On 08 Jan 2004 21:39:17 GMT, (Desmoface) wrote:

How about a J-Pole? Low angle radiation. The bottom end can be connected to
earth ground. In fact, I constructed one using a mast with the 1/4 wave
parallel section added 1/2 wave below the top. Real easy. No radials.


thats also an option..i wonder if'n I'll need radials with a vertical dipole??

Steve
kb8viv

Hi Steve,

The lower dipole element IS(ARE) the radial(s).

You can follow my former instructions and simply make the upper
portion 5/8ths wavelength (if you have the room). If this makes it
too long (too close to ground) you will need radials. But for 10M
that is getting a little carried away if you can hoist a vertical
dipole.

73's
Richard Clark, KB7QHC

"Desmoface" ... anyone think a verticle dipole
would work. ..a vertical dipole for 10...
Steve kb8viv

How about a J-Pole? ..one using a mast with the 1/4 wave
parallel section added 1/2 wave below the top. Real easy. No radials.
John Smith - KD5YI

As others have already noted, vertical dipoles do work
whether center-fed or end-fed (a.k.a. J-pole) without radials.

As already noted, hang it as high as you can manage
- just the normal advice for any antenna except N.V.I.S.

If you want to pursue the J-pole route,
go to CQ magazine's web site

http://www.cq-amateur-radio.com/

and download George VE3ERP Murphy's freeware HAMCALC
ham radio software package. (lower left corner)
(Download it just for general principles.)
Program about-23 of 250+ programs
is Murph's version of my version of Gary N3GO O'Neill's
J-pole program from his Communication
Quarterly article on end-fed half-wave antennas.
Go to Steve AA5TB Yate's website

http://www.qsl.net/aa5tb/

under "Antennas" for more info and a link
to Gary's article on how J-poles
and Zepps really work versus the popular view.

The program gives starting lengths.
For 28.5 MHz:
Using 300 ohm twinlead:

halfwave radiator wire = 196.7 inches
series matching 300 ohm section = 78.6 inches
to the 50 ohm tap point
shorted shunt stub 300 ohm section = 6.6 inches

Total length is about 23.5 feet if you hang it all up
vertically. The not-quite-quarter-wave matching section
can be horizontal with the halfwave radiator vertical
if you need/want to run it that way.

Gary's article, the program or a Smith chart show
why the commonly used 450 ohm ladder line is not
the as good a choice for matching as 300 ohm.

Have fun. Measure and cut metal and plastic,
hang it up, apply and withdraw RF energy.
Don't just do computer calculations
(as I do most of the time (sigh)).

Cheers, 73,

Ron McConnell



N 40º 46' 57.9" W 74º 41' 21.9"
FN20ps77GU46 [FN20ps77GV75]

http://home.earthlink.net/~rcmcc

On 08 Jan 2004 18:51:02 GMT, (Desmoface) wrote:

Hey kids..I know gap kind of does this..but anyone think a verticle dipole
would work...basically a vertical fed in the center...Im wanting a good 10
meter antenna for local stuff and was thinking about a conventional
vertical..than I thought maybe I could do without the radial system and ground
loss issue but just putting up a vertical dipole for 10...any thoughts??

Steve
kb8viv

Cebic has a whole page of 10-10 antennas:

http://www.cebik.com/a10/anta.html

Bob
k5qwg

"Desmoface" wrote in message
...
How about a J-Pole? Low angle radiation. The bottom end can be connected
to
earth ground. In fact, I constructed one using a mast with the 1/4 wave
parallel section added 1/2 wave below the top. Real easy. No radials.


thats also an option..i wonder if'n I'll need radials with a vertical
dipole??

Steve
kb8viv


As others have replied, no you don't.

I once made a 1/4 wave vertical and was listening to a local conversation on
my IC-2AT when there occured a lightning stroke from a thunderstorm a few
miles away. Although the mast and radials were grounded, the conversation
disappeared for about 5 seconds and then faded back in. Electrical charge on
the ungrounded vertical element. But I have never had this problem with a
J-Pole since all parts of it can be at earth ground. I've also used folded
vertical monopoles with the same results.

In my old age I have probably become paranoid about ungrounded driven
antenna elements. I know that some (maybe all) commercial antennas are
designed with networks or other devices which does the grounding. If I were
to build a simple ground plane today, I would make it a bit shorter than
resonant and add a shunt inductor across the feed point. That way there can
be no static accumulation on the element.

By the way, we sometimes get sand/dust storms here. I have seen and heard
the repeated discharges from the center pin to the shell of a PL-259 on a
RG-8 line coming down from the roof during a sand storm.

Anyway, this is not to convince anyone that a J-Pole is a cure-all or even
the best choice. I just wanted to tell about what drives my choices and tell
about a couple of my experiences. Anything you choose will be just fine, as
long as you are aware of its properties.

Have fun.

John - KD5YI

KB8IV wrote:
"I`m wanting a good 10 meter antenna for local stuff and was thinking
about a conventional vertical...then I thought maybe I could do without
the radial system---."

Good thinking. I worked for an oil and gas company which was assigned a
33 MHz frequency shared with a few others in the same industry but
available to us almost at any location within the U.S.A. We made good
use of the frequency for land mobile operations with dozens of fixed
stations and hundreds of mobile units. It worked very well for the radio
"line-of-sight. Usual FM base station power was 500 watts. The mobiles
were 50 watt units. Higher base station power is justified by noiser
receiving conditions in a mobile.

In our international operations we had many HF installations. Some were
AM and some were SSB.

I made a trip to Bolivia to relocate a HF station from a site which was
being seized by the government to accomodate homeless rural people who
were descending upon La Paz to seek their fortunes. Relocation of the
station was easier said than done but was ultimately successful. We had
offices in La Paz and in Cochabamba and we were drilling in the Chaco
Jungle.

While in Bolivia, I got a request from Argentina. They wanted an
aircraft beacon installed on Tierra del Fuego, local land mobiles that
worked, and radio between Tierra del Fuego and Buenos Aires. Strikes
frequently interrupted normal communications. The Peronistas wanted Juan
Peron back and the strikes were part of their agitation. So, I went to
Argentina.

In Argentina, we had RCA and RCA Radiomarine SSB equipment. Our aircraft
were equipped with Collins equipment which was dependale and our pilots
knew how to use it.

The RCA SSB was a problem. The automobile units had plastic coil forms
which melted in normal service. This was far removed from the equator.
It was near the antarctic and damn cold.

Operations were a problem. Base stations were used to communicate
between land bases, vehicles, boats, and tankers taking on oil we had
found and were producing. Multiple crystals meant operators often
couldn`t communicate because they were often switched to the wrong
channel. They also were mystified by knobs identified as "speech
clarifiers".

Fortunately we had some 5-watt Motorola Handitalkies on our stateside 33
MHz FM frequency, on loan to our Argentine operation.

After I installed the low-frequency aircraft homing beacon, the next
problem was getting reliable communications between our main bases in
Rio Grande and San Sebastian, almost 40 miles apart.

This is a land where hurricane force winds blow nearly every day. The
wind is so prevalent it is relied upon for aircraft operation.
Commercial air service to Rio Grande was cancelled when the wind was
calm as the runways were too short for take-offs and landings in the
calm. Commercial flights used DC-6`s (Aerolineas) and C-46`s (Austral).
Our company flew a DC-3 back and forth between Buenos Aires and Tierra
del Fuego. We had Beechcrafts on the Island.

For line-of-sight we needed elevation for 33 MHz antennas. We had
welders, line pipe, steel handbooks and I had a slide rule. So, I went
to work and produced guyed towers at both ends of the path. They were a
little over 100 feet and I put vertical homemade resonant vertical
centerfed dipoles for 33 MHz at their tops. These were connected by RG-8
with the 5-watt radios in the offices. Voila! We were in business with
full quieting. No bandswitching. No clarifiers. No melted coils in the
Motorolas.

We had a second office in Rio Grande but it didn`t need to talk to San
Sebastian. So I made a short self-supporting line pipe tower for that
office. It was about 30 feet. It too had a vertical dipole and a 5-watt
Motorola Handitalkie. When I made a call on that radio, an oil field
supply company in Midland Texas who shared the frequency came back to
me! We`re talking real DX and it was solid. As has been said, that`s the
way it is when the band is open.

Let me correct a statement in this thread that the loweer dipole element
is a radial. It is not. It is an axial and it radiates. Radials are
supposed to be balanced so that they do not radiate.

It is true that radials provide a 2nd antenna connection as does the 2nd
dipole element. That is where the similarity ends.

For the radio connection with Buenos Aires, the public correspondence
station, Radio Pacheco, seemed to work during telephone strikes. So we
went to work. It operated on certain HF channels. Al Hopson, our chief
pilot in Argentina was also a ham and he had had recognized a
Hallicrafters HT-20 that Glen McCarthy had left behind in the Chaco
Jungle of Bolivia when we bought his consession. Al put the HT-20 away
for safe keeping and asked me if I wanted it. He fetched it for me. I
went to Buenos Aires and visited Radio Boliche, "Barato y chi chi".
While there I bought a 2nd-hand Eddystone receiver that worked good and
was cheap (barato y chi chi just as their slogan said).

Back on the island again, it was out with the slide rule and my precious
copy of Ed Laport`s "Radio Antenna Engineering". When we gave Buenos
Aires a call with that HT-20 connected to that rhombic, we really
rattled their cans. The were very slow to believe that we were so far
away.

We ordered the FM stuff they needed to replace all the SSB crap, and
left them delighted with the improvements already made.

Yes. Centerfed vertical dipoles work fine without radials. They have
nulls at their tip ends which reduce mutual impedance with stuff in
those directions. Centerfed antennas are mostly independent of the earth
at close range when low-angle radiation is considered.

Best regards, Richard Harrison, KB5WZI

Yes. Centerfed vertical dipoles work fine without radials. They have
nulls at their tip ends which reduce mutual impedance with stuff in
those directions.

WOW!! That sounds like the makings of an Indiana Jones story line hehe..Thanks
for the entertaining and informative post..73's de kb8viv..

steve

I wrote:
"Centerfed antennas are mostly independent of earth at close range when
low-angle radiation is considered."

Sorry I left out the word "vertical". Certainly a low horizontal dipole
is not independent of earth, but is closely coupled to the earth.

Best regards, Richard Harrison, KB5WZI

the vertical dipole and radials

Just picture a 1/2 dipole horizontally -- then rotate it 90 degrees (or
stand it on end) -- same antenna -- different polarization.

So this picture should clarify why "No Radials".

The lower end is the other half of the dipole - it radiates in conjunction
with the upper half.

Others have advised you about the radiation from "Radials"

--
73 From The Wilderness Keyboard

But, don't get it up to high. EZNEC shows that when the bottom end is a half
wave length above ground, the TOA goes up over 40 with not much improvement
in gain. The vertical half wave dipole seems to be at it's best a quarter
wave above ground (meaning the bottom end is only 8 feet up on 10). So, the
top insulator should be up about 24-25 feet. When installed at this height,
the TOA is below 20 and the gain is almost the same as the higher version,
roughly 1.4dbi. The antenna does not require radials.


"Keyboard In The Wilderness" wrote in message
news:PCzLb.55730$m83.35174@fed1read01...
the vertical dipole and radials

Just picture a 1/2 dipole horizontally -- then rotate it 90 degrees (or
stand it on end) -- same antenna -- different polarization.

So this picture should clarify why "No Radials".

The lower end is the other half of the dipole - it radiates in conjunction
with the upper half.

Others have advised you about the radiation from "Radials"

--
73 From The Wilderness Keyboard

Jim,

I don't know where you get this from. I just ran EZNEC on a 10 m vertical
dipole with the following results:

A) Bottom at 8 feet, gain at 5 degrees is -2.44 dbi.

B) Bottom at 42 feet, gain at 5 degrees is +2.75 dbi.

If you want to work locals, the greater height will also help to get clear
local obstructions, like small hills

Tam/WB2TT
"Jim Leder" wrote in message
...
But, don't get it up to high. EZNEC shows that when the bottom end is a
half
wave length above ground, the TOA goes up over 40 with not much
improvement
in gain. The vertical half wave dipole seems to be at it's best a quarter
wave above ground (meaning the bottom end is only 8 feet up on 10). So,
the
top insulator should be up about 24-25 feet. When installed at this
height,
the TOA is below 20 and the gain is almost the same as the higher version,
roughly 1.4dbi. The antenna does not require radials.


"Keyboard In The Wilderness" wrote in message
news:PCzLb.55730$m83.35174@fed1read01...
the vertical dipole and radials

Just picture a 1/2 dipole horizontally -- then rotate it 90 degrees (or
stand it on end) -- same antenna -- different polarization.

So this picture should clarify why "No Radials".

The lower end is the other half of the dipole - it radiates in
conjunction
with the upper half.

Others have advised you about the radiation from "Radials"

--
73 From The Wilderness Keyboard