Thursday, June 11, 2015

Mini Beach DX Trip

My wife and I took a few days off for a short vacation to Galveston Island this week ( June 8). It was mostly a relaxing, family time, but one short period was set aside for a little radio play I wanted to try out the performance of a small QRP radio I had just obtained from a friend and I also wanted to enjoy the beach. The two seemed perfectly compatible as long as the radio did not dig too deeply into the swimming time in the waves!

Any trip includes some planning, but even the most careful of plans can result in something being left out. The plan for this trip was to try out the little AEA Engineering single band transceiver, not only as a QRP transmitter, but mainly to see how its receiver would work. The radio had been built from a kit by someone else and had ended up in an estate sale. The circuit was originally described in the December 1990 edition of QST magazine by K9AY.

Considering the little radio was just a single band affair, the antenna needed was also simpler. I took the vertical element from my recently taken down 20-meter ground plane. It had been built from salvaged parts from an old Hustler 4BTV vertical. It consists of three sections of inch and a half diameter aluminum tubing stacked together using pieces from the insides of disassembled traps from the original antenna. I used the original base of the 4BTV with its u-bolt clamps to mount it on a four foot long piece of water pipe that I intended to drive into sand at the beach.

Just as an aside, visits to ham fests will often turn up old trap verticals that are often real bargains. I always pick up these when they turn up because even if the traps are old and even ruined, the hardware, including the base and the tubing itself is OK for various antenna projects. Any u-bolts or clamps that might be missing can be picked up at a local hardware store at very reasonable prices. All of my antennas for either hamming or SWL and BCB DX-ing that are more than just wire affairs have all been built from salvaged materials.

Other items taken in the “ kit bag” along with the aluminum tubing for the antenna included pliers, diagonal cutters, a roll of insulated wire, a few short ( 20 feet) pieces of scrap antenna wire and a roll of electrical tape. There was also a 30 foot roll of used RG8X coaxial cable, three short pieces of RG8X with PL 259 connectors on just one end ( the connections to the antenna base used are made with “pigtail leads”-it does not have an SO-239 connector) and a roll of electrical tape. I also took a roll of salvaged plastic rope and three tent pegs in case guying was needed. ( you will notice that there are always a lot of “ salvaged” or used items in my projects...the hobby is by necessity a low budget operation!!! DX-ing need not be an expensive proposition!)

Power for the radio was to be provided by a motorcycle battery. The radio itself had been measured as putting out about 4 watts and on receive, drew very low current. Since the stay at the beach would be relatively short a bigger battery was not deemed necessary. A small, very light weight battery charger was taken to charge the batter in the hotel room at night.

Weight in these kinds of trips is always a consideration as one never knows how far the stuff will need to be carried. In this case, the radio gear was to be carried to the operating position along with the other beach items including cooler with drinks, towels, beach chairs and other items. Since you cannot always be assured of being able to drive up the water's edge, the distance needed for carrying is always unpredictable and usually results in more than one trip being made.

In our case, we were on Galveston Island off the Texas coast. It had already been determined that we would be going to the beach on the east end of the island, an area known as Apfel Beach. This area was relatively far from the built up, business portion of the island, miles east of the Pleasure Pier and other amusement areas. Crowding is not often a problem. We chose to set up in a paid-entry part of the beach rather than the free, public area to avoid noise from loud music being played by some beach goers ( a sore subject for my wife and is difficult to understand why some people have so little consideration for others)

Use of the paid portion of the beach is only $8 per day per car and is very reasonable and there are some restrictions on what can be done there. I was hoping playing quietly with the radios would not be among them. For that reason, we chose to go to the very far end of the beach area well beyond the last of those set up and just before an area restricted for swimming because of rip tides. It was still safe where we were, but just a hundred feet or so down the beach, the flags were up prohibiting swimming.

The disadvantage of the location was that it required a long walk from parking to the water's edge. That meant two round trips in loose sand totaling about a half mile to get everything to our chosen location. Temperatures were in the 90's and there was no shade. We did not have a beach umbrella and this portion of the beach requires any tents or tarp shading to be set up back by the parking line for vehicles.

Driving the water pipe base into the sand turned out to be a tougher job than anticipated. I had not brought a large sledge hammer, but just a smaller hand hammer due to weight considerations. It took considerable pounding and some twisting of the pipe to get it deep enough into the sand to support the vertical element. At this point, it is probably a good idea to advise taking a flat, wooden board along to place on top of the pipe when driving it in the ground, or the end of the pipe will be flared out by the pounding and you might find it difficult to get the u-bolts of the base or the base of the antenna itself to slide down over it.

The vertical element was assembled and tilted up for sliding of the u-bolts of the base down over the pipe and the nuts on the u-bolts tightened. Another suggestion from a lesson learned: It would have been good for me to have taken a small wrench to tighten the u-blots because the pliers I used did not allow for ease of operation under the bracket on the antenna base. It worked out, but took awhile because the nuts could only be turned about a quarter turn at a time because the ends of the pliers were so large. A 7/16's inch box-end wrench would have worked much better. ( planning, planning!)

Things did work out quite well. The antenna base mounting mast was actually in the salt water, negating the need to roll out numerous ground radials. I have learned over the years that salt water at the base of a vertical trumps radials every time!!

At this point the activity had finally attracted the attention of the lifeguard. It would soon be known if the entire operation would be quashed. He came over and just watched a minute as I rolled the coaxial cable from the antenna over to our beach chair area. I told him it was for a radio. He asked if the signals were that weak for music and reminded us that loud noise was not allowed. I then told him it was for listening to short wave radio signals and that there would not be loud noise and that we hoped to hear signals from around the world. I am not sure he really understood, but in a minute he just walked back to his guard tower, looking over his shoulder a few times, probably wondering at the weird things that showed up on his beach!

The moment of truth was soon at hand. The battery was connected, PL-259 screwed into the back of the small radio and it was set up on top of our ice chest as an operating table. It was then that I realized I had left my small headphones back in the hotel room. It was not a fatal error, in that the little radio does have a small built in speaker. There was not a lot of audio, so there was no danger of disturbing nearby swimmers, but it also required having my ear very close to hear the signals over the surf. But not to worry! If that was the worse Murphy's Law had to deliver that afternoon, things would be OK!

We had arrived at the beach about 11 AM Texas time ( 1600 GMT) and had gotten set up in less than an hour! Not too bad!

A quick tune across the 20 meter band showed plenty of signals, may of them quite strong. In the time between 1700-2000 GMT ( with breaks for swims! Priorities, priorities!) the little rig did OK. Several stations made it into the ham log and many more in the SWL log. The small portable key used for cw transmissions was a microswitch mounted on a small board with a knob attached, making it quite small and weighing literally only ounces. The battery outweighed all the gear except the antenna!

In the ham log we entered five stations from Florida...all quite strong over an almost all water path. There were also stations from Tennessee, New York and California. It was not the prime time for DX but still one station each from Italy, Russia ( an R7!), France and the Canary Islands were logged. The EA8 station was particularly loud and was heard working many stations for quite awhile. Numerous other European stations were also heard.

No broadcast stations were logged this trip, as the idea had been to make a quick check of the little QRP rig and the trip was not primarily a DX pedition, but a family outing. A general coverage receiver was not taken on this trip.

The advantages of a beach operation were confirmed once again. The salt water ground is like a S-meter multiplier on receive and almost as good as a linear amplifier on transmit.

Operating portable also has other advantages. Being away from buildings, homes, traffic and power lines meant that the seemingly ever increasing noise floor from electrical power, cable tv leaks and digital noises from computers was totally absent. It was a pleasant break. I would suggest when making such trips even leaving the laptops at home unless you are sure that there is no RF hash associated with their operation. Being out in the open is a real treat in that sense. Logging on paper is a small price to pay for the quiet, and entering the log entries into the computer later is like re-living the experience.

The disadvantages are the need to provide power, the weight of batteries and the possibility that there may have to be some lugging of the equipment by human power. Planning must be careful to make sure you have all you need without making the project one that would require a half dozen hired safari bearers to get it out there. A careful checklist should be made to make sure you don't get to your destination only to find operation is impossible because of a connector, jumper, plug, ( or headphones!) left behind. Antennas might have to be simple but remember the low noise brings signals that would normally be lost in the grass will stand head and shoulders above what little noise might be in your receiver. Signals that might not even budge an S-meter are easily copied.

There are other concerns, particularly with beach operation. You might not want to take your expensive receiver out where salt air, moisture and sand might damage it. That has to be weighed as well.

But all in all, such an operation can be truly rewarding. While this trip was limited by family considerations and a desire not to get totally fried by the sun with no shade available, it was worth the effort and reinforced my desire to make a dedicated radio trip.

Just don't forget the sun screen! ( Alovera helps relieve the pain of the burn!!)

Thursday, June 4, 2015

Developing DX-er's Ears

The last three weeks has seen a relative low amount of time behind the radios. Thunderstorms, rain, and flooding have hit Texas and in addition to everything else, the QRN ( static) has been horrendous. That has not to say there has been no DX logged, there has, but it has been at a cost in time, concentration and pounding of the ears to pull it out.

When the lightning has not been so close as to be dangerous to have the antenna connected, the upper bands have been listenable during the day, at least on frequencies above 15 mhz Early in the mornings Europeans and Russians would make it through on 15 and 20 meters, though 20 was often plagued with heavy static. In the late afternoons the regular flood of Japanese stations would be in with fairly good signals, though sometimes even on 15 meters masked by the static crashes. A couple of good catches were logged, including a South Korea on 15 and Kenya (5Z0L ) and Palau ( T88HR) on 17, though it took some good picking to pull out the callsigns This was on 24 May and all on cw. A group on Bear Island Svalbard-JW9JKA- was also heard on 15 meter sideband but it took almost fifteen minutes to identify.

The lower bands were all but useless for DX on phone. DX of broadcast stations on 120, 90, and 60 meters was a total washout and even weaker stations on 49 and 31 meters were tough to pull out.

This past weekend ( May 30 and 31) saw sunshine return to Central Texas, but on the low bands the static was still horrendous because there were still heavy storms in areas within the first skip zone on the low bands, and yes, static crashes are propagated just like desirable radio signals.

The WPX contest would normally have provided a treasure trove of signals, but for me, the event of a grandbaby's birthday precluded a lot of time in front of the radios ( there ARE priorities when there is a three-year-old involved!!) But even the available time on the low bands was still pretty tough. In the evenings, on 40 meters, only the strongest of Europeans were coming in Friday night Texas Time. Only the big club stations in Italy and Croatia were identifiable. Saturday night was a little better but once again only the powerhouses were pulled out. I did log about 35 DX stations through the crashes, notably stations from Poland, Cape Verde, Serbia, Germany, Slovenia, England, Bulgaria and Spain. All had to be in the S-7 to S-9 range to be readable through the noise.

There are ways of hearing things even in these harsh conditions. I have long been a believer that in hunting for weak DX or trying to identify a station in a jumble that the best filter “ is the one between the ears”. There is no physical or software filter in the world that can give totally QRM or QRN free listening. Mechanical or electronic filters can do nothing about two signals that are superimposed or can be so narrow as to strip the intelligence from an AM or Single Sideband signal. And when it comes to static, well that is a whole 'nother story!

The battle to fight static crashes has been going on ever since the days of the coherer detector. While not always continuous, the loud bursts can either totally cover the desired signal or in periods be so much stronger than the desired one that the receiver sensitivity is either pushed down as the Automatic Gain Control operates or that the overall loudness of the static forces the operator to reduce the gain to protect his ears.

In years past, this problem was solved in a simple way. The AGC in the receiver would be turned off and a hard diode clipper in an audio stage would be used to brute force chop off the higher noise peaks.

In some circuits, the level of clipping was adjustable, but in most it was not. There was a switch on the receiver panel marked “NL”, “ANL” or “ Noise Limiter” or just “ Limiter”. Many times if weak signals were involved, the “ bite” of the clipping circuit would not be deep enough and there would still be a considerable difference between the strength of the desired signal being listened for between the crashes and the crashes themselves. With the AGC off to prevent the receiver sensitivity from being driven down by the static and the higher peaks getting past the clipper, most often the “ Clipping” took place within the ears of the DX-er. I am sure that this resulted in more than one case of severely damaged hearing for a couple of generations of hams and listeners! It should be noted that the only way to listen under these conditions is with headphones. Trying to hear and copy through heavy trash with a loudspeaker is a total study in frustration. And if there are other family members in the house within earshot, such can be guaranteed to result in a pillow or something more deadly being thrown your way!

Newer noise blankers were developed in the early sixties that made use of sampling noise pulses usually outside the passband to which the operator is listening. These pulses would then be used to generate short duration signals to turn down the gain of the receiver for just the brief instant of the noise pulse. These can be seen to work by watching the s meter. These work pretty well on short duration pulse noise generated by spark plugs or other electrical “transmitters”. On some receivers, however, they generate some interesting artifacts. If there is a particularly strong signal in the passband that is being sampled and which is not actually heard where the operator is listening, that signal will cover the offending pulses, meaning the receiver won't work to get rid of them and the operator will hear annoying bursts of noise over the desired signal that duplicates the signal he is not hearing. If there is a jumble of strong signals, as during a DX contest, this results in a ragged up and down bunch of noise on the desired signal that is almost more annoying than the background noise that would be there without the noise blanker operating! I have been known to just turn the thing off when that happens.

Other noise limiters or blankers can have other effects;. Some can greatly distort stronger signals, especially phone signals. There are some radios that have adjustable noise limiters, with a control that adjusts how deep the device “ bites” into the signal to allow the operator to set up the best compromise between distortion and noise reduction.

Few of these devices really do much to help with the thundering crashes that accompany spring storms! Sometimes it gets back to the very basic idea of concentration. This means the operator must narrow his mental focus on just what it is he wants to hear. The same kind of effort is often used at a loud, crowded party where there is loud music and dozens of people talking and there is someone with whom you are trying to have a conversation. You simply concentrate on that one person's voice and mentally tune out the noise around you.

This same technique is used in DX-ing. You focus on the one pitch tone of the cw signal or the one voice in the jumble and attempt to mentally separate it from the crowd or from the background noise. It is not easy at first. All those other sounds are distracting, but you must learn to simply ignore them. The development of this ability is really the difference between a good DX-er and someone who just sits in front of the radio waiting for the DX to jump out the speaker. The development of this technique is a good explanation of why a seasoned Dx-er who started out with rudimentary, simple equipment consistently logs more DX than the new arrival in the game whose first receiver is an expensive, filter laden box who depends on those filters to separate the good stuff from the chaff. Sometimes those folks never develop the ability to mentally filter out the trash and sometimes get disgusted with the hobby and drop it because they can't understand why they have bought all the necessary stuff and can't get the good DX into their logs. Sometimes they even get to wondering if the hobby is all its cracked up to be or if the old hands are just making it all up!

Is there a way to tell you how to do this? As I write this, I am mentally scratching my head trying to come up with the words. All that seems to come out is “ concentration”. Pick out one voice and latch on to it, just as you would to one tone in a jumble of cw signals. Mentally listen through the noise and jumble of other signals. Sometimes with AM signals, if they are on exactly the same frequency without loud heterodynes this can be done with practice. With cw, for me it seems to be easier if the desired signal is at a low pitch. If copied at 1000 hz or so and a signal is 200 hz away, there is not much difference in pitch. But if copied at 300 hz, and the interfering signal is 200 hz away, it “ sounds” almost an octave away and is more easily mentally separated. If the interfering signal is much stronger than the desired, this becomes more difficult, especially if it “pumps” the AGC down. Selecting a faster AGC recovery time or, if possible, turning off the AGC altogether may help prevent the receiver from driving the desired signal down in level. If QRN or other man made pulse or broadband noise is not a problem, you may find that turning the noise limiter off will help separate voice signals on the same frequency because the Intermodulation Distortion that would tend to cause the audio signals to seem to blur together may decrease.

By the way, this brings up a point I have heard when people talk about different receivers. Some BCB DX-ers will say that the effect of mentally separating voices or signals in one jumble is easier in some receivers than in others, that some receivers tend to blur them together, while in others, signals though mixed, seem to be more “ separate”. My theory is that the Intermodulation Distortion either in the audio or perhaps even in the Intermediate Frequency stages might be better in some receivers than in others...that the linearity of the amplifiers might be better. That would make sense when some folks talk about how some of the older, high end tube radios seem to “ sound better” or clearer than some of the newer, perhaps budget solid state radios. The old tube amplifier stages, particularly in the older radios tended to be designed with more “ head room” to handle strong signals. To my ears at least, this was the case with the Hammurland and National receivers. But then, that just might be personal preference or what I got used to. I do know from working with broadcast audio for many years that Intermodulation Distortion can make music sound muddy even if frequency response tests with individual tones in an amplifier will show very good frequency response to very high frequencies, while an amplifier with low IM and even less high end response will still tend to deliver music that just sounds “ clearer”.

Back to the issue of filters for a moment. Software filters, crystal filters, and mechanical filters can be very narrow but cannot tell which signal you really want. They can be narrowed down once you pick out the one you want, but you must first determine which one in the pile you want and if you start with the window too narrow, you can't do that. And how can the DSP tell difference between a heterodyne you want to get rid of and a cw signal you want that might be beating against a carrier nearby? Those decisions are best left up to the person twirling the dials! And perhaps the real fine tuning is to be done with that “ filter between the ears”! Good luck in developing your DX-ers ears and fill that log up!