LR frequency anomolies.

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dave slagle
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Joined: Sat Jan 22, 2005 3:54 am
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LR frequency anomolies.

Post by dave slagle »

Hey Stephie,

A friend has been running the LR with lundahl iron and recently switched to my nickel (shame to call it iron).

He has two issues he is trying to track down.

There is a 4-5dB bump at 50hz. your measurements in this post show a bit of a bump but not that drastic. From 100-2500hz everything is fine but at 5Khz it is up 4dB and that goes to 8dB at 20Khz and keeps going until around 70-80Khz where the iron rolls it off.

do you have the circuit built in LT spice? /have any ideas where to look. in my quick sims with a different LR, I could get similar behaviors but the values needed to be way off. (it does look like the parallel resistor to the smaller choke being undersized will do it)

thanks!

dave
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sbench
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Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

Hi Dave. I'm sure I have the file... I'll have to go searching for it and there's probably only a value or two tweak to fix it.

Sorry for the late response... I was out of country for a couple weeks with my sister.

Stephie <3
sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

There were a number of value changes between the Lundahl iron and your nickel. Remember the HF iron from Lundahl was 450mH and yours is 1H. That necessitated R changes.

The "stock" values with your iron aree R1/R14=169k. R7/R19=13.3k. R2/R15=5.62k and R8/R20=750 ohms.

If he has those values installed (they were 26.7k, 5.23k, 5.9k, 715 for the Lundahl iron), and STILL has those bulges listed, he can try the following...
For the LF bulge, change the feedback pot (200 ohm) value... DEcrease the resistance. Otherwise change R2/R15 to 5.36k, and R8/R20 to 909 ohms. For the HF anomolies, change R7/R19 to 14.3k, and increase R1/R14 to 300k.

My first guess is he has the Lundahl values installed and that won't work.

Let me know if that helps.

Stephie <3
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