Tag Archives: Arrow antenna

Keeping Arrow Antenna Elements Tight with Loctite

I’m a big fan of the Arrow Antenna for satellite operations for its good performance and portability, but one issue that pops up is the constant need to tighten the elements. I leave my Arrow assembled in the back seat of my Honda Accord, so it loosens up on its own. This is annoying from a clanging noise perspective, but it always messes with the performance of the antenna and throw off the SWR in a huge way.

In a discussion some time ago on Twitter, Mike, W8LID, suggested trying fully aluminum threaded rod as he noticed this eliminated the problem and lessens the weight of the antenna slightly. Apparently, the included threaded studs are zinc plated steel which doesn’t tighten nicely against the aluminum threaded inserts in the arrow shafts. McMaster-Carr sells this threaded rod (8-32), but I found it locally at a metal shop so I saved on shipping costs. You can use a hack saw to cut 2 1/4″ pieces and you’re good to go with some minor filing to clean up the ends.

The aluminum studs developed small bends which become big deflections at the end of the 2m elements!

For the past year or so, I used this setup and it did solve the loosening problem nicely, but I recently noticed the elements were looking bent and misaligned. It also was sometimes difficult to dissemble the antenna as the aluminum hardware was binding a bit too tight to get a good grip to loosen it. I’ve been thinking about switching back to the original studs for these reasons, but I was still concerned about the constantly loosening elements.

A couple weeks ago, Sean, KX9X, held a RoverCon on Zoom, which aimed to provide a forum for satellite operators to meet, talk roving, and have a good time. During this, R.J., WY7AA, who is well known for making awesome drilled out masts, mentioned a solution the to loosening elements problem: purple Loctite. Purple Loctite, or officially Loctite 222, is a low strength threadlocker, weaker than the more common blue Loctite. He suggested putting a dab of it on one side of the threads to lock in the stud into one side of the arrow shaft. This leaves the other side free to easily dissemble, but prevents them from loosening on their own. I ended up using off-brand threadlocker on my own (Permatex 24024). I’ll update this if I have any issues in the future, but I look forward to have a nice and snug Arrow Antenna again without the fragility of aluminum studs!

2020 ARRL June VHF Contest Report

I’ve wanted to give a VHF contest a go for awhile, it never seemed like I could have a workable station for real weak signal VHF being an apartment dweller. With all my travel plans canceled this summer due to COVID-19 and plenty of time to experiment, I figured I might as well clear a few weekends to test a portable VHF setup and then work the ARRL June VHF Contest. I decided I’d largely use equipment I already had which meant entering the contest as Single Operator Portable (SOP) with only 5w.

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February 2020 Satellite Operations Gear

To track things over time, I thought I’d do an overview of my satellite gear as of February 2020. I actually have two different setups for satellite operations: one for the FM/APRS sats and one for the linear transponder sats. Since I do FM sats much more often, I’ve tried to slim that setup down so I can quickly run out to catch a pass.

In both setups, my Kenwood TH-D74A serves as the receiving radio and APRS transceiver. This radio, while not full duplex like its brother the TH-D72A, it is a great option for satellite operations in a two-radio configuration. My favorite feature is the built-in audio recording function. This makes recording audio from satellite passes for later transcription a snap without a mess of additionally cabling and a dangling audio recorder. This radio also contains an APRS function which can be used with the ISS and other APRS satellites with just a couple configuration changes. Finally, this radio has a wideband all-mode receiver which lets it work for SSB on linear satellites. Of course, tuning is a bit tricky without a big knob, but it is doable. For FM sats, I simply hang it from a lanyard around my neck and use a 2.5mm mono to 3.5mm stereo audio adapter cable to connect it to earbuds. I also have all the FM sat frequencies programmed into memory so there is little preparation required for a particular pass.

For FM sats, my transmitting radio is typically the Ailunce HD1. This radio is dual band DMR/FM radio, which makes it versatile outside of sat operations and a way for me to keep my ham radio equipment list to a minimum (blasphemy, right?). There is nothing special about it other than it rated for 10W RF output which can be a nice extra boost when needed (like when using my Shorty Arrow).

Chest rig with Yaesu FT-817ND and Kenwood TH-D74

Chest rig with Yaesu FT-817ND and Kenwood TH-D74

For linear sats, my transmitting radio is the venerable Yaesu FT-817ND. It serves double duty as my QRP HF radio, so it is easy to bring my HF and sat setups together on trips. In order to make it a bit more user friendly for satellites, I’ve added a computer headset with a couple adapters and a handheld button for PTT. I also have made a chest rig made from dual-shoulder camera straps and two MOLLE pouches which hold the 817 and D74 at an angle for easy viewing. This works fine but I’d like something a bit more secure to hold the D74.

LidStick

My Arrow Antenna turned LidStick

The antenna I use is either my standard Arrow Antenna (modified into a LidStick) or my Shorty Arrow (also LidStickified). In 2019, the Mini Circuits BLP-200+  popped into my Twitter feed as Mike, W8LID (also the creator of the LidStick), found that it worked well to prevent desense that is sometimes experienced on certain satellites and radio combinations. This filter is put on the 2m driven element BNC connector, and in my experience, it has completely removed the desense issues I had. You may notice it has a 1/2W rating; Mike got in touch with Mini Circuits and learned that this is really only an issue for out of band signals. Many of us have consistently put 5-10W or more of 2m signals through the filter without any issues.

To travel with my Arrow Antenna, I use a telescopic plastic tube which is commonly used to transport real arrows or posters. It is fairly lightweight, but strong enough that I’ve put it in my checked bag many times and it has kept my antenna protected. It is large enough to fit the full size Arrow Antenna, my Shorty Arrow mast, and even my rubber duck antenna for my HT. For the price, this is an excellent option for transport and storage.

For coax cables, I currently use RG-58/U and LMR-240 UF jumpers with BNC connectors. I recommend staying away from cheap RG-58/U (I’m using it temporarily), but the LMR-240 UF is high quality stuff.

The last part of my setup is my iPhone 11. Nothing special about it, but it runs GoSatWatch as my main satellite tracking app. The app costs $9.99 on the App Store, but it is well worth it for any sat op. I really like that it uses the IMU in your phone so that you can hold your phone up to the sky and physically orient yourself to where the pass will be in augmented reality. It has a simple but nice user interface and can support more than just ham radio satellites.

Theodolite iOS App Camera View

Theodolite Camera View

The other app I use occasionally is Theodolite. Photos from this app are often posted to Twitter, leading many to ask “what app is that?” It is useful to see your exact position and error of the GPS and record that for those gridline and corners that require evidence. It is $5.99 but again, well worth it as it has many other features that you may find useful.

 

Shorty Arrow Satellite Antenna

Shorty Arrow Antenna

After seeing a few people on Twitter with a a shortened Arrow Antenna for satellite operations (colloquially called a “Shorty Arrow”), I decided to try to build my own. Rather than three elements on 2m and seven elements on 70cm as with the regular Arrow Antenna, the shorty arrow has two elements on 2m and four elements on 70cm. This results in a more compact and lightweight antenna at the expense of gain, particularly on 70cm. In my experience, this limits the antennas use down near the horizon¬†especially if you have foliage in the way, and it is definitely a bit more of a challenge to get into some sats. Still, I’ve made plenty of FM contacts using 5w radios and this antenna even on weekend passes. I particularly like using this setup when I travel somewhere via airplane as this is small enough to fit in a carry-on bag.

Since you’ll need the antenna elements anyway, I suggest you buy a full size Arrow if you don’t have one already and just share the elements between them. It also saves you having to bother with measuring and centering the holes you drill; just clamp the full sized Arrow to the shorty to drill like I describe below.

What you’ll need:
-2m driven element
-2m reflector element
-70cm driven element
-70cm reflector element
-70cm 1st director element
-70cm 2nd director element
approximately 2 feet of 3/4″ square aluminum tubing – I found four feet of this at Menards for around $10
-handgrip of some sort. I used a foam grip from a garden trowel I found at the dollar store

Tools:
11/64″ drill bit
-hack saw
-metal file
-hand drill
-a couple clamps

The build process is actually really simple and doesn’t require any measuring:

  1. Remove all the antenna elements and the hand grip from the full size Arrow Antenna.
  2. Take the square aluminum tubing and clamp it flush against the Arrow Antenna. Make sure you don’t place the clamps over any holes.
  3. Use the Arrow Antenna as a drill guide by drilling through its element holes and into the square aluminum tubing with the 11/64″ drill bit. This allows you to easily drill with the same spacing as the original Arrow Antenna without have to measure and center the holes. Do not drill through the holes that are usually hidden behind the hand grip on the Arrow Antenna – these are tapped for a 1/4-20 tripod mount.
  4. Remove the clamps, rotate the tubing and Arrow Antenna so the blank side of the tubing aligns with the other band’s element holes on the Arrow Antenna, re-clamp, and drill the holes for the other band in the same way.
  5. Using the hacksaw, cut the excess length off the aluminum tubing.
  6. Use a metal file to round off the ends of the tubing and remove any burs around the holes.
  7. Slide the hand grip on your new Shorty Arrow Antenna and install the elements.
  8. Go work some sats!