Date   
Re: Narrow filter for CW #ubitxcw

_Dave_ K0MBT
 

Yes I was hoping to steal someones design and spend less than 10 dollars.

Have to agree that adding a 300 dollar filter to a radio that I bought used for 45 dollars is not going to happen.

Re: Narrow filter for CW #ubitxcw

Gordon Gibby <ggibby@...>
 

You can put in an op amp analog filter for very small outlay of cash.
I can remember building my first audio filter in the dark ages around 1973. Used toroids probably surplus from the phone company to build filters, and vacuum tubes to amplify the audio signals. Worked pretty good!!! Far far easier today.

Gordon

________________________________________
From: BITX20@groups.io <BITX20@groups.io> on behalf of _Dave_ K0MBT <davesters@...>
Sent: Friday, August 16, 2019 7:08 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Narrow filter for CW #ubitxcw

Yes I was hoping to steal someones design and spend less than 10 dollars.

Have to agree that adding a 300 dollar filter to a radio that I bought used for 45 dollars is not going to happen.

Re: Narrow filter for CW #ubitxcw

Tom, wb6b
 

On Fri, Aug 16, 2019 at 04:13 AM, Gordon Gibby wrote:
Used toroids probably surplus from the phone company
Yes, those were popular back in the day for home-brew projects. Many folks built RTTY demodulators with them.

Tom, wb6b

Re: Narrow filter for CW #ubitxcw

Dale Hardin
 

But, where will you mount the transceiver on the filter board?

Carrier suppression on uBITX v5 - -35 to -40 dB ok?

Rob French (KC4UPR)
 

For USB/LSB on the uBITX, what is a reasonable carrier suppression?  (and how is that properly measured, i.e. I assume it's carrier relative to peak?)

Background:  I should have left well enough alone, but... I've been using my uBITX for FT8 and PSK31, and had directly connected my uBITX mic input to my USB soundcard's headphone output, and my uBITX speaker output to my USB soundcard's mic input.  No special adapter circuits or anything.  Worked fine, bunch of good QSOs.  Fast forward, I was reading about interface circuits, and saw someone said that I MUST put a blocking capacitor between the respective inputs/outputs.  Well, I didn't do that.  Also read about someone saying that a few volts into the mic input could kill diodes in the balanced modulator, leading to carrier leak through.  So then I got paranoid and figured I should check my signal to make sure I hadn't done something like that.  Which brings us to now...

Test Setup:  uBITX v5 transmitting into a dummy load.  RTL-SDR dongle plugged into my PC, operating in direct mode.  "Tone generator": me whistling into the mic.  GQRX running on my PC to view the spectrum.  Just eyeballing the spectrum display.

Results:

(1) with background noise only ... noise floor ~ -75 to -80 dB on GQRX readout.  With PTT on, no tone, desired sideband ~ -75 to -70 db, carrier ~ -75 to -70 db (visibly distinct from desired sideband), opposite sideband absent.

(2) with a tone ... noise floor ~ -75 to -80 dB on GQRX readout.  With PTT on, "whistle" tone, desired sideband ~ -35 dB (peak), carrier seems to be unchanged (-70 to -75 or so), opposite sideband still absent (carrier kind of gets lost in the spectrum from my "whistle" at this point, but as I increase the volume from nothing, the carrier appears to be staying the same).

Does this all seem reasonable?  

Thanks!
-Rob

(PS - As an aside, I checked the DC bias on the USB sound card mic in and headphone out... mic in ~ 2V, which I assume it to drive electrets, and headphone out is 0V)

Re: Narrow filter for CW #ubitxcw

Gordon Gibby <ggibby@...>
 

Too funny!


On Aug 16, 2019, at 09:10, Dale Hardin <joe.dale.hardin@...> wrote:

But, where will you mount the transceiver on the filter board?

Re: V5.1 and Nextion 5”

Joe Puma
 

Looks good 

Joe
KD2NFC 


On Aug 16, 2019, at 5:22 AM, Murray Wills (ZL2IQ) <murray@...> wrote:

<Image-30.png>
<Image-29.png>
Hi everyone

Installed a separate PS and updated the display software. Very pleased with the results.

I also have a higher output regulator coming so the step down PS is only temporary. That board will be useful for other projects.

Thanks for all the help

73. Murray ZL2IQ




On Tue, Aug 6, 2019 at 11:11 AM +1200, "David Posthuma" <davep@...> wrote:

I used a 4.3-inch Nextion screen with no problems.

David Posthuma
WD8PUO

 

From: bitx20@groups.io on behalf of Murray Wills (ZL2IQ) <murray@...>
Sent: Monday, August 5, 2019 6:27 PM
To: bitx20@groups.io
Subject: Re: [BITX20] V5.1 and Nextion 5”
 

Thank you Evan for the time you have taken to help me out.

73 Murray ZL2IQ

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Evan Hand
Sent: Monday, 5 August 2019 11:11 PM
To: BITX20@groups.io
Subject: Re: [BITX20] V5.1 and Nextion 5”

 

Murray,

What Mike is saying is that the 5" screen may be too much for the 7805 5 volt regulator in the Raduino that comes with the uBitx.  There are a number of options, everything from modifying the Raduino regulator circuit, to simply adding another 7805 5 volt dc regulator. 

Background:
The 13.8 volt power supply is much more than the uBitx needs.  The 13.8 volts is good for the finals, however the rest of the board prefers the specified 12 volts.  That is why there are two power connections on the uBitx board.  The 7805 5 volt regulator on the Raduino runs off of the uBitx board supply, not the finals supply.  As currently connected it needs to drop that 13.8 volts to 5 volts.  The difference is dissipated as heat by the regulator.  The amount of heat  depends on the current draw through it. The recommended power supply for the display by Nextion is 5 volts at 1 amp.  Much more than the stock Raduino setup can provide.  

Here is the Nextion spec sheet:
https://nextion.itead.cc/datasheets/nx8048k050/ 

Suggestion:
Based on the current requirements I would suggest that you add another, separate 5 volt power for the Nextion display. This can be based on a 7806 type of regulator like one that is in the Raduino, however it will need a dropping resistor, heat sink, and the appropriate filter capacitors to work.  Another option is to by an assembled 12 volt to 5 volt reducer.  The watch out here is that it could generate noise as most are pulsed based circuits.

Here is an example datasheet for the 7805.
  https://www.sparkfun.com/datasheets/Components/LM7805.pdf

See figure 1 on page 7.  It gives typical input and output capacitor values, though does not cover a dropping resistor. 

Since the input is relatively high compared to the minimum required, and the power dissipation is dependent on the voltage drop times the current (nominal 13.8 - 5 = 8.8 volts times the max current of 1 amp = 8.8 watts).  Much higher than the design dissipation even with a heat sink.  Adding a voltage dropping resistor to get the dissipation lower is suggested.  The minimum specified input voltage is 7 volts.  I would use 8 volts to account for any variations in the input supply.  That means we need to drop the 13.8 volts to 8 volts with a resistor at the current draw of the specified 1 amp.  For this I would use a 4 or 5 ohm power resistor rated for 4 or 5 watts respectively.  Since this is the DC part of the radio, wire wound works well. The actual value of resistor would be 5.8 ohms and 6 watts.  You can go lower in value, just means more heat to be dissipated by the regulator, but do not go higher as at some point the input voltage may drop below minimum.

You will need to add a heat sink on the regulator.  This can be the case if it is aluminum, and you install the appropriate insulators for the mounting.  I would go with a separate heat sink similar to the one on the finals.

Another suggestion is to put a voltage drop between the 13.8 volt supply and the uBitx board.  This involves separating the red and brown power supply wires (per the supplied connector).   To that end I would recommend adding 2 4n4000 series diodes to drop the 13.8 volts to 12 volts to the RED wire.  4n4000 series diodes are rated for only 1 amp, so you will need to separate the finals supply and connect it directly to the 13.8 volt source.  If you do this modification as well, will need to go back and recalculate the voltage and resistor values for the Nextion display above.  I am using a 4 ohm 4 watt resistor in my setup, with the diodes to drop the voltage to the main uBitx board.

Please take the above with a grain of salt.  There may be errors, so verify.

Good luck with the build.

73
Evan
AC9TU

Re: another stuck relay in TX mode #ubitx #bitx20

 

Thanks Peter!

Beside all the TX circuitry, the relay is also driving two other relay coils, so I wonder if that may cause a bit of stress too?  Initial resistance of the relay coils in parallel might be pretty low.

I don't know the draw of the TX (not counting the finals on a separate circuit) but I don't think it woul be close to 2A?  So looking at sequencing, or just a beefier relay may be the long term answer.

73,


Mark

PS:  I suspect the 28W may be due to Don running the finals at more than 12V?

Re: Narrow filter for CW #ubitxcw

Vince Vielhaber
 

I did the same thing in the late 70s with a fone company toroid and a cap. Made for one sharp CW filter. I just recently removed it from my 75A-4 receiver, didn't work that well anymore, the cap was all dried out and I don't do enough CW to need it.

Vince - K8ZW.

On 08/16/2019 07:13 AM, Gordon Gibby wrote:
You can put in an op amp analog filter for very small outlay of cash.
I can remember building my first audio filter in the dark ages around 1973. Used toroids probably surplus from the phone company to build filters, and vacuum tubes to amplify the audio signals. Worked pretty good!!! Far far easier today.

Gordon

________________________________________
From: BITX20@groups.io <BITX20@groups.io> on behalf of _Dave_ K0MBT <davesters@...>
Sent: Friday, August 16, 2019 7:08 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Narrow filter for CW #ubitxcw

Yes I was hoping to steal someones design and spend less than 10 dollars.

Have to agree that adding a 300 dollar filter to a radio that I bought used for 45 dollars is not going to happen.




Re: Narrow filter for CW #ubitxcw

Dale Hardin
 

For those who don't get the joke...

On Fri, Aug 16, 2019 at 8:48 AM Gordon Gibby <ggibby@...> wrote:
Too funny!


On Aug 16, 2019, at 09:10, Dale Hardin <joe.dale.hardin@...> wrote:

But, where will you mount the transceiver on the filter board?



--
Dale Hardin
24750 State St. Unit 487
Elberta, AL 36530
251-597-9256

--
Dale Hardin, KS4NS
Elberta, AL

Re: Narrow filter for CW #ubitxcw

MVS Sarma
 

Why not use max7400 as a n lpf. It is a nice 8 pin dip and/or smď
Spend a while to study the datasheet. It can become variable lpf.

On Fri, 16 Aug 2019, 4:38 pm _Dave_ K0MBT, <davesters@...> wrote:
Yes I was hoping to steal someones design and spend less than 10 dollars.

Have to agree  that adding a 300 dollar filter to a radio that I bought used for 45 dollars is not going to happen.



Re: Narrow filter for CW #ubitxcw

MVS Sarma
 

My reply is for limited use at audio level. Sorry. May not be relavent. 


On Fri, 16 Aug 2019, 9:11 pm Mvs Sarma, <mvssarma@...> wrote:
Why not use max7400 as a n lpf. It is a nice 8 pin dip and/or smď
Spend a while to study the datasheet. It can become variable lpf.

On Fri, 16 Aug 2019, 4:38 pm _Dave_ K0MBT, <davesters@...> wrote:
Yes I was hoping to steal someones design and spend less than 10 dollars.

Have to agree  that adding a 300 dollar filter to a radio that I bought used for 45 dollars is not going to happen.



Re: V5.1 and Nextion 5”

Mark Hatch
 

Fantastic! Glad to see another 5" out there.
73
Mark
AJ6CU

Re: Narrow filter for CW #ubitxcw

Frank Dinger , EI7KS
 

Regarding a CW filter , a simple audio filter with 2 or 3 Amps from a Quad-opamp might be a simple start for good CW listening. There are many circuits on the Web.

Frank    ,    EI7KS

ubitx s-meter swr-meter help #bitx20 #bitx40 #bitx40help #arduino #calibration

circular.simetry@...
 

Hello i am using the 1.80 firmware from KD8CEC on my ubitx with a 2X16 lcd display  and i have noticed the s-meter bargraph  is working only in Rx mode, but when i switch to TX gets stuck with the last value . I want to use the bargraph while transmit to measure the power or the swr. i think  the display update is disabled while tx in the source code. any help wil be appreciated, thanks in advance 73! YO4HUJ Adrian.

Re: Calibration success #ubitx #calibration

Dean Souleles
 

Thank you Leonard. This particular mic doesn’t have a preamp....so no chance of over driving.

Dean

Re: Carrier suppression on uBITX v5 - -35 to -40 dB ok?

Tom, wb6b
 

Hi,

I just double checked the schematic. It looks like there is adequate DC blocking capacitors in the mike input circuit. Also, the mike input already has a DC voltage applied to power the microphone. So, unless the sound card doesn't like the DC voltages and causes distortion, it is likely not the source of the carrier leakage.

I'm not sure how much is good or bad, but the topic of carrier suppression and fixes has come up on this group. Hopefully, other may be able to shed more light on what level is acceptable.

I have had good success with connecting the high side of the volume control directly to the microphone input of a USB sound dongle. And the headphone output of the USB sound dongle directly to the microphone input of the uBitx. Some sound adaptors may work better or worse in this configuration, but the generic adaptor used seems fine in this arrangement. It is possible some sound adaptors might not like the DC voltage (but low current) the uBitx puts on the microphone input applied to the headphone output.

Tom, wb6b

Re: Carrier suppression on uBITX v5 - -35 to -40 dB ok?

Ashhar Farhan
 

The carrier to signal ratio needs to define the signal level as well. A 'Haaalllowww' is usually insufficient (though I use it all the time).
You could download a wav file of two tone and play that into the mic. That is the simpler way to do it properly.

- f

On Sat 17 Aug, 2019, 1:34 PM Tom, wb6b, <wb6b@...> wrote:
Hi,

I just double checked the schematic. It looks like there is adequate DC blocking capacitors in the mike input circuit. Also, the mike input already has a DC voltage applied to power the microphone. So, unless the sound card doesn't like the DC voltages and causes distortion, it is likely not the source of the carrier leakage.

I'm not sure how much is good or bad, but the topic of carrier suppression and fixes has come up on this group. Hopefully, other may be able to shed more light on what level is acceptable.

I have had good success with connecting the high side of the volume control directly to the microphone input of a USB sound dongle. And the headphone output of the USB sound dongle directly to the microphone input of the uBitx. Some sound adaptors may work better or worse in this configuration, but the generic adaptor used seems fine in this arrangement. It is possible some sound adaptors might not like the DC voltage (but low current) the uBitx puts on the microphone input applied to the headphone output.

Tom, wb6b

Re: Carrier suppression on uBITX v5 - -35 to -40 dB ok?

Gordon Gibby <ggibby@...>
 

​A significant number of sound interface systems will have a TRANSFORMER here and there.   It is important in most cases to provide DC isolation to prevent the transformer from dramatically changing the biasing conditions of the mic input amplifier of the radio to which it is connecgted.   This blindsided me once when I connected a homebrew isolator (with transformers) to an icom 2 meter rig to do packet -- and the signals sounded horrible.   You won't damage the transformer, but you can throw the linearity of the mic-amp stage out the window.   A Signalink in the same situation did FINE -- because it had capacitor dc-isolation.   I learned the hard way to DC isolate.


Cheers,

Gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of Tom, wb6b <wb6b@...>
Sent: Saturday, August 17, 2019 4:04 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Carrier suppression on uBITX v5 - -35 to -40 dB ok?
 
Hi,

I just double checked the schematic. It looks like there is adequate DC blocking capacitors in the mike input circuit. Also, the mike input already has a DC voltage applied to power the microphone. So, unless the sound card doesn't like the DC voltages and causes distortion, it is likely not the source of the carrier leakage.

I'm not sure how much is good or bad, but the topic of carrier suppression and fixes has come up on this group. Hopefully, other may be able to shed more light on what level is acceptable.

I have had good success with connecting the high side of the volume control directly to the microphone input of a USB sound dongle. And the headphone output of the USB sound dongle directly to the microphone input of the uBitx. Some sound adaptors may work better or worse in this configuration, but the generic adaptor used seems fine in this arrangement. It is possible some sound adaptors might not like the DC voltage (but low current) the uBitx puts on the microphone input applied to the headphone output.

Tom, wb6b

Re: another stuck relay in TX mode #ubitx #bitx20

_Dave_ K0MBT
 

I have 4 uBITX radios and the first one had stuck the left side relay early on. I replaced it with a stock component and it has worked fine. None of the other machines has had a problem. This relay only carries signals on the receive side so no chance of spurious emissions.

Good luck with your repair.

I approach repairs from the viewpoint of a repair technician rather than that of an engineer. I always get a chuckle with those who think they need a wall full of test equipment to fix these critters So far I have been able to resurrect all 3 uBITX radios determined to be junk by previous owners.
73 all
Dave