[Elecraft] Re: K3 Bias voltage

[Joe Subich, W4TV]

> So the bias voltage is nothing to do with where the 8v line is 
> on the front panel socket.  Unless your mic requires the 8v line 
> which would only normally happen for desk mics (?) I do not see 
> a problem.  The vast majority of desk mics will have a blocking 
> capacitor on the mic audio line.
> 
> Do I have it correct?

Not quite.  Kenwood, Yaesu and TenTec all require the +8V (+5V on 
pin 2 for Yaesu/Kenwood) line for electret mics.  They do not put 
bias on the microphone audio line in order to prevent problems and 
potential damage with dynamic mics.  Instead they install a R/C 
network inside any electret or preamplified microphone to add the 
voltage directly at the mic element or preamplifier.    

Dynamic mics typically do not include blocking capacitors in the 
mic line although some amateur mics will include a switch and .1 
to .33 uF capacitor to provide a rising frequency response.  

73, 

   ... Joe, W4TV 
 




> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ian J Maude
> Sent: Thursday, May 01, 2008 10:57 AM
> To: Elecraft Reflector
> Subject: [Elecraft] Re: K3 Bias voltage
> 
> 
> Hi all,
> I think we need to understand what is happening here.  I am 
> pretty sure 
> I have this correct.
> 
> The front panel socket is the same as the Kenwood one apart 
> from the 8v 
> being present on a different pin.  However, this is a bit of a 
> smokescreen as it actually has very little to do with bias 
> voltage.  The 
> bias voltage as I see it drops a voltage onto pin 1 which will be the 
> mic audio line.  This has been done for speaker mics and handies for 
> some time.  So the bias voltage is nothing to do with where 
> the 8v line 
> is on the front panel socket.  Unless your mic requires the 8v line 
> which would only normally happen for desk mics (?) I do not see a 
> problem.  The vast majority of desk mics will have a blocking 
> capacitor 
> on the mic audio line.
> 
> Do I have it correct?
> 
> 73 Ian
> 
> -- 
> 
> Ian J Maude, G0VGS
> SysOp GB7MBC DX Cluster
> Member RSGB, GQRP
> K2 #4044 |K3 #455
> 
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