Lightwave Scatter

Looking down the road at possible future 'clear-air scatter' or 'cloudbounce' lightwave tests with stations (VE7CNF and VA7MM) on the other side of Georgia Strait, I spent a few minutes breadboarding a more stable modulator for my lightwave system.


As it is at present, the modulator consists of a 556 tone generator, capable of either a steady tone for CW keying or a two-tone FSK 'beaconing' signal used to help the other station in aiming alignment.

For the slow QRSS CW narrow-bandwidth modes required for the scatter tests, I've always known that a tone which is much more stable and of precisely known frequency would be needed. The tone from the 556 does well as an aural CW keyed tone but would probably be all over the place when viewed in a very narrow-bandwidth and not nearly as stable as it sounds by ear.

The little modulator uses a 4500 KHz crystal (pulled from a old VCR several years ago) in a 4060 oscillator-divider. In this case, output from the chip is taken from either the 'divide-by-8192' pin 2, which outputs a precise frequency of 549 Hz or from the 'divide-by-4096' pin 1, which outputs a frequency of 1099Hz.

courtesy G3XBM: http://g3xbm-qrp.blogspot.ca/search/label/nlos

This tone is then used to drive an IRF 540 power MOSFET which controls current through the 1W Luxeon Deep Red LED in the transmitter. The 4060 modulator will be keyed via a QRSS software keying program that I have used for many years to key my LF transmitter.

The lightwave receiving station will look for the QRSS audio signal with an audio spectrum viewer such as Argo or Spectran. The ability to make automatic overnight screen captures will allow the receiving operator to get a good night's sleep while the system diligently watches for any traces of a signal.

An example of a strong signal capture showing a repeating "SL" identification is shown below, as it would appear in a perfect world. In this case (QRSS3), the short 'dots' are 3 seconds long while the 'dashes' are 9 seconds.


Huge signal gains (the ability to dig into the noise for signals) can be had by slowing things down and using narrower receiving bandwidths. Just going from a normal 12WPM speed CW (aural copy) to QRSS3 yields a gain of ~15db. At QRSS10 (10 second dots), an additional 5db is gained while slowing to QRSS60 (60 second dots), a whopping 28 db over 12WPM CW is gained!

Of course all of this extra 'hearing power' comes at a cost and in this case, the cost is 'time'. On an overnight of automated computer monitoring, time is not much of an issue ... it only becomes critical in 'QSO mode' when some QRSS QSOs can take several hours to complete. In any case, it will be interesting to see if any traces of lightwave signals will show up while bouncing around in the clouds.

The Georgia Strait scatter tests will not take place for some time but in the meantime, I hope to do some local tests here, from one side of my island to the other but will build a new portable receiver for these tests and leave my main system intact.

Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

Creating open-source ham radio hardware with Kickstarter

When I started my company last year, it was mainly set up as a design consulting outfit to pick up a few jobs on the side.  At the end of 2014, it became much more when I decided to plunge full-time into my own work.  At the time, one of my respected friends and colleagues, Don Powrie of DLP Design, said to me that the only way to make consistent money is to have a product line rather than rely on consulting work.  I’ve been thinking of how to bring that to market ever since.  I could certainly design some familiar products to me, but they would get lost in the plethora of similar items.  I needed something unique.

I only recently purchased a Raspberry Pi 2 and started checking out what I could do with it in the ham radio world.  I picked up a ThumbDV from NW Digital Radio and got that software running on the Pi.  The trouble was I only had a 1A USB power supply (the one pictured in the Kickstarter video).  Things just weren’t acting right and I started thinking of the best way to get more power to this wonderful platform.  As part of my consulting work, I recently designed a Power over Ethernet adapter for another platform and figured I’d do something similar to launch a product.  Someone had just announced a PoE to Pi power board.  I don’t recall if it was on Kickstarter or not, but I figured it best not to duplicate that effort.  While doing a little shack cleaning and trying to consolidate some wires, I asked myself, “Wouldn’t it be nice to use the Anderson distribution panel right to the Pi?” and the light turned on!  THERE was my unique product.
pi-go-1

I started out with a 5V @ 5A design.  I drew the schematic and completed the PCB layout and started to check pricing and availability of the parts.  Most everything was available at Digi-Key, and the Anderson Connectors from Mouser, but the total was getting close to where I wanted the selling price to be.  For a $35 computer, I couldn’t justify a $70-$80 power board!!  The DC-DC converter also had a very large ground pad for heat dissipation.  I wanted this project to be able to be hand-soldered and started wondering about that large pad.  That design got scrapped and I started looking for another buck converter.  There were several TI and Linear products I considered, but they would have required a reflow oven – either with a center pad, as a BGA, or leadless formats.  Then I found the Alpha & Omega AOZ1031AI.  This is a 8-pin SOIC without any special pad.  The only heat-dissipation suggestion was that pins 7 and 8 do not have any thermal relief, but connect fully to the surrounding plane.  I selected larger commodity parts (0805) that could be seen without a microscope and created the layout, and all parts were in stock at either Digi-Key or Mouser Electronics.  I got everything on order, and even managed to get a couple free PCBs from Pentalogix.  I had attended a Pentalogix-sponsored Cadsoft Eagle webinar at Newark and the perk was a code for two boards.  I just had to cover shipping.

I got everything in and soldered together.  The only issue I ran into was my switch selection.  I used a footprint from one source, and the switch leads were just a little wide for the pads.  First thing was the multi-meter test to make sure the PCB (both bare and assembled) didn’t have any direct shorts.  Next up was the infamous “smoke test”.  Plug it in and hope it doesn’t go “Pfffffft!”.  Success! (I have a bench supply that I started at about 6V and limited the current to 0.5A just in case).  I checked input and output voltages and all was well.  The voltage was then ramped up through the specified range with constant 5V output.  All this was done with no load.  Once I was satisfied that the 5V was stable, I unplugged everything and put it on the Raspberry Pi.  I set the bench supply for 10V and turned it on.  Yes!  The Pi booted and ran normally.  Time for a beer!

I did other tests:  Let it run for 8 hours (check), ramp voltage from 6 to 18V input (check).  At 7V input, the Pi kept rebooting.  At 8V, it was solid – well past the design spec.  Same at 18V.

Next up was the load test.  With 2A going direct to load resistors, I was still able to run the Pi with all four USB ports occupied.  I even dipped the supply to 8V.  The bench supply showed about 1.8A output.  Based on an approximate 80% efficiency of DC-DC converter, I calculated I was drawing about 3.5A on the 5V side – a little past its limit, so backed off the load.  I’ve been running this directly from my radio supply now for several days, and the Pi keeps chugging along.

Going the Kickstarter route wasn’t exactly on my mind when I came up with the product.  Much of my career has been with smaller companies where we all wear many hats.  I already had multiple products that I had taken from concept to full production.  Most of these were one form of communication board or another for the earlier IBM PC and related clones.  I was originally going to just launch a web store site, but was having trouble with how to market the concept.  I started looking at my available funds and figured a good portion would get utilized without much word getting out with a normal store-only approach.  That’s when the Kickstarter site popped in my head.  I looked around for similar projects and decided to give it a go.  I seemed to have everything in place…. except the video.  I’d rather be behind than in front of a camera, so I worked up a script that I hope is fun yet catchy and started recording it.  I took a bunch of pictures and found a few on the ‘net (CC licenses)  This entire project is created in Ubuntu Linux from the design in Eagle to Audacity, Gimp and OpenShot for the media.
pi-go-2

I’m a believer in open-source hardware and software.  This project will be published in the coming days, probably on GitHub.  Eagle uses XML design files, so version control should work just fine.  I still need to write the manual, but everything will be made available as soon as I get the proper README and LICENSE files in place.  All of my work for this project is published under the Creative Commons Attribution and Share-Alike license.  The hardware itself is published under the TAPR Open Hardware License.

As an aside, in looking for the Anderson Powerpole connectors, I ran into a disturbing find:  About half of the connectors in my shack stock look like they’re fake connectors and housings.  Many of them have the “o” missing from the word “POWER” in the stamping.  A few have “POWER” upside-down when compared to a genuine housing.  There are color and fit differences as well as corroded and inconsistently sized pins.  No wonder some my cables were nearly impossible to assemble.  I attached a picutre.  The left side shows genuine Anderson Powerpole parts purchased from Mouser Electronics, an authorized distributor.  The right side shows what I have in my shack stock that I picked up from various hamfests and other sources.  Be sure to only get all parts only from authorized sources.  I almost never trust eBay or Amazon for this type of stuff.

Bob Recny, N8SQT, is a special contributor to AmateurRadio.com.

Colorado 14er Event: Mount Antero (W0C/SR-003)

For the 2015 Colorado 14er Event, Joyce K0JJW and I activated Mount Antero (W0C/SR-003) on the 2m and 70 cm bands. Alan NM5S joined us on the summit, operating mostly HF plus some 2m fm.

We took our Jeep Wrangler up the moderate 4WD road and parked at 13,800 feet. This makes for a very manageable hike to the 14,269 foot summit. Of course, you can always choose to start the hike from lower on the mountain, but you’ll end up walking along the road. This web site provides a good overview of the 4WD road.  The 14ers.com web site and summitpost.org are additional sources of summit info.

Here’s a short video of our operation on the summit.

Here’s the K0NR log on the 2m band, fm and ssb:

August 2, 2015 K0NR Log, time in UTC
15:09     144MHz     FM     K0JJW     
15:13     144MHz     FM     W0CP     
15:16     144MHz     FM     KC5JKU     Mt Elbert 
15:17     144MHz     FM     KD0WHB     Grays Peak
15:21     144MHz     FM     N0XDW      Pikes Peak
15:37     144MHz     FM     KD5HGD     Mt Elbert 
15:42     144MHz     FM     KD0MRC     
15:42     144MHz     FM     KE0DMT     
15:44     144MHz     FM     NQ0L       Franktown 
15:45     144MHz     FM     KE0EUO     Mt Democrat 
15:46     144MHz     FM     K7SO       Mt Democrat 
15:50     144MHz     SSB    KD0YOB     W0C/PR-005 
15:53     144MHz     SSB    W0BV       Buena Vista
15:53     144MHz     SSB    K0YV       Buena Vista
15:57     144MHz     SSB    W0STU      Monument
16:06     144MHz     FM     KD0WHB     Torreys 
16:13     144MHz     FM     KI6YMZ     Mt Elbert 
16:19     144MHz     FM     KE0EKT     Mt Elbert 
16:29     144MHz     FM     WZ0N     
16:29     144MHz     FM     KE0DAL     
16:31     144MHz     FM     WO9S     
16:33     144MHz     FM     K0UO     
17:10     144MHz     FM     KD2FHB     Pikes Peak

It was a great day on the mountain with quite a few Summit-to-Summit (S2S) SOTA contacts. See you next year on a Colorado mountaintop!

73, Bob K0NR

The post Colorado 14er Event: Mount Antero (W0C/SR-003) appeared first on The KØNR Radio Site.


Bob Witte, KØNR, is a regular contributor to AmateurRadio.com and writes from Colorado, USA. Contact him at [email protected].

Ham College episode 8

Ham College episode 8 is now available for download.

Ham College, the new show for those new to the hobby and those wishing to get into Amateur Radio.

In episode 8 we discuss the radio bands available to hams. More questions and answers from the Technical class question pool. We also tell you how you can win an Icom T-shirt and cap and about the AmateurLogic.TV 10th Anniversary contest where someone is going to win a nice HF transceiver and accessories.
55:14

Download
YouTube


George Thomas, W5JDX, is co-host of AmateurLogic.TV, an original amateur radio video program hosted by George Thomas (W5JDX), Tommy Martin (N5ZNO), Peter Berrett (VK3PB), and Emile Diodene (KE5QKR). Contact him at [email protected].

Sparking-Up On 2200m

I haven't been on 2200m (135.7 - 138.8 KHz) for some time ... my last transmissions on this band were almost three years ago. The recent acquisition of the 630m band has refocused a lot of my attention but Canadian activity has never been very high on the real 'top band'. Hopefully when the U.S. gets the 2200m band soon, activity will increase on both sides of the border.

An e-mail alert from Toby, VE7CNF, on the other side of Georgia Strait, indicated that everything was ready for a two-way test on 2200m and he was looking for his initial contact on the band. Having not been on the band for such a long time, some review of my 'tune-up' procedures were in order as well as the need to burn out the spider webs in my outdoor loading coil.

Since being on 2200m, I had modified my 2200m kilowatt transmitter so that it could also be used on the new 630m band. To change bands from 630m back to 2200m, I needed to swap the frequency-sensitive power divider back to 2200m as well as re-set the DDS frequency.

2200m Power Divider
Setting my DDS to the correct control frequency and keying the driver stage revealed no sign of a signal on 137.779 KHz. This was puzzling and several re-checks turned-up no reason for the problem ... it seemed as if there was no signal from the DDS into the transmitter. I set everything back to 630m, just to confirm that there wasn't a more serious problem but everything worked just fine. It was then that I realized my error.

When modifying the transmitter, three years ago, I had also changed the transmitter's input frequency divider from a 'divide-by-four' to a 'divide-by-two' scheme. My original system on 137KHz started with a DDS frequency in the 5.48MHz range and then was divided by ten before being fed to the transmitter's input where the 548KHz signal was then divided by four. Using a higher DDS frequency allowed for greater frequency resolution at 2200m and allowed for very small frequency adjustments across the band. I would have kept the same system for 630m except that my 'divide-by-ten' chip was not very happy at 18MHz and refused to divide.The newer system now only allows me to move around the band in 4.5Hz steps. It's really not much of a problem as there is presently a minuscule amount of activity in Canada on 2200m, but as previously mentioned, this may change when U.S. amateurs gain access to the band.

Having sorted out my transmitter problems and confirming that all was well, the next task was to check antenna resonance and impedance matching as it would more than likely not be the same as I had left it. A low-power check using the 'scopematch' indicated that both resonance and impedance were not optimized. Tapping down on the loading coil by one-turn took care of resonance while adjusting the impedance tap in my matching transformer to its lowest value (see matching scheme below) resulted in a near perfect match on the scope.



I'm guessing that the resonance change was due to the recent heavy trimming of the 80' Balsam that supports one end of my 'inverted-L' and large three-wire flatop.




The tree's crown had previously been very dense and some of the branches were almost touching the flatop. The close proximity always made me worry about possible flashover at the antenna ends as voltages here would be several kilovolts. Removing much of the wet green tree branches directly beneath the flatop also likely contributed to the slight change in resonance.


Impedance Matching Transformer On TV Flyback Cores
The change in impedance to a lower value may have been due, in part, to the removal of the tree branches as well but more likely it was reflecting the change in my ground system. When I had last been on (in mid-winter), the ground was well saturated and the water table at normal heights. The present conditions are just the opposite as things are drier than they have ever been and the water table has certainly dropped substantially.

The sked with VE7CNF went smoothly and it was nice to see another new Canadian station taking an interest in the band, along with all of its challenges. Toby's 200W signal was a solid 559 here even with his small antenna system yet to be fully optimized. As well, he was bothered by heavy switching-power supply QRM from a nearby neighbour. Unfortunately, such noise sources seem to be increasing in numbers and are making operation on LF, already a big challenge, even more challenging. Toby has taken up the challenge with enthusiasm and has now had contacts on 2200m well as on 630m, adding to the ranks of active VE7's on LF and ... demonstrating yet again that amateurs can enjoy the LF bands with small 'backyard' antenna systems. Don't let living in the city be a reason to avoid our new LF bands.


Wouldn't it be great to see some activity from our neighbours in VE6 or VE5, both easily workable on both bands from the west coast... maybe you're up to the challenge!

Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

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