Re: Simpler spur fix

Jerry Gaffke


Going to Axicom relays looks like it pretty much cleans up our issues with harmonics.

But this thread is about spurs, not harmonics.
Raj has found that replacing the toroids at L5,L7 around Y1
and also L1,L2,L3,L4 on the 30mhz LPF with SMD inductors will clean up the spurs.

With both spurs and harmonics cleaned up, the rig can met regs.

Yes, the board layout is not ideal.
Board layout is why we have coupling from the power amp into Raj's L5 and L7.
But looks like replacing some relays and inductors is all we need do
to clean up the spurs and harmonics well enough to meet regs.
(We might need to clean up a trace around the 40mhz transmit LPF, I'm not sure.)

Regarding Sascha's question: 
   "wouldn't it be possible to just shield the original toroids from electromagnetic influences?"
I think it very well could work, worth trying if you have shielding on hand but not the SMD inductors.
Copper blocks electric fields (and electromagnetic waves) quite well.
Though if it's stray magnetic fields that's causing trouble, maybe not.

Replacing the toroids with surface mount inductors seems easier to me
than adding well grounded copper cages around the toroids.

Jerry, KE7ER

On Mon, Oct 15, 2018 at 05:52 PM, MadRadioModder wrote:

It’s the PCB tracks/ /layout and relays that are the problem… not the toroids/ toroid layout.


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