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Author Topic: Which Microphone  (Read 1676 times)
KR4TH
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Posts: 47




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« on: October 29, 2012, 03:17:25 AM »

I have a yaesu 757 MK II and use a yaesu dynamic hand mike, MH-31.  I have been getting poor audio reports, saying my signal sounds compressed and not full audio.  The speech compressor is turned off.  I moved the tone switch on the back of the mike from 1 to 2, and it didn't make any difference. 
 
I also have an old shure 444 in the closet that is wired up for a drake R4TX, which doesn't work (1/4 inch barrel connector).  I just checked the spec sheet on the 757 and it states the mike input should be 500 to 600 ohms.  The shure 444 spec sheet states 1000 ohm impedence.

Is that close enough to work or is that a mismatch?  Would the 444 be a good match to the 757?  I primarily operate cw and am not familiar with mikes, however, I like to have a rag chew on 40 ssb occasionally. 

Jerry
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W9GB
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« Reply #1 on: October 29, 2012, 06:32:31 PM »

You can UPGRADE your MH-31 microphone -- and ADD a Voice Keyer !
http://www.dh8bqa.de/ssp-mh31/ssp-mh31.html
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VA3GUY
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« Reply #2 on: October 29, 2012, 08:57:45 PM »

For what it's worth:  I have a 757GXII also and I use an unmodified Astatic T-UG8 D-104 amplified mic and get excellent reports.  The 'lollipop' gives very high frequency audio out and is good for a DX punch but may not be the best for rag chewing though.

- Guy
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VA7CPC
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« Reply #3 on: October 30, 2012, 02:49:45 PM »

The Shure 444 is (by audio-engineering standards) a "low-impedance dynamic" mic.  The Yaesu 757 expects a "low-impedance dynamic" mic.  No mic bias is needed.

Wire up a cable and PTT switch -- everything should work fine.

The Shure 444 (if I remember right) has a pretty good frequency response for SSB DX and contest work.

I like the sound of the MH-31.  If yours sounds "compressed", there's either something wrong with the mic, or with the rig's settings.

. . . What does your ALC meter read, when you transmit on SSB ?

.               Charles
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AC5UP
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« Reply #4 on: October 30, 2012, 03:32:54 PM »

The Shure 444 is (by audio-engineering standards) a "low-impedance dynamic" mic.

There were several flavors of the 444. The Hi-Z original came in grey and the later Hi-Z / Lo-Z switchable version was in black. EF Johnson offered a custom version of the 444 in brown to match their rigs, and I think those were Lo-Z only.

I've had excellent luck with mine and if needed there's more than enough room in the base to build a one transistor pre-amp.
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KR4TH
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Posts: 47




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« Reply #5 on: October 30, 2012, 05:02:55 PM »

Thanks for ur suggestion and comments.  I will wire up mr 444.  Mine is an older grey mike.  Worked great with drake xmtr.  I will recheck my alc.

Thanks
Jerry
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VA7CPC
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« Reply #6 on: October 30, 2012, 08:45:18 PM »

Oops --

As AC5UP says, there are two versions:

Shure 444 -- a _high-impedance_ mic (100 kilohms recommended input impedance), which is fine for vacuum-tube gear, and would need a matching transformer for good results with solid-state gear;

Shure 444D -- a switchable-impedance mic ("high" or "low"), which should be fine (at "low" impedance) for
. . .     solid-state gear.

I should have started in this hobby about 40 years earlier than I did . . .

.             Charles
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NR4C
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« Reply #7 on: October 31, 2012, 11:49:19 AM »

I suspect that your audio problems are not the fault of the mic.

Most likely are either improper setup of audio controls on the radio or mic technique.

First, hold the mic in your hand close to your cheek.  Talk past the microphone, not into it.  Try to keep the mouth to mic distance constant to insure consistant audio quality.  Don't yell, use a nice casual normal voice.  Talking loud only distorts the sound, and undoes all the work you put into getting good audio from your radio.

Unset all audio controls.  Turn off any compression or processing.  Follow manual on how to set the mic gain, and follow closely.  Once you have the proper gain, get on the air with a friend who knows your voice, and talk.  Try compression or processor to determine of it helps or not. 

You should be sounding like a pro in no-time...

...bill  nr4c
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