Shortwave Listening Post
| Top Row - Left to
Right HRO-500 Solid State HF Receiver Heath SB-620 Spectrum Scope Drake 2B converted to a "Selective SSB/CW Demodulator" Central Electronics Sideband Slicer Bottom Row - Left to Right Racal 6117 General Coverage HF Receiver SP-600 JX-23 HF Receiver B&W Sideband Demodulator |
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R-390A Made by EAC. This particular receiver was rescued from the "St. Julian's Creek Massacre" (see note) by Chuck Rippel, WA4HHG. It is totally restored to like-new condition. It is noteworthy to mention two specifics about this particular receiver. First, is its incredible stability. After warming the receiver for 24 hours, I zeroed with WWV on 10 MHz and left the receiver on my back porch for 7 days. The porch is enclosed, but the temperature varies with the outside temperature. At the end of this week-long test, the receiver had drifted less than 10 Hz! The second amazing feature is the sensitivity. It measured around 0.14 uV on most bands. That's for a 10 dB S+N to N ratio, not MDS (minimum detectable signal). The only thing I did to the receiver was to tap off the audio after the detector and feed it to a 50 watt audio mixer board which drove a 10" speaker. The fidelity was outstanding. This receiver is now back in the hands of Chuck Rippel and I have a much more humble replacement. Note: The "St. Julian's Creek Massacre" is description of the needless destruction of over 2000 working R-390A receivers by the DRMO branch of the U.S. government. This article appears from time to time on the Internet. I wrote the article out of respect for this incredible receiver design. |
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Hammarlund HRO-500 This receiver is on loan from Bob Bollenbacher. The HRO-500 is a fine example of early solid state excellence. These receivers are still popular with SWL's. HRO-500's are rare and a bit expensive when found. There are several interesting features. First is the synthesizer which selects the MHz. The famous PW dial reads directly in KHz with 1/4" between marks. Passband tuning is featured with six tuned circuits tuned to the 260 KHz final i.f. frequency. Oh yes, lest I forget, you can run this receiver on batteries. |
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RACAL 6117 This is my favorite shortwave receiver. This receiver features the famous drift-cancelling "Wadley Loop" design. Selectivity is accomplished by switched tuned circuits at the 100 KHz i.f. Frequency readout is accurate to 1 KHz and the KHz are read on the long, 35 mm wide plastic tape which travels across the top of the center bezel. MHz are read from the small semicircular dial below the KHz dial. MHz are dialed in, not switched in. As the MHz dial is turned, the tuning simply jumps from one MHz increment to the next. There is no bandswitch except that associated with the preselector. The 6117 is an American made version of the famous British RA-17. |
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SP-600 JX-23 This particular SP-600 is very well calibrated and quite sensitive. However, it lacks the selectivity needed under current band conditions. Also lacking is bandspread. The SP-600 does make an excellent short-wave receive, but in my opinion, they fall short of receivers like the RACAL. Certainly, they are not on a par with the R-390A, though they are easier to tune and the audio is much better from the SP-600. All-in-all, it's a nice receiver to have around your short-wave listening post. |
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W4THU "Selective
Detector" One of the major weaknesses of the R-390A, SP-600, and most other receivers of the 1950's is the absence of a product detector. I solved this problem by converting a Drake 2-B receiver to a 455 KHz SSB/CW demodulator. The conversion of the 2-B is simple and all of the mods are removable in just a few minutes. The i.f. from the R-390A is coupled into the Q-multiplier input socket on the back of the '2B. The tuning capacitor for the main VFO was rewired to tune the 505 KHz 3rd conversion oscillator to provide tuning across the passband of the main receiver. 2-B passband tuning and all bandwidth positions are still operable as is AGC. The modified Drake 2B provides all the usual functions of the '2B, including product detector, BFO, 50 KHz i.f. filtering, notch filter, and audio. Truly, the modified Drake 2B makes an outstanding SSB/CW demodulator accessory for any top quality receiver with a 455 KHz i.f. |
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B&W Model 370 Single Sideband
Receiving Adaptor This unusual unit works with receivers having i.f. frequencies between 450 KHz and 500 KHz. That includes a lot of territory. A product detector and BFO are utilized in a 17 KHz i.f. stage. This is a fine quality unit and provides excellent SSB reproduction. |
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