Noob Amateur Radio Antenna Question

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W6SAE

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220 MHz Antenna Question

I recently placed into service a KB9VBR 2-meter J-Pole antenna and am quite pleased with its performance. In addition to 2 meters, it also works well on 70 centimeters. My question is this: would it also be likely to perform well on the 1.25 meter band (220 MHz), since it is between the 2 meter and 70 cm bands?
 
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AK9R

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If you multiply 146 MHz, which is in the middle of the 2m band, by 3, you get 438 MHz, which is just below the 440 MHz repeater portion of the 70cm band. In other words, the 440 MHz band is roughly the 3rd harmonic of the 2m band. Consequently, it's not unusual for a 2m antenna to work on 440 MHz.

Whether that same antenna will work on the 222 MHz band is a function of the design of the antenna and what you mean by "work". You really need to check the SWR or use an antenna analyzer to know for certain whether or not the antenna is resonant there.
 

teufler

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I doubt it, if you have a swr meter that covers 220, go to low power and check it out. 2 meters would be about 18" at 1/4 wave. 440 is about .5 inches at a quarter wave or about 16 inches at a 3/4 wave antenna, so a 2 meter would sort of work on 440, 224 is about 12" so it is too short for 2 meters and a half wave would be about 24 ', too long for a quarter wave 2 meters
 

jwt873

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Have you checked the SWR at 440 Mhz?

If you're using a low power handheld, a J pole cut for 145 Mhz will 'work' at 440, but even though it's a multiple, I suspect the SWR would be very high at that frequency. Handhelds have a very good tolerance for SWR so you're probably transmitting and receiving OK despite a high SWR.

The same will probably apply to 220 Mhz...
 

bharvey2

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I'd guess your SWR would be out of whack at 220mhz. When i bought a 220mhz radio, I built a new j-pole antenna from scratch. The dimensions were nowhere near that of the dual band j-pole. You can get 50' of 450ohm ladder line and make cheap j-poles to your heart's content until you get one that works.
 

wyShack

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Most antennas will work on or near the 3rd harmonic of their design frequency-not always well but good enough to get by. Most FM and repeater work is 'strong signal' or considerably over the noise -that is one reason squelch circuits can be used. basically, the extra 'losses' of a poor antenna are masked by the extra in other factors. 220 is not harmonically related to two meters so the antenna is not likely to match at all and some type of tuner would be needed.
 

W6SAE

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Thanks for all the informative responses. I've been considering buying a 220 MHz transceiver (since my FT-857D doesn't do 220) and trying to decide whether I'd need an additional antenna as well.
 
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