On 5/26/2020 5:11 PM, Curt via groups.io wrote:
Sprite Band Pass filter question for Chuck:
My Sprite has an output BPF labeled "V2", FL3 n FL7 are 1200 pF; FL2 and 6 are missing; FL1 and 8 0.39uH 11t 37-6 core.? "Default" has FL2 n FL6 = 1000 pF; FL1 n 8 0.22 uH.? The Elsie plots are very similar with center frequencies comparable.
My board says "V2".? Refresh my memory about the differences.
Gangue,
The MAIN difference between VER.1 & VER.2 is the added trimmer cap in the OFFSET section to allow loading a crystal to change its frequency in the receive mode.
In the KEYING section the capacitor from the base to ground was changed from .001 to .1uf.
Crowding was reduced in the PHONES connector area by moving the 1N914 diode.
As for the FILTER section, there are doubled caps:( FL2 & FL3) and (FL6 & FL7) to allow cap combinations when moving it to different bands is a single cap value is unavailable. Likewise, FL4 & FL5 are in series for combinational ease. The overall format is that of a Pi filter so one can also easily substitute a LPF for any band of interest using all the extra pads. There are lots of band pass filter values already worked out and included with many kits on QRPme's site and others.
Say you wanted to put the Sea Sprite on 30m..... BCI isn't much of a problem there so switch to a 30m Low Pass Filter (filter values are everywhere), adjust (if necessary) the oscillator caps CEG & CBE (feedback caps: CAP=emitter to ground & CAP=base to ground for the oscillation transistor), plug in a 30m crystal and Bob's your uncle! You are on 30m....
Rex? W1REX
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