| WARC |
| WESTCUMB AMATEUR RADIO CLUB |
Westmorland County, NB & Cumberland County, NS
| Westcumb Amateur Radio Club Projects Page |
| Home Brew J-Pole Antenna Project |
Building My Two Metre J-Pole Antenna
(by VE1CHI, Jim)
Around Christmas time I decided to built a new J-Pole antenna as it was noted on air that I was not getting into
the VE1BHS very well. I figured my home brew Slim Jim just wasn't performing that well mounted up in our attic
and contending with electrical wires and fifty zillion roofing nails!
I started an internet search on J-Poles as I already had several plans for them in my 'Antenna File'. Little did I
know that I would be swamped with information. In this case, more was good. Also two club members, Rick,
VE9RWS and Lloyd, VA1MAB gave me copies of their plans.
I planned to have this little project finished by early January but found myself still reading about it into
mid-month. Better to read a lot and see what everyone else experienced before cutting the copper tubing, right?
The WX was great so this was the perfect time to build and erect an antenna.
Peter, VE1CCL was kind enough to lend me his MFJ Antenna Analyzer and eventually I got to the cutting stage
after doing some calculations and buying more parts. I already had the three quarter inch copper pipe left from
another aborted antenna project.
I eventually settled on K4ABT, Buck's plan, and using his generic diagram, did the calculations. Buck's J-Pole plan
with my annotations and calculations is available for download on this page. Your feed point will have to be
adjusted for lowest SWR depending upon where you mount this antenna, the height above ground, surrounding
trees and buildings, type of coax used (I used RG-213) and so on, so my measurement of 6.6 cm (2.598") above
top of the cross piece and to the lower part of the pipe clamp will not necessarily apply in your case. It does
provide a good starting point, however.
I used a small drill bit and drilled a series of holes in one edge of the SO-239 and then put the pipe clamp
through this slot. The SO-239 connector stands up quite nicely on the copper pipe. Sanding the pipe with a fine
grit emery cloth ensures good electrical contact and makes the antenna look great also. The centre conductor wire
(#12 insulated solid copper) was soldered in place on the SO-239 and the other end was fed into a small drilled
hole in the pipe clamp on the shorter quarter wavelength section. I put a bead of solder on this to hold it in place.
Once tightened, it provides a good electrical contact on both elements.
Once the antenna was complete, mounted in place, and tuned, I sealed the connections with gummy coaxial seal and
then used good electrical tape (not Crappy Tire tape) to seal over them again. The entire antenna was then given
two coats of verathane as a third sealant (I know...overkill!). The verathane will also keep the sanded shiny finish
that way for a longer period.
The support for the quarter wave section was fashioned from an old toothbrush handle. Use anything which
provides strength and does not carry an electrical current, of course. I bought ultraviolet-proof cable ties just
for fastening in this support. The entire unit works perfectly!
Testing: Once I moved the feed points up and down the parallel pipe sections, I was able to find the 'sweet spot'
quite easily and then tighten the pipe clamps. I chose a centre frequency of 146.300 MHz. as this is half way
between the lowest and highest of my 'expected to be used' frequencies. Mid-band, of course, is 146.000 MHz.
In my final test on January 19th. this antenna gave me an SWR of 1.02:1 (or lower) over the entire two metre
band. This was using my SWR & Power Meter - a Kenwood SW-200. Using Peter's MFJ Antenna Analyzer, the
needle did not register on the meter over the entire band! It did move ever so slightly, however, but never came
up on the scale to 1:1. Naturally I was delighted with this result! :-)
Performance: The antenna is now complete and appears to work well. It was then that I discovered my radio was
at fault, not my attic Slim Jim antenna! This was confirmed with my Monday night net check-in on the 30th. My
audio simply trailed out to nothing (VE9RWS reported) and when I switched radios (to my HT), and still using the
J-Pole, I was OK. My HT, unfortunately, only puts out 3 watts at high power but when new, it put out 5 watts.
Radios are like us...not quite as snappy in old age! :-)
Just last week I won an eBay auction and I have an Icom IC-2100H coming which has 5w,10w and 55w power
outputs. Once I receive it and program it and use it with the new J-Pole, I will have a better idea of how the
antenna will work. I have no doubt that it will meet or exceed my expectations. My ultimate goal is to have my
home brew J-Pole working with my IC-2100H and THEN I should be able to hit the VE1BHS repeater with a
decent signal. Time will tell.
On the website, I have provided a number of J-Pole plans as well as links to J-Pole websites. Have a look if you
are interested and print off any you think you might want for your 'Antenna file'. Ya never know when the old
antenna building bug will bite!
Post Script: Thanks to Peter, VE1CCL, Rick, VE9RWS, and Lloyd, VA1MAB for your help - greatly appreciated. I
really enjoyed getting back to building an antenna once again - it is a lot of fun and an aspect of the hobby I had
not done for a few years. I may just build another for the fun of it - meanwhile, back to those 'around the house'
projects I conveniently forgot about! :-)
(If anyone wishes to write a story about their antenna or radio related projects, please do so and send it to me (*.doc please) along
with some photos (jpeg) and I will place it here on the website: ve1chi@rac.ca. Thanks.)
(by VE1CHI, Jim)
Around Christmas time I decided to built a new J-Pole antenna as it was noted on air that I was not getting into
the VE1BHS very well. I figured my home brew Slim Jim just wasn't performing that well mounted up in our attic
and contending with electrical wires and fifty zillion roofing nails!
I started an internet search on J-Poles as I already had several plans for them in my 'Antenna File'. Little did I
know that I would be swamped with information. In this case, more was good. Also two club members, Rick,
VE9RWS and Lloyd, VA1MAB gave me copies of their plans.
I planned to have this little project finished by early January but found myself still reading about it into
mid-month. Better to read a lot and see what everyone else experienced before cutting the copper tubing, right?
The WX was great so this was the perfect time to build and erect an antenna.
Peter, VE1CCL was kind enough to lend me his MFJ Antenna Analyzer and eventually I got to the cutting stage
after doing some calculations and buying more parts. I already had the three quarter inch copper pipe left from
another aborted antenna project.
I eventually settled on K4ABT, Buck's plan, and using his generic diagram, did the calculations. Buck's J-Pole plan
with my annotations and calculations is available for download on this page. Your feed point will have to be
adjusted for lowest SWR depending upon where you mount this antenna, the height above ground, surrounding
trees and buildings, type of coax used (I used RG-213) and so on, so my measurement of 6.6 cm (2.598") above
top of the cross piece and to the lower part of the pipe clamp will not necessarily apply in your case. It does
provide a good starting point, however.
I used a small drill bit and drilled a series of holes in one edge of the SO-239 and then put the pipe clamp
through this slot. The SO-239 connector stands up quite nicely on the copper pipe. Sanding the pipe with a fine
grit emery cloth ensures good electrical contact and makes the antenna look great also. The centre conductor wire
(#12 insulated solid copper) was soldered in place on the SO-239 and the other end was fed into a small drilled
hole in the pipe clamp on the shorter quarter wavelength section. I put a bead of solder on this to hold it in place.
Once tightened, it provides a good electrical contact on both elements.
Once the antenna was complete, mounted in place, and tuned, I sealed the connections with gummy coaxial seal and
then used good electrical tape (not Crappy Tire tape) to seal over them again. The entire antenna was then given
two coats of verathane as a third sealant (I know...overkill!). The verathane will also keep the sanded shiny finish
that way for a longer period.
The support for the quarter wave section was fashioned from an old toothbrush handle. Use anything which
provides strength and does not carry an electrical current, of course. I bought ultraviolet-proof cable ties just
for fastening in this support. The entire unit works perfectly!
Testing: Once I moved the feed points up and down the parallel pipe sections, I was able to find the 'sweet spot'
quite easily and then tighten the pipe clamps. I chose a centre frequency of 146.300 MHz. as this is half way
between the lowest and highest of my 'expected to be used' frequencies. Mid-band, of course, is 146.000 MHz.
In my final test on January 19th. this antenna gave me an SWR of 1.02:1 (or lower) over the entire two metre
band. This was using my SWR & Power Meter - a Kenwood SW-200. Using Peter's MFJ Antenna Analyzer, the
needle did not register on the meter over the entire band! It did move ever so slightly, however, but never came
up on the scale to 1:1. Naturally I was delighted with this result! :-)
Performance: The antenna is now complete and appears to work well. It was then that I discovered my radio was
at fault, not my attic Slim Jim antenna! This was confirmed with my Monday night net check-in on the 30th. My
audio simply trailed out to nothing (VE9RWS reported) and when I switched radios (to my HT), and still using the
J-Pole, I was OK. My HT, unfortunately, only puts out 3 watts at high power but when new, it put out 5 watts.
Radios are like us...not quite as snappy in old age! :-)
Just last week I won an eBay auction and I have an Icom IC-2100H coming which has 5w,10w and 55w power
outputs. Once I receive it and program it and use it with the new J-Pole, I will have a better idea of how the
antenna will work. I have no doubt that it will meet or exceed my expectations. My ultimate goal is to have my
home brew J-Pole working with my IC-2100H and THEN I should be able to hit the VE1BHS repeater with a
decent signal. Time will tell.
On the website, I have provided a number of J-Pole plans as well as links to J-Pole websites. Have a look if you
are interested and print off any you think you might want for your 'Antenna file'. Ya never know when the old
antenna building bug will bite!
Post Script: Thanks to Peter, VE1CCL, Rick, VE9RWS, and Lloyd, VA1MAB for your help - greatly appreciated. I
really enjoyed getting back to building an antenna once again - it is a lot of fun and an aspect of the hobby I had
not done for a few years. I may just build another for the fun of it - meanwhile, back to those 'around the house'
projects I conveniently forgot about! :-)
(If anyone wishes to write a story about their antenna or radio related projects, please do so and send it to me (*.doc please) along
with some photos (jpeg) and I will place it here on the website: ve1chi@rac.ca. Thanks.)
| J-Pole Antenna Websites (plans and hints at external websites) Copper Cactus J pole 2 metre / 70 Cm Dual band: http://www.n7qvc.com/copper.html Copper J-Pole Antennas by dxzone.com: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=11160 Design your Own Super J Pole: http://users.marktwain.net/aschmitz/antennas/jpolecalc.html Homegrown Antennas: http://www.w7mjr.com:81/antennas01.shtml J Pole Calculator by dxzone.com: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=9284 Some J-Poles That I Have Known: http://www.cebik.com/vhf/jp1.html Super J-Pole Plans by dxzone.com: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=9288 The J-POLE Home Page - Buxcomm: http://www.packetradio.com/jpoles4ever.htm VE3CFZ's Super J-poles: http://www.wolfgrove.ca/ve3cfz/Super-J/ |
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Download my J-Pole plan here:
VE1CHI J-Pole Construction Plan (Jan. '06).pdf
VE1CHI J-Pole Construction Plan (Jan. '06).pdf