gmcjetpilot
Well Known Member
Better Antenna, get 4 TIMES performance from your Handheld COM Radio!
Here is a great idea for a cheap portable (not for in flight use) antenna for your handheld. It can be made cheaply and roll up compactly. For a few bucks you can make your handheld are real portable base station with 4 times the power! It could save your life in an emergency?
It can be made with some TV twin lead wire, short coax and appropriate connector (usually a BNC connector). This antenna can be hung from a tree or any object. You can also make it free standing by using a PVC pipe, which can be semi-permanently mounted say on your hanger or mobile home when parked for the airshow.
WHY DO THIS. Well if you want max performance 4-TIMES from the original rubber duckie antenna that comes with handheld transceivers, than this is for you.whether ground support logistics at an air-race or just if you want to maximize range this will do it for about $10-$20. Even in an emergency this could be a life saver.
The rubber duckie antenna that comes on all handheld transceivers is a pretty poor excuse for an antenna. Much performance is given up for compactness. There is no magic to many factors of antenna and length is one. You can try and electrically trick the radio to think its connected to a longer antenna, but the radio knows. It's just physics and there's no free lunch. Antenna length and tuning is key to getting the most out of your radio.
Notes: Ham radio guys work with the VHF or 2 meter band just above the Aviation band. These J-polls can be much more involved than this. You can add a ferrite bead on the feed line (50ohm coaxial) where it solders to the antenna, further improving performance. To do a good job a SWR meter should be used; trim the stub 1/4 wave segment (very slowly no more than 1/8" at a time) for min SWR. The stub is the 19.15" segment (15.25" segment for 146Mhz/2-meter version). You must also trim the longer 3/4 wave segment to match as your trim the stub (see article).
This is more technical article but look at the difference from a rubber duckie to a J-pole, over 6 db gain from rubber duckie (see pg 3, table I @ 146 Mhz). That is a huge difference. For each 3 db is equivalent to doubling your transmitting output, so 6 db is 4 times the output! (2 x 2). If it was 9 db, it would be 8 times more (2 x 2 x 2)! This is article is for 146 Mhz, which is above the aviation VHF communication band (118-136 mhz range). If you want to include the NAV (112-117.95 Mhz) band you might tune it lower to 124 Mhz center. I show 122 Mhz with some extra, just so you have room to trim. You can always make it shorter.
No ground is needed because this is a balanced antenna design.
http://www.arrl.org/tis/info/pdf/0302038.pdf
Some more miscellaneous articles
http://www.arrl.org/qst/2007/03/fong.pdf
http://www.qsl.net/wb3gck/jpole.htm
If you're running an airshow, temp ground control or tower with a handheld, this might be a way to go. You could even carry it in your plane. Say you crash and your need to call for help with a handheld. Would you not want over 4 times the transmitting power? This would be an ideal emergency antenna. It's small (rolled up) and does not weight much. Throw a line onto a high tree branch and host it up!
Here is a great idea for a cheap portable (not for in flight use) antenna for your handheld. It can be made cheaply and roll up compactly. For a few bucks you can make your handheld are real portable base station with 4 times the power! It could save your life in an emergency?
It can be made with some TV twin lead wire, short coax and appropriate connector (usually a BNC connector). This antenna can be hung from a tree or any object. You can also make it free standing by using a PVC pipe, which can be semi-permanently mounted say on your hanger or mobile home when parked for the airshow.
WHY DO THIS. Well if you want max performance 4-TIMES from the original rubber duckie antenna that comes with handheld transceivers, than this is for you.whether ground support logistics at an air-race or just if you want to maximize range this will do it for about $10-$20. Even in an emergency this could be a life saver.
The rubber duckie antenna that comes on all handheld transceivers is a pretty poor excuse for an antenna. Much performance is given up for compactness. There is no magic to many factors of antenna and length is one. You can try and electrically trick the radio to think its connected to a longer antenna, but the radio knows. It's just physics and there's no free lunch. Antenna length and tuning is key to getting the most out of your radio.
Notes: Ham radio guys work with the VHF or 2 meter band just above the Aviation band. These J-polls can be much more involved than this. You can add a ferrite bead on the feed line (50ohm coaxial) where it solders to the antenna, further improving performance. To do a good job a SWR meter should be used; trim the stub 1/4 wave segment (very slowly no more than 1/8" at a time) for min SWR. The stub is the 19.15" segment (15.25" segment for 146Mhz/2-meter version). You must also trim the longer 3/4 wave segment to match as your trim the stub (see article).
This is more technical article but look at the difference from a rubber duckie to a J-pole, over 6 db gain from rubber duckie (see pg 3, table I @ 146 Mhz). That is a huge difference. For each 3 db is equivalent to doubling your transmitting output, so 6 db is 4 times the output! (2 x 2). If it was 9 db, it would be 8 times more (2 x 2 x 2)! This is article is for 146 Mhz, which is above the aviation VHF communication band (118-136 mhz range). If you want to include the NAV (112-117.95 Mhz) band you might tune it lower to 124 Mhz center. I show 122 Mhz with some extra, just so you have room to trim. You can always make it shorter.
No ground is needed because this is a balanced antenna design.
http://www.arrl.org/tis/info/pdf/0302038.pdf
Some more miscellaneous articles
http://www.arrl.org/qst/2007/03/fong.pdf
http://www.qsl.net/wb3gck/jpole.htm
If you're running an airshow, temp ground control or tower with a handheld, this might be a way to go. You could even carry it in your plane. Say you crash and your need to call for help with a handheld. Would you not want over 4 times the transmitting power? This would be an ideal emergency antenna. It's small (rolled up) and does not weight much. Throw a line onto a high tree branch and host it up!
Last edited:
