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Author Topic: Can I Monitor Mic Audio on Yaesu FT-857D ???  (Read 1354 times)
WB2WIK
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« Reply #15 on: March 08, 2010, 03:23:56 PM »

The MONITOR function on the "larger" rigs that provide this aren't just tapping into the mike line.

They're monitoring what the transmitted signal actually sounds like, including processing and other variables, and also including distortion introduced along the way.  It's like turning on a part of the receiver to listen to your "on air" signal without having to use a second receiver.   This feature doesn't come "free," it involves additional circuitry that has cost.

That's why it's normally not found in smaller rigs (at least, not to date).  Most of the "larger" home-station rigs do include it.

For simply "recording both sides of a contact," you can just tap into the mike line.

However this provides no useful signal for an oscilloscope to display.  If you want to make "transmitter adjustments," you need to monitor the RF coming out of your transmitter!
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KD8MJR
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« Reply #16 on: March 08, 2010, 03:39:38 PM »

But can I just Tap into the Mic's line like that?  I figured it would change the impedance that the Mic element see's and mess up my audio??
At this point I would settle for easy recording and forgo the oscilloscope if need be, but will the Mic tap really work with no issue's ?
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WB2WIK
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« Reply #17 on: March 08, 2010, 04:10:41 PM »

Why not?  If it reduces the drive from the mike to the 857D, turn the mike gain up higher to make up for the difference.

Or of course you can prevent loading by just using a large series resistor and driving a Hi-Z preamp; that wouldn't load the mike at all.
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KF6QEX
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« Reply #18 on: March 08, 2010, 05:14:20 PM »

>and mess up my audio??

Well...you can always use a second receiver to check that!
Sorry couldn't help it Smiley
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VA7CPC
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« Reply #19 on: March 08, 2010, 11:12:32 PM »

But can I just Tap into the Mic's line like that?  I figured it would change the impedance that the Mic element see's and mess up my audio??
At this point I would settle for easy recording and forgo the oscilloscope if need be, but will the Mic tap really work with no issue's ?

I think Steve (WB2WIK) is right.  The FT-857 uses a low-impedance dynamic mic (MH-31, nice sound), and the spec for the transmitter says:

. . . Microphone impedance:    200 - 10K ohms (nominal: 600 ohms)

So they've designed the FT-857 mic preamp with a fairly high input impedance, and lots of gain.

A second high-impedance amp, driven by the same microphone, should work fine to get your mic signal into a recorder.

This is a good application for a small Behringer mixer -- use its mic preamp on one channel, use a second channel to "ride gain" on the received audio from the DATA OUT pins, and mix the two channels into an output that you feed to the recorder.

RFI might be a problem -- be warned.

                         Charles
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KD8MJR
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« Reply #20 on: March 09, 2010, 11:02:07 AM »

"RFI might be a problem -- be warned."

Ok now I am not sure what to do....  Go back to the PC mic idea?
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AI7RR
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« Reply #21 on: March 09, 2010, 04:00:15 PM »

I can't speak for the 857, but a lot of rigs use the MON function to feed the mic audio into the headset output. Perhaps the 857 does this also. If that's the case, a high impedance tap off the the headset socket would provide both tx and rx to the soundcard or station monitor.

73,, Roger
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VA7CPC
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« Reply #22 on: March 10, 2010, 01:42:04 AM »

Quote
Ok now I am not sure what to do....  Go back to the PC mic idea?

I think that's the cheapest, easiest thing to try.   I don't know how you'll mix the PC mic signal (your voice) with the rig's output (the received signal), into the recorder input, but I'm sure you'll figure out a way.

If it doesn't work, _then_ try something more sophisticated.

This is _ham radio_ -- we don't need an "optimum solution", we just need something that works.

                 Charles
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