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LSB signal looking more like AM
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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. |
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Mindlessly twiddling RV1 on the Bitx40 (or RV2 and RV3 on the uBitx) will blow the IRF510's.
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I assume you were watching IRF510 drain current when you did the adjustment.. If not: Power down, turn that pots full clockwise (it's backwards) for minimum drain current. (it's backwards) and minimum drain current. Carefully adjust that pot for 100ma of quiescent current through the IRF510 as instructed on the HFSignals tuneup page. Will be nothing at all for about half a revolution, then the adjustment gets kind of touchy. On Wed, Dec 5, 2018 at 04:50 PM, <joshuaclough4@...> wrote:
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). |
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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@...> 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. |
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Hi,
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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. 73, 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. --
bark less - wag more |
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Gordon Gibby
Good advice Bill Cromwell!
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And maybe he can find some ham somewhere he still knows some things and can listen to him. Or use some waterfall and a CW Carrier somewhere to allow him to plot his own response ¡ª there will probably be a lot of fun learning involved, and that¡¯s very very valuable Cheers! Gordon On Dec 6, 2018, at 06:55, Bill Cromwell <wrcromwell@...> wrote: |
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Thanks for the replies.
Will double check the sdr. The first time I used it (when it displayed the correct LSB signal) It didn't even have an antenna on it, I've since added an indoor (albeit non-hf) antenna, was hoping it would cut down on the sensitivity to an HF radio transmitting outside (the antenna at least, radio is in the same room). Second to that, I'll try what someone PM'd, suggesting of using the Raduino V2 digital BFO sketch (evidently after doing the proper mods). https://github.com/amunters/bitx40-raduino-v2 |
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