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I've managed to complete my new 630m loading coil / variometer combination but will need to wait for the completion of my impedance matching transformer before I can test it out on the antenna. From earlier tests on 475kHz, it seems that my inverted 'L' needs about 190uH for resonance on 630m so just a small loading coil was needed. The built in variometer will allow the system to be tuned to resonance easily, without the need for playing with taps. Once I had started to wind the main coil, I decided to put on a few more turns than I had originally planned, reasoning that it would be easier to remove turns if less inductance was needed than it would be to add more turns if I fell short.     My matching transformer will be similar to the one used on my 2200m system for the past several years. Construction details may be found on the GW4ALG web site. This method of matching, rather than tapping up from the grounded end of the loading coil to find the correct impedance match, is much easier to use and readily allows for changes to be made as the seasons change from winter (wet) to summer (dry).

Source: http://www.alg.myzen.co.uk/radio/136/ant_xformer.htm

 

Source: http://www.alg.myzen.co.uk/radio/136/ant_xformer.htm

To avoid core saturation at 1kW, my 2200m transformer was wound on two pieces of 'street ferrite', a phrase coined by VE7TIL  to describe the abundance of these free flyback cores often to be found in discarded TV's and computer monitors. The ferrite usually has a very high permeability and works well in this application as well as for switching FET amplifier output transformers...and, the price is right!  

Source:  http://leoricksimon.blogspot.ca/2007/05/flyback-driver.html

The challenge is removing the core from its encapsulated shroud without damaging the core. Once you get the hang of it, it is fairly easy to do, but you must work carefully with the brittle ferrite. With the proliferation of LED TV's and monitors, this source of free cores will not be around  much longer so grab them while you can ....this ferrite is just too good to throw away!

Courtesy: http://www.nasa.gov

It seems there are still a few surprises left in the strange life of Cycle 24. Yesterday's major X1.6 solar flare seems to be nicely positioned for an earth-impact on Friday. The blast follows an earlier M4.5 flare the day before and the one-two combination could deliver some interesting VHF propagation as the solar stream impacts our planet.

Courtesy: http://www.nasa.gov

Video of the event shows what looks like a near full-on earth-directed hit but for a northerly component. Only time will tell.




Sky watchers as well as VHFers should be alert for possibly major auroral displays on Friday or Saturday.

I've decided, for the time being, to keep my 2200m (136kHz) antenna tuning system separate from the 630m system. This means that I'll need to build a new loading coil, variometer and impedance matching transformer. I'm not really sure why I should maintain the 2200m capability since there is not really much activity here. The only two excuses that I have at present are the fact that it took a heck of a lot of work to get to this point (but it was mostly "fun work") and that the U.S. may be getting the band soon. I'm also not convinced that even if the U.S. does get the band that it would translate into much new activity....so, for the time being, I will keep the system intact.

I've used an online coil calculator to design the coils needed for loading and for the variometer....it will be interesting to see how close the finished values compare with the calculated values. I hope they're not too far off! Here is what the plan calls for:



The main loading coil will be built on a low-loss 6" styrene pipe coupler using #16 solid copper transformer wire, spaced at 3mm. The coil will be elevated above the main form by strips of styrene rod that I have filed small notches into, every 3mm. The rod height will be staggered around the form, gradually stepping down one full turn every 360 degrees. Inside the main coil, the smaller variometer coil will be wound with poly-covered #18 stranded wire on a short length 3 1/2" PVC pipe.




Hopefully I'll get something that tunes from 130-230uH, approximately....if so, I'll not only be happy, but really surprised!

Courtesy: https://www.google.ca/maps/

Propagation to Alaska was much better than usual this morning. A two-minute Perseus recording at 1300z, about 45 minutes before my local dawn, revealed some excellent signals. Unlike many of the beacons in northern Canada, most of the Alaskan NDBs are not purposed for long-range use and run the standard 25 watts into 'T' or short loaded vertical antennas located right near the runway.

09/09/14 1300 529 SQM Level Island AK CO36

Highlighting the morning was my first "new catch" from Alaska in several years - 'SMA' at St. Mary's Lake on 230kHz. It has been on my morning check list for many many years but only today did it decide to reveal itself!

09/09/14 1300 230 SMA St. Mary's AK AP82 USB 231.085 no sign of a LSB

Reported to be running 70 watts, this particular beacon has never been reported to the RNA NDB list nor even heard by those listening in Alaska. I suspect either a very tough path or a system in need of a tune- up. A Google Map view appears to show a single vertical antenna but it may be one end of a 'T' support.

Courtesy: https://www.google.ca/maps/

Hopefully conditions will continue to improve as there are still a few up there that have yet to be logged!

Drain (top) vs Gate (lower) on testbed Class-E GW3UEP TX

I've just completed the Muppet-styled printed circuit version of my previously breadboarded GW3UEP 630m transmitter. The earlier version was built "ugly style" in order to optimize part values and measure circuit parameters.

Testbed (Ugly-Style)

The "ugly version" performed well at 12V and during overnight beacon testing was aurally copied as far east as Kansas. Although the final version has yet to be mounted on its small 19" rack panel, along with a meter to monitor final amplifier drain current, all indications show that it too works well.

Final Version (Muppet-Style)

This version, based on the GW3UEP design, has a few small changes, the main one being the addition of a second parallel-connected FET ....described in an earlier blog.

Running the TX at 12.8VDC on the drain(s) at 2.3A produces an input power of 29W. The measured power out, after the LPF, is 23W into a 50 ohm load. This represents an efficiency of 80%. When run in the normal speed CW mode, the FETs run cool enough that they would probably not even need a heatsink but if run in any of the QRSS (long keydown periods) modes, would certainly benefit from  heatsinking.

Running the TX at a higher voltage of 22.6VDC (on the amplifier only) yields a current of 4A for an input of 90W. Measured output power is 71W for an efficiency of 79%.

Heatsinking would be required at this power level, even for normal speed CW but the finals seem to run just slightly warm. A larger heatsink or possibly a small fan as well would be required for any QRSS CW modes.

I suspect that the efficiency could be further improved yet with very fine tweaking of the output circuit L/C network but the extra few watts gained would not be significant.

At either power level, this easy-to-build transmitter would make a great "first 630m transmitter" for anyone wanting to get started on our new band.

Mike Tuggle's Lyonodyne 17 Crystal DX Tuner

The use of integrated circuits can be interesting in that one IC can be used to build a full superhet. The use of an IC means that the set will not qualify for the 1AD nor for the 2AD bonus points."

The challenge was too hard to resist for many and the contest was popular for several years running. Some of the inventive entries for individual years may be seen here. The contest logbooks  also make for interesting reading and demonstrate the capability of some of these simple radios.

Although the contest has not been run for the past few years, there is still much interest and discussion of "1AD" radios on Dave Schmarder's "RadioBoard" forum.

Mike's LF tuner is a prime example as he uses it daily and continues to post some amazing DX to the Yahoo "ndblist" Group. His furthest ndb catch in North America with the regen has been "YY" in Mont Joli, Quebec.
Now, "YY" is a good catch for me, from B.C., but Mike is listening from Kaneohe, Hawaii !

You can read about Mike's original design here, while his latest version shown below, incorporates a dedicated LF antenna tuner.

LF Regen (Courtesy Mike Tuggle)



LF Regen Schematic (courtesy Mike Tuggle)

A recent posting to the ndb list by Roelof Bakker(PAØRDT) of mini-whip prominence, described his recent construction of his own LF regen, based largely on Mike's design but with a few interesting changes.

Courtesy: Roelof Bakker, PAØRDT

Roelof has also published a nice write-up describing the project which sparked a lot of "must build" discussion within the group.....even enough to make Mike get out his soldering iron and build the European-version!

As old and as simple as they are, regenerative receivers still hold much fascination amongst radio builders and dollar-for-dollar are amazingly good performers, especially on LF.

Courtesy: https://maps.google.ca/

It seems that the recent Trans-Pacific reception of WD2XIQ's Texan WSPR signal by VK2DDI has stirred up a lot of interest from the boys down under. Despite some recent geomagnetic disturbances, some of those that are taking the time to beacon or to listen are being justly rewarded. Sunday's overnight beaconing has produced four more confirmed reports of the U.S. Part 5 experimental stations being heard in both VK and in ZL.

Once again, John ("XIQ"), was heard on the other end....not in Australia but in New Zealand, by Con (ZL2AFP) listening in residential Wellington. Con also caught signals from Larry, W7IUV, in central Washington state, operating on 630m as WH2XGP. Not to be left out of the action, Rudy, N6LF, running as WD2XSH/20 made it down to both VK2XGJ and VK2DDI before the sun came up south of Eugene, Oregon.

Larry, W7IUV ("XGP"), was running a true backyard-size antenna system...just a 34' loaded vertical with a sloping zig-zag top loading wire.  His small wire radial system covers a 16' x 25' patch. His homebrew amplifier, constructed almost exclusively from salvaged computer parts, uses 8 switching MOSFETs in push-pull / parallel running in the rare linear mode! The fascinating description of his amplifier's design and construction can be found at the W7IUV website. With the small vertical, estimated erp is  ~ 10 watts.
Larry's station should be inspirational for anyone who thinks they need huge antennas to be successful on 630m!

Rudy, N6LF ("XSH/20"), runs around 20Weirp to a large top-loaded vertical. The center (radiator) pole is almost 100' high while the top-loading support poles are 80'. Full details of Rudy's fine system, along with much more about 630m, may be found at the Antennas By N6LF website.

N6LF/WD2XSH/20 630m Top-Loaded Vertical

It wasn't just the U.S. Part 5'ers who were on the ball early Sunday morning. ZL2AFP, set up with just a small PAØRDT-style miniwhip at 28' feet and an IC-746PRO receiver, managed to snag two of the northerners. John Simon, VK2XGJ, also listening from a normal-sized suburban lot in Dapto (NSW), with lots of nearby powerlines, caught "XIQ"'s Texas-launched signals on his venerable FRG-100 tied to another small active miniwhip at 20'. Interestingly, the U.S. signals were detected about four hours after local sunset in both ZL and VK. 

LF RX Stack at VK2XGJ

It seems clear that 630m has much to offer in the way of some exciting propagation opportunities and that experimenters do not require large amounts of room to take advantage of this unique part of the spectrum.
Hopefully conditions will continue to provide more long-haul reports in the coming weeks.

In the meantime, remember that Canadian amateurs now have free access to the 630m band, but much more activity is needed...VE6, VE5, VE4, VE3, VE2...who will be the first on 630m in those provinces?  It's time to start melting solder and stringing antennas before winter arrives!