Frequently Asked Questions (FAQ)
I've built and sold hundreds of the J-Pole antennas. I've also had lots of questions about installation, operation and performance. Since there is no such thing as a bad question, I'm listing the most frequently asked questions here.
What are the all copper J-Pole antennas
constructed with?
My J-Pole antennas are constructed out of Type M solid copper pipe for the
ultimate in durability and weather resistance. All joints are soldered with
rosin core solder. An SO-239 connector is soldered onto the antenna at the
point of lowest SWR.
How do your two meter J-Poles perform on
the 440 MHz band?
The two meter J-Pole is tuned for maximum efficiency at the 2 meter band where
the SWR is 1.2:1 or less at 146 MHz. It is a pretty good performer on the UHF
band where the SWR is 2:1 - 2.5:1 between 445-450Mhz. This is still within the
range of what modern radios can handle.
Can you build antennas for any other frequencies?
I can build you a custom antenna for any frequency between 40 MHz and 500 Mhz. If you have a special antenna need, please email me and I'll give you a cost estimate.
I need an antenna for my HF, 10 meter, or CB radio. Can you help?
At this time I do not produce any antennas for the HF spectrum. This would include antennas for short wave, hf, 10 meter or CB radios. But I am investigating new products, so check back from time to time to see if I have any new offerings that may meet your needs.
How are your antennas shipped?
I use USPS Priority Mail to ship my antennas. I find that Priority Mail gives you the best price, speed, and deliverability. The 6 meter antennas are shipped UPS 3 day select which works best due to their length. International orders are usually shipped USPS Airmail Parcel Post.
Can the antenna be painted?
As the copper J-Pole is exposed to the elements, it will develop a dark brown
patina. You may paint the antenna with nonmetallic paint to protect it and help
it blend into the surroundings. If you want to keep the antenna looking shiney and new on the tower, you can also paint it with a clear enamel paint.
I recommend the following procedure if you are planning to paint the antenna. First shine the antenna with some fine '00' steel wool. Then clean the antenna with a rag or paper towel soaked with isopropyl alcohol. Alcohol is flammable so do this in a well ventilated area. Also let the rag dry out in the open before throwing it away to prevent spontaneous combustion. Tape the connector up with masking tape and apply one or two coats of spray enamel paint.
Is there any special way in which the
antenna needs to be mounted?
The antenna is naturally at dc-ground, so it does not need any isolation from
the mast. The antenna can be mounted directly to a metal mast with hose clamps
or U-bolts. The J-Pole can be detuned by nearby large metal objects. You should
keep it at least 6 feet away or above metal buildings and the like.
I live in an apartment. Can I still use
your J-Pole antenna.
You will definitely see an improvement with an antenna like a J-Pole when you
compare it to the rubber duck antenna found on today's HTs. Try clamping the
antenna to the balcony or deck railing, to planting it in a flower pot filled
with landscape stones. Try putting it into the attic space if you have access.
As a final result, prop it up in the corner of the room. If you do that, follow
RF safety guidelines and keep the transmitter at a lower power setting.
How does your six meter antenna
perform?
The six meter antenna works really well. I had one ground mounted and was able
to hit a repeater 40 miles away with 5 watts. The return signal was about half
scale on the on the radio and I had excellent signal quality going into the
repeater according the other half of my QSO. Another person mounted his on his
chimney and is able to talk simplex with 100 watts for more than 40 miles and
still have a full scale signal. These examples exhibit average behavior of the
antenna, but your mileage may vary.
What type of coax should I use?
Coax size is dependant on a couple of factors, most notably the length of your
run and the frequency of your antenna. VHF and UHF signals are more prone to
attenuation in the coax, so a low loss cable should be selected. For a run of
100 feet, here are the loss figures in decibels for some of the more popular
coax types:
| Type of coax cable | Loss at 146MHz in db per 100 feet | Loss at 446MHz in db per 100 feet |
| RG-58 | 6.5 | 12.2 |
| RG-8X | 4.7 | 8.6 |
| RG-8 | 2.3 | 4.7 |
| 9913 | 1.6 | 2.9 |
A loss of 3 db will cut your power in half. A six db loss will cut your power into 1/4. I recommend RG-8 if your cable run is over 50 feet and RG-8X if it is less than 50 feet. You shouldn't use RG-58 for VHF/UHF unless it is a very short run (less than 15 feet.). GMRS J-Pole users should only use RG-8 for short runs and Belden 9913 for longer runs. Loss figures for other frequencies and cables can be found at the Cable Experts.
The SWR is really high
on my antenna. What should I check?
Here are a few things you can check if your SWR is high.
1) Check the coax, make sure there are no problems associated with it.
The connectors should be well soldered or crimped without any shorts and there
should be be any apparent kinks in the cable.
2) Check the mounting location, nearby buildings will affect the SWR.
Keep structures at least six feet away from the antenna, or make sure the
antenna is above the structure.
3) Make a balun to keep RF from coming back down the coax. Make a coil
of about 5 loops of coax with a coil diameter of about 6 inches. This coil
should be located about a foot away from the feedpoint of the antenna. Secure
the coil with cable ties or electrical tape.
4) Inspect the antenna itself. Is the solder loose or cracked at the
feedpoint. If it is, let me know.