Date   
Re: Tracing receive signal for low signal

Dave Space
 


I am going to declare the audio pre-amp a success.  To compare I generated a signal off my signal generator into the air  (no direct connection) and listened for the lowest level I could hear it on my Yaesu which was 20mv out on my generator as barely audible and 40mv audible.  I then connected the ubitx to the same antenna and tested and it is now on par with the Yaesu in terms of at least level of hearing a faint signal and pretty close on a strong signal. (it might even be slightly better on the uBitx now)

Thanks everyone especially Evan and Jim for all of the ideas to get to there.  I do kind of wish we figured out why the board is anemic but I'm good with taking a win :)

I'm trying to decide if I want to tackle the transmit issue (I think I heard it transmit off frequency slightly like 3khz low or something) next or try to add an AGC. (I'm thinking worst case if I can ever get software to load on the Radiuno I can rewrite the software to transmit at a slightly off frequency to compensate for the transmit problem - My day job is in the software development area :) )

Re: uBix - transmit clicking when Mic inserted

Gary Anderson
 

From the HF signals schematic and wire-up diagram (original V3 sourced in ~Feb/March 2018), it doesn't look like the designer anticipated that the Mic/PTT plug would be plugged-in after uBITX power-up.
I think this is where Raj is going when he suggests swapping PTT and Mic wires (on both the uBITX and your mic)

The original supplied V3 wire-up has:
Tip = "Mic" = 4.7K ohm resistor to TX (12V when in TX mode)
Ring = PTT = internal Nano pull-up to 5V
Sleeve = GND

When you plug in a TRS plug to the jack supplied in the kit, the Sleeve to Ring (jack side) can easily short if it is off on angle.
The internal springs in the jack help get the plug off angle  (at least on mine)
A short between PTT and GND puts the uBITX in TX mode.

As you continue to push in the plug, you short Tip to Ring on the jack. (You can see this through the clear plastic window on the jack)
For a brief moment if your uBITX went into TX mode, a second operating condition fault scenario:  4.7K Ohm pull-up to 12V on the Nano. 
Now you are depending on the ESD protection diodes internally to the Nano to protect from Electrical Over Stress.

Swapping Mic and PTT positions would seem to be more robust (I have not fully vetted this solution.)
You would still have the above Tip to Ring fault mode if you accidentally unplugged the while the uBITX was in TX mode.
(so not 100% robust, but that is much less likely to happen often enough to be of much concern, and if the Nano goes 'bad'; you have a clue)

Regards,
Gary




Re: Tracing receive signal for low signal

Evan Hand
 

You are welcome, though it the transmitter is off by 3khz, that is an indication that the calibration is off, and the 3khz off would put it outside of the 2.5khz bandpass for the 12mhz filter.  I would start with calibrating the VFO (clock#2) to be on freq. with CW key.  Then go back and verify the BFO.

Off calibarion is a know issue with the uBitx v4. When not calibrated, the sensitivity is very low.  Get it calibrated, and the receiver is as sensitive as most 10x the cost commercial rigs (that is the case with my v4 uBitix compared to my Icom IC-7300).  The Icom has more features to help with selectivity (and a host of others), however it is not much better at pure sensitivity of the signal over the noise floor.

73
Evan
AC9TU

Re: Tracing receive signal for low signal

Dave Space
 

Thanks again.  Question wouldn't calibration impact both receive and transmit?  In this case receive seems spot (same frequency matches on Yaesu and ubitx and can zero beat on tone) on but I think transmit was off.  BFO frequency seemed good on receive.  I'll need to retest to be sure. 

uBitx worked, shut off, now no audio

Nick
 

Hello, all!

I finished the assembly of my uBitx and case. I turned it on and it seemed to be working. I did not have an antenna attached so was only hearing noise, but It would only stay on for about ten seconds before it would shut off. This happened several times; I thought it might have been because I had no microphone or key attached. Once, as I was adjusting the tuner, the unit shut itself off but this time when I cycled the power and turned it back on, the audio was completely gone. I have checked for loose connections but can't find anything wrong. It appears to power up fine, the tuner and menu functions are working, the only problem is zero audio on both the speaker and the headphone. Interestingly, now that I have no audio the radio is not shutting of anymore.

I'm hoping someone will have some insight as to why the unit shut off repeatedly and now stays on but is is deaf. Any help will be appreciated!!!

Nick
W3VN

Re: #bitx40 BITX40 Winlink configuration #bitx40

rick
 

I'm attempting the same thing.  Would be grateful if you'd elaborate on the signal conditioning circuit.
Thanks!

rick

Re: si5351 crosstalk #radiuno

Glenn
 

This is a fairly old thread but I recently did some testing on my own version Si5351 board with buffer chips on each output, which maybe of interest.   I only tested 2 outputs, 0 and 2, for cross-talk as I had a VFO/BFO Raduino style board set-up to test. Frequencies of ~10.7MHz and 17.8MHz so can only comment on this setup. There maybe differences at other frequencies etc.

My Si5351 PCB is based on the Adafruit style and Sch with same pin-out, and the comparison was between the Adafruit and my buffered version. The buffered outputs were fed thru a 47R resistor and 100nF cap to the SA in the buffered board.  And only via a 100nF cap in the Adafruit version. ie Raduino style. Each of the 74LVC1G04GW buffer chips was supplied with Vcc via it's own ferrite bead and 100nF cap to ground, filter. (not visible, as on bottom of the PCB)

Typical cross-talk of the Adafruit board was around -50dB from output 0 to 2 or output 2 to 0. Output levels into the SA at fundamental, approx. +4dBm.

My buffered version was better by around 8-10dB for cross-talk and output at fundamental increased to approx. +8-9dBm.

Glenn vk3pe




On Sat, Sep 22, 2018 at 07:43 PM, <lynatmts@...> wrote:
Hey Glenn, So what were the results of adding the buffer stages? 
Thanks

Lyn
--
"You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat."

Re: Mini PA für my uBITX #ubitx

DC3MS
 

Bob, i deeply respect long time hams sharing their vast knowledge with new-to-ham Operators,
but i really didnt expect this discussion to start.
Sure its not necessary, nor is it necessary that i recap an Heathkit SB101, SB610, SB620 and build
an extra Hamdesk in the basement to set the line up together with the just acquired SB200.
If i would do my antenna and CW work right, all i needed would be pixie monobanders for each band.
I am not complaining about objections regarding signal quality - i think that is pretty important.

Re: Mini PA für my uBITX #ubitx

Bob Lunsford <nocrud222@...>
 

Mark, I'm in the process of getting a BITX40 (waiting for
shipping notification and tracking number) and those
old Heathkit days are moving into hazy history and a
desire to never revisit them. The only thing I have now
is an HW-2036 2M for monitoring 52S mostly and a
RS HTX-252. I live in a 2M depressed area.

I've build nearly everything Heath had. Had an HW-104
and an SB-104 but the FT-450AT I had made them look
like WW1 submarines. I even had a Drake TR7 which
was to me the Cadillac of HF radios but the 450 was
much better for me. All that is gone now. Moving into
the HF Signals arena.

These Ubitx/TITX40 radios are great. It's a new kind
of technology to me with the Raduino. The UbitX is
surprisingly good on reception and this means from
500KHz to 30MHz.

Big question is, when will the V5 board be available?

Bob — KK5R

--------------------------------------------

On Mon, 1/14/19, DC3MS <mark.schraven@...> wrote:

Subject: Re: [BITX20] Mini PA für my uBITX #ubitx
To: BITX20@groups.io
Date: Monday, January 14, 2019, 1:23 AM

Bob,
i deeply respect long time hams sharing their vast knowledge
with new-to-ham Operators,
but i really
didnt expect this discussion to start.
Sure
its not necessary,
nor is it necessary
that i recap an Heathkit SB101, SB610, SB620 and build
an extra Hamdesk in the basement to set the
line up together with the just acquired SB200.
If i would do my antenna and CW work right, all
i needed would be pixie monobanders for each band.
I am not complaining about objections regarding
signal quality - i think that is pretty
important.

Re: ND6T AGC Troubleshooting

DJ2AG
 

Hi Rich,

thanks for the diagram. Will give it at try.

Armin, DJ2AG

Re: Mini PA für my uBITX #ubitx

DC3MS
 

See - thats what i really like ham radio for. There is no technical or practical reason to spend month on getting the 50 years old HK equipment back in shape - except me finding it fascinating.

I could buy some up to date transceiver for the Money (or even half of it) , but thats just not my kind of fun. I always wanted a Heathkit. Even if its only because of its looks :) 

I also like the uBitx because of the Arduino, which is something i use on a regular basis. 

Just wanted to use a Nano to control a linear and try the i2c connection and a nextion.

No show-off. No really need. But i for sure see a difference in range on 40/80m running FT8 on my homemade HF2V vertical. And it was fun to put together.

Re: Tracing receive signal for low signal

Evan Hand
 

As I understand it, the VFO is not changed UNLESS you have the RIT set.  I should have asked you to verify that first.

73
Evan
AC9TU

Re: uBitx worked, shut off, now no audio

Vic WA4THR
 

Which version of the uBitX? If it is a v.3 board most likely the audio amplifier chip (begins with WX) has failed, a common issue. If it is a late version of that board the chip will be in a socket and easily replaced with a better one.

=Vic=

QCX

Dave Dixon
 

LOKKING FOR A QCX TRANSCEIVER.
band not important.
must be in the uk...

Re: uBix - transmit clicking when Mic inserted

_Dave_ K0MBT
 

What is happening on my radio is that the tip shorts between the ground and the ptt as it slides in. Keying ptt. It shouldn't be putting out much power as the mic is not active until the last terminal is reached and engaged.

I try to not insert mic on running radio.

Re: Ubitx v4 whining and swr check issue(?)

John (vk2eta)
 

The uBitx does transmit out of ham bands but the change of filters is set in relation to ham band edges.

Example for 40m, the 7-10Mhz  filter is switched ON when the frequency is set above 7,000,000Hz.
At or below that value the 3.5-5Mhz filter is ON. Therefore the available power at the antenna connection below 7,000,000Hz will be significantly reduced.

Although it is possible that an issue exist in the 7-10Mhz filter I suspect more likely an issue with the antenna.

Do you have or can you make a dummy load (example 20 x 1k ohms 1/4 watt resistors in parallel would give 50 ohms at 5 watts dissipation, usable with short burst of CW power to test the swr and confirm a very low swr on the 40m band)?

Regarding the whining, based on your "touch" test on the 25mhz crystal I strongly suspect a Nano oscillator issue. Changing the Nano fixed that issue in my rig.

73, John

Re: uBix - transmit clicking when Mic inserted

Bill Cromwell <wrcromwell@...>
 

Hi,

I don't plug-in or unlug anything wit the radio powered. Notthe uBitx. Not the PFR-3, not the Johnson Ranger, not the SW-3 (1933 vintage). Most of the time it's okay but can cause real fireworks. It's a habit that is good to promote.

73,

Bill KU8H

On 1/14/19 7:49 AM, d balfour wrote:
What is happening on my radio is that the tip shorts between the ground and the ptt as it slides in. Keying ptt. It shouldn't be putting out much power as the mic is not active until the last terminal is reached and engaged.
I try to not insert mic on running radio.
--
bark less - wag more

Error in Ubitx Mic Amp circuit?

Uwe , DF1UB
 

Hi,

is there an error in the circuit of the mic amp or just the wrong Cap build in?

the cap C63 at the collector of Q6 should be 1µ polarized, but on the board is a ceramic C.Is this the fault of low mic signal?

Blown finals?

Peter Russell <peter.russell@...>
 

It's now about a month since I got my ubitx and I haven't tried to transmit as my power supply wasn't up to it.
So I built a new (5A) one.
Powered with the new PSU, I wound the bias controls fully clockwise and with my meter checking the current, pressed the key. Turning RV2 produced the expected current increase, but turning RV3, no increase at all!
Must have somehow blown one of the finals!
So I ordered 3 new IRF510's.
I changed the one I thought was at fault and tried again.
Same problem.
Must have changed the wrong one!
Changed the other one.
Same problem.
After a good deal of bad language I got round to checking voltages and resistances around the final circuits, where I realised that one of the bias circuits was behaving very strangely.
To cut a long story short, I removed RV3 from the board only to find that it had broken one of its legs and was hanging only on two ( the ground one had snapped off!).
So I've ordered some presets.
Maybe it's all those tales of woe about IRF510's that I've read on this forum that made me think that one had blown, or maybe I should have done what I was taught and followed correct fault finding procedure before jumping in with both feet.
The presets should be here tomorrow so I'll do a proper repair job and hopefully learn a useful lesson.
DON'T TAKE TOO MUCH NOTICE OF FORUMS!

Peter G8FWY

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Re: Blown finals?

SAM R BURNES
 

Good job on the “learning experience” description.

Thank you for sharing.

73,
Sam
WY8V

On Jan 14, 2019, at 3:46 PM, Peter Russell <peter.russell@...> wrote:

It's now about a month since I got my ubitx and I haven't tried to transmit as my power supply wasn't up to it.
So I built a new (5A) one.
Powered with the new PSU, I wound the bias controls fully clockwise and with my meter checking the current, pressed the key. Turning RV2 produced the expected current increase, but turning RV3, no increase at all!
Must have somehow blown one of the finals!
So I ordered 3 new IRF510's.
I changed the one I thought was at fault and tried again.
Same problem.
Must have changed the wrong one!
Changed the other one.
Same problem.
After a good deal of bad language I got round to checking voltages and resistances around the final circuits, where I realised that one of the bias circuits was behaving very strangely.
To cut a long story short, I removed RV3 from the board only to find that it had broken one of its legs and was hanging only on two ( the ground one had snapped off!).
So I've ordered some presets.
Maybe it's all those tales of woe about IRF510's that I've read on this forum that made me think that one had blown, or maybe I should have done what I was taught and followed correct fault finding procedure before jumping in with both feet.
The presets should be here tomorrow so I'll do a proper repair job and hopefully learn a useful lesson.
DON'T TAKE TOO MUCH NOTICE OF FORUMS!

Peter G8FWY

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