[minima] Re: SOLVED! Re: Re: Anything special about T3's capacitor to ground?
- From: <jerry@xxxxxxxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Thu, 27 Feb 2014 05:13:08 -0700
Happy you solved the problem. Do a post mortem on your troubleshooting
steps and see if there were any signs you missed earlier. Jerry
K5LRU
Harwood, Texas
> -------- Original Message --------
> Subject: [minima] Re: SOLVED! Re: Re: Anything special about T3's
> capacitor to ground?
> From: Thomas Sarlandie <thomas@xxxxxxxxxxxxx>
> Date: Thu, February 27, 2014 3:46 am
> To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
>
>
> Thanks. So yes I had C18 in parallel with R23 which was incorrect.
>
>
> On Thu, Feb 27, 2014 at 1:42 AM, Mvs Sarma <mvssarma@xxxxxxxxx> wrote:
>
> > sent on mail a pdf of adrian's sch where numbers are indicated.
> >
> >
> > On Thu, Feb 27, 2014 at 3:05 PM, Thomas Sarlandie
> > <thomas@xxxxxxxxxxxxx>wrote:
> >
> >> I do not have numbers for resistors and capacitors on my schema. What
> >> schema are you referring to?
> >>
> >> On Farhan's schema, I had the 100pf cap below q9 misplaced. It was
> >> connecting emitter and collecter instead of base and emitter.
> >>
> >>
> >> On Thu, Feb 27, 2014 at 1:32 AM, Mvs Sarma <mvssarma@xxxxxxxxx> wrote:
> >>
> >>> THOMAS,
> >>> WAS IT A CASE OF r23 AND c18 INTERCHANGE OR TRANSISTYOR PINS SWAPPED?
> >>> OTHERWISE NOT POSSIBLE TO MOUNT c18 WRONG WAY !!
> >>>
> >>>
> >>> On Thu, Feb 27, 2014 at 2:31 PM, Ik3nlk <mail@xxxxxxxxxx> wrote:
> >>>
> >>>> I am happy for you! I was following your Odissea since the beginning
> >>>> and it's a relief to read good news from you!
> >>>>
> >>>> Keep going whit this fine project!
> >>>>
> >>>> 73 Giorgio
> >>>>
> >>>> Inviato da iPhone
> >>>>
> >>>> Il giorno 27/feb/2014, alle ore 09:48, Thomas Sarlandie <
> >>>> thomas@xxxxxxxxxxxxx> ha scritto:
> >>>>
> >>>> Hello everyone!
> >>>>
> >>>> It was a little past midnight and there was plenty solder smoke in the
> >>>> shack when I finally heard my minima for the first time ...
> >>>>
> >>>> Special credit to Mark who sent the decisive last message which led to
> >>>> victory. Thanks to everyone who shared comment and tips. The
> >>>> international
> >>>> brotherhood of electronic wizards has once again lived to its reputation!
> >>>>
> >>>> After Mark last messages, I decided to build a new mixer on a separate
> >>>> board, starting from scratch. I used new diodes that I re-matched.
> >>>> Picked a
> >>>> new transformer and checked it's core AL value (thanks Mvs Sarma for
> >>>> suggesting this; it was ok). Used a drill to prepare the trifilar wires,
> >>>> carefully placed the three windings, etc - gave it lots of love.
> >>>> Then I used a little piece of coax to drive the bfo signal from my main
> >>>> board and used my DDS to provide an IF at 20 Mhz. With that complete new
> >>>> setup on a new board, I still had the same problem: with the capacitor to
> >>>> ground there was no signal out of the mixer.
> >>>>
> >>>> At this point the only thing that could be bad was the BFO so I rebuilt
> >>>> another BFO from scratch on my new board.
> >>>> With the new BFO, I finally got a working setup. The audio signal was
> >>>> there.
> >>>>
> >>>> I then looked very carefully at the BFO on my main board and found my
> >>>> problem in 30 seconds. The 100pF capacitor that is supposed to be between
> >>>> the base and the emitter was between the base and the collector. I moved
> >>>> it
> >>>> and it fixed my problem. (And then considered whipping myself with a
> >>>> coaxial cable ...)
> >>>>
> >>>> I have fixed a lot of software bugs but I think with this bug I have
> >>>> earned my first home-brewing scar ;)
> >>>>
> >>>> I would have found the problem earlier if I had suspected the BFO was
> >>>> the problem. I assumed it was ok because I was getting a decent signal
> >>>> out
> >>>> but I was wrong.
> >>>>
> >>>> Anyway, I am now listening to 20m and 40m. It's pretty much dead now
> >>>> but just plugging the antenna in the minima, I can hear a large
> >>>> difference
> >>>> in noise level. I have birdies, am stations and it finally sounds like a
> >>>> receiver. I am confident there will be qsos going on when I wake up
> >>>> tomorrow.
> >>>>
> >>>> I hope everyone will sleep better knowing that the excellent schematic
> >>>> of Mr Farhan was not the problem - I take full responsibility!
> >>>>
> >>>> Thanks again everyone. Each evening spent on this radio is a ton of new
> >>>> stuff learnt - next steps, the transmit stages.
> >>>>
> >>>> 73!
> >>>> thomas
> >>>>
> >>>>
> >>>> On Wed, Feb 26, 2014 at 7:23 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx>wrote:
> >>>>
> >>>>> Hi Gang
> >>>>>
> >>>>> I'm back home and have just wound a 8 turn trifilar transformer on an
> >>>>> FT37-43 and coupled it up to the output of a 20MHz crystal oscillator I
> >>>>> had
> >>>>> lying about.
> >>>>>
> >>>>> Here's the setup:
> >>>>>
> >>>>> <DSCN0332-Optimized.JPG>
> >>>>>
> >>>>>
> >>>>> This is the signal into the BFO port (yuck - but 20MHz):
> >>>>>
> >>>>> <BFO Signal.png>
> >>>>>
> >>>>>
> >>>>> My analogue signal generator (
> >>>>> http://g0mgx.blogspot.co.uk/2013/10/so-hows-sig-gen.html) is
> >>>>> connected to the RF port:
> >>>>>
> >>>>> <RF Port.png>
> >>>>>
> >>>>>
> >>>>> Then I see kind of crap out of the audio port but if I alter the fine
> >>>>> tune on the sig gen I can see what looks like an audio signal:
> >>>>>
> >>>>> <Audio Port.png>
> >>>>>
> >>>>>
> >>>>> There is a load of RF in this signal also, this is 0 to 150MHz:
> >>>>>
> >>>>> <efgjhbaa.png>
> >>>>>
> >>>>>
> >>>>> and if I zoom in on the 20MHz, we can see the mix of the two RF
> >>>>> signals, this is 50KHz either side of the 1st peak above at 20MHz - the
> >>>>> signal closest to the centre and the largest amplitude is the BFO:
> >>>>>
> >>>>> <Audio Port SA2.png>
> >>>>>
> >>>>>
> >>>>> 6.56 of EMRFD is probably the best reference to understand whats in
> >>>>> these signals.
> >>>>>
> >>>>> Mark
> >>>>> G0MGX
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 26/02/2014 12:19, Mvs Sarma wrote:
> >>>>>
> >>>>> Thomas,
> >>>>> please see whether the core qualifies for the AL value specified for
> >>>>> FT37-43. Wind 10Turns and measure inductance. it would be AL /10. as per
> >>>>> www.kitsandparts.com datasheet is 350 with 20% Tol
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Wed, Feb 26, 2014 at 1:29 PM, Thomas Sarlandie <
> >>>>> thomas@xxxxxxxxxxxxx> wrote:
> >>>>>
> >>>>>> 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
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>> Regards
> >>>>> Sarma
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>
> >>>
> >>> --
> >>> Regards
> >>> Sarma
> >>>
> >>>
> >>
> >>
> >
> >
> > --
> > Regards
> > Sarma
> >
> >
Other related posts:
