Low Pass Filters

General discussion and support for the Peaberry SDR V1.

Low Pass Filters

Postby Ve7pke » Sun Jan 13, 2013 12:34 am

In case you are not reading the Softrock40 group in the last week there has been a thread on issues with number of turns on the Toroid's for the low pass filters. I believe the Ensemble RXTX has updated turns information. I expect Dave will update his build directions soon. ;-)
Since I had not built my external Lowpass Filter for 40 on my 4-,30,20 Peaberry, I took the time to measure the inductors before I built it.
I used a VNWA3 as a LCR meter and measured the inductors. I found I needed to remove 2 turns to get the correct inductance of 1.3uH. This seems to line up with the information the SoftRock group.
Attached a S21 sweep of the filters as constructed.
Peaberry External LPF.jpg
VNWA3 Sweep of Filter
Peaberry External LPF.jpg (128.9 KiB) Viewed 2079 times

I put it in a Pomona box
They are pricy but nice. I figured since the radio is so classy it deserved a nice enclosure.
Digikey part Number 501-1103-ND
Pomona Box with 40m LPF.jpg
Nice enclosure
Pomona Box with 40m LPF.jpg (86.52 KiB) Viewed 2079 times

Posts: 15
Joined: Fri Nov 30, 2012 7:30 am

Re: Low Pass Filters

Postby G0XAR » Fri Jan 18, 2013 7:06 pm

Thanks for the Info, once I have finished the main build making the LPF is my next thing to do. ....it is amazing how often the VNWA crops up in tests just lately. I have the version 2 and am slowly getting to grips with it.

73s Steve G0XAR
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Joined: Mon Nov 19, 2012 2:27 pm

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