Yes, you guys are all correct and I was wrong.
I dunno what I was thinking.
The transmitter's broadband noise will indeed go through the bandpass filter
because it is also actually transmitting on that frequency too.
My mistake. THANKS for the correction.
So the only help is to filter directly after the PLL, which of course the
user cannot himself do.
Buy a new radio, I guess!
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Monday, July 28, 2014 8:47 AM
To: tentec@contesting.com
Subject: Re: [TenTec] THANK YOU AND APOLOGY - for Billy
On 7/27/2014 11:26 PM, Rick - DJ0IP / NJ0IP wrote:
> I should have said by inserting a bandpass filter in the antenna line
> *of the transmitter causing the noise*, we can reduce all interference...
Not quite. Bandpass filters can only kill out of band noise -- that is, a
20M bandpass filter passes ALL 20M signals, regardless of where they come
from, but will effectively prevent its own noise from being heard on 30M,
17M,15M, 12M, and 10M. But it will have NO effect on in-band trash -- trash
that it generates on 20M, or 20M trash that someone else generates.
Likewise, a 15M bandpass filter on the 15M rig will prevent it from hearing
20M trash, but it won't do anything for trash that is ON 15M from a 20M rig.
73, Jim K9YC
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