As has been discussed in several earlier threads, many of us suffer from an extremely strong birdie at 7199 kHz.

Today, while experimenting with the VFO drive strength, I had a surprising observation:

By default the VFO drive strength is 2 mA.

I increased the drive strength by adding the following line to the setup() routine:

si5351.drive_strength(SI5351_CLK2, SI5351_DRIVE_4MA);

Then the birdie at 7199 completely disappeared!

So far I haven't noticed any other negative side effects on the receiver.

Can other BITX40 users perhaps try this too and share the results please?

You can try other drive strength values too (accepted values are 2, 4, 6, 8 mA)

If this is indeed a good fix then we may have to include this in the standard Raduino code,

73, Allard PE1NWL

Thank you all for sharing your experiences with different drive strengths.

So far it seems that 4mA is the optimum VFO drive level for a standard Raduino (with VFO on the low side). But this based on only few radios.

Are there any other builders who would like to try this out and share the result? The more data the better.

I'd like to add this improvement to the standard Raduino sketch v1.05.

Thanks, 73, Allard PE1NWL

I am having sort of the opposite problem. I had the original Raduino sketch loaded with no tuning clicks and no birdie at 7.199. Then I loaded? the new standard?? version 1.05 and now I have a very strong birdie at 7.199. The Si5351 drive is set to 4mA Any suggestions or clues to fix this?

PJH, N7PXY

Is this new standard, a raduino.ino sketch version??

Probably what happened is when you uploaded a sketch, your IDE software uploaded an updated Etherkit Si5351 library ?with the sketch. That's easy to fix. Just click on sketch at the top of the Arduino IDE software, go down the menu to include library, move right to manage libraries at the top of that menu. Type Etherkit in the search bar. Look for Etherkit Si5351 in the results and look at the version number installed. If it is higher than 2.0.1 then click on the underlined More Info at the bottom of the description. Select version 2.0.1 and install. Then re-upload your sketch.

The newer libraries produce a louder click when changing frequency. The older versions work great without trouble. And that's usually all there is to it.

The loaded sketch is what has been referred to in the group as the latest 'standard' raduino .ino sketch. And yes I had the Si5351 library 2.0.1 loaded in the IDE, that's what I don't understand. As you said this arrangement is supposed to eliminate the birdie. I guess I might have to reload an even earlier version than 1.05 and build up from there??

Any other ideas?

PJH, N7PXY

To: N7PXY

Ash has just recently uploaded the Bitx40.ino file used in the shipped product. You should get this and upload it to your Raduino and make sure you still have Etherkit 2.0.1 library installed. This should be a factory reset. You can find and try changing a line of code to try and scare away the birdie later. Which is on line # 598.

Here is the github link for Ashar Farhan's working sketch-?https://github.com/afarhan/bitx40

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Makes sense to me.?

The birdie at 7.2 is due to 5*4.8mhz = 2*12mhz ?The crystal filter is between the VFO and the BFO so those harmonics should never meet if we have proper shielding. ?Coax on the VFO is part of proper shielding.?

Of course changing drive level will adust the strength of the various VFO harmonics and will also have an effect.

Will be interesting to see how bad that birdie is when we use the Si5351 CLK0 for the BFO, as there will be some crosstalk within the Si5351. ?We do have the option of moving the VFO to 19.2mhz, reducing the birdies but using the not-so-steep skirt of the filter

Kevin and John,

Thanks for the information. It has already been implimented.

I put RG174 on the VFO feed from Raduino to main board early on in the build.

The line setting drive current to 4 ma is active and I may set it back to 2 ma as that is where it was before the birds showed up.

My intention now is to do the "factory reset" after I play around with a few things just for giggles.

Gotta find the time....

Tnx guys,

PJH, N7PXY?

Grounds are tricky alright. ?Grounding the shield at both ends is the standard way of using coax between modules. ?In this case we're mostly interested in a shield not a transmission line, so detaching the ground on one end is worth trying, perhaps with a 0.1uF cap across the gap. ?Some have reported that a large electrolytic cap across the raduino 12v power supply reduces the clicks, so there are likely spikes in the 12v current (and through all available grounds) when you spin the tuning pot. ?I'd tend to stick with the large electrolytic cap and perhaps a series resistor if that's all it is. ??

Though ground loops can pick up RF. ?Anybody who has probed a busy circuit board with a scope probe using a 6 inch ground wire at the probe tip, then went to just shorting the ring near the probe tip to the nearest circuit ground has seen evidence of this. ?The noise the scope sees can be reduced by more than an order of magnitude. ?If this is the issue, then you probably don't want that 0.1uF cap.

Where grounds are really trouble is when you have multiple power supplies plugged into different circuits from the main fusebox of the building.

Jerry

Ok, before you all take the raduino or the vfo apart, I'm getting the same birdie on my Icom, my Codan and my 817, as well as my homebrew MST-400. ? Looks to me ?as if this is an external phenomenon.

Norm vk5gi

McLaren Vale

South Australia