Hi Brent,
I use #43/61-2403 cores and winding with a small tween wire. I can put 5 windings of 5 turns for one xfrm in my H-Modo Mixer. What I do I use a needle to squize turns into the holes, to make "easier" to insert the last turns.
73
Gian I7SWX
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Thanks John
That's what I figured. I tried it with the number 30, and the amp works, but output is low. I'll try to make a different core. The instructions specify 5 bifilar turns on the primary, and 10 on the secondary, so I guess that works out to a 2:1 ratio with the center tap.
Brent
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BitX20 featured in Nuts and Volts
Just got my e-copy of Nuts and Volts for November 2017. Page 36-40 has the Bitx20 project.
Sent by me
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Re: is there a document that shows proper DC and AC voltages on the latest BitX40 Board from India?
Thanks!! Warmly yours,
Werner Vavken
Sent from my iPhone
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On Oct 25, 2017, at 5:50 PM, Jerry Gaffke via Groups.Io < jgaffke@...> wrote: Here's some DC readings: /g/BITX20/files/K7AGEAnd some AC: /g/BITX20/message/22764A few random hints: /g/BITX20/message/24225Might be something more here, not sure: /g/BITX20/message/23640Maybe here: /g/BITX20/topic/5181681And an LTSpice simulation of Q13,14,15 here: /g/BITX20/files/ke7erTypically, it's in one of the many torroids. between Q13 and the antenna. ?Perhaps a broken wire, or shorted wires, or enamel left on the wire where it was soldered to the board, or a cold solder joint. Or something embarrassing, like a poor connection between board and antenna BNC. You can often find those problems with an ohmmeter. Stuff behind Q13 except the transmit side of the bidi amps is common to both transmit and receive, so less likely to be the problem. ?But a 10 db loss in a mixer, for example, would mean very little transmit power out, but not even noticed on the receiver. Good luck! Jerry, KE7ER On Wed, Oct 25, 2017 at 08:52 am, WERNER G VAVKEN wrote:
s there a document that shows the proper DC and AC/RF voltages at various places on the latest BitX40 Board from India?
?
My receiver is working, I¡¯m now trouble shooting the transmitter.?
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Brent:
Probably not.
A viable alternative to the small "pignose" core
is a slightly larger one two of the same size mounted
back to back, or using four FT37-43
or FT37-61 cores cemented as two pairs of
two each side by side, and made to look sort of
like a "pignose. If necessary, go to a FT50-43 or
61 toroid core. It is not too critical; what makes a difference is
the number of turns and the ratio of turns in the
output transformer. You are trying to match the AB
transistor section to 50 ohms for the antenna. Usually
that is a ratio of about 4:1...but it may not be. There is
a lot of information on the JBOT out there. Look it up for other
alternatives. All of them will work pretty well. You may also
have to add a small capacitor across the primary winding
of the output transformer to squelch oscillation. (It happens!)
I don't know what Sunil is using, but most likely it
is a type #61 core (since these are everywhere now
as they are the common core of the 300/75 ohm transformers
for TV antenna lines). The original source is on Farhan's home
page. Look it up; it is very interesting.
john
AD5YE
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I realize this isn't part of the bitx, but it was developed in the same spirit as the bitx project, so forgive me if I ask a few questions. Firstly, if anyone has built this, can you give me any advice on the output transformer. I purchased Sunil's kit, and am having difficulty fitting the #26 wire on the binocular cores for the output transformer. I have some #30. Will using this much smaller wire degrade performance very much?
Thanks
Brent
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Re: is there a document that shows proper DC and AC voltages on the latest BitX40 Board from India?
Here's some DC readings: /g/BITX20/files/K7AGE And some AC: /g/BITX20/message/22764A few random hints: /g/BITX20/message/24225Might be something more here, not sure: /g/BITX20/message/23640Maybe here: /g/BITX20/topic/5181681And an LTSpice simulation of Q13,14,15 here: /g/BITX20/files/ke7erTypically, it's in one of the many torroids. between Q13 and the antenna. ?Perhaps a broken wire, or shorted wires, or enamel left on the wire where it was soldered to the board, or a cold solder joint. Or something embarrassing, like a poor connection between board and antenna BNC. You can often find those problems with an ohmmeter. Stuff behind Q13 except the transmit side of the bidi amps is common to both transmit and receive, so less likely to be the problem. ?But a 10 db loss in a mixer, for example, would mean very little transmit power out, but not even noticed on the receiver. Good luck! Jerry, KE7ER
On Wed, Oct 25, 2017 at 08:52 am, WERNER G VAVKEN wrote:
s there a document that shows the proper DC and AC/RF voltages at various places on the latest BitX40 Board from India?
?
My receiver is working, I¡¯m now trouble shooting the transmitter.?
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well I removed d7 and c130 and it doesn't smoke anymore but still not working. I hooked up the antenna. makes weird noise from speaker with no static but what I did notice is if I tune around in different spots it sounds like I can hear jumbled voices.
I will probably end up ordering another board and tackle this again later on when I feel more advance or there is a guy at the local ham club that has a lot of experience with electronics. Maybe I will ask him if he wants to look at it with me
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Re: Help with troubleshooting Bitx40 - no transmit.
#bitx40help
Yes, the mic is a Baofeng style handset.? It seems to me that I ended up switching two of the leads from the Miklor diagram to get mine to work as well.? Unfortunately, I do not remember what exactly was switched.? I do know that the speaker works though.
I have tested the PTT function using the PTT switch supplied by HFSigs.? I guess if the mic is not wired correctly, I wouldn't get a response from the switch alone.? I should try the supplied mic as well.
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is there a document that shows proper DC and AC voltages on the latest BitX40 Board from India?
Is there a document that shows the proper DC and AC/RF voltages at various places on the latest BitX40 Board from India?
My receiver is working, I¡¯m now trouble shooting the transmitter.? Thanks?
Werner Vavken, WB6RAW
Sent from my iPhone
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On Oct 25, 2017, at 8:27 AM, Jerry Gaffke via Groups.Io < jgaffke@...> wrote: His -10dbm vfo is going into the rf port of one of the mixers, as shown in the block diagram near the top of that webpage. On Wed, Oct 25, 2017 at 07:50 am, Jerry Gaffke wrote:
I have no idea where his -10 dbm vfo is going.
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Re: Help with troubleshooting Bitx40 - no transmit.
#bitx40help
Is the "BTech" mic you are using a Baofeng style mic? ?I had issues wiring mine according to the Miklor diagrams. ?I had to rewire it to get it to work.
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You guys are so far beyond me with your knowledge and terminology that I had to go read something like this prep article to be able to understand what you are discussing:
"Understanding Mixers ¨C Terms Defined, and Measuring Performance"
I have learned a lot from you folks in only 3 days of reading.? ?It will make my upcoming Technician class even more hands-on for the students.....
Gordon
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His -10dbm vfo is going into the rf port of one of the mixers,
as shown in the block diagram near the top of that webpage.
On Wed, Oct 25, 2017 at 07:50 am, Jerry Gaffke wrote:
I have no idea where his -10 dbm vfo is going.
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His -10dbm vfo is going into the rf port of one of the mixers,
as shown in the block diagram near the top of that webpage.
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On Wed, Oct 25, 2017 at 07:50 am, Jerry Gaffke wrote:
I have no idea where his -10 dbm vfo is going.
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By "carrier", perhaps you mean the incoming signal to the RF port.
That does make sense.
But will vary wildly with the type of mixer.
A level 17 diode ring mixer can take a much bigger rf signal than a level 3 diode ring mixer.
I assume up by 14 db.
And both with do far better than an ne612 mixer.
Jerry
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On Wed, Oct 25, 2017 at 05:19 am, Mvs Sarma wrote:
In a mixer , if the carrier level is above -10dbm,? spurs do occur.
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Here's a more complete quote from that webpage, also showing the previous paragraph. ?He's got some high level diode ring mixers that want +17 dbm and +7 dbm at the local oscillator port. ?The mixers on the ubitx have schottky diodes, and should have around +3 dbm at the LO port ?The local oscillator should be much stronger than the strongest incoming signal at the RF port.
I have no idea where his -10 dbm vfo is going.
Jerry
The VFO and Crystal oscillators are fed into a double balanced diode mixer and then filtered by 10 separate relay switched 2 section Series C BPF's (bandpass filters). Some may question the wisdom of using only a 2 section filters at this stage, however the receiver input BPF's (which are also shared with the transmitter) are 3 section filters and provide adequate stop band attenuation. After filtering, further amplification increases the LO power output where it is split into three separate outputs, +17 dBm for the receiver mixer, -5 dBm to the transmitter board (later to be amplified to +7 dBm for the transmitter mixer) and a low level output for the frequency counter.?
When I first built the LO system I did not pay attention to setting the VFO output level and for reasons I can't remember, the VFO output was 0 dBm. After connecting the LO to the receiver mixer I found a number of spurs that shouldn't have been there. Wes, W7ZOI came to my rescue explaining the importance of not driving the RF port of a balanced mixer with more than -10 dBm. After decreasing the VFO output to -10 dBm the spurs disappeared. The VFO is built into a box made of PC board material. The 10 crystals oscillators and LO mixer are built into the top half of a box made of PC material. The bottom half of the box contains the 10 BPF's and an amplifier to boost the LO output power to the desired level.?
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On Wed, Oct 25, 2017 at 05:24 am, Mvs Sarma wrote:
the comment is here under quote
"When I first built the LO system I did not pay attention to setting the VFO output level and for reasons I can't remember, the VFO output was 0 dBm. After connecting the LO to the receiver mixer I found a number of spurs that shouldn't have been there. Wes, W7ZOI came to my rescue explaining the importance of not driving the RF port of a balanced mixer with more than -10 dBm. After decreasing the VFO output to -10 dBm the spurs disappeared. The VFO is built into a box made of PC board material. The 10 crystals oscillators and LO mixer are built into the top half of a box made of PC material. The bottom half of the box contains the 10 BPF's and an amplifier to boost the LO output power to the desired level."
?Link
http://www.ve7ca.net/Hbr200.htm
read just abovesubheading 6.rf filters
all the best
?reagards
?sarma vu3zmv
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Well that makes sense.
A 50 ohm load is asking an awful lot from the CMOS output of the si5351.
The si5351 has only one pin for the 3.3v rail.
Loading multiple outputs heavily means the internal 3.3v rail will be getting jerked around,
and you will see crosstalk between those outputs.
You might try adding a buffer amp between the si5351 and your 50 ohm load.
Perhaps steal the buffer at Q7 from the bitx40 at ???Q7 is an mmbt3904.
Jerry
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On Wed, Oct 25, 2017 at 04:32 am, Jean-Matthieu F5RCT wrote:
I'm sorry but the spurs are getting worse if I terminate all outputs to 50 Ohms !
If only one ouptut is activated the signal is clean !
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Re: Help with troubleshooting Bitx40 - no transmit.
#bitx40help
It's good you posted this information with such a clear photo. But I have a thing about giving credit where credit is due, especially if that source can give needed additional details. The back-to-back diode mod comes from Raj: ?? /g/BITX20/message/19105Note that he suggested adding an incandescent lamp, which can be quite effective: /g/BITX20/message/21901Here's a few more notes about what can blow in that transmitter: /g/BITX20/message/31352As mentioned previously, I believe Don Cantrell is the source of the 100pf mod to the LPF. His blog post gives considerable detail, including before and after plots: ??? Jerry, KE7ER
On Wed, Oct 25, 2017 at 06:31 am, Al Duncan VE3RRD wrote:
Don't forget to add the two 1N4148 protection diodes as shown at . Worthwhile added insurance for your BITX40.
73, AL? VE3RRD
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You can put them back if you wish after testing, but "they aren't serving any purpose and can be removed from the board"
means you don't have to.
K1 is one of the two big black boxy things on your board, a relay (which could be called a solenoid switch).
The relays are labeled K1 and K2 in the schematic at ? ?
Perhaps a bit confusing as each one has two double pole switches plus a coil in the schematic, and while close together
they don't have a box around them. ?Each relay has pins into the board labeled in the schematic as??1,3,5,8,9,12,14,16
If you put amps through a part of your DVM that was expecting milliamps, that part of it is probably blown.
At least the shunt resistor used for milliamps is blown. ?Could be the damage went further.
Test your meter somehow. ?For example, a 12v battery through a 1k resistor will give 12v/1000ohms = 0.012 amps = 12 milliamps
and the resistor will have to dissipate 12v*0.012a = 0.144 watts, so a quarter watt resistor should do fine.
And 12v/10ohms = 1.2 amps, but that 10 ohm resistor will be dissipating 12*1.2=14.4 watts,
so you would want at least a 5 watt resistor for a quick one second test. ?That resistor will get very hot very quickly.
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On Wed, Oct 25, 2017 at 03:26 am, Barrett O wrote:
Since D7 and C130 ?aren't wired up right, they aren't serving any purpose and can be removed from the board
You mean remove just temporary for testing??
I'm guessing k1 is the solenoid switch right
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Re: Help with troubleshooting Bitx40 - no transmit.
#bitx40help
Don't forget to add the two 1N4148 protection diodes as shown at . Worthwhile added insurance for your BITX40.
73, AL? VE3RRD
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the comment is here under quote
"When I first built the LO system I did not pay attention to setting the VFO output level and for reasons I can't remember, the VFO output was 0 dBm. After connecting the LO to the receiver mixer I found a number of spurs that shouldn't have been there. Wes, W7ZOI came to my rescue explaining the importance of not driving the RF port of a balanced mixer with more than -10 dBm. After decreasing the VFO output to -10 dBm the spurs disappeared. The VFO is built into a box made of PC board material. The 10 crystals oscillators and LO mixer are built into the top half of a box made of PC material. The bottom half of the box contains the 10 BPF's and an amplifier to boost the LO output power to the desired level."
?Link
http://www.ve7ca.net/Hbr200.htm
read just abovesubheading 6.rf filters
all the best
?reagards
?sarma vu3zmv
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Giancarlo - I7SWX
Brent Seres/ VE3CUS
