Message posted by gary on July 22, 2001 at 21:11:00 PST:
Generally when a frequency counter has trouble, there is more that one frequency active. This is nearly always the case with trunked radio systems, i.e. the data channel is active as well as at least one of the trunk channels. What you could do is simply band scan the 400Mhz region with no antenna attached to the radio. No antenna means anything you pick up is probably local. The filters in the scanner will take care of the multiple frequencies. Note that 615Mhz is in the UHF TV band. The spacing of the elements is probably an attempt to get a downward tilt in the signal. The 4 stacked folded dipoles is a high gain antenna, but high gain tends to force the signal out to the horizon. Envision a donut shaped radiation pattern. The is ok unless the antenna is much higher in elevation that the mobile unit. In that case, the signal may go right over your head. Some designs tilt the antenna, while others insert delay lines (precise length of coax) to make the signal tilt electronically. Note that the stacked folded dipole is used for sites that require good HT (handy-talky i.e. hand held) performance. This kind of antenna is total overkill for mobile units.
In Reply to: Re: janet planes at TTR posted by Joerg (Webmaster) on July 22, 2001 at 20:30:51 PST:
Replies: