SOTA FT-857 Manpack

As you may have read in my introduction I really enjoy Summits on the Air activations. There are many different operating styles among the operators. Some enjoy QRP CW, others VHF FM. I am one of the people who like the “military style” HF operation. I usually use about 20W of output power running SSB into low inverted V antenna for 40m. Antenna works on NVIS principle and is therefore great for QSOs with stations 0-1000km far away.

FT-857 Manpack on summit

FT-857 Manpack on summit

Motivation

Biggest problem I ran into was how to safely carry all the equipment up on the summit and how to set up a station as fast as possible. I always take my Yaesu FT-857D and 7Ah SLAB battery. Both are heavy and both were bouncing and colliding in my backpack. Then up on the hill I had to find a safe, dry place, get the radio out, get the battery out, connect the stuff and this took me really long time. Again I was trying to get some ideas in military gear. A manpack radio can do the job. These radios are great, rugged, waterproof but also very pricey and repairs can get complicated unless you have good source of parts. So I decided to make my own manpack from parts I already had and I was able to obtain.

How to

For this recipe you will need:

  • Yaesu FT-857D radio
  • 7Ah SLAB battery
  • piece of hard metal sheet
  • two PL female connectors
  • one N male connector
  • one PL male connector
  • piece of coax cable (good is Belden H-155)
  • original Yaesu monting bracket (optional)
FT-857 SOTA Manpack

FT-857 SOTA Manpack

As you can see on the picture, main idea comes from fact that width of the SLAB battery is nearly identical to the width of FT-857. So you have to take piece of metal and carefully bend it to form letter U. In my case I bought 2 pieces of some bracket for 10Kč in a clearance sale. I cut the two pieces to proper length and from remainings I made the lower part under the battery. I used rivets to hold the three pieces together. You can use whatever material you can get – this is just to demonstrate the basic idea.

FT-857 SOTA Manpack

FT-857 SOTA Manpack

Then I drilled holes on sides to fit the holes on the original Yaesu bracket and on the radio. You don’t have to use the original bracket, but I put a wide Velcro on it and I can use it to hold my LDG Z-100 Autotuner. I don’t use it very often as I use resonant antenna for SOTA, but I wish I had this when I was operating from a beach during 9A holiday/expedition.

Note: This brings me to one more great thing about this manpack. Especially when you are using tuner, amount of cables required is unbearable. With this solution you can plug everything at home hide the cables and later outside you can just press the power button and you are QRV.

Next I prepared female connectors on the front panel. I used the type with nut, not the classic SO-239. I put the VHF/UHF connector on the right side because I use the rotary encoder on left on 2m. HF connector then gone to the left because I use the tuning knob on HF. This setup allows you to comfortably plug antenna and you can even plug in some mobile antennas directly to the socket without any coax. This is especially useful on 2m. For cable I strongly recommend using Belden H-155. This cable has much thicker braid and is overall much more heavy duty then RG-58. The cable can get really stressed as it is on outside of the bracket.

FT-857 SOTA Manpack

FT-857 SOTA Manpack

Finally to secure the battery in place, I bent the metal around it. I bent only the front side as the back side was already bent on all metal pieces I bought. I didn’t have to use any extra straps to hold the battery because it fitted very tight in the bracket. I even charge it in the bracket, but I recommend that you unplug the battery from radio when storing manpack at home. FT-857 obviously draws some small current when turned off and it will drain your battery.

Operation

Manpack was finished so I could give it a test outside. It nicely fitted to my backpack. It feels like if you have a backpack with a frame. On picture you can see me activating Meluzína OK/KA-003 exceptionaly on 2m SSB. That day I worked YU1IO 900km away with only 20W and 3-element yagi in hand.

FT-857 Manpack on summit

FT-857 Manpack on summit

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