The very first receiver that I used in 1967 was Torn E.b. which belonged to my father. It was a robust German WW2 TRF receiver with just 4 battery tubes (valves) RV2P800.
The big band switch knob in the middle of the front panel turned the huge turret. The dial was in units 0 to 100, and there were tables that appeared in the front panel windows for each range as the turret was switched. These showed conversion from dials to kHz. The RX could receive AM and CW. To obtain the best sensitivity and selectivity in AM the feedback control knob in the upper right had to be carefully adjusted to the point before the oscillations started.
For CW the feedback was adjusted so that oscillations just started, which was the point of highest sensitivity. The frequency range of Torn E.b. was very wide, from VLF 100kHz up to just over 7 MHz, so it was useable for the 3 amateur LF bands.
In spite of its simplicity it worked very well and I logged a number of 80m AM stations back in 1967/68 (yes, AM was still used and SSB stations were rather rare). Later I even used it with TX on 160 and later on 80m.
Besides Torn E.b. I used Philips CR-101 superhet RX for all the short wave bands. This was a communication RX built in the Netherlands during the WW2 and utilized 8 tubes (types EF8, EF9, ECH3, EBF2, EM4) and covered 1.5-30MHz in 5 ranges. Mechanically it was built nicely. The upper big tuning knob in the centre controlled the coarse tuning on the big frequency dial. The lower big knob was the bandspread fine tuning with its separate dial.
Later my father acquired the American RCA AR-88F, a great "boat anchor" which I still keep until today.
This RX was probably left here in 1945 by the American army after liberating Pilsen and the west of our country. With weight over 40kg one could be sure this would hardly be ever stolen!
AR-88 receivers were originally used for diversity reception. Three units were mounted in a big rack and connected to different separate antennas which helped to obtain better signal quality by eliminating fading/QSB. Hence the little knob designated "Diversity IF gain". This knob was not used in the standalone unit, so it lent itself for a modification - control of the of the Q-multiplier which was added and greatly improved the selectivity. (Later the Q-mult was removed in order to get the RX into its original condition.)
The radio only used 8 octal metal tubes and single conversion with 455kHz IF.
Separate RX and TX were still widely used, no transceivers. This means that one would first find a station on the RX, then use the netting or, as we used to call it, "TX silent tuning" (VFO on
with no power to antenna). The TX frequency was tuned to the same frequency as RX, and then one could start
transmitting. Some skill was needed to tune to the zero beat or to the correct pitch of the received signal, otherwise the other station would not hear you.
In 1971 I built my first CW TX for 160m with the metal tubes 6AC7 at the VFO and 6F6 at the PA stage (or Russian equivalents respectively).
A lot of experimentation was going on in those days with the then popular "differential keying", a method of sequentially keying first the VFO and then the PA and vice versa, to avoid clicks at the rising and sloping part of the keying characters. Perfect tone could be achieved if the circuit was properly designed. The RC constant in the keying circuit could be altered so the tone changed from "hard" keying to soft "xtal" tone. You could receive a 599x report for such a nice crystal tone.
Apart from home built transmitters and other station accessories we used a lot of ex-WW2 or 1950/60s
surplus military receivers, mostly Czechoslovakian, German, Russian and some American.
In Czechoslovakia a number of German WW2 receivers were more or less spread among hams. A lot of the aircraft "cube" receivers EK10 (E10aK), EZ6, were in use, some with home made convertors, but especially the long wave RX E10L (EL10) that were widely modified for 160m and used by many OL and OK hams. These receivers were cubes of approx. 24x24x24cm. Mechanically they were made of several blocks with connectors so the maintenance was easy, also they all used one single type of miracle tube RV12P2000. Although not utilizing any crystals they had very good selectivity, achieved by simple IF LC filters on 130 or 140kHz.
I used the modified E10L on 160m for many years to full satisfaction and I regret that I got rid of it in the 90s.
When I got my all band licence in 1975 the easiest way in those days to get on the higher bands with the tube 160m CW TX was to simply double the frequency in the PA. The PA tank circuit was tuned to 3.5 MHz, efficiency was low so the output power was QRP but it worked and a lot of nice QSOs could be made.
In 1976 I built a 3 band CW TX (VFO-BA-FD-PA) with EF80 at the VFO and EL81 at PA.
Later a "VFX" was added to the station. This was an all band transistor exciter with VFO and switched CO (crystal oscillators) mixed to obtain signal on all 6 bands (no WARC bands then). The VFX output level was low so I built a two stage PA with one German LS50 (later changed to Russian GU50). The power was up to 70W on LF bands and around 30W on 20-10m. This was my highest QRO in those days.
A separate power supply was used to power all the equipment so in spite of low power the station was rather big.
The separate PSU concept had the advange of full control over plate and grid voltages of the two stage PA and this was a great tool for various QRPP experiments (see QRP).
Operating such a station was complicated, imagine all the knobs and controls that had to be tuned when changing the bands. Tuning control, peaking the VFX exciter, peaking the driver stage, switching the driver LC circuit and PA pi-network coil, tune PA and ANT capacitors. Quite a job! Then net to the RX frequency (remember, this was a separate TX). But it was fun.
I still recall the smell of the old radios, the smell of the hot tubes and resistors, but mainly the silence. Yes, it was a silent station. There were no fans in any of the equipment so no annoying noise! Sounds unreal today, doesn't it, when each PC, transceiver, PSU or PA has its own noisy fan.
Over the years a lot of nice and interesting old radios came through my hands. To name a few, the Czechoslovak Tesla made Lambda 4 and 5 and the newer K12. CZ Army surplus RM31 and R3. US HRO and its German copy Korting KST, German MWeC, KWeA and the perfect E52, Soviet huge R250 etc.
Feeling the need for a transceiver in 1977 I decided to build it. Not the whole thing but utilizing the AR-88F on the RX part. AR-88 is a single conversion superhet with 455kHz IF,
so it offers itself to a relatively straghtforward way how to design a transceive adapter, using the local oscillator of the RX. Without any mod to the radio, the LO signal was fed via a small cap
via a thin coax cable and lead into a separate box where it was mixed with a 455 kHz oscillator (tuneable +/- a few kHz which served as RIT/XIT), then
passed through band pass filters for all the bands (including the new WARC bands), amplified to 1 Watt level and the TCVR was here! Just tune the RX and the TX followed, what
a flexible operating!
I used this set up for many years both on QRP and "QRO" 30-70Watts (with the single GU50 tube PA) and achieved 5Band DXCC with this.
Some years later I modified this transceive adapter tube PA to solid state QRP PA, added a DBM DSB modulator in the 455kHz oscillator path so I became QRV on DSB as well. Although using DSB (both side bands and suppressed carrier) no one would find out that I was not SSB, as only one of my side bands came through their RX SSB filters!
In 1979 another project started - building a CW/SSB 144 MHz solid state transceiver ("TRX Klinovec" designed by OK1DCI). It took me 8 long years to finish it but finally it got me on VHF.
This TCVR's output power was 50mW so I built in a 2 stage amplifier boosting the output to 3W.
In the early 1980s another interesting HF radio came my way, a Tesla ZVP-2. This Czechoslovak communication RX from early 50s was designed for frequency ranges 3 - 24 MHz and was used for diversity reception (like the AR88). A set of three receivers were rack mounted side by side and used with one common local crystal oscillator unit and antenna distribution unit. The radio had a precise projection frequency readout. This presented a kind of challenge to me, so I designed and built another transceive adaptor utilizing the local oscillator of ZVP-2. I only used this for a short time because of its size I soon decided to sell it and thus obtain space in the shack for newer equipment.
1987 - 1997
In 1987 I brought a secondhand Yaesu FT-101E from a radio rally in England, my first commercial TCVR. I was very pleased with it, it was in perfect condition, still with the protective foil over the front panel.
After studying the circuits and Fox Tango newsletters I soon made a few modifications that greatly improved its performance,
a notch filter for the first wide IF, replaced the mixer with Plessey SL6440, enabled TX on 10MHz and added 18 MHz in the unused band switch position.
I enjoyed FT-101E for about 5 years until I bought Yaesu (Sommerkamp) FT102 line, with FV-102DM digital memory VFO and FC-102 antenna tuner.
1997 - today
Era of modern solid state transceivers started but at OK1CZ it took quite a time until I decided to get a new HF RIG. Reason being that it was hard to find a radio that would match not to mention beat the performance of the FT102.
Finally I bought the Yaesu FT920, which would not beat the excellent RX of the 102 but had the advantage of instant band change, no tune PA, 6m band, DSP etc.
Good thing was that FT920 uilizes the same IF as FT102 so with a little mod the IF signal could be fed from FT920 into FT102 IF board, which was equipped with all the narrow CW and SSB filters. This resulted in some very interesting possibilities. E.g. listening to the same signal processed by the FT920 wider IF path and at the same time by the sharp filters in 102's IF and finally mixing the audio from both radios to the mono or stereo headphones.
A few years later I sold the FT920 and replaced it by Icom IC746PRO an all band radio with the bonus of 2m band which I use mostly in the VF contests from my home QTH. (A modification is recommended in IC746PRO in order to solve the driver IC overheating problem). Being DSP it sounds different from the analog ones but I generally like the radio.
I have had the chance to test various modern radios, so for some time I had Yaesu FT1000MP Mark5 Field and Ten-Tec Orion II on my desk., later the FT2000 and Kenwood TS480.
For portable, mobile, contests and DXpeditions I used Elecraft K2/100, FT817ND and FT100, later replaced by Elecraft KX2.
In 2008 first experiences with SDR Perseus, later with various other SDR equipments such as. SunSDR, TS-890S, FT-DX101D etc. But I still like the classic radios best.