[minima] Re: Minima Audio Sections Schematic
- From: Arv Evans <arvid.evans@xxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Wed, 29 Jan 2014 20:06:45 -0700
Farhan
Time constraints have kept me from finishing inclusion of the relay circuit.
That will get done quite soon though.
Most benefit from these drawings is having part numbers. This helps people
discuss the circuit by referencing individual part numbers.
Page size limitations forced me to split the Minima drawing into
sub-sections.
Guess I could scale down the parts but then they would be difficult to
read.
I chose to make a page for each major sub-section of the rig. We obviously
still need your all-in-one drawing so people can get the big picture for
how
it all connects and operates.
More drawings soon.
Arv
_._
On Wed, Jan 29, 2014 at 7:48 PM, Ashhar Farhan <farhanbox@xxxxxxxxx> wrote:
> Arv,
>
> the circuits look so much better when you draw them!
> The relay that switches the audio amp between the sidetone and the audio
> preamp is missing. it is an important part of the design.
>
> the audio preamp is always on. so is the audio amp. during transmission,
> the audio preamp has to disconnect from the audio amp and the sidetone has
> to connect. this is why the relay is needed.
>
> this turns out to be the easiest way to mute the receiver, enable the
> sidetone.
>
> it also sorts out some other issues:
> 1. the capacitors in the audio preamp take a few seconds to charge up. it
> is not an option to mute by powering down the audio-pre amp. hence, the
> need to have a relay to disconnect the audio preamp from the audio amp.
> 2. the sidetone oscillator has two outputs. one goes to the modulator
> which is also connected to the audio pre-amp input. the other goes to the
> audio amplifier (for actual sidetone). if the relay was not there, then the
> sidetone generator would be connected to both sides of the audio pre-amp
> and the pre-amp in turn connected to the audio power amp!
>
> the relay is a nice hack to circumvent these problems.
>
> - f
>
>
> On Thu, Jan 30, 2014 at 2:27 AM, Arv Evans <arvid.evans@xxxxxxxxx> wrote:
>
>> Sandeep
>>
>> Thanks for catching my omission of the two emitter resistors. The drawing
>> has now been corrected by adding two 22 ohm resistors. My build does not
>> include those, but for sake of correctness they do need to be in the
>> drawing.
>>
>> Also fixed C18 by changing it from 1 mfd to 50 mfd.
>>
>> I went back to Farhan's drawing and do not see the 0.01 capacitors that
>> you
>> mentioned. Is this your own addition, or something that Farhan has not
>> yet
>> documented?
>>
>> <http://www.phonestack.com/farhan/minima.html>
>>
>> I do see that he has made changes to the audio section to incorporate a CW
>> oscillator and relay switching for sidetone and +T / +R leads. As time
>> allows
>> I will make those changes to my drawing, and to my own build.
>>
>> The AF output jack arrangement was not shown on my drawing because that
>> is something that each builder should be able to arrange to fit his or
>> her
>> personal preference. Same idea with the microphone input and related PTT
>> lead.
>> [image: Inline image 1]
>> Thanks for checking my work for errors. I will update the G-Drive copies
>> in
>> the next few minutes. Corrected drawings are attached to this message.
>>
>> Arv K7HKL
>> _._
>>
>>
>>
>> On Wed, Jan 29, 2014 at 1:14 PM, Sandeep Lohia
>> <sandeeplohia12@xxxxxxxxx>wrote:
>>
>>> Transistor 368 is also available with motorolla (with & without QRP
>>> heatsink)
>>>
>>> looks same size 2N3906
>>>
>>>
>>
>
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