To track down that interference, put a battery and speaker in with the uBitx, no antenna,?
wrap it all up in foil as Iz Oos suggests.
Should not hear your local broadcast at this point.?

Plug in the antenna, grounding the coax braid where it enters the foil, see if that brings it on.
If so, you need a highpass filter in your antenna line.

Plug in headphones, tying audio ground to the foil where it enters, and give a listen.
If that brings on the interference, then add caps and/or chokes to the wires at the headphone jack.

Remove the battery, power from your regular power supply with supply ground tied to the foil.
If that brings it on, you need caps and/or chokes where power enters the case.

The above strategy won't cure all the various problems that folks might have with a uBitx.
Something like an oscillating LM7805 would be difficult to find without a scope,
and should be cured whether you have broadcast interference or not.
But if you prevent an interfering station from entering the case, it should not be present in the audio.
Perhaps v7 will have an extra $0.25 worth of caps, series resistors to protect Nano IO cells.

Generally, if having trouble with broadcast interferance, use a metal enclosure.
Make sure everything leaving your uBitx such as power, antenna,?and headphones has
the return wire properly grounded to the case where it enters the case.
Signals other than the antenna should have 0.1uF caps from signal to ground right?at that case boundary.
And if the antenna is the source of the interference, use an RF filter to not let it in the box.

Jerry

Hi Curt,
Initially I had TDA2822. That time also I had same experience. Now I have changed it to LM368 by making an adapter board. I have not added the capacitor. But will check CR's capacitor suggestion fixes this.

I dont have any other transceiver to verify my antenna nor can check and confirm if AM broadcast is happening now. Let me check tomorrow morning and see if AM is being heard.

73
VU3ONX

I just received notification and tracking information on my V6, so it should be here in US in about a week. I will post when it arrives. Don't know why I'm getting excited about this, this will be my 8th Bitx since they were introduced.

Joel
N6ALT

Thank you CR,
I tried fixed that capacitors. I could not hear local broadcast. Not sure if this is because of the capacitors or the local broadcast is turned off as it is midnight here. I will check it again tomorrow morning and will report back.?
But when I tuned into 7.05 , I could hear Morse code which is ultra fast for me to catch.

I hope it is fixed.

Thanks any way for helping me out.

73
vu3onx

--
Jack, W8TEE

Jack,

Could you provide a link this this new group - I can't find it.

73,

Paul K2AYZ

OM vu3onx

Its not surprising to let broadcasts sneak into our projects.

Possibly it is being received by your audio board, do examine if it has the proper capacitors on the dc bias to the lm386. Also try headphones to see if it goes away with less audio gain.

Next comes getting into the regulator circuit as Chuck mentions.

Finally, some mention needing a filter to reject medium wave broadcasts in the front of the ubitx. But I am first suspicious of the audio amplifier.

Curt

Iz

I am curious what components you used to replicate the 45 MHz LC filter, and exactly where you installed it in the v4??

I am too concerned about radiating stuff above 30 MHz (the PA and existing LPF should be fine).? It's two spurs not too many MHz away when using 10 or 12 meters that need at least 10-15 dB rejection in my unit.? I like the xtal filter as is so not anxious to convert mine completely to a v5.? all is well enough with it, until I want to do SSB on those upper bands.?

73 Curt

When I entered the hobby I had a PC active speakers and when turned on I was hearing FM broadcasts on 88-108mhz. Then I placed speakers and the circuitry in a metal box and FM stations disappeared. Use aluminum foil I'm case you have a plastic enclosure to see if this might help.

ONX:

? I should have been more clear. There is a LM7805 regulator in a large TO-220 case that sticks out from the "Raduino" board attached to the back of the LCD display. Solder a 100nF from each of the outer two leads to the center lead of the LM7805.? These regulators are high-gain devices and can oscillate. The onboard bypass capacitors in the kit are not always effective. My 7805 oscillated and caused apparent broadcast interference on a sporadic basis.

Chuck w8mqw

I haven’t solved this issue yet. I attached a ground wire to my EFHW antenna, and that didn’t help. I pulled the lm386 chip out and it looked fine and I put it back in. I don’t have any other rigs to confirm it’s not my antenna. Nothing happens if I touch the extra coils of wire.?

First thing to try is to bypass each terminal of the 5-volt regulator on the Arduino board to ground with two 100nF.? (The regulator will oscillate and induce the broadcast images.)

Second, you may have to build a bandpass filter for the band of interest. Or use a T-network antenna tuner that is both a LP and HP filter.

Raj, Iz, Jonas, Ashar

thank you for reply, nice to hear from you all.? I wouldn't be asking if I had a spectrum analyzer to make the measurement!?

I do have the relay board from Gordon installed, my harmonics are fine - CW is fully compliant and I am okay on SSB through 17 meters.? This was confirmed using a club member's analyzer.?

Next I tried installing, every which way possible, a second 45 MHz xtal filter stage.? It greatly reduced the CW output on 40m to under 2 watts - so I decided this wasn't good.? (I trust not every v4 does exactly this, but I know of at least one other nearby that does).?

Next I tried an LC filter similar to v5 has, it did not squash the 40m as much, but did nothing to improve the spurious on 10 and 12 meters - strong spurs hugging the carrier on each side.?

I obtained some shielded SMT inductors from coilcraft, with a Q around 70 at 45 MHz.? More square than the one's Raj used (with little notches in corners) - was difficult to install.? 10m beacon sensitivity is similar to what I had.? Okay I can try the 45 MHz filter again - if it does not wreck 40m CW (with the better shielded inductors at 45 MHz on the existing filter) I can trust it will do something against these spurs (and can confirm the loss isn't huge).? I have one doubt on these inductors, that the shielding was intended against a much lower frequency than 45 MHz - so hard to infer what they are doing - except they are a much smaller antenna presence than the T37-6 (?) inductors.?

73 Merry Christmas and other blessings,

Curt WB8YYY

开云体育

Same to the group?

Hi Gavin,
Is this issue resolved ?
I also have similar problem. Not sure what is the resolution. ( I have talked about it in a different post)
I am from Bangalore / India and I have a uBitx v3 running v0.20 software.
Kindly suggest a resolution. I am also working on all the suggestions provided above.
Thanks in advance.
73
Vu3onx