antenna – Page 9 – WB3GCK QRP Amateur Radio

Antenna Testing at Black Rock Sanctuary

I almost talked myself out of going out today. My grandkids got together and gave me one heck of a cold for Christmas. Thanks a lot, kids. 🙂 Despite being a little under the weather, I packed up and headed out. I’m glad I did.

I drove to nearby Black Rock Sanctuary to test the equipment I plan to use for a National Parks on the Air (NPOTA) activation on New Year’s Day. My antenna today was a 29.5-foot vertical wire with two similar wires on the ground for a counterpoise. I ran one of the wires around the tires of my truck. I ran the other wire into a grassy area directly behind the truck. I figured I was in an area that wouldn’t see any pedestrians. (More on that faulty assumption later.) My rig was my old Yaesu FT-817 and Z-817 tuner.

My vertical antenna. 29.5-foot radiator fed through a 4:1 unun with two 29.5-foot radials. It loaded up great 40M through 10M.

I had last used the FT-817 on 14.060. So, when I powered up the radio, I immediately heard my QRP buddy, Ed WA3WSJ, and gave him a call. Ed was operating pedestrian mobile on Monocacy Hill about 20 miles away from me. He had a great signal. Right after I signed with WA3WSJ, Ed W1GUE gave me a call from New Hampshire.

A view of the "cockpit" of my truck. — A view of the “cockpit” of my truck.

On 15 meters, I called CQ on 21.060 and got a quick response from WA8IWK/8. Allen was portable in Michigan. While I was working Allen, a woman walked her dog directly behind my truck. I noticed her child looking down at the ground. After they left, I went back to check. They apparently had gotten caught up in my counterpoise wire. I re-routed the wire around the truck. Fortunately, I didn’t notice any difference in the antenna tuning.

I moved down to 17 meters and heard Jim W1PID working HK1MW. Jim was hiking in New Hampshire with W3ATB. I moved down a little bit and called CQ. I was hoping that I would catch Jim’s attention. It worked! Conditions were great on 17 meters and Jim said I was very strong into New Hampshire.

On 30 meters, I got a call from a familiar callsign. Wink WA8KOQ from Tennessee is a regular on 30 meters. I’ve worked Wink many times over the years and it was good to hear him again.

I went back to 20 meters to see if I could find Tim W3ATB. No luck today.

Finally, I went back to 17 meters and had a quick QSO with John, YV5IUA in Venezuela.

I’m glad I went out today. The bands were in good shape and my antenna seems to be working great. I should be ready for my NPOTA activation next week.

72, Craig WB3GCK

‘Twas the day before Christmas…

Or was it? You certainly couldn’t tell by the weather. It reached a balmy 71 degrees F today here in southeastern Pennsylvania. It just doesn’t seem right being outside in late December wearing a T-shirt.

Anyway, the shopping was done and the presents were wrapped, so I decided to sneak out to a local park for a little QRP-portable. I drove a couple of miles down the road to Charlestown Township Park and set up in my truck. The forecasters were predicting possible storms, so I operated in the truck today. I used my roll-on support to put my 31-foot Jackite pole up. I used one 30-foot wire as a vertical and another on the ground for a counterpoise. I fed it through a homebrew 4:1 unun. I used my YouKits HB-1B running 4 watts.

Stationary-mobile set up in Charlestown Township Park — Stationary-mobile set up

I started out on 20 meters but had no luck there. Moving down to 30 meters, I got a call from Walt WB8E near Detroit. Walt had a nice signal in Pennsylvania, despite some fading on the band. Next, I went to 40 meters and had a nice, long chat with Lou WA3MIX in Williamsport, PA. Lou grew up in my area and has some relatives in nearby towns. Finally, I went back to 20 meters and called CQ on 14.060MHz a few times. As I reached over to shut off the radio, I heard Dave KB8XG calling me from Michigan. This was Dave’s second CW contact. After wrapping up with Dave, I packed up and headed home.

Whatever your weather is like, I hope you have a very Merry Christmas!

72, Craig WB3GCK

AlexLoop Mounting

In my 40+ years in Amateur Radio, the AlexLoop Walkham was the first commercially-made HF antenna I ever bought. I wanted something for those spur-of-the-moment QRP outings when I want to get on the air quickly and not have to deal with putting wires into trees. The AlexLoop fit the bill nicely. There’s probably nothing novel or new here but here’s how I mount the AlexLoop for operation.

Tripod Mounting. While I was waiting for the AlexLoop to arrive from Brazil, I ordered a Vivitar VPT-1250 tripod from a vendor on eBay for less than $20. The VPT-1250 is super lightweight and stores nicely in the AlexLoop’s carrying bag. It’s a decent tripod for casual use but for something like a SOTA activation under windy conditions, you’d be better off with something more robust.

vivitar_tripod_2 — Vivitar VPT-1250 Tripod with PVC pipe installed.

To use the VPT-1250, I removed the pan/tilt head. I cut a 4-inch piece of 1/2-inch PVC pipe, which I slide over the center post of the tripod. I added a bit of electrical tape to both the tripod post and the PVC pipe to give a slight friction fit. The base of the AlexLoop slides onto the PVC pipe.

Picnic Table Mounting. This is an idea I got from AK4LP’s QRZ page. For mounting to a table, I take the same piece of PVC pipe and insert it into a 1/2-inch PVC elbow fitting. I sanded the end of the PVC pipe so it was easier to remove from the elbow fitting.

I just use a 2-inch C-clamp to secure the pipe and elbow fitting to the side of the table. Again, the base of the AlexLoop just slides over the pipe. I store the PVC parts and the C-clamp in the tripod’s nylon carrying bag. When a picnic table is available, this mount goes to together faster than setting up the tripod.

table_mount_2 — AlexLoop base mounted to table

If anyone knows the ham who came up with the picnic table mounting idea, let me know in the comments and I’ll make sure he gets credit for it.

UPDATE (11/16/2015): I remember now where I got the idea for the picnic table mount and have updated the post accordingly. Many thanks to Bob AK4LP for coming up with this simple and novel idea! Be sure to check out his page on QRZ.com for pictures of his picnic table portable setup. I had the pleasure of working him at that Smith Mountain Lake location back in 2013 while I was camping in Maryland.

73, Craig WB3GCK

Line Isolator

One of my favorite portable antennas is a 30-ft wire fed through a 9:1 unun. This type of antenna generally the uses coax feeder as a counterpoise, since the 9:1 unun configuration provides no line isolation. Most of the time, this has worked well for me with no issues with stray RF getting back into the equipment.

On a couple of occasions, my Elecraft T1 auto tuner began to act up, refusing to load up on one or more bands. (Running through the T1’s diagnostic mode always seems to restore operation to normal.) I’ve also had one of my keyers behave erratically once or twice. Since this has only happened when using the 9:1 unun, my suspicion is that common-mode RF currents on the coax shield are the culprit.

My proposed solution for this is to use a line isolator between the tuner and the coax feeder. (Note: Using a line isolator at the antenna end of the coax would defeat the purpose in using the coax as a counterpoise.) A quick survey of my junk box stash of parts showed I had everything I need to build a line isolator from scratch.

Parts List

RG-174/U coax (approximately 24 inches)
FT-140-43 ferrite core
(2) BNC-F chassis mount connectors
Hammond Manufacturing 1591MSBK Enclosure (2.2 x 3.3 x 0.8 inches)

Construction

This is a very simple project. You can build one in well under an hour.

The RG-174 coax is wound on the FT-140-43 core for a total of 10 turns. Take note of how the 5th turn goes across the core. This makes installation in the case a little easier. I used a couple of small nylon tie-wraps to hold the windings in place.
Drill the holes for each of the BNC connectors and wired up the choke, as shown. I used a 5/64-inch drill bit and had to use a reamer to get the holes to the right size for the BNC connectors I used.
Solder the coax to the BNC connectors.
To mechanically secure the core, I used a piece of two-sided foam mounting tape to mount the choke to the bottom of the case. As an additional precaution, I put a piece of packing foam on top of the choke before attaching the lid. This foam provides a slight downward pressure on the choke to prevent it from shaking loose in the case during handling.

isolator_core_installed — Core installed in case

Testing

I don’t have access to the equipment necessary to do any type of exhaustive testing of the line isolator. In lieu of that, I hooked it up to a 50-ohm dummy load and checked the SWR. It was basically flat from 160M through 6M. While that tells me nothing about how effective it is in reducing common-mode currents, I at least know I didn’t make any serious screw-ups in building it.

2015-11-08 13.45.50 — Completed line isolator

In Operation

Well, this part will have to wait until I have a chance to get out for some portable operating. I want to make sure that the line isolator doesn’t affect the T1’s ability to tune my antenna. Since the initial problems were very intermittent, only time will tell if I solved those problems or not. I’ll be sure to update this post with any new insights I gain.

Update 5/16/2017:

Since this article seems to get a lot of traffic, I figured it was time for a long-overdue update. Not long after this post was published, I tested this 1:1 unun in line with the coax to my 30-foot wire and 9:1 unun. As I suspected it might, it affected the tuning of the antenna. One or two bands wouldn’t load up properly. This made sense to me, since this antenna configuration relies on the shield of the coax for the counterpoise. So, there’s some RF on the coax shield by design. This device obviously is blocking some RF, as it should. I haven’t pursued it further and I still have done any measurements to determine its effectiveness. With a change of connectors on the output side, it could definitely be useful as a 1:1 balun, I suppose.

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Jackite Pole Hacks

I’m a big fan of the Jackite fiberglass poles for portable antenna supports. I have two of them have have seen a lot of use over the years. Here are a couple of quick and simple hacks that improve (in my opinion) on an already great product.

Keeping the Cap From Falling Off

While the overall quality of Jackite’s products is excellent, there is one thing that I find annoying — the caps have a tendency to fall off when transporting the pole. To overcome this, I attached a velcro strap to the cap (Figure 1). The Velcro is something I had on hand in my junkbox. It’s about 8 inches long by 1 inch wide. I used a #4 machine screw with some flat washers, a lock washer and a nut (Figure 2). I used an awl and a small phillips screw driver to make the hole in the cap. I then attached two Velcro strips (the fuzzy part) on either side of the pole (Figure 3). When transporting the pole, just secure the Velcro straps (Figure 4) and you’re good-to-go.

Easy Extension

This quick mod might seem kinda pointless to some users. In fact, I hesitated about writing it up. Anyway, you be the judge:

In cases when I need to bungee or strap the pole to a fixed support, I would first need to extend the top-most section first. This is because the top section sits down inside the other sections when collapsed. What I did was attach a key ring (aka split ring) to the eyelet on the top section (Figure 5). The ring I used is approximately 7/8-inch in diameter. So, I can strap the collapsed pole to a support, remove the cap, reach in and use the ring to pull the top section out (Figure 6).

Again, you might not see the value in this one, but I find it helpful.

73, Craig WB3GCK

Guy Ring for a 31-ft Jackite Pole

Here’s a neat idea I “borrowed” from my QRP buddy, Ed Breneiser WA3WSJ. When I need my Jackite pole to be self-supporting and I don’t have to carry stuff very far, I usually opt for my Jackite ground mount stake. It’s quick and effective but too heavy to carry on a hike. Not to mention the need for a hammer (or large rock) to drive it into the ground. So, in situations where the ground mount is impractical, I use a set of guy lines to hold the pole up. Here’s a simple way that Ed came up with for securing the guy lines to a 31-foot Jackite pole.

It’s pretty simple to build one of these…

Pick up a 2-inch, Schedule 40, PVC end-cap at your local hardware store. You’ll also need some nylon line. I used some 1/8-inch braided nylon rope from my local Walmart store.

Drill a 1.75-inch hole in the top, using a hole saw attached to your drill. When slid over the Jackite pole, the guy ring should rest on top of the bottom (largest) section of the pole.
Drill three evenly spaced holes around the outside of the end cap. Use a drill size just large enough to accept the size of line you are using.
Drill a second hole about 0.5 inch to the left of each of the three original holes. So, you should wind up with 3 pairs of holes around the end cap.
Cut three pieces of line. I made each of mine about 9 feet long.
Thread the line through the end cap holes, as shown in the pictures, and secure the end with a knot.
For the other end of each line, I tied a taut line hitch. This allows you to adjust the tension on each guy line.

My completed guying kit consists of the guy ring with the lines attached and four small plastic tent stakes. Everything fits nicely in a zip-lock bag. (I sometimes throw a lightweight, plastic mallet/stake puller in my backpack to drive in the stakes.) To use it, I drive in one of the tent stakes where the pole will go and three equally spaced tent stakes around it. Put these three tent stakes about 5 or 6 feet away from the center stake. Take the bottom cap off of your pole and place the pole over the center tent stake. The center tent stake should prevent the bottom of the pole from kicking out. Attach the guy lines to the three outer tent stakes and adjust the taut line hitches for the proper tension. That’s all there is to it.

I also built one of these for my 28-foot Jackite pole. For this pole, I used a 1.5-inch end cap. I used a 1.5-inch hole saw to make the large hole. The hole was a bit too small, so I did some filing on it to get the proper fit. The final hole size is approximately 1.6 inches. Again, the guy ring should rest on top of the bottom section. Everything else is the same as for the 31-foot pole.

Thanks again to WA3WSJ for sharing this idea with me.

73, Craig WB3GCK