Radio: it's not just a hobby, it's a way of life

Current Operating Frequency and Mode

OFF AIR but will be QRV on CW somewhere between 472.5 kHz and 475 kHz after dark

SCHEDULED ACTIVITY: CQ 474.5 kHz CW by 1030z through sunrise most days, WX permitting

Domestic propagation was good while long-haul openings were not as impressive as recent sessions; QRN exits the central US and moves to the East coast; JA path opens for Alaska and Hawaii

– Posted in: 630 Meter Daily Reports, 630 Meters

Band conditions were much improved from the previous session, at least for the central and southern US.  Thunderstorms increased in the Mid-Atlantic and Northeast, however, forcing some stations, like WG2XKA at 0100z, to QRT for the night.  Even so propagation around North America was pretty good, supporting transcontinental paths that have been suppressed  over the previous few session.  While the trans-Pacific path presented a few openings, it was down considerably from previous sessions, allowing only higher ERP’s to “make it across” and even those reports were down.  There were no trans-Atlantic reports.  The path to JA was open from Alaska and Hawaii.  This was a session that probably had something for most stations.


11-hour North American lightning summary


It is presumed that long haul propagation has been impacted by the forecast G1 storm conditions that are expected to take hold sometime today.  While the Kp has not yet shown significant increases this morning, solar wind is approaching 400 km/s, up from near 300 km/s in the previous session and significant decreases have been observed with DST values.  The Bz is pointing to the North as elevated proton levels have been observed:







Trans-Pacific openings were present but not as robust as previous session, at least those openings that were also trans-Equatorial in nature.  Roger, VK4YB, labelled this morning as a “Code-3”, diverting Steve, VE7SL, back to bed.  Roger, did not expect much and had no reports of his signal at the time but has since registered a report at WH2XGP in Washington state, who continues to operator “receive-only” as he repairs his amplifier.  Roger submitted the following statistics followed by his report details from WH2XGP:

“Spots 4*WG2XXM (-24) 17*WH2XXP (-21) 20*WH2XCR (-15) Decoded by WH2XGP WH2XCR”


VK4YB, as reported by WH2XGP


Ward, K7PO / WH2XXP, reported decodes from 46 unique stations, including five VK stations:


WH2XXP session WSPR activity (courtesy NI7J)



WH2XXP, as reported by EJTSWL



WH2XXP, as reported by VK2DDI



WH2XXP, as reported by VK2XGJ



WH2XXP, as reported by VK5ABN



WH2XXP, as reported by VK4YB


Ken, K5DNL / WG2XXM, reports that he decoded eight WSPR stations and was decoded by 44 unique stations, including four reports from VK4YB.  He reported low QRN and decodes of WH2XXP at +10 dB S/N.  Ken also reports, “Had 6 decodes fm KL7L best -14.”  Thunderstorms should be less prominent in the near term in Oklahoma.


WG2XXM, as reported by VK4YB


Phil, VE3CIQ, reports, “I made one transmission to XGP, and hit all the usuals, so not too bad from here.”

Steve, VE7SL, report, “GM … Hrd 11, hrd by 29 … good E-W condx w/ 32 spots from VE3IQB, some at CW levels”

Phil, VK3ELV, had a number of late reports from JH3XCU during the previous session, presented below:


VK3ELV, as reported by JH3XCU


Rick, W7RNB / WI2XJQ, reported that he decoded eight WSPR stations including first time reports at VE3IQB.   Rick was decoded by thirteen unique stations:



Doug, K4LY / WH2XZO, completed additional antenna improvements during the session and reported lower QRN:

“A little less noisy last night, and path to VE7SL was open. Heard 8 and heard by 27.  It seemed to be the best night of the season so far here in SC.  Four stations, inc WH2XZO with plus SNRs.  I made slight improvements by cutting back some of the jungle that had grown up near the TX antenna, parting out my old 4″ diameter by 15″ quarter inch flexible copper pipe loading coil for a similar 6″ D by 7” coil, and raising the RX loop from 10′ to 15′ above ground.

With the smaller inductance, but higher Q, 6″ D by 7″ copper coil, I needed more turns on the much lower Q Bud coil which sits below the copper coil and which I tap for lowest SWR.  I’m going to clean up and  “rewind” the old, weathered coil which I used on LOWFER frequencies in the 1990’s and maybe replace the Bud coil with it.”

Neil, W0YSE/7 / WG2XSV, made it deep in the heart of Texas and submitted these statistics:


Neil also reported that he had a JT9 decode from Laurence, KL7L / WE2XPQ.  Hopefully there is a two-way QSO in the near future:


WE2XPQ CQ in JT9, as reported by WG2XSV


WSPR participation was high during the evening, with more than 80 unique WSPR stations observed.  W1GJM was present in addition to our old friend Steve, W6SJP, who recently returned from living in China, now settling in Florida.  Welcome aboard!

Regional and continental WPSR breakdowns follow:


North American 24-hour WSPR activity



European 24-hour WSPR activity



Australian 24-hour WSPR activity



Japanese 24-hour WSPR activity


There were no reports from the trans-Atlantic or trans-African paths.

Eden, ZF1EJ, reported VE7SL during this session, taking advantage of quiet conditions across central and western North America:


ZF1EJ 24-hour WSPR activity



ZF1EJ/1 24-hour WSPR activity


Laurence, KL7L / WE2XPQ, had plenty of CW-level reports of WH2XCR in addition to being decoded at JE1JDL and along the West coast of North America.  Laurence had a very strong session in the northern hemisphere, particularly given that longer haul paths were compromised during this session:


WE2XPQ 24-hour WSPR activity



WE2XPQ, as reported by JE1JDL



WH2XCR, as reported by WE2XPQ



KL7L 24-hour WSPR activity



WH2XCR, as reported by KL7L


Merv, K9FD/KH6 / WH2XCR, covered a lot of ground during this session once again in spite of fewer reports from the trans-Equatorial path to VK.  Reports from VK4YB ended several minutes prior to sunrise:


WH2XCR 24-hour WSPR activity



WH2XCR, as reported by JA1NQI-2



VK4YB, as reported by WH2XCR



WH2XCR, as reported by VK4YB



WH2XCR, as reported by EJTSWL



WH2XCR, as reported by VK2DDI



WH2XCR, as reported by VK2NP



WH2XCR, as reported by VK2XGJ



WH2XCR, as reported by VK5ABN



Jim, W5EST, talks magnetic loops and introduces “THE DG0KW MAGNETIC LOOP CALCULATOR”:

“Hams can receive 630m with Verticals, shack-shorted dipoles, E-probes, and magnetic loops of various types. For one of the loop types there’s a loop calculator authored by Klaus DG0KW. Go to: http://www.i1wqrlinkradio.com/antype/ch9/chiave143.htm

Scroll to bottom of the web page where the Download section provides documentation. The very bottom link “Description” is an English translation describing a resonated loop with coax pickup.

Also among these Download links, click on Magnet-Loop-Rechner (magnetic loop reckoner/calculator) to specifically download the calculator software (4/20/2016 V.1.1.1). Then double-click the Application file among the files that download. Mouse-drag the red & yellow icon MagnetLoop out onto your PC desktop and double-click to open it.

In the illustration I’ve entered an example into the magnetic loop antenna calculator’s windows. The main display window at left handles the main large loop. Click at top on “Optionen” and then click “Sprache” and select your choice of German, French, or English legending.  I’ve opened a second window at right that opens from the first window to estimate an inner coupling loop made of coax.

Using English, I entered values in the Loop – Specifications upper entry blanks to specify a 2.5m diameter, circular, Cu (copper) main loop. This calculator is metric, so it uses meters for the loop diameter.  The calculator accepts your entries in either decimal point or decimal comma notation as is customary for your country. https://en.wikipedia.org/wiki/Decimal_mark

A meter is a little more than a yard, and 3 meters is roughly 10 feet.  To convert dimensions or spaces between meters and feet, use

Space(ft) = 3.281 x Space(m).           Space(m) = 0.3048 x Space(ft).

Conveniently convert AWG wire gauge numbers to specify your intended conductor diameter (mm), and interpret vice-versa. Note popular #18, #16, #14, #12 wire sizes correspond to 1.024, 1.291, 1.628, 2.053 mm diameters.  Or use a web calculator such as: http://www.rapidtables.com/calc/wire/awg-to-mm.htm .

“Length”: Coil lengths ¼, ½ , ¾ , 1, 1½ , 2, 2½ , 3” in inches correspond in millimeters to 6.35, 12.7, 19.1, 25.4, 38.1, 50.8, 63.5, 76.2 mm.  Even with many turns, the main loop has a short coil length compared to its diameter.

If you enter a number of main loop turns as 2 or more, you get a minimum coil length (or width, some would say). The more turns, the more is the minimum coil length. I think the calculator figures that minimum by multiplying wire diameter by one-less-number of turns, and then includes some more spacing to keep the turns capacitance low. You can re-specify the coil length greater than the minimum as you wish.

For a calculating example, I chose to calculate this 2.5 meter (~8’) diameter circular loop using #16 (1.291 mm) wire diameter with 5 turns, and 1.5” (38.1mm) coil length.

For operating frequency, halfway down the DG0KW main loop calculator window, I entered 0.475 MHz.   I specified Tx-Power 100 watts to see what capacitor voltage—about 3700V!–that power would produce.  However, I think most 630m ops would set up this antenna only for receive and would employ a top-loaded vertical for 630m transmit instead.

Showtime! I clicked the “Calculate: Loop” button at bottom left and got these results up above in window middle:

Inductance estimate came out 167uH independent of frequency.  That’s in the ballpark compared to 207uH calculated from this web site http://hamwaves.com/antennas/inductance.html

Capacitance at LC resonance corresponds to this 475KHz-specific formula:

C = 1000pF/(9L(mH)) = 1000pF/9×0.167 = 663pF.

The main loop resonating capacitance at 475KHz estimated by the calculator is ~600 pF (671-78pF self-capacitance). The value will depend on frequency if you want to resonate for another band.  You would connect a capacitor and/or variable capacitor to resonate the  loop.

The narrow bandwidth 1.74 KHz for my antenna example corresponds to high calculated Q=273, close to the standard definition: Q=2πfL/R.

1.754Ω copper resistance is calculated at 630m and differs for other frequencies: I surmise skin effect is included. Again the estimate is in the ballpark compared to 1.85Ω from:


At 630m it calculates 0.12Ω radiation resistance. Total resistance R = 0.12Ω +1.75 Ω.  Not discussed here: Efficiency % and dBd gain (relative to free space dipole) estimates, these are more pertinent to transmit use.

Now click the bottom middle Calculate button named “Coupling Loop.” The calculator proposes a ratio 4 to 5 that roughly relates to main loop diameter ratioed to coupling loop diameter. The proposed ratio increases from about 4 to about 5 as loop height increases depending on the  location you select from top menu. This Coupling Loop window’sCalculate” button then calculates the circumference of the coupling loop coax as 2.09m for a roof-mounted loop and roughly 64cm “Lka” that resembles its diameter dimension.

I surmise the size of this coupling loop isn’t too critical, 20-50% the diameter of the main loop. The coupling loop needs to be big enough to couple in signal, and small enough not to load down the resonant main loop too much.  On receive, the impedance match to 50Ω coax isn’t too critical. If used for transmit, you do care about the impedance match because of SWR.

The 50Ω coax from the shack is connected to a 1:1 balun outdoors at the coupling loop. Its connection diagram is found at p. 11 of the Description document at http://www.i1wqrlinkradio.com/antype/ch9/chiave143.htm

The DG0KW mag loop calculator calculates loops for operating frequencies that can be set at least as low as 10 KHz. ELF frequencies and various dimensional specifications (such as too-small turn spacing inconsistent with turn diameter) will receive no calculation and cause a “Value unreal!” message instead.

The real-life loop antenna you build in its actual environment will depart from whatever a loop calculator might estimate. So be ready to adjust and work with the antenna until it resonates at 630m and receives properly.

This calculator handles the electrical/RF side of the things, which means all-important physical construction matters and rotatability remain up to you.  See other web sites like http://members.shaw.ca/ve7sl/loop.html  and the standard antenna books.

Do you have another mag loop calculator you like, or another loop design?  E-mail us so we can blog the information!”


Click to enlarge


Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).