Re: LSB signal looking more like AM

Bill Cromwell


JoshuaClough4 starts his post with his SDR. I have been playing with SDR a little and with "legacy" radios for a long time. That SDR can be and probably is being pushed *hard* by rf being generated right next to it - in the same room, in the same house, on the same estate. Not in the next state. There are so many ways with that kind of proximity to overload the receiver.

Inside the transmitter the carrier and the opposite sideband are fully present. The signal is processed to remove the carrier and the opposite sideband and then send it to the antenna. But due to varying amounts of leakage they are always present on the same estate, in the same house, and even down to a couple of inches away from the transmitter. A new ham who would just casually tweak those pots while watching the SDR may be one of the new hams who denies that a shielded box is needed for the receiver AND for the transmitter.

Just as a suggestion..reset those pots following the directions for the radio. And then leave them alone until *after* you have installed replacement transistors. Then lookup a WebSDR station within range of your transmitter but still hundreds of miles away (well beyond your local leakage). Examine your signal as seen from afar without having to enlist some other ham to look at it from afar on one of those dreadful "legacy" ham stations :) Back in antiquity we relied on distant friends to examine our signals from those distances. Now we can do it ourselves via WebSDR so the receiver is beyond the "local leakage".

I mentioned newbie mistakes and misunderstandings. Somebody is going to be offended. There are hundreds of us here. A few have thin skins. It's really hard trying to 'elmer' new hams via email and mail lists even if everybody uses the same language. We don't. I'm trying to help and nothing is off limits. Real questions here or in private are welcome. Flames will get you membership in my bit bucket.


Bill KU8H

On 12/6/18 3:14 AM, iz oos wrote:
I don't have a bitx40, but seems you should set BFO further in a way you have only the 500-2500hz bandpass.
Il 06/dic/2018 01:50, <joshuaclough4@... <mailto:joshuaclough4@...>> ha scritto:
My SDR shows my BITX40 signal looking more like AM. Has the carrier
and USB when it should not. The USB does look weaker than the LSB
that's actually supposed to be there, but still way too strong.
I've tried adjusting the two pots thinking that something was
overdriving the signal to create this, but those in any combination
don't seem to change the sideband supression (or lack there of).
I even tried changing the raduino sketch (which being evidently a
clone was fun in itself) without any change.
I've previously tested a lot of stuff already on the board because
It stopped transmitting before and stuff tested fine, which drove me
nuts. Eventually figured out it was the incompatible microphone type
I had hooked up. Had simultaneously changed the power supply and
thought that had damaged something and never thought about the mic.
bark less - wag more

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