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Hi there uBitx owners,

today a ham confirmed me that my modulation was only in the treble part of the audio spectrum: no bass and (that the most annoying) no medium frequencies to hear...

I wonder? if this a known and common problem, although I was not able to find something related while browsing the group's messages.

For information, I just use the electret mike as delivered with my V3 board.

Any comments ?

73s
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Laurent F5FIE.

Laurent

my best guess is the BFO calibration is off - shifting you passband to the high side.? possibly you might hear similar distortion on receive??

try the instructions here, as required



(use CTRL click to launch the url - it goes to the K3PZN ubitx page)

the only other consideration is some ubitx owners report low transmit drive - see if you wattmeter at least moves on transmit?

Curt

You may like to hear your modulation yourself with another receiver. You transmit into a dummy load and you receive without any antenna. I have ver. 3 and has no basses, say lower than 500hz. Listening to my SDR receiver I like my modulation a lot! Excellent for dx. I had generally excellent reports. However I trust more of what I hear myself than the reports by others. Not always their carrier is yours, they might have strange settings in filters, pbt etc

Hello,

thank you all for your excellent replies: I'm going to make the BFO calibration procedure, and listening by myself on my good old DEGEN 1103 chines receiver.

And yes, I was surprised at first by the too higly pitched received modulation: it is a good second facts that leads to a BFO calibration problem.

I will let you know!

All in all this uBitx is a great transceiver for the price, and for many like me a chance to transmit with something else but commercial hardware.

And many thanks again for great support.

Best 73's.
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Laurent F5FIE.

Hi!

I highly recommend doing it using a sound card microphone input. That
way you can adjust the passband using something like fldigi to monitor
the noise floor in the passband.


-adrian

Do not use receivers that have an antenna connected. Remove the whip of the degen if possible. Transmit into a 50ohm dummy load and not to the antenna for these tests.

Hello Adrian,

a good avdice, I'll try this this week-end, as I need to bypass first my AGC board from kit-project (soldered on the slow agc position), who changes a littke the overall audio response...

I'll let you know here.

73s

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Laurent F5FIE.

Hi, just to add my 2p worth. I had this problem and like above, used a dummy load and transmitted an LSB signal. This was received by another rig and showed the BFO was way off.?

I replace the SMD capacitor with a number of others in a number of values and parallels, but could not get the sound I was after. They were all too low or too high in pitch and often just unable to understand at all. Eventually I looked for another set of capacitors and found one from Rapid Electronics. variable 7pF to 50pF SMD. Fitted this and then adjusted it, a bit at a time. until I got the sound I wanted.

Thanks to all here for the help and discussions explaining the fix.

73s Vaughn

Hi,

well I finally hooked up my headphones output to FlDigi, and that confirmed my uBitx's BFO was off, giving an audio about 300Hz too high, which I corrected successflully via the setting BFO menu (I guess my problem was different with Vaughn's one).

I will try to make some phone contact to confirm the transmit audio is actually better now, as I don't have a dummy load to avoid overloading my test receiver.

Thank's again to all of you for you great help.

73s.


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Laurent F5FIE.