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© DELARA News, the official monthly newsletter of the Delaware Amateur Radio Aassociation, Delaware, OH
delara news Delaware Amateur Radio Association, Delaware OH   VOL 33  NUMBER 2 


Bob Dixon  W8ERD

Updates to the Tactical Communications Bridge

Port 1 of the TCB is reserved for the console microphone and loudspeaker, which are wired internally. Yet that port has the same external connector as all the other nine ports, so the question arises, what does that connector do?  Normally it is unused. Study of the manual reveals that connector has the same functions as all the other ports, but they caution you not to use them "because the audio input will appear in parallel with the microphone, and CAUSE CONFUSION". Being already hopelessly confused, I tried connecting an audio input there. Sure enough, it comes out in parallel with the microphone audio. But it uses the same audio gain control, so you cannot balance the external audio and microphone levels properly. And of course you would not want the external audio source to be blatting in on top of the microphone all the time. And I found the external source loads down the microphone audio somewhat, probably because my source was not very high impedance. Here is a problem that can be turned into an opportunity! I connected a little 4 channel external audio mixer to the TCB port one connector.  Its output impedance is high enough that it only slightly affects the microphone audio, easily fixed by turning up the internal microphone gain control. Then I connected 4 external receivers of various kinds to the 4 mixer input ports. I had to find an audio output connection on each receiver where the audio output level is constant, not affected by the volume control, and also where the squelch works.  These are labeled things like "tape out", "line out" etc.  One of the receivers was a problem because its squelch did not apply to the constant level output port. But it has isolated relay contacts intended to turn a recorder on and off, when the squelch operates. So using a little 12VDC relay in series with the audio output, I was able to achieve squelch action on that receiver. The mixer has separate gain controls for each channel, so it is easy to set the audio level for each one appropriately. The connected receivers are: 1 - AOR AR5000.  10 KHz - 2600 MHz, all modes. 2 - Bearcat BCD996XT. Trunked radio.   25-1300 MHz. 3 - Icom R8500.  100 KHz - 2000 MHz, all modes. 4 - Yaesu FT-920  100 KHz - 56 MHz. Any or all receivers can be used at once, to send audio out to any transmitter or phone line. Some examples of possible uses are: Monitoring AM and FM broadcast stations in nearby counties for disaster information. Monitoring Police, Fire etc stations as above. Monitoring utilities such as electric companies. Monitoring the airport and airplanes. Monitoring ham nets such as the Hurricane net I am sure you can think of others; please make suggestions. Using receivers for monitoring frees up transceivers for other purposes as needed. Now what about that still unused connector in parallel with the console loudspeaker output? We can't have any  connectors just sitting around unused! Maybe we connect a recorder there?   Suggestions welcome!