Paul F Posted May 9, 2020 Report Share Posted May 9, 2020 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? Quote Link to comment Share on other sites More sharing options...
Shastapete Posted May 9, 2020 Report Share Posted May 9, 2020 You need to be way more specific than "IFB transmitter" what manufacturer and model number is it? Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 9, 2020 Author Report Share Posted May 9, 2020 Listen Technologies LT-700. Quote Link to comment Share on other sites More sharing options...
Derek H Posted May 11, 2020 Report Share Posted May 11, 2020 I would email listen tech. They’re pretty responsive. Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 11, 2020 Author Report Share Posted May 11, 2020 Thanks. I had that same thought earlier today. Indeed, they are very responsive. Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 11, 2020 Author Report Share Posted May 11, 2020 And first thing this morning, I had the answer from Listen Technologies. They are providing me instructions on how to do it. Good folks. Quote Link to comment Share on other sites More sharing options...
Shastapete Posted May 11, 2020 Report Share Posted May 11, 2020 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 Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 11, 2020 Author Report Share Posted May 11, 2020 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 shield. 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. Quote Link to comment Share on other sites More sharing options...
Shastapete Posted May 12, 2020 Report Share Posted May 12, 2020 A lot more than I expected but not too scary – my only fear is i'd "brick" my transmitter when removing components. Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 12, 2020 Author Report Share Posted May 12, 2020 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. Quote Link to comment Share on other sites More sharing options...
Derek H Posted May 12, 2020 Report Share Posted May 12, 2020 Cool! Share a pic with the SMA in place if you manage it. Quote Link to comment Share on other sites More sharing options...
Paul F Posted May 31, 2020 Author Report Share Posted May 31, 2020 Quote Here is the LT-700 with the SMA installed. I decided to use coax. The connection is made on the other side of the board; pin 1 of the connector on the right side of the picture. It's not easy with coax. I used semi-rigid coax. The back half of the connector that is used for a crimp had to be ground off and the shield of the coax was soldered to the remaining bit of connector. You can see full connector in the middle of the picture to compare what I ground off. The coax has to make a sharp bend to get under the PCB. The beat up G3 IEM and antenna wire will be discussed in another thread. A whip antenna gave me the same results as the microphone antenna. I'll be trying a dipole sometime later, which was the point of doing this. Quote Link to comment Share on other sites More sharing options...
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