Scanner Tip of the Week: Plural Radios, Single Antenna

So you really got bit by the scanner bug and have several scanners to really keep tabs on the action. You really want to have a better antenna for them all but don’t want an antenna farm growing on your roof or your attic. What to do?

There are several good ways to share one antenna with 2 or more radios. There are also several bad ways. The bad ways might work good enough to hear some local stuff but that is about it.

The best way to share an antenna with multiple radios is by use of a Multicoupler. A Multicoupler has a connector for the antenna and 2, 4 8 or more ports for radios.Multicouplers allow signals from the antenna to pass thru it to multiple radios and prevents interference between them. “Active Multicouplers” have low power pre-amps in them to overcome the connector loss present whenever you put something between the radio and its antenna. “Passive Multicouplers” do not have the amplifier and will degrade the signal a bit.

Stridsberg makes several models of Multicouplers tailor made for scanners. Stridsberg is the most respected name in scanner multicouplers and ScannerMaster is proud to carry them. Up to 8 scanners can be connected to a single scanner antenna without loss. Check these out at https://www.scannermaster.com/Multicouplers_for_Police_Scanner_Radios_s/43.htm

If your needs are less stringent then you could use a splitter. Splitters are different in that they merely provide a way to share an antenna with two or more radios. These do not have the circuitry to reduce or overcome signal loss. Splitters can usually be used in the reverse way, to allow 2 antennas to feed a single radio, something that multicouplers usually cannot do.

One could just use coax “T” or “Y” adaptors but these provide no protection against interference or signal loss and are not recommended.

Regardless of the methods use there is no substitute for quality cables. Using high-quality coax, both for the downlink from the antenna and for the jumpers to the radios will reduce the loss and increase the signal strength. Don’t forget to use quality connectors if you make the patch cables yourself. Avoid the use of adapters as much as you can, everyone adds a little more loss to the line.

Scanner Tip: Everything you need to know about trunking but were afraid to ask

In the old days of scanning things were pretty simple, you put in the local police frequency to listen to the police. In many parts of the country however, this no longer works. Most cities, many counties and even entire states use Trunking Systems. What are trunking systems and how do they work?

The best way to explain how a trunking system works is the analogy of a set of bank teller lines. The bank has 5 tellers, you can line up at any of the 5 lines and hope your line goes faster than the others. Then you get stuck behind the lady that wants to have her penny jar counted by hand…

These days however, banks have a single queue and you go to the next available teller when you reach the head of the line. This is exactly how a trunked radio system works: All users are in one queue and get assigned the next available channel. Instead of having a separate frequency for the FD, one for the PD and another for the ambulance, they just go to the next channel that isn’t being used.

All this is controlled by a computer system called, appropriately enough, a “Controller”. The Controller watches the system and when a radio requests to talk it assigns that radio and any other radio in its group to a channel. All this happens in a fraction of a second.

Radios have all the frequencies used by the system programmed into them and the system is broken down into various virtual channels, called “Talkgroups”. Talkgroups are assigned to various uses like channels would have been before. For example, Mayberry PD might be assigned Talkgroup 101 for Dispatch, 102 for Car-Car and 103 for Detectives. Mayberry FD might be assigned Talkgroup 123 for Dispatch, 124 for Fireground and 125 for Tactical. If Mt. Pilot is sharing the system they might be assigned Talkgroup 287 for Police Dispatch and so on.

There are several types of trunking systems but they all work in much the same way. There are differences in the way they get programmed into scanners as well. The main types of trunked systems in use by Public Safety agencies in the USA include Motorola, EDACS, LTR, APCO25 Phase 1 and APCO25 Phase 2.

For scanner listeners these trunked systems add a layer of complexity to the programming. Depending on the type of scanner and the type of trunked system the method used to program differs. For newer Unidens you program in a “System” to identify the type of trunking, then “Sites” to put in the frequencies used and lastly “Groups” for the talkgroup listing. Whistler, GRE and Radio Shack scanners with Object Oriented programming work differently. On LTR and EDACS systems you have to identify the proper “LCN” channel numbers, these are usually well documented at www.radioreference.com. Motorola and APCO25 systems do not need the frequencies in any particular order.

HomePatrol and other scanners with the Database feature will have these Trunked System parameters already programmed so you can just select the Service and location to listen to them. They do all the heavy lifting for you.

Keep an eye on the ScannerMaster Blog for our explanation of Digital operations!