Transmitting through a multicoupler with scanners attached?

[a_jones]

In my vehicle I have 2 Pro-2055s and a HomePatrol attached to a Stridsberg multicoupler and the Larsen tri-band antenna on a Comet hatchback mount. It all works beautifully.

I now need to add my Kenwood TK-880 UHF radio to the equation. The easiest way would be to use a BNC adapter and connect it to the 4th port on the multicoupler. Will I destroy my scanners if I do this? It transmits at 25 watts. I would prefer not running another antenna.

I'm already using my 5 watt TK-380 inside the vehicle and nothing has gone up in flames yet. Ay suggestions?

[a_jones]

It's a Stridsberg MCA204M, to be specific

[jackj]

You do what you want but that thing isn't a bi-directional coupler. I would be very surprised if you haven't already burnt out the preamp by feeding RF into the output port.

[cg]

They are receive only, do not transmit through it.

chris

[KI4VBR]

You will destroy the Strids.....I did it with a 5 watt handheld. It didnt fry anything (no smoke), but the sensitivity of the 4 outputs was gone....no signals, no nothing but white noise. I only keyed up the FT60 handheld for about 2 seconds before I realized the mistake I was making. That was all it needed to turn the unit to scrap.

Dont make the same mistake I made.

Vince

[n5ims]

First off, a multicoupler isn't designed for transmitting, only receiving. If you transmit you'll probably blow the attached scanners as well as the multicoupler.

One possible option (and not a very good one) is to get a duplexer (this is one example --> MFJ Enterprises Inc.) and place it between the multicoupler and antenna. The TK-880 would attach directly to the duplexer's UHF connection and the multicoupler would connect to the duplexer's VHF connection. Your scanners would only work on the VHF-Hi band (or lower) and your UHF radio should work as expected.

You'll need to pick the duplexer carefully since they come with different frequency ranges and some are not designed for multiple radios, but to connect multiple antennas (of different bands) to a single radio. The difference is critical since those designed for a single radio may not have the necessary filtering to prevent the transmitted signal from reaching the scanners.

[a_jones]

Ok - thanks for the warning everyone. I haven't tried it yet, because I suspected that might happen. All the departments in my area are UHF, so it looks like I may have to bite the bullet and look at mounting a 2nd antenna. Fortunately I can just go with a UHF 1/4 wave that will be smaller than the Larsen.

[a_jones]

Originally Posted by a_jones

I'm already using my 5 watt TK-380 inside the vehicle and nothing has gone up in flames yet.

I meant to say that I'm using the handheld with its stock antenna while sitting inside my vehicle. I'm not connecting it to the Stridsberg. I do notice, however, that when I key the mic my scanners stop receiving, which I find odd...

[Ed_Seedhouse]

Originally Posted by a_jones

I meant to say that I'm using the handheld with its stock antenna while sitting inside my vehicle. I'm not connecting it to the Stridsberg. I do notice, however, that when I key the mic my scanners stop receiving, which I find odd...

I don't. Heck, my scanner goes quiet if I transmit on two meters within a couple of feet. A hundred feet from the main police transmitter downtown and it is overloaded.

If I hold my HT near my computer speakers and transmit with the rubber ducky on, the speakers stop producing sound.

These scanners front ends are designed to handle signals down in the millionths of a volt. They are not designed to handle a transmitter right next to them.

[beachmark]

Yes, a scanner input will typically start 'blocking' somewhere in the range of -30 dBm + or - , which is in the 1-20 millivolt range; it'll vary quite a bit between units. That is easy to do with any nearby transmitter. It is a good way to damage nay receiver front end. The front end blow up range can be as low as 0 dBm (around .25 volts).