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Author Topic: Chameleon EMCOMM2  (Read 11685 times)
WA2OMU
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Posts: 8




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« Reply #60 on: January 21, 2013, 03:26:54 PM »

AC4RD de WA2OMU...

I dont know the answer to that, and since I have only used it with 5 watts, it dont get warm.

I CAN tell you how to sort of measure that, tho, but I wont do it for you, even tho I have access to the equipment - I am now retired and still consulting, so even after 44 years there, they are reluctant to let me take the equipment home any more.

Here is what you need to do:  Caution!  High Voltages can be present on the antenna at the hybrid output!!

Take a good Tek scope, at least 2 channels and 150 MHz BW, a good low capacitance 10X or 100X probe and a Tek 50 MHz Current probe, the larger one so it fits over the base of the antenna at the top of a Hybrid or Mini. 

Mount the hybrid with a good ground on the base.  Carl's counterpoise kit is recommened for this, also.  Keep the scope, etc below the counterpoise kit radials.

Read the voltage and current on top of the hybrid with a carrier anywhere from 3 - 50 MHz.  Do this with several antennas on top - a Mil, a V1L, Mil on top of a V1L base, the 60 foot wire, etc., at the bottom, center and top of each band, and several points between bands.

Pay attention to the Phase between the voltage and current, and calculate the power going to the antenna from the Hybrid.   You cant use a 50 Ohm device at the Hybrid output, it will be too reactive for that.  The probe cable lengths will also introduce some Phase shift, so take note of that at each frequency, also.

Measure the power going into the hybrid with a good wattmeter, and divide that into the calculated output.  Or, subtract the output from the input.  So long as the SWR at the Hybrid input is <2:1, you should be able to get a pretty good approximation of the losses.  Adding an input tuner is problematic, as the tuner losses are not known without 2 wattmeters, and the one with the high SWR between the tuner and Hybrid wont read correctly anyways.  A good bi-directional wattmeter on the input will help with high SWR going in.

Plot the results.  Publish them here.  Yeah.  This is a LOT of work.  You asked, we await the results.  No, you dont have to have this by tomorrow at noon.  Maybe friday?

Frankly, without an antenna range, with a standard antenna to compare to, this is about the best you can do.  How accurate will this be?  Depends on a lot of things, some you can control, some you cannot.  But the antenna will be quite reactive at the top of the hybrid since it is not a resonant length at most of the frequencies of the testing. 

One other thing, not quite so scientific is to put some standard antenna up, prefereably a quarter wave vertical, or maybe one of those 43 footers, maybe a Gap, and the mini with various whips, keep them at least outside of the Near Fields, and not at some multiple of a quarter wave and compare them using a coax switch to go between antennas.  This wont give you any pattern elevation information, just a signal strength between your two antennas.  Put the 60 foot wire up as an inverted L, or use the EMCOMM, with the horizontal section at the same height as a resonant dipole for the band, and parallel to it, again the approprite distance apart, and do the comparison again.  You can use a calibrated attenuator in one line or the other to get a better result than just the S-meter alone - match the signals at the same S-meter level with the calibrated attenuator.  This will be easier and probably a lot safer.  But this is a system level test, and you cant seperate the hybrid efficiency from the antenna patterns.

I have done this with my dipole and the 25 foot aluminum flag pole that now supoports the center with an AH-4 tuning the flag pole against 4 extension cord radials laid on the ground - 3 25 and 1 50 footer - I had to take the tree that supported the center down...  so when I put that flag pole in, I made sure that it was isolated from ground with a lightning gap at the bottom (inside the PVC sleeve) so I could use it for an antenna, if necessary.  Frankly, on 40 the dipole had it by a big margin with NVIS, and the flag pole more the same on DX.  On 20 and 15 (nothing higher was open) they were more the same, but the dipole was generally better (it was higher than the ground mounted flag pole).

I would love to see the results of both methods!  I wonder what the correlation would be.

Having said all that, I am still satisfied both with my home trap dipole and my Mini and Mil Whip.  I have bot the V1L, and plan to do some more testing next spring.  Right now, there is 6" of fresh snow on the ground and it is 20 degrees outside, and dropping.
 
73,  Jerry  WA2OMU
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WA2OMU
Member

Posts: 8




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« Reply #61 on: January 21, 2013, 03:53:55 PM »

One more thing -

That Conjugate Match your antenna tuner makes - transform the resistance to 50 Ohms and balance the reactance out so the system is resonant.  Not much loss there.  Dont know what is in Carl's matching network, but it seems to achieve the same thing without relays or knobs, and is quite broad band to boot.

Also, toroids can get hot - core losses are always there, as are wire losses.  Same with your Tuner coils.

If the tuner is at the antenna, so much the better (AH-4).  The line is flat.  The Hybrid is also at the antenna...

If the tuner is at the transmitter end of the coax, the reactive losses are higher than if the line were flat (into a 50 Ohm, non reactive load).  I feed my dipole with 85 feet of LMR-400 to minimize those losses, but they are still there, and I work the whole world with that antenna, both QRP and at 100 watts.  Like I said - I am satisfied with it and its performance.  No, it aint as good as a resonant dipole on every band.  But it works quite well enough.

Jerry  WA2OMU
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WA2OMU
Member

Posts: 8




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« Reply #62 on: January 21, 2013, 06:15:13 PM »

Finally,

For the record, all my portable ops (mostly QRP with my 817)  pre Chameleon have been with resonant dipoles for each band, 40 - 6, (but not 75 or 160).

I used Mil M22759/43 wire, silver plated, ETFE Tefzel insulated, 16 or 18 gage, cut to each band and trimmed with my AA-54 to the band centers of most use.  I have ring crimps on each end to attach to the center feed and the end insulators.  I use heavy fish line to pull this up into trees, with center and end supports.  (Mostly always available where I go...)  NOT easy to change bands!!  Different length dipoles, too!

I have a special choke balun at the feed, with lugs for the crimp on connections on each wire.  I have 3 LMR 200 coaxes, a 25, a 50 and a 75 foot, with barrel connectors to get what I need to reach from camp to the antenna.

Oh, yeah, plenty of spare washers and nuts...

This gives me the absolute maximum efficiency and minimum SWR, BUT...

I had so much fun with the Mini and Mil on everything from 20 to 10, that I am questioning continuing lugging all that wire around any more - maybe the 40 dipole, maybe the 60 foot wire - the mini will be there, anyways...

Can I sacrafice even a little efficiency for convenience?  You  BET!  Even at 5 watts.  It worked.  Dont even need the trees any more! 

WALLAH!!  Instant QSY!!  I can use a setup that gives me the bands I want at minimum SWR by adjusting the counterpoise to some extent  -  On the Ground, Dont have to lower anything!!  Yeah, most rigs will work OK into a 2:1 SWR, and I KNOW that I can do this and better with just the mini and Mil with a single 17 foot counterpoise laid on the Ground from 20 to 10!

Thanks, Carl.

By the way, all you folks, Carl just published some SWR and Return Loss charts for the EMCOMM2 on his site. 

Jerry  WA2OMU

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AC2EU
Member

Posts: 399


WWW

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« Reply #63 on: January 21, 2013, 07:12:00 PM »

Quote
By the way, all you folks, Carl just published some SWR and Return Loss charts for the EMCOMM2 on his site.

Got a URL? Just went to the mfr's site and it looked the same to me!
Not for nothin', but there really should be some attempt to show performance specs on their site, even if it is under "ideal conditions" for the various configurations.
There are no disclaimers there saying you need radials,etc, for such and such... It just implies that it works as is.  Huh
It DOES SAY that an external tuner IS REQUIRED.

This is all much ado about nothing, but it sure is entertaining to see grown men getting their panties in a bunch over an overpriced piece of wire!   Roll Eyes

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.


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ROB1955
Member

Posts: 10




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« Reply #64 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: 399


WWW

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« Reply #65 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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ROB1955
Member

Posts: 10




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« Reply #66 on: January 21, 2013, 09:36:20 PM »

AC2EU A review has already been posted few days ago: http://www.eham.net/reviews/detail/10895

I don't know what you need to know more than that:
They tell you which frequencies was tested (2MHz to 54MHz)
They tell you the length of wire (60')
They tell you the elevation of the wire (10' high)
They tell you the wire orientation (Horizontal)
They tell you the length and type of coax cable used (25' RG-8X)
And they even tell you the coax was removed (mathematically from the SWR reading)

What do you need more?

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

I've no idea what kind of antenna analyzer they used (AIM4170 antenna analyzer maybe ??)

We're simple CHA products owners. No more no less.
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N4CR
Member

Posts: 1666




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« Reply #67 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

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
W1JKA
Member

Posts: 1679




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« Reply #68 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: 1728




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« Reply #69 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: 448




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« Reply #70 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
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Posts: 13253




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« Reply #71 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 #72 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: 1679




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« Reply #73 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: 1666




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« Reply #74 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

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
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