I have a two amp fuse inline. How do you tell if it is oscillating?

And a really bad swr is what I am guessing killed the irf510's.
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

A series resistor also tends to act like a treble tone control. Low
frequencies with higher audio power levels tend to get attenuated more
by a higher voltage drop while lower power audio high frequencies don't
get attenuated as much.

YMMV as far as the actual effect on the ear.

tim ab0wr

On Thu, 15 Mar 2018 19:22:33 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Quiescent current into the TDA2822 is around 6ma, peaks can be 1 Amp.
Though?100ma might be sufficient for moderate speaker volumes.
You would need two resistors for a voltage divider, and maybe waste
500 ma through them to keep the voltage moderately well regulated.

Good spot for an LM7805.

On Thu, Mar 15, 2018 at 07:10 pm, Ashhar Farhan wrote:

One could use a voltage drop resistor. The higher the current draw,
lower would be the voltage to the TDA2822
?

Ryan,

One thing to remember is that crystal filters have always been
considered to be *upper* sideband filters primarily.

They don't have infinitely steep firewalls at each end of the bandpass.
Think of a crystal filter having a slope of 60deg on the low frequency
side and a 45deg slope on the upper frequency side. It's not that
bad but it illustrates the point.

The filter works best when the carrier is on the low frequency side of
the crystal and the audio is above the carrier. The high frequencies in
the voice are usually lower in power anyway so the increased slope on
the upper frequency side of the filter still provides adequate
attenuation.

If you switch and put the carrier on the upper frequency side of the
filter and the audio lower in frequency than the carrier then you are
using your filter where it works the worst. It's not so bad for
transmitting other then it doesn't suppress the carrier as well but for
receiving it tends to let low frequency noise *and* signal through more
than if you use it as an upper sideband filter.

This is also why receivers using such a method often sound so different
on lsb than on usb. Low frequencies in the voice are emphasized much
more when using the filter as a lsb filter than when used as an usb
filter.

The reason for this is that crystal filters are based on the resonant
frequencies of the crystals, the capacitances associated with the
holder, and the stray capacitances of the filter itself. Resonant
crystals can be seen as a combination of resistance, capacitance, and
inductance, just like any resonant circuit. As you go higher in
frequency the capacitance provides less impedance and the higher
frequencies are attenuated less [impedance = 1/(jwC)]. That and the
holder capacitances and stray capacitances provide lower impedance
paths around the filter as the frequency goes up. So you get less
attenuation on the high frequency side.


At the risk of boring everyone, using crystal filters as lsb filters
was done a *lot* in times past when it was difficult to provide two
vfo's of such high frequency that had any stability at all. It was far
easier and worked better to use one of the same crystals as in the
filter as your bfo. You could pull it with a parallel capacitance to
place it on one side of the filter or the other, and being based on a
crystal the bfo would be pretty stable. You just had to live with the
shape of the filter.

This is one of the less appreciated design choices Farhan has done. By
using such different frequencies in the second stage he has been able
to invert LSB signals into USB signals at the filter stage. Thus he
makes the best use of the crystal filter for both USB and LSB
received signals.

Rather than show a bunch of math just remember that when you subtract
the oscillator frequency from the signal you maintain orientation of
the sideband. When you subtract the signal from the oscillator you
invert the sideband.

In the ubitx the first mixer inverts a lsb received signal to usb and a
usb received signal to lsb by subtracting the signal from the vfo. The
second mixer then uses the lower frequency oscillator to maintain the
45mhz usb signal and the higher frequency oscillator to invert the
45mhz lsb signal back to usb. When you look at the block diagram for the
ubitx remember that when it says (33Mhz on USB/57Mhz on LSB) that he is
talking about the 45Mhz signal, not the received signal.

tim ab0wr

On Thu, 15 Mar 2018 00:13:32 -0700
"Ryan Flowers" <geocrasher@...> wrote:

See, this is why I posted. I know I'm in over my head. I don't fully
understand the crystal filter and where its passband is positioned.
You just gave me good information though, so thank you. And Tim, the
variables and equation used is

vfoOffset + frequency) VFO Offset of 11984800 + frequency displayed
(7mhz) and oh my, I just realized I'm doing it backwards which is one
reason I am having such a hard time. I do most of this late at night
and it shows lol. Thanks for causing me to re-evaluate that. This
would explain why I was getting FT8 only in what I thought was LSB
mode. I modified the code to subtract displayed frequency from
carrier, outputting 5mhz instead of 19, and adjusted the USB/LSB
frequencies based on what you said Jerry, and they were dead on.?

I fired up the rig and did some basic testing and the audio was very
clean. I hooked up the PC and had an FT8 QSO by answering nearly the
first CQ I saw. Success! Thanks so much for the help, guys.?

I still want to understand how the 5 crystals all being on the same
frequency works. I think the X5 crystal has a capacitor to pull the
frequency up to adjust the passband, and the 119984800 which I
mistakenly thought was my offset is not, but is rather the original
LSB frequency I was *using* as the offset on my QRP Labs VFO. Because
now I'm seeing that I'm a few khz low on the display, which I suppose
makes sense since my offset is equally low. I have some adjusting to
do.

Thanks again- you guys have saved me tons of frustration.

--
Ryan Flowers - W7RLF
MiscDotGeek.com ( )
Multi Band BITX40 ( )
The BITX40 FAQ ( )

Joe,

Since you put in a new chip and no audio.. could mean a short at the speaker jack or speaker.

If you turn up the volume does the current go up? does the chip get warm ?

Did you have any audio earlier before the smoke ?

Raj

>I got mine yesterday also,? ordered 2/17.
This is exciting news - I ordered mine on 2/19.

As for the 2822 chips, I've decided to put a regulator in their B+? line before ever powering them up.

Thanks!

Jerry:

I cite those only as examples. You are right -- the IRF510 was
chosen by WA2EBY both because it was the most workable
and one of the cheapest solutions. And now one can get good
devices made by Fairchild or Vishay.

There are others nowadays. One of the closest (besides the IRF512)
is probably the FQP9N08. It has a drain voltage of only 60V but a
Ciss of ~250 pF. Another one is the DPACK MTE300N2013S,
though I don't know about the cost of that one. The main disadvantages of
the smaller ones are lower drain voltage and lower power dissipation.
That must be accounted for...

There are many examples with Ciss in the range of 300 to 800 pF.
Even devices up to 3000 or 4000 pF. will work after a fashion.
These can be made to work with proper layout and some impedance
matching. Most are under $US1.00 each also. One can use another
power MOSFET if necessary, even the IRF520s or IRF530s,
though it is not recommended that they be used. Doug Demaw was
experimenting (and using) the MJE3055T, one of the earliest available
MOSFETS. It can be done. But they are rare now, alas.

john
AD5YE

Just FYI:

Center Frequency: 700 Hz
Bandwidth: 200 Hz
DC Power: 5VDC
GAIN: Upto 20dB via R11 and R12 + trimpot.

Resistors 1206 SMD:
R1 33k
R2 33k
R3 1M
R4 47k
R5 47k
R6 36k
R7 36k
R8 10k
R9 750k
R10 10
R11 100K
R12 100K

Capacitors 1206 SMD:
C1? 0.1u? 104
C2? 47n?? 473
C3? 36n?? 363 (33n + 3n3 mount on side together)
C4? 1n??? 102
C5? 39n?? 393 (33n + 5n8 mount on side together)
C6? 1n??? 102
C7? 2n2?? 222
C8? 2n2?? 222
C11 0.1u? 104
C14 220u? Electrolytic

Other:
IC TLC274
Relay OMRON G6S-2-DC5
200K/100k trimpot

R11 and R12 are optional to parallel the 200k trimpot to make it a logarithmic 100k.
Or just use a linear 100k pot.

Use a switch connected to 5V to turn on the filter.
This powers the opamp and switches the relay feeding the audio into the circuit.
When off the relay just passes the audio straight through unfiltered

73

Maybe, if they work ill put the extra ones up with my RadionoI2C boards....

Nice. ?Are you selling these boards?

Regards



Simon VK3ELH?

Im loving the cheap and easy EasyEDA/JLPCB boards and simple web designer.
This time its a CW filter similar to the QCX and HiPerMite. I take no credit for the design, just copied it and added a switching relay.
I ordered 10 boards at $10 posted. love it!



73, Nick VK4PLN.

Greetings,


? ? ?I finally got my uBitx assembled and in the case of it's final destination.. I checked my wiring on everything, and nervously applied power..? ?Display came up and I was happy.. turned the VFO for a sec and watched the frequency changed.. pushed in to change function.. all at once.. I smelled the magic smoke smell and the audio chip went pop...? I happened to look in my parts bins and I have happened to have a few more.. it appears from a different manufacture, and these are the "M" flavor.? I replaced the audio chip.. but I have no audio, via headphone or speaker.. I turned it off.. wanted to check with the group..?

73 de Joe KB5VJY k

These HEXFETS are rated for 200V and 50A. They will (sorta) work as you have shown.

But the gate input capacitance is 4000+ pF. That increases your standing wave in
the drive circuit and lowers your output considerably. You have 2 choices:
Either replace the finals with IRF510s (after you have figured out what blew them up),
or figure out how to lower the input capacitance to 180 pF. or so. You can also probably
safely use a drain voltage of 48v or so, but there would probably be oscillation which would
have to be accounted for. Incidentally, how do you know they are not oscillating now?
Since the potential drain amperage is so high, it is probably wise to provide a current limiter
if you have not already done so, especially using wspr or another more or less continuous
wave function.

It's better to replace the finals.

john
AD5YE

All I know is I wasn’t getting the correct voltages on Q90. It was 0 volts dc on all three pins. I was also losing the transmit dc in the vicinity of R84. So I replaced them both. Yeah, I know, kind of a shotgun approach but it brought it back.?

73,
Guy

Well, pushing the limits on the irf510 mosfets, they caved on me. So, digging through my junk I found four irfp260's and soldered them in as an effort to get back on the air. So far, it seems to work, but I noticed the current draw is much lower and a bit more heat is created, however, I have pretty get distance on wspr and about the same reports on ft8.

Does anyone know if there are any changes that should be made to the ubitx to get it to work better (with more output) using these mosfets? The obvious answer is to order some more irf510's from jameco and put them in, and quit limping the radio along on these other mosfets...but..ya know, spare parts bin and all.
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

--

Some of these clones seem to blow for no particular reason.
I think we primarily must limit the supply voltage, not so much the current under load.

Though they are really good at dealing with variations in supply voltage.
The series resistor in the 12v supply could be a solution for a good (non WX)?TDA2822
if you are worried about exceeding the max power dissipation spec at high volume
and low load impedance.

开云体育

The DPAK package is perfect.?