Using Yaesu MD-100 mike for Kenwood TS-850

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Jan De Smet:
I bought a new Yaesu MD-100 table mic at a hamfest yesterday.
I own a Yaesu FT897 for Maritime Mobile use, and this table mic works fully with it, including the scan/fast ans slow freq tuning via a sliding ring on the mic.

But I want to use it on my fixed station Kenwood TS-850 rather then on the FT897.

My questions:
- can anyone help me with wiring diagram of the MD-100?
- the mic accepts a 5V fixed voltage from the FT897 tcvr plug but I suspect this is only used for some active filtering that the mic is capable of (not for the scan function?)
- with the Kenwood I don't need any Up/Down freq tuning from the mic (which the stock portable mic is capable off) but I would like to keep the filterin capabilities of the MD-100
- the Kenwood mic plug has a pin that supplies 8V fixed voltage but I think it is not used in the stock mic. Up/Down tuning can be done via switching pin Up or Down to Grnd. Is this correct?

- if I need 5V for the active filtering in the MD-100, how can I bring Kenwoods 8V down to 5V? Via a voltage divider or by measuring the current used in the MD filtering module and from this calculate its resistance, and then calculate the resistor I have to put in series with this module to bring down the 8V to 5V?

TNX for any help,

Jan
ON3ZTT

Robert Anderson Jr:

mic                        
1 up                      
2 +5v                      
3 down                    
4 fast                        
5 ground                  
6 ptt                      
7 mic shield              
8 mic audio                

Radio
4 Up
5 8v
3 down
6  NC
8 Gnd
2 PTT
7 Mic Shld
1 Mic Audio

I dont Know if the up down buttons will work or not (Try at your own risk)

but you Do need a voltage source to supply power to the microphone for the mic element to work So you could probably add a 5v zener diode between pins 2 and 5 inside the mic.  

Floyd Sense:
Go here for everything you ever wanted to know about microphone connections: http://homepage.ntlworld.com/rg4wpw/date.html

The MD-100 uses a dynamic microphone cartridge and doesn't need a supply voltage to work.  If I were you, I'd first get it working in THRU mode.  The +5V is required to run the op amps in the filter circuit.  Use a small 3 legged regulator to drop the voltage to 5V, or you could use a zener diode.

Jan De Smet:
That is what I suspected, that the 5V is only needed for the filtering circuit.
Since the Yaesu MD100 mic also has a scan/Up&down switch (or circuit) I think it would give trouble trying to wire this to the Kenwood TS-850 Mic circuit.
The yaesu FT897 mic plug has 1 pin for this called 'Fast', it can switch the TF897 into fast up/down tuning and if switched for > 1 second it switches off the FT897. hence it behaves like the FT897's Power on/off switch does.
I don't think this would match the kenwood wiring at all, and since it is to be used as a base station mic, I don't need the tuning ability from the mic, so I will leave those out.

But yes I would like to keep the filtering circuitry.
Since I want to keep the MD100 yaesu connector intact to use with my Yaesu897 just-in-case, I will make an adaptor cable. So I would need to incorporate the voltage drop down circuitry in the adaptor cable.

Could anyone provide me with simple schematic for a voltage regulator bringing the 8 V to 5V, or how to wire-in a zener diode (it will need a shunt resistor)?

TNX,

Jan
ON3ZTT

Jan De Smet:
Done!
Re-wired the mic connector plug that was yaesu-wired to kenwood-wired, and incorporated a 7805 voltage regulator and a 100nF polyester cap along the mic wire to bring the 8V pin down to 5V, and nicely taped this in and on the cable.
In this way I did not have to modify the new MD-100 Mic inside and void the warranty.
It works OK and I did connect the Up and Down which in the MD-100 is operated through a sliding ring and this also works flawlessly.

The only thing I need to use it again with my FT-897 is an new yaesu wire mix cord.

TNX for all advices,

Jan
ON3ZTT

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