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Buyer Beware - Cobra Ultralight

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

Buyer Beware - Cobra Ultralight

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

Buyer Beware - Cobra Ultralight

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
--

Buyer Beware - Cobra Ultralight

Owen Duffy wrote:
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.

Here's what my IC-756PRO manual says about its internal
tuner: "*Matching impedance range: HF bands, 16.7 to 150
ohms unbalanced (Less than VSWR 3:1)"
--
73, Cecil http://www.qsl.net/w5dxp

Buyer Beware - Cobra Ultralight

On Fri, 09 Jun 2006 05:13:04 GMT, Owen Duffy wrote:

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?

In the manuals or specifications of most radios I have looked at with
internal tuners, they say somewhere what the tuner can match. The
Kenwood TS440SAT had in its instructions somewhere that it could match
antennas with SWR up to 10:1 (which seems to be typical of most
internal tuners on radios.) I have read the specs of many rigs
including Yaesu, Kenwood and Icom. I can't say which have the specs
and which don't, but I remember reading the specs many times for many
radios.

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?

I would read the radio specs, check my antenna and if the antenna
matched, it matched, if not, I would use an external tuner, adjust the
antenna, replace the antenna or repair the radio if necessary.

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).

I saw NO specifications on the antenna related to resonance when I
looked (the link is posted on an earlier posting.) This leads me to
believe that the antenna is made by a hobbyist rather than a
professional corporation. This isn't necessarily bad, but it would
mean I would look into it further before buying. Reading the reviews
in eHam, etc, which I believe pointed to a good antenna not addressing
your specific problem. However, having as much information as I have,
I would have done what the first reviewer on eHam did. I would build
my own and test it.

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.

I will be glad to look at that. I hope it helps the OP.

Owen

Thanks,

When looking at antennas, I first look at all the information
available from the manufacturer, then I look for reviews such as at
eham, and I might bring it up for question here and at similar forums.

The antenna in question has no specifications or promises, per se,
except for the claim that one can tune it to all the bands. This
claim is reinforced by the reviews on eHam.com. As I said earlier, I
wouldn't buy it, I would build it. I like doing that. :) If I were
to purchase it and had an internal tuner in the rig, I would ask the
maker or seller of the antenna if it is expected to work on my
particular radio. He might inform me that the antenna might not work
on some internal tuners and I would be better informed before I
purchase.

Of course, the OP apparently doesn't have this information, or didn't
read it about his particular rig. Then again, there are very many
external factors that could affect the antenna.

I recently helped someone connect an 80 meter antenna to a TS-440 SAT
which has an internal tuner. When we tested it in one position, it
worked perfectly. However, when we added 6 feet of coax to move the
radio and it suddenly tuned everywhere in the mars 4 mhz band except
the area around which he meets in his net. We had to trim the antenna
to make it match. Strange, but true.

I didn't analyze the whys and wherefors, but we did get the man
operating successfully, which was the purpose of our visit.

Well, I have to get ready for that four letter word forbidden on local
repeaters here.

73 for now.
buck

--
73 for now
Buck
N4PGW

Buyer Beware - Cobra Ultralight

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 -

Buyer Beware - Cobra Ultralight

Dave Platt wrote:
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
That all seems pretty reasonable though the explanation that the
"built in tuner would not accept more than a certain level of SWR" is
not a good way to express the limits of internal tuners, but it is an
explanation that would appeal to those with lesser knowledge.
The problem is that antenna is advertised to work all bands.
Unfortunately it doesn't do very well on many bands.

The SWR is "off the scale" on many bands.

The same would be true of almost any other doublet-style antenna, I
think. Such antennas are often usable on a large number of bands if
you have a wide-range transmatch/tuner, but I don't think I know of
any which are usable in this way with the limited-matching-range
"line flattener" ATUs built into modern solid-state transceivers.

The Cobra Ultralight is only about 60% as long as a normal resonant
near-half-wave dipole for 75/80 meters. It's shortened by linear
loading. I imagine it has a narrower SWR bandwidth than a simple
dipole.

Which right away spells trouble when trying to match the huge 85-75
meter bands.

The manufacturer states that a tuner _is_ required. The wording is
perhaps somewhat more optimistic about using a transceiver's built-in
ATU than is justified, though. I wouldn't plan to use an antenna of
this sort without a good external tuner with balanced-output
capability (whether intrinsic or via a good current balun).

The original poster might want to consider making a multi-wire (or
"fan") dipole. With several sets of wires it'd surely be possible
to make one which would tune on 80, 75, 40, and 20 well enough to not
need an external tuner... although fitting it into under 80 feet of
linear space might prove to be a challenge.

Or an off center fed dipole. If he can get that antenna up 50 feet,
the ends can droop down.

- 73 de Mike KB3EIA -

Buyer Beware - Cobra Ultralight

"pbourget" wrote in message
ups.com...
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...

Yes, the Ultralite Senior is quite effective! Mine is at 60 feet at the
apex and the "Vee" droops down to about 20 or so. I get pretty nice signal
reports both from local and afar. You can't always win 'em all, but when an
antenna works *reasonably* well most anywhere you work, a fella can't ask
for much more! And I am perfectly happy with mine.

73

Jerry
K4KWH

Buyer Beware - Cobra Ultralight

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