This was a busy week, but I managed to work a few more stations after my first contact with Wayde, K3MF, which I described in the prior blog. Since I worked Wayde, all of my subsequent contacts have been digital, using JT9.
On Wednesday I worked John, W3HMS twice, first using FT8 and then using JT9. I then worked Eric, NO3M about an hour and a half after I worked John. That was done while I was at Hilltop. Later that evening I returned home and transmitted WSPR with a 20% duty cycle for a while. I then switched to JT9, and after making that change I no longer had transmit output. I tried rebooting the remote computer but that made no difference. I could not reboot the K3 that was was using for both Rx and Tx because I had not set up pin 25 on the accessory socket on the back to act as a remote “ON” button. So that was the end of my transmitting on Wednesday.
My long term plan was to use one of my openHPSDR SDRs for MF and LF work anyway, so on Thursday rather than wring up the accessory connector for the K3, I substituted one of my openHPSDR Hermes transceivers for the K3. I added 25 dB of attenuation between the Hermes RF output and the input to the ENI 1040L amplifier, as that amount of attenuation keeps the input power going to the amplifier under 1 milliwatt. With the 25 dB attenuation in place, a drive level of 21 on the Hermes gives me 100 watts Transmitter Output Power.
I wanted to use the SDR rather than the K3 because all of the SDR controls are available on the remote VNC screen that I see at home when operating remote, whereas the K3 is “invisible” when I operate remote. Plus with the SDR I get two nice spectral displays and waterfalls that extend beyond what WSJTX shows me. The SDR gives me two receive slices, and I use one to run an instance of WSJTX in WSPR mode, and the other to run another instance of WSJTX, this one in JT9 mode. That way I can monitor activity for both modes simultaneously. In fact, I can use one slice to monitor 630m and the other to monitor 2200m simultaneously! You can see on the image at the top of the screen that both WSPR activity and JT9 activity are robust on a Friday night.
Being “fresh meat” on the band, I quickly made four first-time contacts in less than 30 minutes as soon as I fired up the radio this evening, working one after the other WA3ETD, K9SLQ, N3FL, and K9KFR. Below is a table showing details of my 630m contacts thus far.
| Call | Mode | Grid | Azimuth | Distance km | Report Sent | Report Rcvd |
|---|---|---|---|---|---|---|
| K3MF | CW | FM19sr | 28 | 80 | 599 | 449 |
| W3HMS | FT8 | FN10mf | 266 | 88 | -21 | -15 |
| W3HMS | JT9 | FN10mf | 266 | 88 | -24 | -21 |
| NO3M | JT9 | EN91wr | 240 | 385 | -07 | -25 |
| WA3ETD | JT9 | FN33lq | 32 | 450 | -04 | -27 |
| K9SLQ | JT9 | EN70 | 277 | 781 | -10 | -24 |
| N3FL | JT9 | FM19ka | 215 | 172 | -08 | -17 |
| K9KFR | JT9 | EN71 | 281 | 804 | -10 | -24 |
In WSPR mode, my transmitter has been heard a bit further out than my longest JT9 contact, as you can see from this list of stations who have heard me on WSPR:
| Timestamp | Call | MHz | SNR | Drift | Grid | Pwr | Reporter | RGrid | km | az |
|---|---|---|---|---|---|---|---|---|---|---|
| 2018-03-17 05:12 | W3SZ | 0.475722 | -16 | 0 | FN20ag | 0.001 | VE1YY | FN85ga | 1149 | 59 |
| 2018-03-15 02:32 | W3SZ | 0.475735 | -26 | 0 | FN20ag | 0.001 | N1DAY | EM85 | 818 | 232 |
| 2018-03-15 03:22 | W3SZ | 0.475729 | -22 | 0 | FN20ag | 0.001 | VE2PEP | FN46hc | 747 | 28 |
| 2018-03-12 00:38 | W3SZ | 0.475731 | -23 | 0 | FN20ag | 0.001 | W4KZK | EM97 | 538 | 236 |
| 2018-03-15 03:44 | W3SZ | 0.475732 | -24 | 0 | FN20ag | 0.001 | N1JEZ | FN34im | 521 | 24 |
| 2018-03-15 03:44 | W3SZ | 0.475731 | -20 | 0 | FN20ag | 0.001 | AA1A | FN42pb | 482 | 64 |
| 2018-03-17 04:08 | W3SZ | 0.475763 | -8 | 0 | FN20ag | 0.001 | W1XP | FN42fo | 450 | 53 |
| 2018-03-17 05:10 | W3SZ | 0.475728 | -15 | 0 | FN20ag | 0.001 | WA3ETD | FN33lq | 450 | 31 |
| 2018-03-15 03:14 | W3SZ | 0.475731 | -20 | 0 | FN20ag | 0.001 | NO3M/3 | EN91wr | 385 | 296 |
| 2018-03-16 22:52 | W3SZ | 0.475728 | -25 | 0 | FN20ag | 0.001 | WA3TTS | EN90xn | 347 | 277 |
| 2018-03-16 21:18 | W3SZ | 0.475730 | -19 | 0 | FN20ag | 0.001 | K3RWR | FM18qi | 221 | 195 |
| 2018-03-16 22:22 | W3SZ | 0.475730 | -18 | 0 | FN20ag | 0.001 | K3RWR/3 | FM18qi | 221 | 195 |
| 2018-03-14 22:52 | W3SZ | 0.475732 | -14 | 0 | FN20ag | 0.001 | KJ4YBS | FM28bh | 218 | 178 |
| 2018-03-12 00:30 | W3SZ | 0.475731 | -23 | 0 | FN20ag | 0.001 | W3LPL | FM19lg | 145 | 220 |
| 2018-03-16 22:52 | W3SZ | 0.475731 | -23 | 0 | FN20ag | 0.001 | K1BZ | FM19ne | 144 | 213 |
| 2018-03-16 21:26 | W3SZ | 0.475730 | -15 | 0 | FN20ag | 0.001 | N3FL | FM19ua | 142 | 192 |
| 2018-03-15 02:32 | W3SZ | 0.475731 | -24 | 0 | FN20ag | 0.001 | K3FOX | FM19qf | 129 | 206 |
| 2018-03-17 04:08 | W3SZ | 0.475730 | -19 | 0 | FN20ag | 0.001 | AA2UK | FM29pv | 114 | 111 |
| 2018-03-14 21:28 | W3SZ | 0.475731 | -21 | 0 | FN20ag | 0.001 | W3HMS | FN10mf | 85 | 267 |
That I would be heard at greater distances with WSPR than I was able to achieve with JT9 QSOs is of course expected for several reasons: WSPR is inherently more sensitive (-31 dB WSJT units) than JT9 (-27 dB WSJT units), the WSPR reception only requires one-way communication, and there are many more chances over time for a station to copy me using WSPR than JT9 just by virtue of total minutes spent transmitting in each mode to name a few.
I have been able to receive much further than I have transmitted. Those of you who have followed my blogs know that earlier in the winter I was able to receive WSPR from Hawaii on a number of occasions. In the past 2 weeks I have received 41 unique calls; but two of these, the longest two “receptions” are either false decodes or pirates. Here is a list of stations received by me on 630m in the past 2 weeks, in descending order of path length. Starting with and including EA5DOM they are “real” decodes. Note that the azimuth values reported by WSPRnet here are the reverse azimuth from W3SZ’s perspective:
| Timestamp | Call | MHz | SNR | Drift | Grid | Pwr | Reporter | RGrid | km | az |
|---|---|---|---|---|---|---|---|---|---|---|
| 2018-03-15 02:50 | P57SCV | 0.475703 | -23 | 0 | ED90 | 0.2 | W3SZ | FN20ag | 11106 | 4 |
| 2018-03-13 08:26 | P60PCD | 0.475595 | -26 | -1 | FF43 | 0.2 | W3SZ | FN20ag | 8554 | 356 |
| 2018-03-09 01:40 | EA5DOM | 0.475607 | -26 | 0 | IM98xn | 1 | W3SZ | FN20ag | 6312 | 298 |
| 2018-03-13 10:40 | W7IUV | 0.475692 | -28 | 0 | DN07dg | 1 | W3SZ | FN20ag | 3549 | 86 |
| 2018-03-12 04:28 | ZF1EJ | 0.475695 | -20 | 0 | EK99ig | 2 | W3SZ | FN20ag | 2390 | 11 |
| 2018-03-14 01:58 | WA4YHC | 0.475640 | -22 | 0 | EL44 | 0.2 | W3SZ | FN20ag | 2249 | 35 |
| 2018-03-16 09:06 | KE7A | 0.475779 | -27 | -1 | EM12kx | 1 | W3SZ | FN20ag | 2049 | 61 |
| 2018-03-16 10:12 | W5OXC | 0.475650 | -28 | 4 | EM13mm | 5 | W3SZ | FN20ag | 2006 | 62 |
| 2018-03-11 06:08 | K5DNL | 0.475709 | -25 | 0 | EM15lj | 5 | W3SZ | FN20ag | 1924 | 67 |
| 2018-03-13 10:40 | K1UTI | 0.475795 | -25 | 3 | EL86wx | 0.5 | W3SZ | FN20ag | 1583 | 19 |
| 2018-03-17 02:44 | N4WLO | 0.475676 | -25 | 0 | EM50uo | 0.1 | W3SZ | FN20ag | 1547 | 43 |
| 2018-03-16 10:32 | W0DJK | 0.475700 | -29 | 0 | EN34gh | 5 | W3SZ | FN20ag | 1505 | 101 |
| 2018-03-16 10:12 | W4BCX | 0.475625 | -9 | 0 | EL98pd | 5 | W3SZ | FN20ag | 1417 | 17 |
| 2018-03-16 09:50 | K2BLA | 0.475692 | -14 | 0 | EL99hb | 2 | W3SZ | FN20ag | 1340 | 20 |
| 2018-03-16 10:12 | WD8DAS | 0.475719 | -27 | 0 | EN52hx | 1 | W3SZ | FN20ag | 1154 | 101 |
| 2018-03-16 10:12 | VE9GJ | 0.475701 | -18 | 1 | FN77ha | 2 | W3SZ | FN20ag | 1133 | 232 |
| 2018-03-14 01:14 | WA4SZE | 0.475771 | -29 | 0 | EM65 | 0.2 | W3SZ | FN20ag | 1108 | 58 |
| 2018-03-12 00:28 | W9XA | 0.475795 | -20 | 0 | EN51uu | 0.2 | W3SZ | FN20ag | 1048 | 96 |
| 2018-03-09 01:40 | KA9OKH | 0.475648 | -26 | 0 | EM67fx | 10 | W3SZ | FN20ag | 1030 | 72 |
| 2018-03-14 23:56 | WA9CGZ | 0.475619 | -26 | 0 | EN61ch | 1 | W3SZ | FN20ag | 1002 | 93 |
| 2018-03-13 10:40 | KU4XR | 0.475769 | -13 | 0 | EM75xr | 2 | W3SZ | FN20ag | 869 | 52 |
| 2018-03-11 08:02 | N1DAY | 0.475743 | -14 | -1 | EM85sg | 5 | W3SZ | FN20ag | 797 | 44 |
| 2018-03-11 08:02 | KC4SIT | 0.475609 | -7 | 0 | EM85tg | 5 | W3SZ | FN20ag | 792 | 43 |
| 2018-03-13 05:46 | K9KFR | 0.475681 | -18 | 0 | EN71 | 0.5 | W3SZ | FN20ag | 775 | 97 |
| 2018-03-11 23:30 | KN8DMK | 0.475651 | -28 | 0 | EM89oo | 2 | W3SZ | FN20ag | 587 | 81 |
| 2018-03-13 09:22 | VE3EFF | 0.475742 | -10 | 0 | FN15rj | 1 | W3SZ | FN20ag | 572 | 175 |
| 2018-03-11 06:08 | VE3CIQ | 0.475767 | -18 | 0 | FN15wd | 1 | W3SZ | FN20ag | 542 | 179 |
| 2018-03-11 04:12 | W1IR | 0.475788 | -6 | 0 | FN34lp | 5 | W3SZ | FN20ag | 542 | 207 |
| 2018-03-11 03:24 | W4KZK | 0.475690 | -16 | 0 | EM97xe | 0.2 | W3SZ | FN20ag | 493 | 45 |
| 2018-03-11 03:24 | AA1A | 0.475684 | -18 | 0 | FN42pb | 1 | W3SZ | FN20ag | 482 | 247 |
| 2018-03-16 21:56 | WA3ETD | 0.475721 | -27 | 0 | FN33lq | 2 | W3SZ | FN20ag | 450 | 213 |
| 2018-03-11 03:24 | W1XP | 0.475666 | -19 | 0 | FN42fo | 1 | W3SZ | FN20ag | 450 | 236 |
| 2018-03-10 23:02 | WA1OJN | 0.475715 | -1 | 0 | FN32pi | 5 | W3SZ | FN20ag | 357 | 231 |
| 2018-03-11 03:44 | AE2EA | 0.475764 | -17 | 0 | FN12fr | 2 | W3SZ | FN20ag | 303 | 154 |
| 2018-03-17 02:34 | KA1AL | 0.475704 | -22 | 0 | FN31gm | 0.02 | W3SZ | FN20ag | 252 | 237 |
| 2018-03-12 06:10 | N2EIK | 0.475699 | -24 | 0 | FN21 | 1 | W3SZ | FN20ag | 155 | 210 |
| 2018-03-16 13:12 | W3LPL | 0.475742 | +1 | 0 | FM19lg | 5 | W3SZ | FN20ag | 145 | 39 |
| 2018-03-12 02:36 | N3FL | 0.475755 | -11 | 0 | FM19ua | 0.02 | W3SZ | FN20ag | 142 | 11 |
| 2018-03-16 13:12 | WB3AVN | 0.475670 | -11 | -2 | FM19og | 5 | W3SZ | FN20ag | 132 | 32 |
| 2018-03-11 21:26 | W3HMS | 0.475628 | -27 | -2 | FN10mf | 0.05 | W3SZ | FN20ag | 85 | 87 |
| 2018-03-09 16:50 | K3MF | 0.475797 | +14 | 0 | FM19sr | 2 | W3SZ | FN20ag | 74 | 35 |
We will end this blog with two interesting tidbits regarding my Inverted L transmit antenna. You will recall that based on the variometer settings I estimated that the inductance needed to match the antenna was approximately 700 uH. And in the previous blog I used the 472kHz.org website antenna simulator to estimate the inductance required to match the antenna. That calculator estimated that the antenna’s capacitance was 151 pF and that 745 uH would be required to match the antenna. On Wednesday I measured the capacitance of the antenna with no matching attached using my BK Precision 875B RLC meter and obtained a value of 157 pF. At resonance (475 kHz) the impedance of the antenna is purely resistive, with no reactance. Thus, at resonance Xc – Xl = 0.
So,
2 x Pi x f x L – 1 / (2 x Pi x f x C) = 0
Solving for L,
L = 1 / (4 x Pi^2 x f^2 x C)
where
f = frequency in Hz
L = inductance in Henries
C = capacitance in Farads
Plugging in
f = 475000
C = 157 x 10^(-12) Farads
gives a value of 715 uH as the inductance value required to match the antenna. So the prior estimates of 700 and 745 uH were pretty darn close to the value of 715 uH obtained by measurement of the capacitance of the antenna and the calculations shown above!
The second interesting tidbit is that my inverted L, before I moved the vertical element further away from my tower, was extremely sensitive to small changes in antenna position caused by shifting breezes. This is not surprising; with the vertical element of the Inverted L within 2 feet or so of the vertical tower there is significant capacitance added to the inverted L’s Xc, and as the vertical section moves closer to and farther away from the tower this capacitance value will change.
My intuition was that this variation in capacitance was likely greater than any variation caused by motion of the much longer horizontal section of the antenna, so I felt that if I could move the vertical section of the inverted L further away from the tower and “tighten up” the vertical section of the Inverted L so that it would swing less in the breeze, that this would reduce the variation in capacitance and thus reduce the changes in antenna tuning during windy periods. This proved to be the case.
Watch the SWR and Power changing with time on the video shown below that was taken before I moved the vertical section of the Inverted L further from the tower and tightened up this vertical section so that, being more taut, its excursion would be reduced and thus the variation in antenna capacitance would be reduced, thus reducing the changes in Xc and antenna matching.
Although the SWR and power readings shown in this video are both incorrect, as the Nye tuner was not designed for these frequencies, they do give relative readings. When the Nye antenna tuner’s SWR meter shows 2:1, the actual SWR as indicated by my miniVNA Pro is 1.05:1. And the RF power reading has proven to be double the actual value over a wide range of RF power values.
The video stops suddenly because I was concerned about the safety of the transmitter with these wide excursions in SWR and power. Even though the amplifier is supposed to be safe and protected from damage even with open and shorted loads, I did not want to risk the small possibility of damaging the amplifier due to sub-optimal loading conditions and excessive reflected power. Although it is nice to have protection circuits, it is even better (and definitely wiser) not to create circumstances where you have to rely on them.
The next thing that I need to do is to improve my transmit antenna efficiency, which is currently about 0.00291. With this efficiency, my 100 watts TPO gives me only 291 milliwatts EIRP or about 5.8% of the maximum permitted EIRP. All other factors being equal, just raising my EIRP from its current value to 5 watts would increase my signal strength by 10 x log(5/0.291) = 12.4 dB.
In the process of improving my transmit antenna system, I will also upgrade my variometer (actually, replace it with a homebrew variometer that can handle higher powers and be remotely tuned) so that I can increase my power from 100 watts to 400 watts and remotely adjust the antenna matching if need be as the antenna resonant frequency changes due to changes in environmental conditions.
Of course, if I achieve a high-enough antenna efficiency, a TPO of less than 400 watts will give me 5 watts EIRP. With my current antenna efficiency, I would need 1719 watts TPO to achieve 5 watts EIRP. So there is a lot to be gained by improving my transmit antenna efficiency.
Once that is done and I can be heard by everyone I hear, then it will be time to improve the performance of my receive antenna, which is still the 500 foot BOG (Beverage On the Ground). I have been looking at adding additional receive antennas that would be complementary to my 500 foot BOG. W8JI has an excellent website filled with information on antennas for the low bands. The index page is here. W8JI’s index page for low-noise receiving antennas is here. There is a list of antenna types at the top of this page and clicking on one of the links in that page will take you to the appropriate antenna type. I found Tom’s page on Magnetic Receiving Loops interesting. He basically says that what many people think about the way in which magnetic loops operate is incorrect, and that the construction method used by many folks is wrong.
73,
Roger W3SZ