Sunday, July 23, 2017

Go-boxes for QRP rigs

A few months ago I posted my thoughts regarding what I believe may be the next step in outdoor portable QRP rigs - protection from the elements. The technical performance of modern rigs like the KX-series from Elecraft and the numerous designs from KD1JV are amazing - but their degree of environmental protection lags somewhat behind.

Several hams have taken it upon themselves to create clever solutions and one can't help but admire the craftsmanship in these homebrew designs. Free programs like Front Panel Designer and DraftSight make it possible for the dedicated ham to make a custom template/faceplate for any rig and case combo and have it delivered right to your door. 3D fasteners (like those used in Elecraft's K3) then secure the faceplate to a Pelican or B&W case.



Check out the following designs:
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From Tom OE2ATN, KX2 + Pelican case -  (click here for more)

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From Martin DK3IT (KD1JV's MTR-3B + Pelican case):
Dear all,

For quite a while, I have been trying to work on a light and quick-to-setup station based in my MTR3B, mainly for SOTA, with following goals in mind:

1. Lightweight and compact (that is clear).

2. Rapid setup: In the beginning, I tried packing an MTR with all kind of stuff in bags, which was compact and lightweight. But it takes a lot of time to unwind and connect everything; parts can be lost, and it is a pain to use many distinct parts e.g. in 50 cm of fresh snow. Also, I often have very limited time on the summit, so loosing 10 minutes to unpack my rig is problematic.

3. Sturdy and watertight: I want to be able to squeeze my gear into a full backpack with crampons, carabiners, etc. in a hurry without fearing to break the key or other parts. The MTRs slide switches are e.g. easy to damage. Also, at least when stowed away, rain and some snow should not harm.
Inspired by the GoBox concept by Tom, OE2ATN, for the KX2.

I designed a similar station based on the MTR3B, with the following components:


  • Mountain Topper MTR 3B, gives 40-30-20m, which is all I need, removed from its metal case
  • Pelican 1040 case
  • 4.8V 4 x AA Nimh battery pack; fully sufficient capacity for several hours, much less risk than Li-based batteries
  • Two step-up converters that generate 6 and 12 V DC from the battery, 12V for full 5W and 6V for 1 W for tuning and QRPP
  • Simply battery voltage monitor with two LEDs, a zener diode and a transistor - green LED shows sufficient voltage to not overload the step-up-converters (their input current increases as the input voltage drops), red LED shows undervoltage so that you can stop before the Nimh batteries get damaged. I decided against an automatic turn-off circuit, because I want to be in control to finish a QSO
  • SWR meter (rather: indicator, hi) and power indicator with LEDs, based on the design by DF3OS
  • Volume control (simple 1k micro potentiometer) to adjust headset and speaker volume
  • LM386 amplifier and tiny control monitor, so that I can be away a few feet from the radio, e.g. during CQ loops
  • Palm Pico Single key, mounted with magnets on the bottom that allow easy stow away and various angles for operating.

All components are mounted on a front panel designed as a 3D print part. I will later replace that by a laser-cut aluminum one but wanted to test the concept first.

The front panel includes a few metal washers so that a Palm Pico Single key can be mounted in various angles via its magnets and can be retracted during transport.

The charging of the NimH batteries is done by an externalplug-in power supply that supports 1 A current and includes all circuitry for intelligent charging.

For longer activations, external batteries can be plugged in via the same DC connector.

I am very, very happy with this setup. I can be QRV within 15 seconds + antenna set-up; you cannot loose any part, and the complete station without antenna is just 559 grams. The batteries allow for many hours of operation with full 5W.

The next project is a similar station on the basis of the MTR5B, mainly because of the VFO display and the option for a rotary encoder (and 17m).

I will be happy to share the 3D files if anyone is interested.

73 de Martin, DK3IT:



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Scott AK5SD (KX3 + B&W case):


Read more about Scott's design on Thomas K4SWL's blog. Many more photos, parts list and downloadable file for Front Panle Designer are there as well.
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Hanz W1JSB has been creating clever, practical and eye-appealing designs for years using a variety of QRP radios. His site is here. I particularly like his use of touch keyers.


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And a 100-watt go-box based on a KX3:


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2 comments:

  1. Good evening John, they are very professional looking and the links you provided for the faceplate manufacturing I never knew these places existed for the home builders.
    73,
    Mike

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    Replies
    1. I've never designed a faceplate either and most of my homebrew rigs show it - they operate well but look like crap due to the "learn to use a nibbler as you go" technique I implemented. If Front Panel Designer and similar outfits had been around back then the dreaded cosmetic aspect of housing a rig might have also been the funnest part.

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