A Happy Marriage of Ideas: The SST and TFR
Special to The ARS Sojourner
I love my SST, and have been very successful with it. It has a wonderful receiver and a razor-sharp filter. When I'm in the field I put the SST on my knee and hold a Whiterook keyer on top of the rig while I send.
It has been difficult to use the SST inside a little tent or while in a sleeping bag because the keyer and battery box and their dangling cables get in the way. Sometimes I have found it hard to find a quick QSO within the narrow eight KHz range of the SST VXO while on the trail.
I wrote down a list of ideas for a TFR and decided to assemble a radio to try them out. I made a list of the desirable features:
1. The radio should have built-in keyer and batteries so there are fewer dangling cords and boxes to deal with. 2. The radio should have broad enough frequency coverage to allow me to find a QSO when the bands are quiet. 3. The radio should be easy to use from a sitting, standing or reclining position. 4. The radio should weigh less than a pound, yet be tough, functional and reliable.
I struggled to decide which band to use, and finally settled on 40 meters. Twenty would also have been a good choice. I don't possess skills to design a circuit from scratch, so I decided to purchase a NN1G SW40 kit.
I've used Dave Benson rigs in the past, and have great regard for them. I also spent $5 on a TiCK keyer chip and put it on a tiny piece of perfboard inside the rig.
My first concern was for a suitable enclosure. I made a number of cardboard mockups and tried using them in bed, standing, and sitting on the ground.
After these experiments, I decided that a narrow, handheld case with paddles above the tuning dial would suit me best. The keyer paddles were placed at a comfortable angle so I can hold the rig with my left hand and use my right hand to tune, write and send.
The gain control and phone outlet faces me, the antenna jack is pointed away from me. All the electronics fit in the top of the case so the bottom can be removed without dealing with dangling wires. The upper portion of the box is half of a 3X5 inch Radio Shack aluminum project enclosure.
The bottom is made of clear ABS plastic. I painted the top blue and decorated it with automotive pin-striping tape. The bottom was going to be painted, but my kids thought it was “neat” to see the electronics inside, so it remains clear.
I considered using a 10-turn pot to tune the rig, but after putting one in a NorCal 40A with a KC1, decided I don't like the arrangement. The SW40 kit cost less than $50. It was fun to assemble, works very well, and puts out 1.5 to 2 watts.
It tunes from 7016 to 7052 KHz. I fitted a nut into the plastic back of the rig so it can be firmly attached to a small clipboard when I need a writing surface for contest logs.
The keyer paddles are homemade. Silver plated copper contacts were soldered to lugs to make the switching circuit. The TiCK chip is powered by a small internal lithium cell.
I leave the battery in the circuit all the time so I don't have to reset the keyer speed each time rig is powered up. The paddles are disconnected from the circuit when the rig is off.
I've been very happy with the keyer. The placement of the paddles at an angle above the tuning knob has worked out very well.
The rig is powered by an internal nicad battery pack. After fooling with various batteries for many months I happened on a bunch of discounted cordless telephone batteries that had been donated to the thrift shop by a defunct electronics store. The package consists of four 3.6 volt batteries in series. They weigh 5 ounces total, are rated 300 MaH and cost $8 total.
These provide just over 3 hours of frantic operating time, and much more if I am just listening and ragchewing. I charge the batteries with a “wall wart” or a small solar panel. A lightweight 10X12 inch solar panel with a voltage regulator runs the rig without batteries on a moderately sunny day.
I thought an internal speaker would allow me to listen while I am moving about in camp, but I abandoned the idea after looking at current consumption, space and weight data.
I have a tiny external speaker with an audio amplifier to use if needed. A pair of high-quality earbuds are more than adequate for operating.
My little rig is housed in a tupperware container, and waits in my backpack to accompany me to the bush. In its usual state with batteries and earbuds but no clipboard, it weighs in at 17.5 ounces - just a little over a pound.
It is 3X5X2 inches, a little “fatter” than I wanted it, but the depth was necessary to house the rather husky rechargeable battery pack. The rig is comfortable to use, hears well, and has netted a lot of QSOs from my home QTH.
It has been to the field twice so far, and it will see a lot of action during the spring and summer hiking seasons.
The picture shows me and my 12-year-old daughter, Mary, during a hike to a remote ancient Indian site in Southeastern Utah, January, 1999.
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Bob Armstrong, N7XJ, an avid QRP operator, builder and outdoorsman, lives in Manti, UT.