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Michael Black[_2_] · February 10th 09, 08:09 PM posted to rec.radio.amateur.boatanchors

On Tue, 10 Feb 2009, wrote:

On Feb 9, 9:14*pm, " wrote:
Looking to buy a 3395 AM filter as used in early tube Heathkit
receivers..any other suggestions on receiving AM with homebuilt filter
system? *TNX 73 *Harold
Followup: I am looking for a 3395 KHZ. AM Filter for a Heathkit SB301.
The AM filter was offered as an Option . The SB 301 will not receive AM
without the optional filter....It has AM detector and everything but the
filter..I thought someone might have worked out a substitute for the
Heath filter..like a high Q tuned IF can or whatever... TNX Harold

At 3395KHz, LC circuits won't provide enough selectivity. You're either
going to have to find a Heathkit filter for sale, which likely is
going to be hard since the SB line was primarily for SSB so the
optional AM filters would be in scarce supply to begin with, or see
if you can get a more recently manufactured filter, assuming those
third party companies have bothered with AM bandwidth filters.

You could have some crystals ground to the frequency, and try making
a ladder filter. Or get just one, and make one of those old phasing
type crystal filters, which would need loading to get the needed
wide bandwidth, and of course wouldn't provide good skirt selectivity.

You do realize you could do what people did at the time, when SSB-only
rigs starting coming along but AM was still common? Receive using
the SSB receiver, which will chop out the unneeded sideband and
knock the carrier down so it won't be a bother, and then the signal
becomes SSB inside the receiver where the BFO can properly demodulate
it.

Michael VE2BVW

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