Date   
Re: Oscillation problems Bitx20a

Arv Evans
 

FOKO

The "Miguel" mod that you are talking about has become a de-facto standard for the QRP-Kits version of BITX.  It decreases higher frequency gain of the IRF510's and makes them less suceptible to oscillation if the antenna feedpoint impedance is too high.  These components are usually just soldered across the indicated points on the bottom of the PCB.  

Arv K7HKL
_-_






Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: Fokko PH0KKO <kaapstad1@...>
Date: 5/29/18 12:46 AM (GMT-07:00)
To: BITX20@groups.io
Subject: [BITX20] Oscillation problems Bitx20a

I built a Bitx dead-bug-style for 40 meters based on the Bitx20a schematic but I have some oscillation problem. I set the driver bias and both final biases to 50 ma and the drive adjust about a quarter of the way up. Sofar nothing wrong.

But as soon as I connect the signal generator it starts oscillating, even after disconnecting the signal and turning the drive adjust all the way down. I use a 40A switching PSU so that should be able to handle it, my amp meter does not show any fluctuation.

There are some suggestions in the Bitx20a manual but I don' t quite know hoe to interpret them: "mounting a 220 ohm resistor between C6/R13 and the collector of Q3", does that mean leave everything else as it is and add an extra resistor between these points? Or does it mean: cut the connection going from C6/R13 to T3 and put a 220 ohm resistor in between?

The same goes for "mount a 1k resistor between the drains of Q18 and Q19". Also here, should I leave it as it is and simple add a 1k resistor over the drains of these MOSFETs or put them in line between the MOSFETs going to T2? This is not clear to me. I hope someone can advise me.

 

Re: Instruction Manual needs revision #ubitx

W7PEA
 

Yes! There's a wiki on doing a vanilla buid I started for the same reasons you mention.  https://groups.io/g/BITX20/wiki/uBITX-Assembly

It's not mine, it's the groups, so feel free to improve it. 
W7PEA

Re: A steal for Arduino Experimenters

Jack, W8TEE
 

Mornin' Joel:

Agree 100%. The CAT people do need the interface and the reason I push that more than the non-USB versions is because much of my work is done with people who don't have much (any?) programming experience and the familiar USB connector lowers the hurdles in their minds. After I put JackAl to bed, I'm going to do a project with the new Protoneer board, which is about the same size as the Nano, but with a 3x clock and 32K of SRAM.

Jack, W8TEE

On Tuesday, May 29, 2018, 10:11:53 AM EDT, Joel Caulkins <caulktel@...> wrote:


Jack,

You are so right about the clones. My first was a authentic Arduino UNO that I bought from Radio Shack for 30 bucks, (so I've paid the tax), now I have maybe 40 clones of all flavors including a dozen plain ATmega328PU chips for building directly into my projects. When you get right down to it, a Arduino is nothing but a 328 chip and a 16Mhz crystal and a couple of 22pf caps, (overly simplified I know). I also agree with Jerry about using Pro Minis, it's not necessary to have all that USB circuitry sitting there running for a occasional firmware update when you can just plug a USB TTL Serial adapter in, do your update and remove it. Of course this wouldn't work if you needed CAT control, I don't. That Banggood kit is a great deal for getting started building Arduino projects.

Joel
N6ALT

I would like to chat with someone that has set there ubtx up with a raspberry pi and is using fl digi,

Tony D'Angelo <tony_d_33931@...>
 

I would like to chat with someone that has set there ubtx up with a raspberry pi and is using fl digi,

I think this may be a good way to go as I have most of the parts. Not sure if I need an external sound card or diarwolf or both. I do have a pi tnc but I don’t think that would be much help here. Please I want to chat with some one who has done this no please no “helpful guys with a bunch of links.”  We all know what I’m talking about! LOL

Thanks

Re: A steal for Arduino Experimenters

 

Oh, I forgot to add that we can make the ATmega328 even easier by eliminating the 16Mhz crystal and the two 22pf caps, and use the internal 8Mhz clock which runs a si5351 and OLED display just fine with no noticeable difference.

Joel
N6ALT

Re: audio dropping out

 

Dave,

Solder a wire to the 2822 audio chip 12v in PIN 2 and monitor the voltage when this audio dropout happens.
A plated through hole may not be conducting properly if the voltage is dropping!

OTOH, your audio chip maybe bad.

Raj


At 29/05/2018, you wrote:
On Mon, May 28, 2018 at 12:39 pm, Jerry Gaffke wrote:
Does the problem also occur when you have the volume set so low that you can barely hear it?

I want to say no it does not. It seems to be happening only when the vol pot is at half way position, or higher, and a loud station comes on.  I hear a crackling noise as the sound drops out fairly quick. Then, it will also come back the same way, by itself with no intervention from me. (Like I said earlier, sometimes if I touch the range and yellow wires the sound comes back. Now, I don't know if this was just coincidence.)   It also happens while I am tuning up on whatever band and I have the volume too high. If I turn it down, it seems to stop.

Thanks,
Dave
 

Re: A steal for Arduino Experimenters

 

Jack,

You are so right about the clones. My first was a authentic Arduino UNO that I bought from Radio Shack for 30 bucks, (so I've paid the tax), now I have maybe 40 clones of all flavors including a dozen plain ATmega328PU chips for building directly into my projects. When you get right down to it, a Arduino is nothing but a 328 chip and a 16Mhz crystal and a couple of 22pf caps, (overly simplified I know). I also agree with Jerry about using Pro Minis, it's not necessary to have all that USB circuitry sitting there running for a occasional firmware update when you can just plug a USB TTL Serial adapter in, do your update and remove it. Of course this wouldn't work if you needed CAT control, I don't. That Banggood kit is a great deal for getting started building Arduino projects.

Joel
N6ALT

Re: Simple sound card interface #ft8

Doug W
 

here's what I did...
https://groups.io/g/BITX20/wiki/Digital-Setup
--
www.bitxmap.com

Re: audio dropping out

Dave de WS1ETI <docame12@...>
 

On Mon, May 28, 2018 at 12:39 pm, Jerry Gaffke wrote:
Does the problem also occur when you have the volume set so low that you can barely hear it?
I want to say no it does not. It seems to be happening only when the vol pot is at half way position, or higher, and a loud station comes on.  I hear a crackling noise as the sound drops out fairly quick. Then, it will also come back the same way, by itself with no intervention from me. (Like I said earlier, sometimes if I touch the range and yellow wires the sound comes back. Now, I don't know if this was just coincidence.)   It also happens while I am tuning up on whatever band and I have the volume too high. If I turn it down, it seems to stop.

Thanks,
Dave
 

Re: RF power chain mods and improvements..

Kelly Jack
 

Hi all,

Some more testing and mods.

Measured efficiency of the PA only when RV1 adjusted for 10W output on each band (current measured through the PA-PWR line, current is zero during receive):
80m  29%
40m  29%
30m  33%
20m  30%
17m  34%
15m  45%
12m  41%
10m  45%

Not good.

Changed T11 to BN43-3312 same wire and turns ratio, 2 primary to 4 secondary.

Power measured using same method as above with BN43-3312 no cap across the primary, each band set to 10W by adjusting RV1.

80m  40%
40m  39%
30m  46%
20m  44%
17m  41%
15m  49%
12m  48%
10m  50%

Much better and finals are cooler but still get hot with key down for 30 seconds. Some acceptable numbers there but why is efficiency increasing with higher frequency?

Note that power efficiency measurements are for the finals only.

73



Simon
VK3ELH



 

Re: RF power chain mods and improvements..

Kelly Jack
 

Hi all,

Some more testing tonight.

Measured efficiency with mods per earlier post was low as follows:

Band                            Efficiency
80                  29%
             15
40                                 10                                                                         20
30                                 10                                                                         20
20                                 9                                                                           19
17                                10                                                                          22
15                                10                                                                          18
12                                8                                                                            16
10                                6                                                                            16

Re: Receive FM Radio Station #bitx40

Mike aka KC2WVB <rb5363@...>
 

Since your building your rig from scratch this will be easy for you to accomplish.

Once everything is working. Modify the amp that the microphone feeds by doing this:

"I lhave changed just R63 so now it is 24 ohm (I added 2 ordinary 100ohms resistors in parallel) as suggested. I confirm it increases the average power to the right level given the stock mic element."

This is the fix people are using to increase the gain. Its the one that I can't do because my hands are not steady enough to pull it off. Hence I am going the route of adding a pre-amp which I intend to make variable. Apparently without this change the audio being mixed into the RF is too weak and one needs to speak rather loudly to be heard on receive.

Good luck and I am rooting for your success.

On Tue, May 29, 2018, 8:07 AM Mike aka KC2WVB <rb5363@...> wrote:
Incidentally, what is your call sign?? I want to listen for you once you have the bugs worked out and the rig up and running.

On Tue, May 29, 2018, 7:54 AM Mike aka KC2WVB <rb5363@...> wrote:
What ever the outcome you did great! Most people did not build from scratch and source their own parts.

Too bad my lack of knowing your language may make it difficult to be of much help. However, let me ask this simple question. What are you using for an antenna? If it is not something like a dipole cut to 40 meters or 20 meters or 80 meters...then you may hear nothing but noise and interference on the receiver. 
My version of the radio came to life when I connected a 40 meter dipole to the rig. The 40 meter dipole is two wires each 32.5 feet long connected at one end to either the center conductor or shield of 50 ohm coax cable. The other end of the coax runs to the rig. The feed point of this antenna, I.e. where the wires connect to the coax, is ideally elevated to 1/4 wave length in height or roughly 33 feet.
I could not elevate my 40 meter dipole so I built a compromise dipole. The issue that occurs when the dipole is not elevated to 1/4 wavelength is that the feedpoint impedance becomes terribly low to the point it is far short of 50 ohms and nearly nothing can then be heard. So, I made my dipole as a folded dipole that uses two wires on each leg. This raises the feedpoint impedance of the antenna to such an extent that it is actually spot on 50 ohms when it is barely off the ground. This of course changes the radiation pattern but not enough that I don't still pick up Dave, on or about 7.145 MHz, out of England whenever he keys up.

AgIn good luck, hope you get the bugs worked out.

On Tue, May 29, 2018, 4:12 AM <qonita.salimah@...> wrote:

Thank you for your reply.
I also tried to make the wire connectivity in Baofeng mic and speaker according to the post in this threads : https://groups.io/g/BITX20/topic/4554574

The PTT switch in Baofeng work perfectly, but not for the speaker and mic. I will try to make the modification like you've said.

But what about the RX system? It still not receiving any ham radio signal. I tried to follow the troubleshooting that Asshar Farhan made in https://www.youtube.com/watch?v=R8G8XAwq38A&t=456s
Here is what I've got

C107 (C13 in my schematic) makes noise when it's touched with cable.
C33 (C6) is also make noise
C31 (C9) is also make noise, but not very loud.
C53 (C5) I didn't hear any noise at all. 
C21 (C24) I didn't hear any noise at all. 

I also didn't hear any noise if the cable touched the antenna connector.

I made my own BPF and LPF because I want to make 8.456 MHz frequency as the center frequency.

Here is the schematic. To tell you the truth I didn't buy the kit from Asshar Farhan. I built in from scratch, like from the schematic, the PCB layout, and bought all the component by myself. I come from Indonesia. And this is for my final project. Still learning and this is my first time building a radio

Thank you very much for helping me

Re: FS: Bitx AGC Kits

Dave <k4em@...>
 

Is there a non-SMD board version available, SMD is too small for me. If you have the eagle files, I could send off to OSHPark would be fine. Thanks.

Dave
k4em

Re: Receive FM Radio Station #bitx40

Mike aka KC2WVB <rb5363@...>
 

Incidentally, what is your call sign?? I want to listen for you once you have the bugs worked out and the rig up and running.


On Tue, May 29, 2018, 7:54 AM Mike aka KC2WVB <rb5363@...> wrote:
What ever the outcome you did great! Most people did not build from scratch and source their own parts.

Too bad my lack of knowing your language may make it difficult to be of much help. However, let me ask this simple question. What are you using for an antenna? If it is not something like a dipole cut to 40 meters or 20 meters or 80 meters...then you may hear nothing but noise and interference on the receiver. 
My version of the radio came to life when I connected a 40 meter dipole to the rig. The 40 meter dipole is two wires each 32.5 feet long connected at one end to either the center conductor or shield of 50 ohm coax cable. The other end of the coax runs to the rig. The feed point of this antenna, I.e. where the wires connect to the coax, is ideally elevated to 1/4 wave length in height or roughly 33 feet.
I could not elevate my 40 meter dipole so I built a compromise dipole. The issue that occurs when the dipole is not elevated to 1/4 wavelength is that the feedpoint impedance becomes terribly low to the point it is far short of 50 ohms and nearly nothing can then be heard. So, I made my dipole as a folded dipole that uses two wires on each leg. This raises the feedpoint impedance of the antenna to such an extent that it is actually spot on 50 ohms when it is barely off the ground. This of course changes the radiation pattern but not enough that I don't still pick up Dave, on or about 7.145 MHz, out of England whenever he keys up.

AgIn good luck, hope you get the bugs worked out.

On Tue, May 29, 2018, 4:12 AM <qonita.salimah@...> wrote:

Thank you for your reply.
I also tried to make the wire connectivity in Baofeng mic and speaker according to the post in this threads : https://groups.io/g/BITX20/topic/4554574

The PTT switch in Baofeng work perfectly, but not for the speaker and mic. I will try to make the modification like you've said.

But what about the RX system? It still not receiving any ham radio signal. I tried to follow the troubleshooting that Asshar Farhan made in https://www.youtube.com/watch?v=R8G8XAwq38A&t=456s
Here is what I've got

C107 (C13 in my schematic) makes noise when it's touched with cable.
C33 (C6) is also make noise
C31 (C9) is also make noise, but not very loud.
C53 (C5) I didn't hear any noise at all. 
C21 (C24) I didn't hear any noise at all. 

I also didn't hear any noise if the cable touched the antenna connector.

I made my own BPF and LPF because I want to make 8.456 MHz frequency as the center frequency.

Here is the schematic. To tell you the truth I didn't buy the kit from Asshar Farhan. I built in from scratch, like from the schematic, the PCB layout, and bought all the component by myself. I come from Indonesia. And this is for my final project. Still learning and this is my first time building a radio

Thank you very much for helping me

Re: Receive FM Radio Station #bitx40

Mike aka KC2WVB <rb5363@...>
 

What ever the outcome you did great! Most people did not build from scratch and source their own parts.

Too bad my lack of knowing your language may make it difficult to be of much help. However, let me ask this simple question. What are you using for an antenna? If it is not something like a dipole cut to 40 meters or 20 meters or 80 meters...then you may hear nothing but noise and interference on the receiver. 
My version of the radio came to life when I connected a 40 meter dipole to the rig. The 40 meter dipole is two wires each 32.5 feet long connected at one end to either the center conductor or shield of 50 ohm coax cable. The other end of the coax runs to the rig. The feed point of this antenna, I.e. where the wires connect to the coax, is ideally elevated to 1/4 wave length in height or roughly 33 feet.
I could not elevate my 40 meter dipole so I built a compromise dipole. The issue that occurs when the dipole is not elevated to 1/4 wavelength is that the feedpoint impedance becomes terribly low to the point it is far short of 50 ohms and nearly nothing can then be heard. So, I made my dipole as a folded dipole that uses two wires on each leg. This raises the feedpoint impedance of the antenna to such an extent that it is actually spot on 50 ohms when it is barely off the ground. This of course changes the radiation pattern but not enough that I don't still pick up Dave, on or about 7.145 MHz, out of England whenever he keys up.

AgIn good luck, hope you get the bugs worked out.

On Tue, May 29, 2018, 4:12 AM <qonita.salimah@...> wrote:

Thank you for your reply.
I also tried to make the wire connectivity in Baofeng mic and speaker according to the post in this threads : https://groups.io/g/BITX20/topic/4554574

The PTT switch in Baofeng work perfectly, but not for the speaker and mic. I will try to make the modification like you've said.

But what about the RX system? It still not receiving any ham radio signal. I tried to follow the troubleshooting that Asshar Farhan made in https://www.youtube.com/watch?v=R8G8XAwq38A&t=456s
Here is what I've got

C107 (C13 in my schematic) makes noise when it's touched with cable.
C33 (C6) is also make noise
C31 (C9) is also make noise, but not very loud.
C53 (C5) I didn't hear any noise at all. 
C21 (C24) I didn't hear any noise at all. 

I also didn't hear any noise if the cable touched the antenna connector.

I made my own BPF and LPF because I want to make 8.456 MHz frequency as the center frequency.

Here is the schematic. To tell you the truth I didn't buy the kit from Asshar Farhan. I built in from scratch, like from the schematic, the PCB layout, and bought all the component by myself. I come from Indonesia. And this is for my final project. Still learning and this is my first time building a radio

Thank you very much for helping me

Re: A steal for Arduino Experimenters

AGØH
 

Thanks, Lee.  I already have the book by Jack.  The kit of added parts seemed like a good buy and I thought the PDF which was corrupted would help to explain how some of the components could be used.  
Keith - AGØH 

Re: Simple sound card interface #ft8

John
 

I bought an el cheapo USB soundcard on eBay, also because my laptop has a combined audio port.
Has been working great for me combined with a USB cable for CAT control.

John
KG5WJQ

Re: #bitx20 #bitx40 #bitx20 #bitx40

vu3dkk@...
 

OK I got formula,Then using this,how to rewind the output transformer?

Re: Oscillation problems Bitx20a

Bill Meara
 

Foko:  First, congratulations on the dead-bug scratch built BITX.    

I too had instability problems.   That is normal.   You just have to be patient and think logically to cure the problem.   Try to figure out which stage is at fault and how the unwanted feedback is happening.   Then break the feedback loop.  

Here are some blog posts about my problems.  They may help you.   You can probably find more posts like this on my site.  




Hang in there.   Good luck.  Keep us informed on your progress.   

73  Bill N2CQR    

On Tuesday, May 29, 2018, 2:46:24 AM EDT, Fokko PH0KKO <kaapstad1@...> wrote:


I built a Bitx dead-bug-style for 40 meters based on the Bitx20a schematic but I have some oscillation problem. I set the driver bias and both final biases to 50 ma and the drive adjust about a quarter of the way up. Sofar nothing wrong.

But as soon as I connect the signal generator it starts oscillating, even after disconnecting the signal and turning the drive adjust all the way down. I use a 40A switching PSU so that should be able to handle it, my amp meter does not show any fluctuation.

There are some suggestions in the Bitx20a manual but I don' t quite know hoe to interpret them: "mounting a 220 ohm resistor between C6/R13 and the collector of Q3", does that mean leave everything else as it is and add an extra resistor between these points? Or does it mean: cut the connection going from C6/R13 to T3 and put a 220 ohm resistor in between?

The same goes for "mount a 1k resistor between the drains of Q18 and Q19". Also here, should I leave it as it is and simple add a 1k resistor over the drains of these MOSFETs or put them in line between the MOSFETs going to T2? This is not clear to me. I hope someone can advise me.

 

Re: A steal for Arduino Experimenters

David Wilcox
 

I bought the Elegoo starter kit for $30.00 and it came with a little CD with all the files on it.  Was well worth the money.  You can go to the Elegoo site too and download their starter files.  I am sure most of the starter programs are similar.

Here is the beginning page: https://www.elegoo.com/download/

The kit I have is the basic one for the Mega 2560.  I couldn't download the file on my old iPad for some reason but you can with a real computer.  

I am surprised you aren't getting better service from Bangood.  I haven't had any problems with their stuff so far.  I prefer Adafruit though as their service is fantastic.

As long as you have the kit any beginning book about beginning Arduino should give you the lessons on how to use it.  The Arduino website itself has lots of information.  Looking over many of the starter kits available they all have the same or similar parts.  You just need the lessons.

FWIW, your mileage may vary.

Dave K8WPE 

On May 28, 2018, at 9:25 PM, AGØH <kmilr1@q.com> wrote:

I ordered and received the Basic Starter Kit from Bangood.  The kit, however, has no 'help' manual but a later post included a web address from Bangood to send for the free PDF starter guide.  That link did not work.  I wrote Bangood and, after two requests, received a 75mb zipped file.  I tried to unzip it and was given the message that the file couldn't be unzipped as it was corrupted.
Several requests to Bangood to send re-send the file have fallen on deaf ears.
So......has anyone received the PDF that could forward me a copy?  It would be greatly appreciated as this nubee needs all the help he can get in experimenting with the Arduino. 

Thanks,
Keith AGØH