An Interesting FT8 Afternoon

Lest my loyal blog-followers think I’ve taken a leap to the digital-darkside, rest assured this is not the case!

The only time that I (somewhat grudgingly) use FT8 is during the summer Es season, since most of the DX seems to have migrated to that mode. On Monday afternoon, during a moment of weakness driven by curiosity, I moved my receiver from 630m JT9 to 40m FT8 ... what might I see at around noon, via this popular weak signal digital QSO mode? To say that the results were surprising is an understatement!

40m at noon

The above screen capture shows the signals decoded between 12 and 1PM local time! Although it was surprising to see all of the east coast signals, it was shocking to see all of the signals (a dozen or more) coming from Japan and South Korea! All of them were working Europeans to their west, none of which were decoding here.

With an all-daylight path between VE7 and Asia, could these signals be coming via the long-path? If so, I would expect to see at least a few signals from other countries along the great circle path to Asia but none were forthcoming. Perhaps it’s a case of there being a sufficiently weak D-layer to allow signals to propagate on the direct path via the F-layer, in spite of the all-daylight path. What do you think?

I then moved the receiver down to 80m, and monitored there for the next two hours.

80m at 1500 local

The 80m screen capture above was made at 3PM local time! Once again, I was surprised to see so many signals coming from the east, in broad daylight! Is this further evidence of a weak D-layer or just a demonstration of the capabilities of FT8?

For both 80 and 40m, the antenna used was my 80m end-fed half-wave configured as an inverted-L ... 70’ straight up and 60’ horizontal. The feedpoint is one-foot above the ground and located beside the ocean, looking towards the east.

I then finished off the afternoon with a look on topband, using my 160m half-sloper. The screen capture of 160m was made at 5PM local time, fully two hours before my local sunset!

160m at 1700 local

Like the previous two bands, 160m was showing signals in broad daylight, from the east coast! Low D-layer absorption? ... salt water horizon gain? ... excellent antennas? ... or is this just the sensitivity of FT8 revealing 'normal propagation' that we can't hear on CW? I suspect that it's a complex combination of all of these factors and maybe others.

In reality, the weak-signal ‘digging power’ of FT8 is not too much greater than the threshold for audible CW ... hearing about 1 S-unit (~6-7db) deeper. Maybe that’s all it takes to peel-back, like an onion skin, another layer of hidden signals.

There are other weak-signal digital QSO modes much more sensitive than FT8. Both JT9 and JT65 can each hear more than an S-unit deeper than FT8 but at the expense of taking longer to do it ... there’s just no free-ride. I believe that the shorter (~15 second) sequencing of FT8 is the main reason for its overwhelming popularity, in spite of its lower sensitivity.

I’ll run this test again soon to see if Monday’s daytime prop was unusual or if it was typical of what to expect with weak-signal digital modes on the lower bands during the daylight hours ... either way, it was indeed, an interesting FT8 afternoon!

July's EME Window

With QSLs still arriving from previous 2m EME action, I was looking extra forward to late July's very short window.

When last month's activity was interrupted by my 140W brick amplifier catching fire, I was anxious to see if my repairs and homebrew RFC would still allow me to play on the moon. With July's best-positioned moonrises being too close to the sun (which was also rising at the same time), I was only able to spend a short time over two days before the moon travelled too far to the south and into my neighbour's trees.

Luckily I was rewarded with what seemed like very good lunar conditions, enabling me to easily work six different stations ... three of them being all-time new ones and boosting my EME initials total to 112.

I2FAK Franco / 16x19 el array
RK3FG Anatoly / 4x15 el array
G4SWX John / 4x16 el array
F4DJK Paul / 4x11 el array / #110
F5AQX Andre / 4x11 el array / #111
DL9DBJ Hartmut / 4x10 el array / #112

In addition, DL1VPL told me that he was able to copy me with his single 12el Yagi during the QSO with I2FAK! Needless to say, a contact between two single Yagi stations would be truly remarkable. I've only been able to copy a single Yagi station once over the years.

F4DJK's 4x11 el array

F5AQX's 4x11 el array

DJ9DBJ's 4x10 el array

I was gratified to see that letting the smoke out of my little amplifier last month apparently caused no permanent damage and the repair seems to be holding up ... but I'll leave the bottom off for now just in case it gets any more crazy ideas.

June Moonbounce Heats Up

Last week's favorable northern declination of the Moon allowed me two days of activity, once my moonrises had lagged far enough behind the early sunrises.

With fixed elevation and not having the ability to track the moon as it rises, I can only operate for about two hours before the moon gets too high. The highest elevation that I am able to work seems to stop near 20 degrees.

With QSLs from earlier sessions still arriving, I noted last week's activity was down somewhat from the previous month ... summertime activities usually take priority over EME for most moonbouncers.

During my two mornings of moon time I worked five stations which included two new DXCC countries, bringing my 2m DXCC total to 30. Stations worked at the end of June were:

                    ON4AOI #106 (new country)
                    OH3AWW #107 (new country)
                    I2RV second QSO
                    DK9WI #108
                    IK6CAK #109

ON4AOI - 4 X 14V / 14H array

OH3AWW - 4 X 9el array

IK6CAK - 9H / 6V 8el LFA array more

Interestingly, all of the stations answered one of my CQs, with one CQ having three different callers at one time ... pretty exciting and something that I don't think has occurred here before! But that wasn't the only excitement of the week.

In the middle of a CQ following my QSO with IK6CAK, I heard a faint 'crack' sound from my amplifier, an aging RF Concepts 2-135, followed by the unmistakable whiff of a 'too hot' electronic component ... every ham is familiar with this always unwelcome odor and it usually spells trouble.

During the next CQ, I saw a trace of smoke coming out of the amp's back corner vent holes, at which point I reluctantly shut things down in the middle of some superb EME conditions.

After tearing into the amplifier, the only thing that looked stressed was a small inductor (L14 below), part of the output filtering / impedance matching circuitry.

It looked a little darker and somewhat stressed and as I gave it a poke with a screwdriver blade, it immediately disintegrated into what you see below.

It was a small (1.2uH) encapsulated RFC which appeared to be wire-wound on a core material that I did not recognize and likely suitable for VHF. I surmised that after several years of 100% duty-cycle JT65 operation, the inductor had been over-stressed to the point of failure ... helping to filter all of those nasty high frequency harmonics can't be an easy job!

After a search of my RFC collection (see below), salvaged mostly from junked TVs, monitors, VCRs and other electronic cast-offs temporarily 'borrowed' for stripping from our local recycle center here on Mayne Island, I settled on a 1.2uH choke that I hoped would be a suitable replacement. It had just a few turns so I assumed it was wound on some sort of powdered iron or ferrite form. Whether or not it would behave at 144MHz was another question.

After reassembling the amplifier the following morning, I keyed up at full power during the EME window but halfway through my initial CQ I saw smoke and then flames coming from the inside of the case ... yikes! Shutting down immediately killed the fire and after tearing into the amp yet again, I saw that this time, the output coupling capacitor (C51) had completely destroyed itself.

The new inductor (L14) appeared a little heated, but I assumed it was only smoke-damaged from the nearby flameout of the capacitor. I replaced C51, an 820pF silver mica, with a higher rated one of the same value and, once again, gave it the smoke test ... literally.

After a few seconds, a whiff of smoke appeared from the back of the amp, followed by the SWR trip-out kicking in and shutting the amp down.

This time it appeared that the inductor was definitely complicit in the destruction of the capacitor as it was charred and black. I surmised that whatever core material the little inductor was wound upon, definitely was not suitable at 144MHz and had caused the little inductor to either change value or to saturate ... whatever it was doing had created a highly reactive condition in the output circuit, changing the output load impedance and sending the SWR sky-high.

This time I replaced the inductor with a homebrew one, wound on a plain phenolic former, hoping to avoid any ferro-magnetic / frequency compatibility issues. After reassembling the amplifier, it seemed to be happy once again and ran nicely for several 60 second JT65B sequences at full power with no smoke or component heating!

By this time I had run out of favorable EME windows as my moonrises were now too far to the south to keep me away from the neighbour's trees ... I'll just have to be patient and wait until the end of the month for the next definitive test. Let's hope there's no more smoke.

May's 'Red Ryder' EME Ops

There still seems to be a number of 'big guns' showing up each month, that I have not heard or worked before as well as several 2-Yagi 'little pistols' that I am able to work under very good lunar path conditions. I suspect that having just 1-Yagi puts me in the $2.95 'Red Ryder' category!



With the QSL's from last month's surprisingly good EME conditions just starting to arrive, May's moonbounce operation continued to produce good results.

Whether this is because of better than normal lunar path conditions or just a result of my neighbour's tree-pruning, remains to be seen.

The few days of operating in early May were, as usual, planned to take advantage of the Moon's closest approach as well as the Moon's most northerly declinations. The latter condition puts moonrises directly out in front of the house and looking across Georgia Strait's many miles of saltwater. The extra theoretical 'sea-gain' appears to be a reality under these conditions and allows my 9el Yagi to garner another 6db on both transmit and receive paths, making it perform more like a '4-Yagi' array.

Eight stations were worked this time around, with six of them being new 'initials', bringing my EME total from 95 to 101. Several of these stations were speaker-audible, at CW levels.

          NTØV #96
          IK7EZN #97
          EA2AGZ #98
          G4SWX
          F6HVK #99
          G4CDN #100
          DK5LA #101
          DK3BU

IK7EZN's cross polarized 4 x 13 array

 

 

 

 

EA2AGZ's 4 x 16 array

DK5LA's cross polarized 8 x 16 array ...very loud!

For now, any earlier thoughts of building a 4CX250 300 watt amplifier have been put on hold, while I continue to slowly work my way through what seems a never-ending list of workable stations.

April Moonbounce

My Moonrise

This week I had several days of unobstructed ocean moonrises as the Moon peaked on its monthly northern declination track. Thanks to the recent topping of my next door neighbour's large Douglas Fir, and removal of low-hanging branches, I am now able to track moonrises a little further to the south than before and can add two more EME days that were previously blocked by the large tree. All operations are on 2m JT65B mode, using a 9el Yagi and 140W output.




When I started (April 1) conditions looked as if they should be good, with lunar perigee (Moon's closest approach), degradation (background skynoise) and declination all looking favorable, but I was in for a surprise.

The rising yellow plot indicates the Earth-Moon distance growing further apart (increasing path losses) while the red plot indicates fluctuation in daily skynoise (temperature) near the moon. The blue plot indicates declination track from north to south ... for me, the higher the better.

courtesy: http://www.mmmonvhf.de/eme.php

Listening on the first two days (April 1-2) produced a few weak signals from the larger stations only and nothing from the more common '4-Yagi' stations and, no QSO's ... something was amiss. I can only attribute this to some real-time solar flaring during this two-day period and the resultant short term geomagnetic agitation the flares produced ... but almost as if the 'switch' had been flipped, the third day proved to be much different.

On day three, five new 'initials' were worked including one new state (New York) and two new DXCC countries! Truly surprising was that two of the stations worked were using just two Yagis, with both stations answering one of my 'CQ's.

Good conditions continued for the next few days, bringing my initials count from #87 to # 95, with the following stations all going into the log, turning a disappointing start into one of the best lunar sessions I have encountered:

HA6NQ, LZ2FO (two 13 el Yagis), EB5EEO, K2ZJ (two 14 el Yagis), DK5YA, S52LM, F8DO, PA5Y, SV6KRW, UA3PTW, OK1UGA.

April's operation brought  my 2m DXCC count to 29 and states worked total to 27.

SV6KRW's 4 x 8el Array

EB5EEO's 4 x 32el Cross-polarized Array (16V / 16H)

DK5YA's 4 x 22 Cross-polarized Array (11V / 11H)

As mentioned in my last EME report, I keep wondering when I will run out of stations that are able to hear my small station, forcing me to build a bigger amplifier for a few more precious db, but with the ability to occasionally work some 2-Yagi stations, the list of potential targets has increased dramatically ... perhaps the large Fir tree was a bigger attenuator than I had thought.

Thursday's Moonrise

I couldn't hold out any longer! The sight of a full-moon rising over the ocean a few nights ago was just too difficult to resist ... I would have to spark-up my 2m mini moonbounce system and see what was happening.






The QSLs are now all in from my last eme adventures in the early summer, bringing my total number of contacts to 80.

RW1AY used an 8 x 15el cross-polarized array

EA4CQ's 4 x 9el DK4ZB yagis

YU7AA's 8 x 13el nested array

NC2V used a 4 x 20el cross-polarized array

VE1KG's 4 x 17el yagi array

DK5SO used four 20' long yagis and 750W

My simple system uses a single 9el m2 yagi and an old third-hand 140W brick amplifier and built-in GaAsFET preamp. The yagi is mounted atop my 50' tower and fed with about 100' of RG-213 cable, along with its 2+ db of loss.

Looking directly out over the saltwater of Georgia Strait seems to provide the near theoretical 'sea-gain' of 6db, making the little yagi behave more like a box of four in terms of gain. As well, there are no noise sources when pointing out over the water at the rising moon. Not being able to elevate the antenna means 'moonrises' only, and usually gives me about 90 minutes per session before the moon gets too high.

Last night was surprisingly active, mostly with U.S. stations, as it was still early evening here but there were also several early-rising Europeans on the band.

One outstanding signal was from a station I had not worked before, OK1DIG, who was running a 4 x 15 element yagi array. I called him a few times when his signal was easily audible (-15db) but he seemed to only hear me later, replying to one of my 'CQ's, with his signal starting to drop here. This is often the case on 2m eme as a reciprocal two-way path is not always the rule. He was my only contact of the evening (#81) but also heard were K9SLQ, UT3MD, PA3FYC, all of whom I have yet to work.

OK1DIG's audible JT65B CQs

With another favorable moonrise tonight, albeit over an hour later, another go will be hard to resist!

April's Single-Yagi EME

With several QSL's from last month's EME action now arriving, April's 'best days' have just concluded. For me, operating with no antenna elevation, 'best days' mean those with northern-most lunar declinations (these put the moon rising clearly and almost directly out in front of the house, not in the neighbour's trees); not having the moon near the sun and also, having the moon closer to perigee (closest approach to earth) rather than apogee (furthest from earth). With just a single 9 element yagi, every db is precious.

A website that helps determine when these good days occur, is the Making More Miles On VHF eme page. A graphical display of several important elements will easily determine which days might be best to operate ...

courtesy: http://www.mmmonvhf.de/eme.php

... but I have also found success on days that don't look particularly great, with the moon approaching apogee and it's subsequent higher db path loss. As with most radio propagation, there is also some magic involved and, just like on any band, some days are simply 'better' and for no obvious reason.

This month saw six EME contacts, some with stations worked previously, in 2007, and not 'new uniques', while three were new, bringing my uniques total to 73, with this small, horizon-gain assisted system.

G4SWX John 4 x 16el array #71 ... answered my CQ
KB8RQ Gary 24 X 13el array!! worked with moon at 1 deg high
UX5UL Oleg 4 x 16el array #72
UT6UG Val 4 x 32el array #73 Val and Oleg both live in Kyiv, Ukraine
RK3FG Anatoly 4 X 15el array
K9MRI Joe 8 X 28el array - Indiana

G4SWX  4 x 16 el EME Array

KB8RQ 24 x 13 el EME Array

As summer approaches, it will be interesting to see how favorable the above mentioned variables will come into play as many of the best northerly declination days will also closely follow the sun and its increased background skynoise ... not so much a problem for me but for those bigger stations trying to hear a very weak signal in a noisier sky.