Date   
Results of MAX9814 in uBitx #ubitx

John <passionfruit88@...>
 

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: I got my uBITX ... adventurous shipment !

William R Maxwell
 

hey Mike, don't take it out on the poor old Volvo. If it happens to be a 240 series, it has the best 4 cylinder engine ever built. Dump your old Abba records, rollmops, Bofors gun or similar, instead!

Bill,VK7MX


On 27/02/2018 10:09 AM, Michael Hagen wrote:

Dirty Rotten Bureaucrats!

I am for sure going to Dump my Volvo!

Fearing the VAT Tax here some day!

.... ..   .... ..

73's

Mike, WA6ISP



On 2/26/2018 2:41 PM, Mikael wrote:

Santa came early this year. 

Finally got the package with my uBITX today. (Ordered Dec 21st)

Well... Now the fun Begins! Case and all other parts arrived weeks ago. 

Forecast says snow and Cold weather for the weekend so excellent for Indoor radio assembly

 

My uBITX got held back in Swedish customs for a few Days and they  slammed me with 25% VAT plus handling fee which added up to about 42USD

Cheap China packages is history for us in Sweden now since postal office is introducing a handling fee of 9USD + 25%VATon declared value

on ALL packages from 1st March regradless of value.

If I order something small for 2USD free shipping from Aliexpress now - I will pay Ali 2USD and then 9,5USD in VAT plus handling fee to get the package out in Sweden.

Been known for some weeks now but will be hundreds of thousand packages already on the way that people never will pick up now with the new fees

 

Regards

Mikael


-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

Re: Kd8CEC: where is key type?

Carlos E. Wenzel
 

Thanks for your support.....
73's Carlos Ik2yra 

Il 28 feb 2018 03:05, "Ian Lee" <kd8cec@...> ha scritto:
I saw the mail late because my long vacation was over.
In this semester, I would like to introduce uBITX to students.
so, I am busy making uBITX lecture materials before the new semester starts.

You can read How to CEC Firmware and various videos in my blog.

I found some things I recently uploaded and I linked them below.

About General features
http://www.hamskey.com/2018/02/cat-support-ubitx-firmware-cec-version.html

You will also find some resources on the AutoKey (builtin s / w memory keyer), uBITX Manager and more.

Thank you for using my firmware.

Ian KD8CEC


2018-02-28 2:58 GMT+09:00 DrZ <zehrhj2@...>:
Found it in setup.
Howard



--
Best 73
KD8CEC / Ph.D ian lee
kd8cec@...
www.hamskey.com (my blog)

troubleshooting no TX SSB #ubitx #ubitx-help

John
 

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?

John

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

Lawrence Galea
 

Mono plug on headphones?

On Wed, Feb 28, 2018 at 9:37 AM, John <jjczon@...> 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?

John


Audio buzz

Jodannastreet1985@...
 

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 can’t see anything obvious... 

Regards Carl.

Re: Audio buzz

MVS Sarma
 

Rdeduce the value of100 ohms battery feed to lm386 to say 20 or 10 ohms. Just get a 12 ohm and place above 100 ohm and solder.

On 28 Feb 2018 14:30, <M0clscarl@...> 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 can’t see anything obvious... 

Regards Carl.

Re: ergonomic design of front panel

Vic WA4THR
 

I put my display on the right primarily to avoid blocking the USB port on the Raduino with another control. I can quickly lift the lid on my BitX40 and plug in to adjust the sketch without having to move any components, and I have not had any issue with a hand blocking the display while I am tuning.

=Vic=
WA4THR

Re: Schematic Drawing Software

 

Mr. Farhan, 

Kicad seems to have become somewhat easier to tackle from the last time I fought with it. Last time was on Linux, this time on Mac....sure seems to be easier to work with, looks like I will be able to print a solder paste stencil after manipulating the Gerbers from the improved Antenna Analyzer big green board.  Thanks for the nudge, looks like I will be able to work with this.

And if another major upgrade is coming....glad I made the jump. 

My Builders Group will be creating a number of their own mods and we will give Kicad a spin.

Craig
KM4YEC

Better Schematic

Walter
 

Where can I download a better Schematic of the UBITX?  I cannot read the one off the website the resolution is low.

I need the resistor values for R63 and R60.  I did the dynamic mic mod and may have to replace these resistors if I cannot get my dynamic mic to work with the UBITX.  I need these values to order some SMD's

Does anyone know where to buy a package of SMD resistors with many different values?

Thanks for your help
--
73, W9KJO
Walter

U1 fried

K4LXY
 

Last night while trying various speakers, smoke started rolling out of my uBitx.  The audio IC U1 was fried.  I'm assuming the audio line shorted while inserting plugs.  They are cheap (5 for $6) and I'll install a socket for easy replacement.  But a word of warning.....
Howard K4LXY

Re: U1 fried

Walter
 

On Wed, Feb 28, 2018 at 04:08 am, DrZ wrote:
Last night while trying various speakers, smoke started rolling out of my uBitx.  The audio IC U1 was fried.  I'm assuming the audio line shorted while inserting plugs.  They are cheap (5 for $6) and I'll install a socket for easy replacement.  But a word of warning.....
Howard K4LXY
i Noticed the volume switch has an on/off switch built into it.  perhaps I will connect this in line with the speaker jack and turn it off before plugging and unpluggings speakers and stuff.
 
--
73, W9KJO
Walter

UBitx no audio! Could use some advise

Brett Deschene
 

Hi everyone.
I recently received the ubitx and have wired it up but am not getting any audio signal.
When I initially wired it up I accidentally had the PTT shorted to ground causing it to go into TX immediately. I disconnected the power, rewired the jack and continued.
Powers up fine
All functions appear to work (except audio)
Rotary encoder tunes up and down the bands and goes through the menus a like a hot knife through butter.
Screen says that it Goes into TX when PTT is engaged or when Keying begins.
During receive everything appears fine but no audio
Speaker and headphones are tested and work.
Audio Jack is correctly wired and works.
Potentiometer is wired correctly, tested and works.
Antenna works and brings in a signal just fine on other radios.
Antenna jack is wired correctly and connected to the board.
I am tuned to a frequency where I know my antenna is receiving signals heard on other radios.

Audio is completely nonexistent. No sidetone heard from CW, no static, hissing, popping, nothing.
I am pretty sure the issue is something simple and located on the board somehow but even with the schematic of the received audio path I just do not know how to diagnose and am not sure where on the board to take readings. Any help would be much appreciated.

-Brett Deschene

Speaker Jack

Walter
 

If I use the Speaker jack with headphones, then I naturally have to turn the audio down very low.  However, if doing digital modes then the audio is too low for the signal link. 

What would I need to do to install a second jack for headphones and lower the audio for headphones while leaving the speaker volume up higher? 

Would a simple resistor work or is more required for such a modification?

Is there a place to tap into a constant audio level that is not affected by the volume control?  Kind of like a line level output?

Thanks for your help.
--
73, W9KJO
Walter

Low level hum in headphones on UBITX

Walter
 

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: BITX40 carrier and low output

Allard PE1NWL
 

Have you already aligned the PA BIAS and PA DRIVE according to the instructions on hfsignals.com?

  1. Attach a dummy load to the antenna
  2. Insert a ammeter (you may use your VOM meter in high amps range) into the PA power supply’s positive line
  3. Keep the PA BIAS preset (RV1) to fully clockwise position. Now when you press the PTT button, the ammeter should read about zero.
  4. Increase PA BIAS without speaking into the mic until the PA current shows 100 ma
  5. Give a loud and long HAAAALLLOOWW into the mic and the current should jump to slightly over 1 amp
  6. Adjust the RV136 to increase the PA drive if the current doesn’t jump all the way to 1A
  7. Keep monitoring your signal on a nearby receiver.

73 Allard PE1NWL

Another shipping Notification Update

KC4VZT Middleburg, FL
 

Well, I just got a paypal notice that the tracking of my uBitx as been issued. I ordered my uBitx on Jan 2 and today is Feb 28. So soon I'll have the uBitx in hand, not sure when I'll get a chance to build it up but hopefully it will be soon.

-Obe (KC4VZT)
Middleburg, FL

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.

Re: Another shipping Notification Update

Daniel Conklin
 

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

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