I heard my first signals and got my first decodes last night on the 2200m / 0.136 MHz band!
My first decode, which came immediately on my tuning to this band, was from WH2XND in DM33, 3356 km away from my QTH, with a signal strength in WSJT units of -27 dB. WH2XND was copied for most sequences between my start time of 0456 and 1120 UTC, when I received the last decode from him for the night. His best signal strength here was -24.
Immediately thereafter, at 0458, I copied Rob, K3RWR at -15 dB, again in WSJT units. Rob was also copied essentially every sequence through the night, with my last decode of K3RWR at 1306. Rob is only 213 km away, and his strongest signal was -6 dB.
I also copied WH2XXP, who is close to WH2XND. They are both in DM33, near Phoenix, AZ. XXP was copied frequently, but less often than the other two stations mentioned, and only between 0608 and 1032. His strongest signal was -26 dB.
I also heard some CW that was 569 on this 0.136 MHz band, but I was writing some PHP code and not really paying attention to the sounds in my headphones, and by the time I realized what I had been hearing it was too late for me to get callsigns as the station stopped transmitting just as I realized what I had been hearing.
All of this is using the same 40-foot horizontal end-fed wire attached to an AMRAD Active Antenna preamplifier that I have been using on 630 meters. There is a good deal of noise on 0.136 MHz, more than on 630 meters, but clearly it is not prohibitive even though I have done NOTHING thus far to mitigate it.
My plans at this point are to build some more preamps and to set up some BOGs (Beverages On the Ground). Mike WA3TTS has been EXTREMELY generous with his time and expertise, and has advised me on using binocular cores to roll my own beverage transformers. Mike has also been extremely helpful with advice on the great importance of doing everything possible to reduce QRN on the 630 and 2200 meter bands in order to optimize receive capability.
There are some really excellent references on the web on receiving system antennas and on reducing problematic receive noise. In this regard, here is a good article on receive-antenna matching by WA1ION. And Here is W8JI’s gateway page to his great work on receiving antennas. The section specific to beverage antenna construction is here.
And for some technical information on chokes, here is a great article on common-mode chokes by W1HIS. Also, Jack Smith K8ZOA (SK) wrote a great article on IMD in Broadband Transformers that you can find here. DX Engineering has bought the rights to much of Jack’s work, but they have NOT placed any of his excellent publications on their website. You can download much of it in this zip file. The website from which I got this link is in Czech, and is located here.
I haven’t collated my receive results on 630m yesterday yet, but here is my map from WSPRNet for the past 24 hours:
On 630 meters I’ve now received from as far west as Hawaii, and as far east as France.
Here is a look at signal strength in WSJT units vs inter-station distance for my wspr decodes on 630m. I apologize for the aspect ratio produced by the 30+ stations that I have now received. If you want to see the details, right click on the image, click on “open image in another tab”, open that tab and then pull on the edges of the browser to enlarge your browser window:
As expected, although the signal strength data for each station has a large range due to varying propagation, there is a significant negative correlation of signal strength with distance (t = -47.1, F = 2883, p<2e-16), and a significant positive correlation with station transmitting power (t = 47.3, F = 2236, p<2e-16), with a much weaker correlation with azimuth (t=7.1, F = 87 ), which fits with my subjective impression that my wire antenna is not extremely directional. There appears to be a very weak correlation of received signal strength with time evaluated as hours from midnight (t = -3.8, F = 14), although the weakness of this correlation may be exaggerated for reasons noted below.
The addition of callsign to the regression improves it, although not greatly. The Analysis of Variance Table for the multiple linear regression when callsign is included as an independent variable is shown below:
| Variable | Df | Sum Sq | Mean Sq | F value | Pr(>F) |
|---|---|---|---|---|---|
| Distance | 1 | 167266 | 167266 | 3968.795 | <2.2e-16*** |
| Azimuth | 1 | 5064 | 5064 | 120.154 | <2.2e-16*** |
| Power | 1 | 129770 | 129770 | 3079.131 | <2.2e-16*** |
| Time | 1 | 824 | 824 | 19.553 | 9.884e-06*** |
| Call | 29 | 164037 | 5656 | 134.214 | <2.2e-16*** |
As noted above, DISTANCE and then POWER are the most powerful predictors of received signal strength. CALL is also a predictor of signal strength and does add to the strength of the regression, because it includes not only the distance and power factors, but also all of those transmitting-station-related factors that we cannot include in this regression because we have no knowledge of them but which are very important: transmitter efficiency, transmitter feedline loss, transmitter antenna efficiency, directionality of the transmit antenna, local geographic factors at the transmit site that affect the strength of the transmitted signal at our heading, take-off angle of the transmitting antenna, etc.
Azimuth contributes essentially nothing to the regression, due to its very high correlation with callsign. In fact, removing azimuth from the regression results in no change in the r-squared value for the regression, indicating no change in the accuracy of the regression when azimuth is removed as an independent variable.
Time is a very poor predictor of received signal strength, with an F value of only 19.6. The weakness of time as a determinant of received signal strength may be exaggerated for several reasons: First, the dependence of received signal strength on time is almost certainly non-monotonic, and so will be poorly evaluated by a linear regression model. Second, many (but not all) stations turn off their signals during the day, so that there are no data available from those stations for analysis at those times, and the data during daylight hours is essentially limited to signals received from W3LPL. However, regarding this second point, even if the times used for analysis are limited to 2100-1300 UTC, time is still only a weak predictor of received signal strength, with the F value rising only from 19.55 to 41.1 with this change. Third, the received-signal time dependence if there is one would likely be affected by the local time at not only my station, the receiving station, but also by the local time at the transmitting station, and by the local time at every point along the propagation path between us. This would weaken the apparent correlation of “time” as measured by the time at my station only, with signal strength.
The image below is a plot of more than 10,000 received signal strengths for wspr signals on 474.2 kHz here at W3SZ vs time from midnight (UTC). Notice that there appears to be a ramp-up in signal strength from about 4 hours before midnight UTC to midnight, and then a ramp-down in signal strength between about 8-12 hours after midnight UTC. This is more easily seen in the second graph below, which is limited to times from 2100 to 1300 UTC.
Finally, below is a graph which shows the time dependence of received signal strength for all 32 stations that I have decoded on 474.2 kHz. If you don’t have a large monitor on which to view this image, the details may not be apparent to you but you will still be able to get the gist of the data. Opening this image in a new tab as previously described will make the image larger and easier to see.
The individual station graphs above make it easier to see the ramp-up and ramp-down at the beginning and end, respectively, of the receive cycle for each station’s signals. They also show some of the effects of “distributed time” along the signal path that I mentioned above. Notice that the most eastward station, F5WK in France, is heard only around 0000 UTC, whereas the most western station, K9FD in Hawaii, is heard only between 0500 and 1000 UTC. Similarly, W7IUV in Washington state is heard only around 0800-1100 UTC and W6EMC in California is heard only around 0800 UTC.
My station now has more than 10,000 decodes on 630 meters received over a period of less than a month, with very simple, minimalist equipment. So the message to you is get on the air and check out these bands! If I can do it with a minimalist station and only my rudimentary knowledge of things RF and especially things LF, you can have great success at your station. The only thing stopping you is inertia!
Have a great week and get going and enjoy the fun!
73,
Roger W3SZ