Simple Coax Antenna Gain & Vertical Bandwidth

I have a simple coax cable with the shield taken off and the center wire is acting as an antenna. it is in the L-Band (1.7GHz - 1.85GHz) and I need to know the gain as well as vertical beamwidth. I've looked at numerous sites and can not find any information so is any one has a good guess it would be greatly appreciated.

Assuming what you mean is a quarterwave whip?, then it has a gain of unity (compared to a dipole) and is omnidirectional horizontally, and fairly wide vertically as well (no idea how much, it never applies).

Nigel's response is likely to be sufficient for your needs. If not you might take a look at resources for radio amateurs. There are quite a number of antenna modelling methods - and some free software available to ease the burden of calculations.

Antenna gain is achieved with focussing in a narrow beam. Like the dish for a satellite receiver. A Yagi antenna uses many director elements to focus the signal direction. I have seen stacked Yagi antennas on apartment buildings which focusses in a narrow vertical angle.

for 2.4GHz usualy a small λ/4 omnidirectional antenna that comes with WLAN cards is about 2dBi... if your cable is not in the right size probably you will not have good reception.

Unfortunetly I need a number for the gain which I guess I will use 1, as well as a vertical beamwidth. This is for military paperwork (DD1494) so we can get our camera system to be tested out in the US as well as overseas. I highly doubt that just giving a educated guess is going to cause a problem as our transmitter is good for ~300 yards at best. One would think the company we bought the transmitter from would have this information but no.

Thanks for all your input.

Just a note of caution - sometimes an isotropic radiator is used as the point of reference - sometimes it's a dipole - they are not the same. As I recall, dbi refers to isotropic. In some situations we can assume the reference level if none is stated - I don't know what the industry standard would be if the reference level is not stated.

Worth noting - the performance of an antenna as might be measured or experienced some distance from the antenna is quite dependent on things like nearby objects, height above ground or a ground plane, among other things. The position of a 1/4 wave radiator - vertical, horizontal or in-between, would affect performance. From my experience (limited to hobby) manufacturers may make a statement about gain, beamwidth, etc - the better manufacturers are able to describe the conditions that are the basis for those claims.