Reviewing my WSPR report from overnight its obvious that the band was very open and stations that were further away from the noise sources were able to take advantage. There were many single digit S/N reports and this seems to be a theme repeated by many stations based on summaries received from operators this morning.
Solar wind has been a bit elevated during this session but otherwise the geomagnetic field seems to be behaving itself:
John, WA3ETD / WG2XKA, has been fighting weather and wildlife this week and shares these details:
Neil, W0YSE/7 / WG2XSV, reports that he added a radial under the house and it seems to have made a difference. Who can argue with RF current flow? Additional radials may be forthcoming.
Doug, K4LY / WH2XZO, provided a nice report after sunrise yesterday morning about on-going daylight reports of his signal in the Cayman Islands:
Ron, NI7J / WH2XND, had another session of trans-Pacific reports from stations in Australia, this time adding David, VK2DDI, to the mix. Its been long theorized that the seasonal transition openings between North America and Oceania often seen in September should also be seen in March but this year is the first time it has been observed with any regularity. Ron also notes forty unique decodes of his signal and he decoded ten unique stations from Arizona, in spite of the high noise levels.
Hideo, JH3XCU, reports that the JARL awards that were mentioned yesterday and in previous reports are only available for amateur radio QSO’s and SWL’s. This information came after an inquiry about QSO’s that I had completed under my Part-5 call sign. While I could submit SWL reports of stations received as an amateur operator, I cannot submit two-way QSO’s until the band is administered under Part-97, which should not be long. You can be certain that once the band opens, I will be making a mad dash to get the first certificate in the US. I hope others will join in the mayhem for a little friendly competition! Thanks to JH3XCU for the details and thanks to the JARL for sponsoring an award on the band. I look forward to the ARRL and CQ magazine doing the same.
Joe, NU6O / WI2XBV, is interested in completing a “diversity QSO” using WSQ2. Please contact Joe on the ON4KST chat/logger for details on this very interesting endeavour. Like me and others, Joe really enjoys making two-way QSO’s and getting out of the “WSPR-rut”. While WSPR is a very useful tool for evaluating band conditions in real time, there is nothing like making real exchanges with another operator. While we are on the precipice of persistent noisy band conditions, consider scheduling a two-way QSO with a station, even if they are only “down the street” and communicate. It may change the way you look at the band…
Ken, K5DNL / WG2XXM, reports that he only decoded six stations due to high QRN levels but was decoded by forty unique stations.
WSPR activity was high, with 81 MF WSPR stations observed at 0415z. Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African path, however, ZS1JEN was present during the session. UA0SNV was also present but had no reports in the WSPRnet database.
WD2XSH/17 reported DK7FC during this session on the trans-Atlantic path.
It was a noisy night in the Cayman’s but Eden, ZF1EJ, and Roger, ZF1RC, provided a number of reports for stations around the US.
In Alaska, Laurence, KL7L / WE2XPQ, received stations along the western coast of North America, into the American southwest and Pacific:
In Hawaii, Merv, K9FD/KH6 / WH2XCR, had a great night, particularly with stations in Australia. The noisy conditions on the mainland US didn’t sour the fun, with reports into and out of the central US.
In Australia, Phil, VK3ELV, and Roger, VK4YB, continue to receive reports from WH2XCR and Phil had another session of reports from Japan.
Jim, W5EST, presents a “DIALOG WITH JOE WI2XBQ ON RF ANTENNA BASE CURRENT MEASUREMENT”:
“Joe WI2XBQ NU6O shared perspectives from his experience with RF current measurement.
Joe WI2XBQ: Use an AC-powered variacto calibrate a thermal RF ammeter, good from DC to 50 Mhz. The current is measured with variac driving an amps-measuring DVM (digital VOM) in series with the RF meter. Run up the variac to full scale reading. Compare it to the DVM. We tested and calibrated meters this way for AM broadcast use. Put a filament transformer in between if you need more AC current than the 5A the variac may give.
Jim W5EST: And you can also buy the sensor element and homebrew the rest, I suppose. https://www.surplussales.com/Meters/MtrRF-amps.html . Still, calibration is vital like you say. Is there anything to be careful of?
Joe WI2XBQ: Because deflection of the meter is proportional to the amount of heat in the heater wire, which is proportional to the square of the current passing through it, the thermo-ammeter has a square-law scale. A thermal meter at the base of a very short vertical doesn’t read accurately when its heater element resistance approximates radiation resistance. If inserting a thermal meter detunes the antenna, the reading isn’t accurate.
Jim W5EST: How can we get better accuracy?
Joe WI2XBQ: Current transformer based RF metering is the norm now, but the variac calibration method doesn’t work for them. Instead, use a calibrated thermal meter as a transfer standard to test a current transformer meter at operating frequency.
Jim W5EST: Current transformer RF metering, that’s like the Jan. 20 blog about Pat WD2XSH/6, W5THT http://500kc.com/about_stations/6/index.htm . How would you recommend MF/LF folks do transfer standard calibration of a current transformer RF meter from a thermal RF ammeter?
Joe WI2XBQ: Hook the calibrated thermal RF ammeter with your RF current meter’s current transformer in series to a dummy load. Introduce RF drive and run up the RF drive to the meters and dummy load. Use the readings from the thermal RF ammeter to calibrate the current transformer RF meter. Don’t calibrate a current transformer meter at the antenna base. Install it there after calibration on the dummy load.
Jim W5EST: Like the musicians might say, “Does your theme have variations?”
Joe WI2XBQ: Instead of a thermal ammeter reference, you can use a calibrated RF wattmeter to measure forward power into the dummy load since it’s 1:1 SWR. RF current is I = sqrt(Power/Rdummy). Also, compensation of diode detectors in a current transformer RF ammeter benefits meter linearity and calibration. Transient suppression, see: http://www.deltaelectronics.com/data/tca1data.htm
Jim W5EST: I see our dialog parallels John WE2XGR/3 W1TAG at http://www.w1tag.com/RFA.htm .
5A current transformer RF ammeter: http://www.spirat.com.au/vk5zvs/pic53.htm . Full-wave diodes:
Jim W5EST: Say, Joe, what if somebody lacks a variac or a wattmeter or a second ammeter.
Can people just omit using an RF ammeter entirely? With ATU disconnected, measure the system resistance Rsystem between antenna base and ground as the real part of the antenna impedance the analyzer tells. Suppose analyzer says impedance is 25 – j1000. Then Rsystem =25Ω. Reconnect ATU and adjust it for 1:1 SWR. Drive ATU /antenna with TX power output TPO. Calculate antenna base current I = sqrt(TPO/Rsystem). What’s your opinion? Any practical tips how to do that?
Joe WI2XBQ: One big reason to measure RF antenna base current is to estimate EIRP. Hams have worked to measure field strength, but it’s hard to get a calibrated FS meter up and running inexpensively. For an industry standard field strength meter, see: http://www.pi-usa.com/pdf/fim22-41.pdf See a NIST paper on field strength meter calibration: http://www.nist.gov/calibrations/upload/im-34-4b.pdf The procedure for calibrating loops (p. 492 ff) uses a thermal ammeter calibrated at DC. I think an amateur FS meter could be constructed in light of the NBS calibration setup. For John W1TAG’s extensive work on FSM, see http://www.w1tag.com/LF_FSM.htm
Jim W5EST: So what should we do?
Joe WI2XBQ: Face it: Compared to EIRP, base current is a relative number. If we could accurately measure or derive the actual radiation resistance of the antenna, then the base current reading would be meaningful on the way to EIRP. In amateur systems, unlike professional MF systems, you have nearly all ohmic loss and very low radiation resistance. So, measure the power going into the tuning unit ATU vs. RF antenna base current. Less base current means more ohmic system loss. The loading coil is a big loss resistance in the system so minimize losses in the coil. It may be cheaper than putting copper in the ground or adding antenna height.
CLOSING: Thanks, Joe! We appreciate blog contributions from all readers!”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD <at> gmail dot (com)!