AOR AR8200 User Manual
Wider bandwidth IF filter
Wider bandwidth IF filter for NFM
With this modification you got possibility of:
- Meteosat and other geostationary satellites weather pictures decoding
- NOAA and other polar orbiting satellites weather pictures decoding
- 9k6 amateur packet decoding
- Significantly better readability of Inmarsat voice transmissions
- Decoding other higher speed data transmissions as FAX etc.
- if you know of another let me know
Three types of narrowband IF (Intermediate Frequency) filters are used in AR8200:
- 3 kHz for both SSB, CW and NAM
- 9 kHz AM and SFM
- 12 kHz for WAM and NFM
Widest one is 12 kHz filter, but if you want to use AR8200 for decoding higher data
speeds or other data transmissions you need bandwidth at least 30 kHz and one of filters
must be replaced by wider type. You can change any of these three filter but I recomending
12 kHz filter. Standard narrowband FM transmission you can still receive on SFM mode
without significant difference between 9 kHz SFM and original 12 kHz NFM mode. Same
thing for WAM and AM receiving mode, because NFM and WAM using one filter. Of course
you can still clearly receiving for example amateur repeater on 30 kHz filter but if there is
another transmission on channel 12.5kHz close you will hear it in background too.
After searching on Murata website I have found type for ideal replacement - SFGCG455BX.
It has same package, bandwidth of 30 kHz (+/-15kHz) and SMD package same as Murata
filters used in receiver. Other filter parameters as loss and impedance little vary but it is not
problem. The problem is source for this new filter. I'm tried contact official distributors but
they selling 500+ quantities. Other components distributors like RS-components, GME or
GES don't have any of Murata filters in stock. My last try was searching by web search
engine. And I was found one radioamateur components distributor here in Europe selling this
filter by one piece. They are from Finland and nam is
EL-KAMA. They also selling other hard
to find components.
IF Board with original filter:
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Amateur Radio Directory
www.hamdirectory.info
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Wider bandwidth IF filter
Desolder old filter located on IF board using desoldering braid:
Adjust new filter leads and solder on place:
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