One Orbit Closer

I received my Arrow antenna today. It is trivial to assemble and seems really well designed and built.

Knowing I would be using two radios to achieve duplex operation, I ordered it without a duplexer. However, I failed to order any BNC cabling with it and I don’t have any BNC connectors to make the necessary cabling, so, I packed it down into it’s handy portable bag, ordered what I will need and began the next stage of waiting.

And Sputnik Was His Name-O

I received my MFJ-1866 discone antenna. Assembly was trivial, basically screw all the elements into the right holes, short ones on top, long ones on bottom. It looks as much like Goddard’s early work as an antenna.

I mused that it looked like Sputnik and my wife has already called it Sputnik (as in, “Are you going to move Sputnik out of the bedroom?”

Sputnik it is.

I did screw up my order, though. I had toyed back and forth with what coax I was ordering and ended up with the unintended product in my cart in the end. I ordered a 50′ jumper of 400MAX, which is awesome cable, but it’s 1/2″ diameter stuff and I had intended to get much thinner RG-8X as there will be a 6-8 foot bit of it showing… INSIDE THE HOUSE! It’s not like I’ll never have a use for the 400MAX, so I’m conflicted on whether to jump through the returns hoops, but delays delays delays. I *may* have some RG-58 laying about already, leftovers from a trapped dipole antenna project I started at the old house. There is a box in the storage container that says “ANT TRAPS” that has been misinterpreted by more than one person.

I did connect the discone with a short cable to the SDRdx. Even sitting on the floor in the spare bedroom, it improved reception over the Comet SMA ducky that was used before and I was able to pick up a few 70cm repeaters. Receiving on 2M was a problem, though.

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Note the terrible birdies. The receiver and antenna are just a few cubits from my LAN gear, most notably a Cisco PoE switch powering a few Polycom phones. As that is my day job and I work from home, they must remain. However, my personal laptop kinda lives in that room for now and it was the easiest (read: least nanny state) to install the software on. All this will get better when it is moved away from that cluster.

Fun fact, the screen capture above is from my phone, running the Android version of Microsoft’s Remote Desktop, connected to the laptop running SDRuno. Mouse operations are a little weird, but it otherwise works just fine.

Long term, I’m thinking the discone may go into the attic, with the *thin* coax coming down into the kitchen; we have a DirecTV coax coming down in an unobtrusive corner. Then I can kinda shoehorn a little VHF/UHF/SWL station in that corner where we have a PC or two, using the SDR and my FTM-100DR with an antenna switch. RDP lets me work it from largely anywhere else. I can also play with putting the FTM-100 on WIRES-X at that time. The trouble with evil plans is that they just keep comin’.

My Arrow antenna has not shipped yet. The order confirmation said “Your order is estimated to ship within five business days. Orders usually ship within two business days.” Today is the evening of 7th business day, not even counting the day I ordred, so it’s late, but probably not late enough for me to reasonably complain. :/

Sat On A Light

There have been amateur radio satellites in orbit for literally my entire life. Hams were in space only four years behind the Russians, less than a year before I was born. It also was the first satellite deployed as a secondary payload from a primary launch… ejected using a spring purchased from Sears. Remember, it doesn’t *have* to be expensive to work, but if *my* life is in the balance, I’d rather it was. It should at least be a McMaster-Carr spring…

The first time I heard of amateur radio satellites, I presumed that was an exotic part of the hobby that only the ham elite (read: rich hams) would ever have access to. I think a big part of that was the math needed to predict orbits and the presumption that exceptional precision would be needed. Turns out that it’s not particularly difficult, but neither is it trivial. Johannes Kepler figured it out on paper by candlelight. With the advent of personal computers in general and the ubiquitous smart phone in particular, much of that number crunching is a few finger swipes away. Now working satellites seems to be reduced to learning the idiosyncrasies introduced by chasing a slowly tumbling 1/2 watt transceiver 300 miles away while it flies by at 17,000 miles per hour. Piece o’ cake.

I exaggerate the difficulty, though not the conditions. As rough as that sounds, it can be done with as little as a handheld antenna and a dual band HT, assisted by some tracking software.

Armed with some basic tips obtained from various YouTube sources (which I will detail below) and an Android app, I was able to pick up the beacon on a couple of satellite passes with only my existing base station gear, an Icom IC-7100 and a Diamond X-300A. This is a fixed base station antenna optimized for transmitting and receiving towards the horizon.

Undocumented Satellite Beacon Pass

Note that I am chasing the Doppler frequency shift, which is one of the two biggest idiosyncrasies. Satellites are moving fast enough for Doppler frequency shift to matter. Most satellites operate crossband, with an uplink that is either 2M or 70cm and a downlink that is the other band. Obviously both are affected by Doppler shift, but as it is a percentage effect, the higher the frequency, the larger the effect, so 70cm is more affected that 2M.

Having now heard such a birdie tone intentionally, I am reasonably sure that I have accidentally heard them before and perhaps just didn’t realize it was a satellite! How simple must it be if I can do it accidentally?

I have tried a couple times since then to hear QSOs and I can *just* tell there *might* be something there, maybe the tiniest bit of a beat tone tuning the range, but not enough to pull out of the noise.

To give myself the best chance of success, I ordered an Arrow 146/437-10WBP antenna. This is a 3 element 2M and a 7 element 70cm on a shared boom. The BP suffix is the split boom (back pack) version which breaks down easily for transport, so I also got the carrying bag for it. At this writing, it has not yet arrived. Being a handheld antenna, it helps with the other major idiosyncrasy, polarization fading. As the satellite tumbles in microgravity, the antennae are changing orientation and being able to rapidly change polarization is one strategy for coping with that. Antennas built with circular polarization is another.

My plan to start is to try FM using two handhelds. I have 2 each Baofeng UV-5Rs, RD-5Rs and an Icom ID-51, so I can mix and match as necessary.

I also used this as an excuse to picked up an SDRPlay receiver, the SDRdx model. I have nearly purchased an SDRPlay receiver a few times over the last few years, but never pulled the trigger. I’m not sure if it will actually be used for satellites or not, but I imagine I will at least experiment with it. Plus, everything else you can do with an SDR 🙂 Not necessarily only for satellite use, but for very wideband SDR reception, I got an MFJ-1866 discone antenna. This will be my first experience with a discone. This model can do double duty as a 200W transmit antenna for 2M to 23cm as well. It might become the first antenna mounted on the house, as opposed to the workshop.

Three Years? Really?

I guess it has been.

I have done a few things ham related in the last three years, but I haven’t really been very active on the air. Bad ham!

In February of 2017, I installed the FTM-100DR in my new Kia Sportage. I did not want to drill the roof for the antenna, so I used a magnetic mount, but I found a clever way to route the cable into the car.

There are rubber plugs on the rear gate.

And a cable passthrough from the gate to the body of the car to fish the cable through…

From there, I don’t have any good pictures of it, but I fished the coax from there down to the spare tire well.

By then, the end of the coax was reached and I had to add a connector and more coax to make it reach the front of the car. From there, it’s a pretty normal tuck under the floor mats to the driver side console.

About a year later, I ran the wire to remote mount the control head on the windshield. Sorry about the focus. 🙂

Among the things I enjoyed with the FTM-100DR was playing with APRS. The FTM-100DR can do APRS or something else, but not really both. It can sort of receive APRS messages while being set up to transmit voice, but if it is beaconing APRS data, it’s beaconing data. This was only one factor driving my desire to upgrade, so it was natural to choose the FTM-400XDR. As a side benefit, it was a drop in replacement in the car. Same mounting bracket and power cable for the main unit, same remote cable and suction cup for the control head. And now, APRS is a fully supported feature that can be turned on and off at will with almost no effect on voice operations.

My IC-706MkIIg had been a great rig, but had developed an intermittent transmit problem. Since I generally use it with RemoteRig, I can’t do anything physical to the radio when this issue comes up. I don’t operate often enough to want to deal with a troublesome rig, so I bit the bullet on getting another. I didn’t want a used rig, so I shopped around a bit. I was looking for another rig with with a detachable head for use with RemoteRig; I like that paradigm. I did not have any particular bias for Icom, but I did like the control head for the IC-7100. It seemed well suited to remote operation on a desktop.

Ironically, when I was ready to connect it to the RemoteRig, I found that the radio end unit was non-functional. It had been a while since I’d used it, so I don’t know if it was a storm or long term heat out in the shop that killed it. Long story short, it had no signs of life and the voltage regulator on the board ran super hot, not enough to melt anything, but definitely not right. I contacted Microbit and after a couple of emails and tests back and forth, it was determined to be unrepairable. They sold me a replacement board at a discount price, which was fine with me. It was relatively trivial to get the IC-7100 working over RemoteRig.

Since the IC-7100 has a built in USB soundcard for digital modes, I wanted to look into that. The connectivity with RemoteRig and the USB port is complicated, so I also looked into Icom’s RS-BA1 remote software. To operate *that* remotely, I needed a PC that was local to the radio and it seemed like a tiny fanless PC would suit the purpose.

It worked mostly, but I had a lot of trouble getting it to stay awake long term, no matter what BIOS settings I use. It would be fine for a couple of days then it would go to sleep. I would have go out there and touch it to wake it up. Within a few months, it went belly up as well. I have not revisited it as yet.

Some time back, I bought a new Icom ID-51 handheld. After a couple of years, I decided to sell it because I just had no real use for one out here in the country. Then around January 2018, I decided to get another for access to D-Star. Shrug. Make up my mind!

Speaking of handhelds, inspired largely by Radioddity review and tutorial videos from Dave Casler, I got interested in DMR. Of course, no DMR repeaters in handheld range out here, but Radioddity BaoFeng radios are cheap enough to get two and set them up for simplex operation between the two. It works pretty well, so whenever I do find some DMR repeaters somewhere, I should be able to join in. Plus, there’s always the DMR hotspot angle. Pay no attention to whatever that frequency is there. It was in the radio when I turned it on.

I have never been truly active enough to *justify* QSL cards, at least not in my mind, but I still wanted some. I finally had an epiphany and figured out what would be the best QSL card for me. I found a caricature artist service online and had them produce a portrait suitable for QSL cards.

Antenna Tweakage

I had some time one afternoon to use the RigExpert analyzer to tune the ol’ 6BTV.

For tuning a trap vertical, I can’t imagine it being much easier. Between the analyzer and the DX Engineering tilt base, it only took about an hour.

The procedure is simple. Hook the RigExpert to the antenna, scan the band you want to tune, tilt the antenna down, adjust the length of the space between traps, repeat.

You do the highest frequencies first as that is the bottom of the antenna and will affect the lower frequencies higher up the antenna.

This antenna is pretty broad banded in all the small bands, which isn’t really that hard to do. It does make tuning a matter of moving the small peak to a more desirable spot, in my case, the lower ends of the band where JT65 lives. The charts are kinda dull for 10, 15, 20, 30 and 40 meters.




The nature of lower frequencies combined with an extra wide 80 meter band mean that its pretty hard to make an antenna that covers the entire band. This one is no different.

Since the bandpass is so peaky, I chose to try for the middle of the band.

Scanned the whole range the antenna can do:

Now, after all this, I need to get on the air some more…

The Off Kilter Dipole

I couldn’t help it. A few days ago, I was looking for something else (a common pass time for me) and in the cabinet I opened, I saw the off center fed dipole that I built when I first got back into the hobby. I had it up at the old house. It was an attempt to have a physically smallish antenna that could operate on several bands. I used it for at least on ARRL Field Day. There were problems, most of which are not expected to have been with the design of the antenna 🙂

While I have not found a specific online source of the original instructions, I have found several essentially identical sources, so I will refer the reader to Google on the matter.

Basically, cut a wire to the full length of a half wave dipole for the lowest frequency desired, in this case 40 meters so a bit short of 66 feet, plus a foot or so working and tuning room. Instead of cutting it in the center, cut it 14% off center, 42′ 2-1/4″ and 23′ 8-3/4″. You connect the legs to a 4:1 balun and voilĂ , OCF dipole.

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Here’s where the online information and what I was holding in my hand depart. As I write this, I have not carefully measured the legs of the antenna, but I strongly suspect that I may have cut the short leg not 14% from the center but 14% from the end. That leg of the antenna is significantly shorter than 23 feet and I really think it’s more likely about 9 feet, which would indeed be 14% from the end. Definitely a newbie sort of math error.

Now it gets maybe kinda weirder.

I strung that antenna up Saturday morning. Well, very temporarily “up”, with one end anchored to the workshop door frame and the other to the Mule. The short end is nearest the camera.

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I connected the RigExpert to it with an 18″ jumper and did several SWR scans using it as a standalone unit.

Turns out, the antenna appears to be tuned a little low, but it’s not so far off that it would be unusable, particularly with a tuner and on the low end of 20 meters, maybe even without a tuner.

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Those low SWR dips are just below 40, 20 and 15 meters.

I think it’s funny that, at the time I was testing it on Saturday, I did not yet know about the 14%-from-the-wrong-end error I apparently made when I built the thing, so this didn’t seem to be off base at all.

Scanning the whole range that the RigExpert can do reveals an even more surprising bit. The antenna appears to work at 2:1 or better from about 70MHz up.

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This scan is a little rough because there are only 100 points on a plot covering a full 170MHz. Armed with the information I now have about this antenna, I think I want to set it up and scan it at higher resolution and see if I can learn enough to understand why it works at all. My intuition suggests that the high frequency response might be due to the one really short leg. I want to see exactly where that lowest SWR dip around 150MHz is and what relationship that has to the actual length of the short leg. I think the still reasonable response at lower frequencies may be related the antenna’s overall length and maybe harmonics of 7, 14 and 21 MHz.

I do not yet fully understand the Smith chart, but this doesn’t look like one to learn on, at least not at 170MHz bandwidth.

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Unrelated to that, I also rearranged the equipment rack to accommodate a Mirage 160W VHF amplifier. The power supply I have for it is only 20 amperes, so it may not be up to the task. It is also missing the binding post nut.

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At first glance, I thought this was a 1/4″ x 28 tpi stud, but it turns out to be 6mm x 0.75 pitch. Once I have the power supply connected, I will try out the amp.

Interestingly enough, the thing pulls about 8 amps just sitting there. I am mildly suspicious.

 

Antenna Tuning Precheck

The ol’ 6BTV has been out there for three or four years and has served me well enough. It was about two years ago that I used an MFJ antenna analyzer to see where it’s peaks were after repairing it (from running it down with my truck) and they were all close enough to operating range to leave alone.

However, my interest in more operating means that I’d like to have a better idea where it works best. More than a year ago, I got a Rig Expert AA-170, the HF to 2m range device. Other than firing it up at my desk at work once, I’ve not used it until tonight. Pretty slick box.

10 meters is usable across the band, with a power-peak at the bottom end in the rtty/data sub-band.

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15 and 20 meters are both pretty much smack in the middle of the band.

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30 meters is a pretty narrow band, so it makes sense that it would be pretty flat across the whole thing.

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40 meters is, again, a peak in the lower end of the band. With my interests in JT65 and PSK31, that’s probably as good a place for resonance as any.

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80 meters is where I finally really need to tweak it. The resonance point is a few kHz below the bottom of the band and the antenna bandwidth is fairly narrow, so I need to choose a spot in the band and see how well I can match it.

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If I adjust 10 meters up a little in frequency, the rest of the peaks will move a bit upward as well, as 10 meters is the bottom section of the antenna.

The software that comes with the Rig Expert does a decent job of graphing as well.

This is an SWR scan of 3.0MHz to 30MHz, accounting for 75 feet of RG213 cable. The dips obviously correspond to the tuning of the six bands that the antenna covers, 80, 40, 30, 20, 15 and 10 meters. The software also marks the ham bands in white on the background fill.

6btv-cable

On The Air Again

Well, strictly speaking, I was not really off the air because I was receiving JT65 before I discovered the damage.

We have a friend who visits once a year or sometimes every other year, and while he’s here, it does projects and other work around the house. This time, however, I had inadvertently set a trap.

The coax from my HF vertical antenna comes out of a shallow trench too far away from the workshop. The Husqvarna walk behind line trimmer is a pretty powerful cutter.

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Yesterday, I finally had both time and the materials to repair the damage, protect if from future damage and to add lightning protection along the way.

First, I put a new connector on the coax where it comes out of the dirt and moved my ground rod to the same area. I also added 90 degree elbow of 1-1/2″ PVC conduit to protect the coax at the new spot where it comes out of the ground.

I hit something immovable with about 2 feet of ground rod still sticking out, so I cut it to length.

The ground rod was closer to the radio before, so I had to replace the 10ga solid copper to the inside grounding block. I put a new connector on the coax from the other side of the damage and fed them both through the conduit.

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I put an Alpha Delta stud mount surge protector on the ground rod, using the provided stud to clamp the station ground wire. I sealed the connectors with Temflex tape.

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I dug out enough around the splice enough to put an irrigation valve box around it for maximum protection.

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Finally, I filled and packed the void with soil.

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Although I had a false start assuming the old intermittent transmit problem had returned, the antenna tuned up perfectly on 20m.

Reach For The Stars

Ok, maybe not that high….

Due largely to my difficulties in reaching in to repeaters in the DFW metroplex, I have been looking somewhat into erecting a tower. While my immediate plans are to put a Diamond X300 up on the top of it, having a structure for wire antennae or a tower mounted camera would be nice, too.

The tower itself is expected to be $1500-2000, depending on installed height.

Universal Tower has an aluminum self-supporting tower design that seems to hit all the bullet points. They use a system wherein they design a tower from 30 to 100 feet high, with wind load ratings of 3 to 35 square feet, using modular 10 foot sections of various sizes. They have straight, tapered and top sections in 11, 14, 18, 22, 26 and 30 inch widths. The heavier ratings are shorter towers with wider sections. The straight sections are, duh, a straight section of that width. The tapered section are of that width, but they taper down to the next smaller size at the top. The top sections are finished off like you expect a top section to be, with a conical bit and a place to put a pipe or tubing mast.

I have analyzed the sizes and chosen a starting point of the 9-40 tower, 9 square feet rating, 40 feet high. The entire system consists of a big block of concrete (4 x 4 x 4 feet, which would weigh just short of 5 tons) in the ground with a 22 inch base unit, a 22″ tapered section, an 18″ tapered section, a 14″ tapered section and an 11″ top section. The tower itself is about $1115, not counting the concrete and digging the hole for the anchor.

If 40 feet is not enough, I can add an 18″ straight section between the 22″ tapered and the 18″ tapered for $270, raising the assembly to 50 feet. Continuing, I can add a 14″ straight section for $155 to make the 50 into a 60 and a 22″ straight section for $409 to make the 60 into a 70.

As the height goes up, the wind load rating goes down, 9 square feet, to 7, to 4 and to 3. The 70 foot design is the tallest they allow for the 22″ base. The next size base, 26″, requires a bigger concrete base (4.5 x 4.5 x 5.0 feet) and the 40 foot tower, while rated for 23 square feet wind load, starts just a little cheaper than 22″ 70 foot. Furthermore, the 70 foot tower with the 26″ base only gets 1 more square foot of wind load rating.

I’m guessing a 50 foot tower is likely what I will need to get a better signal into the metroplex. The antenna itself is 10 feet tall and could be mounted on a 10 foot mast at the top of the tower, so the base of the antenna would be at about 58 feet and the top at about 68 feet.

I have a couple of emails out to get quotes on the concrete and the digging. I suspect that digging in our area will hit rock only a little way down, so mechanization is probably going to be a requirement.

There is another variable that I thought wise to check on. The runway at a nearby grass strip airport points pretty much directly at our house. On the fcc.gov website, there is an online tool called TOWAIR wherein you can plug in your coordinates and some details about your proposed tower and it gives a PASS/FAIL on whether your structure needs to be registered with the FAA. It basically calculates the maximum height that a structure can be, based on some rules and specifications. Because this little airport has a runway in excess of 3200 feet and is designated for Public use, a structure within 20,000 feet must fit in a 100:1 glide slope. For every 100 feet farther away, the structure can be 1 foot taller.

When I plug in the coordinates where the tower would be and specify a total height of 70 feet, the tool returns the following failure message: “FAIL SLOPE (100:1) FAA REQ – 0.0 Meters (0.0 Feet) away & exceeds by 11.0 Meters (36.0900 Feet)”

Short version, 70 feet is 36.09 feet too high.

Now I am almost certain this does not mean that the tower would be prohibited, only that it must be registered. Further, it may need to be painted or lighted. I have much research to conduct.

By easter-egging various figures, I was able to determine that a height of 32 feet 9 inches would not need registration. Also, although it would be fairly impractical, moving the tower to the farthest point away from the airport and still on our property is not far enough away to change the permitted height.

While I was snooping around with antenna heights and locations, I punched in the numbers for an 80′ tower on a property not too far away. It is far enough away to clear the requirements with 9.8 feet to spare.