----- Original Message -----
From: "hitekgearhead" <[email protected]>
>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
Proportionally, there is less difference between 450 to 470 MHz (20 / 450,
or 4.44%) than there is between
30 to 36 MHz ( 6 / 30, or 20%) or even 42 to 50 MHz (that'd be 8 / 42, or 19%).
Receive won't be affected very much (although you
could measure the difference) but transmitting would have 2:1 or worse SWR.
That's why at home I run a j-pole tuned to 52.52 for FM and repeater work,
and a 3-el Yagi tuned to 50.2 for SSB work. If I tried
swapping antennas for the different modes, I get a 2.5 SWR. I then go oh shoot
and flip the switch back. :-)
(And on-topic, I'm running 1/4 wave antennas tuned for 51.55 receive and
53.25 transmit. :-)
Ray, KB0STN
