Hmm, my analysis in post /g/BITX20/topic/6215251might be full of beans. The SiLabs document an619 shows that registers 16,17,18 can set drive levels at clk0,clk1,clk2 to values of 2,4,6 or 8 ma. With 8ma max into 50 ohms that's a 0.008*50 = 0.4v pk-pk square wave across the 50 ohm load. Farhan's ubitx has a 6db pad between the raduino and T1, so the primary of T1 sees 0.4v/2 = 0.2v. T1 has two windings driving the diodes, a step-up transformer, so the diodes see a 0.4v pk-to-pk. But a single schottky diode has a forward voltage of around 0.4v at 10ma, I have no idea how this 0.4v signal source can drive two schottky diodes in series. ? But the ubitx apparently works. What am I missing here? I'll have to put a 50 ohm load on a si5351 someday, see just how much drive the si5351 can give. Might be best to include a buffer amp, if only to reduce all the crosstalk you would get between si5351 channels when asking it to deliver maximum drive.
On Mon, Oct 23, 2017 at 02:54 am, Gordon Gibby wrote:
think you're off a decimal point there.... 2 mA into 50 ohms is 1/5 of a milliwatt so it wold not be 3dBm....?
From:?Kelly Jack <kellyjack1968@... ? ?Sent: Monday, October 23, 2017 5:30 AM?
this page indicates that setting the drive at 2ma equates to 3dbm into a 50ohms load.
|
And what would happen using Si5351 with analog switcher mixer (Tayloe detector). The square wave only close and open the switch.- LU5DNM -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Pavel Milanes Costa Enviado el: lunes, 23 de octubre de 2017 07:13 p.m. Para: [email protected]Asunto: Re: [BITX20] Raduino question. El 23/10/17 a las 16:53, Jerry Gaffke via Groups.Io escribi¨®: The ARRL Handbook says square waves are better,
though does not say anything about how huge the difference is. We are talking the same language, we are agree on the point that square is better, but not always... I'm just making a little note to the side of the page about a special case as per my experience... Grab your digital copy of the ARRL handbook and keep looking at chapter 10... search for figure 10.22 on page 10.21 just in the next page of your note. Look at the graphic at the bottom of figure 10.22 compare the output from using a sine wave vs square wave, square wave has ALL the harmonics (solid line), the sine one has none (dashed line) Also the output from a sine VFO is 3dB lower than the square one. ;-) I was only saying that if you use the Si5351 as BFO to mix with the IF and grab the audio, and you use a low freq on it (below ~2 Mhz as per my experience, worst on the 500 Khz range) you may get a very noisy audio as those solid lines (harmonics) are very close each other and will mix again and again inside the mixer/amplifiers and you will get a very noisy reception, full of carriers here and there... On tx there is no problem as the SSB filter wipe them away... In deed if you use a high enough IF (as the bitx40 do, in 12 Mhz) all the unwanted mixing are cleaned by simple filtering, but beware if you use a low freq as 455Khz or 500 Khz... those unwanted mixing products will haunt you... Been there, done that, must filter it if you use a Si5351 for BFO below ~2Mhz. -- 73 CO7WT, Pavel.
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Re: FS:W8TEE TFT boards and parts
Sold Thanks all for the interest
?73
?? David
???? N8DAH
|
tombstone? Yep. Vince.
On Oct 23, 2017 10:00 PM, "Vince Vielhaber" <vev@...> wrote:
You might want to tombstone it to make sure that is what's smoking.
Vince.
On 10/23/2017 10:32 PM, Barrett O wrote:
Looks like it. Nothing eles but the diode I installed in that spot
On Oct 23, 2017 9:18 PM, "Vince Vielhaber" <vev@...
<mailto:vev@...>> wrote:
C130 is a 0.1uf. It's smoking? Are you sure that's what's smoking
and not something near it?
Vince.
On 10/23/2017 10:00 PM, Barrett O wrote:
Well I got around to install a diode still no luck. I had some
1N914
which are supposed to be electrically the same. I ended up
accidentally
ripping one of the traces off that seems to lead to the relay.
I
drilled
and installed diode. I installed annode to ptt1-2 (brown side).
connected cathode side to c130. rarduino comes on. barely any
noise came
out of speaker even with antenna connected. then noticed c130
was
smoking and melting into board. Does anybody know what
capacitor
I can
switch that with?
Ps. If it sounds like I don't know what I'm doing it's because
I
don't
but trying to look at the diagram and find the nearest point
that
it
connects to solder to with the same polarity.
Barrett
KG5SSO
--
Michigan VHF Corp.
--
Michigan VHF Corp.
-- Michigan VHF Corp.
|
A junction transistor like the mmbt3904 (the bitx40 schematic is incorrect in labeling them bc849)
is at first glance symmetrical, running it upside down with emitter and collector reversed could sort of work.
But they are optimized for the emitter going to ground, not the collector.
Page 2 of the datasheet shows that the base-emitter breakdown voltage is only 6 volts,
? ??
so if the emitter (now pseudo-collector) is at 12v and the base is below 6v that junction will break down
like a zener and current will flow. ?Pushing that junction into breakdown can have a permanent effect on gain
if current is restricted, and blow the transistor if it isn't. ?Not something they bother to spec though.
Assuming the mmbt3904 operating upside down is acting more or less like a normal NPN transistor,
with power to the bitx40 reversed the base of Q7 is biased at ? 12v*2.2k/(1k+2.2k) = 8.25v through 1k || 2.2k = 667 ohms
and the reversed transistor is in saturation. ?The 470 ohms at R74 is the only thing restricting collector/emitter current flow
to around 12v/0.47k=25ma, and Q7 is dissipating 25ma*12v=300mw. ?Would probably survive that, but not by much.
Unfortunately, with the pseudo-emitter down near ground, the base will be too despite the best efforts of
the biasing resistors at R71 and R72. ?So the pseudo-collector to base voltage will exceed
the 6v emitter-base breakdown voltage of the datasheet, and all bets are off. ??
I'm not planning to test my guesses of what might happen on my bitx40 anytime soon.
Mine has an LM2940CT-12 regulator in the supply line from the battery.
Unlike the older LM7812, the LM2940CT-12 ?will protect against reversed battery leads.
It also protects against battery voltages in excess of 12v, and gives some semblance of overcurrent protection.
The IRF510 is powered directly from the battery with no protection, ?as the IRF510 is quite cheap.
Maybe I'll add a 2A fuse there someday. ?After watching T7, L8, and associated traces fry.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 08:20 pm, Jerry Gaffke wrote:
Q7 has mostly that 470 ohm emitter resistor to stop excessive reverse current, but probably survived.
I'm not really sure how Q7 (or any of the other transistor amps) would behave in the face of a reverse supply.
|
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On Tue, Oct 24, 2017 at 07:06 am, tArthur Bryant wrote:
I heard you are working on an updated uBITX circuit, is this true? When will the drawings be available?
|
Ashhar,
I heard you are working on an updated uBITX circuit, is this true? When will the drawings be available?
Art
KB8HGW
|
Re: BITX QSO Night - Need Alternate Frequencies
I agree that there is too much QRM ?with the BC station close by as I commented a few weeks ago. Before picking a new one like 7282, why don't we check for a few weeks to make sure we don't run into the same problem again. Would a freq above 7.175 and below 7.200 be better to avoid broadcast traffic?
73 Everyone
WI1B
Ken
|
If you reversed the power leads into the main bitx40 board, I suspect surprisingly little would blow.
D7 and C130 are meant to be a snubber across the coil of K1, but got wired up wrong.
They are not across the coil (pins 7 and 8 of the relay) but instead are from +12v to ground.
They should have been wired up like D8 and C164 at K2, directly across the relay coil.
Since D7 and C130 ?aren't wired up right, they aren't serving any purpose and can be removed from the board.
U2 is probably blown, as the LM78L09 is not built to deal with a negative voltage at the input.
But damage probably stopped there, as Q8 and Q9 have no path from +12 to gnd of less than 1kohm.
Check for 9v at U2 pin 1, if you don't see 9v then replace U2.
Or if you are brave, just wire across U2 from pin 3 to pin 1 and cut pin 2 loose from ground,
you don't really need a regulator there if not using the analog vfo.?
Q7 has mostly that 470 ohm emitter resistor to stop excessive reverse current, but probably survived.
I'm not really sure how Q7 (or any of the other transistor amps) would behave in the face of a reverse supply.
U1 and Q16 have a handy reverse power protection diode at D18, so should have no trouble.
Likewise with the three BiDi RF amps, they all have a diode in series with the 12v supply.
There is no path around Q12 that sees less than 1kohm, and 12ma shouldn't fry anything there.
Likewise with Q10 and Q11.
If you did not press the PTT button, then the stuff around Q13, Q14 and U3 never saw power,
and should be fine. ?
If you wired up PA-PWR1 with a reversed 12v supply and powered that up, it could have blown the IRF510
as it has a reverse diode from drain to source. ?But more likely the coil at L8 or T7 would burn first.
If you did not wire up PA-PWR1 in reverse, then that stuff should all be fine.
The Raduino on the other hand is probably toast if it saw reversed supplies. ?
Maybe you do want to get U2 working again, supplying 9v to the analog vfo
so you can install a coil at L4 and play with the rig till a new Raduino arrives.
That's just a quick survey, I probably got some stuff wrong.
Could well be something more than U2 that blew on the main board.
And perhaps somebody can figure out how to bring your Raduino back from the dead.
May not be trivial to figure all of this out without a scope and some idea of what's going on.
At worst, consider this a nice cheap $59 lesson in what not to do, ?and go order another unit from hfsigs.
?
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 07:00 pm, Barrett O wrote:
Well I got around to install a diode still no luck. I had some 1N914 which are supposed to be electrically the same. I ended up accidentally ripping one of the traces off that seems to lead to the relay. I drilled and installed diode. I installed annode to ptt1-2 (brown side). connected cathode side to c130. rarduino comes on. barely any noise came out of speaker even with antenna connected. then noticed c130 was smoking and melting into board. Does anybody know what capacitor I can switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I don't but trying to look at the diagram and find the nearest point that it connects to solder to with the same polarity.
|
My gut instinct is that that diode is installed incorrectly
somehow.? Double check to make sure you are not shorting the power
supply with the diode.? I would also highly recommend you add a 1
amp fuse to your power input while you are sorting this out.
On 10/23/2017 10:32 PM, Barrett O wrote:
toggle quoted message
Show quoted text
Looks like it. Nothing eles but the diode I
installed in that spot
|
toggle quoted message
Show quoted text
On Oct 23, 2017 10:00 PM, "Vince Vielhaber" < vev@...> wrote: You might want to tombstone it to make sure that is what's smoking.
Vince.
On 10/23/2017 10:32 PM, Barrett O wrote:
Looks like it. Nothing eles but the diode I installed in that spot
On Oct 23, 2017 9:18 PM, "Vince Vielhaber" <vev@...
<mailto:vev@...>> wrote:
? ? C130 is a 0.1uf.? It's smoking?? Are you sure that's what's smoking
? ? and not something near it?
? ? Vince.
? ? On 10/23/2017 10:00 PM, Barrett O wrote:
? ? ? ? Well I got around to install a diode still no luck. I had some 1N914
? ? ? ? which are supposed to be electrically the same. I ended up
? ? ? ? accidentally
? ? ? ? ripping one of the traces off that seems to lead to the relay. I
? ? ? ? drilled
? ? ? ? and installed diode. I installed annode to ptt1-2 (brown side).
? ? ? ? connected cathode side to c130. rarduino comes on. barely any
? ? ? ? noise came
? ? ? ? out of speaker even with antenna connected. then noticed c130 was
? ? ? ? smoking and melting into board. Does anybody know what capacitor
? ? ? ? I can
? ? ? ? switch that with?
? ? ? ? Ps. If it sounds like I don't know what I'm doing it's because I
? ? ? ? don't
? ? ? ? but trying to look at the diagram and find the nearest point that it
? ? ? ? connects to solder to with the same polarity.
? ? ? ? Barrett
? ? ? ? KG5SSO
? ? --
? ? ? Michigan VHF Corp.? ?? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
--
? Michigan VHF Corp.? ?? ?
? ? ? ? ? ? ? ? ? ? ? ? ?
|
You might want to tombstone it to make sure that is what's smoking.
Vince.
toggle quoted message
Show quoted text
On 10/23/2017 10:32 PM, Barrett O wrote: Looks like it. Nothing eles but the diode I installed in that spot
On Oct 23, 2017 9:18 PM, "Vince Vielhaber" <vev@...
<mailto:vev@...>> wrote:
C130 is a 0.1uf. It's smoking? Are you sure that's what's smoking
and not something near it?
Vince.
On 10/23/2017 10:00 PM, Barrett O wrote:
Well I got around to install a diode still no luck. I had some 1N914
which are supposed to be electrically the same. I ended up
accidentally
ripping one of the traces off that seems to lead to the relay. I
drilled
and installed diode. I installed annode to ptt1-2 (brown side).
connected cathode side to c130. rarduino comes on. barely any
noise came
out of speaker even with antenna connected. then noticed c130 was
smoking and melting into board. Does anybody know what capacitor
I can
switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I
don't
but trying to look at the diagram and find the nearest point that it
connects to solder to with the same polarity.
Barrett
KG5SSO
--
Michigan VHF Corp.
--
Michigan VHF Corp.
|
Looks like it. Nothing eles but the diode I installed in that spot
On Oct 23, 2017 9:18 PM, "Vince Vielhaber" < vev@...> wrote:
C130 is a 0.1uf.? It's smoking?? Are you sure that's what's smoking and not something near it?
Vince.
On 10/23/2017 10:00 PM, Barrett O wrote:
Well I got around to install a diode still no luck. I had some 1N914
which are supposed to be electrically the same. I ended up accidentally
ripping one of the traces off that seems to lead to the relay. I drilled
and installed diode. I installed annode to ptt1-2 (brown side).
connected cathode side to c130. rarduino comes on. barely any noise came
out of speaker even with antenna connected. then noticed c130 was
smoking and melting into board. Does anybody know what capacitor I can
switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I don't
but trying to look at the diagram and find the nearest point that it
connects to solder to with the same polarity.
Barrett
KG5SSO
--
? Michigan VHF Corp.? ?? ?
? ? ? ? ? ? ? ? ? ? ? ? ?
|
C130 is a 0.1uf. It's smoking? Are you sure that's what's smoking and not something near it?
Vince.
toggle quoted message
Show quoted text
On 10/23/2017 10:00 PM, Barrett O wrote: Well I got around to install a diode still no luck. I had some 1N914
which are supposed to be electrically the same. I ended up accidentally
ripping one of the traces off that seems to lead to the relay. I drilled
and installed diode. I installed annode to ptt1-2 (brown side).
connected cathode side to c130. rarduino comes on. barely any noise came
out of speaker even with antenna connected. then noticed c130 was
smoking and melting into board. Does anybody know what capacitor I can
switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I don't
but trying to look at the diagram and find the nearest point that it
connects to solder to with the same polarity.
Barrett
KG5SSO
--
Michigan VHF Corp.
|
Well I got around to install a diode still no luck. I had some 1N914 which are supposed to be electrically the same. I ended up accidentally ripping one of the traces off that seems to lead to the relay. I drilled and installed diode. I installed annode to ptt1-2 (brown side). connected cathode side to c130. rarduino comes on. barely any noise came out of speaker even with antenna connected. then noticed c130 was smoking and melting into board. Does anybody know what capacitor I can switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I don't but trying to look at the diagram and find the nearest point that it connects to solder to with the same polarity.
Barrett
KG5SSO
|
I believe that phase noise from the si5351 will scale up proportional to the output frequency.
So while phase noise from a 5mhz vco could be fine, it might become more of an issue
with the 45mhz IF of the ubitx. ?Receiving a 30mhz signal would put the vfo at 45+30=75mhz.
So phase noise on 10m with the ubitx that's 15 times worse than the Bitx40 on 40m.
However, several ubitx have been built, and apparently work well.
Jerry
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 04:29 pm, Jerry Gaffke wrote:
Trouble with a 455khz IF makes sense.?
There is a reason Farhan went to a 45mhz IF on the ubitx.
?.....
Phase noise may matter at some point, perhaps with narrow band digital modes like JT65?
|
Re: FS:W8TEE TFT boards and parts
Hi David
I am interested, let me know your Paypal ID and I will pay for it. Thanks.
Sebastian K4BAC
From: N8DAH <Dherron@...>
To: [email protected]
Sent: Monday, October 23, 2017 4:57 PM
Subject: [BITX20] FS:W8TEE TFT boards and parts
I wanted to get this project off the desk as I don't have time to work on it and no cash to get a 2nd bitx for it.
I have 2 x W8TEE boards for the tft display 2x regulators one AD9850 2x encoders 5 x AO3's one mega2560 pro mini (purchased from the same place Jack has gotten his in the past)
?
I am looking to sell the lot 35$ shipped to your door.
?
?Any questions please e-mail me direct
d herron at live dot com
?
73
?? David
????? N8DAH 
|
Trouble with a 455khz IF makes sense.?
There is a reason Farhan went to a 45mhz IF on the ubitx.
Plenty of weird things going on around mixers,?
many of which I am sure will surprise me if I ever get beyond armchair pontificating
and try getting designs of my own working.
I really don't have the tools to look for phase noise or minor mixer products.
But did order an sdrplay after hearing Pavel recommend it a few weeks ago for
inspecting crystal filter shapes. ?Is there software appropriate for measuring phase noise
using the sdrplay? ?Does the sdrplay have a local oscillator with significantlly
less phase noise than?the si5351? ?Also hope to use it as a spectrum analyzer,
hooking it up to a Rasberry Pi 3..
Phase noise may matter at some point, perhaps with narrow band digital modes like JT65?
I assume phase noise would present itself as more random noise when tuning in a weak signal,
though there are other possible causes for that symptom. ?
Many say the bitx40 sounds good, even compared to commercial gear that costs 10 or 20
times as much. ?And the Raduino has always had si5351 code that used a fractional output divider,
first with the Etherkit library and now with the si5351bx routines.
toggle quoted message
Show quoted text
On Mon, Oct 23, 2017 at 03:12 pm, Pavel Milanes Costa wrote:
In deed if you use a high enough IF (as the bitx40 do, in 12 Mhz) all the unwanted mixing are cleaned by simple filtering, but beware if you use a low freq as 455Khz or 500 Khz... those unwanted mixing products will haunt you...
|
Re: FS:W8TEE TFT boards and parts
The parts are currently awaiting payment if he falls through I will update the post?
|
Re: BITX QSO Night, Sunday, October 22, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
Confirming a good contact with Randy WB5YYM. Thanks for Arkansas! As is generally the case, W1LY was too close in for me to hear.
Lots of other good contacts made while listening, including DX. I worked YU1XA (Serbia) with my 5 watts. He¡¯s a fixture kilowatt station on 40m.
73s All,
Bruce KC1FSZ
|
N8DAH
Arthur Bryant
