User's Manual

Page 4
SVR-200 Service Manual
Functional Description
Generally, vehicular repeaters are used as mobile extenders in cross-band operation: the link is
VHF/UHF/800 MHz simplex and the mobile is Lo-band, VHF, UHF or trunking. In-band operation is possible,
but care must be taken to prevent interference between the mobile's higher power transmitter and the repeater
receiver. Proper frequency selection and antenna placement are important even in cross-band operation, but
especially for inband use. The use of low power pre-selector cavities may be placed in line with the repeater
antenna cable since it is simplex and low power.
Important Note
The SVR-200 operates on simplex frequencies; part of the multi-vehicle format dictates that all of the
SVR-200s must be able to monitor all link traffic on site and be able to determine if a handheld is transmitting,
or if other repeaters are transmitting. The handhelds must transmit CTCSS, but should be carrier squelch
receive. The handhelds should not use CTCSS decode if the repeater is utilizing the multi-vehicle format,
as this will interfere with the priority sampling which is essential for multi-vehicle operation. Also, the
handhelds would have to have different encode and decode tones in order for the repeater to be able to tell the
difference between handhelds and other repeaters, so the handhelds would not be able to hear each other. The
repeaters should not transmit CTCSS unless used only in a single vehicle environment.
When the user leaves the vehicle, they activate the SVR-200 via their mobile radio front panel or a separate
switch. When the mobile radio is receiving carrier and proper tone, the SVR-200 will begin transmitting on
the handheld’s receive frequency. The user is able to hear and respond to all radio traffic, including other
handhelds at the site. The SVR-200 can be programmed to give the handhelds priority in a conversation by
periodically sampling for handheld activity (carrier and proper tone) during base to handheld transmissions.
During sampling, if the SVR-200 detects a handheld transmission, it will cease transmissions, key the mobile
radio and repeat handheld to base. This allows the handheld to respond during repeater hang time or during
full duplex interconnect calls. Priority sampling can be enable/disabled through PC programming and the
interval can be programmed between .25 seconds and 2.5 seconds in .25 second increments.
The SVR-200 has a fixed 3 minute time out timer for base to handheld transmissions. If the mobile COR
is active for more than 3 minutes (and the SVR-200 is the priority unit) it will send a double blip and cease
transmission until the mobile COR is inactive. The 3 minute time-out is in affect regardless of whether the
SVR-200 is programmed for priority sampling or not.
Multi-vehicle operation
When the SVR-200 is first activated, it will transmit a short “lock tone” that alerts the user that the system is
functioning. It will then assume the priority status and be ready to repeat any base to handheld or handheld
to base transmissions. If another unit arrives on scene and is activated, it too will transmit the “lock tone”;
when the first SVR-200 detects the lock tone from the second unit, it will increment a “priority counter” and
will no longer repeat any transmissions. The recently arrived unit will be the priority repeater, and the first
unit will be 1 count away from priority. This process will continue for each unit that arrives at the site, creating
a priority hierarchy for up to 256 vehicles, each with a unique count and only one unit at priority status. The
SVR-200 will not transmit it’s lock tone if the radio channel is busy when first enabled. It will wait in
non-priority status until all transmissions cease, then send its lock tone and become the priority unit.
Even though the other SVR-200s are not at priority status, they will continue to monitor the channel for
activity. If the priority unit were to leave the scene or become disabled, the other units will detect the condition
to repeat and determine that there is no priority unit repeating the transmission. They will then begin
decrementing their priority counters until one of them reaches the priority status and begins repeating the
transmission. Since the SVR-200s are all at different counts, only one will reach priority status and begin
transmitting. The other units will sense the new priority repeater and cease counting down, preserving the
priority hierarchy.