AmateurRadio.com

As mentioned in my last blog, using a transverter to drive a separate amplifier requires some method of switching system in order to automatically handle the antenna, transverter and amplifier input / output ports. To run a relay switching system in the WSPR or JT-9 modes requires that the switching be controlled by the transceiver's PTT line which in turn is controlled by the WSPR software. Using VOX keying is out of the question as it causes the relays to be 'hot-switched' and with higher power will eventually lead to their demise.

For many years I managed PTT line control via my laptop's comm port but these are now things of the past, requiring switching to be done via the USB port. There are many commercial products available that will do this nicely as well as handle the audio feed from radio to computer and vice-versa, but I found that my homebrew version worked just fine. Making it work via the USB port however required a serial-to-usb converter. This was described here, in an earlier blog and for the few dollars invested has proven to be a very reliable interface.

The schematic of the switching control unit is shown below. It uses two inexpensive OMRON G2RL-1-E DC12 relays purchased from Digikey. Although not coaxial, the $3.09 (U.S.) relay will easily handle a kilowatt as decribed by W6PQL. These relays have large contacts, rated at 16A. I added a few extra components that absorb any relay switching transients as well as remove any RF on the control lines.

Relay Control Unit

Keying Line Damper: courtesy: KK5DR

The relays are shown in the 'receive' (none keyed) mode. In this position, the antenna is routed directly into the transverter's output connector. In 'transmit' mode, the transceiver's PTT line is grounded, switching the relays. The antenna moves over to the amplifier's output and the transverter's output gets connected to the amplifier's input.

I must say a few words about Digikey's service. I really am amazed at what a superb job they do in supplying hobbyists with small orders. So many companies nowadays cannot be bothered with such things or demand a large minimum order for the privilege of handling your purchase! From what I can tell, Digikey bends over backwards to help out the little guy, with no minimums as well as dirt-cheap, fast shipping. Living in Canada, I'm used to U.S. dealers making me jump hoops to place an order, only to find out that the cost of shipping is often prohibitively high or they ship only via UPS which I will not accept.

I placed a small two-page order with Digikey via their excellent web site on a Tuesday afternoon. On Friday morning, there was a knock at my door at 0800 hours ... it was a courier service delivering my parts! To put this in context, I live on a small island in the middle of Georgia Strait, accessible only by air or by ferry. To me this service is incredible and the cost of postage was only $6.00 (U.S.). I really have no idea how they do this but they obviously have put into operation a very efficient system ... hats off to them and their skilled management that has figured this all out. A few years ago I sent in orders to both Digikey and to Mouser, each within an hour of each other. Like my recent order, the Digikey parts arrived in just a few days while the Mouser parts took over three weeks ... perhaps things have changed since then but this is the reason I use and recommend Digikey whenever I can.

Once I had the needed parts, I quickly built a PCB for the switcher and put it together in a day so that I might begin 630m skeds with VK4YB as soon as possible.


If you would like a full-size layout suitable for the iron-on toner PCB construction method, I'll be happy to send you one via email.





The first test run with VK4YB at 0300 local time proved problematic. When I fired up at full ERP, I immediately saw some output instability on the scopematch screen. Before I could shutdown however, I had blown a FET in the amplifier, shutting me down and sending me back to bed to worry about the situation.

Having had time to think about the problem made me suspect something in the new relay changeover unit since that was the only new variable in the system. I suspected that perhaps the relays were not fully seated before being hit with full RF output and the possible hot-switching had caused enough short-lived SWR to take out the very reactance-sensitive FET final. In many years of operation with the amplifier, this was the first blown FET I have had. When I built it, I made sure that the FETS would be easily accessible (see below) should such an occasion arise ... unlike my initial transmitter, where replacing a FET was a nightmare.



Fortunately, when FETs go south on a push-pull amplifier, only one FET will blow ... whichever one was conducting at the time, thus preserving the remaining FET. I flipped a coin and unsoldered the source lead of the left hand FET and measured it. Sure enough it had a drain-to-source short. My day was off to a better start. Once replaced, I set out to determine what had caused it to blow in the middle of the night.

Since I didn't want to blow another FET, I could only 'key-up' in very short bursts and see if the instability was still present. I put the amplifier on a dummy load and everything seemed normal but when put onto the antenna, it reappeared. Suspecting an arc in the loading coil, I checked it carefully. I indeed did find a charred blackened section near the top high-voltage end of the coil but that could have been a short-lived event from the past as I'm sure small crawly things often meet their demise between the windings without causing any problems other than a quick puff of smoke or a short-lived arc to the PVC coil form.

After cleaning the coil and removing any carbon paths as well as giving it a few coats of varnish, I was hopeful that the problem would be gone ... but no, the scopematch indicated it was still misbehaving. As well, I could hear a weak but audible high-pitched oscillation coming from somewhere in the amplifier's circuitry. I suspected that it came from one of the output transformers but with the fan noise it was impossible to accurately locate the source of the rogue 'squeal' when briefly keying-up.

Fast forward several hours of pulling out what was left of my hair and I was no further ahead. The amp continued to work fine at high power, via the new relay system, into my dummy load but into the perfectly matched antenna, the problem remained. It was at this point that I decided to look at the input signal from the doubler, a nice squarewave at 950kHz for the amp's divide-by-two input chip. The scope instantly indicated a dual squarewave with more than one frequency present!

Recently built W1VD 'Frequency Doubler'

I control the input to the doubler by setting the transverter's output to 1W but at 0300 that morning had set it to 1/2 watt, noting that the amplifier seemed to be happy at that level. I then increased the drive from 1/2 watt to 1 watt while watching the 950kHz signal and immediately saw it morph into a wonderfully clean squarewave once again! Sure enough, the amplifier returned to complete stability into the antenna.

It looked like the doubler was not getting enough 475kHz input to actually double properly and its output was a mixture of 950 and (mostly) 475kHz. The amp's divide-by-two input would then try and turn this into a mixture of 475 and (mostly) 237 kHz which the highly-tuned antenna system would balk at, producing the unwanted FET-killing reactance. Being passive and none-reactive, the dummy load was quite happy to take the signal all day long if I let it.

With the mystery solved, full ERP beaconing and scheduling with VK4YB has begun once again, but the TransPacific path has been stingy for the past few mornings ... hopefully this will change now that I'm ready again, barring any further complications.

This past week I was eventually able to mate my W1VD frequency doubler with my 630m FET amplifier and run some higher powered tests on 630m WSPR and JT9 modes.


Up until this time, I have been limited to about 1/2 W EIRP but using the amplifier allows me to get to the 5W EIRP limit. I have been using the VK4YB transverter's 475kHz reduced output of 1W and driving the doubler previously built as part of a transverter project. The doubler produces a nice 950kHz squarewave to drive my amplifier's divide-by-two flip-flop input circuit which in turn produces the dual antiphase outputs needed to drive the push-pull switching FETs in the final amplifier. Being a linear transverter, when used alone at 70W, it will run any mode that the IC756 ProIII will produce such as SSB, WSPR etc, but my switching FET amplifier is class-D, non-linear, which limits it to non-linear modes such as CW, WSPR and JT-9, the most popular modes on 630m.

A few days ago, VK4YB and I ran our first 630m sked on JT9 as conditions looked favorable. Unfortunately, this was before I had my transverter / antenna switching system completed so I was limited to the barefoot transverter at ~ 1/2W EIRP. Using a transverter to drive an external amplifier means the antenna must be switched between the amplifier output and the transverter input in addition to switching the transverter's output between the antenna and the amplifiers input. I'll post details of my switching system, and inexpensive but power-capable relays, in an upcoming blog as there are probably many 630m operators planning on doing something similar.

Thanks to Roger's huge antenna, his 90W signal was making it through well enough on this end but he was not able to decode anything from me.



1109 -26 0.3 1098 @ VE7SL VK4YB QG62
1111 -28 0.3 1098 @ VE7SL VK4YB QG62
1147 -24 0.1 1100 @ VE7SL VK4YB QG62
1149 -27 0.1 1100 @ VE7SL VK4YB QG62
1153 -27 0.1 1100 @ VE7SL VK4YB QG62
1159 -26 0.1 1100 @ VE7SL VK4YB QG62
1209 -26 0.0 1100 @ VE7SL VK4YB QG62
1225 -25 0.1 1100 @ VE7SL VK4YB QG62
1227 -26 -0.0 1100 @ VE7SL VK4YB QG62
1229 -24 0.1 1100 @ VE7SL VK4YB QG62
1239 -23 0.1 1100 @ VE7SL VK4YB QG62
1247 -26 0.0 1100 @ VE7SL VK4YB QG62
1249 -26 0.1 1100 @ VE7SL VK4YB QG62
1253 -23 0.1 1100 @ VE7SL VK4YB QG62
1255 -28 0.1 1100 @ VE7SL VK4YB QG62
1257 -26 0.1 1100 @ VE7SL VK4YB QG62
1303 -27 0.2 1100 @ VE7SL VK4YB QG62
1305 -23 -0.1 1100 @ VE7SL VK4YB QG62
1307 -25 -0.1 1100 @ VE7SL VK4YB QG62
1309 -23 -0.1 1100 @ VE7SL VK4YB QG62
1313 -25 0.0 1100 @ VE7SL VK4YB QG62
1319 -27 0.0 1100 @ VE7SL VK4YB QG62
1323 -22 0.1 1100 @ VE7SL VK4YB QG62
1325 -25 -0.1 1100 @ VE7SL VK4YB QG62
1327 -24 0.0 1100 @ VE7SL VK4YB QG62
1329 -25 0.0 1100 @ VE7SL VK4YB QG62

My location on the 'wrong' side of Mayne Island requires me to fire directly into a very nearby 600' hilltop, directly in Roger's path.

I'm at the base of the hill on the far right. The large mountains are on Vancouver Island and then open Pacfic.

Later WSPR beaconing, using the new doubler and full power, tends to indicate that a two-way digital QSO should be possible with good conditions. Roger is now able to hear my signal at levels good enough for the JT-9 WSPR QSO mode.

VE7SL	0.475633	-25		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475633	-26		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475632	-23		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475632	-26		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475632	-30		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475634	-28		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475634	-30		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475634	-30		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475633	-28		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475633	-29		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475633	-27		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475632	-28		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475630	-28		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475629	-29		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475629	-31		CN88iu	5	VK4YB	QG62ku	11820
VE7SL	0.475629	-30		CN88iu	5	VK4YB	QG62ku	11820

With the antenna / transverter / amplifier switching unit complete, Roger and I will continue to watch band conditions favorable to the Trans-Pacific path and hopefully exchange signals sometime this fall before the path disappears until next spring. For Roger, near Brisbane, the path peaks for him in the late evening while for me, it means crawling out of bed at 0330 local time to check the prop, hoping to find good signals from down under ... working VK on 630m would be well worth losing a few hours of nightly sleep!

As our sunsets start to come earlier and dawn arrives later and later, the sun's accelerated southerly excursion has brought sudden changes to 630m propagation.





This past weekend's CLE activity saw universally poor propagation as well as weather related QRN from lightning ... but as usual at this time of the year, things can change rapidly. Wednesday's overnight map of my own 630m WSPR activity illustrates why September propagation on LF and MF can often be spectacular and this is with just 65 watts total power output:

courtesy: http://wsprnet.org/drupal/

Among other things, the map indicates the growing interest among U.S. amateurs in the 630m band. Hopefully they won't have to wait too much longer, although I seem to be saying this more often than I would like to. It is of interest to note that even though these were WSPR reports, signal levels at most reporting stations were either into the 'audible CW' levels or at 'JT9 workable' levels ... all stations should be workable once the 630m ham band becomes a reality for all North Americans. Midwinter conditions over the next several years should see an abundance of transcontinental contacts on both CW and on JT9!

The east-west path is the bread and butter direction for interesting possibilities, when it comes to those of us in VE7 land. Normally it only really sets in when geomagnetic conditions are quiet but, as a result of coronal hole streaming, this week's geomagnetic field has been anything but quiet. As John Langridge, KB5NJD / WG2XIQ reported today in his invaluable '630m daily reports':

The geomagnetic field was extremely active, with many reporting periods at storm levels. The Bz is pointing to the South and solar wind velocities are very high, peaking at 700 km/s. This event is significant and I am just glad to see that it is helping and not hurting propagation. When will the bottom drop out? Clearly there is a lot going on here that we do not understand.

With stormy conditions continuing throughout the week, Friday's path to down-under enjoyed some enhancement as well, not unusual when the east-west path is disturbed. VK4YB's 90 watt signal was widely heard by several VE7's (VE7CNF, VA7MM and VE7BDQ) in the predawn hour, as Roger's signal peaked up briefly for several WSPR decodes.

courtesy: http://wsprnet.org/drupal/

As the coronal hole streaming continues, this morning's path to VK seemed even better along with a new antenna at VK4YB favoring the northwest:

12:24      VK4YB      0.475622      -21   VE7BDQ    11844 km      
12:12      VK4YB      0.475621      -22   VE7BDQ    11844 km      
12:08      VK4YB      0.475622      -17   VE7BDQ    11844 km
11:04      VK4YB      0.475622      -24   VE7BDQ    11844 km     
11:02      VK4YB      0.475623      -22   VE7BDQ    11844 km     
10:54      VK4YB      0.475623      -22   VE7BDQ    11844 km

12:28      VK4YB      0.475626      -21    VE7SL       11820 km     
12:24      VK4YB      0.475625      -23    VE7SL       11820 km     
11:54      VK4YB      0.475623      -25    VE7SL       11820 km     
11:04      VK4YB      0.475623      -23    VE7SL       11820 km    
11:02      VK4YB      0.475625      -26    VE7SL       11820 km     
10:54      VK4YB      0.475626      -21    VE7SL       11820 km

11:22      VK4YB      0.475614      -28    VA7MM      11872 km     
11:04      VK4YB      0.475614      -28    VA7MM      11872 km     
11:02      VK4YB      0.475615      -33    VA7MM      11872 km     
10:54      VK4YB      0.475615      -26    VA7MM      11872 km

I should mention that the other VE7 stations are all operating from noisy suburbs near Vancouver ... clearly fine examples of what can be done on 630m under less than ideal operating conditions and by paying close attention to system optimization. Please don't let living in the city stop you from enjoying the mysteries and challenges that our latest ham band has to offer ... as mentioned earlier, there is still much to be learned about using this band at amateur radio power levels and small backyard antennas. How exciting is that!

This past weekend's CLE saw typical summer conditions ... poor propagation and lots of lightning noise. The MF NDB band was noisy on all three nights, almost everywhere.



As usual, I put my Perseus SDR to work, recording the assigned frequency slots and came away with 24 catches, including some of the 630m experimental stations.

28 11:00 260.0 YSQ Atlin, BC, CAN
27 08:00 260.0 AP Sedalia, CO, USA
27 07:00 261.0 7J Forestburg, AB, CAN
27 09:00 263.0 OAY Norton Bay, ALS
27 08:00 266.0 VR Vancouver, BC, CAN
27 09:30 266.0 SL Turner, OR, USA
27 09:30 266.0 SAA Saratoga, WY, USA
27 09:30 266.0 ICK Annette Island, ALS
29 12:00 266.0 BZ Bozeman, MT, USA
27 09:30 268.0 ZWL Wollaston Lake, SK, CAN
27 12:00 269.0 ZW Teslin, YT, CAN
27 09:30 269.0 YK Castlegar, BC, CAN
27 09:30 269.0 UDE Delta Beach, MB, CAN
27 08:30 512.0 HMY Lexington, OK, USA
27 08:30 515.0 SAK Kalispell, MT, USA
27 08:30 515.0 CL Cresent Beach, WA, USA
27 08:00 521.0 INE Missoula, MT, USA
29 11:30 524.0 MNL Valdez, ALS
29 11:00 525.0 ICW Nenana, ALS
27 11:00 529.0 SQM Big Level Isl, ALS
27 07:30 473.8 WI2XJQ Edmonds, WA
27 07:30 475.0 VA7MM Coquitlam, BC
27 07:30 475.2 WG2XSV Vancouver, WA
27 07:30 477.6 VE7CNF Burnaby, BC
29 13:00 474.0 VE7BDQ Delta, BC

One nice surprise was the strong showing from Alaska towards dawn on night three. Not a peep was heard from the mainland Alaskans on the first two mornings and I was fully expecting to find the same thing on Monday morning but that was not the case.

The last time that this frequency range was covered was during CLE 191 in February, 2015 ... prime winter conditions. At that time I logged 42 beacons compared to 24 this time. The furthest one heard was 4023km away while this time the best was at 2873km. My average distance back then was 1670km compared with 1046km this time.

From Brian Keyte's (G3SIA) summary posted via the Yahoo ndblist Group, come these stats:


In last weekend's CLE we were listening for NDBs in the range
260 - 269.9 kHz and above 440 kHz, including several Amateur beacons.

Here are the combined results tables for listeners away from Europe,
attached as CLE210a5.xls. Soon they will also be available
from the CLE page http://www.ndblist.info/cle.htm

19 Reporters
37 Radio Countries heard
83 different beacons heard
212 reports supplied

Most Heard NDBs:

Rprts kHz C/S Location Cou.
=============================================
9 512 HMY Lexington OK USA
9 260 AP Denver CO USA
9 521 INE Missoula MT USA

8 266 VR Vancouver Lulu Is. BC CAN

7 269 YK Castlegar Brilliant. BC CAN

6 515 SAK Kalispell Smith Lake MT USA

Missing NDBs? (not including Amateur beacons)

The following list shows NDBs with 6 or more loggings in
the similar event in Feb. 2015, but not reported this time.
They may have been withdrawn, changed frequency or ident,
be temporarily out of service or just be inaudible due to conditions.

Then Now kHz C/S Cou Location
=====================================
13 0 260 AVZ USA Terrell TX
11 0 260 BVQ USA Glasgow Beaver Creek. KY
6 0 260 GHJ USA Gastonia NC
9 0 261 2H CAN Lebel sur Quevillon QC
6 0 261 D6 CAN Fairmont Hot Springs BC
7 0 263 JDN USA Jordan MT
6 0 263 LB USA Angleton Lake Jackson TX
10 0 264 ZPB CAN Sachigo Lake ON
6 0 269 AR USA New Iberia LA
11 0 269 CII USA Choteau MT
6 0 269 PK USA Park Rapids MN

10 0 515 OS USA Columbus OH
6 0 521 GM USA Greenville SC
6 0 521 TO USA Topeka KS

Overall conditions should be much better by this time next month as September propagation can often be superb, as long as the lightning activity has died down. Over the past few seasons I have noticed that it seems to be hanging in a few weeks longer than in the past, hopefully not a long term trend but with all of the bizarre weather changes we are seeing, I wouldn't be surprised if that were the case.

Over the past week, I've been playing with my 630m transverter summer project.





It's not the normal type of transverter that would produce a signal on 630m (~475kHz) but rather, one that will produce a signal on twice this frequency. My630m amplifier, using switching FETs, was designed and built with a 'divide-by-two' input circuit, to allow for greater frequency resolution when first constructed as a 2200m system. I really don't want to modify the transmitter and prefer just to be able to unplug my DDS and plug-in the transverter, allowing me to run WSPR, JT9 and several other digital modes when needed.

So far I've not been able to get the transverter to produce the desired low voltage 950kHz squarewave output, although I'm closer than when I began the troubleshooting.

My circuit is basically a G3XBM 630m transverter, without the FET final amplifier. Instead, the driver feeds a  full-wave rectifier frequency doubler for 630m, designed and published a few years ago by Jay, W1VD. Although I can get a squarewave end result, I think harmonics creeping into the process earlier down the mixing chain are causing non-symmetry in the output.









I'm using a 3.200MHz crystal oscillator with low level RF drive from my IC756PROIII transceiver at 3.675MHz feeding an ADE-1 double-balanced mixer in order to utilize the 'difference' frequency, 475kHz.

3.2MHz signal out of oscillator buffer stage

475 kHz signal out of mixer stage

Signal out of 'squarer' stage

Signal out of full-wave bridge

Signal out of LPF

Asymmetrical squarewave from 4046 output

I've tried a 3-section LPF with a cutoff of ~600kHz between the mixer output and the next stage, trying to knock down the 'sum' frequency of 6.875MHz and any crystal harmonics but have since replaced this with a 630m diplexer at the mixer output to pass anything below 1MHz to the squarer and anything above 1.5MHz to ground. I'll keep playing with it ... until it works as it should or I have no hair left to pull out. I may also just rebuild the circuit, Manhattan-style, with normal sized parts, making it much easier to change or modify as I need. The scope grabs shown above are with the diplexer in place at the mixer output. It seems like something in the full-wave frequency doubler is amiss. I've looked at T1, the bifilar transformer several times but don't see anything odd but that's the stage where things seem to go south. Maybe it's an impedance matching-thing, something I'm yet uncomfortable with when it comes to properly matching various stages.

I also now realize that the section of transverter I have chosen will require post-mixer filtering, not shown in the schematic. Not using the last stage (FET PA) and its associated filtering, has no doubt caused more harmonics to appear in the output than anticipated. If I redesign and rebuild, I will add an LPF after the crystal oscillator as well as at the RF input port and pay more attention to post-mixer filtering.

Another route to try, rather than the W1VD doubler, may be this 4069 IC doubler or a similar 4011 doubler.

Although the project outcomes have not yet been achieved, the process has been a positive one in a couple of respects and well worth the time spent so far.

I have learned that working with the 1206-sized SMT parts is much easier than suspected and in fact, populating the board with these tiny parts was a lot of fun.  The 1206-sized parts are at the 'large' end of the SMT size-spectrum ... rest assured I won't be going any smaller, at least for now.

My previous taste of SMT-construction was many years ago, when I built a small 40m QRP transceiver using seventy-two SMT parts ... it was an inexpensive kit from one of the QRP clubs. Happily, it worked with no problems but I found the process tiring and laborious and only soldered a few parts on the board each day until it was completed. The present experience was the exact opposite as I found it a very enjoyable experience ... I'm really looking forward to doing more SMT construction in the future.

The other positive outcome was knowing that my PCB design process can work well with the narrower lines, pads and much smaller IC footprints. I still design my boards using MS Paint and have always been happy with the ease at which it works. I know many might scoff at MS Paint but it really is a very versatile little program, with a short learning curve, unlike many of the more sophisticated PCB design programs.

Although I will work with SMT again and, similar to this project, I'll not be concerned about shrinking the board too small, although I'll work towards that goal. My main reason for trying a homebrewed SMT board was to see if I (my eyes) could still handle it and since so many parts are no longer available in the 'normal' size we have been used to for the past several decades ... particularly obvious when trying to source IC's in the good old DIP package. I am seeing a lot of 'obsoletes' pop up for some of my wanted chips, as the larger DIP packages are no longer in as much demand.

And one more positive outcome. I used the project as an excuse to purchase a new soldering station ... one that I had been lusting over for a few years as it is very SMT-friendly compared to my old Weller clunker. It also has an electrically isolated tip, unlike my Weller. The Hakko FX-888D turned out to be everything I had hoped and was no doubt part of the reason that I found the SMT process so enjoyable.

Add caption

If you haven't tried building with these smaller components, don't be afraid to test the waters. I have no idea how long our 'normal-sized' leaded parts will be readily available but I now know that their eventual demise won't slow me down when it comes to homebrewing.

'VR' - 266kHz

This coming weekend will see another CLE challenge, this time in the MF band from 260 - 269.9 kHz plus 440 - 1740 kHz.





'CLE's' are 'Co-ordinated Listening Events', and NDB DXers around the world focus their listening time on one small slice of the NDB spectrum ... but this time around, the range has been expanded.

The lower frequency range covers one my very strong locals, 'VR' on 266 kHz. 'VR' is an outer marker approach to Vancouver International's 'two-sixes' and is located a few miles east of the main runways in a farmer's field. Although running just 50 watts, it is widely reported (as far east as North Carolina), probably due to the excellent soggy ground beneath its somewhat unusual delta-shaped loop.

From CLE coordinator Brian Keyte (G3SIA), via the Yahoo ndblist Group, comes the following reminder:

Hello all,

Our end-of-August Co-ordinated Listening Event will soon be here.
We'll be hunting for normal beacons in two contrasting frequency ranges
and there is also the possibility of hearing several amateur beacons.
As always, first-time CLE logs will be extra welcome.

Days: Friday 26 August - Monday 29 August
Times: Start and end at midday, your local time
Frequencies: 260.0 - 269.9 kHz
plus: 440.0 - 1740.0 kHz

These are interesting frequencies, the same ones that we last used for
CLE191 in February 2015 when 45 of us joined in.

Many of us should be able to hear beacons in both ranges, though Europe
only has a handful in the '260s'. From 440 onwards, North America has a
few, mostly around 520 kHz, while Eastern Europe has several beacons
and some regular UNIDs. Some of the NDBs can also be found among
Europe's Medium Wave Broadcast Stations.

Many of us are within range of amateur beacons on frequencies mainly
around 474 - 478 kHz. We'll be listening for ANYTHING OPERATING IN
BEACON MODE, preferably with normal speed Morse.
(We ask operators who sometimes use QRSS, PSK, WSPR, etc.,
which need software to receive them, to PLEASE CHOOSE THE
SIMPLER MODE during the CLE so that we shall all be able to
receive them and make reports).

Please look out for my final details with advice about log-making, etc.
in a few days.

73
Brian
----------------------------------------------------------
From: Brian Keyte G3SIA ndbcle'at'gmail.com
Location: Surrey, SE England (CLE co-ordinator)
----------------------------------------------------------

These listening events serve several purposes. They:

• determine, worldwide, which beacons are actually in service and on-the-air so the online database can be kept up-to-date

• determine, worldwide, which beacons are out-of-service or have gone silent since the last CLE covering this range

• will indicate the state of propagation conditions at the various participant locations

• will give you an indication of how well your LF/MF receiving system is working

• give participants a fun yet challenging activity to keep their listening skills honed

Final details can be found at the NDB List website, and worldwide results, for every participant, will be posted there a few days after the event. If you are a member of the ndblist Group, results will also be e-mailed and posted there.

The very active Yahoo ndblist Group is a great place to learn more about the 'Art of NDB DXing' or to meet other listeners in your region. There is a lot of good information available there and new members are always very welcome. As well, you can follow the results of other CLE participants from night to night as propagation is always an active topic of discussion.

If you are contemplating getting started on 630m, listening for NDBs  is an excellent way to test out your receive capabilities as there are several NDBs located near this part of the spectrum.

You need not be an ndblist member to participate in the CLEs and all reports, no matter how small, are of much value to the organizers. 'First-time' logs are always VERY welcome!

Reports may be sent to the ndblist or e-mailed to either myself or CLE co- ordinator, Brian Keyte (G3SIA), whose address appears above.

Please ... give the CLE a try ... then let us know what NDB's can be heard from your location! Your report can then be added to the worldwide database to help keep it up-to-date.

For the past several months I have been beaconing overnight on 630m WSPR mode. I've been using a new transverter designed by Roger Croft (VK4YB) and Ralph Loveday, in Queensland, Australia. One unit was sent to me for beta testing and I have been hammering it as hard as I can ever since setting it up in the spring ... no problems have been experienced after several months of 12 hour nightly beaconing punishment. Nightly signal reports often range from Hawaii / Alaska and eastward to New England ... all during the 'not so good' summer band conditions.

Now that beta testing is complete, production units are now ready for distribution from Monitor Sensors, a family environmental-sensor manufacturing company of which Roger is Governing Director.

The introduction of the VK4YB 630m Transverter presents another new option for those wishing to get on the band, or in the case of American amateurs, to get prepared for the band ... soon expected to be implemented in the U.S.

When I first started using the test unit provided, I was immediately impressed with how simple it was to set up and to get operational. It sits inconspicuously beside the main station's transceiver, taking up less space than the typical station speaker unit.

One usually associates 'transverter' operation with a rat's-nest of cabling or re-cabling to accommodate the new addition. The transverter arrived with all necessary cabling, even a nice Anderson power pole connector to connect the user-supplied 12V power source. A second pair of 12V contacts is also available for sharing with other station needs. One feature that I quickly appreciated was the dual RCA jack on the rear panel for controlling the transverter's PTT keying line. With my transceiver's PTT line already being used for another purpose, it was simply a matter of plugging-in (cable supplied) and sharing the line with the second jack ... no need for unplugging or using an external adapter to split the PTT line. Switching from 630m to normal HF operation is simply a matter of turning the transverter 'off' ... all HF operations are back to normal with antenna routing taken care of. There appears to be a lot of thoughtful engineering packed into this little box.


A look under the hood shows a well-planned and efficient use of space as seen in this pre-production prototype shown below. If Collins Radio were to manufacture a 630m transverter for the military, I can't imagine it being any better than this!

prototype board under test

Although rated at 50W output, my transverter produces ~ 70W output when run at 12.6 volts. More output can be realized at higher voltage, up to as much as 16 volts. Power is generated with six carefully-matched Lateral MOSFETS, three aside, in a parallel / push-pull configuration.

"... we carefully match the FETs into three pairs. Each pair is matched to its opposite number but the pairs are chosen so 2 have low gain, 2 have mid gain and 2 have high gain. This improves the IPs and also the harmonics. With matched FETs we are getting the 2nd harmonic at typically -60dB. That's 10dB better than the stringent FCC requirement." 

Roger's unit is running at 16 volts and produces 90W output, with his 630m WSPR signal being the one most often heard in North America from down under.

The transverter's multi-colored screen combines with a multi-function menu, allowing a visual on-screen display of numerous parameters such as RF output power, DC supply voltage and current draw, SWR, exciter drive power, heatsink temperature, graphic SWR display and various warning screens.

The transverter requires 3-5 watts of 160m drive from the station transceiver for full output power. Built-in safety circuits prevent overdrive from causing any damage. Similarly, transmitting into a high SWR or with no antenna connected is no cause for concern. Temperature sensors will trigger shutdown should the heatsink rise above 100 degrees C. Software also prevents out-of-band transmission.

This is a microprocessor controlled linear-transverter. This means that operating system software can be readily updated (via the supplied micro USB cable) as new features are implemented. It also means that any mode your transceiver is capable of operating on can be produced on 630m. At present, the most popular modes on the band are WSPR, CW and JT9 but I suspect this order may change once the band is opened up in the U.S.


A shortened eight-page Operator's Manual can be downloaded from the Monitor Sensors web site but units will ship with a more comprehensive 22-page manual. For more information regarding pricing and shipping, please contact Monitor Sensors here. For technical questions, please contact Roger here.