[AMRadio] AM filter for an SB-300


SBJohnston at aol.com SBJohnston at aol.com
Sun Apr 9 14:42:25 EDT 2006


Mark W1EOF wrote:

>Probably a long-shot, but I gotta ask: Do any of you have experience either
>making a AM bandwidth filter, or modifying a SSB filter for a SB-300 or
>similar receiver? I have one article on modifying a SSB filter by installing
>four new crystals. Given the expense of buying four crystals I've been
>re-thinking it.

I just did exactly this.  I tried modifying an SSB filter - no luck at all.  
The closest I could get was to eliminate two of the crystals but the blow-by 
outside the main passband was unbearable.  Then I changed the four crystals in 
the SSB filter to the frequencies in a Heath AM filter - that worked really 
well.  To keep the costs down I got the crystals from Petersen Radio at $11 
each.  

I used my spectrum analyzer with tracking generator to confirm operation and 
tweak the parallel cap values.

Steve WD8DAS

sbjohnston at aol.com




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