Hi Al, The most simple explanation is, the higher you go in frequency, the wider the band width. This is also relevant to the diameter of the metal of the antenna structure. The fatter it is, the more the bandwidth will increase. On low band frequency's you really really have to get it "Fat" to increase the bandwidth. As an example a standard Mobile whip (Not a HT antenna) at 50 MHz, may yield a 1.5 to 1 VSWR over 3 MHZ. to increase it to 5 MHZ you would need to increase the diameter to about the size of about a 1/4 inch pipe. Thats why you would see better bandwidth characteristics in a 1/4 tube constructed antenna than that of the type of a mobile whip. at same frequency.
So Again thats not the exact true to a formula explanation but it gets the picture in the minds eye of the electrical characteristics of an antenna, I hope its clearer not muddier :-) Richard ________________________________ From: hitekgearhead <[email protected]> To: [email protected] Sent: Wed, June 30, 2010 10:58:06 PM Subject: [Repeater-Builder] lowband HT antennas I know I am revisiting this again but I could use some clarification. It has been stated before that the Motorola low band helical antennas have a useful bandwidth of about 1MHz. I was just wondering why that was the case, say in comparison to HT antennas in other bands. For instance, (and correct me if I am wrong) the mid UHF (430-470MHz) radios often all use the same 6" 1/4 wave whip. What am I missing? I know that the first type of antenna is loaded and the other is a 1/4 wave whip, but beyond that I don't understand the fundamental differences that would allow one a wider bandwidth over the other. Please pardon my antenna theory ignorance Also, in relation to that, what use would be a 99 channel MT1000 unless one either programmed the frequencies on quite a narrow spread, or carried multiple antennas? Thanks in advance, Albert
