[minima] Re: Anything special about T3's capacitor to ground?
- From: Thomas Sarlandie <thomas@xxxxxxxxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Tue, 25 Feb 2014 23:59:44 -0800
Mark,
If you have a chance, I would be very interested in reading what is the
signal strength you measure here at the output of that transformer. I might
be looking at a problem that does not exist - maybe my sensitivity problem
is somewhere else.
Mvs Sarma: Thanks for the tips. I have tried smaller capacitance without
any success and I have looked hard for solder bridge. I might try building
a new mixer out of circuit to make sure I start from scratch.
73,
thomas
On Mon, Feb 24, 2014 at 9:25 AM, Thomas Sarlandie <thomas@xxxxxxxxxxxxx>wrote:
> Mark,
>
> I am getting confused too ;)
>
> The radio is in RX. I believe my audio amp works ( I can receive AM
> broadcast by putting my finger on the input wire ). I can also receive my
> 3kHz tone even with my capacitor in the circuit. My problem is I don't
> receive any other signals. It's like the receiver is completely deaf except
> to very strong signals applied to the input.
>
> When you say it's normal for the input of the audio amp to be weak, how
> weak are we talking? Micro-volts? Milli-volts? Should I be able to see
> something on the oscilloscope? Maybe the very high impedance output is
> normal.
>
> If it is, then my sensitivity problem might be somewhere else. How could I
> test that?
>
> Can you confirm that plugging an antenna on the receiver makes a
> difference in the level of noise you can listen to? Plugging an antenna on
> mine makes absolutely no difference to the noise strength.
>
> thanks again for your replies!
> thomas
>
>
> On Mon, Feb 24, 2014 at 1:41 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>
>> Hi Thomas
>>
>> I think I am getting confused (nothing new there). If the radio is in TX
>> then the point where your scope is connected is where we would inject audio
>> to mix with and modulate the BFO signal. If we are in RX (that's my
>> assumption) then we would only expect to see the injected signal being
>> modulated i.e. an audio signal and very weak one too - most of the gain in
>> the Minima is at audio. Is the audio amp working (does it buzz when you
>> stick your finger on the input)? I am not sure what you should expect to
>> see at that point? The audio tone there will also alter and be totally
>> dependent on the tuning of the LO and hence the output of the mix.
>>
>> If your scribbles are correct then the transformer looks correct to me.
>> Without checking the signals on mine I can't help much more until I get
>> home (Thursday)....
>>
>> Mark (just boarding in Abu Dhabi & bound for London)
>>
>>
>> On 24 February 2014 08:48, Mvs Sarma <mvssarma@xxxxxxxxx> wrote:
>>
>>> thomas,
>>> even a cheaperTA7358 and perhaps LKA1168 or so ( a compatible) would
>>> also work, I suppose
>>>
>>>
>>> On Mon, Feb 24, 2014 at 1:29 PM, Thomas Sarlandie
>>> <thomas@xxxxxxxxxxxxx>wrote:
>>>
>>>> Raj: Yes I have all the dots on the same side. I have checked several
>>>> times now. Unless I am really reading something backwards I think I have
>>>> that covered.
>>>>
>>>> Farhan: I don't but I will look into that. Would a ne602 work too?
>>>>
>>>> It's really raging to see my 4KhZ signal get out of the mixer but not
>>>> be able to tame it into the audio pre-amp because the output impedance is
>>>> so high. What could explain this? I will take any theory ;)
>>>>
>>>> 73,
>>>> thomas
>>>>
>>>>
>>>> On Sun, Feb 23, 2014 at 11:07 PM, <farhanbox@xxxxxxxxx> wrote:
>>>>
>>>>> Thomas, if you have an ade-1, just drop it into the circuit.
>>>>> - f
>>>>> Sent from BlackBerry® on Airtel
>>>>>
>>>>> -----Original Message-----
>>>>> From: Raj <vu2zap@xxxxxxxxx>
>>>>> Sender: minima-bounce@xxxxxxxxxxxxx
>>>>> Date: Mon, 24 Feb 2014 12:29:53
>>>>> To: <minima@xxxxxxxxxxxxx>
>>>>> Reply-To: minima@xxxxxxxxxxxxx
>>>>> Subject: [minima] Re: Anything special about T3's capacitor to
>>>>> ground?
>>>>>
>>>>> Thomas, please check all three DOTS are from the same end of the
>>>>> transformer.
>>>>> Most important that same winding start and end is correct.
>>>>>
>>>>> At 24-02-2014, you wrote:
>>>>> >Thanks Mark. That's how I have been doing it. I was not sure because
>>>>> T1 & T2 do not have those dots. Is it because phasing is not important on
>>>>> them?
>>>>> >
>>>>> >I have just rewound a new T3 using a new roll of #32 AWG wire on a
>>>>> new FT37-43. I get the exact same problem. So here is a picture of what I
>>>>> am doing with some labels as to where the wires go. I hope I am doing
>>>>> something very stupid and someone will be able to point it out:
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Regards
>>> Sarma
>>>
>>>
>>
>>
>
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