On Fri, 09 Jun 2006 00:59:53 GMT, Owen Duffy wrote:

On Thu, 08 Jun 2006 20:33:12 -0400, Mike Coslo
wrote:


I'd buy a tuner that will handle open wire feed, lose the 4:1 balun,
and get on the air.

Mike, did you notice "Mystery's" comment re spending more money on a
"tuner extender": "Not the answer I wanted to hear". She/he may be
even less interested in the spend on the tuner you describe.

I agree with you that antenna looks worth a try / perseverance, but it
will probably need a wider range tuner than commonly fitted internal
to transceivers unless you experiment (what's that!) to find a
feedline length that the rig/runer accommodates on all bands, or
switch feedline lengths.

Owen


There really isn't a lot of information on the antenna on the page I
saw: http://www.k1jek.com/. Many antennas have a spectrum of
frequencies and their associated SWR. Knowing my internal tuner can
only handle 8:1 but the antenna shows places I am interested in using
with 12:1, would help me in my decision to choose the antenna or
another. the OP didn't have that information. I know that internal
antenna tuners are basically 'fine-tuners' and are very limited
compared to external tuners. (at least Kenwood is clear about that in
their instruction guides. ) I am not pointing a finger at either
party, Mystery for not posting the information or some warning nor the
OP for not asking. The Mystery page isn't very Corporate looking so
one would have to assume some give and take in the purchase by both
parties.

Is there any reason the antenna can't be returned for a refund? If
not, can it be sold to someone else who is interested?

This is one of life's lessons learned.


I just looked at the review of the antenna from eHam.com:
===============
WA1BSB Rating: 5/5 Apr 24, 2006 14:29

Homemade Ultrilite Senior Time owned: 0 to 3 months

Hi I went and made a homemade Ultrilite I too 3 conductor tv rotor
cable 70 ft each side and mounted it to a modified 450 ohm ladderloc
at the center I then ran about 50 ft of ladder line down to a 4.1
balun I know the plan calls for 100 ft but I just dint have the spot
to coil it up The antenna is in a flat top configuration up between 2
trees about 80 ft up from the balun I ran about 70 ft of RG8X 50 ohm
to my 746 Pro it tunes perfect on all bands 10-160 using the radios
tuner 1.1 swr Anyhow it works with good signal reports so far on 40
and 20 meter Im looking forward to trying in 75 and 160 Anyhow bottom
line whether you make one or buy it its quite the antenna I glad I got
one 73s
==================

There are many other reviews about the antennas, both jr and sr.

Maybe there is a better configuration that will work, or he may need
the tuner or tuner extender.

Good luck

Buck


--
73 for now
Buck
N4PGW

On Fri, 09 Jun 2006 00:05:47 -0400, Buck wrote:

frequencies and their associated SWR. Knowing my internal tuner can
only handle 8:1 but the antenna shows places I am interested in using

Buck, how do you know that your tuner can handle (presumably SWR up
to) 8:1? Is it a commonly published specification for transceiver
internal tuners or external tuners?

The capability of a tuner is much more complex (pardon the pun), but
could be mapped for each band to a Smith Chart as an area of input Z
that could be transformed to 50 ohms, and then one could plot loss
contours to show the acceptable range. What would you do with the
information?

Whilst it may be appropriate to specify the tolerance of Z on a
nominal 50 ohms antenna with a maximum VSWR in a given frequency range
(eg as often done for VHF and UHF antennas), the Cobra does not
pretend to present any particular impedance on any particular
frequency (remember that user is permitted to use any length of open
wire feed operating at high VSWR, so the Z at the tx end of the balun
cannot be specified at any frequency).

The Cobra Junior, a 72' long linear loaded dipole, looks interesting
in terms of a short antenna for low HF bands with reasonably low
losses. I have run some preliminary NEC models and analysed the feed
system loss with 25m of W551 ladder line, they look promising. I will
build a complete model over HF along the lines of the ones that
underly my article on the G5RV feed system at
http://www.vk1od.net/G5RV/index.htm . More when it is done in a day or
three.

Owen
--

Owen Duffy wrote:
On Thu, 08 Jun 2006 20:33:12 -0400, Mike Coslo
wrote:


I'd buy a tuner that will handle open wire feed, lose the 4:1 balun,
and get on the air.

Mike, did you notice "Mystery's" comment re spending more money on a
"tuner extender": "Not the answer I wanted to hear". She/he may be
even less interested in the spend on the tuner you describe.

Of course.

But sometimes the unwanted answer is still the correct or best one.....



I agree with you that antenna looks worth a try / perseverance, but it
will probably need a wider range tuner than commonly fitted internal
to transceivers unless you experiment (what's that!) to find a
feedline length that the rig/runer accommodates on all bands, or
switch feedline lengths.


Sounds like time for Cecil to join in. I know his system uses
switchable lengths of twinlead, but perhaps he might have something to
offer here in a one length feedline system.

- 73 de Mike KB3EIA -

Michael Coslo wrote:
Sounds like time for Cecil to join in. I know his system uses
switchable lengths of twinlead, but perhaps he might have something to
offer here in a one length feedline system.

Anyone have an EZNEC model of this antenna?
--
73, Cecil http://www.qsl.net/w5dxp

Michael Coslo wrote:
Sounds like time for Cecil to join in. I know his system uses
switchable lengths of twinlead, but perhaps he might have something to
offer here in a one length feedline system.

Things are slow here at the GED office today so I modeled
the Cobra-Jr and Cobra-Sr. The Cobra-Jr suffers from
feedpoint impedance problems similar to a G5RV used on
75m. The feedpoint impedance on 3.7 MHz is about
16.5 + j459 ohms giving a 450 ohm SWR of 56:1.

For my variable feedline method to work with 450 ohm line,
the SWR must fall between 4.5:1 and 18:1. A dipole that is
1/2WL on the lowest frequency of operation usually meets
that requirement. The G5RV length doesn't and the Cobra-Jr
doesn't.

One thing interesting about the Cobra-Jr is that if it is
made 62 feet long instead of 73 feet long, it becomes
resonant around 3.85 MHz with a feedpoint impedance of
about 16 ohms. That's an SWR of only about 3:1 on coax.
or ~1.3:1 using a 1:4 balun. That's a half size antenna
for 75m that is only about 1.5 dB down from a full size
1/2WL dipole.
--
73, Cecil, http://www.qsl.net/w5dxp

On Fri, 09 Jun 2006 00:59:53 GMT, Owen Duffy wrote:

Mike, did you notice "Mystery's" comment re spending more money on a
"tuner extender": "Not the answer I wanted to hear". She/he may be
even less interested in the spend on the tuner you describe.

I agree with you that antenna looks worth a try / perseverance, but it
will probably need a wider range tuner than commonly fitted internal
to transceivers unless you experiment (what's that!) to find a
feedline length that the rig/runer accommodates on all bands, or
switch feedline lengths.

Owen


How is the "tuner extender" made? is it simple enough to duplicate
with a home-brew?


--
73 for now
Buck
N4PGW

Buck wrote:

How is the "tuner extender" made? is it simple enough to duplicate
with a home-brew?


A tuner extender is about worthless. It is an autotransformer. Nearly
every auto tuner has more impedance range than the ferrite core
autotransformer used to extend the tuner.

The problem really is the Cobra does NOT have resonances at the points
that are claimed, so impedance is off the scales on some Ham bands.

I measured a Cobra that was supposed to hit 80, and it missed by a few
MHz. A person would be much better off doing something else, although
I'm sure with a good tuner contacts could be made on any band.

After all.... I can work Europe on 160 SSB and VK's on CW with my
mobile antenna, and it is less than 1% efficient and that is on 160!!

73 Tom

Mike Coslo wrote:

SNIPPED

I'd buy a tuner that will handle open wire feed, lose the 4:1 balun,
and get on the air.

- 73 de Mike KB3EIA -

That's exactly what I use.

130 feet long center fed doublet with 600 ohm open wire tuned feeders.

Tuner is an OLD [30+ years] MURCH UT2000A with a balun.

Runs great on 75/80, 60, 40, 30, 20 meters.

I have used a LP for 20-10 meters. It is currently down as a result of QTH
change and limited $$$.

/s/ DD, W1MCE

wrote in message
oups.com...
Buyer Beware
I have read all the reviews and I am wondering if they are about the
same antenna I purchased. I bought the Cobra junior antenna and
followed the directions for installation. The antenna is 50ft in the
air in a flat top configuration. When I hooked it up to my radio, it
would not tune on segments of certain bands, most noticeably 75/80. I
called Joe to get some help and was told that my radio, which has a
built in tuner would not accept more than a certain level of SWR and
was told to trim the twinlead back 19 feet. I did and while some of the
problem was solved, I continued to have problems on 75/80. I emailed
Joe to ask for further assistance and was told that the next step was
to buy a tuner extender (price $60). Not the answer I wanted to hear.
If in fact this kind of problem exists with radios that have built in
tuners, prospective buyers should know that in advance. For the cost of
the antenna and now the tuner extender, I could have bought a better
antenna, which is what I intend to do. I am not pleased with this
antenna and would not recommend it especially to someone who has a
radio with a built in tuner and intends to use it. Additionaly, the
performance on 40 seems to be very good. It seems to under perform on
20. Can't tell on 75/80 because I can't tune the band.

KC2GWK

Lots could be wrong here including trying to kibbutz the problem from afar.
But it *sounds* like it is a combination of not enough tuner and a "bit" of
operator error. The internal tuners simply do not have enough capacity to
meet the demands of all-band operation in some cases. I have the Ultralite
Senior using the LDG Pro 100 tuner and I simply LOVE this antenna! I know
that there is loss on some bands, but any so-called "all-band" antenna is
going to be a compromise when compared to a dedicated, resonant antenna. I
don't even LIKE tuners, but I have some requirements beyond the Amateur
bands including US gov't SHARES and FEMA. I have to quickly move from one
band to the other and, in order to do so, I have to accept some loss.
However, I am VERY happy and surprised at the overall performance of *my*
antenna. Actually, I'm told that it is unusually loud for a 100 watt station
on a number of bands and quite readable on others (I don't HAVE to be the
loudest thing going to be effective).

I would guess----and that is what it is, a guess------that your internal
tuner doesn't have the ability to match this antenna-----AND probably a
number of others as well in multi-band service. Or you simply may have
overlooked something in the installation---like location or height above
ground.

For every 10 users of a product, there's going to be one, perhaps, that is
dissatisfied. With the Cobra, the reviews I have read are decidedly in favor
of both the Junior AND the Senior Ultralight. You can't win 'em all!


73

K4KWH

I have the Ultralite Senior and am very happy with it. I have it at 30
feet with the ends dropping down about 15 feet since my lot isn't big
enough. I bought it primarily as a local contact antenna since
everything else I have is a vertical of one type or another. It turns
out to work much better than I expected. I have worked the South
Pacific, Europe and Peter One on it with 100 watts. I use the full 100
feet of ladder line it came with to a 4:1 balun through a remote
antenna switch and 50 feet of LMR400 coax. Sometimes it receives better
than my verticals and it almost always is quieter. In fact that is why
I used it for Peter One, I couldn't pick what calls they were coming
back to because of the noise on the vertical and half square. My TS-480
internal tuner tunes it on every band, even 6 meters which there are no
claims for.

Pete W6OP

Jerry wrote:
wrote in message
oups.com...
Buyer Beware
I have read all the reviews and I am wondering if they are about the
same antenna I purchased. I bought the Cobra junior antenna and
followed the directions for installation. The antenna is 50ft in the
air in a flat top configuration. When I hooked it up to my radio, it
would not tune on segments of certain bands, most noticeably 75/80. I
called Joe to get some help and was told that my radio, which has a
built in tuner would not accept more than a certain level of SWR and
was told to trim the twinlead back 19 feet. I did and while some of the
problem was solved, I continued to have problems on 75/80. I emailed
Joe to ask for further assistance and was told that the next step was
to buy a tuner extender (price $60). Not the answer I wanted to hear.
If in fact this kind of problem exists with radios that have built in
tuners, prospective buyers should know that in advance. For the cost of
the antenna and now the tuner extender, I could have bought a better
antenna, which is what I intend to do. I am not pleased with this
antenna and would not recommend it especially to someone who has a
radio with a built in tuner and intends to use it. Additionaly, the
performance on 40 seems to be very good. It seems to under perform on
20. Can't tell on 75/80 because I can't tune the band.

KC2GWK

Lots could be wrong here including trying to kibbutz the problem from afar.
But it *sounds* like it is a combination of not enough tuner and a "bit" of
operator error. The internal tuners simply do not have enough capacity to
meet the demands of all-band operation in some cases. I have the Ultralite
Senior using the LDG Pro 100 tuner and I simply LOVE this antenna! I know
that there is loss on some bands, but any so-called "all-band" antenna is
going to be a compromise when compared to a dedicated, resonant antenna. I
don't even LIKE tuners, but I have some requirements beyond the Amateur
bands including US gov't SHARES and FEMA. I have to quickly move from one
band to the other and, in order to do so, I have to accept some loss.
However, I am VERY happy and surprised at the overall performance of *my*
antenna. Actually, I'm told that it is unusually loud for a 100 watt station
on a number of bands and quite readable on others (I don't HAVE to be the
loudest thing going to be effective).

I would guess----and that is what it is, a guess------that your internal
tuner doesn't have the ability to match this antenna-----AND probably a
number of others as well in multi-band service. Or you simply may have
overlooked something in the installation---like location or height above
ground.

For every 10 users of a product, there's going to be one, perhaps, that is
dissatisfied. With the Cobra, the reviews I have read are decidedly in favor
of both the Junior AND the Senior Ultralight. You can't win 'em all!


73

K4KWH