Man-Portable HF Antenna strategy

February 3, 2023 Julian OH8STN Antenna Testing, Chameleon Antenna, Education, Emergency Communications, Field Comms, Ham Radio, Off Center Fed Dipole, Portability & Mobility, Portable Ham Radio, QRP Portable 15

For the off-grid field radio operator with limited weight & carrying capacity, what antenna options do we have? Actually, quite a few! Let’s talk about smaller, lighter, and more efficient antenna options.


Hello Operators.
For the past few years, I have been guilty of choosing the most rugged antenna options available. At some point, reducing size and weight became more important than the robustness and the survivability of my portable antennas. The thing I realized is “If my antenna was lighter-weight and truly man-portable, it would be possible to carry redundant, more lightweight, and more efficient antennas. We could also benefit from reducing the overall weight of the station carried! That’s where I am now.

The antenna in the image below is the OCF40 from Chameleon Antenna. The OCF40 is an Off Center Fed Dipole OCFD covering 40-6M. Most of you might not know that the OCF40 is my favorite man-portable antenna! This is a fact, but one which has not been promoted very well.

Below we can see a drawing of the OCFD deployment in practice. The off-center fed dipole is feed off-center with one leg about 1/3 the way from the center. The entire antenna is still a half wavelength on its primary frequency. More wire in the air right?
Much of my learning about the OCFD comes from Serge Y. Stroobandt, ON4AA at groups.io. If you are interested in OCF antenna builder/experimenting, I’d suggest joining that group. There is a mix of experienced and clueless (like me) Operators, all passionate about the OCFD. All are willing to share their own experiences.

My typical OCF deployment uses a carbon-fiber mast as a center hoist. The legs are achored to the ground with tent stakes, or trees if available.

Man-Portable weight savings

Normally my man-portable off-grid ops are either on the fat bike or hiking with the dog. In either situation, carrying capacity is always limited. If this is a multi-day excursion, shelter food, perhaps water, plus gear for Snapper (my dog) need to be taken along as well. If it is cold (near or below freezing), the loadout will again grow in size and weight.

Snapper and our Nortent Tipi 4 tent in Lapland

The point here is the size and weight of the antenna gear. Rugged antenna equipment ALWAYS means heavy antenna gear. The Chameleon MPAS, Hybrid, EMCOMM, FLOOP, TD, … are all great albeit heavy antennas. The MPAS is extremely easy to deploy, often making its weight forgiveable (to an extent). Still, there are questions one should ask themselves.

  • Is it better to carry a rugged, heavy, broadband antenna, or an ultra-lightweight and more efficient antenna?
  • If the goal is reducing weight, reducing loadout, and minimizing the comms gear, why on earth should heavier antenna gear than necessary be carried?

Often, the honest answer is “It is stupid to carry unnecessary weight!”.

Go-To antenna

My go-to antenna for regional communications has been the Chameleon MPAS 2.0. Essentially, it is a rigid random wire vertical end-fed antenna, which is extremely easy to deploy. My thinking behind this antenna was cold weather deployment. The longer it takes me to deploy a fiddly antenna in sub-freezing temps, the more likely I am to get frostbite (again). The fast deployment also means a shorter time to get on air. These are fair points, but, … The downside about the MPAS 2.0 in its various configurations, is its size and weight. It will surely survive anything mother nature throws at it. The question though; Do I need that level of survivability!? Perhaps not.

In the following video, you can see a man-portabe rapid deployment of my “Big Gun” station. The antenna is the Chameleon MPAS 2.0 with MIL EXT antenna extension. The station was very easy to set up. It was also very fast to set up. The station consisted of the Icom IC-705, PA500 amp, Chameleon MPAS 2.0, and Microsoft Surface. One will already notice how the station has decreased in size over the years. A further reduction in station size and weight can only be a good thing.

Size matters

What if I were to swap ruggedness for greater efficiency and weight savings, at the expense of antenna survivability? Would this be an acceptable trade-off? Indeed, I think it would be!
Think of it this way. The smaller and lighter the comms gear we carry, the easier it is to get ourselves to our operating location. The more weight we have to carry, the more difficult it is to achieve our field communications goals.
Imagine if all we had to carry was a radio and antenna. There would be more room for off-grid power supply for example. Imagine having a lightweight & efficient antenna, instead of a heavier broadband antenna. One could run less output power while maintaining reliable communications. Lower output power, means longer battery life, or carrying lower capacity, lighter weight batteries.
This is already a no-brainer.

Review of the OCF40 from Chameleon

In the video below, I field-tested the Chameleon OCF40. The Chameleon OCF40 comes from their “Pocket” series of portable antennas. This series of antennas was designed for ultra-light QRP portable operation. These are full-size antennas with full-size performance but built with lightweight materials and miniaturized components. These antennas complement the new lineup of lightweight, battery operated, Man Portable HF portable transceivers from Icom, Lab599, & Xiegu, …

In the above video, I deployed a carbon-fiber mast as a hoist for the dipole. Performance was actually better than expected. This configuration was lighter, easier to carry, simple to set up, and easy to tear down. My only complaint is Chameleon Antenna does not make an 80 meter or 60-meter version of this antenna. If fact, 95% of the ham radio community see little point to anything below 20 meters for POTA or SOTA activations. Chameleon Antennas rarely sales man-portable antennas designed for 80-40 meters. There is the F-LOOP, but it is too big for man-portable ops. This is a bummer (at least it was a bummer, keep reading).

Here are the key points of the OCF40 from Chameleon

  • Weighs literally nothing
  • It covers 40, 20, and 10 meters plus some others with a tuner
  • It is very efficient on 40 & 20 meters, and has reasonable performance on 10 meters.
  • It is completely waterproof
  • Handles 50 watts

The reason for mentioning this Pocket series antenna from Chameleon is its size, weight and performance. This is a man-portable antenna, built for operators who have a critical need for ultra-lightweight portable antennas. The only problem with the Pocket Series of antennas from Chameleon is the selection. There just isn’t a wide selection of these ultra-light & efficient options from Chameleon Antenna. This leaves me with two options, building the antenna myself, or finding some other manufacturer who already does.

Changing my antenna strategy

Regional emergency communications is very often done on the low bands. 80 meters, 60 meters, & 40 meters NVIS. Longer-range communications is usually reserved for 30 meters, 20 meters, 15 meters, … Looking back at some of the disaster deployments, where amateur radio played a role, we see operators trying to use DX bands and configurations, for regional communications. Ths shows us a lack of understanding about regional antenna work. It also shows us how antenna manufacturers are ignoring the regional EMCOMM & Preparedness communications space.

With that said. regional EMCOMM is a very niche part of amateur radio. This may be the reason we don’t see efficient yet portable low band antenna options, from manufacturers like Chameleon. Thankfully we do have other options.

N9SAB Antennas

Thankfully, there are enthusiasts like Tim Ortiz, N9SAB (http://oh8stn.net/n9sab) making exactly the lightweight, waterproof selection of wire antennas we need, for extended fixed and/or man-portable field operations. N9SAB has a variety of man-portable antennas like the Off Center Fed Dipole, G5RV, end-fed half wave, and traditional dipoles, … All of these antennas have extreme portability in mind. These are different from the fair weather POTA and SOTA style of antenna we often see on YouTube.

My man-portable antenna requirements

As you can see in the image above, magnetic loops, vertical antennas, and now lightweight wire antennas have found a place in my communications toolbox. Here are the key requirements of man-portable antennas.

  • Pocket sized
  • A half wave or more
  • 100-watt capability
  • Weighs nearly nothing
  • Takes up nearly no space when packed away
  • Waterproof
  • Either efficient balun or with no balun
  • No polycarbonate enclosures
  • Can be easily configured for NVIS or DX

N9SAB has several antenna designs which fit my requirements. He has both ultra-lightweight QRP versions and 100-watt versions of the same antenna designs. You’ll see the following two version of the N9SAB OCF antenna for 80 meters and 40 meters on the channel soon.

80 meter OCFD

This 80m version seems like an excellent choice for Winlink! Its primary band is 80 meters, yet has excellent performance on 40 meters as well. The other bands (compromise) are gravy. With this antenna, I could easily set up an 80m tri-mode Winlink RMS on 80 meters and 40 meters without a tuner or complex antenna switching. Using a “Cheap” radio like the Xiegu G90, this 80-meter OCFD and a Mini PC would be the perfect solution for a budget multi-channel, multi-band Winlink RMS.

This is the 80-6M 100W HF Antenna Off-Center Fed Dipole. An efficient dipole for fixed and field radio Winlink work has been difficult to find. This antenna should be quite efficient on 80 meters, but a good compromise on the other bands. Being a full-sized antenna, my belief is it will still outperform other short broadband antennas like the Chameleon MPAS 2.0 with MIL EXT.
The 80-6 meter Off Center Fed Dipole: can be found on eBay (Ebay affiliate link) https://ebay.us/sw1M1U

40 meter OCFD

The 40 meter OCFD version seems like an excellent option for 40-meter data mode communications like JS8Call. Imagine being able to run JS8Call on your FT-818, IC-705, KX2, and TX-500, … while being able to switch over to 20 meters for DX on data or voice, all without a tuner. Just a radio and antenna! We loose the antenna tuner, and gain more performance. The additional bands are gravy.

The 40-6 meter 50-watt version of the antenna has been my primary fixed station (JS8Call) antenna for several months now. It freed up my 80 meter full wave skyloop for more critical use. Although incredibly similar to the Chameleon OCF40, we still need to revisit the 100-watt version on the channel again soon.

You can find the 40-6 meter off center fed dipole on eBay (Ebay affiliate link) https://ebay.us/SoPiyb

The following PSKreporter maps are examples of my daily JS8Call performance (from home) using the 40-6 meter version of the Off Center Fed Dipole from Tim Ortiz N9SAB. The antenna is driven by the Icom IC-705 & PA500 running about 30 watts. There is no day passing by where my station isn’t heard on several continents. Please pay attention to both TX and RX spots on these maps. The antenna hears as well as it transmits. Naturally, more wire in the air is another benefit over its lossy broadband cousins.

I have an array of these lightweight, portable antennas coming in during the first half of 2023. I’ll start with the 80-6 meter OCF. Then move to the 40-6 meter OCF, before testing several other man-portable, lightweight designs.
Please take a look at the selection of antennas from Tim Ortiz N9SAb on eBay (http://oh8stn.net/n9sab) . These are affiliate links, so you’ll also be supporting my work by using them.

Broadband antennas: Another perspective

For the past year on the channel, we have discovered the benefits of energy efficiency for off-grid field radio ops. Radios like the Discovery TX-500, Icom IC-705, the Elecraft KXx series, and the (Tr)uSDX have given us the ability to reduce the amount of battery and solar power required to field our stations. If fact, ridiculously high current consumption has added to and taken up a large amount of our load carrying capacity in the form of batteries. This is usually an afterthought, but more current-hungry systems, require higher-capacity batteries. Can we think of anything else adding unnecessary weight to our kits? I can think of one area where we can improve. Antennas!

Antennas can serve us in several ways. They can be fast and easy to deploy. The can reduce our workload and help prevent operator fatigue. They can be broad-banded enough that we only need to carry one antenna and a lightweight tuner for all of HF. This can reduce loadout and time to get on-air. In contrast, the broadband antenna can also force us to run higher power. It is a trickle-down effect from there.

For as many benefits a broadband antenna brings us, they also introduce some negatives to our field radio ops. Broadband antennae introduce losses to our stations. Losses which can be acceptable in some situations, eg regional communications. In other scenarios, the losses are intolerable. Here’s an example. of a signal coming in on a dipole. The signal is 3db up versus the shortened broadband antenna deployed at the same height. What was a strong signal on the dipole, is in the noise on the broadband antenna. Why? Because for the convenience of a broadband antenna, we give up some efficiency. For regional comms, I don’t care too much. Regarding weak signal work, it can turn into a nightmare. Either way, we need to have more/better antenna options.

We usually compensate for losses with narrowing filters, more power, and higher gain, … If conditions are bad enough, more power will be required on both sides of the QSO. This takes more energy from our battery storage. It may also force us to increase our portable power systems (battery and solar), to field our stations for the same amount of time, had we just used a more efficient antenna. Again, the trickle-down effect.

A poor antenna causes us to run on higher power, which causes us to use more battery, which causes us to increase battery capacity, which causes us to carry more weight, …

Wire antennas

At the end of the day, if we CAN put a dipole in the air, WE SHOULD put a dipole in the air. This is especially true as we now have lightweight carbon-fiber masts weighing nothing, available for deployment. Where a self-supporting broadband vertical was once the logical solution to our rapid deployment problems, a dipole or, EFHW with a carbon-fiber mast could be just as simple to deploy. Never mind being able to quickly swap out between regional NVIS and DX configurations on the same antenna. The benefits of a wire antenna are beyond reproach. The hardest parts of this endevour should be choosing which wire antenna to use, building or buying, and configuration.

Final thoughts.

I’m not saying there is no place for broadband antennas, 1/4 wave verticals or the other types of antennas we have seen on this blog and YouTube channel. The 1/4 wave vertical has shown us epic levels of performance on HF. The broadband antennas have definitely made field deployments easier. Unfortunately, for the man-portable operator, broadband antennas have also increased the amount of weight we carry. I don’t need an antenna capable of 300-500 watts, if my gear can only generate 10 watts, 50 watts, or 100 watts.
Ultimately, the key points here are increased performance and weight reduction! By limiting the size and weight of our antenna, or other pieces of gear which could be substituted with something smaller, lighter and more efficient, we increase station performance, minimize operator fatigue, and field a more efficient HF station.

What are your thoughts?

73
Julian oh8stn
YouTube: https://www.youtube.com/@oh8stn
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Blog: https://www.oh8stn.org

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15 Comments

  1. Here’s another viewpoint – the wire antennas in the field are cumbersome. You need a lot of space and time to deploy and recover these antennas. I have a couple N9SAB antennas, and they are high quality products indeed. Unfortunately, they tangle like crazy and I spend so much time keeping them straight or separating legs before they get pulled right. A vertical whip like the MPAS is much faster and more predictable.

    • I do not disagree with you Kevin. However, when comparing the weight of the N9SAB OCFD and MPAS, the OCFD wins. It is a fraction of the weight of the MPAS. I agree that wire antennas need more attention and can take longer to deploy. That is my biggest concern. The hope is the performance improvement over the MPAS will more than make up for the increased deployment difficulty. The OCF outperforms the broadband antennas quite easily. Like you said though, managing the wire is something which needs to be sorted out.
      Good feedback. Thanks for reading and commenting.
      73
      Julian oh8stn

  2. I agree whole heartedly with you’re thinking. I like to have a minimal basic system as possible, and support it as required. I have been using DIY EFHW antennas for a couple years now. Usually a 10 watt version for qrp with an X-6100, but also a kit with a 100 watt version if I need to take my IC-7300. I use a telescoping fishing pole (light and easily deployed) and stakes for a sloper and have had good success. Keep up the good work, always keeping us thinking.

    • Thanks for this comment.
      Sometimes putting out these ideas is quite worrying. One can never know the reactions from the community. So far so good.
      Thanks for reading, commenting and for the kindness.
      73
      Julian oh8stn

  3. Being out in the field more, and now having a 705, even though we have the Icom tuner, has shown us how nice a dipole can be. The dipole performance has been better than our EFHW antennas, and the lack of RF coming back to the radio even nicer. The daughters and I are operating mostly CW, so don’t normally use the whole band. Using QRP has shown us a few things now, one of them is that a balanced antenna is really nice with the efficiency. We have though about “Doublets” and would like to try some ladder line soon as well. As we do more, weight I’m sure will be a considerations.

  4. For years I have built and used all manor of wire antennas. My go-to for field work is the dipole doublet, ladder-line fed, with a small tuner at its base, powered by a bias-T through the coax. For < 50 watts, you can get away with 300 ohm ladder, but must go up to 450 ohm ladder for higher wattage. You can also get away with a 40M version to work 80/60M if you take the 2 ends of the ladder, feed them both to the center conductor of the tuner input, throw out a 60 foot radial on the other side, and call it a Marconi. If you use the Silky copper wire, it doesn’t (rarely) tangle. The small tuner is a LDG in a plastic ammo box where I also carry a couple baluns as needed.

    73, Jamie
    WB4YDL

    • Jamie, Where do you find the Silky wire and which LDG tuner do you use? Thanks and 73, Steve W1LV

        • Thanks, Julian. I had my eye on the FlexWeave from that company: #14 polyethylene black jacketed FLEX-WEAVE TM, 168 copper strands for high abrasion/rodent resistance. Link: https://www.davisrf.com/antenna-wire/flexweave.php N9SAB will make an antenna for me if I send him the wire. (I have made many myself, but he has some intriguing ideas I would like to explore for my own use, of course)

          That T1 tuner is now on my “buy list”

  5. Julian, great content as always. Naive question for you. Why choose an off-center fed dipole over a conventional dipole if the mounting configuration will essentially be an inverted V in either case for the choice of bands and type of deployment you are using here? Curious about advantages/disadvantages.
    Tripp Griffin
    KO4ROU

  6. Great discussion. On my SOTA and backpacking I use one of these:
    () 130’ EF (80m and up), QRP w/ Ft140-31 8:1 winds, hand built
    () 65’ EF (40m and up), QRP w/ FT140-31 8:1 winds, hand built
    () 40m dipole with common mode choke, QRP
    () SOTABeams band hopper-4 (80/40/30/20) linked dipole, I think it’s good for 100W

    I have not seen a benefit of using a counterpoise on my EndFeds – I stretch the feed line out and don’t run a choke. The EF and QRP dipole are less than half the size and weight of the SOTABeams dipole. I sling a fishing weight and 10lb test fluorescent fishing line in the trees to feed the wire. I’ll bring my compact fiberglass mast if no trees. I’ve seen no appreciable difference in performance with the broadband EF vs tuned dipole at low powers. The steep transform ratio of the EF can be an issue here though. Dipoles are naturally efficient because there is little need for impedance transformers (tuners are impedance transformers too). Keep the antenna more than 1/10th wavelength up to keep the fields from warming the worms.

    Weather proofing my own builds is a pain. That alone is with buying a nice pro built unit. I’m probably not going to wind any more myself!

    Wire mgt is key and takes practice. Figure-8 on your winder or fingers (“antlers”). Always think which way you want to unwind and which direction to throw the line to feed. I screw this up too often. Wet trees suck up power.

    To any operator I highly recommend building a few of your own antennas if for no other reason than to appreciate someone who does it better than you!

  7. I have been building OCF Dipoles and Linked dipoles as NVIS antennas for over a year now and have found that tuning them for the height that you plan to deploy them is critical for efficiency. I have been leaning toward 15 feet at the feed point for simple, quick, rapid deployment situations. I am not sure at what height Tim Ortiz tunes his antennas, but I would recommend that you decide on your most common deployment height and tune accordingly. Tim makes great antennas and to make them work most efficiently you will need them tuned for your specific needs.

  8. Hi Julian. Thanks for sharing the information. I’m learning a lot! I have a question, what is the model of the fiberglass mast you are using in this video?

  9. I have a prototype OCFD by Tim. It came equipped with removable extenders for bands below 40m and a heavier duty balun. The antenna is brilliant.

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