Skip to main content

KH6JRM's Amateur Radio Blog-simple antennas continued

Now that some clear weather has returned to Hawaii Island, I've been able to fix most of my antennas that were damaged by high winds and the 25 inches of rain my qth received during a very wet March.  Most of the repairs went well.  The fiberglass poles were a little scratched by airborne debris and the wire elements were a bit twisted around the masts, but, in general the antennas came through the storms alright.  I was able to lower the masts most of the time before I left for school and that prevented more damage from the high winds.

I erected my two verticals in their original configurations--one a 40-meter inverted vee with the apex at 33 feet and the other a 20-meter vertical dipole stretched out on an old 33-foot MFJ fiberglass pole.  Both antennas were fed by 35-feet of 450-ohm balanced ladder line into a MFJ W9INN 4:1 balun.  A short run of RG-6 coax (15 feet) was connected to my trusty Drake MN-4 ATU.  That in turn was connected to the old Swan 100-MX at the operating desk.  Both antennas tuned up without problems.  I use the 20-meter vertical dipole on 20, 15, and 10 meters, while the 40-meter inverted vee can be used from 40 through 10 meters.  I still have the 40-meter loop under my house.  The loop is my backup antenna in case the other skyhooks meet with an accident.  The loop is also the antenna for my Hallicrafters SX-62A general coverage receiver.

Once I reassembled my "antenna farm", I removed the 135-foot wire that was pressed into emergency service during the bad weather.  Unfortunately, the wire was visible to passerbys and I didn't want too many comments made about it.  The verticals have been painted to blend in with the environment and are usually lowered during the day, unless I'm not working at school.  My neighbors are a pretty good bunch of people, but, with our area being in a weak reception zone for television and FM radio, I really don't want to create any interference with those who depend on over the air reception.  Although most of the neighborhood has cable or direct tv, there are a few who still depend on broadcast signals from the Island of Maui for their television shows.  I keep a pretty low profile and usually operate with power levels below 10 watts.  I have received no complaints about tvi or any other interferrence since I adopted the qrp and stealth antenna ethic.

Despite these limitations, I still get on the air and have a lot of fun, even at 10 watts or less.  Speaking of fun, how about the new 630-meter band approved by WARC-12?  I'm  sure we amateur radio operators can figure out a way to use this band despite the huge antenna requirements for this segment (472 to 479 Khz).  The dipole dimensions would be in the range of 909 feet or so, with vertical elements stretching to almost 455 feet.  The radial field would be quite large as well.  Having working on several MW AM radio stations, I can assure you that putting in an extensive radial field of 120 or so wires, each 1/4 wavelenth long, can be quite an undertaking.  From what I gather in the various antenna forums (i.e. those at eham.net), you could use a large coil with a 160-meter antenna to get on the air.  Assuming a one-percent efficiency rating, you could use a 500 watt amplifier to get the 1 to 5 watts erp required by the WARC-12 document.  Experimental work by amateur radio operators near 500 Khz and efforts by "lowfers" running stations in the 160 Khz to 190 Khz band under part 15 restrictions show promise.  There are also rumors that Elecraft K-3 transceivers will be able to generate power in the 630-meter band.  So, the new frequencies may prove very useful for those of us inclined to experiment in the lower portions of the electromagnetic spectrum.  The FCC is working on regulations for this band and should have some guidance by 2013.

That wraps it up for now.  I'm on call for substitute teaching duty at Laupahoehoe High and Elementary School until Good Friday.  So, it's off to bed for some much-needed "beauty" sleep.  At my advanced age, I need all the help I can get.

Have a good and safe weekend!

Aloha es 73 de KH6JRM--Laupahoehoe, Hawaii.  BK29jx15

Comments

Popular posts from this blog

G5RV Multi Band HF Dipole Antenna. Post #1555.

If you can't see the video, please insert this title URL into your browser search box: https://www.youtube.com/watch?v=aeNHIQ_j4Dk This well-produced and richly illustrated tutorial on the classic G5RV HF Dipole Antenna was presented to the Brandon Amateur Radio Society in Brandon, Florida in 2017 by Bernie Huth (W4BGH).  Bernie does an excellent job of  explaining the pros and cons of this popular HF antenna from the late Louis Varney (G5RV).  Although Varney envisioned his design primarily as a 3/2 wavelength antenna for the 20 meter Amateur Radio band, radio amateurs have used the antenna for multiband use.  The G5RV is an excellent choice for the 20 meter band.  Performance on other HF Amateur Radio bands is good enough to qualify as stand alone HF antenna if you can only erect one HF antenna. For the latest Amateur/Ham Radio news and information, please visit these websites: http://www.HawaiiARRL.info. http://www.arrl.org. http://www.arrl.org/arrl-audio-news (a wee

Amateur Radio Bicycle Mobile Setup. Post #1554.

If you can't see the video, please insert this title URL into your browser search box: https://www.youtube.com/watch?v=2zWb-KnkGdY. Here's a way to use Amatuer/Ham Radio while you work on shedding a few pounds in useful exercise.  Why not equip your bicycle for 2 meter/70 cm mobile operation? In this short, well-made video, "taverned" shows us how he used a mag mount antenna, a simple C clamp, and a basic ground system to convert his mountain bike into a mobile station.  The project is straight forward, simple, and gives you emergency communications while you peddle down the road. For the latest Amateur/Ham Radio news and information, please visit these websites: http://www.HawaiiARRL.info. http://www.arrl.org. http://www.arrl.org/arrl-audio-news (a weekly podcast which is updated each Friday afternoon). https://hamradiohawaii.wordpress.com. https://bigislandarrlnews.com. https://amateurradionewsinformation.com (Amateur Radio News & Information).

An 80-Meter Vertical Helix

Like many amateur radio operators, I live on a small lot surrounded by neighbors, utility lines, and civic-minded citizens concerned about the "attractiveness" of my community.  Whether by design or outright fear, I've adopted the "stealth" approach to ham radio antennas.  It's the old "out of sight, out of mind" idea applied to amateur radio antennas. The amateur radio press is full of articles describing the struggle of amateur radio operators to pursue their hobby under the burdensome regulations of CC & Rs, HOAs, and other civic minded citizens who object to antenna farms.  So far, my modest verticals, loops, and inverted vees have blended well with the vegetation and trees bordering my small backyard.  Vertical antennas have always been a problem because of the limited space for a radial system.  There are times, however, where a shortened vertical for the lower HF bands (such as 80/75 meters) is necessary where horizontal space is lack