Tag Archives: HF

I Can’t Believe My Antenna’s Up!

I suppose the title could also be: (or how I learned to stop procrastinating and finally put up my HF antenna).

Well, I did it. I finally got my HF antenna up after months of admiring it through the plastic wrap and having the world’s most expensive paperweight (IC-7300) sitting in my metashack (how could I really ascribe any reality to it when it was still merely a concept). What I would like to accomplish in this article is not only a description of the construction etc. but also of some mental gymnastics, I had to do in order to get to the finish line.

Way back in February, I was able to get my General license. I was pretty stoked (to use the common tongue) and looking forward to getting it up and going. This required, essentially, two things: a radio and an antenna. Easy-peasy, right? The first really was easy. I wanted a 7300. Who didn’t? The proverbial ICOM bandwagon drove by my house daily. Several times a day while banging on a few drums. So, I did my homework as best as I could, talked to a few folks, and with not much arm twisting, bought a rig. Now I needed the antenna. And some drums…

For this portion of the ordeal, I ended up doing my homework a little more. I spoke to Fred and Anita at length about their choices: read their blog, saw their own setup in person, read posts in the Elmering session of Nashua ARC’s website, read comments on eHam.net about various antenna types. Some factors to consider are — in no particular order:

    1. Budget
    2. How much help you will have to put this up
    3. Aesthetics
    4. Available real estate
    5. How many bands do you want to work

At my QTH in MA, I have 0.5 acres in the front and back.

My QTH in Tewksbury, MA
My QTH in Tewksbury, MA

Having done my homework, I decided to go with the Buckmaster 7-band off-center fed dipole rated for 3 kW.

First Antenna - 3 kW antenna at the top
3 kW antenna at the top

I think the price point was a bit north of 300 bucks. Having made up my mind, I didn’t do anything about it. Upon reflection, I think I really didn’t act because work consumed me until mid-May. I literally had no free weekends for months, so there was no rush. In the interim, Fred and Anita had opened up their station for use, and I took joy in hearing about others’ QSOs for a while.

In order to still feel like a HAM, however, I decided to take my Extra exam in May. Once I that got out of the way I bought the Buckmaster in June on one fateful Thursday afternoon, and again, there it sat in the meta shack until September. Excuse #2: Honestly, with a project this big (at least for me) I think I was a bit gun-shy to get it up. I felt unqualified to do it; maybe even afraid to fail amidst all these competent people in the club.

Up until now, this may have read as Dear Diary, so let’s get to some actual station construction! Labor Day weekend was the ticket.

Good grief was this tough! Probably 85-90% of the total time was spent trying to figure this out. Mainly because, looking at the graphic, I had to get this about 35 ft. in the air. I got frustrated pretty quickly…

Buckmaster OCF dipole installation picture. Right from their website
Buckmaster OCF dipole installation picture. Right from their website

Now maybe that doesn’t seem like it’s that high, but I assure you, it becomes pretty darn high when you keep failing. So thinking about the problem and researching on the internet led me to some methods to try to get a rope up in the tree:

  1. Use a potato gun
  2. Call folks from the club to come lend a hand
  3. Rent a scissor lift from Home Depot
  4. Use a bow and arrow
  5. Use rope tied to a rock or stick and try to launch over the branch I want.

Here was what the jury decided on each of these options:

  1. Built one! Fires really well, but had issues initially with sparking it in the combustion chamber. Turns out the reason was due to insufficient amounts of butane getting into the chamber. In any case, I abandoned this as a choice. But who’s to say I can’t be mischievous at a later date.
  2. I felt bad bothering folks despite one ethos of amateur radio is to Elmer each other, so I didn’t ask for help. Bad news bears to those of you in the same predicament.
  3. Too expensive for the little time I needed it. I think Home Depot (spelling error intentional) wanted something in the neighborhood of 200 bucks or more.
  4. Don’t have one and nearest friend with one lived in Carlisle. Would have to work around his schedule and at this point, I was thru being patient.
  5. Rock idea worked reasonably well, but honestly, the best option was to get a stick and tie nylon fishing line around it. I have a pretty good arm it turns out, so I tied fishing line around the stick and started throwing.

In full disclosure, the elimination of these options takes us from Friday to Monday. Wisps of steam could be seen emanating from my ears.

The stick was attaining the requisite height and hitting where I needed it to. The huge snag (no pun intended), though, was the fishing line was getting caught in the branches on the way down. Yet another problem. Cue engineer father-in-law. He’s the guy labeled “this guy” in the picture.

Helper Dude
Helper Dude

He recommended winding a large amount of fishing line around the stick (but not all of it so that there would still be some left over on my side of the branch) so that when it came down the other side of the branch, it would unravel and not be as likely to get caught. This worked like a charm!

With the fishing line on either side of the branch, we tied the actual nylon, water / UV resistant rope (which I picked up at Home Depot) somewhere 25% up my side of the fishing line and then got on the far side of the branch and began hoisting it up. This also worked out very well.

First Antenna - Same father-in-law and hanging ropes which will support the Buckmaster
Same father-in-law and hanging ropes which will support the Buckmaster

Finally, with the rope I actually want to use over the tree, I tied the Buckmaster to one end of the rope on my side of the branch and then raised it up. I lowered and raised it a few times to make sure it wouldn’t get caught in the tree at any place. I tied off the free end through an eye screw that I screwed into the tree.

The coax I used was LMR-400. Again, doing my homework, I decided to splurge and buy 200 ft of coax but without the PL-259 connectors. I did this because I wanted to be able to cut the coax where I wished and would subsequently learn how to attach the connectors myself. This too turned out to be a relatively easy job. I picked up some connectors at the Boxboro Hamvention and borrows Dave’s (N1RF) crimper set (with dies) to attach the connectors. Taking my time, I was able to do both ends of the 200 ft coax in about 30 minutes tops. I also purchased some Super 88 electrical tape from Home Depot as well as used Scotch’s 2228 Moisture Sealing Electrical Tape (some other folks use CoaxWrap) for weatherproofing. I applied this following Fred’s suggestion on his blog.

First Antenna - Layers of super 88 and weatherproofing electrical tape fastened to antenna connection point
Layers of super 88 and weatherproofing electrical tape fastened to antenna connection point

With the feed-point setup, I then purchased two more nylon, water/UV resistant ropes to connect to the Buckmaster’s insulators. I found that the 3/16” diameter by 100 ft. rope worked well (3/16″ fit nicely through the insulators’ 1/2″ holes), again purchased at Home Depot. Shirley, the cashier, shot me a smile after ringing me up for the umpteenth time. To temporarily tie these off, I terminated the rope through some more eye screws I screwed into trees in my yard. But for the final installation, I will again follow Fred’s advice from his blog post.

Then, I ran inside, ran the coax through the window thereby performing the transformation of the meta shack into a proto shack! (Proto because it’s in the process of getting changed and upgraded) Ta da! Prestidigitation! That night I worked Brazil and the Czech Republic on 20 and 40 m respectively, and Australia around 0615 the next morning on 20m.

Protoshack, Coax not shown.
Protoshack. Coax not shown.

My follow up projects:

  1. I never mentioned grounding. I do have an 8 ft copper ground rod that I will install. I bought lightening arresters from DX Engineering: I have the kind that allows the passage of DC voltage which is needed for utilizing an antenna switch down the road. Since I plan on buying an antenna switch later, this seemed like a good option. This entire installation will take some time, so I need to find a free weekend. For now, I am only operating when the skies look perfect!
  2. Install my 15 m dipole that I bought from the HRO and covers the band not covered but the Buckmaster. This will likely happen in the Spring. For reals.
  3. Track down RF interference sources in my home and install the necessary chokes and beads. I’m kind of looking forward to this step.
  4. Find a final resting height for the radiating wires of my Buckmaster. I have a cousin with tree climbing equipment. Once he comes over to trim some branches etc., I am going to try and make a 180-degree angle with the wires as best as I can. Additionally, my wife wants me to switch out the white, nylon, water/UV resistant rope with dark colored rope since it’s a bit too visible.

Once I got going, I really had a blast. If I can be of any help to anyone about this, please feel free to send me a reply or contact me on the club website. Thanks a lot for following me through the whirlwinds that are my thoughts, and see you on the air!

Best and 73,

Brian (AB1ZO)

NPOTA Fun – Activating a New Park

Ever since we built our Mobile HF Station, we’ve talked about taking it to Acadia National Park in Maine and operating from the top of Cadillac Mountain.  The 2016 ARRL NPOTA event gave us the motivation to plan the trip for the week before Labor Day.    The week before our trip, we saw an article in the ARRL Letter encouraging operation from the newly declared National Monument, Katahdin Woods and Waters in Maine, which had just be designated as NPOTA MN84.  Visiting the NPS website, we learned that the park is only a 2 1/2 hour drive from Bar Harbor, where we are staying.  We decided to accept the challenge to be the first to activate the new park.

F150 Mobile Station at the entrance to Katadhin Woods and Wildlife National Monument NPOTA
Our F150 Mobile Station at the entrance to Katahdin Woods and Waters National Monument

Tuesday, August 30 was our first full day of vacation, we left our hotel room and parked by the Acadia visitor center and called “CQ National Parks”.   We ended up with 76 contacts in the log from NP01.

After that we got on the road and headed toward Katahdin Woods and Waters, activating counties along the way including the county line between Penobscot and Aroostook Counties.

NPS Map of the NPOTA
NPS Map of the Park

As a newly designated National Monument, Katahdin Woods and Waters does not yet have a visitors center or any signs showing you when you enter and exit the park.  We just had the map (above) to determine where the park boundaries were.    All of the roads in black on the map are gravel roads that are also used for logging trucks.

Entrance to Katahdin Woods and Waters National Monument NPOTA
Entrance to Katahdin Woods and Waters National Monument

We entered the park from Swift Brook Road off Rt 11 in the lower right corner of the map.  We drove through the lower section by the entrance and then headed north along the Eastern Branch of the Penobscot River and operated near the Loos camping area.   The sign above confirmed that we were within the park boundaries.

Scenic View of Katahdin Woods and Waters NM NPOTA
Scenic View of Katahdin Woods and Waters NM

The scenery along the river was beautiful with views of the mountains in the distance.

Operating at NPOTA MN84
Operating at MN84

We started operating on 20m and the pileups were huge!  Everyone was excited to get this new NPOTA into the log.  Fred, AB1OC/M ended up going split on 20m due to the size of the pile-ups.  After a while, he moved to 40m to give the close in folks a chance at MN84.  We went back and further between 20m and 40m until the pile-ups thinned out.   We also made 18 QSOs with the club callsign N1FD to also give the club credit for the activation.  We really enjoyed activating the park and the people we talked to were great!  We made a total of 350 QSOs from MN84.

Katahdin Woods and Waters NPOTA - National Park Yes!
Friendly Sign at Katahdin Woods & Waters

We also plan to activate Acadia National Park NP01 again from Cadillac Mountain this week. We will also activate Saint Croix Island, HS01 and Roosevelt Campobello International Park, AA21 in Canada (as AB1OC/VE9 and AB1QB/VE9).

Activating MN84 for the first time was truly a memorable experience.  We enjoyed it so much we will be back on Saturday to give more NPOTA chasers a chance at MN84!  Hope to talk to you on the air!

Anita, AB1QB

Broadband Matching for Antennas

This article discusses some work on designing a matching network to make antennas match well (low VSWR) across the entire ham band.  This will be a described in more detail at the September Tech Night.

Antennas have an impedance (or match) that varies with frequency.   Transmitters want to see a matched antenna with an impedance of 50 ohms.    The antenna has the best match at one frequency and the match gets worse as the operating frequency changes.

Some bands and antennas are more challenging to match than others.  Shortened or loaded antennas have a narrow range of match frequencies.  The 75/80 meter band has a wide bandwidth in term of percentage.

Here’s a plot of the SWR for my 40 Meter Dipole.  It’s a good match at 7.000 MHz and degrades to about 2:1 at 7.100 MHz.  Obviously, this is not optimized.

Broadband Matching - SWR for 40M Dipole
SWR for 40M Dipole

Modern radios have built in automatically adaptive matching networks make the radios work over a wider bandwidth, but networks are lossy and reduce transmitted power.

A manual antenna tuner has a lot lower loss than the built in tuner, but it requires manual adjustment.  In fact, the extra tuned circuits generally act to make the antenna have even less bandwidth.

The QUCS RF circuit simulation program has the ability to model SWR, bandwidth, matching networks based on data about antenna performance.  The antenna data can come from either an antenna modeling program such as 4NEC2 or EZNEC.  Or the data can come from a measurement made by a good antenna analyzer.

QUCS also has a built in optimizer.  It has the ability to try hundreds of circuit values and home in on an optimal design.

The optimizer setup needs a definition of “optimal”.  For the case of a broadband antenna, “The worst case SWR anywhere in the ham band shall be as low as possible”.  In the terms that QUCS understands, “minimize the maximum SWR over the frequency range 7.00 to 7.35 MHz.

Here is the result from running the optimizer on the data for my mistuned 40M dipole.  QUCS has designed a broadband matching network that can achieve less than 1.5:1 SWR over the whole band.

Broadband Matching

QUCS achieved this by varying the components of a filter network.  I drew a general filter network and let QUCS tune the component values.  This network is designed with coaxial stubs.

Broadband Matching

The model of the antenna is stored as a file in the X1 file component. Line7 is a 30-meter coax feedline.  The actual matching network consists of Line 1, 2, 3, 4.  Each line is 50 Ohm coax.  Line 1 and 3 are configured as open stubs.  The line lengths predicted by the model are…

  • Line 1: 7.75 meters
  • LIne 2: 4.47 meters
  • Line 3: 8.49 meters
  • Line 5: 8.03 meters

Here’s another example.  160-meter antennas are often implemented as shortened loaded verticals.  The loading makes the match very narrow-band.   The red curve in the plot below shows a top loaded 160 meter vertical.  It only covers a fraction of the band.Broadband Matching

The blue curve shows the result of an optimization run that selected the values for a 7 component matching network.  It achieves about 1.7:1 across the whole band.  This network uses capacitors and inductors because coax stubs would be very long on 160 meters.

Broadband Matching

The component values for this network…

  • C1: 3450 pF
  • L1: 3.954 uH
  • C2: 3978 pF
  • L2: 6.951 uH
  • C3: 6156 pF
  • L3: 2.831 uH
  • C4: 4778 pF

I have not built any of these networks to see how they work in practice.  The 160-meter network has some extreme values and it is probably very touchy to get right.  Building that network to handle Tx power will require vacuum variable capacitors in parallel with high quality stable fixed value capacitors.   But, the 160 network doesn’t really need 7 components.  Put in one less stage of L-C and the ripple across the passband goes up a bit.

Conclusions

QUCS is a great RF circuit simulator.  This shows that it can work with data from an antenna model or analyzer and can optimize matching networks to create a broadband antenna.

Jeff, WA1HCO

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