Saturday, June 22, 2013

DXing With the Watterson

This early period of serious DX-ing was done with a 1940's vintage Watterson table radio that had belonged to my grandfather. It was a simple receiver, of the basic design known as an “ All American Five”. This is the catch-all name given to the basic design of a five-tube superhet with an AC/DC power supply and no power transformer. The filaments of the tubes of these receivers were wired in series such that the voltage drops of all added up to about 120 volts, or the basic power line voltage. Thus no filament transformer was needed. High voltage for the plates of the tubes was obtained with a half wave rectifier operating directly off the power line, agin with no transformer. This allowed for operation off either AC or DC power but probably more importantly, kept the price of these radios to a minimum.

Of the versions of these radios using the larger, octal based tubes, all had the same lineup: 12SA7 pentagrid converter, 12SK7 Intermediate Frequency amplifier, 12SQ7 Detector, Automatic Gain Control and first Audio Frequency amplifier ( this tube has two diodes and a triode in the same envelope) 50L6 Audio Output amplifier and 35Z5 rectifier. Later designs using miniature tubes but otherwise very similar in design used a 12BE6 pentagrid converter, 12BA6 Intermediate Frequency amplifier, 12AT6 detector, automatic gain control and first Audio Frequency amplifier, 50C5 Audio Output and 35W4 rectifier.

Some of the basic multi-band short wave receivers used this same design and same tube lineup, including the famous Hallicrafters S-38 and S-120 series and the National SW-54 and NC-60 lines. These entry level SWL receivers were basically just the standard broadcast receiver designs with switched coils to allow tuning the higher frequencies.

This design did not have an RF amplifier stage, which resulted in decreased sensitivity on the higher bands. It also resulted in rather poor image rejection on the higher bands meaning these receivers often were plagued with spurious responses to strong signals. Performance on the standard broadcast band was pretty decent, though the single IF stage did not provide great selectivity. However, for DX-ing North American stations that were for the most part on 10 kilocycle centers, the selectivity provided was adequate except in the case of trying to pull out a weak, distant station directly adjacent to a strong local station. The only time the poor image rejection was a problem in broadcast band receivers was in the case of a strong local station above 1450 kHz. It might also appear near the low end of the dial. It was a much bigger problem on the short waves without an RF stage to tighten the selectivity of the front end.

The “image” frequency response of a superhet receiver design appears at twice the Intermediate Frequency away from the real frequency. Since the IF frequency used in these receivers was 455 kc, the image would be 910 kc below the actual station frequency. Thus a strong local station on 1450 kc would not only appear there, but also at 540 on this type of receiver. A station on 1600 would thus also appear at 690. ( I am using kc or kc/s for kilocycles per second for frequency references here because at this time period, the term “Hertz” had not come into standard use yet)

The other thing that had to be taken into account when using these receivers had to do with safety. Since there was no power transformer, the ground side of the power line was often connected directly to the chassis of the radio. Since polarized or three prong plugs were not in use in homes or on the radios at that time, depending on which way the cord was plugged in, even if the radio used a “floating ground” wiring scheme to avoid it, if a bypass capacitor to the chassis became leaky, there could be anywhere from 50 volts to 120 volts to ground on the chassis or case. Proper grounding and correct plugging into the wall socket was a necessity. With some designs, this voltage could also appear on an external antenna connection. Receivers made today do not present this danger, but if anyone is using one of these vintage receivers, this fact should not be taken lightly!! Regardless of receiver design, its always a good idea when using one of these today is to put a .05 microfarad capacitor in series with your external antenna.

All of these factors were pretty well common knowledge for people using these receivers in those days. Even as a ten year old DX-er, I had become aware of them, from reading articles in Popular Electronics, Electronics Illustrated and Radio-TV Experimenter. By this time, I was also going through my father's material from his radio-tv repair correspondence course.

The Watterson had a connection for an external antenna on the back. It also had a built-in loop antenna that was also the inductor for the tuned circuit for the input of the pentagrid converter stage. The connection was simply to the “high” side of the loop through a series capacitor. For short antennas this was not much of a problem, but when longer and longer antennas were connected to the radio in coming months, I found that the input was becoming detuned by the additional distributed capacitance to ground provided by the antenna, requiring a minor front end realignment of the radio. But I get ahead of myself.

The radio was basically a Broadcast Band receiver, but like many radios of its vintage, it tuned a bit more than the 540-1600 kc/s of what was then the Standard Broadcast Band. If you looked at the far right side of the tuning dial, the top of the band was marked by a “160” for 1600 kc/s. However, above that in small letters was the word “Police”. Up through the 1930's and into the early 1960's, a segment of the radio spectrum just above the broadcast band was used for dispatching police! As it came into my possession, the radio tuned up to almost 1800 kc.

The first external antenna used with the radio was thirty feet of wire suspended under the overhang of our house from two porcelain nail up insulators. My ground connection was to an eight foot piece of water pipe my dad drove in the ground outside my bedroom window. Another ground wire ran from that to a nearby water faucet. ( there was no plastic water pipe in those days).

We moved into the new house at Thanksgiving time, but it was really Christmas break time before I really had time to try out the radio in the full DX mode. There was a lot to do getting moved in, trying to get the yard started and numerous chores. I did get to use the radio for some casual listening while doing homework and found that on the outside antenna, it did a great job receiving WLS 890 from Chicago and KOMA 1520, Oklahoma City. The signals were “armchair copy” with only a little fading. And the Saturday night Grand Ol' Oprey came in great from WSM 650.

The first night of Christmas break I got all set for a night of DX-ing and hope for a full band scan. In those days, many stations signed off at midnight or 1 AM clearing some frequencies for more distant stations. There were hopes for Canadians. I was not sure how I would identify the Mexican stations. I did have a phonetic list of the alphabet in Spanish but did not seem to hear call letters given except at the top of the hour. The American pop stations made it easy, with jingles and call letters given between virtually every record.

Beginning that night, I soon had most of the so-called “clear channel” stations logged. In those days, they were truly clear channels. At night, that group of stations were truly alone on their respective frequencies. Though they were easy to log later, the first time they were heard and written down, it was a big thrill. It was like a night in Chicago that night. WMAQ on 670, WGN on 720, WBBM on 780 and WLS on 890. I sat in front of the radio with the most recent copy of the Whites Radio Log stations listed by frequency. I was puzzled by the fact that the first four stations from the Windy City, I could not hear a trace of WCFL on 1000, but only heard a Spanish language station. It was later that I learned about it being directional.

There were some other great loggings that first night: WSM 650 Nashville, WLW 700 Cincinnati, XELO 800 Juarez, Mexico ( My first officially logged foreign station, identified along with the other Mexican stations logged that night because it was carrying English language programming) WCCO 830 Minneapolis ( though with considerable splatter from WBAP 820) WHAS 840 Louisville, KOA 850 Denver, WWL 870 New Orleans, KDKA 1020 Pittsburgh, WHO 1040 Des Moines, XEG 1050 Monterrey, Mexico, WNOE 1060 NEW ORLEANS, KRLD 1080 Dallas, KFAB 1110 Omaha, KMOX 1120 St. Louis, KWKH 1130 Shreveport, KVOO 1170 Tulsa, WOAI 1200 San Antonio, WCAU 1210 Philadelphia, KSTP 1500 St Paul, WLAC 1510 Nashville, KOMA 1520 Oklahoma City, WCKY 1530 Cincinnati, XERF 1570 Villa Acuna, Mexico.

There were many other stations heard that night, but many channels on which they were found were jumbled with multiple stations. Logging the clear channel stations took much longer than it should have, because I had to formally identify them all. I also did not make it till midnight before I faded out myself.

In later nights, I began working on some of the stations on the “off” channels and weaker clear channel stations and began picking out the ID's of some of them. Some stations were elusive, showing me that DX-er's Law of Nature: fades will always come when a station is about to ID. Some of those heard in coming days that were weaker or were picked out of the initially unintelligible mess on some of the crowded channels included KXOK 630 in St Louis, KFEQ 680 St Joseph, Missouri, KEEL 710 Shreveport, WJR 760 Detroit, WHB 810 Kansas City, WKY 930 Oklahoma City, KAAY 1090 Little Rock, KYW 1100 Cleveland, WJBO 1150 Baton Rouge, WGAR 1220 Cleveland mixed with a Spanish language station, KTUL 1430 Tulsa, KWCO 1560 Chickasha Oklahoma, KLOU 1580 Lake Charles, Louisiana and KATZ 1600 St Louis.

I was still having trouble picking things out of the jumble. There was still time to develop “DX-ers Ears”. This is the mental ability to separate what you want to hear from noise and interference. It is an ability developed over time to concentrate on a specific voice or sound or song and mentally tune out the chaff. This ability seems to sharpen with time and I have found it particularly useful in copying CW on the ham and utility bands when even the sharpest filter cannot result in only one signal being heard. By concentrating on the specific pitch of the cw signal you want, even if it is the weaker of as many as three or four clumped up together, as long as the stronger ones are not pushing the AGC down, the “filter between the ears” can pick it out...just an aside again: This is why often old time CW ops( including myself in that group) sometimes prefer to defeat the AGC in the receiver completely in such situations and let the filter in the ear just clip off the higher volume signal while the brain picks out the pitch you want. This works particularly well with headphones. It was about this time that I also learned that picking signals out of the mud works better with headphones and installed a headphone jack on the back of the Watterson. ( this also allows listening late at night without disturbing the rest of the family) It may also explain some of my hearing loss that has shown up as I approach my mid sixties!

Those first few weeks I also noted but did not identify Spanish language stations on 540(strong!), 590, 640, 690, 730(very strong!!, 900 (strong!) 990, 1000, 1030, 1140,1160, 1180, 1220 (fading over WGAR) and 1580 ( fading over KLOU). At the time I never positively identified the Spanish language stations on 590 and 640, but knowing what I know now, I'll bet they were Cuban.

It was some months later in reading articles by CM Stansbury, Hank Bennett, and others whose names I unfortunately do not recall, that many Mexican stations went by slogans most of the time rather than call letters. I began collecting the slogans in a notebook as I ran across them in articles and finally began identifying some by the slogans ( “La Voz de la American Latina”, “ Desde Mexico”, “Radio Mil, “ etc) I also learned that some of the stations were simulcast on multiple frequencies and were able to pick them out that way.

Some of these stations have become markers or beacons for determining frequency just like the earlier stations had. Some of the big ones that really ran high power had amazing signal strengths, like XEWA 540 San Luis Potosi ( 150 kw), XEW 900 Mexico City ( 250 kw) and XEX 730 Mexico City that was listed as 500 kw at the time.

It was also about this time (mid 1959) that I ran across some articles in Popular Electronics about QSL-ing stations and soon had my very first Broadcast Band QSL. It came from XELO in Juarez.

There was a lot of reading of DX articles and perusing of catalogs going on about that time with eyes toward getting a better receiver or at least something that would get short wave frequencies about that time, but there was just no possibility of that financially. Thus grew the idea of enhancing the Watterson as much as possible to improve its performance. At age ten, there was not much that I had learned that could do much with the simple design.

There were attempts to squeeze the absolute most out of what there was by making sure the radio was operating at top efficiency. I probably almost wore out the adjustment screws on the variable capacitor trimmers and in the Intermediate Frequency Transformers peaking and tweaking. I did not have a signal generator or even a voltmeter at that point, so all alignment was one by ear.

My process at that time was to tune in a fairly weak station during the day ( so the signal would not be varying), then starting with the input IF transformer, swing the adjusting screw on first the primary and the secondary through an audible peak, then going to the output IF transformer and doing the same thing, going over and over the process. One could hear a mild “swish” as resonance was tuned through, though the peak was rather broad. There was some improvement in selectivity but there is a practical limit as to how much you can narrow down a single IF stage at 455 kc.

I did make one attempt at trying to tighten things up by introducing a little regeneration in the IF by soldering a short piece of wire onto the plate pin of the 12SK7 tube and moving it over near the grid. The problem was that when the AGC would recover on a weak signal, the stage would break into oscillation if more than just a little was introduced and on strong signals the effect was not too great.

Once again, its a matter of “if I had known then what I know now” I might have either come up with a way to disable the AGC or build an outboard Q-multiplier. But even as it was, there was usually adequate selectivity to separate stations that were 10 kc apart. I guess at the time I though pderhaps I could hear some of the European split channel stations if I could tighten it up, but as it turns out with the antenna situation at the time, it would never have happened anyway.

The idea of trans-Atlantic or trans-Pacific DX was always there, however. I still remember the one article by Stansbury that mentioned him logging JOJR and JOTR from Japan.

As tuning went on, I soon started thinking about improving the antenna. The thirty foot length soon grew to fifty, then 75, the took a turn and went down entire back and the west side of the house for a total length of about 130 feet. It was still under the overhang of the house, however and only about 9 feet above the ground. I am surprised I heard as much as I did given that situation. The wire used for antennas in those days was salvaged from unwound loop antennas off other radios and soldered-together short pieces of insulated wire. One segment was even made from split TV antenna twin lead.

This was truly a low budget operation!

At one point, the antenna situation took a quantum leap for the better. My dad came home with two 20-foot long 2X4's and put up two masts about 75 feet near my bedroom window and one at the very back of the yard. There were pulleys at the top to allow antennas to be raised and lowered. The wire for the antenna came from unwinding the field coils of a burned out six volt (!) generator ( not alternator, but generator) from a 1951 Chevy pickup. Even though this antenna was not as long as the original, the fact that it was higher and away from noise generated in the house meant it was a HUGE improvement!

This brought some weaker signals up out of the background, particularly in another interesting part of the dial, that above the 1600 kc mark that was then the top end of the broadcast band ( this was over 30 years before the expanded band came into being). This was the part of the dial marked “Police”. Low and behold I actually heard police calls up there. I was never really sure where they were coming from, but assumed at the time somewhere on the west coast because of some of the geographic references. They were only audible at night.

The thought then came that perhaps I could hear a bit of the short wave spectrum if I could shift the tuning of the radio up a bit. There was lots of adjusting of the local oscillator trimmers on the variable capacitor, but the move wasn't much. It did allow me to get up into the 160 meter band.

At that time the 160 meter ham band was shared with the LORAN navigation system and the characteristic phase shifting pulsing sounds were readily audible. But soon at night, I was hearing some amateur stations. In those days, the large majority of ham communications was till on AM with single sideband still in its growth stages. I only heard signals at night and among those, mostly stations with the W0 prefix, the "zeros" being in the Kansas, Nebraska, Dakotas, Missouri and Minnesota areas. It was still a thrill to hear my first ham transmissions.

There were also some other signals to be heard in that region. There were a few stations identifying with Morse Code....I was just learning the code about that time and it was with great difficulty that I managed to identify the first as “ RAB”. It was later discovered reading an article about Utility DX-ing that I learned that there were still a few navigational beacons in this spectrum and that this particular station was at Rabinal Air Force Base in Guatemala.

Nightly DX-ing continued through the 1959 time period with listening skills improving and careful tuning turning up more and more stations on other than the clear channels. It was in the fall of 1959 that I managed to stay up till just past 2 AM and found, lo and behold, XEWA had signed off and I was able to hear my first Canadian BCB station...CBK 540 in Regina, Saskatchewan.

The log was being filled with more and more lower powered stations as the “filter between the ears” developed more and more. One of the good ones ( with a QSL too!) was KSJB from Jamestown, North Dakota. More and more Mexican stations became identified. Radio Mil XEOY on 1000, XERPM on 660, XEDM on 1580, along with XET on 990, XEQ on 940, XEWK on 1190, XEB on 1220,XEAE on 1600 and XEQR on 1030.

The next big change was coming however. My dad was entrusting to me the “leftovers” from his radio correspondence course which included a six tube broadcast radio with an additional, as yet unconstructed addition: a short wave receiving converter! The radio itself had been on the shelf for several years and did not work and the converter was still scattered parts in boxes. But the idea of tuning up into the short waves was a big thrill. A big change was about to come.

No comments:

Post a Comment