[TenTec] Tentec 700 Hand Mic Question

[Bwana Bob]

Dave:

Well, the only other thing that  can suggest is an RC circuit on the 
power input to the mic to slow down the rise time.


                 73,

                 Bob WB2VUF

On 12/18/2010 2:28 PM, K8JDC wrote:
> Bob,
>
>       Yes I did wire the voltage hot all the time as a test.  The power
> is definitely going thru the PTT switch but the mic is hot all the time
> if I  bypass the PTT switch.  In other words, if I use my footswitch to
> key the back-panel mic input (for digital modes or whatever), then the
> 700 audio is also live if it is connected to the front of the radio.
> Now, I can obviously unplug the 700 but I was hoping to find a fix
> because I want to be able to use the front and back panel mic inputs
> interactively.  I can do this with my 701 hand mic without the spike but
> was hoping to fix the 700 so it was also usable.
>
> Whatever transient is going on is not caused by activating the PTT
> anyway because I tried connecting the mic with the PTT switch already
> activated and it still causes the spike.  Seems like it is the
> application of voltage to the circuit and the PTT switch.
>
> Dave
>
>
>
> On 12/18/2010 12:26 PM, Bwana Bob wrote:
>> Dave:
>>
>> Did you try rewiring the mic element so that it is powered all the
>> time? Maybe the mic power is going through the PTT switch and the
>> turn-on transient is putting out an audio pulse.
>>
>>                  73,
>>
>>                  Bob WB2VUF
>>
>> On 12/18/2010 10:50 AM, K8JDC wrote:
>>> Friends,
>>>
>>>        I recently got a Tentec 700 hand mic and noticed that it causes
>>> the
>>> radio to transmit a spike every time the PTT lever is pushed.  The mic
>>> was set up to use a 9V battery when I got it but I have wired it to
>>> operate directly off my Paragon II.  It spikes on either power source
>>> and the spike is basically full output power so it's a bit alarming.
>>>
>>>        I originally thought the spike was related to the operation of the
>>> PTT switch...i.e. a little clicking noise causing the spike but that's
>>> not true.  If I key the PTT with the mic disconnected from the radio and
>>> then connect the mic to the radio, the spike still happens so it appears
>>> that it is related to applying the voltage to the mic circuit or
>>> cartridge.  I played around a bit trying to add a capacitor to stabilize
>>> the power in the circuit and eliminate any transients but the spike is
>>> still there.
>>>
>>> Has anybody seen this and/or have a fix?  The existing caps in the
>>> circuit appear to be okay (i.e not shorted) and I think the cartridge
>>> itself is the cause of the spike.  There is a resistor feeding power to
>>> the cartridge but I have not tried raising the value (yet).
>>>
>>> Thanks...
>>>
>>> Dave
>>> K8JDC
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