Re: low-band filter


On 11/13/20 12:52 PM, doug wrote:

On 11/13/20 2:40 AM, jdow wrote: <>

That has some interesting observations and well down the page some interesting schematics.

It appears he revisited the filter a couple more times if you dig a little.


On 20201112 18:01:07, doug wrote:
I wonder if there is available from some source a simple filter that would attenuate the broadcast band
to a sufficient extent as to not create harmonics or overload the input of simple sdr devices, or the tinySA
spectrum analyzer. I am interested in tracking down the source of some broad-band noise in the lower
frequency range from about 3 to 15 MHz.
--doug, WA2SAY

Thanx, JoAnne--It's obvious that the writer has done his homework. I have already investigated some
filter designs but my problem is that I'm no longer working in this field--I've been retired for 18 years--
and have no access to the components any more. I am hoping that someone, somewhere, who does
have access has designed and built a filter for the purpose, and is now selling copies of it for some
reasonable price--say $15 or so? (I'll put it in a shielded box, if it doesn't come with one.)
--doug, WA2SAY

It turns out that there are some ready-to-use hp filters. On source was Canadian Amazon, and they can't ship to US,
apparently. (Tried to buy but was was advised I can't.) But US Amazon has a couple of filters, a bit cheaper, AAMOF,
and I ordered one. About $16. I suppose it has about $1.00 worth of parts in it, but worth the no-hassle!
Thanx to all. I didn't know that Amazon would have such a thing, but I should have known better--they have
--doug, WA2SAY

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