Date   
Re: Results of MAX9814 in uBitx #ubitx

Tim Gorman
 

John,

Good job!

tim ab0wr

On Tue, 27 Feb 2018 20:42:11 -0800
"John" <passionfruit88@...> wrote:

After trying a few schemes I have settled on a MAX9814 circuit for
the AGC.

I used the Adafruit board but there are a few variations on eBay with
some probably requiring less hacking than the Adafruit design. I had
to solder a wire on a SMD component to access the CT (time constant
capacitor) pin of the MAX IC, and remove the Electret capsule.

I have attached the schematic and a few pictures of the AGC circuit
as I now have in the rig. The 5VDC is taken from the Raduino board.  

Performance wise I took two sets of measures, one with the AGC turned
down low and one with the AGC turned one third of the way up.

A few notes on the tests. I used an A/B comparison with an FT-817,
with the pre-amp off, receiving  a carrier at 1,500Hz  from local
radio stations (with attenuation). The FT-817 S-Meter seem
notoriously non-constant in the steps between the S-units, but that
is all the reference I have where I am. The AGC voltage is taken from
the CT pin of the MAX9814.

The AGC voltage fluctuates quite a lot, so I tried to record the
average value.

At high signal strength, to determine if the saturation was coming
from the AGC circuit or the uBitx upstream, I would bypass the AGC
and keep the volume down to prevent the audio circuit past the volume
pot from saturating. If the harmonics of the audio disappeared, the
AGC alone was producing distortion, otherwise it appeared at least
before the AGC, and possibly in as well.

Here are the results:

1. "Medium" AGC: input pot turned to about 30% of full scale.

FT817         AGC
S-Meter     voltage(mV)       Notes
S0                  0               
S1               300
S2               350
S3               400
S4               460
S5               510
S6               650
S7               750
S8             1,700         Large variation. FT-817 S-meter S8
plateau issue? S9            2,200          Some saturation of AGC
noted (starts to appear in audio FFT, not noticeable) S9+10
 2,460           Saturation of AGC audible, but not unplesant. S9+20
   2,460           Audible saturation of both uBitx and AGC (harsh
sound).

The AGC kicks in early and keeps the volume pretty constant until
saturation occurs. Saturation of AGC does limits the dynamic range of
receiver.

1. "Low" AGC: input pot turned to about 7-10% of full scale.

FT817          AGC
S-Meter      voltage (mV)       Notes
S0 -S4               0                                
S5                50-200            (100mv avg)
S6                  200
S7                  360
S8                  500
S9                1,260
S9+10         1,800
S9+20         2,300                 Saturation of both uBitx and AGC
(visible in audio FFT, but not really audible) S9+30         2,400
             Audible saturation of uBitx and mostly of AGC.

This is the most "FT-817 AGC" like, from my perspective, and is what
I have settled for.  I want to use the AGC voltage as an s-meter
input and this setting does produce a gap at the bottom end, but this
is not critical IMO.

In both cases I noted some small "clicks" when the AGC kicked in on
strong sudden signals. 

The maximum gain of the MAX9814 as set in the schematic attached is
of 50dB and requires screened cables in the audio circuit. I
originally had the input and output of the circuit fed to a two core
"stereo" screened cable and I would get feedback. I had to use two
single screened audio cables.

73, John (VK2ETA)

Re: uB Shipped!!

Michael Baker
 

I got payment confirmation on January 4 and still waiting for my second one to be shipped.

Re: Designing Maritime Radio #bitx40

qonita.salimah@...
 

Thank you for your reply..

There is no requirement for the modulation itself, I think SSB is good enough and suitable for my project. Did one RF-Front End circuit work for both transmit and receive system?

What about the Crystal Filter Circuit, should I make change on the circuit? Did the Crystal Circuit aim is for keeping the IF Frequency fixed tuning in 12 MHz? 

Thank you

 

Re: ergonomic design of front panel

Tim Gorman
 

Michael,

I like your layout. I am considering putting the on/off switch on the
back as well in order to keep it close to the power connector.

I have a bit larger case than yours. I have a four pin mic connector
that will mate with most of my older ham and cb microphones (mic +
ptt) so it probably needs to go up front. The cw key can easily be on
the back panel, that's a good idea.

Thanks,

tim ab0wr

On Tue, 27 Feb 2018 17:37:32 -0800
"Michael Babineau" <@ve3wmb> wrote:

Tim : 

I did something similar with the BITX40.

If you tune with your left hand and don't put the tuning Knob on
the left that you will likely find that you obscure the display when
you are tuning. I use a Computer headset with my Bitx40 and it has
long leads so I opted to put mic/phones/ptt and key jack all on the
back panel. IMHO the front panel is already busy enough with the
display, tuning and volume etc. Attached is a photo of my BITX40
front panel. I intend to do something similar with my uBITX when I
get around to it.

Cheers

Michael VE3WMB

Re: Another shipping Notification Update

Jason Schlager
 

I ordered Dec 23. Arrived Feb 22 in USA. Paypal had DHL tracking entered on Feb 19.  I never received notice of it being shipped. Also, there were no duties or taxes.

--
Jason Schlager
KM6AUS

Re: Better Schematic

Jerry Gaffke
 

The uBitx surface mount R's and C's are all in the 1206 package.
The surface mount 2n3904's are are mmbt3904's.
The audio amp is the TDA2822M variant (M says it's in the 8 pin DIP package).


On Wed, Feb 28, 2018 at 05:54 am, Walter wrote:
What value SMD's do you think these are? I see 0603,0805, 1206. 

Re: troubleshooting no TX SSB #ubitx #ubitx-help

Jerry Gaffke
 

So "didn't have power on SSB" means you didn't see power into a wattmeter (with dummy load) when attempting to transmit?
Have you tried transmitting CW with a hand key?
Is that scope good to 10mhz or so?

Inspect the entire board carefully under good light and with magnification for damage somewhere in shipping.
Often the torroids have trouble with broken or shorted wires, or enamel left on the wire, or an otherwise
poor solder job.  However, if the receiver worked, all torroids except those between Q90 and the IRF510's
are probably ok, and the mixers and local oscillators are fine.
The TX side of the BiDi amps is probably ok since they are simple and auto-stuffed and seldom have trouble.

Switch to one of the low bands like 80m or 40m, hopefully within range of the scope
Remove power (PA-PWR) from the IRF510's so you don't have to worry about dummy loads and such
while debugging the transmitter, when things are working you should see a couple volts of RF at the
gates of the IRF510's.

When pressing PTT with no input to the microphone, all those 2n3904's at Q90,911,912,92,93,96,97 
should have around 0.6 volts dc between base and emitter, and the emitter should be a little bit above ground. 
You can check this with a DVM.  Do they all look ok?

When speaking into the mike or using the hand key, I believe the base of Q90 will have something on the
order of 50mv rms of RF on it at the operating frequency, can you see that with the scope?

If Q90 is getting RF, then follow that on through the other stages, should see a volt or two rms
of RF at the gates of the IRF510's.  The gates of the IRF510's should be biased by RV2 and RV3 to
around 3 or 4 volts (but DON'T twiddle RV2 and RV3 unless monitoring quiescent drain current at PA-PWR). 

If you do see RF at the IRF510 gates, then it's time to attach a dummy load and restore PA-PWR,
see if the dummy load gets signifcant power when attempting to transmit.
If not, do the drains of the IRF510's get 12v dc when ptt is pressed?
Does PA-PWR current go up to 200ma or so (100ma of quiescent drain current per IRF510) when pressing ptt
with no audio into the mike, demonstrating that the IRF510's are probably working fine?

Jerry, KE7ER


On Wed, Feb 28, 2018 at 12:37 am, John wrote:
Last week I received my uBitX. AFter wiring up I discovered that I didn't have power on SSB.
The next day when i wanted to investigate my problem I smoked U1 when I plugged in my headphones.

Tonight I unsoldered U1 and after that I powered up. Measured with the scope and I see a signal at the Mike input and on the collector of Q6. So that first part seems to be okay.

What would be the next step to backtrack the fault?

Re: Ubitx case #ubitx

Neil Goldstein
 

Should we add Carl's case to the ubitx.net enclosures section.

I purchased one of these, by the way, and the quality is excellent!!

--Neil, W2NDG

Re: uB Shipped!!

Karl Schwab
 

Hurray Vince!  Let me know when you get it on the air, and I'll listen for you!  Karl, KO8S


On Tuesday, February 27, 2018 10:35 AM, Vince Vielhaber <vev@...> wrote:



Ok, for all those waiting...  I just got a ship notice that my uB has
shipped (today 2/27) and will be here on thursday (3/1).  I ordered on
12/28.

Vince.
--
                          http://www.metalworkingfun.com





Re: Designing Maritime Radio #bitx40

Chris Brewer
 

Hello Qonita,

One consideration you may need to address is that the bitx family transmits and receives single sideband (SSB) modulated signals. If your application requires AM modulation instead then significant modifications would be required.

If SSB is ok, then in general you would need to modify the tuned circuits in the RF front end to match the new band and edit the Raduino software to set a different local oscillator frequency.

Of course, there will be many other details to address, including software changes to support your specific restrictions and requirements.

Regards,
Chris Brewer, AC9GN

On Feb 28, 2018 8:55 AM, <qonita.salimah@...> wrote:
My name is Qonita, and I am a student i my last semester. I'd like to learn about BITX40 because it is very suitable for my last project. 
So my project is to make a HF communication system for Fisherman Ship and the Coast Station. The frequency is already been stated by the government. It were 8.222 MHz (for the Ship) and 8.746 MHz (for the Coast). The Ship Station can transmit voice and GPS location (simple digital data, just 9 digit of MMSI ship code and location from the GPS Satellite), but can only receive voice. For the Coast Station, can only transmit voice, but can receive voice and digital data.
I think BITX40 can be a perfect example module for the voice communication. Can anyone explain to me what parts of BITX40 that I should change for the required frequency?
 
Thank you very much
 
 

Re: Speaker Jack

Richie Chambless
 

Hello Walter,

I have been doing some work around this same subject. You can take the low-level audio signal to an external amplifier by connecting the signal in to Vol-H (R170). This is the yellow wire coming off of the audio connector (diagram on HF Signals is incorrect). You can also reduce the headphone volume by inserting two small value resistors (under 100 ohm) in series with the output of the audio amp. Do this by connecting the output of the amp to pins 4&5 of the headphone jack. Now put the resistors across pins 1&2. I hope that makes sense! Google the Realistic DX-160 schematic to see what I’m talking about.

Designing Maritime Radio #bitx40

qonita.salimah@...
 

My name is Qonita, and I am a student i my last semester. I'd like to learn about BITX40 because it is very suitable for my last project. 
So my project is to make a HF communication system for Fisherman Ship and the Coast Station. The frequency is already been stated by the government. It were 8.222 MHz (for the Ship) and 8.746 MHz (for the Coast). The Ship Station can transmit voice and GPS location (simple digital data, just 9 digit of MMSI ship code and location from the GPS Satellite), but can only receive voice. For the Coast Station, can only transmit voice, but can receive voice and digital data.
I think BITX40 can be a perfect example module for the voice communication. Can anyone explain to me what parts of BITX40 that I should change for the required frequency?
 
Thank you very much
 
 

Re: Ubitx case #ubitx

Carl Beck
 

I design a case for my uBITX. see the attached PDF File.  I print them on my 3D Printer and have had very good feedback from the ones I have sold.  Take a look.

Re: Better Schematic

Walter
 

On Wed, Feb 28, 2018 at 05:33 am, Kerr Smith wrote:
Hi Walter,

There is a clear schematic at the following location (found on the hfsignals site):

UBITX v3 pdf

This is for version 3 of the UBITX.

As for getting a selection of SMD resistors I would suggest getting a mixed pack from somewhere like Banggood:

SMD resistor kits

I have bought several of these small kits in the past and they are a great way to instantly (after shipping of course) get a wide range of resistor values.

I hope this helps,

Kerr
Outstanding Schematic and SMD source.  What value SMD's do you think these are? I see 0603,0805, 1206.  What is the standard size using for electronic projects like these?

Thanks for your help
 
--
73, W9KJO
Walter

Re: Low level hum in headphones on UBITX

Walter
 

On Wed, Feb 28, 2018 at 05:15 am, Thomas Smith wrote:
Hi Walter,
What are you using to power your UBITX?  If you are using a power supply plugged into your wall, this may be coupling 60 (50?) Hz noise into your rig.  If you are powering it from the wall, can you use a battery (even just temporarily) to see if that is the source?
Tom

On Wed, Feb 28, 2018 at 1:23 PM, Walter <W9KJO@...> wrote:
I notice while using headphones with my new UBITX that there is a low level hum in my headphones.  I only seem to notice this with the headphones at low volume.

Is there a fix for this?

Thanks

--
73, W9KJO
Walter

 

 

It is powered off the batteries from my solar system, 12vdc system used only for my ham radio station, no inverter (yet).  Four large deep cycle batteries charged by an MPPT Controller.  I check it for noise often.  I have a power supply on the batteries to make up for low charge at night but it was off at the time as that charger is disconnected by my Internet relays during the daytime.  I'm pretty sure there wasn't any noise introduced from my power supply,BTW

BTW, I am so impressed by the Solar System, now 2 years old, That I am going to build a second system to power much of my house in the near future.  These panels even provide charge under cloud cover, it drops from 15 amps to 3 or 4 amps but that is enough to keep the batteries at charge even when operating my station at 27 amp current draw with the batteries making up the difference.  The duty cycle is low enough, even while in digitial modes, that it keeps up on only a few amps.  I even use my 12vdc HF Amp while on solar power.  It's been amazing and reliable.

I do have a DC Boost Regulator installed in my UBITX to raise the PA Voltage to a stable 24vdc.  I thought this might be the noise so I disconnected it and used only the 13.8vdc from my batteries but the noise was still present.  So the boost regular it not causing the noise.

--
73, W9KJO
Walter

Re: Better Schematic

Kerr Smith
 

Hi Walter,

There is a clear schematic at the following location (found on the hfsignals site):

UBITX v3 pdf

This is for version 3 of the UBITX.

As for getting a selection of SMD resistors I would suggest getting a mixed pack from somewhere like Banggood:

SMD resistor kits

I have bought several of these small kits in the past and they are a great way to instantly (after shipping of course) get a wide range of resistor values.

I hope this helps,

Kerr

Re: ergonomic design of front panel

Michael Monteith
 

I totally agree with you Michael.  I think some realized it after they got things together.  I've seen them put the large 4 or 8 pin mic jacks next to the tuning knob.  That would drive me nuts.   Yours looks clean and smooth.   Ne mess cables in the front.  Even the side would be a better option than the front in my opinion. 

73, Michael
KM4OLT

Re: Low level hum in headphones on UBITX

Thomas Smith
 

Hi Walter,
What are you using to power your UBITX?  If you are using a power supply plugged into your wall, this may be coupling 60 (50?) Hz noise into your rig.  If you are powering it from the wall, can you use a battery (even just temporarily) to see if that is the source?
Tom

On Wed, Feb 28, 2018 at 1:23 PM, Walter <W9KJO@...> wrote:
I notice while using headphones with my new UBITX that there is a low level hum in my headphones.  I only seem to notice this with the headphones at low volume.

Is there a fix for this?

Thanks

--
73, W9KJO
Walter


Re: Another shipping Notification Update

Daniel Conklin <danconklin2@...>
 

I ordered mine on the 29th of December 2017, and I haven't gotten notice of shipping yet.
Dan W2DLC

Re: Audio buzz

 

Carl,

Bad connection on the power jack, see if you can find another jack from a discarded walwart the fits snugly.
Some have a slightly small hole and can be drilled to enlarge to fit.

Raj

At 28-02-2018, you wrote:
Hi, I am getting a buzzing coming through the speaker on my bitx40. Oddly this seems to quieten or completely disappear when I wriggle the power in the back of the case?? Could this be ground related? I cant see anything obvious...

Regards Carl.