Lightweight BackPack Radio Guide (from Harlikwin Ep 3)

Harlikwin, from Episode 3 (manpack/milpack) just posted this commentary on Backpack radios….enjoy!


Lightweight Pack radios
I’m writing this piece from the standpoint of needing a lightweight back-packable radio that I can take with me on overnight and several night outings so weight and power out are critical considerations.

My definition of lightweight is that I will use the target weight of approximately 5lbs or less to design a lightweight packable radio system (minus antennas) capable of SSB use.

Thoughts on power
One thing I will talk about is what I consider useable power levels, and I acknowledge that this topic is highly divisive so I’ll put down my opinions on it and people can disagree with me if they like (and I know they will).

I will begin with a simple fact: nearly all of the worlds military’s have for four decades decided on a ~20-30W power level for their portable SSB backpack radios as the best compromise for reliable man portable SSB HF communications and in my opinion for reliable SSB work this is probably the best compromise between power out and weight and power consumption.

However, very few of the examples examined here offer a full 20W output as a stock configuration, so some sort of amplifier is required. I will fully acknowledge that SSB contacts CAN be made with very little power under the right conditions, been there done that, but in general it is my experience that there is a big difference between making SSB contacts with 5W and 20W, not merely the measly 1 S unit of power as many folks with come back with as a counterpoint.

I will break it down as saying as 5W SSB is great for CW and data modes such as PSK31 but generally unsuitable for making reliable SSB comms. 10W of power is again great for CW and data but still a bit marginal for SSB. In my opinion and experience, 20W+ is the best range for low power SSB under most ionospheric conditions.

That being said I will jump in and examine the commonly available options in the new and used ham radio market, the list isn’t meant to be comprehensive but I feel like I’ve covered most of the basic rigs available.

The configurations
I will discuss 3 different configurations, the base radio and what it weighs (with batteries) and then 20W and 50W configurations with an outboard amplifier. For the sake of comparison I have chosen the MX-P50 Chinese amplifier and a Zippy 4.2Ah LiFePo4 external battery and various elecraft or LDG ATUs (noted) for the comparison to keep the configurations simple, all weights posted include internal batteries if available as well.

Certainly one can decide if 4.2Ah is enough capacity to run the system for the required time, but I’ve used it as convenient placeholder. It should be noted the amplifier listed does require a very good antenna match, hence all configurations will include an ATU. Alternately I suppose you could use a perfectly matched antenna, but in practice in the field its too much of a pain IMO, a tuner is the same weight or less and much easier to use.

The contenders

KX3 HF+6m
The KX3 is often bandied about as the do it all super lightweight wonder radio for backpacking, SOTA and other lightweight activities. It certainly boasts a lot of great features such as IF DSP, internal ATU and batteries and fancy things like CW/PSK31 decode, AND it is lightweight and compact to boot. Unfortunately the advertised weight is listed without internal batteries, or optional things like an ATU or optional 2m radio module or extra filters or the “optional” mic so it is a bit misleading.

Also unadvertised is the fact that to realize its full 10W of output power it does require an external 13.8vdc power source. With those two caveats however it is still very lightweight and does put out a very usable 10W of power. With an external LiFePo4 battery and internal batteries and ATU option the weight comes in at 3.4lbs for 10W output which has the best power to weight and volume ratio at that power option of the radios listed. Adding an external 20 or 50W amplifier is certainly an option however to my knowledge one must also add an external tuner to utilize it with the KX3. With a MX-P50M tuner and outboard T1 or Z817H ATU the weight climbs to 4.9lbs and 5.5lbs for 20W/50W respectively, we can use the outboard battery to run the amplifier and the internal batteries to run the radio.

The one area where the KX3 does fall short compared to all the other options is cost, the price for the various configurations is roughly double that for any other configuration running from about 1430 for a loaded (ATU/Filters/mic) base configuration to about 1800 for a configuration with the amplifier and external ATU.

The FT817 was the first QRP radio marketed as such, with a very small footprint for the base radio and a 5W power output, achievable on internal batteries, it took the low power world by storm. However almost all later radios had 10W+ power output after folks became frustrated by the FT817’s lack of SSB performance, also partly due to lack of power and any sort of speech processing which should absolutely be included (easily fixed by aftermarket mics or kits).

It should be noted that the FT817 is the only radio reviewed that can cover the whole frequency range from HF to UHF, which may make it attractive to some. The base configuration with batteries weighs in at 2.5lbs for 5W of performance (I should note the kx3 is a bit lighter ~2lbs running 5W). For effective HF SSB performance the FT817 benefits the most from an outboard amplifier, using theMXP50A amp and a LDG Z817/Z817H tuners one gets weights of 5.5 and 6lbs for 20W/50W respectively.

Essentially the FT817 is half a pound more than the KX3 at every turn and volumetrically comparable to the KX3 configurations. Cost wise it depends, used FT817’s vary widely from ~300-600 USD so the configurations can run from 800 (assuming a 450 base cost) to ~1000 USD depending on if one gets a new or used FT817 to start off with.

IC703/703+ HF+6m
The ICOM703 comes in a 10W configuration with a built in narrow range autotuner. This was a very popular radio for some time but was discontinued by ICOM for some reason.

At first glance it is very comparable to the KX3, though the KX3 boasts features like IF DSP vs AF DSP and CW/PSK decoding. Also the stock IC703 with external battery (no internal batts) weighs in at a hefty 5.5lbs and volumetrically is comparable to the 20 and 50W configurations of the FT817. If we start adding things like the amplifier and external ATU the weight rapidly climbs out of “lightweight” territory.

The 703 isn’t a terrible choice if you can find one cheaply, and it is nicely integrated aside from the external battery, its just going to be a bit heavier than other options. For those interested add about 2.5lbs to add the 50W amplifier and Z817H tuner for a final weight of ~8lbs and about double the volume.

Cost wise since its discontinued varies quite a bit, anywhere from 500-700 on auction sites in the authors experience and then 50 dollars for the battery, in this sense it’s a pretty good deal if one decides 10W is all that is required for the user and one doesn’t need the fancy features and light weight of the KX3.

SG2020 HF only
The SGC SG2020 is sort of the oddball, like the 703 it is no longer produced, it had a mixed reputation for problems and perhaps that is why it is no longer made.

It is a genuine 20-25W radio though it also needs an external battery to run and an ATU is again recommended to match field antennas. In a configuration with our battery and a lightweight elecraft T1 ATU the weight comes in right at 6lbs; not terrible given the power out it compares reasonably well to the amplified KX3 and FT817 based configurations in terms of weight and volume.

Cost wise since its discontinued varies quite a bit, anywhere from 500-700 in the authors experience and then 50 dollars for the battery and $160 for theT1 ATU.

TJ5A 4 HF bands only
A recent interesting offering from youkits targeted at the SOTA and backpacking crowd and running 20W power out. The base rig is fairly barebones, but it is offered with a clip on 4AH LiIon battery pack.

Combine this with an T1 ATU and the rig becomes a very lightweight 4.3lb 20W rig, it has a superior power to weight ratio at the 20W power level to every other rig examined. It is fairly basic however and does not cover all bands, it comes in two configurations of 40/20/15/10m and 40/20/17/15m or fancy things such as speech processing (though one presumes this could be user added like on the FT817).

The fully assembled radio with T1 ATU and battery comes in at 610 making the cheapest option.

No discussion of QRP radios would be complete without discussing antennas. There are a ton of options in this regard, from ultra-lightweight wires to fancy portable vertical systems such as the buddistick and buddipole.

From the authors standpoint of camping antennas, they have to be lightweight and fairly idiotproof. The paar EFZ trail friendly comes in at .5lbs advertised and will handle 25W power on 40/20/10m. If ones camping site has trees (this is not always possible for me) then it is an ideal antenna to take to throw in a tree. Comparable designs include the EARC antenna kit from Hawaii.

The buddistick is another popular option, and one that can be emplaced without supports, though it weighs a bit more. It should be noted that while both of these options can be used without tuners in theory, in my experience the EFZ and other multiband designs will be mostly resonant on only one band and close on the others which necessitates some sort of ATU (unless one is very confident of their finals).

It is a similar story for the buddistick, the swr will vary somewhat on the surrounding environment, therefore either an antenna analyzer or ATU is required for the best match and frankly the ATU’s weigh about the same as analyzers and are easier to use with presets for the buddistick.

Concluding thoughts.
The right radio for someone really depends on primarily on budget and operating style. If you are a drive to your operating site and setup on the picnic table type of operator, a few pounds weight means absolutely nothing to you (why are you even reading this?).

However, if one seeks the lightest weights possible at any cost and is willing to give up a bit of SSB power, the base KX3 with an external power pack is probably the best option. If one wants a highly flexible, highly modular and lightweight setup that can be heavily customized ala carte, the FT817 based platform is the best choice as it can run from a uber lightweight 2.5lb 5W CW rig to a 6lb 50W SSB rig and a variety of configurations in between.

If one requires a cheap 20W SSB radio and lightweight, then the youkits offering is very tempting both in terms of price and performance though it is limited in terms of band coverage. However if budget and frequency coverage are desirable then the SG2020 and IC703’s if acquired at the right price can also be good choices.

What I’m doing in case you care
I got into a used FT817 for a very good price a few years back, so frankly upgrading that has made a lot of sense for me since I didn’t pay anywhere near “new” prices. I really do like the flexibility of the platform, if I really need lightweight I can take the radio and the internal lithium pack I run and it is enough to work CW barefoot (or data if I did that sort of thing) for a few nights at a weight of 2.5lbs.

I can add an outboard Z817 tuner or external battery if I’m concerned about antenna mismatches (and I usually am) or need more runtime for a pound more at 3.5lbs. And then If I feel I need more power, or need to take a SSB radio I can add the Z817 tuner MX-P50 amp and the zippy battery for a 5.5lb 20W out configuration (I use 20W since I am limited by my tuner and by battery life).

What I would do if I were starting from scratch
If I were to do it using “new” components and had a pile of money to spend I would very seriously consider the KX3, it would be as good on SSB in the stock configuration (5w), but it would weigh a bit less (2lbs if numbers can be believed) and have an internal ATU compared to my current setup.

If I decided I needed lightweight and a bit more power I just grab a battery pack which gets the weight to 3.4 lbs. Then if I decided I needed more talk power I’d grab the amp and outboard tuner for a weight of 5.5lbs and 20 or 50W out (assuming I used the Z817H tuner so I could run 50W). The only thing I would really give up vs the KX3 is the 440mhz capability, which I really don’t need in the wilds (though 2m has come in handy once in a while).
However, If I weren’t daddy warbucks, I would also very seriously consider the TJ5A as a runner up for a man portable SSB rig given its very low cost and high power output. The band limitations might bother me a bit, but realistically one can certainly get by without 80, 30 and 12m, and the 40/20/15/10m configuration nearly perfectly matches the paar EFZ.

What I wish one of the major manufactures would build.
A waterproof(rainproof, not diveable), durable 20W all mode/band rig that weighs less than 5lbs and is compact with a wideband ATU and with an internal battery bay or clip on Lithium battery pack that can run the rig for an hour or two on SSB (say about the size of the IC703 with battery included max).

There should be a provision for vertically mounted HF whip for manpack use, and possibly a separate VHF/UHF whip (though that could be switched internally I suppose) and a front panel mounted BNC connector. There should be a 3 position switch VHF/HF/BNC to indicate where the active antenna is connected.

Also there should be effective DSP, and there should be a USB connector for DATA. And it should cost no more than currently priced FT817

Thanks Harlikwin for sharing with the Fo Time Audience!

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