Wednesday, January 3, 2018

Test of Chameleon CHA MPAS Antenna

I recently picked up a Chameleon CHA MPAS antenna with the Mil Extension (CHA MIL EXT), and their ground spike for portable & SOTA work.  The primary reason is that sometimes, the summit is going to be too busy with people to setup my dipole rig.  Cowles mtn is a good example.  Another reason is that I may want the option of setting up faster (5 minutes) rather than goofing around with the dipole.  Mountain tops here don’t have trees so my dipole setup is a mast, guys, and an inverted V config.

I wanted to do a quick setup and function test before my next hike to my main test area (Black Mtn.) or the next SOTA mountain that I want to check off.  My initial testing was at a park on the top of a hill (Hilltop Park) in San Diego.   I setup at two different areas and used a Rigexpert 600 antenna analyzer to gather the data.  I mainly focused on 20 & 40 meter bands and I wanted to know how tunable the antenna was and if I could get out.  The bands weren’t busy and I was wondering if the antenna was going to work at all.  My opinion changed when I had a quick QSO with a guy in Puerto Rico, Vancouver, and another in Nevada.  I guess it’s working.

Note:  I’m a newbie at this (licensed general about 3 months ago) so if you find any errors or have any suggestions, comments, etc, I’d really appreciate you commenting below.

One other note.  The SWR readings are from the graph are estimates based on the graph visual (supplied) and not exact readings except for the median freq.  I could have taken a reading at each end but I really didn’t feel it was needed.  Also, the analyzer is new but I’ve never had it calibrated or bench tested. I could have the most exact data in the world but the data variations produced by different soil, moving the counterpoise just a little, and the way I had my tongue hanging all bump my test results one way or another.  As a ham, you know that there are about a 1000+ other variables that come into play during actual use.  My sample data has three points and it is directionally correct.  Reproducing the tests  at three sites were pretty much +- .2 SWR.  The analyzer pictures have additional data that I did not cover.  Take a look and let me know your thoughts. 

I tested three different configurations in three locations (2 at the park and one at my house) and one config at a single location.  All configurations have a single counterpoise because that is my intended SOTA setup.
     Mounted to a 14 foot tripod
     Mounted to tripod at 6 feet
     Mounted to the ground spike sticking up about 5 inches.
     One test with no matching unit, just the 14’ of stick mounted on the bracket and a counterpoise.

The 7 MHZ band SWR when mounted at 14 feet on the tripod’ ranged from 1.8 at the bottom of the band to 1.95 at the top and was at 1.9 SWR in the middle.  Testing in the other two locations was within +- .2 SWR with my house being lower.

   



The 14 MHZ band SWR when mounted at 14 feet was from about 1.28  at the bottom of the band  to 1.21 at the top and was at  1.26 SWR in the middle. Testing in the other two locations was within +- .2 SWR with my house being lower.

  


I’m not going to bother showing the difference between 14 and 6 feet because the data is +- .2 SWR.  I did find that my house is consistently lower but noticed that just changing the position of the counterpoise bumped the results a bit.  It’s also possible that the soil, which is dry compared to the park, may have had some influence.

Sticking this thing in the ground also works well, which really surprised me.  I’m guessing actual performance won’t be the best, but for gun and run it will get the job done.

  



I did do a test of the 6M band (50 MHZ), and 80m (3 MHZ) and both are definitely tunable, as you can see below. 

  


My final test was to see if it would be tunable without the matching unit.  As you can see below, the 20m band was tunable (I used a MFJ-939Y tuner), but the tuner wouldn’t bring in the 40m band.  When the tuner gave me the warning song when trying to tune 40m, I didn’t bother hitting the radio SWR.

 


I’m happy with 20m and 40m.  Those test results are not only tunable, they show that I can get by without an antenna tuner for this config.  I made a couple of QSOs without the auto-tuner and made Puerto Rico just as the band was headed south. 

I did a bunch of research when looking at end-fed verticals.  The biggest influencer was Julian at Survivaltech Nord, OH8STN.org.  His YouTube videos covered the Chameleon and Alpha antennas in depth.  I’m happy with the CHA MPAS, it  lives up to his review as far as portability, build quality, etc.  Yes, I’ve only put it through one test (3 setup / breakdowns)  but I think this is going to work out great.  I considered the Alpha and dropped that idea after I saw his review and some others.  I also considered the superantenna that Julian is currently reviewing (I think he has three videos of it) but I took it off the list because it was heavy and I didn’t want to futz with the tuner on the loading coil when on a mission.  For SOTA work, I mainly work 20 and need the 40 meter when conditions are bad. The CHA MPAS seems to do both easily (I wish I had done a QSO on 40m but I ran out of time).  I’ll do that in the next week.

Summary of tests and what I learned:

  1. The antenna tunes for 20 and 40 for SOTA without a tuner.  I’ll keep a tuner with me incase my config gets strange.  It is definitely tunable on 6m and other bands. 

  2. Performance was great (3,252 miles), and it went a lot farther than I thought.  I consider the Chameleon a suboptimal solution as compared to my Packtenna inverted V config but I may change my mind after a couple of missions.  The compromise here for me is setup time, weight, and goofing around.  High winds could be a issue, especially if they are swirling.

  3. I’m still learning how to evaluate capability of different antennas since there is more to it than SWR.  The mission here was to see how tunable the antenna was and I checked that off the list.  Obviously I wanted to do a quick QSO to validate the darn thing will get me out of the state, and I checked that off. 

  4. The matching unit really rocks and makes this system a real performer.  Without the matching unit... well, it’s just a wire in the air like anything else.  I’m not really sure why they give you the bracket to mount just the antenna without the matching unit.  I’m only guessing but if you tune and can punch directly to the wire without the matching unit, it may product a tad better results.

  5. I wish I had tested without the MIL EXT on it but I’m a bit of a freak and figured that I would probably not run without it.

  6. I have a lot more to learn, that I think will only come with time.

This is the first shot I’ve taken at doing any kind of published testing that should be reproducible and pass a peer review since I’m using an empirical approach.  I did this because I wanted to give something back.  As a new Ham, one of the things that is really difficult for me is evaluating the difference in performance (actual use, not SWR)  between different antennas, dipole and the vertical setup in this case.  I know that the dipole is the gold standard (yes, yagi and other directional are top dog but not for SOTA work).  I like to maximize my DX when on the mountain and I’d love to know how much I’m compromising.  When I skip 3,200 miles on my first time out, I guess I really shouldn’t bitch.  I do SOTA mainly because living in a neighborhood means that my home station is one giant compromise.   I have a clear shot to the east off the top of the hill from my house via a 45’ gap (between houses).  If it weren’t so unsightly for my neighbors, I’d get something above my roofline.  If I did, I could get a good 270 deg beam shot off my hill.

If you have any thoughts on my analysis, performance of the this vertical vs. dipole, comment below.  I’d love to hear from you. 

Super big thanks to K7CAR  for allowing me to butt in during his CQ time and connect with WP4CTD in Puerto Rico.  Kent also came back to me two more times as I was testing different locations.  This was super helpful and fun.

UPDATEI've just posted results of some practical tests HERE.  Check it out!

Contacts for today (all on 20m)

     WP4CTD
     VE7MTW
     K7CAR

REFERENCE

      My Typical SOTA Loadout
      For more info on SOTA, rules, etc, go to the homepage HERE.
      Ham Terminology
      SOTA Specific Links



73s,
-- Chris Claborne, N1CLC



2 comments:

  1. Nice write up. Found your blog doing a search for "CHA MPAS SWR Chart". My 30ft mast and EFHW Wire had to come down since guy wires took a beating from my Alaskan Shepherds' jaws of life. Looking at a vertical for low angle take off on the lower bands, need antenna for next 9 months until I start the tower project. Welcome to ham radio. I was recently licensed in March 2017. 73, W7DAZ. Derek

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