Mic Z issue

[Jerry-n5ugw]

I have a FT-902DM which requires 500-600ohms mic input. All newer mics are Hi-Z. What would be a good soluation for this. Audio chain input??? really old Mic??? Which suggested??

[Steve - WB3HUZ]

All newer mics are Hi-Z.

Which newer mics? Most recent vintage pro or semipro type mics (those with an XLR connector) are low-Z and should work FB in your application.

[K3ZS]

A preamplified D-104 would work, they are probably more common than the HiZ ones.   CB'ers used them for "power mikes".   I have found a few at regular flea markets and also at hamfests.

[k4kyv]

And they sound like crap.  A real D-104 is a hi-Z mic, designed to work directly into a 5 to 10 megohm load for a good low-end response.  That power mic junk in the base of the stand is nothing but a distortion generator.

[ka3zlr]

I have a FT-902DM which requires 500-600ohms mic input. All newer mics are Hi-Z. What would be a good soluation for this. Audio chain input??? really old Mic??? Which suggested??

Hello Jerry,

 Before we get Lost with the Input Impedance of yer rig, it is a good time "Now" to sit down and break down the Mic stages of your rig, look at the schematic, and take some time understanding completely what is happening prior to the balanced modulator.

 Now I say that because when i see a question like this come in, I remember when I was first learning About Audio and Audio characteristics and the How to's in application,  Not necessarily do you need to worry yourself about what to apply to the rig, But How to apply it...with that rig you can apply your audio to the input of the first stage if you want, the second stage even better, you can apply your audio to the balanced modulator directly, with a complete outboard system.

 The thing is, What is it that Jerry wants to do,... if you want to create you own sound, take the time to build up a decent system that contains good response, good balance, good compression, good limiting factors..etc...

 What's Jerry wana do OM., with that rig even a good Sure hand mic sounds good..with no work....The 104 head depending on condition, meaning not all 104 heads are or were created equal...and there's the aging element involved now with them, you'll be sorting an segregating heads believe me.

No Power Mic anything here...leave that to the cooper electronic people and the ten meter heads..the free banders....yuk...


73 jack.





 
 

[w4bfs]

hi Jerry ... I agree with Jack ... this is a system question and seems like the time to consider what type of audio mic/processing you plan to use ... from the other thread, I think you are planning to make the 902 your primary (sole ?) am station ... if you want to use the line level input and if Yeasu used the default Japanese standard of 10kOhm at 300mVpp, then you will need to pick up voltage gain ...I would consider some processing as well ... I use a Symetrix 528e and am well pleased ... there are other threads for excellent processors .... in addition, homebrew is not out of the question as well... one final thing... the mic input on most rigs are designed to use electret elements .... the dc power for the electret is "on top of" the audio ... I have rfi problems with those ... some less expensive processors/mixers are susceptible as well ... hope this helps....73 ...JOhn

[Jerry-n5ugw]

Well how shall I'll say this Jack. I have never run a hybred on AM so my experianc is limited. If you think my question is to infentile or to basic for this board, you have choices, do not respond, do not read, or slam the writer. I see no reason to reinvent the wheel if someone with experiance on such a rig has input, not that everyone has the same talents as you. I'm sure the WORLD is in awwww of your AM prowles, for myself I just want to be able to run my Trailer rig and give the listener some clean audio. You see i have to use  Low Balance modulation in my trailer during the week. The current state of jobs in this country has left me with no option but to work out of state to make a living for my family. I got down sized from my mamagement position when the company i served for 25yrs got sold. I did run only plate mod'd rigs,but that wont fit in my trailer. Oh to have my HB 572's moding 813's back. But I'll just keep to myself so I do not disturb your WORLD. Thanks for your learned input, it was helpful in finding my way or learning something new. Oh by the way I have a degree in Electronics and can navagate thru the drawing just fine and really understand what I am seeing. So once again let me say Thanks

[nq5t]

I have a FT-902DM which requires 500-600ohms mic input. All newer mics are Hi-Z.

Jerry ...

Most new radios do have low-z mic inputs.  The 444D is switchable.  Many of the Heil mics are switchable, and the ones that aren't are nominally 600 ohms Z, etc.  I'm surprised finding a suitable mic would be an issue.  Unlike the D-104, which requires a Hi-Z load for the crystal element, matching mics to radios is mostly about levels, not impedance anyway.

Even a D-104 -- some don't like the old preamp that came with the stands, but a good preamp isn't rocket science, and with FET input you can preserve the Hi-z load the D-104 element wants to see for good low frequency response and provide enough drive to the radio, regardless of the radio's mic input Z.

Grant/NQ5T

[Jerry-n5ugw]

Thanks Grant, I'll build up my audio input and get'r done. Just wanted to ask to see what opinions, experiance was out there. Sorry for the very basic question for a very basic application.

[Ed-VA3ES]

Jerrry, I use a pre-amped D-104 with my Yaesu FT-990, and it sounds great (it's a low-Z radio).   I just barely  crank the preamp level, (about 1/4 turn). No one has ever complained.  The audio is crisp, and very articulate with  very little low-end. That's what I want for general QSO use.   I'm not interested in HiFi on SSB. On AM, it sounds fine, but no low end.  If I want low end I go to my plate modulated rigs. 

[ka3zlr]

Well how shall I'll say this Jack. I have never run a hybred on AM so my experianc is limited. If you think my question is to infentile or to basic for this board, you have choices, do not respond, do not read, or slam the writer. I see no reason to reinvent the wheel if someone with experiance on such a rig has input, not that everyone has the same talents as you. I'm sure the WORLD is in awwww of your AM prowles, for myself I just want to be able to run my Trailer rig and give the listener some clean audio. You see i have to use  Low Balance modulation in my trailer during the week. The current state of jobs in this country has left me with no option but to work out of state to make a living for my family. I got down sized from my mamagement position when the company i served for 25yrs got sold. I did run only plate mod'd rigs,but that wont fit in my trailer. Oh to have my HB 572's moding 813's back. But I'll just keep to myself so I do not disturb your WORLD. Thanks for your learned input, it was helpful in finding my way or learning something new. Oh by the way I have a degree in Electronics and can navagate thru the drawing just fine and really understand what I am seeing. So once again let me say Thanks

Well, That's all fine an dandy but I took the original post as a general group question and I can't read Minds.......I asked you "what is it that you wanted to do" and laid out a small "brief" on simple how to's, an a small understanding of a path to chose...in small words Understand the rig, understand what your doing...there's no insult directed at you.

Pardon Me.

[kb3ouk]

I use a D-104 with the preamp on an FT-901DM, and it will work if you keep the preamp at about 1/4 of the way open and keep the gain on the radio down fairly low.
at about a quarter way open, and the rig's mic gain down low. The main problem i have is that the audio wants to pop if your voice peaks are too lioud when the gain is just slightly too high.
Shelby KB3OUK

[ka3zlr]

Those Preamplified stands are great for one thing, if ya need an extra 40 - 50 bux off of ebay,... especially if ya find one in decent condition  . I guess they're ok if you have a sound proof room an little backround, but they drag in every noise and movement in the immediate area, all they do is drive the pants off the first stage of these rigs and your always turning knobs, they have no balance, no limiting effects, no compression, nothing...there is however some mods on the net I've done that do calm those down a bit...but for radio listening I think those things are irritating...but that is just my observation...

 That Rig is capable of so much better sounding AM with a few simple Mods a little reversal of the ALC, Line Audio feed with good Transformer matching and a little time.

[kb3ouk]

I was thinking about tearing the amp out of mine and running it straight from the mic element to the radio, without that amp in there.
shelby kb3ouk

[KF8XO]

Well how shall I'll say this Jack. I have never run a hybred on AM so my experianc is limited. If you think my question is to infentile or to basic for this board, you have choices, do not respond, do not read, or slam the writer. I see no reason to reinvent the wheel if someone with experiance on such a rig has input, not that everyone has the same talents as you. I'm sure the WORLD is in awwww of your AM prowles, for myself I just want to be able to run my Trailer rig and give the listener some clean audio. You see i have to use  Low Balance modulation in my trailer during the week. The current state of jobs in this country has left me with no option but to work out of state to make a living for my family. I got down sized from my mamagement position when the company i served for 25yrs got sold. I did run only plate mod'd rigs,but that wont fit in my trailer. Oh to have my HB 572's moding 813's back. But I'll just keep to myself so I do not disturb your WORLD. Thanks for your learned input, it was helpful in finding my way or learning something new. Oh by the way I have a degree in Electronics and can navagate thru the drawing just fine and really understand what I am seeing. So once again let me say Thanks

Breath Jerry...BREATH...

[WU2D]

Like Don encourages, the D-104 will have a beautiful response into a nice Hi-Z device like an FET or a tube grid.

The good old MPF-102 into a bipolar emitter follower would be hard to beat in this role and it could go in the base of the microphone. Astatic tried this with the early preamplifier mics but it was an early all bipolar attempt, which never quite did the job in terms of response. It did allow the mic  to drive the SSB rigs of the day, however.

Likewise, Electrets can be mismatched. They like to see a fairly low impedance. I have used the common base bipolar amplifier for electrets with good success.

Mike WU2D