I decided to do a quick and simple SWR analysis of my Chameleon Antennas CHA MPAS Lite today.
NOTE: This is only in the VERTICAL configuration.
Using a Rig Expert AA-35 Zoom and the antScope 2 software, I ran through a few scenarios that I’m posting here for my reference and yours.
The antenna was setup in my backyard in a vertical configuration. I unspooled exactly 25 feet of counterpoise per the manual (marked with electrical tape for repeatability), laying it on the ground.
The entire length of the included coax was also unrolled and laid out on the ground. I did note initial higher SWR readings with it coiled and with a shorter length between the antenna and the analyzer.
Let’s start with a full range reading. This is the end to end range that the AA-25 Zoom can handle, which is 60kHz to 35MHz.
We can then run through each band, one by one, zooming in on the SWR ranges that the analyzer reports. Note the wide portion of each band that is covered by the SWR regardless of it being >= 1.5. We do not see large dips that start and end with the band edges.
160m
80m
40m
30m
20m
17m
15m
12m
10m
Confusion
Upon getting the band by band results, I started scratching my head because the SWR readings that I was getting was different than what Chameleon reports in their user manual.
In some cases better, in others worse.
I decided to then run the AA-35 Zoom against my Hustler 4BTV Vertical antenna which I have for my permanent antenna installation at home.
Everything lines up exactly like I expected for the 40/20/15/10 meter portions, so I am chalking up my CHA MPAS Lite readings to one of two things; environmental factors such as location, etc., or difference in meters being used from Chameleon and myself.
In either case, Chameleon does state in their user manual that:
The CHA MPAS Lite requires a wide range antenna tuner or coupler on some bands…
Page 3 of User Manual
In other words, this is not a resonant dipole that you hang in a tree and then go – it is a toolbox sort of antenna that performs quite well across multiple amateur bands, but requires some tuning depending on what band you’re using.
Conclusion
For reference, here is what they published for SWRs in a vertical configuration vs what I got, with green and red representing better or worse than advertised respectively:
| Frequency | Chameleon’s SWR | KD0HBU’s SWR |
|---|---|---|
| 1.9 | 4.5 | 3.7 |
| 3.7 | 3.3 | 2.9 |
| 7.1 | 2.0 | 2.8 |
| 10.1 | 1.8 | 2.8 |
| 14.1 | 1.7 | 2.1 |
| 18.1 | 1.2 | 1.5 |
| 21.1 | 1.2 | 1.5 |
| 24.9 | 1.6 | 2.2 |
| 28.5 | 2.0 | 2.6 |
If anyone knows what I should try different to improve on the above, please let me know in the comments.
I’ve never used any of the Chameleon products — they are too expensive to buy and ship to the UK —
However from my own antenna activities, assuming the Chameleon has something like a 9:1 UnUn at its base, the counterpoise length makes a BIG difference to the SWR on different bands.
I have tested, adjusted and marked my 9:1 antenna’s counterpoise for minimum SWR — measured using an inexpensive analyser, but on all the main amateur bands, (other than 160M where the antenna radiator is just too short) I can get below a 1.8 SWR. 80M is s bit of a stretch too with such a short radiator.
Buddipole do something similar using a measured radial with their Buddistick products — and it works!
(This is where I got the idea.)
My vertical radiator is a 7Metre fibreglass pole with circa 18 SWG PVC covered wire radiator ‘velcro strapped’ to the pole (The same pole/radiator I use with my QRPGuys 3-band antenna — as depicted on my website and Youtube channel)
However, my favourite portable vertical is the End Fed Half Wave using a 10M pole for 20M and above. With that antenna I use a single 10ft counterpoise.
73
Bruce G4ABX
@G4ABX
DrT(G4ABX)
g4abx.co.uk