Saturday, July 13, 2013

Extending the Range

While the early days of listening had taught me much about tuning the short waves and identifying stations, there was a desire to see if the range of the receiver could be stretched somewhat. There was considerable dial space both above the 20 meter amateur band (14-14.35 mc) and below the 40 meter band (7.7.3 mc) leading me to believe that there was only a little space left to reach the 19 meter band (15-15.45 mc) above 20 meters or the 49 meter band (5.9-6.2 mc) below 40 meters.

I had the idea that if I could reach the 19 meter band I could hear some better DX in the daytime. The 31 and 25 meter bands were pretty much limited to North American signals during the daylight hours. Mostly during the day I was hearing Voice of America stations along with Spanish language stations I presumed were from Mexico and maybe a few South American countries. I had firmly identified XEWW on 31 meters, recognizing its ID from its Standard Broadcast Band sister stations XEW and XEWA, and with help from my newly acquired World Radio TV Handbook. Others were Spanish language programs from Radio Canada and a commercial New York City station, WRUL ( this station later became WNYW and many years later when moved to Okeechobee, Florida became WYFR).

From what I had learned aligning other radios, including the Watterson, which was still my main Broadcast Band receiver, I knew I could shift the frequency tuned by the radios by adjusting the trimmer capacitors on the side of the variable tuning caps, the section that tuned the local oscillator. I had been able to shift the Watterson a hundred kc or so, out of a tuning range of about 1300 kc. It was “stretched” up to a bit above 2000 kc, up through the 160 meter amateur band. Since the HF converter tuned a range about 8 mc or so, I figured that proportionately I ought to be able to shift the range at least 1 mc and reach 2 new bands.

Since the receiver had no cabinet, it was easy to reach the back section of the tuning capacitor with a small insulated screwdriver. I tuned in the 10 mc WWV and backed up on the trimmer screw a half turn. Sure enough, the radio tuned off WWV. If I was right, it would require tuning the tuning dial down a short distance to find it again, if the receiver had been shifted up in frequency. It only took a moment to find out that was true. It only took a little tweak to bring it back in.

I had hoped that the move would have been greater than that, but that was just the first try. I backed off on the adjustment another half turn, then once again brought WWV back into the picture. Several such adjustments resulted in moving WWV three or four divisions down the dial until I reached a point where further turning made no difference. The trimmer cap was very near its minimum capacitance and the adjustment screw was very loose, wobbling and in danger of falling out completely if loosened even a little more.

The proof would now be in the pudding. It was time to see if the tuning had been shifted enough to bring the 15 mc WWV and then the 19 meter band into range. Tuning the dial of the converter toward the upper end of its range was done with anticipation.

Before I hit the top of the range, there it was! Another signal from WWV, just as strong as the 10 mc signal had been. This had to be the 15 mc version. There was still a little room left on the dial, maybe enough to get at least a part of the 19 meter band. I soon hit stations! Rather than stopping on any particular one, I continued up until hitting the upper range stop to see if I went past the end of the entire band. However, luck was not with me on this one. I hit the stop without reaching dead center of the last station. At least I would have part of a new band, though it wasn't much. The entire space on the dial from the 15 mc WWV to the stop was less than half an inch.

The first station actually identified on the 19 meter band that afternoon was interestingly enough, one that I had just identified a day before on 31 meters: XEWW...a parallel broadcast with a recognizable announcer and slogans..” La Voz de la America Latina”. It was at the very top of the range against the stop. My World Radio TV Handbook that had opened the door for identifying so many new stations had it listed as being on 15160 so that meant that only about a third ot a half of the band would be tunable. Others logged that first day were Radio Canada and the venerable HCJB and one other Mexican station, XERR. I am certain of these because they are the first of the 19 meter stations on my “stations heard” list, even though I was not logging dates and times at that part of my listening career.

As an aside at this point, I would suggest that any beginning listeners begin keeping a log at the very beginning of their listening career, because there may come a time later when you will wish you had the data. Such information is very valuable in developing a feel for propagation and how your antennas are working. When I first began full data formal logging, I used ARRL amateur log books, but later determined that a formal log need not be something printed like that. The past 25 years or so I have used plain spiral notebooks such as high school or college students use, without ruled columns. I just write across the line in de facto columns the time, station, frequency, mode ( am, cw, ssb, etc) signal strength, power ( if available) and location. While many SWL DX-ers use more complicated methods of recording signal strength such as the SINPO method, I have always used the amateur radio RST system ( readability and signal strength for am or ssb with the third character for tone for cw). Since my earlier receivers did not always have S-meters, I used a “mental” S meter determination for the signal strength.

As you can see from this and earlier articles, there was really no way to determine anywhere near the exact frequency of stations being heard in those days. This was not unusual for any of the SWL receivers available for listeners then. There was no digital readout for any receiver and only the very expensive, top end Collins receivers had analog dials that could give much of a frequency indication closer than maybe 10 kc, and then only on the amateur bands. In those days, log entries, for me were only indications on which band the stations were heard, i.e. 41,31,25 or 19 meters, or the 40 or 20 meter amateur bands.

After being satisfied that the 19 meter band was being covered and logging a few stations, I decided to try moving the receiver in the other direction to see if 49 meters could be received. I knew that there would not be an easy way to “band switch” but I wanted to know if it could be done. I guess I just assumed that if I wanted the additional bands one way or another, I could just retune the trimmers each time. Using the same method of “sliding” WWV at 10 mc but tightening the trimmer instead of loosening it, I shifted the range of the receiver in the other direction. However, I soon reached the end of travel of the screw on the trimmer and it was very tight and I still had not reached the 49 meter band. I am not sure what frequency it would reach, but it was still above 6.2 mc and I never heard a broadcast station. I pulled the trimmer adjustment back out and decided I would just have to be happy with the three bands ( or more accurately 2-1/2).

It was only some years later, after I had already obtained my first commercially built general coverage receivers, that I wonder why it had never occurred to me that another method could have given me the lower frequencies. It would have been a simple matter of adding a small parallel disk ceramic capacitor across the variable. It would have been small, probably 50 pF or less and would have shifted the local oscillator frequency down. It could even have been switched...with another across the input variable to help it track, too. Something so simple, but it did not occur to me at age 11. But it was a time of learning and sometimes the obvious now was not so obvious then.

In years since, I have thought of a number of ways to improve that original receiver, which I still have. It had a number of design problems that could easily be corrected and greatly improve the performance, particularly with regard to stability, selectivity and image rejection.

But at the time, I was just happy to have anything that would get me on the short waves. The next few months were a wonderful time of discovery. I began learning about listening at different times and developing my “DX-ers Ears” to find a whole new layer of DX possibilities.

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