PDA

View Full Version : Interesting Cloud Burner Antenna


William Taylor
June 11th 05, 07:39 AM
http://www.hamuniverse.com/supernvis.html

The claim is that a dipole 7 feet off the ground has
a 10db gain over a G5RV at 50 feet.

Is that possible, or hype?

Cecil Moore
June 11th 05, 02:53 PM
William Taylor wrote:

> http://www.hamuniverse.com/supernvis.html
>
> The claim is that a dipole 7 feet off the ground has
> a 10db gain over a G5RV at 50 feet.
>
> Is that possible, or hype?

It's could be true for 30m or 10m. Certainly not true
for the bands for which the G5RV was originally
intended namely 80m, 40m, and 20m. 12m comes as a
bonus.

You can make a G5RV just about as good as a dipole
on all HF bands.
0'-16' 20'
xmtr---coax---+---LLLS---+---450 ohm LL---+-102' dipole

The key is the LLLS, ladder-line length selector that
allows selection of 0'-16' in increments of one foot.
It requires four 4PDT relays, like the Omron LY4.
The relays are controlled from the operating position
but auto-switching would be easy to implement with a
directional coupler and a couple of op-amps. The
largest loop of ladder-line is only 2.5' in diameter.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Fred W4JLE
June 11th 05, 02:59 PM
Anecdotal evidence. First note he says 160 meter G5RV, one could assume he
has doubled the size to 204 feet to meet this claim. Run a 204 foot dipole
through EZNEC on 40 and you can see why the claims may be valid in some
directions.

"William Taylor" > wrote in message
...
> http://www.hamuniverse.com/supernvis.html
>
> The claim is that a dipole 7 feet off the ground has
> a 10db gain over a G5RV at 50 feet.
>
> Is that possible, or hype?
>

Cecil Moore
June 11th 05, 03:26 PM
Fred W4JLE wrote:

> Anecdotal evidence. First note he says 160 meter G5RV, one could assume he
> has doubled the size to 204 feet to meet this claim. Run a 204 foot dipole
> through EZNEC on 40 and you can see why the claims may be valid in some
> directions.

I didn't look at it but just noticed 'nvis' in the title.
Of course, a dipole at 7 feet will have near-vertical gain
over a G5RV at 50 feet. Near-vertical gain is NOT what the
majority of hams desire. Near-vertical gain is the antithesis
of DX.

> "William Taylor" > wrote in message
> ...
>
>>http://www.hamuniverse.com/supernvis.html
>>
>>The claim is that a dipole 7 feet off the ground has
>>a 10db gain over a G5RV at 50 feet.
>>
>>Is that possible, or hype?

--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Ed
June 11th 05, 08:24 PM
> I didn't look at it but just noticed 'nvis' in the title.
> Of course, a dipole at 7 feet will have near-vertical gain
> over a G5RV at 50 feet. Near-vertical gain is NOT what the
> majority of hams desire. Near-vertical gain is the antithesis
> of DX.
>


I differ on that opinion. My 40M/80M operational preferences are
definitely for close-in communications, such as getting on the Noon-Time
net, various in-state 75M nets, and other "local" activities". The lower
noise factor of the NVIS antenna helps, too. Of course, its best to have
two antennas, one such as NVIS and another well placed dipole, for optimum
choice.


Ed K7AAT

John Smith
June 11th 05, 08:33 PM
.... personally, I apply a little sticker of an arrow on each antenna I
build...

.... hey it can't hurt!!! <grin>

John

"William Taylor" > wrote in message
...
> http://www.hamuniverse.com/supernvis.html
>
> The claim is that a dipole 7 feet off the ground has
> a 10db gain over a G5RV at 50 feet.
>
> Is that possible, or hype?
>

Cecil Moore
June 11th 05, 09:00 PM
Ed wrote:

>>I didn't look at it but just noticed 'nvis' in the title.
>>Of course, a dipole at 7 feet will have near-vertical gain
>>over a G5RV at 50 feet. Near-vertical gain is NOT what the
>>majority of hams desire. Near-vertical gain is the antithesis
>>of DX.

> I differ on that opinion. My 40M/80M operational preferences are
> definitely for close-in communications, such as getting on the Noon-Time
> net, various in-state 75M nets, and other "local" activities". The lower
> noise factor of the NVIS antenna helps, too. Of course, its best to have
> two antennas, one such as NVIS and another well placed dipole, for optimum
> choice.

What are you disagreeing with? How much DX do you work with
your NVIS antenna? Do you really think the majority of hams
are only interested in local communications on HF?
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Ed
June 11th 05, 09:25 PM
>
> What are you disagreeing with? How much DX do you work with
> your NVIS antenna? Do you really think the majority of hams
> are only interested in local communications on HF?

I guess my disagreement was with the word "majority"... but then, I was
thinking of 75M/40M and not the higher bands. I would say on the two bands
I meant to restrict my comments too, that more hams probably do communicate
"locally" rather than hunt DX.


Ed

Terry O'Neill
June 12th 05, 02:25 AM
I used an antenna quite similar to this (mine had only one ground reflector)
for local (within 300 miles) 40 meter ssb. Mine was at about 16' high.
About 1/8 wl on 40. It was consistently 2-3 s units better than the the high
(70') 40 meter dipole when working stations within about 300 miles. 300-1000
miles they were very close. For DX the high dipole was always better.

Here's a good web site that explains the phenomema

http://www.athensarc.org/nvis.htm




"William Taylor" > wrote in message
...
> http://www.hamuniverse.com/supernvis.html
>
> The claim is that a dipole 7 feet off the ground has
> a 10db gain over a G5RV at 50 feet.
>
> Is that possible, or hype?
>

Korbin Dallas
June 12th 05, 03:17 PM
On Sat, 11 Jun 2005 15:00:18 -0500, Cecil Moore wrote:

> Ed wrote:
>
>>>I didn't look at it but just noticed 'nvis' in the title.
>>>Of course, a dipole at 7 feet will have near-vertical gain
>>>over a G5RV at 50 feet. Near-vertical gain is NOT what the
>>>majority of hams desire. Near-vertical gain is the antithesis
>>>of DX.
>
>> I differ on that opinion. My 40M/80M operational preferences are
>> definitely for close-in communications, such as getting on the Noon-Time
>> net, various in-state 75M nets, and other "local" activities". The lower
>> noise factor of the NVIS antenna helps, too. Of course, its best to have
>> two antennas, one such as NVIS and another well placed dipole, for optimum
>> choice.
>
> What are you disagreeing with? How much DX do you work with
> your NVIS antenna? Do you really think the majority of hams
> are only interested in local communications on HF?

Yes the majority of hams are indeed interested in Local HF communications
on 80 & 40. Something that will reliably commutate out to 300-400
miles.

When they think of DX they think 20 - 10 meters.

Those that are interested in DX on 80 meters are a very small minority.


--
Korbin Dallas
The name was changed to protect the guilty.

Cecil Moore
June 12th 05, 04:07 PM
Korbin Dallas wrote:
>>What are you disagreeing with? How much DX do you work with
>>your NVIS antenna? Do you really think the majority of hams
>>are only interested in local communications on HF?
>
> Yes the majority of hams are indeed interested in Local HF communications
> on 80 & 40. Something that will reliably commutate out to 300-400
> miles.

They can get that from a 40 ft. high G5RV. No 7' high
NVIS dipole is needed. AND you can work DX on 20m-10m
with that 40 ft. high G5RV. I repeat, the majority of
hams are NOT interested *only* in local communications
on HF. A 7' high dipole is a poor performer on 20m-10m.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Ed
June 12th 05, 08:37 PM
> They can get that from a 40 ft. high G5RV. No 7' high
> NVIS dipole is needed. AND you can work DX on 20m-10m
> with that 40 ft. high G5RV. I repeat, the majority of
> hams are NOT interested *only* in local communications
> on HF. A 7' high dipole is a poor performer on 20m-10m.


Cecil, since I started this thread with a comment on yours, in retrospect
I will admit what you say above is true! My comment applied to a small
particular group of operators on the lower bands (or is that higher bands?)



Ed K7AAT

Cecil Moore
June 13th 05, 12:07 AM
Ed wrote:
> My comment applied to a small
> particular group of operators on the lower bands (or is that higher bands?)

The top band is considered to be 160m so I assume "band" is
associated with wavelength, e.g. "160m band". So it appears
that higher bands = lower frequencies, but I could be wrong.
The IEEE Dictionary is no help. It thinks a "band" is a
track on a rotating memory device. :-)
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

[email protected]
June 13th 05, 05:07 AM
What are you disagreeing with? How much DX do you work with
your NVIS antenna? Do you really think the majority of hams
are only interested in local communications on HF?

Some are...Most work only the low bands...I know many
hams who couldn't care less about dx. They only talk to
other regional "good ole boys"....
But saying that, comparing a G5RV at 50 ft, against a
dipole at 7 ft, is fairly silly. The NVIS qualities are more
due to height above ground per wavelength, than the
length of the antenna.
Overall, I think the idea of running low dipoles, or using
ground screens, and pseudo "reflectors" etc, are
generally a waste of time.. If I were working NVIS on 75m,
I'd prefer a dipole at 50ft over one at 7 ft. It will have lower
ground losses, and I'd be willing to bet the NVIS performance
would be just as good as the low antenna. But, the medium
range performance would be a good bit better. Also, you
can work dx also...I've worked dx on 75m, using a dipole
at 35 ft...It's no big deal really...Just finding the DX to talk to
is more difficult. Also...NVIS antennas are not low noise,
unless they are defective in some way...They may reduce
the reception of far off lightning, if that static arrives at
low angles.. A low dipole has great reception of noise...
Straight up....A low to medium height dipole already has
enough gain straight up. I don't really want to enhance it
further...I also want to have decent performance on longer
paths...Listen to all the BIG strappers on 75m...I bet very few
are running real low dipoles with screens...Most will be running
higher dipoles hung from towers, trees, etc...
MK

Ed
June 13th 05, 05:40 AM
> What are you disagreeing with? How much DX do you work with
> your NVIS antenna? Do you really think the majority of hams
> are only interested in local communications on HF?

As you may have missed previously, my comments were directed from the
standpoint of a 75M/40M operator. Personally, I don't consider a NVIS
antenna a valid antenna above those bands. So, for the two bands I have in
mind, Yes, I believe the majority of operators there are interested in
local/intra-state communications.


Ed

Buck
June 13th 05, 05:57 AM
On Sat, 11 Jun 2005 06:39:12 GMT, William Taylor
> wrote:

>http://www.hamuniverse.com/supernvis.html
>
>The claim is that a dipole 7 feet off the ground has
>a 10db gain over a G5RV at 50 feet.
>
>Is that possible, or hype?


I'll take a stab at it. First of all, its objective is to create
nulls at low-take-off angles so shortwave broadcast stations will not
have so much noise. The antenna is a 300 ohm folded dipole that is
fed with 50 ohms but then the antenna has a reflector on the ground.
It is effectively a 2-element yagi pointed strait up (give or take a
few degrees at the user's choosing.)

I don't think a two element beam has a 10 db gain, but I don't know
the gain of a G5RV on the same frequency. Presumably, the signal
strength of local signals will improve and DX or broadcast stations
will drop.

This is known as a Near Vertical Incidence (I forget the 's') antenna.
Great for operating local districts on 160-30 meters. If the dipole
is raised high enough, it will be just a dipole, but then it will be
mis-matched to the feedline and have considerable loss.

This is my theory, correct me if I am wrong

--
73 for now
Buck
N4PGW

Google