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 Previous: Youth@HamRadio.Fun: K2BSA--Promoting Amateur Radio to 40,000 |  Next: AO-40 Achieves a New Orbit |
NEWINGTON, CT, Jul 5, 2001--A signal transmitted on 184 kHz from ZL6QH--the Wellington, New Zealand, Amateur Radio Club's Quartz Hill station--has spanned the Pacific. The transmission was part of a series of announced transpacific tests. Its reception on June 30 by Steve McDonald, VE7SL, of British Columbia, Canada, paves the way for an eventual two-way Amateur Radio contact.
"A claim is made for the confirmed reception of ZL6QH by VE7SL, on 184.4 kHz, over a path of 11,709 km," said Bob Vernall ZL2CA, who organized the transpacific tests. "This is a one-way confirmation, as VE7SL does not have transmitting capability." (See sidebar "Analysis of the Received Signals and Argo Screen Captured by VE7SL" for additional details on this LF accomplishment.)
Vernall said that on June 30, seven New Zealand stations--including ZL6QH--and one Australian transmitted test signals in the 160-190 kHz band for the transpacific tests. "Various DX listeners had prior knowledge of the schedule of individual test frequency and coding used by each station," he said. Amateurs in New Zealand and Australia have access to 160-190 kHz.
The VE7SL Argo spectrograph showing reception of the ZL6QH signal. [Larger image] |
Reception of weak LF signals typically is done using spectrographic software like Argo or Spectran. McDonald--who lives on Mayne Island northwest of Victoria--used Argo to capture the ZL6QH signal and very likely that of ZL4OL, although no claim was being made for the latter.
Amateurs spanned the Atlantic in both directions earlier this year on 136 kHz. Efforts to duplicate the feat by making it across the Pacific have been under way during the winter season in the Southern Hemisphere.
"From an analysis of the screen capture, it is claimed that VE7SL received and positively identified signals from ZL6QH," Vernall's announcement said. "It is also very likely that signals were received from ZL4OL, but co-channel interference made the result too indistinct to obtain positive identification of coding."
The 10-foot-diameter receiving loop used at VE7SL. |
The reception occurred right around the time of sunrise in
British Columbia. Vernal said an opening between New Zealand and British
Columbia occurred approximately 45 minutes before British Columbia's sunrise on
June 30, faded at sunrise and then opened for another 15 minutes or so.
Steve McDonald, VE7SL. |
ZL6QH was transmitting dual-frequency CW with two-minute elements, one frequency representing dits, the other dahs. The ZL6QH station was running approximately 100 W into a longwire antenna. Vernall and Andrew Corney, ZL2BBJ, were the ZL6QH operators, with assistance from Richard Roberts, ZL1CPZ/MW0CPZ.
Other stations involved in the transpacific tests were ZL1WB, ZL3VN, ZL3FJ, ZL3PN, ZL3JE and AX2TAR (VK7ZAL), Vernall said.
An active contester and DXer, McDonald earlier this year was the first to claim Worked All States while using a low-power "Tuna Tin 2" transmitter. All contacts were completed while he was running about 400 mW.
Larry Kayser, VA3LK, who was among those succeeding in the transatlantic LF tests by completing a two-way contact, continues transmissions on 136 kHz to Oceania each evening. Kayser is one of a few Canadian amateurs with special authorization to transmit on 136 kHz.
The ARRL has petitioned the FCC to authorize Amateur Radio
allocations at 136 kHz and in the 160-190 kHz band. The petition is pending.
Analysis of the Received Signals and Argo Screen Captured by VE7SL
The ZL6QH TransmissionThe transmission format used by ZL6QH was dual-frequency keying, with 1-Hz shift, and "dot length" of 120 seconds. The identifier was Q, sent as "dah dah dit dah," with "dah" as 184.4005 kHz and "dit" as 184.3995 kHz. Dual-frequency keying has equal length elements for "dit" and "dah" and only a brief transition between elements to save time with very slow keying, so each "Q" in the 10-minute repetitious sequence of QQQQQ had the following format: Dah of 184.4005 kHz for 2 minutes, then a brief pause Dah of 184.4005 kHz for 2 minutes, then a brief pause Dit of 184.3995 kHz for 2 minutes, then a brief pause Dah of 184.4005 kHz for 2 minutes A silent period of 2 minutes (This was repeated for many hours.) The LF signal was generated using a modified TS-850 in SSB mode fed with audio from a laptop PC using VFSKCW software. The low-level LF signal from the TS-850 transverter port was fed to an external LF power amplifier, and the output power was around 100 W at the time of the VE7SL observation. The antenna was a long wire at the Quartz Hill club station, which is run by the Wellington Amateur Radio Club. The ZL6QH operators were Andrew, ZL2BBJ, and Bob, ZL2CA. Richard, ZL1CPZ (visiting MW0CPZ), assisted with ad hoc antenna maintenance that allowed ZL6QH to carry on with LF testing. ZL6QH transmitted from before ZL sunset to after ZL sunrise, with one break earlier in the evening for transmitter maintenance and one break for antenna maintenance that happened to be at the beginning of the opening to VE7, and it was fortunate that work was completed in time to allow the transmitter to operate over the period that we now know was when propagation to VE7 was very favorable.
ZL4OL TransmissionThe transmission format used by Mike, ZL4OL, was single-frequency keying with 184.4000 kHz carrier, and 120-second "dot length." It was deliberately arranged to be in between the dual-frequency keying of ZL6QH and allows one correctly tuned Argo screen to be able to capture either signal. Originally, ZL4OL was intending to use an identifier of "L"--as it has a mixture of dits and dahs--to assist in identification, but PC problems at the time meant he resorted to manual keying, so instead used "O" as an identifier, so the 15- minute sequence for ZL4OL was: Dah of 184.4000 kHz for 2 minutes Silent for 2 minutes Dah of 184.4000 kHz for 2 minutes Silent for 2 minutes Dah of 184.4000 kHz for 2 minutes Silent for 5 minutes (This was repeated for many hours.) ZL4OL synchronized his 15-minute sequences to start on the hour, and he kept up the manual keying for some seven hours, closing down at 1155 UTC, five minutes before midnight local time. The transmitter power was 500 W, and the antenna was a home-station Tee.
VE7SL ReceptionSteve, VE7SL, set his R75 receiver for 184.4 kHz, with a CW sidetone frequency of 600 Hz. An earlier check with the 60- kHz standard frequency station showed a 0.2 Hz error, so the receiver was set 0.2 Hz from having 600 Hz in the middle of the Argo screen. The antenna is a home made octagonal loop antenna, with 10 foot diameter. The Argo screen capture has a PC time stamp of 6:16 AM, but it was known to be four minutes from actual time, so correcting for that, and converting to UTC, the screen capture was at nominally 1312 UTC, which is approximately an hour after the local sunrise at 1216 UTC. The screen shows a sequence of dashes at nominally 599.7 Hz, and a varying brightness line at nominally 600.2 Hz. The dashes at 599.7 Hz are in agreement with the ZL6QH transmission, for the "dit" part of the dual-frequency "dah dah dit dah." The "dah" part of the transmission should be 1 Hz higher in frequency, and that is just off the top of the Argo border on the screen capture, missing out by about 0.1 Hz. However, despite the receiver tuning situation, the part of the ZL6QH signal that was displayed is undoubtedly from ZL6QH, as an analysis of the "dit" timing is virtually identical to the transmitted pattern. From a local log at ZL6QH, 1200 UTC occurred a quarter way through third visible "dit," and sunrise at 1216 UTC occurred close to a "missing dit," which is assumed to be a fade, then one more "dit" was received before daylight reduced the DX propagation. A reason for ZL6QH not having any "dits" showing to the left of those on the screen capture was that the transmitter was shut down to carry out antenna work (in the dark, with a spotlight), as rising wind resulted in the long wire intermittently touching the leg of a Vee antenna at Quartz Hill, and a tether had to be used to guarantee clearance of crossing wires. The first "dit" showing on the Argo screen is the first one transmitted after the antenna crossover was attended to. The other significant part of the Argo screen shows a varying brightness line at nominally 600.2 Hz. This is close to the intended ZL4OL frequency, being nominally 0.5 Hz higher than ZL6QH "dits." ZL4OL ceased transmission at 1155 UTC, which agrees well with the end of bright patches on the line. From the start of the line, the propagation opening was from around 1120 UTC. The line also re-appears weakly after ZL4OL ceased transmission, so it seems that an interfering signal was present, unfortunately, right on the ZL4OL carrier frequency. Further, the interference is likely to be a DX source, as it came and went over a similar time frame as the ZL propagation opening. While it is very likely that ZL4OL signal was received by VE7SL, it is too indistinct to positively identify the coding used, due to a combination of co-channel interference and fading. Later checks of the R75 showed that it does give rising audio frequency for rising radio frequency, so the captured signals make sense as to where they are relative to each other, as transmitted. The Argo capture is equivalent to a down-converted version of the LF spectrum. It would have been better still for the R75 to have been centered with 600 sidetone corresponding to 184.4000 kHz, however the result was as recorded, and it happened to capture on the screen only one half of the frequencies from ZL6QH. Despite this, it is felt by the participants that there is no doubt that the "dits" that were captured did come from ZL6QH, and can be used to claim a one way DX reception report by VE7SL. It was unfortunate that there was interference on the ZL4OL frequency, as that involves a longer path length, by some 598 km.--Bob Vernall, ZL2CA
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