your model obviously
needs work to agree with physical reality. But whether the Lattin
antenna is worth all the effort and mechanical troubles is another
story.

The antenna described is a dipole rather than a vertical, but the same
principles apply.

I suspect that a key element to the antenna's operation is the use of
the tubular Twin-Lead, with its 0.8 velocity factor. This stuff is
probably close to being unobtanium these days. Another point is the
extreme narrowness of resonance on most bands.

The W5GI antenna seems to be a variation on the Lattin theme.

For all that trouble, it seems to me that a better choice (if you want
direct coax feed on the non-WARC HF bands) is the classic W3DZZ trap
dipole. With only two traps and mechanically robust construction it is
possible to achieve direct coax feed and low SWR on 80/40/20/15/10,
and the cut-and-try is much easier.

73 de Jim, N2EY

N2EY wrote:
The W5GI antenna seems to be a variation on the Lattin theme.

He says nobody has been able to model or explain why the
antenna works. KA8NCR over on qrz.com says it's lossy
on receive compared to a resonant dipole and about the
same as a trap dipole. I think this is the thread:

http://www.qrz.com/cgi-bin/ikonboard...=6015 8;st=10

Looking at the W5GI antenna, it would seem that reflections
from the ends of the antenna would flow towards the feedpoint
on the coax braid due to skin effect and encounter an open
circuit. If one sent a TDR pulse toward the end of the antenna
from the feedpoint, what do you suppose one would see coming
back?
--
73, Cecil http://www.qsl.net/w5dxp