Tag Archives: shtf

Lightweight Antenna Roundup 2 – Chameleon MPAS Lite v Wolf River Coils SB1000 TIA

When I was running mobile HF in the 1990’s and early 2000’s I accumulated a bunch of 3/8-24 mount antennas. There were hamsticks, Hustler coil-loaded whips, an Outbacker Perth, plain whips… Outbacker sold a metal tripod that was marketed as a ground plane and antenna mount in one. I didn’t spring for that. I just bolted a 3/8″ coupler to a cut-down surveyor’s tripod, made a quick and dirty radial plate, and gave it a go. It worked. It wasn’t great but it gave me a different way to deploy those mobile-mount setups. At that time these “stationary mobile” solutions were a novelty setup among the hams and publications I interacted with. A simple dipole was always going to crush that mobile antenna, and did.

FFW to the vaguely 2020-ish period and somehow ultra-portable field antennas, mainly for QRP use, are flying off the shelves. In the depths of a solar minimum, no less. The effectiveness of these systems is a tribute to the radio arts in general. Getting a signal onto the air is still job #1. The vagaries of propagation and the system on the other end of the QSO take care of the rest.

Three of the most popular categories today are end-fed wires, linked dipole/monopole, and coil-loaded verticals. Some designs hybridize these approaches. I’m leaving the brilliant DX Commander line out of this because I think they are portable with an * in that it isn’t a trivial thing to set up. I own one and will be giving it the treatment it deserves soon.

I currently maintain a small armada of portable antennas and they all have their strengths and weaknesses. Today I’m going to examine two designs that have some similarities, some differences, and I feel they fill a similar niche:

Chameleon MPAS Lite

The Chameleon MPAS Lite is an end-fed design based on a CHA Hybrid-Micro (roughly 5:1 un-un), a very nice 17′ stainless steel telescoping whip, and a burly stainless steel ground spike to mount them on. It also comes with 50′ of medium duty feedline RG-58-looking coax with a ferrite-bead common mode choke installed, and 60′ of tacti-cool PTFE insulated he-man wire on a heavy duty winder. A supplied stainless steel D-ring on a 3/8 stud allows the CHA Micro to feed a wire (The supplied wire or your own) for NVIS and other “mo’ radiator mo’ betta” setups. Not coincidentally it has the look and feel of the Jeep of portable antennas. I would not want to be on the receiving end of that ground spike wielded in anger.

WRC SB1000 TIA

The Wolf River Coils SB1000 TIA, Mega Pod is a self-supporting HF vertical antenna system. The SB1000 is a sliding-contact adjustable coil. This design is immediately familiar to any mobile HF op. In fact many users deploy the Silver Bullet series coils in HF mobile setups and their reviews indicate satisfied customers. Think of a screwdriver coil without the screwdriver. It feeds a stainless 102″ (8.5 foot) whip, and the coil is designed to load that whip from 80-12m. The kit comes with three 35′ wire radials, and the Mega-Pod. The pod is a machined aluminum hub with three 3/8″ tapped holes at 120 degree intervals, and a standard SO-239 to 3/8″ stud mount adapter mounted through the center. Three aluminum rods with threaded ends form the legs, which also act as radial attachment points thanks to the provided lock nuts. It’s a good, reliable design and the use of aluminum in the Mega-Pod helps keep the overall weight down.

Portability and Ease of Operation

Both antenna systems are light, portable, set up and break down easily. The Chameleon has a smaller footprint due to only using one (or zero) radials. The WRC needs a larger area to spread out the radials, which are key to both tuning and performance. The CHA Spike is quicker to set up and less fiddly than the Mega-Pod. The Mega-Pod can be a little springy and while not unstable is not rock solid stable. I don’t think it needs to be overbuilt. The threaded rods and lock nuts let you set the nut at a point before the rod bottoms out, and then tighten the rod against the radial lug. Don’t hesitate to put all three radials on one leg. It will work the same and it’s easier to set up that way. If you really needed it to be easier you could make lugs with extensions terminated in your choice of quick connector and then terminate your radials to match. I think that is overkill. The spirit of the WRC TIA is to have a working setup without a lot of fuss. The TIA Mega-Pod is more of a casual, less “tacti-cool” piece of gear, but it still effective.

With either setup you can be on the air in about 5-10 minutes. The CHA will set up faster, but neither is a chore. It hasn’t escaped my imagination that the CHA Spike is a really nice way to mount the WRC. In fact you could also imagine running the 17′ CHA Whip on the SB1000 and having a 80/40 setup with a better radiator.

Tuning/Matching

The user can get the WRC tuning very close by listening for peak noise on the band of interest. Once the user gets close it can be a bit of a chess match to get it zeroed in. The TIA is easiest to tune if you have an antenna analyzer or other SWR sweep device. I first used this antenna with a Xiegu G90 and the internal SWR sweep/analyzer was a big help. My old MFJ-259 makes it easier still. The key is being able to sweep around the band to determine if your current tuning is low or high. Once you are close it only takes small tweaks to move the resonant point. Without much fuss I was able to tune it on 80m through 12m. You can get it on 10m by shortening the whip, or just using the whip alone.

The tuning reference points in the WRC instructions will get you in the ballpark, but all kinds of external factors can change the amount of loading you will need. Tuning the stock setup with the three radials over average ground is what the instructions are based on. YMMV. As discussed in a previous blog post I consider a base-loaded whip to be in the “tuned circuit” family. The whip isn’t resonant, but the coil is making a resonant circuit for the frequency of interest. The apparent Q of the design is “moderate”. Not razor sharp, not super broad, but it can be touchy once you get the coil contact close to your tuning point. You probably won’t need a common-mode choke, but I always bring one because… RFI Happens.

The MPAS Lite is a whole different concept. It is not designed to show a low SWR on any band. The design assumes you have a matching device between your rig and the Hybrid-Micro. You might get lucky and see a sub-2:1 one one band and it might be fine. I typically see SWR values between 1.5:1 and 5:1 without a tuner. My 991A has a built in tuner and matches it with no complaints. I use a LDG Z817 with my IC705 and that matches it easily as well. With a manual tuner you are back to peaking band noise then fine tuning. My MFJ 901 will tune a watermelon, so it’s no news that it was great with the MPAS.

Radial/Counterpoise

The three 35′ radials supplied with the TIA are both the bare minimum, and also seem to be enough. I tried adding three bundles of three 20′ radials in addition to the supplied ones and it didn’t seem to help much. If I was trying to improve on the system I would try three 20m radials marked off at the 1/4 wave points for each band of interest. Just unroll the radials to the band marker. Of course this means you need over 60′ in each direction on 80m. Tuned radials have the potential to improve the performance of this system. It could be an interesting project. It also might not matter too much.

As for using a counterpoise or radials on the MPAS… one, zero, five, nine? In my experience the performance of these systems is unpredictable in the literal sense. If it gets you on the air it is working as advertised. Counterpoises in an untuned system are a funny business. When the radiator is not a resonant length I think you can do more harm than good trying to run tuned radials. I typically attach the CHA Radial and lay out about 25-35 feet of it in a convenient direction. If you are having tuning issues just change the counterpoise length/config or remove it entirely. Like a 9:1 end-fed the function of the counterpoise is debatable. It also might not have the same function in every deployment.

In a related topic, the MPAS isn’t limited to using the 17′ whip. You can attach whatever radiator you want and it will probably work. I believe the best to approach to sizing a wire radiator is to keep the suggested lengths for 9:1 un-un operation in mind. The transformer ratio might be different, but you still don’t want resonant lengths if band flexibility is on the menu.

Power Handling

Both matching units have loss issues that result in heat buildup. The WRC SB1000 is rated at 100W SSB, 50W CW, and 20W Digital. Similarly the CHA Hybrid-Micro is rated at 100W SSB and 50W continuous. I think a conservative approach to power output is wise here. You can smoke either device if you get too aggressive with the power. On the TIA the coil is trying to load a 102″ CB whip on 80m or 40m. This is a lot to ask and there are plenty of examples available on forums like eHam attesting to either deformation of the coil former, or outright failure when pushing the power ratings. On the Hybrid-Micro I would just assume the match at the feedpoint is bad, and that will make a lossy system worse, and that makes more heat. Heat Bad. I won’t run more than 35w in digital mode on either, and no more than 50w in SSB/CW.

Performance

I will be running a side-by-side test of the two systems soon. For now I will just give my impressions of them based on using them in the field using the same radios under similar conditions. I’ll get the bad news out of the way first: Neither is a fantastic antenna system when compared to almost anything else. Short radiators and lossy base loading are not a recipe for great antenna performance. However these antennas are not marketed as high-performance DX machines. Their calling card is portability and ease of deployment. In that respect they are both very good systems. Perceptions of on-the-air performance will have a lot to do with expectations, operating style, location, and whether making a specific contact at a specific time is essential. I have used both on POTA and POTA-style outings and they both hear much better than they get out. That’s normal. I felt like I was taking advantage of my “always loud somewhere” approach on every contact. I would be unable to work a solid 4-lander from RI (normally a given) but I might be getting 59+ reports from Kansas or Idaho. You will make contacts on either. You will make a mix of stateside and DX contacts. And no, these are not just pricey dummy loads.

The TIA got my initial performance nod based on my preference for tuned circuits over broadband transformers. But the TIA uses a whip that is half the length of the MPAS, giving up some if not all of that advantage. Also, if you run those TIA radials out to full length (recommended) you will need something like a 60-square-foot area to lay it all out in. The design is a little quirky and the user needs to be more involved with those quirks. It’s built out of hardware store parts and stainless wire. That isn’t a knock. Any ham will look at it and know that WRC puts a lot of care into their product and they are getting good value.

If you are intending to do a lot of band-hopping you will be much happier with the MPAS. Hitting “TUNE” and being ready on a new band is certainly seductive. It comes at the cost of additional system losses, but if you are making the contacts you want to make it doesn’t matter too much.

Straight Talk!

Aside from being a snap to set up in the field these antennas are providing regular HF capability to hams who may have given up on running a “real” HF antenna on their property. That’s great and the easy setup, small footprint, and low visibility are big selling factors. A concern I have expressed here and in other places is that there seems to be some confirmation bias among hams who haven’t worked with better antennas. I’ve seen excited reports of working monster Slovenian contest stations with one of these antennas and 10W, and I hate to tell you that is not a measure of *your* antenna’s performance. I’d also point out the fine work of Thomas Witherspoon, K4SWL, on his YouTube channel. He has many great real-time videos of an array of QRP rigs with different portable antenna solutions including the MPAS line. Note that he is almost exclusively calling CQ, hence pre-selecting stations that can hear him. If he was chasing stations with the MPAS he would need to take a very different approach. I don’t mention this as a negative on these antennas or the users. I mention it as a point that might be of help interpreting on-line reviews including this one.

Bugs and Observations

None of these issues are “deal-breaker” serious, but each antenna has some quirks and design issues:

I found that I needed to keep wrenches in my kit for the WRC because the 3/8″ hardware gets stuck together. It was a little annoying and I think a couple of inexpensive adjustable wrenches are a good accessory to keep with the WRC kit. Disassembly might also result in the SO-239 to 3/8 adapter coming loose on the Mega-Pod hub. I have a spare Hustler quick release that I am thinking of using to knock these issues down.

As I mentioned, the WRC Mega-Pod can be a little springy. Some care is required when deploying it, especially making sure you have slack in case of a trip or snag. The WRC whip isn’t going to take too many flops before it needs serious attention.

The MPAS Lite has fewer parts and doesn’t have much to go wrong. Still, I feel like the knob used to secure the counterpoise feels tacked on. It’s has red plastic knob and a small threaded rod which will only grab the eyelet on the CHA Radial by a corner. It doesn’t seem like it will make solid, reliable, electrical contact. It stands out mostly because everything else is so burly. Note: Unlike the SB1000 coil, the CHA Hybrid-Micro is not rated for mobile use.

WRAP

As you can tell I want to review these systems for what they are. They both work as designed to allow quick setup in tight spaces and allow operation across the HF bands. They both use standard 3/8-24 hardware allowing the user to mix, match, modify, and experiment with the provided building blocks. I haven’t touched on cost but the MPAS costs more than twice the tag on the WRC. Value is so subjective that I will just say that both feel like they are priced right. Also, I don’t feel like one is a big performance winner over the other.

If I was looking for an affordable portable setup to use around the campsite, for instance, The WRC TIA is a great option. I’ve covered the setup and tuning procedures. The result is being able to work on many HF bands with no additional tuner needed.

If I had to deploy something as fast as possible, with the least hassle, the winner is the MPAS by a large margin. You will draw very little attention, take up very little space, and get on the air. Even though a transmatch is required it doesn’t seem to be much of a hurdle. I used several matching units, including the MFJ-901, and they all worked just fine. You can also load a long wire, end-fed inverted vee, vertical wire… so the system is more flexible than the WRC.

I hope this post has been helpful. I have enjoyed using these systems, and can see why they maintain their popularity. As long as your expectations aren’t for some miracle system that gets big antenna performance in a small package then you can expect to get a lot of enjoyment out of either.