wrote in message
ups.com...
On Feb 22, 12:16 am, "Sal M. Onella"
wrote:
It was a bust. :-(

They can be quirky..And the decoupling is pretty critical. I always
preferred
a base fed half wave for those reasons. You still need to decouple for
best
performance, but there are no "coax in the way" issues, etc.. I use a
simple
"gamma loop" feed. IE: single turn coil, and a cap if needed.
Sometimes
you don't need the cap, but if you do, 30-50 pf is about the usual
value for
10m. I make those from a short length of coax.. I'm basically copying
the
feed system of the usual cushcraft ringos.. BTW, cushcraft sells a 10m
ringo if one doesn't want to build one, or have the tubing.

I will try decoupling and also try that feed.

I have several commercial antennas but I tend toward building them myelf. I
learned the hard way about the three types of copper pipe, K, L, & M. Until
I got home and hit google.com, I didn't know to shop for the more economical
Type M and paid premium $$$ for Type L. I don't want to think what Type K
would have cost.

"Sal"

On Feb 23, 12:40 am, "Sal M. Onella"
wrote:
wrote in message

ups.com...





On Feb 22, 12:16 am, "Sal M. Onella"
wrote:
It was a bust. :-(

They can be quirky..And the decoupling is pretty critical. I always
preferred
a base fed half wave for those reasons. You still need to decouple for
best
performance, but there are no "coax in the way" issues, etc.. I use a
simple
"gamma loop" feed. IE: single turn coil, and a cap if needed.
Sometimes
you don't need the cap, but if you do, 30-50 pf is about the usual
value for
10m. I make those from a short length of coax.. I'm basically copying
the
feed system of the usual cushcraft ringos.. BTW, cushcraft sells a 10m
ringo if one doesn't want to build one, or have the tubing.

I will try decoupling and also try that feed.

I have several commercial antennas but I tend toward building them myelf. I
learned the hard way about the three types of copper pipe, K, L, & M. Until
I got home and hit google.com, I didn't know to shop for the more economical
Type M and paid premium $$$ for Type L. I don't want to think what Type K
would have cost.

"Sal"- Hide quoted text -

- Show quoted text -

Sal, I would like to know how it works with the PVC as I have tried it
on exactly this type of antenna and it worked horribly. Apparently the
PVC I was using has some really lousy dielectric qualities, This stuff
would melt in a microwave while other PVC pipes do not.. I understand
that all PVC is not created equally and that some may be OK. To get
mine to work I used larger pipe, smaller coax, and a different
insulating material but my original was identical to your first
attempt. Unfortunately for me I made all the changes at once and
really dont know which fixed the problem except that the PVC was an
issue. I am very interested in finding whether or not just adding the
choke fixed the problem because this is also something I forgot to do
on my intial attempt. Second attempt had one of those chokes from
"Wireman" made of a length of coax and ferrite beads. One thing that
concerned me even after the antenna was working is the the SWR
appeared to be a little too good. It was 1.2:1 in the middle of 10
meters and never got ave 1.7:1 even at the band edges. I thought that
this is a little too good to be true..

Jimmie

"JIMMIE" wrote in message
oups.com...


snip

One thing that
concerned me even after the antenna was working is the SWR
appeared to be a little too good. It was 1.2:1 in the middle of 10
meters and never got ave 1.7:1 even at the band edges. I thought that
this is a little too good to be true..

My concern, too, for the same reason but the readings appear to be
authentic. For check, I tried the modified antenna (coax not running
through the lower element) on a few other bands with very, very low power
and got terrible VSWR readings. I get about a 1.4:1 at the low end of the 10
band, dropping to a 1.1:1 near the top of the band. I believe having big,
fat elements helps.

Due to cable loss, my measured VSWR at the transceiver is a skosh better
than what I would see at the antenna. A nice chart in the ARRL Antenna Book
shows that with 1 dB cable loss (approximate for 100' of RG-8), my 1.4:1
VSWR measured at the radio is actually closer to 1.6 at the antenna. Still a
keeper. I went on the air last night with a few watts and got a great
signal report from a local ham, so the antenna is working.

"Sal"
(KD6VKW /AE)

Sal M. Onella wrote:
"JIMMIE" wrote in message
oups.com...


snip

One thing that
concerned me even after the antenna was working is the SWR
appeared to be a little too good. It was 1.2:1 in the middle of 10
meters and never got ave 1.7:1 even at the band edges. I thought that
this is a little too good to be true..

My concern, too, for the same reason but the readings appear to be
authentic. For check, I tried the modified antenna (coax not running
through the lower element) on a few other bands with very, very low power
and got terrible VSWR readings. I get about a 1.4:1 at the low end of the 10
band, dropping to a 1.1:1 near the top of the band. I believe having big,
fat elements helps.

Due to cable loss, my measured VSWR at the transceiver is a skosh better
than what I would see at the antenna. A nice chart in the ARRL Antenna Book
shows that with 1 dB cable loss (approximate for 100' of RG-8), my 1.4:1
VSWR measured at the radio is actually closer to 1.6 at the antenna. Still a
keeper. I went on the air last night with a few watts and got a great
signal report from a local ham, so the antenna is working.

"Sal"
(KD6VKW /AE)




A year or two ago I was into playing with various monopole designs for
10 meters and greater freqs.

The bazooka I built and liked was a stainless steel whip for the
radiator. The bazooka sleeve was hook to coax and the mast--at the
sleeve where the bottom of the radiator was mounted on a teflon block
insulator. The sleeve was either 1-1/8 or 1-3/8 copper pipe.

The antenna was fed at the top of the sleeve where the radiator exited,
with a 1:1 current balun on a toroid core. The balun was able to handle
100+ watts and I drove it at 100 W.

The swr was below 1.5:1 on most of the ten meter band, I don't believe
it was ever above 2:1, if memory now serves me correct.

The antenna was ok. However, a 1/2 monopole with a gamma feed is what I
finally settled on and still run today. Benefit is that this antenna
requires a minimal counterpoise for excellent performance and radiation
pattern and ease of construction.

Regards,
JS

"John Smith" wrote in message
...

snip

However, a 1/2 monopole with a gamma feed is what I
finally settled on and still run today. Benefit is that this antenna
requires a minimal counterpoise for excellent performance and radiation
pattern and ease of construction.

Regards,
JS


I need to learn more aboout matching. I picked up the 1989 edition of
ARRL's ANTENNA IMPEDANCE MATCHING at the swap meet a few years ago, but I
really haven't taken the time to dig into it.

I'm starting to think in terms of Smith charts, which I never thought I
would need or use. Surprise!

Sal M. Onella wrote:
I'm starting to think in terms of Smith charts, which I never thought I
would need or use. Surprise!

Carrying a Smith Chart around in your head is a
good way to conceptualize transmission line and
antenna configurations.
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
...
Sal M. Onella wrote:
I'm starting to think in terms of Smith charts, which I never thought I
would need or use. Surprise!

Carrying a Smith Chart around in your head is a
good way to conceptualize transmission line and
antenna configurations.
--
73, Cecil http://www.w5dxp.com

Yes. I have seen a lot of Smith charts for broadband Navy shipboard
antennas. The people who match them obviously have to do a chart for the
raw antenna in place on the ship, then design and adjust a matching network,
followed by a chart of the results, with every point inside the 3:1 (or 4:1)
circle. Their efforts are generally documented in the ships' antenna files.

I agree about the Smith chart for conceptualizing but at this stage, I am
just a Smith baby.

Back on topic, I am using the sleeve in a conventional dipole configuration
until I can take the time to apply the ideas presented in this NG. I
noticed this afternoon that coiling four turns of decoupling loop a few feet
from the feed actually raised the VSWR, which I didn't understand. Also,
where the coax hangs down next to the antenna makes a difference in the
VSWR, so obviously the line is not "flat" and is instead part of the
antenna. (Do we still use the term "flat" to describe a transmission line
which is properly matched to the load? I recall it from Navy training more
than 40 years ago.) My first HF antenna works, but it's clearly no marvel.