Bandpass-filter, Diagram from HP-SDR
Baumappe HP-SDR (PDF)
On the Internet you could find the homepage with DATA for AMIDON TOROIDS, and the use of ON-LINE calculation of inductans/resonans.
The finished print:
From TOP of PRINT you find:
As it look now, the 12/10 and 6 meter filter has to be changed.
The amplifyer is tunning, after changing some wrong capasitors, only 10 pf, must be 100 nf, the smal blue spot on the print.
Be awhare of the amplifyer coils. Follow the description.
Remember to insert a damping on your VNWA input ( - 20 db ), for not do dammage ur VNWA.
My SUPER-INSTRUMENT, DG8SAQ's VNWA from SDR-KIT,
is used to measure the filter.
A tiny Lab-Top is dedicated to
The VNWA also have possibility for Spectrum Analysing, so IN_ALL, a very useful instrument on field day and a measuring evening.
To day the filter is optimized.
Old pictures is changed to new, with mush better measuring results.
|Measuring 160 meter.:
Result of LOW-PASS-Filter for -> 2.5 MHz
The picture talk for it selv.
RETURNLOSS: -29.07 db
The cut-off frequency go down more than 55 db.
PUSH and PULL the coils to best result.
|Measuringr 80 meter:
Result of LOW-PASS-Filter for 3.5 - 3.8 MHz
Just after the book!!
LOSS les than 0,5 db
RETURNLOSS -27 db
The cut-off frequency go down near 60 db ved 60 MHz
|Measuringr 40 og 30 meter:
Result of LOW-PASS-Filter for 7.0
and 10 MHz
Very close to the goal, and not to change any more.
RETURNLOSS: more than 26.5 db
Afskæringsfrekvensen falder fint 55 db
for 20, 17 og 15 meter:
Result of LOW-PASS-Filter for 14,
17 and 21 MHz-båndet.
InsertLOSS: on 14 MHz er 0,65 db
RETURNLOSS: - 26,26 db
for 12 og 10 meter:
Result of LOW-PASS-Filter for 24 MHz-båndet.
The 21 MHz band is better in this filter - I accept this result.
24 MHz :
|Calibreted to 100 MHz:
How does it look between 60 og 100 MHz?:
|There is a
filter more, but I have to experiment a little more with this for the 6
OZ6YM, Palle, den 3. oktober 2011.
Think I can not make it better than this in a hurry.