OK...I've got to ask...Comet CHA-250B vertical

[Wayne]

-3.5 to 57 Mhz with 1.6:1 or less SWR
-No tuner required
-No radials
-No traps
-No coils
-23.5 feet long

Question: What's in the magical lump at the bottom of the radiator?
Resistor?

Wayne
-W5GIE

[Bert]

In news:jh6a8v$sbb$1...@dont-email.me "Wayne" <mygarb...@verizon.net>
wrote:

> Question: What's in the magical lump at the bottom of the radiator?
> Resistor?
>

The short review in Feb 2006 QST says:

According to Comet, the matching circuit is basically a network
of resistors and capacitors. A toroid balun is present as well.

It also says:

The CHA-250B’s performance is mediocre
to poor on 80, 40 and 30 meters, but it does
an adequate job on the other bands. At a list
price of $469, this is hardly an inexpensive
antenna. Frankly, a small antenna tuner, a
length of 450-Ù ladder line and a wire dipole
will yield superior performance at less than
half the price.

But:

In circumstances where choices are extremely
limited and cost isn’t a major consideration,
the Comet CHA-250B may be a contender,
especially if the alternative is not getting on
the air at all. In addition, the CHA-250B may
also be a viable option in emergencies when
you need a multiband HF antenna that can be
deployed in a matter of minutes. In those situations
you just want to get a signal on the air,
not work the world.

--
Bert Hyman W0RSB St. Paul, MN be...@iphouse.com

[Wayne]

"Bert" wrote in message
news:Xns9FF67BC3D33...@216.250.188.140...

Bert Hyman W0RSB St. Paul, MN be...@iphouse.com

***********************
-
I'm somewhat skeptical of the claims at lower frequencies, particularly with
my recent experiments with tuner loaded verticals.

The current experiment is a 14 foot long vertical (on a flat metal roof) fed
with 25 feet of RG-8 and a tuner at the rig. It does work quite well on
20-10 meters, but not below 20 meters.

Wayne
W5GIE
/W6

[Ralph Mowery]

"Wayne" <mygarb...@verizon.net> wrote in message
news:jh6ilv$fv0$1...@dont-email.me...

>
> Hyman W0RSB St. Paul, MN be...@iphouse.com
> ***********************
> -
> I'm somewhat skeptical of the claims at lower frequencies, particularly
> with my recent experiments with tuner loaded verticals.
>
> The current experiment is a 14 foot long vertical (on a flat metal roof)
> fed with 25 feet of RG-8 and a tuner at the rig. It does work quite well
> on 20-10 meters, but not below 20 meters.
>
> Wayne
> W5GIE
> /W6

The tuner for short antennas should be at the antenna. While it will not be
a real killer of a signal, many mobiles do very well with antennas about
half that long, but the antenna is usually loaded at it to match the
feedline.
If you put one of the screwdriver type antennas in the same spot, it shuold
make a lot of differance on the lower bands.

[Wayne]

"Ralph Mowery" wrote in message
news:cs2dnQpTOr1NcKvS...@earthlink.com...

Not mentioned in my previous post is that there is a separate vertical 11
feet long, base loaded, for 40 and 30. I haven't really done much
experimentation with it yet.

I am interested in knowing more details about the Comet matching unit, but I
suspect that the details are unavailable.

-Wayne
W5GIE

[NM5K]

Yep.. My mobile antenna in it's longest "parked" config is a 14 foot
tall whip, and the loading coil is at 8 or so feet up from the base.
It browns the food quite well on 80 and 40, mounted on my large Ford
truck.
The base of the antenna is on the side window pillar, about 2 feet
below the roof line.
I've parked on the beach "Gulf Coast" and done better on 1500+ mile
paths with 100w than some of the guys running dipoles and amps at
various home stations around the country.
No joke.. just due to my antenna spitting most of it's power at just
the right angle, where as theirs were largely aiming straight up in many
cases.
Anyway, the loading is the key.. If the 14 foot whip is loaded at the
antenna, and the radial system is good, it will work pretty well.
And as usual, it's better to have the coil center loaded or slightly
higher for best results. Or add a top hat/wires. But that may cause
visual issues for some. :|
But even base loading would work much better than tuning from the shack
with a tuner. On the low bands with a such a short whip, the tuner loss
will usually get you, even if the feeder losses are low.

[Sal]

"NM5K" <no...@invalid.net> wrote in message
news:jh7cmo$j32$1...@dont-email.me...


< snip

> I've parked on the beach "Gulf Coast" and done better on 1500+ mile
> paths with 100w than some of the guys running dipoles and amps at
> various home stations around the country.

From the beach at Port Aransas TX, I connected a 20m dipole to my 100W
TS-120. The dipole was 9 feet up in the center (ladder on the motor home)
and the ends were about 5 feet off the dirt. I worked three German stations
in short order, along with a slew of guys in the northern US. (The Germans
were contesting that weekend.)

You just never know what will work.

"Sal"

[Owen Duffy]

"Wayne" <mygarb...@verizon.net> wrote in news:jh6a8v$sbb$1@dont-
email.me:

I wrote some notes at http://vk1od.net/antenna/misc/CHA250.htm .

The advice that it contains resistors is not supported by inspection of
the device.

It is lossy, and loss is a common technique for broadbanding an antenna
system.

If you Google, you should find plenty of pics of what is inside the base
of the unit.

Owen

[Ralph Mowery]

"Sal" <sob...@aol.com> wrote in message news:jh7lmp$kjp$1...@dont-email.me...

>
>> From the beach at Port Aransas TX, I connected a 20m dipole to my 100W
> TS-120. The dipole was 9 feet up in the center (ladder on the motor home)
> and the ends were about 5 feet off the dirt. I worked three German
> stations in short order, along with a slew of guys in the northern US.
> (The Germans were contesting that weekend.)
>
> You just never know what will work.
>
> "Sal"

I bet that all the stations gave you a 5x9 report also.

Go to a country that is on the rare list and you can put up a wet piece of
string and get 5x9 all day long no mater how many times you have to repeat
the calls.

During good conditions almost anything will work. It is under bad
conditions that a beter antenna system pays off. I have a beam up 60 feet
and some wire antennas around the same height. Most of the time the signal
levels are such that I can hear the same stations off either one. There are
times that I work stations off the beam with good received signals that I
can not even hear on the wire antennas.

[Wayne]

"Owen Duffy" wrote in message
news:Xns9FF7BB71D1...@88.198.244.100...

=
Hey, very informative. Thanks.
Wayne
W5GIE

[Wayne]

"NM5K" wrote in message news:jh7cmo$j32$1...@dont-email.me...

<snip>

Some years ago, I was in a 40 meter net, along with a local buddy. My
antenna was a dipole at about 30 feet, and he lived in an antenna restricted
condo. So, when he got home from work, he connected the coax from the home
rig to his mobile bugcatcher on the car. Night after night his signal
reports were excellent.

[Jim Lux]

Probably not an explicit resistor, but some sort of network that is
really lossy and has the same effect. There's a variety of this sort
of thing around. Radio Shack used to sell a wideband vertical with a
funky looking ferrite transformer. Looking up the patent, you could
get the schematic, and basically, it was a 10-15 dB loss over a
pretty broad band. Not too tough to get a 1.6:1 SWR with a 15dB pad
in the system (in fact, I'd be amazed if the SWR was ever as bad as
1.6:1)

The odd thing is, such things DO work. When propagation is hot, an
extra 10-15 dB of loss isn't even noticeable.

[NM5K]

On 2/12/2012 12:42 PM, Wayne wrote:

>
> Some years ago, I was in a 40 meter net, along with a local buddy. My
> antenna was a dipole at about 30 feet, and he lived in an antenna
> restricted condo. So, when he got home from work, he connected the coax
> from the home rig to his mobile bugcatcher on the car. Night after night
> his signal reports were excellent.
>
>

At night, my mobile antenna was usually better than my home dipole
on a path from TX to FL. "40m" I discovered this after talking to a
guy from the car, and then switching to the dipole when I got home.
My signal dropped. :( And it was no fluke. I tried it several
more times, and the mobile won most every time.

It's just the mobile antenna being better at that lower angle,
than the dipole, which at 35 feet or so, probably was better for
NVIS, than longer paths.
Of course, in the daytime, the dipole smoked the vertical on
all the shorter paths.
But I've never had any trouble being able to operate running
mobile on 80 or 40 meters. Even the short regional paths on 80m,
I was always able to work the people I wanted to. Often with
quite decent reports for a mobile in a NVIS world.
Would be quite normal to get reports of 20+ DB over 9 on most
peoples meters. Sometimes 30 over 9. And that's on a fairly short
80m path of less than 500 miles.
My mobile antenna in the "driving config" is 11 feet tall.
It's about 5 feet under the coil, and 5 feet above it. The
coil itself, being about a foot.
I add a 3 foot solid hustler mast to make it 14 feet when
I'm parked. Then, it's 8 feet under the coil, and 5 over it.
Makes quite a difference.
But I'm only set up to use those on my trucks now.
I still have not been able to bring myself to cut holes
in my newer Toyota.. :( I know if I do, it's eventually going to
warp the trunk lid, like it did when I mounted it on an Honda Accord
I had. Even with reinforcing under the trunk lid, it eventually
slightly warped the area around the hole. And this is with a
light mostly glass antenna. Mine is a "plastic bugcatcher". :|
So with the Toyota, I just go without, and just take the radio
to use when I get where I'm going.

[Sal]

"Ralph Mowery" <rmower...@earthlink.net> wrote in message
news:m-OdnVDX8tfTQKrS...@earthlink.com...

>
> I bet that all the stations gave you a 5x9 report also.

I'm rather accustomed to that in contests. ;-)

>
> During good conditions almost anything will work. It is under bad
> conditions that a beter antenna system pays off.

Agreed. I only operated from that beach for a few hours on one day. The
next day might have been terrible.

"Sal"
(KD6VKW)

[Sal]

"Jim Lux" <jim...@earthlink.net> wrote in message
news:c6bb4d48-b848-4e9f...@s13g2000yqe.googlegroups.com...

When propagation is hot, an
extra 10-15 dB of loss isn't even noticeable.

Like 10m today. Path from Florida to West Coast was like a land line around
1900Z.

"Sal"