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Revision as of 23:34, 21 June 2011

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:

FM/SSB/CW/packet

Radio receive current:

preferably less than 700mA

Tuner:

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

Battery:

sufficient to handle a weekend without recharging

Power:

Battery, AC, or solar

Antenna:

Vertical or dipole with optional voltage balun

PC:

Small netbook capable of digital modes

Size:

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

All items:

Weight as minimal as possible !

The Radio

Here is a quick rundown of the radios I considered:

Military radios (PRC-104, PRC-132, PRC-138, PRC-320, PRC-1099, PRC-2000, 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.

Commercial radio VX-1210 ($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.

Commercial radio Mobat Micom 3 Pathfinder (25W)

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.

FT-817ND ($600, 2.6lb, 8-16v, rx: 300-500mA, tx: 2A/5W):

Tempting, and would pair nicely with LDG Z-817 tuner.

Only problem is I want 20W+. This could be accomplished with a Tokyo High Power HL-45B

amp ($900, 3.4 lbs, 8.5A/45W, 160-6m) however I think the price is a little high.

Regardless this is a viable combination and has the benefit of low RX current.

IC703+ (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).

IC706MK2G ($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.

IC7000 ($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.

FT-897D ($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.

FT-857D ($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:

$200 LDG YT-100 (latching relays) for 857/897 100w = 1.5lbs 4-800 ohm 7 x 7 x 2

$200 LDG AT-897+(latching relays) for 857/897 100w = 2.0lbs 6-800 ohm 11.5 x 3.25 x 1.5

$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 battery

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.

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.



Notice the top door works great for the powerpole.

Here is a view of the internals. The protection circuit board is on the top.

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.





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 and the computer File:W7ki solar panel and netbook.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.



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.


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. I could not 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.

Fortunately I found an 8.5' collapsible aluminum pole made for measuring snowpacks and after some tinkering it worked like a charm. Paired with a couple of 18" aluminum extender rods and a large tapped coil it turned out to be a usable antenna. 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 connects to two spools of wire. These wire spools can also be used as a counterpoise for vertical configurations.

For VHF/UHF I have a 17" dual-band antenna or another option for VHF only is putting 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 you 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.