STOP - I changed my mind! (hi)
I don't think I was wrong, after all.
Let's be specific now.
STN. 1 is a radio with broadband noise operating on 40m.
STN. 2 is a K3 operating on 20m.
STN. 3 is an Orion operating on 15m.
All stations are running 100w.
When STN. 1 transmits on 40m, its broadband noise (over the entire hf band)
causes the s-meters of STNs 2 & 3 to rise by 3-S-units or abt. 18 dB.
STN. 1 adds a Dunestar Model 300 (40m) Bandpass Filter to his antenna
feedline. This filter will suppress all signals outside of its bandpass
(after a specified distance in kHz) by about 40 dB.
THUS the noise being transmitted on 20 and 15m is also reduced by 40 dB.
THEREFORE the problem originally seen on those two bands at STNs 2 & 3 is
gone.
The BPF has successfully eliminated it.
Of course the broadband noise is also transmitted across the entire 40m band
because that portion of the spectrum is not attenuated by the BPF.
So I return to my original standpoint that bandpass filters will help reduce
noise level increase on other bands at multi-transmitter stations.
Of course one assumption might be that the noise is being transmitted inside
the shack, thus not going through the 40m BPF. Fair assumption, but in the
case I was personally involved with (and solved), that was not the case.
What we found was the noise level varied when we rotated the two beams.
It was worst when they were pointing towards each other and much better when
pointing away from each other or off the sides.
This, BTW, was the reason they were blaming my antennas and not the two
radios they were using.
As it turned out, it was both TS-590s causing the problem.
When the radios were replaced with a TS-850, and then a K2, the problem
ceased.
Ergo, at least in that case, the broadband noise was through the antenna
feedline and out the antenna.
A bandpass filter (which they did not have) would have helped.
Am I missing something here?
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Rick -
DJ0IP / NJ0IP
Sent: Monday, July 28, 2014 10:01 AM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] THANK YOU AND APOLOGY - for Billy
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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