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Current Operating Frequency and Mode

OFF AIR for storms, probably for much of the week if the forecast holds

Average to below average domestic propagation with relatively high noise in many areas of North America as geomagnetic conditions return to quiet levels; VK4YB presents, ”The VK4YB 630m ‘Bottom Hat’ Vertical Antenna”

– Posted in: 630 Meter Daily Reports, 630 Meters

The details for May 31, 2016 can be viewed here.

IMPORTANT REMINDER: Neither 630-meters nor 2200-meters are open to amateurs in the US yet.  Please continue to be patient and let the FCC finish their processes.  Click here to view the proposed “considerate operators” frequency usage guide for 630-meters under Part-97 rules that was developed with the input of active band users.

There were a lot of storms around North America and it was relatively noisy, making domestic openings challenging to realize.  Long-haul paths were not much better aside from a couple of openings between North America and Oceania.

11-hour North American lightning summary


Geomagnetic conditions are once again quiet with a Bz that is pointing to the North and solar wind velocities averaging near 385 km/s.  DST values have generally leveled out but continue in negative territory.  Luis, EA5DOM, reminded us that the strongest space weather event ever recorded occurred fifty years ago in 1967. It resulted in a DST of -387nT and the Kp was 9 for 6 hours. Flare flux was 8000 SFU at 2800 MHz.  A talk by Dolores J. Knipp of the University of Colorado on the subject of this event was given at the American Meteorological Society’s 14th Conference on Space Weather and can be heard here.





Joe, K9MRI / WI2XUL, reported that he was QRV on 476 kHz CW for a bit at 0251z for testing.

Al, K2BLA / WI2XBV, reported that he operated for a bit this morning through moderate QRN conditions, decoding three WSPR stations.

Doug, K4LY / WH2XZO, reported that he experienced “Some relief from QRN.  Seventeen, most in a long time, decoded XZO  who decoded five.  Some signals that had been in the -20’s dipped into the teens for the first time in what seems like weeks.”

Larry, W7IUV / WH2XGP, reported poor conditions.  He provided reports for five WSPR stations and he received reports from nineteen unique stations.

WH2XGP 24-hour WSPR activity (courtesy NI7J)


Neil, W0YSE/7 / WG2XSV, reported that he decoded three WSPR stations including WI2XBQ, WH2XXP, and WH2XGP.

Roger, VK4YB, reported that “conditions were a carbon copy of yesterday. With the exception that there will be no reports from Japan owing to heavy thunder storms over the mainland.”  Roger shared two-way reports with VK4YB.

Mike, WA3TTS, reported, “…Perhaps another evening of slow improvement in MF propagation… 7 stations decoded. NE EWE on SS to 0330 and then NW EWE until SR.  I should have listened SW for awhile as I might have been able to pick up ZF1EJ or WI2XRM….I will try that strategy this upcoming evening…”  Mike provided the following statistics:

Mike added:

“Also decoded WH2XND 59 times overnight on 2200m. SNRs were high overnight t  -25 best to -33 decode limit.  Dual band receive with hybrid splitter on output of LF/MF converter….

QSL received from VK4YB in snail mail yesterday for April 25, 2017 630m Equinox decode.  Many thanks for the card and your comments Roger !”

Trans-Pacific report details, excluding KL7 and KH6, can be viewed here.

Ward, K7PO / WH2XXP, received reports from thirty unique stations including ZL2AFP.  While the session was hopeful at the beginning, Ward indicates that it turned out to be disappointing and even a little worse than the previous night.

WH2XXP 24-hour WSPR activity (courtesy NI7J)


I skipped CW during this session because it was obviously noisy, starting WSPR just after local sunset.  The band was moderately slow to produce results until it was totally dark, even on shorter hops but this is normal band behavior for this time of year.  As previously stated, three hours after darkness represents the beginning of the best openings during the Summer months.  At 17% duty cycle, transmit and receive numbers were balanced but suggest overall band conditions that were in distress.  No surprise there.  My transmission report details can be viewed here and my reception report details can be viewed here.

WG2XIQ 24-hour WSPR activity


Regional and continental WSPR breakdowns follow:

North American 24-hour WSPR activity


European 24-hour WSPR activity


Japanese 24-hour WSPR activity


Oceania 24-hour WSPR activity


Eden, ZF1EJ, provided reports for three WSPR stations and he was reported by five unique stations.

ZF1EJ 24-hour WSPR activity


Laurence, KL7L / WE2XPQ, indicates that the ionosphere was a bit better with West coast and Pacific reports.  He provided reports for three WSPR stations and he was reported by four unique stations.  He shared two-way reports with WH2XCR.

WE2XPQ 24-hour WSPR activity


Merv, K9FD/KH6 / WH2XCR, provided reports for VK3HP and shared two-way reports with VK4YB.  He received reports from VK2XGJ and ZL2AFP.  Merv’s DX report details can be viewed here.

WH2XCR 24-hour WSPR activity


Roger, VK4YB, presents, “The VK4YB 630m “Bottom Hat” Vertical Antenna”:

“A very good antenna on 630m would be a 500ft vertical. If you have one of those, read no further. I am taking 500ft as being near enough to a quarter wavelength for my calculations. Next taxi off the rank would be a fully hatted vertical. By fully hatted, I mean with enough wire up at the top of the vertical section to bring the vertical to quarter wave resonance without the need for a base loading coil. For a modest height of say 50 to 100ft, this means a lot of top wires and supports in the top hat. Needless to say, it takes a huge effort to get that amount of wire in the air and keep it there in high winds.

Next best thing is a full sized inverted L. Here the top hat is replaced by a single horizontal loading wire. With our typical 50 to 100ft vertical section, this still requires at least another 400ft of wire up high and quite a lot of real estate to fit it in.

If none of those options are practical, the next compromise would seem to be the short vertical, brought to resonance with a loading coil. I have an inherent dislike of loading coils. But it is not because they are difficult to wind or adjust, nor is it because they have losses. It is because they are replacing the best part of the antenna, the part carrying the high current, and leaving only the low
current tail end.

So is there another alternative to the three antennas mentioned above which enables us to retain the maximum current section of the vertical but relieve us of the burdensome top hat?

I’ve come up with an idea I call the “Bottom Hat” vertical. It is the poor man’s inverted L. Instead of running the 400ft top section out to the full length at thefull height, I let it drop to ground and run the rest at 6ft above the ground. The disadvantage of this method is that it creates a second vertical in which the current is in anti-phase to the first vertical. The radiation from the two verticals will tend to cancel each other. But the cancellation is nowhere near as bad as you may think. I have roughly calculated the RF current at points A, B, C and D in the diagram below. The radiating ability of a vertical is very much dependent on the product of current in the vertical multiplied by the length of the vertical usually stated in units of degree-Amperes. In this case, the vertical is 90ft or 16.2 degrees at 475 kHz. The average current is 0.98 A, so the all important product is 15.9 deg-A. The corresponding number for the second (West) vertical is 5.4 deg-A. Broadside to the array, there will be 10.4 deg-A working in your favour. End-fire there will be 11.6 deg-A, because the separation of the verticals by one eighth of a wavelength means less than full cancellation.

I have checked the one amp into the antenna is correct using an RF ammeter.  The transverter shows 50 watts output and an SWR of 1:1. I am not happy about the 1:1 SWR, because it shows the antenna as having 50 ohms input impedance. It should be much less and the difference is made up of ground losses, which are high. However the feed arrangement couldn’t be simpler. The vertical just plugs straight into the centre pin of the SO239 output socket. The case of the transverter is connected to the station ground via other cables. I trimmed the length of the bottom hat wires to bring the center of the band to 1:1 SWR. At the band edges the SWR only rises to about 1.2:1. Rain or wind does not affect the SWR.

My existing NE and NNW beam antennas out-perform this bottom hat antenna along their main lobes, but in all other directions the bottom hat is superior. On the second night of operation, its WSPR beacon signal was decoded by ZF1EJ at a distance of 14,452 km on a bearing of 87 deg, nearly due East of Brisbane.”

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