Body Mic Receiver

[srievley]

I am getting ready to outfit an undercover vehicle. The receiver for the body mic (wire) has a BNC connector on it. The two way radio is a CDM1250 and we always use Moto 1/4 wave antennas. I can install two of these antennas but have the one for the body mic receiver have a BNC on the end. What I would like to do is run this wire inside a trim panel and terminate it with a bulkhead BNC. Then, when the receiver is used, I can run a short cable between the bulkhead connector and the receiver. I like this idea because I don't have to worry about the cable laying in the seat when not in use. My concern is the signal loss from using the extra connectors. The receiver needs to be as sensitive as possible. Any thoughts or suggestions are welcomed. If it matters the receiver is made by Swintek.

[Jim202]

I am getting ready to outfit an undercover vehicle. The receiver for the body mic (wire) has a BNC connector on it. The two way radio is a CDM1250 and we always use Moto 1/4 wave antennas. I can install two of these antennas but have the one for the body mic receiver have a BNC on the end. What I would like to do is run this wire inside a trim panel and terminate it with a bulkhead BNC. Then, when the receiver is used, I can run a short cable between the bulkhead connector and the receiver. I like this idea because I don't have to worry about the cable laying in the seat when not in use. My concern is the signal loss from using the extra connectors. The receiver needs to be as sensitive as possible. Any thoughts or suggestions are welcomed. If it matters the receiver is made by Swintek.

Any connector introduces a slight loss. The quality of the connector and the quality of the work by who made up the cable connections is probably more important than worrying about the connector loss. One trick that many don't realize is that BNC connectors tend to leave a black type film on the inside of the connections with use. If you take a cotton swab and some alcohol to clean out this film deposit it will improve your performance. Makes a big difference in the transmit side of the use of these connectors.

If you have a portable radio using a BNC connector, pull of the antenna and look at the connection on both the radio and the antenna. You might be surprised at what you find.

Jim

[Bill_G]

Insertion loss for BNC connectors is quite small. On the order of .2db for good quality connectors. I wouldn't worry about it especially if you follow Jim's advise to keep them clean.

[motorola_otaku]

First and foremost, use good cable. Teflon RG58, Times LMR195/200, and RG142/400 are all acceptable. If you're using a NMO-mounted antenna, use a continuous-impedance NMO mount too. What you reclaim in the cable alone over cheap RG58 should adequately compensate for any miniscule loss induced by a couple of BNCs.

On the connector itself, use a RF Industries nickel-silver-Teflon part. The difference between them and nickel-Delrin is tiny, but hey, if every little bit counts..

[srievley]

I was planning on using a Moto 1/4 wave kit, 4008 I think. Is the coax and nmo in this kit any good? We have several of these already as we use them for all our CDM1250 installs. My particular install will be to receive only, no transmitter at all. A seperate antenna will be installed for the CDM1250. They will be spread out as far as possible on the roof of the vehicle.
Thanks to everyone who has replied.

[Bill_G]

The mount and cable are fine, but I would use a gain antenna.