W7KI Manpack Radio

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This article details how I set up a HF/VHF/UHF manpack radio.



Design goals

Radio RF Output:

Minimum of 20W, preferable to have optional 50W+ available if needed

Radio Frequency coverage:

HF, 6 meters, 2 meters, and 70cm

Radio Modes:


Radio receive current:

preferably less than 700mA


10-500ohm minimum, preferable little to no idle current


sufficient to handle a weekend without recharging


Battery, AC, or solar


Vertical or dipole with optional voltage balun


Small netbook capable of digital modes


Everything fits within a pack suitable for airplane carry-on (21x14x10").

All items:

Weight as minimal as possible !


$2500 neighborhood

The Radio

Here is a quick rundown of the radios I considered:

Military radios

I looked at the PRC-104, PRC-132, PRC-138, PRC-320, PRC-1099, PRC-2000, and AEG SE-6861.
All of them are good radios. Only problem is I want HF/6/2/440 so I'm stuck
with looking at amateur radios.

Lab599 TX-500

New 2020 !
Modern 10W HF/50mhz all mode portable transceiver with a rugged aluminum case.
Made in Russia. Worth checking out. Current price $790.

Icom IC-705

New 2020 !
10W HF/6/2/440 all mode portable SDR transceiver with a touchscreen display.
Matching pack and radio-specific ATU available.
If I had to re-do this project today this radio would be under serious consideration despite being 10W.
Current price $1300.

Vertex VX-1210

This is a commercial radio ($1400+, 7.1lb w/batt, rx: 500mA, tx: 3A/5W, 5A/20W)
Very tempting but is HF only. Has option for internal autotuner and can be
set up for VFO operation. Battery is 14.4v 4AH.

Mobat Micom 3 Pathfinder

This is a 25W commercial radio. Excessive cost for this project. Otherwise a great radio !

Outback radios (QMAC, Barrett, Codan)

QMAC HF90 excessive cost & no longer made, Barrett 940 too heavy (18.5lbs w/tuner battery)
Barrett 2040, Codan 2110 excessive cost.

Yaesu FT-817ND

Portable amateur radio ($600, 2.6lb, 8-16v, rx: 300-500mA, tx: 2A/5W)
Tempting, and would pair nicely with the LDG Z-817 or Elecraft T1 tuner.
Only problem is I want 20W+. This could be accomplished with a Tokyo High Power HL-45B
amp ($400, 3.4 lbs, 8.5A/45W, 160-6m) + LDG Z-817H tuner.
This is a viable combination and has the benefit of low RX current.

Icom IC703+

Amateur radio (discontinued, 4.4lb, 9-15.8v, rx: 300-500mA, tx: 3A/10W, HF+6M)
Nice radio, big and easily readable display, built in autotuner. Wish it did 2m/440
like its bigger brother (IC-706).

Elecraft KX3

Portable amateur radio (new to market, 1.5lb, 8-14v(?), rx: 150-???mA, tx: ?A/10W, HF+6M)
Great display and control layout located on what would normally be considered the "top"
of the radio which gives ample room compared to other radios. Built in autotuner. CW paddles
right on front of the radio. I would have liked to see a little more than 10W however its
certainly a reasonable and usable amount of power (and better than 5W). Has option for
an external KXPA100 100W amp and KXAT100 tuner. Overall it is an exciting product and I
probably would have bought one if I wasn't looking to have 2m/440 in the same radio.
I don't know if it supports CTCSS for 10m FM repeaters and CTCSS/DCS for 6m FM repeaters.

Icom IC706MK2G

Mobile amateur radio ($800, 5.5lb, 11.8-15.8v, rx: 1800-2000mA, tx: 20A/100W)
RX current way too high, VHF frontend easily overloads. Nice display as with the IC703
above. The RX current is a deal breaker for battery ops.

Icom IC7000

Mobile amateur radio ($1200, 5.1lb, 11.8-15.8v, rx: 1300-1600mA, tx: 22A/100W)
Nice radio. RX current better than IC706 but still a little on the high side for battery ops.

Yaesu FT-897D

Mobile/portable amateur radio ($900, 8.6lb, 11.7-15.9v, rx: 600-1000mA, tx: 22A/100W)
HF/50 MHz:5 watts = 4.0-4.7 amps 10 watts = 5.3-6.4 amps 25 watts = 7.3-9.2 amps 50 watts = 10.6-12.9 amps
144 MHz: 5 watts = 3.4 amps 10 watts = 4.2 amps 25 watts = 6.3 amps 50 watts = 9.4 amps
420 MHz: 5 watts = 4.2 amps 10 watts = 5.6 amps 20 watts = 8.7 amps
Designed for field ops and has room for internal batteries (13.2v, 9AH) however the batteries
add an additional 6.5lbs to a radio which is already heavy at 8.6lbs. One option is to run your
own external battery which gives you room to install an internal 120V power supply. Overall
I really like this radio but its ruggedness will cost you in weight. You can get the FT-857D
(sacrificing the 897's rugged case and internal battery space) and save 4lbs on your back.

Yaesu FT-857D

Mobile amateur radio ($800, 4.6lb, 12.4-15.2v,
rx: 600-1000mA (spec) 650-700mA (green/red backlight) 590mA (backlight off)
tx: 2A/5W 5A/15W 22A/100W)
Unlike the FT-897D above, this radio does not come with a TCXO. By the time you spend $100 on
the TCXO you end up with about the same radio as the FT-897D for the same price. Comparing the
FT-857D to the FT-897D has some pluses: 4lbs lighter, detachable head, and easier to mount mobile.
The minuses are we don't get the rugged case and battery space. I don't think either of these
minuses will matter as the radio and batteries will end up in a pack. One other thing to note is
both the 857 and 897 will automatically limit the radio to 20W when running on battery power
(by grounding the brown wire on the power connector).
Spec says voltage is 12.4-15.2, manual says 11.73-15.87.
The 857's signal will start sounding bad at about 11.75v.

Given everything above it came down to deciding between the FT-857D and FT-897D.
I chose the FT-857D because its 4lbs lighter than the FT-897D. Every pound counts when backpacking !
The radio is best equipped with: tcxo-9, keypad mic, (2) W4RT/inrad.net filters.

The Tuner

For honorable mention we have the long-discontinued Kenwood AT-130 which is a very small 80-10m(+WARC)
manual tuner (6 x 2.4 x 6.3 inches, 3.5 lbs.). For field ops I prefer a small autotuner. Yaesu makes the
FC-30 ($170, 17-150 ohms, 3.1 x 1.8 x 10.2 in, 2.2 lbs) however its 17-150 ohm tuning range is quite
narrow compared to the LDG product line.

Here is the breakdown of the LDG products I looked at. All of them have latching relays.

$200 LDG YT-100 for 857/897 100w 4-800 ohm 7 x 7 x 2 1.5lbs
$200 LDG AT-897+ for 857/897 100w 6-800 ohm 11.5 x 3.25 x 1.5 2.0lbs
$160 Z100+ ? 125w 6-800 ohm 5.5 x 5.5 x 1.5 1 lb w/o batts
$170 Z11pro2 6-1000 ohm 7.7 x 5.0 x 1.5 1.5lb w/o batts

I ended up going with the Z11pro2 as it can autotune based on RF sense which keeps the CAT and ACC ports free. This is good because we
need both ports for our data interface. Another bonus of RF sense tuning is it makes the radio PC-ALE capable provided the antenna is
tunable on whatever ALE frequencies are to be used.
The device on the left is the data/soundcard interface


The Battery

The following text describes how to build a battery pack. If you do not want to build this battery pack then you can buy one already built. For example you can look up "ZIPPY Flightmax 8400mAh 4S2P 30C LiFePo4 Pack" which currently sells for about $75. You will need to find a suitable charger for it.

I initially considered using 11 Accupower NiMH low-discharge "D" cells (10aH, 1.25v, 145g ea.)
This would give us 13.75v, 10aH at 3.5lb for about $110.

After more research I went with (8) 40160S LiFePO4 batteries (16AH/ea). This project really only needs 4 of these batteries however I opted to build two battery packs. 4 of these batteries in series gives you around 13 volts.

Update 11-21-2011: The 40160S 16AH battery is no longer being sold. The manufacturer has replaced it with the 40152S 15AH battery.

Paired with each battery pack is a circuit which protects from overcharge/overdischarge/overcurrent. It also keeps the batteries balanced while charging. After a long search for a suitable lightweight container I found the 4-battery pack fits perfectly into a "Huggies" baby wipe plastic box. I cut a small slot in the box for a short piece of velcro which holds the lid closed. The complete pack weighs about 5 lbs.

If you intend on taking your backpack radio on a commercial aircraft, keep in mind there are restrictions on high capacity lithium ion batteries. If you believe this will be a problem you can build a pack from 11 NiMH D cells or use a pre-made NiMH RC pack.


Notice the top door works great for the powerpole. File:W7ki_pack_battery2.jpg

Here is a view of the internals. The protection circuit board is on the top. File:W7ki_pack_battery3.jpg


The AC adapter/charger

I wanted enough beef for the radio to do 20W off the adapter. I ended up getting IBM PA-1121-0711 16V 7.5A Notebook Power Supply Adapter for about $14 off ebay. It is relatively small and weighs 0.4 lb. I run it through a bridge rectifier which reduces the voltage to 14.8V which is suitable for operating the radio and charging the battery pack. Of course running DC through a bridge rectifier only uses two of the four diodes however it was an inexpensive solution which is much easier than standalone diodes to mount to the cable/fuse.

I found that the battery pack can draw up to 8A during charging so I used a 10A fuse on the power supply. Yes, I know the power supply is only rated at 7.5A and putting a 10A fuse on it is not good practice. So far it hasn't been a problem. During charging the bridge rectifier can get quite hot so make sure it is on a non-flammable surface. The obvious solution to all this would be a series current limiting resistor which is something I'll look into when I get the time.

For now I am charging the battery pack with a small smart charger (Noco Genius G3500) which is set for a standard 12V battery at a 3.5A charge rate. It just so happens that its output voltage on this setting is just right for charging the LiFePO4 battery. The Noco Genius is a handy little charger as it is also good for charging and topping off car batteries, AGM batteries, 12V 7AH brick batteries, etc. and it will float the batteries without overcharging them. Another nice thing about this charger is its small enough to fit in the pack.


The Solar Panel

PowerFilm F15-1200 20W (10.5 x 6.5 x 0.6" 1 lb )
Nice compact and light panel but a little pricey at $10/watt. I would have gone with their 30W panel but it was even more overpriced.

Here is the solar panel File:W7ki_solar_panel.jpg

The Computer

EEEPC 1000h. Small battery-efficient netbook with 10" screen. Used it because I had it on hand. Any netbook would probably do ok so long as it has mic/headphone jacks. One bonus of this particular computer is you can feed it 12VDC direct.

Here is the computer File:W7ki_netbook.jpg

The Data Interface

Homemade. Nothing fancy, just some audio isolation transformers, a level converter, and a PTT transistor.
The data interface and the tuner are attached to the mobile mounting bracket with velcro. Note how the mobile bracket is angled such that the front of the tuner is slightly elevated. This was done to give some clearance to the radio speaker and also helps to direct the audio out of the pack.

The Antenna

I looked at a variety of compact antennas (Outbacker Joey, Outbacker Stealth Plus, ATX-W38 walkabout, ATX-DHP, and a handful of others). It was difficult to find anything that would collapse to under 18 inches (requirement for the pack I'm using). It was probably just as well since many "portable" antennas are helical which I personally despise.

My original intent was to buy a "Buddi" product and evaluate how it worked in a vertical configuration. The only issue was whether their 80 meter coil would fit in the pack. I emailed them multiple times asking the dimensions of the coil but unfortunately all of my emails were ignored. This probably speaks volumes as to how they handle issues after a sale so I thought it best not to do business with them until their customer communication improves.

Of all the pre-made antennas I found two that appear to be worthwhile.

One is the SuperAntenna MP1B SuperStick which is a good solution as it collapses to 12 inches and weighs under 2 pounds. When I first wrote this article their company had no products available which I believe was due to a transition in ownership. Their products are now available again and I plan on trying one out. I would buy the MP1B antenna, TM1 mount, and optionally MC60 coil for 60 meters and MC80 coil for 80 meters. A properly adjusted SuperAntenna requires no tuner however you need to use a correct length ground radial.
In June 2015 SuperAntenna released the MP1R SuperStick with a flexible whip.
As of 2017 SuperAntenna has the MP1DXMAX which appears to be a viable solution.

The other is the JPC-7 product line which can be found at http://www.108mhz.com/ham-antenna-c-59.html or on ebay. All three versions of the JPC-7 are lightweight and collapse to a small size.

If you choose not to purchase a pre-made antenna, the text past this point describes an antenna/coil that you can build.

I ended up using a military AT271-A/PRC antenna. It is a 7 section antenna with a 3/8-24 base that extends to 113.5 inches and collapses to 17 inches.
It has an optional 8 inch spring (AB-129/PR) which I am not currently using.
As an alternative I found an 8.5' collapsible aluminum pole made for measuring snowpacks and after some tinkering it worked like a charm. There is a threaded version which may work better (listed at the end of this article in the Parts Sources section).
Either of these antennas is very usable on HF when paired with a couple of 18" aluminum extender rods and a large tapped coil.


Obviously running a huge coil with a short antenna is about as worthless as a short helical so its important to remember to use as much whip or longwire as you can if you are less than 1/4 wave.

For a horizontal option I built a tapped voltage balun which attaches to a vertical extension arm and connects to two spools of wire. File:W7ki_horiz_setup.jpg
The wire spools can also be used as a counterpoise for vertical configurations.
The device at the bottom is a carbon fiber camera monopod which we use as a vertical extension arm.
The device at the top is a carpal tunnel wrist strap which is used for attaching the monopod extension arm to the pack aluminum extension arm.
The antenna wire is wound on Coleman camping clothesline spools.

Another HF antenna option is to build the St. Louis Vertical: http://www.amqrp.org/projects/stluisvert/STLV%20Project.html

For VHF/UHF I have a 17" dual-band antenna. For VHF only you can also put one of the 18" aluminum rods onto the 1" antenna mount.
6 meters can be done with the 17" antenna on top of both 18" rods.

The Pack

I looked at dozens of packs before settling on the Jansport Driver 8. Most other packs were either oversized and/or too heavy.

My reasoning for a 21x14x10" size limit is so you can carry this on a commercial airplane if you are traveling. You certainly wouldn't want to check this as luggage as it would probably get destroyed by handling or stolen.

Two main things I liked about the Driver 8 are the wheels and the telescoping arm. The telescoping arm is wonderful because it is very sturdy aluminum which allows you to securely attach an antenna to it. This is great for manpack operations if you want the antenna up while you are walking around with the pack on your back. It also works great for fixed operations as the pack itself can be used as an antenna base. The wheels not only give your back a break where smooth surfaces are available, they also give you the ability to easily lay down the pack when assembling a long antenna. Its like having a mini fold over tower.

The wheels are inline skate wheels and have a very low ground clearance. It will roll fine inside buildings or on a paved sidewalk. The wheels will not work on a trail. This is unfortunate as it is much easier to pull 35 lbs on wheels than to heft it on your back. One possible solution to this is to run a 1/2 inch rod (or thread stock?) along the bottom of the pack and install a pair of 10" x 1.75 lightweight plastic wheels. I would use Martin Wheel part number 110 wheels because they come with metal ball bearings.


Construction and Setup

A complete materials and sources list is at the end of this article.

Extension Rods and Antenna

To make the aluminum extension rods you need a 3 foot piece of aluminum rod. Cut the rod into 3 pieces, 2 of them will be 17 inches long and the third piece will be the remaining 2 inches.

Take a 21/64 inch drill bit and drill about 1.5 inches into both ends of the 17 inch rods. Be careful to drill straight. Once this is done tap threads into both ends with a 3/8-24 tap. Tapping threads into aluminum generates a tremendous amount of heat so remember to tap slowly and use an oil lubricant. Right after tapping these rods I bumped one of them with my arm and got a very nasty burn.

Once the tapping is done thread a 1.5" 3/8-24 RHT stainless stud into both ends of the rods. Then, for each rod, put a 3/8-24 jam nut over the stud on one end and put a 3/8-24 x 1-1/8 Hex Coupling Nut over the stud on the other end. When you are done it should look like the picture below.


This section deals with constructing the antenna if you chose not to buy an AT-271 antenna:

Now grab the remaining 2 inch piece of aluminum rod. Drill one end 1 inch deep with a size F (.2443 inch) bit then drill the other end 1 inch deep with the 21/64 inch drill bit you used for the other rods. Tap 5/16-18 threads into the size F end and 3/8-24 threads into the 21/64 end.

Take the aluminum snowpack pole, remove the lanyard string, push in the lower release spring button and shove it up the tube a couple inches, and tap the bottom for 5/16-18 threads. The two photos below show the start and finish of tapping the threads. I seriously do not recommend using vise-grips as shown in the photos. The antenna deforms very easily. It would be much better to lightly use a vise which can distribute the grip better with much less crush force. Again, BE VERY CAREFUL NOT TO CRUSH OR DEFORM THE TUBE. I darn near destroyed the prototype using vise-grips.



Next we take a 1.5 inch 5/16-18 stud and thread half of it into the antenna. This is generally difficult to do so I recommend tightening two 5/16-18 nuts against each other onto the stud and use the outer nut with a wrench. Once the stud is threaded into the antenna you can thread the 2 inch aluminum rod onto the stud, then thread a 3/8-24 stud into the other end of the rod. Put a 3/8-24 jam nut onto the exposed threads. What you have done here is built a 5/16-18 to 3/8-24 thread adapter. The photo below shows what the finished product should look like.


The next step is to modify the antenna to make it conductive. The anodized surfaces do not conduct electricity so you need to take some sandpaper and sand out the inside of the bottom of each rod (about 3/4 inch should do). Another issue is the tapered inserts which are crimped into the top of the rods. These don't conduct either so you need to lightly bond them with an arc weld. This should be done with a MIG or TIG welder. Remember to sand the surfaces first, including the entire tapered section. I cheesed mine by using two truck batteries, a pair of jumper cables, and some real thin aluminum wire. Some people refer to this as hillbilly arc welding. Please don't do this unless you know the risks, know what you are doing, and you are using appropriate eye protection. Verify the end to end continuity of the antenna with an ohmmeter when you are done. Here is what mine looked like when it was done.

The final step is to flatten out the pointed tip of the antenna rod. You can do this with a grinder or file.


The coil is made from a 7 3/4 inch piece of 4 inch diameter drainpipe with a drainpipe cap on each end. To make room for more coil turns we cut 1 3/8 inch off the end of the drainpipe cap. You need to cut two end caps.

Locate the center of each cap, tap the center with a center punch or nail, drill a 1/8" pilot hole, then drill in again with a 3/8" bit.

Now we take a piece of 1/4 inch schedule 80 pvc pipe and drill/tap it for 3/8-24 threads the same way you did the aluminum rods (except please don't use lubricating oil). Its important to use schedule 80 pipe as it has the correct inside diameter for tapping threads. The pipe should be about 7 1/2 inches long and later you might have to make some slight length adjustments for fit. Once your threads are tapped you can thread a 1.5 inch 3/8-24 stud into each end then put a 3/8" USS Flat Washer over the end (see photo below). Put one end into an end cap, put a 3/8" USS Flat Washer on the outside of the end cap, stack one 16-14AWG 3/8 ring terminal on top of the washer, and secure it with a 3/8-24 x 1-1/8 Hex Coupling Nut stacked on top of the ring terminal.


Put the other end cap on. On the outside stack a 3/8" USS Flat Washer, a 16-14AWG 3/8 ring terminal, and a 3/8-24 jam nut.
Remember to cover up any holes in the drainpipe with a square of duct tape.


To make the coil, glue 4 pieces of .065 Nylon Edge Trim as shown in the photo (credit to Phil AD5X for finding this edge trim). When cutting them to length, remember to offset each one to correctly accommodate a spirally-wound coil. Once this is done, drill a .065" diagonal hole from the edge of the cap through the top of each cap (see photo), thread the wire through the hole and wind the coil with .064" (14AWG) tin coated copper wire. Remember to keep tension on the coil or else it will wind loosely. The wire is stiff and doesn't come off the coil perfectly so there will be some manual coil alignment/straightening to do after the coil is wound. Once the coil is wound, put the ends thorough the 16-14AWG 3/8 ring terminals, then cut & solder. Be careful of heat damage to the plastic while soldering. Its usually best to loosen the end nuts prior to soldering as it will conduct less heat away from the ring terminals.

The coil tap is an EZ-Hook XM attached to a 16-14AWG 3/8 ring terminal with an 11 inch piece of 22-gauge 7-strand insulated hookup wire. Attach the ring terminal above the coil ring terminal as shown in the photo.

The EZ-Hook XM works great for 17AWG wire however its a little small for our 14AWG coil. The hook can be slightly adjusted with needlenose pliers to fit the 14AWG wire. The picture below shows the modified hook profile.

As built, the coil specs out like this: 7" length, 4.25" dia, 50 turns, 14ga .063 (spaced) = 129uH
Its a little overkill on the size & inductance but it gives a lot of flexibility with short antennas.


The balun is based on a design by WB6ZQZ. His design appears to be a bifilar current balun in series with a quadrifilar voltage balun. We are only interested in the quadrifilar transformer because we will be using an external ferrite choke on the feedline (which allows us to use the choke for antenna configurations that don't use the voltage balun). Here is a link to instructions on how to wind the quadrifilar transformer:

Use 16ga enameled wire and a F-125-K toroid. Once the transformer is wound you can mount it on a small piece of plastic with holes drilled for the wires. Attach the wires to each other as per his schematic diagram and PC board photos.

Mount the completed toroid into a 3x2x1 inch Jaycar UB5 clear jiffy box. Install an SO-239 connector into the bottom of the box. For terminals I used (4) 1/4"-20 x 3/4" bolts/nuts/wingnuts which are available at a home-improvement store. Label the terminals for Common, 50, 25, and 12 ohms. Attach a short piece of velcro to the back side which allows for mounting.


Antenna Mount & Wire Spools

The antenna mount uses 1/4-20 hardware. I recommend replacing two of the nuts with wingnuts. Cut an 11 foot piece of Belden 8219 RG58A/U and loop it twice through two Laird LFB187102 ferrites as shown in the photo below. The coax fits tightly and we do not want to stretch it while pulling it through the ferrites so use a non-petroleum lubricant (I used cooking spray). Once this is done you can put UG-175/U reducers on the cable and solder a PL259 connector on each end.

The antenna wire is spooled on a (2) Coleman 827E140T colthesline reels (thanks to Richard WA6KYR for finding these). Each Coleman reel comes with 21 feet of nylon cord. Pull all the cord out and cut off 13 feet so there is 8 feet remaining on the spool. Attach 59 1/2 feet of 22AWG insulated hookup wire to the end of the nylon cord. You can do this by stripping the end of the wire and pushing it through the middle of the nylon cord about 1/2 inch from the end, then secure the end of the nylon cord by lightly melting it with a lighter or soldering iron. Now you can reel in the wire. If it gets stuck you can open the reel with a 1/3 turn of the enclosure shell. Attach a 16-14AWG 3/8 ring terminal to the end of the wire.

If you are wondering why we use 59 1/2 feet it is because its the only length available that is reasonably close for loading at 75-80m and is not an even 1/2-wavelength multiple of any amateur band from 6m-40m (in fact we can go +/- 3 feet before bumping into one of these multiples. You should be able to roll this out to full length and tune any amateur band from 80m-6m. It also makes a good antenna to use with ALE and our RF-sensing tuner.


Each battery pack is made of (4) 40160S LiFePO4 cells (3.2V 16Ah) with a battery management circuit put into a Huggies wipe box. The battery management circuit sits on top of a plastic board which is an Akro-Mils 40150 (3.3 x 7.7 x 0.1 inch). Mount the batteries in the plastic holders, wire them in series with the bus bars, mount the battery management circuit, then wire it in. I recommend using a 30 amp fuse as pictured. Once this is done attach a 30A (12-14AWG) Powerpole connector with 12-gauge wire. The battery management circuit will charge the battery up to 14.2v before it automatically cuts off. The charger should be at least 14.6v.

Each 40160S cell is rated at 3.65V (Max Charge), 3.2V (Nominal), and 2.0V (Discharge cut off).
Max charge current is 5C (80A) and max discharge current is 10C (160A).
Cell life is rated at 2000 charge/discharge cycles under normal use.

Update 11-21-2011: The manufacturer has discontinued the 16ah 40160S battery and replaced it with the 15ah 40152S battery.

The complete battery pack weighs about 5 lbs.




Data Interface

The data interface consists of audio isolation transformers, an RS232 level converter, and a PTT transistor. The audio circuit is per the "KK7UQ Interface Model II" circuit although I chose not to use the potentiometers and solid state relay in the original design. The original design and documentation can be found here:


The RS232 level converter is per a circuit attributed to OE1RIB.

I decided not to go with the Yaseu CT62 cable because I wanted the ability to use the DTR line for PTT (which is much cleaner for automated CW than keying with serial commands). Don't get me wrong here, I prefer a key, however flexibility was one of the design goals. I modified the level converter circuit to take power from the radio rather than trying to rob it from DTR/CTS with diodes. There is also a DPDT toggle switch on the back of the data interface which is an "OFF" switch (cuts the power from the radio and cuts the PTT line). I looked at off-the-shelf interfaces and most of them were either too big or required power for the audio circuitry.
Use a USB-serial converter if your computer doesn't have a serial port. I recommend using converters with the FTDI chipset for best performance and OS compatibility (I used USBG-RS232-F12 from usbgear.com).

Here is the actual circuit I used to build the data interface:


Remember to leave clearance for the jacks and switches when laying out the components on the PC board.


Velcro attachment


Mounted to radio


To connect the interface box to the radio I used a short piece of cat5 network cable wired like this
CAT + Br-W

Data Out12 O-W
Data In W-Bl
Data PTT W-O
Data GND Bl-W

The mini-din connectors go in very tight so beware of non-functioning or partial connections when you do this. Once you get them seated properly they work great and stay in place. Make sure to notch the back of the connector sleeves so the cables can exit at 90 degrees.


In the above photo you will also notice a connector/adapter contraption covered with electrical tape. These UHF right-angle adapters were used because the radio rests on its back side in the pack and we don't want the weight of the radio sitting on a PL259 connector and pinching the coax. All UHF right-angle adapters are not created equal. Most of them are garbage and use a small internal spring to connect the center conductor. The correct part to use is Amphenol 083-1AP UG-646/U. The adapter connecting the radio to the tuner is two of the Amphenol right-angle adapters connected with a short piece of LMR-600 with the center conductor diameter ground down from 0.176" to 0.157". The length of the LMR600 and the mounting position of the tuner are critical because you don't want to obstruct the ports on the rear of the radio. As you can see in the photo below, this arrangement makes the back of the radio very compact which helps it fit in the pack.


Power Wiring

On the power supply you can add a third powerpole connector which is jumped to ground. When the third connector is also done on the radio side (connected to the radio brown wire) it forces the radio to 20W when plugged into the supply. This is good because our power supply is only rated for 7.5 amps.

The power cable is 24 inches of 12-gauge red/black zipcord with a third wire for sensing low-power mode. Additionally it has a 16 inch length of zipcord for the tuner with a 2.5x5.5mm right-angle connector. As with the OEM cable, the 12-gauge cable splits off into two 14-gauge cables at the connector. You will notice that there are no fuses on this cable. I didn't bother because all my power sources for the pack are fused. In hindsight it would be prudent to put 30A fuses on both the positive and negative wires.


Third Powerpole connector for low power sense.


Connector end detail



The monopod is used to elevate the feedpoint of the dipole or a short vertical antenna. It is carbon fiber, weighs only 19oz, and extends to 68".


The monopod needs to be shortened to fit into the pack. Going around the perimeter of the small end rod, cut off the bottom half of the top rubber cap. This will allow the rod to collapse about an additional 1/2 inch.


The bottom cap can be removed by pushing in the two roll pins with a small center punch. Then, with the rod fully collapsed, you will see there is about 13/16 inch you can saw off the big end without hitting the smaller rods that collapse inside of it. The photo below shows it after the cut.


Radio setup

Here is how I set mine up

Tune radio to 7.000mhz

Push and hold FUNC key for one second.

Rotate Select knob to "Menu 1" (Ext Menu). Set it to on.

Rotate Select knob to "Menu 19" (CAT Rate). Set it to 9600.

Rotate Select knob to "Menu 29" (CW Sidetone). Set it to 5.

Rotate Select knob to "Menu 38" (Dig Mode). Set it to PSK31-U.

Rotate Select knob to "Menu 59" (Mic Sel). Set it to RMT if you are using the MH-59A8J mic.

Rotate Select knob to "Menu 75" (RF power). Using the large tuning dial, set it to 45.

Rotate Select knob to "Menu 86" (TX IF Filter). Using the large tuning dial, set it to 2.3

Rotate Select knob to "Menu 1" (Ext Menu). Set it to off.

Press and hold the FUNC key to exit.

Tune radio to 50.000mhz

Push and hold FUNC key for one second.

Rotate Select knob to "Menu 75" (RF power). Using the large tuning dial, set it to 45.

Press and hold the FUNC key to exit.

Tune radio to 144.000mhz

Push and hold FUNC key for one second.

Rotate Select knob to "Menu 75" (RF power). Using the large tuning dial, set it to 20.

Press and hold the FUNC key to exit.

Tune radio to 446.000mhz

Push and hold FUNC key for one second.

Rotate Select knob to "Menu 75" (RF power). Using the large tuning dial, set it to 10.

Rotate Select knob to "Menu 1" (Ext Menu). Set it to off.

Press and hold the FUNC key to exit.

Enable 2.3kc filter for TX:

Push FUNC, rotate select to N, press 2.3 (above B key)


The most basic setup is pulling the aluminum pack handle up one notch and attaching the mount/antenna. This can be used for a quick base setup or walking around with the pack on your back. The photo below shows the mount and 2m/70cm whip installed. If you want a somewhat useful counterpoise for 6m/2m/70cm without attaching the counterpoise wire, simply invert the feedline such that the chokes are by the radio instead of by the antenna. This way you can use the coax itself for a counterpoise. Its certainly not the best way to do it but it will work.


Each aluminum rod is 18" and you can use one of them by itself for a 2m quarter-wave.


If you use both rods with the 2m/70cm whip on top you will have a 6m quarter-wave.


You can use the monopod to elevate the a 6m/2m/70cm antenna. We use the carpal tunnel wrist strap to attach the monopod to the packs aluminum handle. The next photo looks like the leaning tower of Pisa because my first prototype was done with a medium-sized wrist strap. I have since moved to a small-sized strap which makes it stand much straighter. The monopod is good for 6m/2m/70cm verticals and for holding the feedpoint of a dipole. Do not use the monopod with the 8-foot antenna rod and/or the large loading coil as it gets too top heavy to remain stable. The following photo shows the ground radials installed and the choke ferrite near the antenna feedpoint. For a simpler setup you can skip the ground radials and invert the feedline (so the choke ferrites are near the radio) which will make the feedline act as a counterpoise. Yes I know this was said earlier in the article but its worth repeating.


Detail of antenna mount attached to the monopod pole


The collapsible antenna by itself will work as a quarter-wave on 10m (pictured below) and should also tune up ok on 12m. It will work as a quarter-wave on 15m if you add the two aluminum extension rods.


Attaching the coil (tapped on the lowest turn) to the antenna base with the two aluminum rods above it will tune down to 80m. This configuration will have near zero efficiency however it will allow short-range communication on 75/80m while walking around with the pack on your back.


The best vertical configuration for 80m thru 17m is attaching the two rods to the base, putting the coil on top of the rods, then putting the collapsible aluminum antenna rod on top. It is best to tilt the pack over on its wheels and assemble the antenna on the ground.



Once its assembled, tilt it up by lifting the aluminum arm on the pack. The weight of the batteries do a good job of keeping the antenna in place.


If you want to try 160 meters you can remove the 8 foot whip and connect one of the 59-foot wire spools to the top of the coil.

For a dipole configuration you can strap the balun to the top of the monopod and connect our spools of wire to it. Dipoles work best when they are at least 1/4 wave above the ground. Our feedpoint impedance will typically be much less than 50 ohms because in most cases we will be less than 1/4 wave off the ground. This will be especially noticeable on 40m/80m. Attach one wire to the "C" (common) balun terminal and attach the other wire to either the 12, 25, or 50 ohm terminal depending on which one works best. The wire spools use 3/8 ring terminals so we can optionally connect them directly to the vertical antenna mount if you want to feed a dipole directly without the balun.

One other important thing to note about dipoles is its best to keep the ends up off the ground. There is 8 feet of nylon rope at the end of the spools which can help in getting your wire somewhere it can be secured. In my pack I also keep short plastic tent stakes and short bungee cords which can help in some situations.


There are a few other odds & ends I keep in the pack. The PL-259 center to ring terminal adapter is for using the voltage balun with the vertical antenna. The Powerpole "Y" cable is for running the AC adapter or solar charger while using the radio. The short 3/8-24 bolt is for attaching a dipole wire directly to the antenna mount or to the top of the coil. There are also two 8-foot stereo cables for the data adapter and a 10-foot serial cable (not pictured). (I chose 8-10' cables to keep the computer RF a little ways away from the radio/antenna). At the bottom is the usb/serial adapter and on the bottom right are short velcro cable ties for attaching the feedline to the monopole and/or aluminum pack handle.


Here is how it all fits into the pack


The complete pack with both batteries and the computer weighs 35 lbs.

The weight can be substantially reduced by removing the spare battery, AC adapter, computer (if you don't need it), and any antenna parts you don't plan on using.

In case you are wondering where the CW key/paddles are, I'm still working on finding a solution that works well with this portable setup.
Two that have been recommended are the Mini Paddle from Milestone Technologies and the Traveler Light from Begali.

Parts & Prices

$799 FT857D w/YSK857
$95 TCXO-9
$82 MH-59A8J DTMF mic (also needed for direct freq entry)

$120 W4RT2.3khz ssb filter
$169 Z-11pro2

$14 IBM PA-1121-0711 16V 7.5A Notebook Power Supply Adapter (ebay)
$2 bridge rectifier KBPC5010 (ebay)

old: $144 (8) 16ah 40160s lifepo4 $24/ea  (bmsbattery.com or manzanitamicro.com)
new: $144 (8) 15ah 40152s lifepo4 $24/ea  (evassemble.com)
$3 (8) 40152S or 40160S battery holders 0.40/ea
$4 (8) 40152S or 40160S bus bar connectors 0.50/ea
$80 battery shipping

Update 11-21-2011: The manufacturer has discontinued the 16ah 40160S battery and replaced it with the 15ah 40152S battery.

$97 (2) 30A Battery Management PCB http://www.batteryspace.com/pcbprotectioncircuitmodulefor4cells128vlifepo4batterypackat30alimited.aspx

$11 USB to serial converter http://www.usbgear.com/computer_cable_details.cfm?sku=USBG-RS232-F12&cats=199&catid=482%2C199%2C601%2C461

$8 3/8X24 Thread Mirror Mount:  Wilson 901104
$5 (20') Belden 8219 (RG58A/U) 
$3  (4) Amphenol 83-185-RFX (UG-175 reducer)
$20  (4) Amphenol 83-822 (PL259)
$10 shipping (theantennafarm.com)

$79  Jansport Driver 8 TN89-008 UPC 757969203361  Wheeled Backpack (buy.com)

$6  dual-band (2/440) whip with 3/8x24 mount (hamstick EDBW-1, Opek DB-1, or Workman DB-1) 
$4  (2)  WORKKW2000A or CONXPARTSA   (this is the power cord and connector pins)
$3  (6 feet) Red & Black DC wire 12 GA
$9  shipping  (k1cra.com)

$11 (3') LMR-600  (showmecables.com)

$1  (4) 1/4"-20 nuts (7/16" head)
$1  (4) 1/4"-20 x 3/4" bolts
$2  (8) 1/4"-20 wingnuts
$9  (10') 4" drainpipe   (we need one 7 3/4" piece)
$4  (2) 4" drainpipe cap (home depot)

$20  (5) littelfuse FHA30 12AWG inline fuse holder
$3  (1) 5-pack of ATO 7.5 fuse (drillspot.com)

$3  4' 14 gauge cable (for short part of radio power connector)  (.62/ft)
$1  4' 18 gauge cable (for battery sense +/- to pcb, low power wire on power cable)  (.31/ft)
$6 (1) 1/4" (22-18) Ring Terminal 50pcs
$4 (1) 1/4" (16-14) Ring Terminal 50pcs
$6 (1) 1/4" (12-10) Ring Terminal 50pcs
$10 shipping (parts-express.com)

(1) DB9F     mouser 156-1309 0.80
(4) BC546A    mouser 512-BC546A   0.10
(2) 5.6k 1/4w  mouser 588-OD562JE  carbon comp 5%  0.42/ea
(3) 10k 1/4w  mouser 588-OD103JE   carbon comp 5%  0.42/ea
(1) 3.5mm 3-pin plug (cw)  (2 wires used)  mouser 568-NYS231BG  1.69   (for cw jack)
(1) 8-pin mini-din (cat)   (4 wires used)  mouser 171-2608 1.49
(1) 6-pin mini-din (data)  (4 wires used)  mouser 171-2606 1.36
(2) 600ohm 1:1 transformer  mouser 42TL016-RC  1.66
(2) 51 ohm 1/4w   mouser 588-OD510JE  0.42
(1) 1uf cap   mouser 5989-100V1.0-F    0.71
(1) .0047uf cap  mouser 140-50P5-472K-RC   50v ceramic disc  0.12
(1) 100 ohm 1/4w  mouser 588-OD101JE 0.42   carbon comp 5%
(1) 1k 1/4w   mouser 588-OD102JE 0.42
(1) board  mouser 854-PR1593K $4.10 2.6 x 2.6
(1) box    mouser 546-1593KBK $2.88 (box is 2.6 x 2.6 x 1.1)
(2) 2.2k resistor 1/2w  carbon comp 5%   mouser 588-OF222JE   (1/4w mouser 588-OD222JE  0.42 not avail)
(4) PL259 right angle Amphenol 083-1AP UG-646/U   Mouser  523-83-1AP  $14.70/ea
(1) 2.5x5.5mm right angle plug (24AWG) power plug for tuner   mouser 171-3216-EX  $1.04/ea
(2) ferrites  - mouser 875-LFB187102-000  3.03/ea  3/4" OD  .400" ID  1.125" long (3 turns RG58 = 1000 ohm impedance @ 1-5mhz)
(2) mouser 526-WH22-00-100   100' 22awg copper 7-strand hookup wire black nteinc.com $19  (use p/n 03-100 for orange)  insulation OD 0.060"
(2) 3.5mm stereo jacks   502-35RAPC3BV4  2.73
$112 total
$12 shipping (mouser.com)

$8 (1) 14-pack 3/8 ring terminal 16-14AWG  (JT&T 2011H - amazon.com)
$18 (2) 8ft 3.5mm stereo cables (mediabridge - amazon.com)
$3  21/64 (.3281") drill bit for 3/8-24 threads (amazon.com)
$28  3' Aluminum 6061-T6 Seamless Round Tubing, WW-T 700/6, 1/2" OD, 1/4" ID, 1/8" Wall, 36" Length (amazon.com)
$65 Opteka CFM300 68" 5 Section 8x Carbon Fiber Monopod (amazon.com)
$209  (1) PowerFilm F15-1200 20W solar panel 10.5 x 6.5 x 0.6  1 lb  (amazon.com)

$11 (4) EZ-Hook XM   (digi-key 461-1004-ND)

$2 Akro-Mils plastic dividers  (Akro-Mils 40150 wasserstrom.com)

$1 (8) 3/8-24 Jam Nuts 18-8 Stainless Steel
$1 (2) 3/8-24 Hex Nut 18-8 Stainless Steel
$10 (5) 3/8-24 x 1-1/8 Hex Coupling Nut 18-8 Stainless Steel
$1 (10) 3/8" USS Flat Washer 316 Stainless Steel
$7 shipping (fastener-warehouse.com)

$7  (5') 1/4" schedule 80 PVC pipe (usplastic.com)

$14 (2) coleman 827E140T colthesline reel (coleman.com)

$58 AT-271A/PRC antenna (ebay)  OR  $58 Voile Tourlight Avalanche Probe (8 foot) (voile-usa.com)
    Alternatively there are threaded snow probes at: http://us-warehouse.genuineguidegear.com/collections/probes/products/solid-probes

$2  (2) 6" tent stakes (rei.com)
$2  (1) 4-pack of 10" bungee cords (rei.com)
$8  tax/shipping (rei.com)

$12  (1)  F-125-K Toroid Core  1.25" 250-300 permeability low loss ferrite 1-30 mhz    (theaudioguru.com)

$11 (1)  1/4 lb Wire, 16ga (0.05") enameled (we need 4 feet for toroid) (allspectrum.com or jameco.com)

$20 (1) 79-87283 DonJoy COMFORTFORM WRIST support-Small right  (expressorthopedics.com - warning, it takes them a month to ship it)

$8 Cables To Go 52030 - 6ft DB9 M/F All Lines Extension Cable Black    (nextwarehouse.com)

$12 (1) 85085K8 25-pack nylon edge trim  .065 gap width    3/16 opening, 15/64 height, 12 3/4 long
$23 (1) 8871K71 80' (1 lb) spool .064" (14ga) tin coated copper wire (spool says Arcor 14AWG)
$2 (1) 91187A202 1.5" 5/16-18 RHT stainless stud  (or you can order a 10-pack for $4.55 with part number 95412A587)
$10 (2) 95412A659 5-pack of 1.5" 3/8-24 RHT stainless stud
$9  tax/shipping  (mcmaster.com)

$2518 approximate cost

$?  (1) stickyback velcro (attach tuner to radio mount)

$?  (1) velcro wire ties (attach coax to antenna mast)

$?  (1) 3/8-24 tap
$?  (1) 5/16-18 tap
$?  (1) Jaycar UB5 clear jiffy box (for balun) 3x2x1"

$?  (4) 30A (12-14AWG) red/black powerpole connector (1 for radio, 2 for batteries, 1 for AC/DC power supply)

More Information

Here are some websites with great ideas for building backpack radios:

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