This page is written to educate radio
operators on the effieciency of handie talkies.
Most handie talkies put out no more then 5 watts, some far less.
The antenna on a handie talkie is a compromise antenna. Try this visual test... a dipole antenna for 146 MHz is 3.2 feet long.
Lay a yard stick down on a table. Lay your HT beside it, with the antenna connector at the 18 inch mark.
The dipole antenna (3.2 feet long) has "unity" gain, i.e. zero gain. 5 watts in and a very short coax will probably result in nearly 5 watts effective radiated power.
You can see that the antenna and the body of your HT are far shorter than the yard stick. (Yes, the body of the HT is part of the antenna system.)
There is no way your HT will be as effective with it's rubber duckie than if it had a dipole antenna connected. In fact, your ERP may be far less than the HT's rated 5W output.
Rubber Duckie Antenna Facts: (some of this information taken from http://en.wikipedia.org/wiki/Rubber_Ducky_antenna .
Most handie talkie antennas are some type of spring encased in a rubber coating. In fact, once the rubber is remove, what you have left is a spring.
If the coils of the spring are wide (a large diameter), relative to the length of the array, the resulting antenna will have narrow bandwidth.
Conversely, if the coils of the spring are narrow, relative to the length of the array, the resulting antenna will have its largest possible bandwidth.
If the antenna is resonant, and the spring has a large diameter, the impedance will be well below 50 ohms, tending towards zero ohms with large inductors as the structure starts to resemble a series-tuned circuit with little radiation resistance.
If the antenna is resonant, and the spring has a small diameter, the impedance will increase towards 70 ohms.
Therefore, from these rules, one can surmise that it is possible to design a Rubber Ducky antenna that has about 50 ohms impedance at its feed-point but a compromise of bandwidth may be necessary. Modern Rubber Ducky antennas such as those used on cell phones are tapered in such a way that few performance compromises are necessary.
At 70 CM (UHF) frequencies, a quarter wave antenna (1/2 of a dipole) is 6 inches. Most HT's with 70 CM have a 6 inch antenna on them. BUT... most of those HT's also have 2M (VHF) in them.
Therefore, where does the rubber duckie actually radiate? Even if it is some kind of hybrid antenna, the radiation efficeiency is going to be less than the 6 inch 1/4 wave antenna.
And, if the rubber duckie is actually an antenna made for 2M (NOTE: most 2M antennas will show a perfect match on 70 CM) then the radiation pattern for 70 CM is going to be so skewed that
the effectiveness goes down the tubes.
So, what can a HT be used for?
If you are line-of-sight of a repeater then you can probably use it. If it is line-of-sight and not too far away.
If you are in a hole or dip, your HT is probably better off being used in monitoring or paper weight mode...seriously... unless..
You decide to use an external antenna.
How do you pick the external antenna? Buy the antenna that will give you the most gain, and keep the coax short. A 6 db gain antenna with 5 watts input through a short coax will yield about 19 watts ERP.
And here is something to think about on cable loss:
So, if you buy a 6dB gain antenna, add 50 feet of RG-8 cable, feed with 5 watts, you will have an ERP of about 15.2 watts.
So, the next time you try to hit that distant repeater will sitting in your car under it's "Faraday Cage", and you think your HT is broke (or worse, the repeater is screwed up) remember
your HT is a compromise. It will not do the unreasonable....
Most handie talkies put out no more then 5 watts, some far less.
The antenna on a handie talkie is a compromise antenna. Try this visual test... a dipole antenna for 146 MHz is 3.2 feet long.
Lay a yard stick down on a table. Lay your HT beside it, with the antenna connector at the 18 inch mark.
The dipole antenna (3.2 feet long) has "unity" gain, i.e. zero gain. 5 watts in and a very short coax will probably result in nearly 5 watts effective radiated power.
You can see that the antenna and the body of your HT are far shorter than the yard stick. (Yes, the body of the HT is part of the antenna system.)
There is no way your HT will be as effective with it's rubber duckie than if it had a dipole antenna connected. In fact, your ERP may be far less than the HT's rated 5W output.
Rubber Duckie Antenna Facts: (some of this information taken from http://en.wikipedia.org/wiki/Rubber_Ducky_antenna .
Most handie talkie antennas are some type of spring encased in a rubber coating. In fact, once the rubber is remove, what you have left is a spring.
If the coils of the spring are wide (a large diameter), relative to the length of the array, the resulting antenna will have narrow bandwidth.
Conversely, if the coils of the spring are narrow, relative to the length of the array, the resulting antenna will have its largest possible bandwidth.
If the antenna is resonant, and the spring has a large diameter, the impedance will be well below 50 ohms, tending towards zero ohms with large inductors as the structure starts to resemble a series-tuned circuit with little radiation resistance.
If the antenna is resonant, and the spring has a small diameter, the impedance will increase towards 70 ohms.
Therefore, from these rules, one can surmise that it is possible to design a Rubber Ducky antenna that has about 50 ohms impedance at its feed-point but a compromise of bandwidth may be necessary. Modern Rubber Ducky antennas such as those used on cell phones are tapered in such a way that few performance compromises are necessary.
At 70 CM (UHF) frequencies, a quarter wave antenna (1/2 of a dipole) is 6 inches. Most HT's with 70 CM have a 6 inch antenna on them. BUT... most of those HT's also have 2M (VHF) in them.
Therefore, where does the rubber duckie actually radiate? Even if it is some kind of hybrid antenna, the radiation efficeiency is going to be less than the 6 inch 1/4 wave antenna.
And, if the rubber duckie is actually an antenna made for 2M (NOTE: most 2M antennas will show a perfect match on 70 CM) then the radiation pattern for 70 CM is going to be so skewed that
the effectiveness goes down the tubes.
So, what can a HT be used for?
If you are line-of-sight of a repeater then you can probably use it. If it is line-of-sight and not too far away.
If you are in a hole or dip, your HT is probably better off being used in monitoring or paper weight mode...seriously... unless..
You decide to use an external antenna.
How do you pick the external antenna? Buy the antenna that will give you the most gain, and keep the coax short. A 6 db gain antenna with 5 watts input through a short coax will yield about 19 watts ERP.
And here is something to think about on cable loss:
| Cable |
Length (ft) |
Loss |
Pin (W) |
Pout (W) |
| RG-213 |
100 |
2.61dB |
5 |
2.7 |
| RG-213 |
50 |
1.3dB |
5 |
3.7 |
| RG-8 |
100 |
2.34dB |
5 |
2.9 |
| RG-8 |
50 |
1.17dB |
5 |
3.8 |
| RG-8X |
100 |
4.0dB |
5 |
1.9 |
| RG-8X |
50 |
2.0dB |
5 |
3.2 |
| RG-58 |
100 |
5.0dB |
5 |
1.5 |
| RG-58 |
50 |
2.5dB | 5 |
2.8 |
So, if you buy a 6dB gain antenna, add 50 feet of RG-8 cable, feed with 5 watts, you will have an ERP of about 15.2 watts.
So, the next time you try to hit that distant repeater will sitting in your car under it's "Faraday Cage", and you think your HT is broke (or worse, the repeater is screwed up) remember
your HT is a compromise. It will not do the unreasonable....