My "Elmer" KØYTI (now AAØA) handed me a stack of 73 Magazine back-issues back in 1971. I was fourteen years-old at the time and already becoming bored with my store-bought radio equipment. I responded to an advertisement in one of the 73 Magazine issues (shown below) by sending off an order for $3 worth of MPF102 JFETs. I chose the MPF102 because it was the least expensive device offered!
Having received my field-effect transistors I set about trying to build a crystal-controlled oscillator for the 40m band. I mounted the components on several bakelite tie-strips, which were themselves screwed down onto a wooden base.
After several days of trial and error I finally heard the oscillator's signal on my shortwave receiver. I used my only piece of test equipment - a VOM that I had purchased from a nearby Radio Shack outlet store - to measure the total DC input power to the oscillator. With a fresh pair of 9Vdc "transistor radio" batteries in series, I calcuated the input DC power was just over 50mW.
Soon afterwards I had the idea of coupling this oscillator to my 40m dipole antenna. Having no idea how to calculate the optimum number of coupling turns at the tank inductor, I tested various windings by measuring the relative output at the antenna with my VOM, set to read "volts," in series with a germanium diode.
Having placed my straight-key in the circuit I began calling CQ. I didn't know if I could be heard outside my neighborhood, much less outside of my city.
I was still at it some days later with not so much as a nibble. I must have sent out five-hundred calls to no avail when, at last, I heard a station returning my call sign. It was W3EGL/Ø in Rochester, Minnesota; a distance of 388miles or 624km. We easily exchanged reports. Obviously, I was ecstatic over the contact.
Alas, both his QSL card and my old log book are long gone, so I can not tell you what the signal reports were. However, I recall from his QSL that he'd been using a pair of military surplus "Command" radios..."BC" something or other. I remember thinking it was pretty neat that he'd heard my tiny signal on such old and basic equipment.
I called for some time, off and on, in the following weeks, but this was to be my only QSO made with a handful of milliwatts in those days. What with school, dating and jobs, I eventually left amateur radio for what turned out to be a period of over twenty-five years.
I returned to the hobby in 2008 with the aim of making "homebrew milliwatting" my primary focus. In early 2010 I rebuilt the MPF102 one-stage transmitter from memory. Using the same drain supply voltage as before, I noticed the output power varied considerably from one MPF102 to another (the Idss and Vp values lie in a broad band of values from one device to the next), but it generally fell within the range of 10 to 20mW.
However, by 2010 I had developed an interest in early semiconductors. Accordingly, I replaced the MPF102 with one of the earliest modern silicon JFET's.
The first commerical field effect transistor appeared in France in 1958. This was the Technitron; brainchild of Stanislaus Teszner. Unfortunately, this germanium alloy device suffered from very low gain and high reverse-leakage.
Crystalonics of Cambridge, Massachusetts produced the first commercially available silicon JFET in 1960. Although the reverse-leakage was vastly lower than in the Technitron, and the transconductance was an order of magnitude higher, it was a poor perfomer in comparison with modern silicon JFETs. In fact I have four of these devices in my collection. Only one of the four - type C632 - is barely capable of producing sustained oscillation at 4MHz. The listed transconductance for the three type C631 devices in my possession is only 125uMhos with a pinch-off of 30V and up to 50pF of interelectrode capacitance!
It was the advent of Jean Hoerni's planar technology in 1959 that paved the way for modern, high-performance silicon JFET's. The first of these to be produced was a line of P-channel devices made by Texas Instruments, beginning in 1962: the 2N2386, 2N2497, 2N2498, 2N2499 and 2N2500.
I replaced the MPF102 in the QRPp transmitter of my youth with a 2N2499. My sample bears a date-code of September 1962; a very early device indeed. Given the May 1966 Texas Instruments price guide lists the 2N2499 for $12.90 (equivalent to $86 in 2010), I shudder to think what it must have cost in 1962 (the first JFET project to appear in QST Magazine debuted in 1966).
The RF power output was actually a bit higher using the 2N2499; at 28mW vs. 10 to 20mW with the MPF102s. I paired this transmitter with a regenerative receiver built from an early 2N2386 JFET (regenerative detector), direct-coupled at the source resistor to a 1957-vintage 2N107 PNP germanium transistor (AF amplifier stage).
On 6 May 2010, K1GOW in Providence, RI answered my CQ on 40m. Joe was running 3 watts to an end-fed wire only 15 feet off the ground. The distance between us was 167miles or 270km. The reports were 569/439.
On the next day I worked KA2PQY in Milmay, NJ (338mi/544km) with 569/339 reports.
On 10 May I worked two stations: N2AYI in Carney's Point, NJ (332mi/535km) with 579/539 reports, and, KA2KGP in Forestville, NY (340mi/547km) with 569/339 reports. BTW, Tom's QRZ page notes that he is a deaf CW operator.