Sunday, November 15, 2015

Tuning Tricks, Antenna Trimmers and Observations

       This weekend ( November 14 and 15, 2015) has indeed been an adventuresome weekend on the radio.  Three new  band-countries jumped into the log.  I call it a "band-country" when its a new country on a given band.  In this case it was Willis Island as the current DX-pedition got underway and I managed to snag them on 12 and 10 meters for the first time, having logged them on 15 meters from an earlier trip to the small island.  This is an example of how the only way to put a country into the log is via the amateur bands, because there is just nothing else there to generate a receivable RF signal! That takes my 12 meter total to 173 and my 10 meter total to 216.
       The other was Ascension Island heard for the first time on 80 meters, taking my 80 meter country total up to 118. I realize my total on that band is not that impressive compared to the " big guys" but given the size of my antennas and my relatively noisy location,  I am happy with any new one I can get! Of course this did not add to the overall countries total because Ascension has been there for a long time thanks to much more powerful transmitters pushing out the BBC's signal!
       Overall it was a pretty good weekend to be listening.  It was rainy most of Saturday and outdoor chores had to wait. The bands were fairly good. Friday night 40 meters was very good.  While it was not a new country, it was a thrill to hear Kenya , Western Sahara and the Canary Islands on the ham bands between what was actually 0200 and 0300 Saturday the 14th.
        Earlier time in the evening was unfortunately spent in front of the television watching coverage of the tragedy in Paris.  It also appeared that the BBC was quite strong in several spots, leading me to wonder if they did not lay on some additional transmitters and beam headings that favored the US for their coverage.  Perhaps some of you who keep track of them more closely might add comments. I could post them later if you should notice such.  International events often generate transmissions that are outside the norm.
       Saturday morning Texas time listening began about 1300 GMT. ( OK, so I slept in a bit!!) The initial WWV sweep showed it would be a good day. Beginning at 1348 GMT, the  2.5 MHz  WWV was S-9 + 20 DB with WWVH from Hawaii just barely detectable in the background. The 5 MHz WWV was S-9+ 20DB with WWVH clearly audible behind.  On 10 MHz WWV and WWVH were about equal strength with the S-meter at 20-over. On 15  Mhz surprisingly WWV was S-8 to S-9 but bouncing around a lot with no signs of WWVH.  The best was yet to come!. Even this early with sun probably just rising at their transmitter site, WWV on 20 MHz was already up to S-5 and S-6 and was clearly audible on 25 MHz!
       I noticed when checking the amateur contest listings for the weekend that the OK/OM DX contest ( Czech Republic and Slovak Republic respectively)  was going to be on CW and the JIDX ( Japanese) DX contest was going to be on phone.  That would mean some possible DX targets two ways.  One, it would be fun to see how many Czech and Slovak stations could be logged on CW and how many Japanese stations could be logged on phone on difficult bands.  But also, these smaller contests are also ways to log other countries listening for stations calling those hosting the contests.  The trick is often to listen at times when prop is NOT good to the host country and to listen for other DX stations calling THEM.  The " trick" is to look for pileups or to look on one of the spotting websites like DX Summit and look for stations host country hams are posting that might have prop to you and go park on those frequencies.
       Of course for listeners within the host countries its an easier deal.  Find a station in your country that is working a good run and park on that frequency and let them bring the DX to you!
       Or, if there is a relatively rare station working the contest in your continental area that those working the contest in the host country would probably like for a points multiplier,  park on HIS frequency and let him attract the DX to you.  This works particularly well on the " hard " bands for hearing the host country.  For example, here in Texas listening on 160 or 80 meters if there is a Caribbean station working the contest parking on his frequency will increase your chances of hearing the host country's stations on a tough band.
       The same works for DX-peditions. For example, this weekend was VK9WA on Willis Island was working stations and telling them to call  " up" or above their working frequency.  By tuning off the expedition and into the " pileup zone" you will find lots of goodies to put into the log.  It may take careful tuning and highly concentrated listening to pick callsigns out of the pile, but it can often be worth it.  QSL's sought from these stations will be easy to get as well, because you can believe those operators will remember the time and place where they were trying to bag a good one!
       For those whose CW is just developing, listening like this is great practice.  It always help in building speed to listen in deep concentration in tough conditions.  Also,  anyone can copy for short bursts at a much higher speed than their average copying speed.  As in physical exercise,  "stretching" always leads to improvement!
       This also applies to listening in pileups on phone, just in a different way. It will help develop your " DX-er's ears" by helping to develop the mental technique of pulling what you want out of apparent chaos through concentration. 
       In both cases,  phone and cw,  it may take callsigns going by several times to allow you to pick them out.  You will find yourself getting one letter at a time, until the entire callsign is filled in.  I usually write them down on scratch paper and while digging in a pile, either add each new letter to those already written down, or drop down a line for each "listen",  finding sometimes it may be required that a letter be changed because it was not heard properly the first time.  For those familiar with mathematical terms,  I guess you could say this is a form of " mental integration"!
       I have found that the same "mental integration" technique works in trying to identify a station down in the noise.  Listening over and over and over will sometimes have the signal fade up and down or noise bursts be present or absent in different places to let the ID finally pulled out and another one in the log!
       Of course the old hands reading this will be saying " I  knew that all along" but maybe trying some of these things will help the " newbies" learn a little faster, develop mental acuity and perhaps avoid frustration that might lead to ( "gasp!") dropping the hobby!
       These techniques can also be used for DX-ing other things than just the ham bands. Broadcast stations ID's or clues to identity can slip by quickly.  For those who run audio recordings, often running them several times will allow some form of mental integration.  For those with SDR's, the same might be the case, perhaps with different passband or selectivity settings.  For those who take the hobby beyond just listening to programs this could lead to bagging a good one rather than letting it go by because copy is tough. ( not that just listening for programs  is not a good thing, there are some great cultural things to be experienced listening to SWBC not to mention the exotic feel of listening with the fading and knowing you are doing it yourself without intervening wires...I am sorry but listening on the internet is just NOT the same!!!)
       OK, so back to Saturday morning. A quick check of twenty meters showed European signals coming in already at 1400 GMT. They were not strong but were readable. Many had a marked echo on the signals, indicating either multiple arrival paths or multiple backscatter effects. 
       Sometimes when signals sound like that here in Texas it is when they are passing through the auroral zone and are generally from Northern Europe ( particularly Scandanavia) or parts of Russia.  In this case, however,  the echo was pronounced on many Southern European stations.  Regardless of the mechanism, such makes copy of CW signals difficult because the delayed or echoed sounds tend to fill in the gaps or spaces between the " dits" and " dahs". 
        On voice signals, it makes understanding the words very difficult. The effect can be quite interesting sometimes.  I have heard instances where prop has brought signals  from Asia to my radio by both long and short path at the same time. There have been times when the long path was actually stronger than the short path and the "echoed" syllables were actually stronger than the "original". I still remember the very first time I heard this effect and was amazed.   It was in 1959 or 1960 while using my first, home built shortwave receiver and heard the Voice of America relay station from the Philippines early in the morning on 31 meters for the first time.
      In any event,  there are a few things that might be tried to make either the phone or CW signals more readable. The first thing to remember is that the Automatic Volume Control ( AVC) or Automatic Gain Control (AGC) is doing its best to "level out" the signal.  On CW particularly this means bringing up the gain when signals drop in level  or are absent.  This means the AVC ( or AGC) is actually aggravating the situation by making the echo and original signals the same strength.
       The first thing to try depends on whether you have a selectable AGC speed.  If so, select the slowest speed.  If not, it will be necessary to find some way to reduce the AGC effect.  The only way to do this is to reduce the strength of the signal to the point that the AGC has no room to "recover gain". If you have an RF gain control, back it off. If you have switchable attenuators, switch them in. As long as the signal is audible, it matters not if the S-meter is swinging above S-9! If there is enough difference in strength between the original and echo signal you might find a point where it becomes more readable.
       The same can be said of phone or AM signals. The effect may not be as pronounced and in some cases will not help much, but it doesn't help to try.  In some cases where the signal is " just ALMOST readable" every little bit can help!  The technique works better on SSB phone signals than AM signals.
       One other thing you might try if you have more than one antenna is to select a different one. A different antenna might have enough of a different pattern that one or the other of multi-path signals might be reduced or enhanced.
       For hams working CW and trying to make a contact with a station marked by heavy echo,  if its on a path going through the auroral zone,  be aware that your signal is being affected in exactly the same way on the distant end. If signals are strong and the other station is not answering your calls even though you know he must be hearing you,  its possible that the echo is making it impossible for you to copy you regardless of strength.  The answer is to slow down. Not just with more space between letters with your keyer or bug sending letters at the same rate,  but actually slowing down the  letters to allow more space between "dits" and "dahs". 
       I keep a straight key in the circuit wired in parallel with the output of my electronic keyer to allow quick and easy switching to a slower speed.  Often this is the difference between being just heard and actually copied.  This technique can also  be used in other times than just multi-path or echo situations.  Sometimes it can work in pileups and other heavy QRM or QRN situations.  When its tough, whatever works !!
       During part of the weekend's listening,  I switched away from the R-75 I had been using and fired up my old Hallicrafters SX-111. I still think this is one of the prettiest of the old boat anchors.  When I was in junior high school, an older fellow who was in high school at the time and an active ham  lived across the street from one of my aunts.  I would visit him frequently and he was  a great help with learning the code and generally learning radio in general. He had an SX-111 and I remember thinking it was really something. It was so much more stable and selective than the little National SW-54 I was using for SWL at the time.  I guess when the opportunity to do some trading to get one years laer presented itself,  it just would not do that I would pass it up.
       By the way, it is unfortunate but I have lost track of that ham over the years.  His name was Lou and his call was K5HFR. That call is not active in any data base now and of course many people have changed callsigns or obtained vanity calls since then and I have not been able to trace him.  Of course it could  be he is no longer active.
       In any event, as I fired up the Hallicrafters it came to mind when I switched to forty meters and calibrated the dial that for some reason I was struck by the need to adjust the antenna trimmer.  It occurred to me that many who use these radios today as collectors or who did not use them in " the day" may not know the purpose of this control.
       On these radios,   tuning is accomplished by multi-gang variable capacitors.  One section or "gang" tunes the mixer input, one tunes the local oscillator that generates the signal to convert the incoming signal to the Intermediate Frequency and if there are third and fourth gangs they tune the RF amplifier (s).  They must all track together to maintain even gain across the band.
       The rub comes in when an external antenna is connected to the receiver  Even if link turns on the coils are used to couple the input signal into the first tuned circuit,  capacitance of the antenna system can "load " the circuit somewhat and cause some detuning,  meaning the first tuned circuit will be pulled down in resonant frequency somewhat and might not track properly.  The antenna trimmer control is used to counteract this effect.
       There are multiple ways  it may be done.  In some receivers, the antenna trimmer is simply in series with the incoming "hot" lead of the antenna, with the idea being series capacitance will minimize the  capacitive loading effect ( see any electronics book on what happens when capacitors are connected in series).
       In some receivers the antenna trimmer is a small capacitor connected in parallel with the input tuning variable. In alignment, the first stage is tuned with the capacitor partially or nearly fully meshed.  Then when the effect of additional capacitance from the antenna is added,  by turning the antenna trimmer to a more un-meshed position, the effect of the added antenna capacitance is effectively nullified.
       It is not necessary for the receiver operator to know which method is used or in fact how it all works.  All one must do is when one stops in any general part of the band is to rotate the antenna trimmer control for maximum  signal. Any time you move an appreciable amount in frequency,  just peak it up.
       This is not to be confused with the preselector tuning in some receivers.  That is a whole 'nother deal!
       Hope all of this has been of some help and not just the rantings of an old guy! To many of you, this might be old hat,  but to new guys or folks dealing with boat anchors for the first time, some of it might be useful.  For those DX-ing the ham bands, it might be of some real use. As I have said before, none of these techniques should be taken as " the only way" but ways that I have found that work for me and hopefully will be of some assistance to others.
       Happy hunting and good DX!

1 comment:

  1. I do trust all the ideas you've presented for your post.
    They are very convincing and will definitely work.

    Nonetheless, the posts are too brief for newbies. May you
    please lengthen them a bit from next time?
    Thanks for the post.