The Drake SPR-4 receiver was the first "serious" radio I owned,
and in some ways, it was the one
of the best. I dreamed about this radio through my last couple of
years of high school, and sometime around 1980, I bought one that
belonged to Drake's Western Canadian distributor, Bob Fransen,
VE6RF. Now Bob is a real (European) craftsman-type, so the set was
in immaculate shape. Unfortunately, due to a financial disagreement
with my landlord, I only had this set for a couple of months before
I sold it back to Bob. Later, when I wanted to (re-)purchase it,
Bob had sold it to a friend of his.
Not long after that, I purchased an SPR-4/FS-4 from Don Moman, shortly after I met him. I used this pair for about a year, before I sold them to a friend of mine. He is still using them occasionally. I went on to many more modern receivers from Yaesu and Icom. Many years later, I bought another SPR-4, but I think that this one was in poor shape, and the front-end had been damaged by static or lightning. It didn't seem to be in as good shape as the first one, so I sold it off. Today, I'd love to find an SPR-4 in good shape, or even in condition suitable for restoration.
The SPR-4 is an excellent receiver mainly thanks to it's precision tuned front-end preselector. This gang-tuned PTO preselector protects the dual-gate MOSFET first mixer from overloading and intermod by simply heavily attenuating everything more than about 20 kHz either side of the signal frequency. The VFO is implemented with the famous Drake PTO, and has excellent frequency resolution for an analog VFO. The scale could readily be read to less than 500 Hz. All of the circuitry is solid-state, and the dial lamps draw more current than the rest of the set (at least at normal audio levels). The audio quality and fidelity is outstanding, thanks to the 4 pole L-C IF filters used in the 50 kHz second IF stages. These aren't as sharp as a mechanical or crystal filter, but they don't suffer from the group delay and ringing of "brickwall" filters. As many have pointed out, this can make quite a difference when listening to a very weak MW AM signal beside a local powerhouse with all of the attendant "splatter".
The main disadvantages of the set are the limited coverage and slow bandchange/slewing operations. There is a 23 position bandswitch (manufactured for 23 channel CB radios?) which selects one of 23 crystals, which in turn activate one of 23 500 kHz bands. If you were lucky, you could find one of the rare FS-4 synthesizers, which provided full coverage without any crystals. If you wanted to change bands, you would have to change the crystal switch to the appropriate band, change the band switch to the band indicated by the crystal switch, and then tune the preselector to the range indicated. This is a little awkward when you are trying to check parallels, a second receiver is almost mandatory.
My best logging on an SPR-4 was probably KIKI in Honolulu, Hawaii on 730 kHz, using a 400 foot beverage at my parent's farm near Edmonton, Alberta. What I remember more clearly, though, is the first time I turned on my first SPR-4; I arrived home late at night, and excitedly hooked up the radio and tuned to 20 meters. I was astonished at how easy it was to tune in and listen to the Russian and Eastern European hams on SSB, and that they were coming in so clearly that late at night. It was quite a step up from my old Heathkit GR-78, which required a safecracker's touch to tune in SSB stations. Some would argue that for DXpeditions, especially for MW DXing, there isn't anything that tops the Drake SPR-4. The R-390 or SP-600 boatanchors may outperform it in terms of ultimate performance, but Arnold Schwartzenegger hasn't accepted my invitation to our next DXpedition.