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   Home   Help Search  
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Author Topic: Chameleon EMCOMM2  (Read 25364 times)
ROB1955
Member

Posts: 15




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« Reply #60 on: January 21, 2013, 08:29:01 PM »

Hey, if $125 is burning a hole in your pocket, give it a try and let us know how it works out! Put a review on EHAM.

Are those burning a hole in your pocket too? : http://www.lnrprecision.com/purchase/
(I've nothing against them. They work too. We're talking about price here.)

Look at this one (two bands):
LNR FX-2 with EF-40/30 Antenna Combo   3W/4.5W   $270

or this one (mono band):
EF-80   100W   $125

For cheap made in China junk you can always go to here: http://www.mfjenterprises.com/Categories.php?sec=218

Here is the EMCOMM II link: http://chameleonantenna.com/CHA%20EMCOMM%20II/CHA%20EMCOMM%20II.html

AC2EU if interested I think that chameleon are looking for dealers... It might help your VERY DRY choice of amateur radio antennas on your website. Just saying...



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AC2EU
Member

Posts: 965


WWW

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« Reply #61 on: January 21, 2013, 09:10:26 PM »


Here is the EMCOMM II link: http://chameleonantenna.com/CHA%20EMCOMM%20II/CHA%20EMCOMM%20II.html

AC2EU if interested I think that chameleon are looking for dealers... It might help your VERY DRY choice of amateur radio antennas on your website. Just saying...


No thanks! I don't sell antennas, anyway. If I did, I would want a bit more information. For example, there is no indication of under what conditions/configurations the test was made. 
I have no beef with anybody who wants to make a buck, but as was mentioned, the claims were too general and vague.
The graph is a good start, but he should add some more specifics.
 
The OP started this thread because it sounded too good to be true. Now we have gone full circle.
I have not tried the antenna, but whoever thinks it's for them should buy it and review it. Go for it!!

Instead of fighting, you and your buddy should learn from this thread. You might sell more antennas!!
Personally, I think it's more fun to make my own antennas...
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N4CR
Member

Posts: 1757




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« Reply #62 on: January 21, 2013, 10:14:47 PM »

I found a close-up of each individual bands. Click the link DOWNLOAD GRAPH : https://docs.google.com/file/d/0BxAWMo2X6UGIeVZTd0Jwd0ZWcmM/edit

That's a start. Now where's the gain figures?

Comparison to a standard dipole on each ham band would be a good place to start. in dBd please.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
W1JKA
Member

Posts: 2034




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« Reply #63 on: January 22, 2013, 03:32:04 AM »

     I will not be buying this type of antenna anytime soon,but would be very interested in knowing if the company is listed on any stock exchange.Sales and profit margins can't help but be on the upswing due to low overhead in the marketing dept.(free ads and publicity) and knack for getting free beta testers and consultants in the technical R&D division,an exemplary business model.Perhaps it is listed under another name or abbreviated stock symbol.I doubt it would be a PENNY stock,AMEX maybe??.Buy low sell HI.
« Last Edit: January 22, 2013, 03:51:52 AM by W1JKA » Logged
W5WSS
Member

Posts: 2226




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« Reply #64 on: January 22, 2013, 05:45:53 AM »

My wire works better than yours and mine only cost $5 Grin

Good Carma
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AG6WT
Member

Posts: 510




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« Reply #65 on: January 22, 2013, 08:52:27 AM »



(This one do not works all the time)
http://chameleonantenna.com/CHAFORUM/index.php?p=/

(This one does)
http://groups.yahoo.com/group/ChameleonAntenna/

Why people are posting questions on this forum to get answers about a product (in this case the EMCOMM 2) when they can go directly at the source (their forums) and ask the community, actual owners or the manufacturer directly?


The Yahoo forum is filtered and posts are regularly deleted. If you go there you'll notice that there aren't any posts before Nov 2012 even though there has been a forum since at least 2009 when I was posting there. Why is that? What is there to hide? FWIW, I was posting there back in 2009 because I couldn't get my Chameleon V1 to work and had a series of posts with other owners and one of the Chameleon employees trying to figure out what was wrong. My threads were deleted a few months after posting. My suspicion was that posts that didn't help with sales were purged.

Also, you can make a similar performing antenna for less than half the price with a Balun Designs 9:1 Unun and 53' of wire. Balun Designs has a cutting chart and 53' will keep the SWR low enough on 160-6m for a typical internal or external compact tuner to handle. The rating is only 300 watts but when you are talking encom, how many cart around an amp? And of course if you buy your own toroid you can wind your own for even less; the design is well documented.

Ray KJ6AMF
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WB6BYU
Member

Posts: 15675




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« Reply #66 on: January 22, 2013, 01:44:02 PM »

I think what we have here is one of those verbs with an irregular conjugation:

I am performing an engineering evaluation of the design and publishing my results.

You are checking to see it meets your needs before buying it.

He is bashing the antenna without trying it.


If you go back through the thread I don't remember making any specific negative
claims about the antenna that aren't readily apparent from the description on the
company web site.  It's not "bashing" an antenna if you are making true statements
about it:  other hams can still decide whether it meets their needs or not, in spite
of how inconvenient or uncomfortable the truth might be.

For example, since the antenna is described as a 60' wire connected to some sort
of matching network on the end of the coax, with "no radials required", then,
without knowing what is in the matching network, it is a reasonable interpretation
of basic engineering principles to conclude:

1) there will be common mode currents on the feedline.

2) the 60' wire can't generate a stronger signal for the same output power, or
have a significantly different radiation pattern, than the same wire with a
different feedpoint matching network, except for potential losses in either
network, or due to radiation from the feedline due to the common mode currents.


Now, when someone asks about the antenna, pointing out those aspects of the design
are simply stating the truth, even if they aren't mentioned in the manufacturer's data
about the antenna.  To some people those are important to know.  To others they
don't matter.  Neither of these necessarily prevents the antenna from working as
described (or as not described):  lots of hams use antennas with common mode currents,
and the second implies that it can work as well as other options the same size
if the matching losses are low.

Can we quantify the antenna performance?  Sure we can:  string up a 60' wire,
establish a standard feedline configuration, and then apply different types of
matching networks between them.  Measuring the current or voltage on the
wire at the feedpoint will give a relative indication of output power to the antenna.
You can also experiment with the effect of adding radials, changing the length
of the coax or how it is arranged relative to the ground, etc.  In addition to
measuring the current in the wire, you can also monitor the signal strength at
some distant point, as well as measuring the common mode current on the
feedline.  This is a simple enough test to run - in fact, if one built a fixture
with banana plugs it would be a convenient way to experiment with different
types of matching devices to see what works best on different bands.  (It could
also be used to evaluate different arrangements of the coax to understand how
they affect the common mode current.)


In choosing an antenna, the first step is to decide which parameters are the most
important to you:  what bands it operates, expected signal strengths compared to
other options, ease of use, if it needs a tuner, etc.  For EMCOMM, much will depend
on your vision of the communications needs that you need to meet, because that
affects the required bands, radiation patterns, and radiated power levels, as well
as practical considerations such as available supports, sources of interference,
mechanical stresses on the antenna, required speed of setup, transportability, etc.


It all comes down to making an informed decision of what best meets your own
needs.  The Military and many other organizations like to use wide-band antennas
because they can be set up by non-technical personnel, even if the losses are 5 to
10dB on some bands.  But in a marginal situation where you need every last bit
of radiated power to be heard, or have to make the most of limited batter power,
this wouldn't be as good of a choice.  Similarly, I might not have any issues using
an OCFD or other antenna with high common mode currents when out camping, but
at our county EOC it gives us an S-9 noise floor due to the coax running alongside
the computer network cables.

In fact, in >40 years of providing emergency communications, I haven't yet found
a single "perfect" antenna for EMCOMM, and I've tried a lot of antennas in that
time, from a 60' wire plugged into the coax jack on the back of my transmitter,
to dipoles, quads, rhombics, curtains, long wires, etc.  Currently we use dipole
kits for 40 / 80 / 160m because that best meets our needs, but I also make
sure we have enough options that we can set up a digital link on 30m or 17m
or some other band should the need arise.


So factors such as antenna efficiency and common mode currents can be important
in making an informed decision, and making sure such information is available to
the general public is an critical step in that direction.
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KK4CPH
Member

Posts: 154




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« Reply #67 on: January 22, 2013, 02:00:20 PM »


The OP started this thread because it sounded too good to be true. Now we have gone full circle.
I have not tried the antenna, but whoever thinks it's for them should buy it and review it. Go for it!!

Instead of fighting, you and your buddy should learn from this thread. You might sell more antennas!!
Personally, I think it's more fun to make my own antennas...

And having read thru all these pages, I'm still not convinced.  I think I will make my own antenna.
On page 1 of this thread, Phil (N4CR) posted a way to make an antenna out of ladder line, ladder-loc, and copper wire.  I think that's what I will do.  Will probably only cost about $40.  Phil, if you, or anyone else, could tell me what balun (if any) I need for this set up, then I'll be good to go.

Eric

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W1JKA
Member

Posts: 2034




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« Reply #68 on: January 22, 2013, 03:06:45 PM »

Re: KK4CPH

               Wise decision.Hope you learned a little and had some fun in the meantime.
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N4CR
Member

Posts: 1757




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« Reply #69 on: January 22, 2013, 05:40:42 PM »

And having read thru all these pages, I'm still not convinced.  I think I will make my own antenna.
On page 1 of this thread, Phil (N4CR) posted a way to make an antenna out of ladder line, ladder-loc, and copper wire.  I think that's what I will do.  Will probably only cost about $40.  Phil, if you, or anyone else, could tell me what balun (if any) I need for this set up, then I'll be good to go.

Does your tuner have a balanced line input?

If it does, run the ladder line all the way to the tuner. If it doesn't, run the ladder line to as close as you can get it to your rig and connect it to a 1:1 current balun which connects to coax the makes it the rest of the way to the tuner. Because there can be high SWR on the ladder line/coax , it pays to have more ladder line and less coax because coax can be very lossy when presented with a high SWR condition.

While some say SWR is to be avoided at all costs, it really depends on whether the SWR causes loss. In the case of ladder line, even 10:1 SWR can be fairly low loss and nearly all of the power fed into the system will radiate. And this is why ladder line has been popular for delivery of RF for many many decades, since long before coax was invented.

As far as having a balun and/or a tuner, visit this page and see what you think...

http://www.w5dxp.com/notuner.htm

Look at point 4 in the page below. See how much loss is in a 100' feedline for RG-8 vs balanced line on multiple bands.

http://w4rnl.net46.net/abd.html

That's why many of us continue to use balanced feed lines to this day. Even though coax is convenient, easy to use and can lay along the ground, balanced line is very very efficient at delivering your transmitter power to the antenna without a lot of power being dissipated as heat on the way to the antenna.

If you decide to use a balun, you can build one or buy one. A 1:1 current balun is really easy to build, you just need the right core for it. Here's a good article that explains how to build a 1:1 or a 4:1 toroidal balun. I suggest a 1:1 for the 135' doublet, but many will suggest a 4:1. You can build them both for the price of buying either one already made.

http://www.yccc.org/Articles/Antennas/N1IW/Balun_short_version.ppt
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73 de N4CR, Phil

Never believe an atom. They make up everything.
KK4CPH
Member

Posts: 154




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« Reply #70 on: January 22, 2013, 08:50:29 PM »

Phil, thanks for the info.  My tuner does not have a balanced line input. I'll bring the ladder line right up to my house and from that point its about 6' of coax to my rig. This setup will be a major improvement over my current one which is a 31' vertical that's 150' away. It has been frustrating especially since antenna's are my weak point. That's why I was looking at the Chameleon thinking it would be a quick & easy way.  I learned with CW there's no such thing.  Now it just needs to warm up so I can do this. (Of course an ice storm would "test" my installation)
73,
Eric
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N4CR
Member

Posts: 1757




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« Reply #71 on: January 23, 2013, 04:38:45 AM »

Phil, thanks for the info.  My tuner does not have a balanced line input. I'll bring the ladder line right up to my house and from that point its about 6' of coax to my rig. This setup will be a major improvement over my current one which is a 31' vertical that's 150' away.

If you could get something like this... (that was 275 watts fully modulated AM, for SSB that's just less than a kilowatt)

http://www.ebay.com/itm/Johnson-Viking-275-Watt-Matchbox-Antenna-Tuner-/321060106970

...you'd have what is considered one of the best (high efficiency) ways to drive balanced lines, a link coupled tuner. I shopped for some time and got the smaller Johnson Matchbox for around $100. I run my Collins 30L-1 amp through it often and it handles that just fine. It's great for tuning a ladder line fed doublet. Johnson also made a kilowatt tuner. A kilowatt of AM is way past the capability of our 1500 watt limit on SSB.

Or there are plenty of plans for building your own link coupled tuner.

http://www.pituch.net/Steve%27s%20Page/Radio/500%20Watt%20Link%20Coupled%20Tuner/500%20Watt%20tuner1.html

http://www.richardflake.com/ww8jtuner.htm

There's lots more if you research.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
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