DE
DANIELS
ELECTRONICS
VT-4R150 VHF Project 25 Digital Transmitter Instruction Manual
4-3
separate control of their channel select lines, so changing receiver channels does not affect the
transmitter channel.
Q: Why is the transmitter staying on after the receiver signal is removed?
A: The transmitter has a hang timer that keeps it keyed after the receiver signal disappears. This
can be used to keep a chain of repeaters up between transmissions. The delay is adjustable from 0
to 3.75 seconds.
Q: What’s that noise at the end of a transmission?
A: The transmitter can insert an audible “kerchunk” at the end of a repeater transmission. In
Project 25 digital mode, this simulates the effect of the squelch noise, which is heard at the end of
an analog repeater transmission. In analog systems, the squelch noise is the sound of the
receiver’s IF noise before it squelches. This is often useful as a confirmation to repeater users that
they have “hit” the repeater. In Project 25 Digital mode, no noise is heard at the end of a
transmission due to the all-digital nature of the system, so an artificial noise is added to serve the
same purpose. There is a jumper on the transmitter’s microprocessor board to disable the
kerchunk noise.
Q: Why is the Radio Service Software failing partway through a read or write of the receiver?
A: If the receiver is squelching and unsquelching repeatedly during the read or write operation, the
communications bus may be too congested. Try changing channels on the receiver, or disconnect
the RF signal source from the receiver during the read or write operation.
Q: Why does the transmitter not transmit with the correct TGID or NAC, or in the wrong mode?
A: In a typical repeater, if the received signal is digital, the transmitter will be keyed from a bank B
channel, NOT from bank A, even though the receiver may be receiving on a bank A channel.
Make sure that for each transmit channel number, both the A and B bank are programmed with
analog information and Project 25 information, respectively.