Tag Archives: 40m

The Hardware Store 40m Magnetic Loop Antenna

A while back, I wrote up and submitted some info to QST antenna design competition on my 40m Magnetic Loop antenna. The contest is over so I am now publishing the write up on this site on the Projects page. The direct link to the file is here.

The write up details the design and construction of both the 40m Loop antenna and its High Voltage capacitor made from Copper tubing. Nearly the entire antenna can be made from parts gathered at your local building supply store. Hope some of you find this Useful!


Working 40m and 17m this Weekend

I reconfigured what has become my main antenna, the 40m 1/4 wave vertical. This is still a temporary installation but I am growing increasingly happy with the results I am getting. I frankly can’t remember the last time I used the horizontal end fed. I have had to roll up the radials on occasion to mow the yard and have not yet deployed my permanent radials. Currently I am using the 30 foot travel mast from SOTAbeams to support the vertical wire and have four 27 foot radials deployed. I am using my homebrew 1:1 current balun at the feedpoint and running to the shack with 50 ft of RG-8X.

If I get the chance I’ll start operating around 6:30 am local time on 40m JT-65. I can usually snag several contacts in Japan with the occasional contact into Australia, Indonesia or the Philippines. The action is over by about 7:30am local time as the band closes quickly after sunrise.

Saturday afternoon, I was checking the bands and came across a strong VK station on 17m SSB. We exchanged signals reports in the 54 to 55 range. I moved over to JT-65 and found that there was DX activity including another VK contact. Today Sunday I am finding about the same conditions, great 40m propagation to the far east in the early morning and some light DX into Europe & South America on 17m in the late afternoon.


Vertical Weathers a Thunderstorm

We had some much needed rain at the QTH last night. I had taken down to work on the Homebrew Buddipole early last evening but left the 40m vertical in place. The storm blew through at about 4am and dropped over an inch and a half of rain with gusty winds up to 25 Mph. My wife went outside early this morning and came in to tell me we had debris in the back yard and oh by the way your antenna is bent. Doh!

Went outside expecting the worst. I have heard stories of fiberglass tubes breaking off in high winds. I was relieved to find that the antenna was indeed bent near the top, but only because the vertical wire had blow into and tangled into a tree branch holding it over. I shook it loose and it popped back vertical instantly. Three sections had telescoped back in near the base so after pulling them back out I am back in business. This SOTABeams travel mast has taken some real abuse!

40m QSO’s with 1/4 Wave Vertical

Most of this week was sent collecting WSPR data on the 40m 1/4 wave vertical. The vertical is holding up better to the breezy days after placing some duct tape on the joints of the travel mast. The vertical radiator is a 32 foot length of insulated #14 speaker wire. There are only four 27 foot ground radials deployed at this time. There is a 1:1 current balun at the feed point and about 50 feet of coax to the shack after that. Here is the SWR plot:


SWR is under 1.5:1 across the whole band with a resonant point 7.125 MHz. This antenna has been a solid performer on 40m without a tuner. I am noticing that the band starts opening up to DX about an hour before dusk. Last night I made several SSB contacts with Europe after 10pm local time.

Switching to 40m JT-65 at that time was very interesting as well  as the propagation conditions can be somewhat visualized with pskreporter. I really tested the JTDX software last night and have gotten the hang of the user interface which is subtly different from WSJT-X.  I set the IC-7100 with AGC-off and the bandwidth filter set to 3.6 kHz. Rather than search and pounce, I would look for a quiet spot at the extremes of the band and call CQ DX. This strategy worked well with many European stations answering. Over time, I can see my signals fading on the pskreporter map as eastern Europe’s morning progresses. As dawn approaches in Western Europe, stations start coming online and start to see my signal. At the same time, the opposite terminator starts approaching New Zealand and Australia and my signals starts picking up there as well. I knocked off at about midnight local time and picked up at about 7am and repeated. This time JA stations were answering my CQ and I was running a JT-65 “pile-up” with several JA stations calling at the end of a QSO.

Very pleased with the antenna performance on this band. 20m is acceptable through a tuner but the WSPR data indicates some degradation in performance over a resonant vertical or even the end fed antenna.

Running 40m 1/4 Wave vertical on 20m

Overall I am very impressed with the 40m performance of the 1/4 wave vertical. For grins I am running 20m WSPR by running through the antenna tuner. The tuner found a match and after only 8 hours had enough unique receives to make the WSPR challenge yesterday. The count is now up to 123 and I expect to be on the board again with a very decent showing. I will continue testing on 17m then over to 80m and 160m. Not expecting much on the low bands but am interested in the results. I am not going to run on 15m because it is resonant on that band as a third harmonic to the 40m primary.  I’ll leave 12m and 10m on the DXxtreme as that antenna has proven itself well on those bands (when they are open).

Update on the 40m 1/4 Wave Vertical

Ran WSPR last night on 40m with the 1/4 wave antenna. Here is the Map as of this morning:


Started running some JT-65 this morning and while difficult to run pile ups, I am getting QSO’s with JA by calling CQ. On my third one since starting this morning:


Overall I am very pleased with the performance of this antenna. I’ll be doing some tests on 15m as well although the band has been quiet.

Testing of the 40m Loop Continues

Here is a plot of my 24hr 1W WSPR signal using the 40m Magnetic Loop Antenna:


Next up tested PSK31 and JT65 with 20-30W of power. I made two solid contacts within 380 mi of the QTH which somewhat verifies the NVIS aspect I’d hoped for. I made some additional solid contacts on JT65 including to Guatemala and Cuba. The jury is still out on SSB though. I tried the Daytime Texas Traffic Net on 7.285 this morning and while I closed a contact with Net Control in Amarillo, Texas I was weak and I know there was some transmit problems on my side as the antenna was not tuned with precision. I’ll try again soon with the antenna tuned for 7.285 Mhz. The antenna held up well through the night and through a very windy day here at the QTH in South Texas.It swings around a bit so I may setup a “guy” wire to help position it. It has been largely oriented East-West. I should also note that it is about 2 S units quieter when compared to my main end-fed antenna.  So far so good!

UPDATE 1/11/2017: Made a 100W SSB contact to the Daytime Texas Traffic net. This time I tuned the antenna to a 1.42 SWR at the net frequency of 7.285Mhz. SWR behaved while transmitting and the net control copied my signal without issue. Net control was just east of Dallas in Kaufman, TX. 

40m Magnetic Loop Antenna with Modifications 

Here is the final version of my 40m magnetic loop antenna using my homebrew hi-voltage variable capacitor. As I mentioned yesterday, I fixed an issue with the variable capacitor feed screw. Today I set it up outside handing from a tree as before. The difference is that the capacitor is now at the 3 o’clock position to facilitate tuning without a ladder. This moves the feed point to the 9 o’clock position. No changes were made to the pvc supports as I merely change the position. I read a 1.31 SWR at 7.039 MHz with am fully engaged. I am running 1W WSPR on it now and will report results tomorrow. Here is what it looks like in operation:

Modification to Hi-voltage Capacitor

Made a modification to the High Voltage capacitor today. I added a washer to keep the captive nut on. Seems to work well.


I am ready for my next field test of the 40m loop. This time the cap will be at the 9 o’clock position with the toroid at the 3 o’clock position.

40m Loop Update

I ran 1W WSPR on the 40m Magnetic Loop Antenna for about 18 hours before impending inclement weather forced me to bring it down.Here is what is looks like when taken down:


Very compact. Longest PVC pipe is about 3.5′ long. Here are the WSPR results:


The antenna held up well over night. Only issue is the captive nut came loose. Epoxy does not seem to do the job so I’ll have to come up with a fix. Also thinking about how to bring the tuning adjustment down to a more reasonable height.