Date   
Re: Mode Changes

Reed N
 

R1.1.2 sounds like you might have my software, not the KD8CEC software.

The side band buttons don't turn off in my build because in CW mode, when receiving, the radio shifts up or down from the displayed frequency. The direction of the receive shift is determined by the side band selection, and the magnitude is determined by the selected CW tone frequency in the settings menu.


Reed

Mode Changes

Bill Robbins
 

I have the V6 with the KD8CEC firmware, R1.12.  When changing modes the USB or LSB buttons never turn off when choosing CW.

Can someone refer to a post or revision change that I have missed?

Thanks

Bill
WA8CDU

Re: automatic side band switch.

Richard
 

The problem is that I can NOT manually select my sideband. Listening to a station on LSB and then switching to USB makes no difference in the audio as it should.

Re: Only noise when connected to the antenna #v6

Tom, wb6b
 

On Mon, Mar 2, 2020 at 11:03 PM, Jonathan Kayne, KM4CFT wrote:
I have decided that I will be doing another revision of the board that will be built in a modular fashion
Yes, this has been an interesting thread. Looking forward to the next iteration. Learning from your more scientific approach than us old time Hams used when such equipment, as is available now, wasn't. 

A couple of comments though. You may want to do you initial troubleshooting at lower input frequencies, around a a few MHZ. Connecting the coax cables directly to the circuits (maybe right at the low impedance output of the IF amplifiers would be ok) could be significantly loading the circuits and changing things. 

It looks like you might have been using a high impedance input to the spectrum analyzer (not sure if they have anything other than 50 ohm inputs), if so use a 10:1 scope probe to sample your test points. 

A 10:1 scope has the magic ability to violate everything you thought you knew about transmission lines. The probes use a special lossy coax cable (thin restive wire for the center conductor) that dampens the "reflections" that normally cause frequency vs cable length effects and ringing. Thanks to old time Tektronix or HP engineers for figuring this out.  

Or, you could, also, connect a 50 ohm resistor in series at the end of your cable to the test point. That will mitigate some of the load of directly connecting the cable to the test point.  There are scope probes that do this or have a restive attenuator at the test side of the cable, and use regular coax rather than lossy coax. 

In some parts of your debugging it might make more sense to use closer to the maximum allowable signal levels (rather the trying -50dbm and such) and just use a regular oscilloscope for more generic shotgun checking if signals are there or not, and ballpark levels and frequencies look OK. Then go for the finer analysis of the Spectrum Analyses. 

Tom, wb6b

Re: Efficient speaker for low volume #audiocircuit #ubitx

Jack, W8TEE
 

Yep, I noticed that on the response curve.

Jack, W8TEE

On Tuesday, March 3, 2020, 3:50:25 AM EST, Trystan G0KAY <trystandavies+nodirect@...> wrote:


Jack,

The thing is, that Mylar cone speaker probably is an ideal speaker for morse as it has a resonance at around 700Hz, so that would explain it.

Trystan

--
Jack, W8TEE

Re: automatic side band switch.

Curt
 

Richard

Note that on the lower bands LSB is used for voice, but USB is used for all bands on FT8. Likewise, LSB is used on all bands for RTTY. So we need the manual function control.

Curt wb8yyy

Re: Efficient speaker for low volume #audiocircuit #ubitx

Trystan G0KAY
 

Jack,

The thing is, that Mylar cone speaker probably is an ideal speaker for morse as it has a resonance at around 700Hz, so that would explain it.

Trystan

Re: Only noise when connected to the antenna #v6

Evan Hand
 

Jonathon,

I have found the posts interesting.  I have been trying to duplicate your signal analysis measurements, and can do so up to the SSB filter.  There I am getting significantly different spectra.  I also cannot understand the large hump and ripple on the spectra.  Granted that I do not have a good quality SA, I am using an Analog Discovery 2 (AD2), it still does not make sense to me, as the frequency would need to be wobbling all over the place to get that kind of spectra.  For my measurements I found the same narrow peaks being shifted through the mixers and side spikes removed through the filters.  The frequency changing as expected.  The AD2 only goes up to 50 MHz, so could not measure all of the products in the first up conversion stage.

I will be interested in your measurements once you get it working.  (note: the rig that I tested was a v5, and would receive the signals and produce a tone when tuned to an offset of the injected sine wave.)

73
Evan
AC9TU

Re: Lna #ubitx

MVS Sarma
 

LNA at front end with out having BPF  for band selection would be catastrophic. Power from radio broadcasts will overload such LNA and make mess.

Better to use multi-band 3 section filters and then use LNA with attenuator , if needed.  Farhan says  we dont need  band filters as ubitx uses dual conversion.


sarma  vu3zmv


On Tue, Mar 3, 2020 at 11:31 AM Evan Hand <elhandjr@...> wrote:
There have been multiple messages on this site covering the addition of an RF LNA to the input of the uBitx.  All conclude that it does not make a significant difference.  That is not the case with adding amplification in the audio sections,, with an add on audio power amp being the most common.

If you find that you do not have enough speaker volume, I would add the power amp, most common are based on the TDA2030.  Example :
https://groups.io/g/BITX20/message/76640

FWIW
73
Evan
AC9TU

Re: Only noise when connected to the antenna #v6

Jonathan Kayne, KM4CFT
 

After some thought, I have decided that I will be doing another revision of the board that will be built in a modular fashion. I intend to connect RF lines together with SMA connectors to preserve signal integrity and use plain old stranded wire to run control signals. 
This will make it more easy to experiment with and isolate any potential noise problems. 
I also plan on adding two ground planes on both sides connected with via stitching to help with the noise and eliminate ground loops!
I will post again with my progress as I think the group might find it interesting!
73,
-Jonathan, KM4CFT

Re: Lna #ubitx

Evan Hand
 

There have been multiple messages on this site covering the addition of an RF LNA to the input of the uBitx.  All conclude that it does not make a significant difference.  That is not the case with adding amplification in the audio sections,, with an add on audio power amp being the most common.

If you find that you do not have enough speaker volume, I would add the power amp, most common are based on the TDA2030.  Example :
https://groups.io/g/BITX20/message/76640

FWIW
73
Evan
AC9TU

Re: uBITX6 assembly instructions

Evan Hand
 

Bill,

I believe that the issue is prior look up on the HFSignals.com location.  You need to be sure to not take the default url that you found before, rather type out the hfsingnals.com in the url, and insure that there is nothing beyond the .com.  That will take you to this page:
https://www.hfsignals.com/ 

Try the above link

FWIW
Evan
AC9TU

automatic side band switch.

Richard
 

The site information says that the sideband automatically switches at 10 mhz.  I just put my V6.1 together and am listening to a net on 80 mtrs. using the front panel usb/lsb  tab the side band stays at LSb no matter what I do. I can't at this time find another station above 10 mhz to see what happens. Is switching so automatic that I can not do it manually. If so why do I have the option on the front panel ?
Inquiring minds want to know
 Richard
KE5NCR

Re: Only noise when connected to the antenna #v6

Curt
 

Jonathan

I am less troubled by noise and leakage into the receiver than not being able to receive signals. Sweeping an IF signal into the final mixer should produce audio output when it gets within so many kHz of the LO.

Sometimes its desirable to disconnect things and test individual circuit blocks, a method used by many scratch builders.

The specific arrangement of the hardware can lead to coupling between things, but these should be smaller than a large RF signal.

Okay there is one thing that can wreck a circuit, a regulator that is oscillating,  but easy to notice that with a oscilloscope.

Do isolate the circuit functions in question,  and examine those. I even once troubleshooted a superhet receiver by touching my HF antenna to the IF section, as there were signals there. If not, you have nice instruments there.

Curt

Re: uBITX6 assembly instructions

support@...
 

Hello Bill

https://www.hfsignals.com/index.php/ubitx-v6-assembling-the-full-kit/

This link is active and can be accessed. Please use another browser in case you have any difficulty to open it. Copy paste this link in case you are not able to click the link from within the group.

This link provides a step by step instruction for assembling your V6 uBitx and is very easy.

All the best.

Thomas
--
Support@...

Re: TX frequency is 1.2 kHz off #bfo #calibration #cw #v6

Curt
 

Juha

sounds like have made nice progress!  yes the CW on transmit is a bit different - it tends to respond a bit slow and there is the matter of not pausing too long, lest the relay open up and we get the delay again.  I have somehow learned to do CW with it.  on receive, I installed a SCAF tunable bandwidth audio filter. 

enjoy your rig!

Curt wb8yyy

Re: Lna #ubitx

Curt
 

worthwhile to experiment, but the ubitx is quite sensitive when connected to a reasonable size antenna.  if your antenna is working, you should hear the noise level rise a little when the antenna is connected. 

possibly a preamp may help a little on 28 MHz, but it should not change much.  usually adding gain harms a receiver, once a receiver has enough gain.  some folk are boosting audio gain a bit, but generally not much need anywhere else. 

of course report your results. 

73 curt

Re: Only noise when connected to the antenna #v6

Dr. Flywheel
 

Are you using your SA Tracking Generator to check the behavior through the signal path? Did you measure the actual frequencies of the three OSC outputs?

---Ron
N7FTZ

On Mon, Mar 2, 2020 at 4:02 PM Jonathan Kayne, KM4CFT <jzkmath@...> wrote:
If I trace the signal through and there is noise appearing in the first stage then I don't think it's a matter of alignment. Plus I have tried that numerous times and it never helped. 
At this point I am literally connecting the spectrum analyzer to the antenna connector. Disconnect the antenna switching section from the rest of the circuit and it's clean. Connect the LPF plus 1st conversion to the circuit and the noise floor goes above the -90 dBm signal. I need to figure out what is raising the noise floor at the first stage which should fix the issue. 

Re: Only noise when connected to the antenna #v6

Jonathan Kayne, KM4CFT
 

If I trace the signal through and there is noise appearing in the first stage then I don't think it's a matter of alignment. Plus I have tried that numerous times and it never helped. 
At this point I am literally connecting the spectrum analyzer to the antenna connector. Disconnect the antenna switching section from the rest of the circuit and it's clean. Connect the LPF plus 1st conversion to the circuit and the noise floor goes above the -90 dBm signal. I need to figure out what is raising the noise floor at the first stage which should fix the issue. 

Re: Only noise when connected to the antenna #v6

Dr. Flywheel
 

More than likely, your IF oscillator frequency is off and the Xtal filter attenuates the incoming signals as a result. Try calibrating the BFO oscillator.

73's
Ron
N7FTZ

On Mon, Mar 2, 2020 at 3:03 PM Jonathan Kayne, KM4CFT <jzkmath@...> wrote:
It seems that somehow there is a bunch of noise making it into the radio. Just running it through the 1st conversion seems to bring the noise floor up enough for any reasonable signal to have adverse affects on the performance as seen by these two pictures! This was at the antenna connection so somehow noise from the 1st conversion is bleeding into the circuit making it too noisy to use. 
Any ideas on how to fix?