A Portable 20/30/40m Vertical Antenna

This post is cross-posted to my more general-purpose nerdery blog, jeff.glass/blog.

Following the Forth of July, I took a few days off of work to recuperate from a grueling work project that we pushed over the finish line on the third. And what better way to relax in the wake of a heatwave than getting out in the beautiful, low-70’s weather and working on a new portable HF antenna.

Pole.jpg
From eBay listing

The heart of the antenna is an inexpensive ‘7.2m’ telescoping fishing pole, which can be had for less than $30 with Prime shipping or for less than $10 if you don’t mind waiting. The pole weighs about 10 ounces, comes with a small fabric sheath, and collapses down to about 24″. I’ve been wanting to try out something like this since I stumbled across VK3YE and his squid-pole setups awhile back – Peter’s also featured these particular poles in another video. Be aware, a pole called “7.2m” may not actually be 7.2 meters from end to end: check the listings carefully:

rod
Note the difference between the “stretch” column and the “specification” column.

The length of the pole is enough for a quarter-wave vertical for 20m with some room to spare on either end. To allow for multi-band operation, I added a QRPGuys Tri-Band Vertical accessory to the bottom of the antenna. The piece is essentially just two loading-coils (in this case, iron-powder toroids) with slide-switches to short them out. The 20m configuration is a true quarter-wave vertical; one of the toroids is switched in series for 30m, and both are placed in series for 40m. Ultimately, not a complicated setup. While it would be easy enough to homebrew, the ergonomics of the switches, the hardware to attach the antenna wire and radials, and the clever PCB setup are enough to make it worth the $15 to just buy the darn thing. It even has little notches on the edges of the PCB for straps/ties/rubberbands to attach it to the vertical.

triband
From QRPGuys.com

Tuning the antenna is straightforward: you cut a piece of wire (a bit long) for a 20m quarter-wave, and lay out four 10′ radials. Then, you bit-by-bit trim down the vertical element to resonate at the desired point in the 20m band. Then you switch in the 30m coil and compress/expand its turns without changing the antenna length to resonate on 30m. Finally, switch in both coils and adjust the second coil to resonate on 40m without changing either the antenna length or the first coil. Voila, a tri-band, base-loaded antenna.

Unfortunately, my antenna analyzer is old school, and doesn’t have a frequency readout. It’s an old MFJ-207 that I scooped up at the SMCC Hamfest in 2016, and while it does have a port to attach a portable frequency counter, I couldn’t find my cheapie one on the day. But I do have a nice Heathkit IM-2420 Frequency Counter with an internal OXCO that I scored an amazing deal on at a hamfest last year (it had an intermittent power switch). So, I attached the MFJ to the antenna, tuned its analog VFO for lowest SWR, walked inside without touching the dail and hooked it up to the frequency counter to see where the center frequency was. Repeat for say the upper and lower 2:1 SWR ranges. Trim the antenna a little, and repeat measurements. Once 20m is tuned, repeat with adjusting the coils for 30m and 40m. A fairly cumbersome process, but for three frequency ranges on one antenna, it was a half-hour project at most.

IMG_4804

In the end, the antenna is less than 2:1 SWR across all of the 20m band, all of the 30m band, and all but the top 50 Khz of the 40m band.

I’ve glossed over the mechanical details of the antenna to this point – the base of the telescoping pole fits snugly-yet-easily into the a piece of 1″ schedule-40 PVC pipe. I bought a 5′ section from the local big-box store and cut off a ~10″ section to hold the antenna. I strapped two ground-stakes that I got at Hamvention this year to the bottom with a couple zip-ties and a couple rubber-bands. Finally,  I threaded a long 3/8″ eye-bolt though a matching hole about 2″ from the bottom of the pipe and secured it with a nut on either side – this acts as both a stop for the pole so it doesn’t fall out the bottom, and provides an easy hand- or foot-hold for pressing the stakes into the ground.

img_4840.jpg
The finished antenna mount. It may be getting a coat of high-vis paint in the near future.

The setup for the radials was something I stumbled across by chance while buying the PVC pipe. Our local big-box hardware store was having a sale on these RECOIL Brand cable winders that are meant for headphones or charging cables or similar. I’ve found that they can almost hold four 10′, 24-guage speaker wire radials. This is solving the problem of wires-getting-tangled-in-a-bag that I’ve had with all my antennas to date. Thank goodness!

img_4842.jpg
A few loose ends are worth it for the assurance that the wires won’t get tangled in transit.

It takes about 6 minutes to setup or tear down the antenna:

  • The stakes are driven into the ground with a firm foot.
  • The telescoping pole is unwrapped and placed in the base
  • The antenna wire is unwound from the QRPGuys winder and tied to the tip of the telescoping pole with a small bit of cotton-wrapped nylon line (what we’d call tie line). The top section the pole is very flimsy, so I add a second tie to the next-largest section.
  • The pole is pushed up to full height, taking the antenna wire with it, which leaves the QRPGuys rig hanging about 2′ off the ground.
  • The QRPGuys rig is tied to the pole with another bit of tieline.
  • The radials are unstrung from their winder, pinched to the ground terminal on the QRPGuys rig, and spread out.
  • Run coax to a nearby table/seat/rock.
  • Set up radio, battery, key, antenna, and logbook.
IMG_4810
The antenna fully set up and freestanding.

Of course, my very first time away from home with the antenna… I forgot the radial wires. D’oh! I was way out in the suburbs, too. I wasn’t about to drive an hour home and an hour back for 4 bits of wire, so I first tried out the antenna with no radials (just the coax as a counterpoise). This worked alright – I picked up K2D in CT in the 13 Colonies event on the second call (this at 5W QRP with the ATS-4), but was having trouble with other contacts.

Since I planned to swing by the local Fry’s Electronics on this adventure, I decided to pause operating for a while and make that run. Mostly I was picking up parts for an amplifier project (more on that to come), but while I was there, I looked for solutions to my radial problem. I found a 10′ section of RJ11 phone cord with 4 wires for $1.69 – perfect! Back out in a new park, I stripped the wires out of their jacket, spread them on the ground, and tied them to the antenna’s ground terminal. Instant radials!

IMG_4814
And such colorful radials too!

With the antenna back to spec, things really picked up – surely, being on 20m at sundown didn’t hurt either. I scooped K2A (NY), K2B (VA), K2H (MA), K2L (SC), and K2M (PA), as well as the 13-cols bonus station WM3PEN in Philly. Many of these I got on the first or second call, though K2L was a real struggle. There was a very patient operator on the other end though.

13cols
The 13 Colonies special operating event runs each year for a week around the 4th of July in the US.

I picked up a couple of other interesting stations along the way: PJ2/KB7Q out of Curacao (though the license gives away that he’s either an ex-pat or visiting), and CQ918FWC from Madeira Island (!) off the coast of Portugal. There were a number of these World Cup special stations on the bands this week as we close in on the finals. At 3800+ miles away, this was my best DX of the day, and a great proof of concept for the new antenna.

ord fnc
At QRP wattage ,this 3800 mile contact was made at 760 miles/watt.

Hear you on the air!

73

Advertisements

ARRL Field Day 2017 – QRP Portable

In contrast to my field day adventures last year, in which I hung out with the folks from the North Shore Radio Club and ran 100W on a K3S, this year I opted for a decided more small-scale approach. Using my ATS-4 receiver, I ran 3.5W CW on 15m, 20m, and 40m for about four hours Saturday afternoon in the lakefront park here in Chicago.

My antenna was a single 40-some-odd-foot wire hung from a tree, fed by my ZM-2 antenna tuner. I think when I built the ZM-2 last year, I goofed something up in the SWR circuitry – the built-in LED should go out at minimum SWR, but mine seems to be brightest at low SWR. To compensate for this, I brought along the MFJ-207 Antenna Analyzer I got at the SMCC Hamfest last year and used that to adjust the antenna tuner.

With the big analog, multi-octave dial on the front of the 207, I found it useful to first tuner the ATS to the desired frequency (say, 14.030) while attached to the antenna and adjust the analyzer until I heard the “WHOOP” of its signal generator in my headphones. With the frequency of the analyzer and receiver close to matching, I’d move the coax back from the tuner to the analyzer and adjust the ATU until the 207 showed lowest SWR. Reconnect the ATS, and away we go!

IMG_0918
The MFJ-207 Antenna Analyzer covers up to an octave with a half-turn of the variable cap. Listening for its signal on a receiver made it much easier to find a specific frequency.

I used a new battery setup for this outing – a 12V, 6000mAh TalentCell lithium-ion pack that I borrowed from work. I love this pack – a little less than a pound, charges from a wall-wart, and has a built-in barrel connector and on-off switch. There are also models with a built-in 5V USB charging port, for topping off cell phones and other devices on the go. While the ATS is designed to run at 12V MAX (not 13.8V), I found that the 12.2V the pack was putting out proved to be fine – it seems the limitation is in the heat dissapation from the BS170 finals, and running relatively low duty-cycle search and pounce that wasn’t an issue. I’ll be ordering one for my own use soon. (Or perhaps the even more compact 3000mAh version – the size of a deck of cards!)

The rest of the pack list included:

  • A HamKey brand iambic paddle
  • A golfball and a kite-string winder for getting the antenna wire into a tree
  • A pair of Koss UR-20 headphones
  • A small battery-powered speaker with 1/8″ aux input
  • Variable DC and Coax jumpers
  • A notebook and pen
  • A folding camp chair.

All of the above fit into a small laptop bag, along with a few other tools and bits I didn’t end up needing.

IMG_2847.JPG
The full field day setup, minus the antenna.

I managed 69 contacts, all QRP CW hunt-and-pounce, during my operating time – no tremendous DX, but I did hit a couple of rocky-mountain states and a plethora of sections up and down the East Coast. Final score was just over 1000 pts – that QRP multiplier really stacks up!

I also couldn’t have asked for better weather on the day – 72 degrees and slightly cloudy with a pleasant breeze. Simply stupendous.

IMG_2845.JPG

Hear you on the air!

73

Catching Up: CQ World Wide CW, 2016

Having started a new job in October that’s keeping me quite busy, I’ve resolved to care less about the timeliness and length of posts, and to prioritize getting them down.

To that end, here’s a brief recollection on the CQWW CW Competition that I participated in back in November. One of the largest international contests of the year, this was certainly a hopping time on the air. I participated using my repaired ATS-4, at around 3W, and there were a good many stations I could hear but not contact. Nevertheless, I ended up with 17 contacts over 11 countries and 7 CQ Zones. My best DX was ED8X in the Canary Islands – a little over 4000 miles away, for better than 1300 miles/Watt. What a day

I wracked up a host of ATNO’s (All Time New Ones, or new countries in the log), including: Curacao, Dominica, Bermuda, the Canary Islands, the Cayman Islands, Bonaire, French Guiana, Turks and Caicos, and Peru.

cqwwcw-map

I’ll be back on the air for CQWW 2017. Hear you on the air!

73

First 30m Contact, and a Stateside Update

This past weekend, late in the evening, as I was fiddling around with the ATS-4 seeing how the bands were doing, I ran across a particularly strong CW signal on 10.116 MHz, near the bottom of the 30m band. It turned out to be the end of a QSO between KA7OGK and W5IP, the latter of whom was coming in 5-by-8 here in Chicago. When they wrapped up their conversation, I through out a quick call to W5IP, and she came back! I could tell that Carroll (whose name I’d gleaned from the earlier conversation) was heading out, as our exchange was much more perfunctory than conversational. But it allowed me to put my first 30m contact (as well as my first Texas station, as it turns out).

And with that, I’ve now made a contact on every band I currently have access to – 80m, 40m, 30m, 20m, and 15m! So far 40m and 20m have proved to be my workhorse bands, but some late-night exploration makes me think I should be paying more attention to 80m later in the evening.


With the new 30m Texas contact, and one with a nice Louisiana ham this morning (WB5WDC, retired petroleum engineer who used to work not far from Chicago in Crystal Lake), my total number of states worked is up to 10: Arizona, California, Colorado, Louisiana, North Carolina, New York, Pennsylvania, Texas, and Virginia:

WAS Map 10-26.png

Until I can put a longer or more-vertical Antenna in the air, I don’t think I’ll be chasing foreign counties for a little while, but Worked-All-States seems like an achievable short-term goal. Of course, of the 10 states I’ve worked, I only have confirmation from California and Pennsylvania, so there’s a way to go yet. But I’m having a great time acquiring my own “All Time New One” states.

Hear you on the air!

73