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Paul F

Adding an antenna to Mic/Line input - IFB Xmitter

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I have both a portable and rack unit IFB transmitter. I use a dipole on the rack unit. The portable unit uses the microphone/line input as the antenna. I am feeding line input from a Zoom F8 to the transmitter. The portable unit's range is poor (unusable). Is there a way for me to make up some type of T connection that would allow me to add a dipole antenna to the line input to the transmitter?

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And first thing this morning, I had the answer from Listen Technologies. They are providing me instructions on how to do it. Good folks.

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2 hours ago, Paul F said:

And first thing this morning, I had the answer from Listen Technologies. They are providing me instructions on how to do it. Good folks.

Great! manufactures tend to know their product best!

Please share that info here too, I also have an LT700 kicking around for extra comtek feeds, and would love to know that info

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This can be done for the transmitter or receiver. Their instructions provided a way to add a wire  antenna directly out of the case or a way to add a BNC coax cable wired directly to the board and out through the battery case. I didn't care for either of those. Here are my modified instructions. I haven't tried this yet. I'm waiting for the SMA connector.

 

LT-700 Instructions:

 

1. Open the case by removing 4 screws under the battery cover.

2. Remove the back cover.

3. Disconnect the transmitter board from the main board. There are no fasteners. It is held on by connector friction.

4. Remove C8 from the transmitter board. The board is marked LT700-TXRF. C8 is located next to the larger of the two connectors (J1, see picture)

5. Remove the plug of plastic covering the antenna hole. (see picture). This location is used for an antenna on the -863 version of the LT-700

    5a. I'm assuming an SMA connector is going to fit in there, but I won't know until I get it.

    5b. Install the SMA connector in the antenna hole.

6. Attach coax center lead to the back side of pin 1 of J1, which is the pin closest to C8. Connect that lead to the SMA connector.

7. Attach coax shield to the ground plane of the circuit board near pin one and to the SMA shieldLT-700 Modification.jpg. The back side of the transmitter pcb board is the ground plane. You'll have to scratch off some of the green mask according to them, but I haven't looked for a better location.

8. Reassemble the unit.

 

Receiver instructions are the same except instead of removing C8, remove L8 which is next to J2. I don't know if receiver cases are the same and have the antenna plug. I'm too lazy to go to the shop and look.

 

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My concern is losing or not being able to solder C8 back on if I'm not satisfied with the change. I'd rather cut a trace. I'll poke around and see if there is another way to make the C8 disconnect without removing C8. I won't pull the plastic plug until I'm sure this works decently.

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