开云体育

FT-980 - Low Modulation in AM Mode

VK2MOH All Messages By This Member #67 HI, I buried the following enquiry in another thread so thought it best to bring it to light in its own thread... Operating my FT-980 on AM for the first time this weekend, on-air comments suggested that the rig has a modulation issue. With Mic Gain at max, people commented on poor modulation. I can’t get any action at all on the ALC meter in AM and need to almost shout to get it moving on SSB.?? My first thought was the 0.33uF capacitor but, checking the circuit, this is switched in and out using the Tone Switch. Switching from "1" to "2" made no difference. Could it be the microphone cartridge? How would I test it? Online searching for information revealed very little, it seems this particular microphone (MH-1B8) was not widely used.? Any clues on testing the microphone, sourcing a replacement cartridge or other avenues of enquiry would be appreciated. includes photos and a circuit for the microphone.? If it’s significant, the unit was built in 1985.? ? All the best, ? Mark VK2MOH
Fred, N8YX All Messages By This Member #69 Mark, Do you have another mic to try with your rig? I get more than adequate drive with an MD1- series desk mic and don't have to open up the Mic Gain very far to obtain an ALC reading. 73 - Fred, N8YX
Mat Breton N8TW All Messages By This Member #70 My rig actually came with the MH-1B8 hand mic (the FT-980 standard 600 ohm hand mic) ... I quickly retired it somewhere. I'll try to dig it up. I would not be shocked if the mic element was not in as good a shape as it used to be. I a number of older mics: many have aged well ... but a few have not. Note: if I set my mic gain at max (or anywhere near it) on my FT-980, I will overload the mic pre-amp resulting in poor audio. Any chance this could be it? -- -Mat Breton, N8TW

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