Homebrew Vintage Gear

My resurgence of interest in CW, followed by the case and feeding of Straight Keys, soon led to other serious perversions. If you enjoy using straight keys, or even wish to drop back, however briefly, into a simpler time, the event of the years is the ARRL's Straight Key Night (SKN), which starts every New Year's Eve at 00:00 UCT (7PM EST) and runs for 24 hours. While standard keys predominate, you will also hear bugs, sideswipers, cooties, and a host of manual keying systems that defy description. To make things more interesting, the keys are often plugged into vintage gear (anything prior to 1970, also affectionately known as boat anchors), with the result that bands like 40 meters sound like a time-machine to decades past - the good, bad, and the ugly of hand-sent CW, drifting signals, and more chirps than the bird section of a pet store. The fact is, most of the fists are first-rate and the signals from finely-restored gear produce beautiful notes. The ether is also filled with courtesy and commeraderie, the bands as we fondly remember them from our youth! Where else can you work a guy who was a Navy radioman or served with the Merchant Marine during WWII, or listen to a replica suitcase spy radio of the same era?

With a number of SKN forays under my belt, I decided that by 20109 (the 52th anniversary year of my Novice license), I wanted a piece of vintage gear for the evening! My first thought was to acquire something from my Novice past. My very first transmitter was a single 6V6 rig, assembled on wooden slats, from the 1955 ARRL publication, How to Become a Radio Amateur:

My own disappeared decades ago, but I "borrowed" this photo from the Pastime Projects Web Site, where you can still purchase a kit for this project! I had a handful of contacts with this rig and remember endless hours of calling to no avail. The problem was, I was operating QRP before it became sporting, my receiver was awful, and I didn't know what I was doing. The rig was a one-tube "power oscillator" (see later comments) and, as a result of its open construction, it almost electrocuted me twice: In both cases it slid off a shelf and onto my operating table where, naturally, my hands were busy logging, writing, and keying. If you build one of these, add side slats to the "chassis" to make sure that no accident can cause anyone to come into contact with the "innards" while the rig is operating!

My "ideal" transmitter would keep me in the QRP operating envelope yet still have the look and feel of the decade between the late 50's and late 60's. One of the significant benefits of ARRL membership is that you have access to the Periodicals Archive and Search that lets you browse and download the contents of QST from 1915 onwards. My personal answer to an optimun vintage project was in the form of an article by Don Mix (W1TS) in a 1968 issues of QST - Mix, D. 1963. A simple transmitter for the beginner. QST (October):22-28:

A close took at the sub-title and you will see "12 Watts on 40 or 80". You have to remember in cruising through these old articles that transmitter power "back in the day" was measured in terms of DC input as opposed to today's standard of DC output. Don's little transmitter can be expected to crank out 4-6 watts, depending primarily on the plate voltage on the 5763 final amplifier. What puts this rig head and shoulders among many of the "beginner" transmitters that appeared between 1955 and 1970 is the fact that it is not a single-tube power-oscillator. Such rigs were popular because of their relative simplicity (hence lower cost), but had high levels of crystal current (that can heat up vintage crystals and even destroy modern plated crystals) and they often had horrible chirp (freqency-shift when keying). The W1TS transmitter is a respectable MOPA design (Master Oscillator, Power Amplifier) that avoids all the problems of putting an oscillator on the air with the trivial added cost of a seperate tube to provide the oscillator function. This is one of the best written construction articles that I can remember and I would love to provide a link to download the PDF, but the ARRL holds the copyright and rightfully should control the download rights to the article.

This little transmitter design popped up once more in QST   in an article  by Steve Johnston (WD8DAS) - Johnston, S., 2003. The two-tube tuna tin transmitter (T5). QST (January) 39-42:

Although Steve (WD8DAS) does not reference Don's 1968 article, it is the same circuit (aside from the innovative packaging to create a tube version of the famous Tuna Tin 2 QRP rig), with the exception of the addition of a simple key-click filter, a 47 ohm resistor to limit the crystal current (both good ideas) and a trivial change in the final grid-leak resistor. One very nice aspect of this article is a pretty up-to-date set of references for getting the needed parts. This article can also be downloaded from the ARRL web-site (www.arrl.org).

My own version of the transmitter ended up looking a bit different than either of its ancestors:

Those of you who are as grey-haired/bald as I am will see a family resemblance between this rig and the venerable Ameco AC-1:

I never had one of these rigs, but I always liked the simple look. It was another simple power oscillator (the second tube is a rectifier, not an independent oscillator) and I was not the least bit interested in operating one. What I did do was build my W1TS replica so that it looked a bit like the AC-1.

I used a plug in coil system for the "look" and have no plans to use coils for other bands. My single coil covers both 40 and 30 meters (the latter a band that did not exist when W1TS designed his rig). My plug-in coil forms were obtained from National RF which sells both the forms (very nice) and matching octal sockets.

The tune and load capacitors are panel-mount receiver variables that are widely available (see the vendor list in the WD8DAS article). The power transformer is a Hammond 269AX - widely available from vendors such as Digi-Key and Mouser. I used two octal sockets from National RF - one for the crystal socket - a common option in days gone by - and the other for the plug-in coil. You will also need a minaiture 7 and a miniature 9-pin tube socket - again available from most vintage components outlets. C1 can be a small trimmer as shown, but I used a fixed 33 pF silver-mica unit and the rig keyed cleanly. In common with the practice of the time, the transmitter did not contain any provisions for T/R switching Cystals were obtained from the AF4K Website (great service).

We did lots of different things for T/R switching "back in the day", but given the fact that I wanted plenty of isolation between the transmitter and the modern rigs that would used as receivers, I elected to drop about $80 on a good coaxial relay (>60 dB isolation on HF) that I got from Surplus Sales of Nebraska (stock #CX-600M), another outfit with great service. They are also a good source for one or more sets of spare tubes!

Given that some folks would like to build the transmitter, or at least look at some of the elements of a homebrew vintage project, I have compiled a complete W1TS PROJECT MANUAL that you can download by just clicking the link. The manual contains literally everything you need to know to duplicate the transmitter. One of the items featured in the manual is my COILS program to help you arrive at a design for a final output coil when you cannot or don't care to duplicate the one in the original publication. This program will prove useful in most vintage transmitter projects. Simply click on the link and then use the Save As option. The program does not require installation and is run as a simple executable file.

RESULTS

The rig was a pleasure to use and netted me half-a-dozen contacts in the first afternoon I put it on the air. It puts out about 4-5 watts and has so far received excellent on-air-reports.

States Worked: 46 and counting....

Total QSO's: 876 and counting..