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I live in a spot where I would be useful for weather spotting, but I can't reach the repeater with a handheld (I can hear just fine, but they can't hear me.) My base is in a detached garage, and I'd like to be able to use it to transmit during periods of severe weather.

I have bare pairs running from the house to the garage, and I know back in the Dark Ages, you could control a radio remotely over the telco using a 20mA loop or something similar. I also have a battery backup for the radio. What I'd like to do is have some gizmo that is powered by the battery in the garage that lets me transmit from inside the house. (I don't need to control the rig, just key the transmitter and send audio.) All the searches I've done wind up involving computers or Ethernet ports or CI-V and what not. What did they call the thing that would sit on the desk to control the radio? Is there a schematic or an article I can refer to?

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    $\begingroup$ What radio is it? $\endgroup$ – hobbs - KC2G Apr 9 at 15:56
  • $\begingroup$ Can you please elaborate on the "bare pairs running from the house to the garage"? Are they twisted pairs? Shielded? And how long are they? $\endgroup$ – Mike Waters Apr 9 at 16:26
  • $\begingroup$ Have you tried a better antenna? A J-pole up higher would be lots better than the rubber duck antenna on your HT, and might enable you to get into the repeater with no trouble. $\endgroup$ – rclocher3 Apr 9 at 17:44
  • $\begingroup$ Are you thinking of a phone patch? $\endgroup$ – rclocher3 Apr 9 at 18:08
  • $\begingroup$ The radio happens to be an IC-706mkIIg, but that's not really important to my question. As far as "bare wires", I run some CAT6 cable. (Actually I ran 2, one for ethernet, one for the now abandoned landline and anything else I wanted.) I have (a now broken) 2m j-pole on the roof. I could go that way, yes. A phone patch is related to what I'm thinking, but no, that's not what I was thinking. $\endgroup$ – Duston Apr 9 at 18:18
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A fair number of base radios can function as a cross-band repeater. If this is the case, and your local regulations allow it, you might not need any cable or gizmo at all.

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  • $\begingroup$ Duston's radio is an Icom IC-706mkIIg which does not have cross band repeat. $\endgroup$ – vu2nan Apr 11 at 4:43
  • $\begingroup$ And just to note, I have enough rigs that I was able to jerry-rig a personal link (handheld to the Icom, and then use the squelch output of the Icom to trigger the PTT on a Drake) but it's clunky. I wanted a simpler solution. $\endgroup$ – Duston Apr 15 at 13:50
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Well, the minimum you need is just... a cable. You can get mic input, PTT, +8V, and ground off of the mic or accessory connectors on the radio, and audio output (if needed; I gather you just want to listen on your HT) from either of those or the external speaker jack. If you put each signal, along with ground, on one pair of the CAT6, and wire up to a microphone connector in the house, it might work 100% okay.

If the cable is too long, the voltage drop might be too much to allow the PTT to key reliably. In that case, you can use a simple NPN transistor switch to help it out — collector to the radio's PTT pin, emitter to ground, one side of your PTT pair to base, and the other side to the radio's +8V through a suitable resistor (small enough that your PTT works, large enough to keep the current reasonable. Maybe 0 for a very long run.)

If your transmit audio is too noisy, or just too low, then you might need to boost the levels on the cable. This is somewhat of a pain, because it appears the 706mkIIg comes with, and expects, a condenser-type microphone. Two routes suggest themselves:

  1. Switch to a dynamic microphone, buy or make a simple mic preamplifier, and connect it between the mic and the cable at the house end. On the radio end, use the MOD input of the accessory jack, and not the mic jack. Crank the preamp level up to a point which brings your voice well above any noise, and then if that level is too much (overmodulates the radio), use a resistor divider to ground to bring it down as needed.

  2. Keep using a condenser mic. Use audio transformers at each end of the cable for isolation. Provide 8V bias for the mic, and a DC-blocking capacitor in series with the microphone. You may or may not still need a preamp.

Speaker (if you choose to wire it) will probably be fine, but if the levels off of the mic or accessory jack are too low, then the rig's "external speaker" jack should provide considerably higher ones :)

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