Posts Tagged ‘630m’
Music To My Ears
April 26th, 2016 | 
Author: 
In my 'other' life, before retiring, I taught high school for 35 years. I soon became tired of doing my nightly lesson preps and marking of papers on the kitchen table so I built a large oak roll-top style desk, but without the 'roll' part.It had lots of drawers, both big and small, slots and cubby-holes, and made the nightly homework very much more enjoyable.
The left end of the desk was occupied by my Sony ICF -2010 and above it, on the desk's top shelf, was a small amplified and tuneable ferrite loop antenna. The Sony was tuned to the 500kHz international MF 'distress' frequency, which was mainly used as a CW calling frequency for ships wishing to work the coastal traffic handling stations. Once contact was established, stations would move to the 'QSS' working frequency used by the coastal, so that the distress frequency was not tied-up.
As I sat at the desk doing my nightly prep, the silence would be broken every few minutes with the sound of a CW caller, either a coastal or a ship. It was music to my ears.
On a normal night, the numerous coastals could be heard with their periodic traffic lists interspersed with ships up and down the coast calling with traffic or weather reports. However, on a really good winter night, the frequency was almost constantly abuzz with CW. Ships, as well as the coastals, could be heard from the Gulf of Alaska down to the Gulf of Mexico ... as far west as the Hawaiin Islands and on really rare nights, along the eastern U.S. seaboard. On those nights, 500kHz would sound like 20m CW, even on my little Sony and desktop loop.
Thanks to the forethought of those that had the good sense to record some of those amazing sounds, you can step back in time and listen to what '500' sounded like back in its prime ... recorded somewhere in western Europe.
The most recent 630m crossband activity brought back these pleasant memories of what the band could sound like at times, with several very strong VE7's and a few weaker U.S. experimental stations to the south, all busily calling CQ at the same time on various frequencies. I consider it a huge privilege to be able to operate on this much revered part of the radio spectrum ... one steeped in such great CW tradition.
I think it won't be too long before 630m will sound much like its old glory days again ... and wouldn't that be a wonderful thing.
VK4YB Lights Up West Coast On 630m
The past few weeks have seen many of the VK 630m WSPR stations making it into North America's west coast and points east. VK2DDI, VK2XGJ, VK3ELV and VK4YB have been the signals most often seen. Particularly dominant is the signal from Roger, VK4YB, the northern-most station, located in Moorina, Queensland, near the Pacific Ocean.Roger's signal has been decoded locally by myself as well as VE7BDQ and VA7MM, creating excitement over the more normal nightly spots from the central states.
2016-04-13 11:10 VK4YB 0.475646 -28 QG62ku 5 VA7MM CN89og
2016-04-13 11:20 VK4YB 0.475647 -29 QG62ku 5 VA7MM CN89og
2016-04-13 11:28 VK4YB 0.475647 -28 QG62ku 5 VA7MM CN89og
2016-04-13 11:28 VK4YB 0.475644 -23 QG62ku 5 VE7BDQ CN89la
2016-04-13 11:36 VK4YB 0.475644 -26 QG62ku 5 VE7BDQ CN89la
2016-04-13 11:52 VK4YB 0.475643 -25 QG62ku 5 VE7BDQCN89la
2016-04-13 11:56 VK4YB 0.475643 -28 QG62ku 5 VE7BDQ CN89la
2016-04-07 08:54 VK4YB 0.475643 -25 QG62ku 5 VE7SL CN88iu
2016-04-07 09:36 VK4YB 0.475644 -29 QG62ku 5 VE7SL CN88iu
2016-04-07 10:08 VK4YB 0.475644 -29 QG62ku 5 VE7SL CN88iu
2016-04-07 10:18 VK4YB 0.475644 -29 QG62ku 5 VE7SL CN88iu
2016-04-07 11:04 VK4YB 0.475644 -29 QG62ku 5 VE7SL CN88iu
2016-04-13 11:06 VK4YB 0.475644 -24 QG62ku 5 VE7SL CN88iu
2016-04-13 11:10 VK4YB 0.475644 -23 QG62ku 5 VE7SL CN88iu
2016-04-13 11:20 VK4YB 0.475644 -23 QG62ku 5 VE7SL CN88iu
2016-04-13 11:28 VK4YB 0.475644 -28 QG62ku 5 VE7SL CN88iu
2016-04-13 11:32 VK4YB 0.475644 -25 QG62ku 5 VE7SL CN88iu
2016-04-13 11:52 VK4YB 0.475643 -18 QG62ku 5 VE7SL CN88iu
2016-04-13 11:56 VK4YB 0.475643 -22 QG62ku 5 VE7SL CN88iu
2016-04-13 12:16 VK4YB 0.475643 -27 QG62ku 5 VE7SL CN88iu
2016-04-13 12:28 VK4YB 0.475643 -26 QG62ku 5 VE7SL CN88iu
2016-04-13 12:32 VK4YB 0.475643 -25 QG62ku 5 VE7SL CN88iu
2016-04-13 12:54 VK4YB 0.475644 -24 QG62ku 5 VE7SL CN88iu
2016-04-13 12:58 VK4YB 0.475643 -24 QG62ku 5 VE7SL CN88iu
2016-04-13 13:10 VK4YB 0.475643 -25 QG62ku 5 VE7SL CN88iu
2016-04-13 13:24 VK4YB 0.475643 -27 QG62ku 5 VE7SL CN88iu
2016-04-13 13:28 VK4YB 0.475643 -27 QG62ku 5 VE7SL CN88iu
Roger has sent the following information to me regarding his well-planned system:
My antenna is serendipitous.
I am a complete novice on 630m. I only came on the band about 2 months ago at the request of a local friend, Peter, VK4QC. That is not quite true, because I was on the band once before, about a year ago and made one contact and then managed to burn out the front end of my Drake TR7, which I had roughly converted to 630m operation.
My QTH is atop of a stony ridge on 10 acres. The previous owner said there was some soil somewhere, but I haven't found it yet! Ground conductivity is very poor, I think. If you drive in two stakes about six inches apart, an ohmmeter says infinity. That's if you can drive in a stake. Because after the first quarter inch you hit shale rock. Interestingly the shale layers are at about 60 degrees to the horizontal. There are some quartz inclusions. Yes, I have tried crushing the quartz and panning it - no gold!
Getting back to my story, I needed to put up a 630m antenna in a hurry. The idea of winding a big loading coil with the rotatable inner coil was a bit daunting. And putting down ground radials or an earth mat was out of the question. So, using only some wire, string and a bow and arrow, this is what I came up with:
What is missing from that drawing is that the wire is running North-East to South-West, all in a straight line, with the shack at the North-East end. It is line-of-sight from the top of the vertical section to the Pacific ocean. I didn't put the direction on the original drawing because I didn't think it was important. I thought it was essentially a top-fed vertical and would therefore be omni-directional. Nothing could be further from the truth. Experience has shown that it is very directional. I have never had a single report from Japan, and yet my signal has peaked at -3 in Hawaii (about the same distance). Also VK3ELV, using a quarter wave near vertical, gets almost nightly reports from both Japan and Hawaii and at similar strengths. That would seem to indicate a front to side ratio of more than 20dB for my antenna, which is surely impossible?
I estimate the feed point impedance is about 3000 ohms. The ATU has 48 turns on the secondary, tuned by fixed capacitors of 960 pF in parallel with a 500 pF variable which is about two thirds meshed. The primary is 5 turns fed by the transverter having a 50 ohm nominal output. The impedance at the top of the secondary should be near 5000 ohms, but the antenna feed wire is tapped about two thirds of the way up the secondary coil, which gives 1.03 : 1 SWR. The earthy end of the coil is connected to the mains earth and the metal work of the shed. I haven't tried terminating the far end. I did think about connecting it to the fence wire that runs round the property but I thought that might be a bit dangerous. There would be high voltage points in places. The transverter output is nominally 50 watts, but it is giving about 90 watts in reality.
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| Roger - VK4YB |
Like many on 630m, Roger is using an Elecraft K3 into a transverter to generate his 630m 90 watt signal. It is interesting to see the strength of Roger's signal here throughout the night but particularly during the 1152-1156Z time slot. His signal peaked at -18db, right at the level of audibility ... CW levels, but quickly dropped. Throughout the night however, his signal was easily within range of the capabilities of the two-way JT-9 WSPR QSO mode ... had either of us been seriously involved in a two-way JT-9 QSO attempt during that night, it would have been quick work I think.
John, VE7BDQ, has already managed to push his WSPR signal to VK on more than one occasion ... this from a typical, suburban backyard inverted-L. The possibilities are exciting, but will mean some middle-of-the-night vigilance!
As activity on 630m increases in both VK and VE, we are beginning to see more and more DX possibilities arising, particularly during the Spring and Fall equinox periods when this path seems to peak. As activity in Japan picks up, it is only a matter of time before some of them begin showing up in numbers here on the west coast, as the path to JA has always been reliable and somewhat less demanding than the path to down under. I suspect also, that as the present solar cycle draws down (and supposedly goes 'quiet'), 630m Trans-Pacific signals will grow even stronger,and on most other paths as well.
In view of the JT9 QSO possibilities, I think it is clear that I now need to seriously think about building a transverter, allowing me to at least be in 'ready-mode' for the coming 630m challenges ... hopefully for the next equinox.
Top Hats
When it comes to discussion of 630m, the topic of antennas seems to top the list. One of the easiest ways to enjoy what 630m has to offer is to try and utilize a low band antenna that may already be in place. An 'inverted-L' for 80 or 160 can be readily bottom-loaded and with a few radials, can provide a good starting point ... but with a little additional work, its efficiency can be easily improved by expanding the top horizontal (top hat) section.Jim, W5EST, has posted an interesting description of the pros and cons of the 'top hat' in a recent KB5NJD daily 630m report. Those thinking about getting on the band or those considering ways of improving their present antenna might find the information helpful.
Top Hat Advantages:
Higher EIRP comes from a more nearly uniform current distribution all the way up a TX vertical. https://en.wikipedia.org/wiki/T-antenna . But remember that adding top hat doesn’t help you if your license is subject to a legal limit EIRP that’s reached by your station already.
A vertical without a top hat has no current at its tip, meaning the upper part of a hatless vertical is inefficiently used. Average RF current for a hatless short vertical is only half what an RF ammeter shows at the antenna base. Top hat lets a shorter vertical antenna yield same total radiated power TRP by increasing its degree-amperes, as discussed March 31, this blog.
2 amperes of 630m RF base current in a 10° tall hatless short vertical can give 10 degree-amps (2 x ½ x 10°) and yield 15 degree-amps with an ample top hat. A top hat can increase average RF current by about a quarter to half, which could as much as double the TRP.
Top hat increases antenna system capacitance. You get more flexible QSY by decreasing the system Q. SWR increases rapidly as your frequency departs from antenna system resonance, see graph Feb. 10, this blog. With lower system Q the SWR doesn’t increase so rapidly. Then you can QSY temporarily a little way without retuning or by just retuning a little in the shack instead of outdoors at the ATU.
Decreased Q somewhat lowers antenna voltage KV from antenna base to top hat. On 630m Q = (2π 475)L/R by definition and Vantenna = 1.4 Q P / I < Vbreakdown. See Jan. 16, this blog.
Top hat wires can be symmetrically or asymmetrically positioned to give approximately similar capacitance whichever way. I’ve not modeled the effect of a top hat on the azimuth and elevation antenna patterns of an electrically short vertical. I don’t think the effect is very significant. But if you know a link or some better information about this, let us know.
If your radials have extended way beyond the extent of a small top hat high above, then providing longer top hat conductors above the radials can more efficiently utilize the radials. If the radials mostly go in one or two directions, then for highest antenna system capacitance the hat wires should extend in those directions to couple best with the radials. Your experience may suggest this last is not too important, especially if you have a perimeter conductor and/or several ground rods and your soil has favorable conductance.
Another top hat advantage is that top hat conductors are compatible with structural support and stabilization for the very top of an MF/LF vertical antenna. You get added degree-amperes–and steadying at the top to boot.
If the top hat slants upward, its system capacitance contribution is somewhat decreased compared to a top hat of same length horizontally, but the vertical slant contributes radiated power. Depending on the arrangement of antenna and trees on some properties, using a shorter vertical with an upwardly slanting asymmetrical top hat may make the antenna system both easier to guy and less obvious to neighbors.
Putting in a top hat or improving a top hat increases the degree-amperes of a short vertical mainly by distributing the same RF amperes more uniformly. Adding more radials and longer radials decreases the antenna system resistance and increases the degree-amperes of a short vertical mainly by increasing the RF amperes of antenna current itself.
Top Hat Disadvantages:
A top hat obviously requires outdoor work to construct or revise it. You may be able to simply increase your transmitter power TPO more conveniently than to do the outdoor work.
A top hat needs to extend more or less horizontally from the top of the vertical, although the angle is not too critical within +/-45°. Distant supports for the top hat at that top level may be unavailable or expensive and inconvenient to provide. If the top hat were attached to the vertical below the top of the vertical, the otherwise radiation-beneficial top segment of the vertical becomes mostly unused.
If the top hat slants quite steeply downward, its effect on system capacitance may be a wash– more capacitance by closer approach to the ground and less capacitance because same length top hat conductor extends less outward over the ground below. That defeats a reason for putting up a top hat in the first place.
Moreover, if the top hat slants steeply downward, then vertically downward RF current in the top hat cancels part of the radiation from the vertical antenna and at least partially defeats the improvement in vertical antenna current uniformity that the top hat is intended to confer.
A long top hat may not fit on the available real estate. Even if it fits, it may add to visibility as far as difficult neighbors are concerned.
Adding a top hat means you need to retune the ATU after the addition. But so does improving the radials or just about anything else you do.
Top hat conductors add more weight on a vertical than lighter-weight guying does. The weight of the top hat likely adds to the support demanded of the antenna base. If you put downward-slanting top hat conductors under tension at their far ends to keep them from drooping in the middle, then a lot of that tension will be imposed on the vertical too. That can produce a buckling force on the vertical which may call for additional guying halfway up the vertical.
Top hat conductors convey a declining but substantial RF current along their length. That involves I2R losses in the skin effect resistance of the top hat conductors. However, if your earth resistance is high or your radial/grounding system is not very elaborate, some loss in the top hat probably does not decrease the RF amperes of antenna base current very much at a given TPO compared to the improvement in radiation TRP that the top hat gives you.
If skin effect resistance losses in the top hat are significant compared other losses in the system, reducing top hat losses generally means more conductors or heavier conductors in the top hat. That translates to more weight for the whole system to support.
A top hat translates KV of antenna top voltage to its ends. If the top hat extends all the way to leaf cover of trees or shrubs, unexpected sparks might jump to them in quiet weather, or in windy weather, or sometime when such trees or shrubs grow nearer to the top hat end(s).
Generally top hat advantages outweigh their disadvantages so long as you plan intelligently. Please tell us your experiences with top hat advantages and disadvantages!”
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| A G3XDV LF top hat |
Jim often adds an interesting op-ed piece to the KB5NJD daily report and sifting back through the past few weeks will provide some great 630m 'food for thought' bed time reading!
630m To Down Under
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| Today's Sun courtesy: http://sdo.gsfc.nasa.gov/ |
With the sun remaining reasonably quiet over the past several days, a sudden spike in the geomagnetic field on Saturday afternoon saw a number of trans-Pacific spots showing up on 630m WSPR mode.
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| courtesy: http://wdc.kugi.kyoto-u.ac.jp/ |
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| courtesy: https://www.google.ca/maps |
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| VK3ELV 630m |
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| courtesy: https://www.google.ca/maps |
Although VK3ELV's signal was right at the edge of WSPR decoding levels (-29db), it would only take a few more db to allow a two-way JT9 digital mode QSO to take place ... maybe something that will be possible in the coming years of solar minimum and much better LF/MF propagation. To be readable on CW would need an equivalent true power output increase of at least 16 times, requiring VK3ELV to run around 2,000 watts output!
Over the years I have seen ZL6QH a number of times on 2200m (QRSS CW mode) but this is my first reception of VK and, hopefully, not my last.
To keep up to date with overnight activities on 630m, visit the excellent site of KB5NJD. John posts a detailed daily summary of events. In addition, you will find some excellent resources to help you get involved in this part of the spectrum ... and remember, you don't need a big backyard or a big antenna to have fun on 630m.
Local Lightwave Activity / A New 630m Resource Site
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Toby, VE7CNF, has sent me some mail indicating that his new lightwave system is ready for a two-way test!
His system is very similar to the ones built and deployed by myself and Markus, VE7CA, in late 2013. The culmination of that activity is described here, in 'On Making Nanowaves - Part 6'. Our lightwave QSO and homebrew gear were later described in a 'how to' article in the 'The Canadian Amateur' as well as in the newest edition of 'The Radio Amateur's Handbook' (2016).
Toby describes his most recent pre-QSO backyard testing:
The lightwave gear appears to be working well. Focus looks good and the
finder scopes are doing their job. There's a reflective sign high up on a
hydro tower 170 meters away that's handy for testing. It lights up bright
when the transmitter's on it.
Back scatter off the clouds above my house worked too. I heard my CW beacon, audible 339, off a patch on the clouds about 1 degree wide. I don't really know if it was clear air scatter from closer by, or scatter off the clouds, but the spot was small. That's with the tx on the front deck, and rx in the back.
I used Spectran to check the noise from city lights in my area. At QRSS10
speed there are spectral lines at 540, 600, and 660 Hz. They aren't too
strong, but those are some frequencies we should avoid.
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| VE7CNF's lightwave system - TX (L) & RX (R) |
Hopefully the weather will co-operate enough to allow us to make a two-way QSO later this week. Plans call for Toby to set up near the same location in West Vancouver used by VE7CA as it offers a clear LOS path to Mayne Island, 54km to the southwest.
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| 54km Georgia Strait crossing (courtesy: https://www.google.ca/maps) |
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Rik, ON7YD, has set up a new website devoted to information specific to 630m. His 472kHz.org site looks as if it will be a valuable resource for those looking to get information and a start on our new band. At present, there is some really great information regarding transmitters, antenna systems and calculating E(I)RP levels. Have a look!
ARRL Working For LF / MF Future
As the rollout of new LF and MF ham bands grows closer for U.S. amateurs, earlier this month, the ARRL requested the FCC to carefully consider the procedural requirements governing the advance notification of local electric authorities of their intended 630m / 2200m operation. The FCC had suggested that under certain circumstances (mainly the distance to the nearest PLC signal-carrying power lines), amateurs would be required to notify and co-operate with power authorities ... but it was all very vague and seemed to place the conditions under which operating authority would be granted into the hands of the power companies.
In what appears to be a preemptive move to head-off the (possibly) overly onerous and impossible roadblocks suggested by power company representatives, the ARRL filing states:
“ARRL does not object to such a notification requirement, provided that it is appropriately circumscribed, not overbroad in its applicability, and not overly burdensome for radio amateurs to comply with,” the League’s statement asserted.
In addition, the power authority Utility Telecom Council (UTC) has been notably silent on the issue ... slowing the process even further.
"The ARRL noted that comments filed by the Utilities Telecom Council (UTC) called for a system of “quasi-coordination” by radio amateurs before commencing operation on 2200 meters (135.7-137.8 kHz). In its remarks to the FCC, the ARRL pointed out, however, that the UTC has not volunteered any information with respect to how a notification process might work nor offered any PLC database information to the ARRL or to the amateur community so prospective users of the band could determine if their operation might be problematic."
The League took the opportunity to remind the FCC, once again, that the low ERP levels generated by amateurs operating on the new bands would have a low probability of creating any interference and further pointed out that PLC systems operating between 9 and 490 kHz are not subject to protection from licensed services.
The ARRL also indicated that any sort of blanket notification requirement prior to transmitting on 2200 or 630 meters “would be clear regulatory overkill,” and that utility companies should clearly be required to demonstrate how amateur operations would cause harmful interference to their PLC (unlicenced) operations.
It's good to see the ARRL still being proactive with regards to procuring these new frequency allotments on behalf of U.S. amateurs ... hopefully making implementation sooner rather than later. The entire ex parte filing can be read here as well as the ARRL's own news posting of the procedure here.
In the meantime, I'll make yet another call-to-arms to fellow Canadian amateurs, who already have these two new bands but aren't using them ... new activity from the western provinces would be especially welcome as there are a now a number of well-equipped stations in VE7 who would like to work you.
PAØRDT Miniwhip Shakedown Continues
Those of you that have been following the recent set of four YouTube videos posted in my recent PAØRDT Miniwhip Shakedown blog, regarding the care and feeding of the PAØRDT active e-probe antenna, may be interested in a fifth video in the series, posted by Mike in the U.K.
PAØRDT's recent modification of the isolating transformer, in the miniwhip coupling unit, provides much better immunity to common mode noise-coupling in the HF bands. Mike shows the installation and operation of the new unit along with some additional grounding out at the antenna.
Those of you that are looking for a possible solution to relatively good reception on LF or on the 630m band, might find the answer with a carefully thought out installation such as the one shown in Mike's video series.
Although living in the suburbs often means dealing with a lot of noise, particularly on LF / MF, Mike's system shows that excellent low noise reception is indeed possible. It is important to 'probe' your backyard with the antenna itself in order to find the quietest location for installation.
More information on the PAØRDT miniwhip and other low-noise LF / MF antennas may be found in previous blogs here.
PAØRDT's recent modification of the isolating transformer, in the miniwhip coupling unit, provides much better immunity to common mode noise-coupling in the HF bands. Mike shows the installation and operation of the new unit along with some additional grounding out at the antenna.
Those of you that are looking for a possible solution to relatively good reception on LF or on the 630m band, might find the answer with a carefully thought out installation such as the one shown in Mike's video series.
Although living in the suburbs often means dealing with a lot of noise, particularly on LF / MF, Mike's system shows that excellent low noise reception is indeed possible. It is important to 'probe' your backyard with the antenna itself in order to find the quietest location for installation.
More information on the PAØRDT miniwhip and other low-noise LF / MF antennas may be found in previous blogs here.
