Tag Archives: Loop antenna

Video blog episode 012

It’s been a while, but I finally have put together another video.  It starts a new series on small transmitting loops (“magnetic loops”), the workhorse type of antenna at my station.  These antennas are a great option for working on HF when you have very limited space.  Part I of the series gives introductory information and how to do the calculations to design a loop that works for your situation.  Later videos will show how to build and use this type of antenna.


Amateur radio: CQ WW SSB contest prep, late October 2017

Phew! Since I’m at the end of my first 12 months on the air, I decided to put in as full of an effort as I could in the CQ Worldwide SSB contest. Given the limitations of my station, the results-to-effort ratio was rather small, but conditions played a role in that, as well as the huge pileups due to so many people on the air. This post talks about the station upgrades I made before the contest, while the next one will be about the contest itself. Continue reading

Amateur radio: California QSO Party, October 7th-8th, 2017

I’m getting close to finishing my first 12 months on the QSO party circuit, and the California QSO Party is one of the biggest of the year.  Being next-door, I figured I would be able to make a lot of low-band QSOs, but wasn’t sure about 20 meters and above.  The contest ran from 16UT on Saturday through 22UT on Sunday (9am Saturday to 3pm Sunday local time).

Unfortunately, I was not able to do anything radio-related until after 6pm on Saturday, then I had to spend 2 hours getting my new 8-foot diameter loop up and fully operational, including a trip to the hardware store.  I finally got on the air at 0330UT (8:30pm CA and AZ time).  The goal of my largest transmitting loop to date was not only to increase my radiated signal on 40 and 80 meters, but also to be able to transmit on 160 meters.  See my recent post for more information on the loop.

As Murphy’s Law would have it, the first station I heard calling CQ on 40 was having trouble hearing everybody, so after 5 minutes I still wasn’t sure if my antenna was working properly.  But, once I gave up on that station, I was able to make a bunch of easy contacts on the band.  Even with losing 15 minutes struggling to get the loop up a little higher (center of the loop at 10.5 feet), I managed 15 QSOs in the first hour on 40.

I switched to 80 meters, where their were even more good signals out of CA and I picked up 24 QSOs in an hour, a new record for me, including 15 in 25 minutes.  This is all “search and pounce” and especially on 80 meters, the bandwidth on a small transmitting loop is very narrow, so I have to adjust the tuning capacitor before just about every QSO.  This is accomplished using a miniVNA Pro as an antenna analyzer, so I switch the antenna input into that, which goes into my laptop.  The vacuum variable capacitor up on the antenna has a 12-volt motor connected to it, and that runs into the shack to my rig power supply and a simple control box.  The miniVNA Pro sends less than 1 milliwatt to the antenna to analyze it, so it doesn’t transmit a bunch of QRM like some “real” antenna tuners that you often hear on the HF bands.

After that, I switched back and forth between 80 and 40 a couple times.  Activity dramatically dropped off at midnight (07UT), not surprisingly.  I got my 56th QSO (including one duplicate) shortly after that, then nothing more.  I listened on 160 for a station that was periodically calling CQ, but he never heard me respond.

I was back at it on Sunday morning a little before 13UT, and made some more contacts on 40 and 80 meters.  Unfortunately, when I finally checked out 20 meters on my smaller loop, I could barely hear any CA stations, just a cacophony of stations from the eastern US calling into CA.  Unfortunately, indeed I was too close to CA to get any QSOs on 20, so I gave up at around 16UT.

I came back for the last 25 minutes of the contest, still not able to work anyone on 20, but picked up several more QSOs on 40.  I ended the contest with 72 QSOs (plus one duplicate), split evenly between 40 and 80.  I worked 37 out of 58 counties, which I felt was pretty good for just two low bands.  Of course, if I was further away, I might not have made as many 80-meter contacts in getting more 20-meter contacts, so it’s hard to say what that would have done to my county total.

Amateur radio: 160 meters…maybe

I’ve been thinking about ways to get on 160 meters with my very limited space for antennas.  I use small transmitting loops (“magnetic loops”) to cover from 80 meters to 10 meters.  These loops are tuned by the amount of inductance of the loop and a variable capacitor. The frequency scales as the reciprocal of the square root of the inductance/capacitance product.  Thus, the obvious options were to build a larger loop to get more inductance, and/or use more capacitance. Continue reading

Amateur radio: on the air!

I had my 10-foot magnetic loop antenna ready to go for this weekend’s ARRL SSB contest, but realizing that it would only work one band (20 meters) for that contest, at the last minute I decided to build a new loop to finally go on the air as K7HKR. I used this on-line calculator to figure out something optimized for both the 20- and 40-meter bands with the high-voltage variable capacitor I have on hand. This ended up being a 15-foot circumference loop made out of 1/4″ copper coil pipe, which is much easier to bend than the 1/2″ pipe I used for the 10-foot loop. Continue reading