Bidirectional Inband repeater

[Jay G.]

Hello and thanks for taking the time to read this.

I run a small volunteer security group. We use 2 simplex business band frequencies which we are licensed on: ie: 461.000 and 466.000.
We are going to be working an event at two local separate locations and want to keep each event on it's own channel, but have the ability to speak to each other. Cant make it a "real" inband repeater because some of the radios we use are RDU2020 radios which cant be programmed for a repeater - Have no choice but to stay simplex.

Heres what I came up with - tell me if it makes sense:

2 CDM1250 radios, set at 10 watts, one on 461.000 and one on 466.000. Motorola RICK set to bidirectional mode. Duplexer tuned to frequency.

Operations at location 1 are on 461.000 and location 2 at 466.000. Anything at location 1 is sent out by repeater to location 2 on their frequency and vice versa.


Make sense? Sounds to me like it will work.
Any other suggestions or comments??

Thanks to all!

[The Pager Geek]

Yup, either get some decent antenna separation or a standard 5MHz duplexer and you should be good to go.

tpg

[N4DES]

What are you licensed to? If it is just mobile (MO), then operating these as what I would believe as FB2's would not be legal.
Sure sounds like it would work operationally as long as no one gets too winded.

[emtprt]

I would check with your local radio shop to rent portables and a repeater for the event. Most larger shops have portable repeaters on their license with a cache of radios. The typically have a license that covers an entire state or multiple counties in their service area.

The radio shop also hase the ability to program multiple channels in the radios allowing channels for operations, parking, escorts and administration. Thay may also be able to provide multiple repeaters for each group or geographic region.

I helped at a Special Olympics event which had 9 channels and 5 repeaters to cover events and a large geographic area. The whole project was setup in for hours and proved to be worth every penny

[AEC]

All radios can be configured for repeater duty.
One transmitter, one receiver.
The ancillary equipment are the controllers, duplexer and feedline/antenna.

You need to feed RX audio INTO the transmitter, at the approrpriate level, and at 461.000/466.000 business, that would be narrowband, IE...2.5 Khz deviation.
Adjust the transmitter to no more than 2.3K max deviation as some voice peaks can exceed the 2.5 K max. The occupied bandwidth must stay below the 12.5 K channel bandwidth, and deviation above 2.5 can cause excessive excursions from the maximum channel bandwidth and cause IMD products to nearby channels also.
Run a service monitor to check for SINAD on your system, to ensure proper operation, good receiver sensitivity and no in-channel distortion products are being generated.
Tuning the cans require a stable frequency and power from the monitor, and regardess of some, running ful power while tuning ANY duplexer can cause burns and arcing inside the cavities, which produces dead spots and prevents tuning in this area. Arcing also creates IMD products under load and spurious emissions.

Improper tuning of cavities also prevents any system from operating at peak perforance, robs transmitter power and creates desense to the receiver, limiting range of that system.