Michael Black wrote:

You do realize that it may not be the transmitter?

If your receiver (and you don't specify what it is) hasn't got
good strong signal-handling, the station may be overloading it
and causing the junk. And at first glance, it wouldn't be
obvious whether it's the receiver or the transmitter.


Excellent suggestion. Try a high pass filter passing everything above
1710 to see if you have an improvement.

At least then you will have a good indication if it is a problem of
receiver overloading or not ...

If you are using a transceiver as opposed to a separate receiver/xmitter
(I know, I am an OT) you can use an rf switch to cut out the filter on
xmit to "cure" the problem.

Regards,
JS

Why all this stuff about "high pass filters" and such. You are dealing with
a spot frequency, not a band of frequencies. A simple parallel resonant
notch filter should do the job quite nicely and still pass everything from
DC to daylight except that spot frequency.

Jim

On Wed, 24 Jan 2007 08:49:21 -0800, "RST Engineering"
wrote:

Why all this stuff about "high pass filters" and such. You are dealing with
a spot frequency, not a band of frequencies. A simple parallel resonant
notch filter should do the job quite nicely and still pass everything from
DC to daylight except that spot frequency.

Hi Jim

There's not much more effort in completely covering a band of problems
with a band reject (high pass) filter. The original poster could
discover the NEXT broadcaster creating problems when he limited his
suppression to the first one. Who needs a chain of notch filters when
one would work as well for the entire band?

73's
Richard Clark, KB7QHC

Because he's got a SINGLE frequency interfering with his station. To hell
with covering the entire band. A single parallel resonant network will do
something in the order of 80 dB of rejection if the L and C are at LEAST
something reasonable for Q.

Care to calculate the order of filter that will do 80 dB as a low pass
filter? And the Q of the components necessary to make the insertion loss
negligible at 160 meters?


Jim


"Richard Clark" wrote in message
...
On Wed, 24 Jan 2007 08:49:21 -0800, "RST Engineering"
wrote:

Why all this stuff about "high pass filters" and such. You are dealing
with
a spot frequency, not a band of frequencies. A simple parallel resonant
notch filter should do the job quite nicely and still pass everything from
DC to daylight except that spot frequency.

Hi Jim

There's not much more effort in completely covering a band of problems
with a band reject (high pass) filter. The original poster could
discover the NEXT broadcaster creating problems when he limited his
suppression to the first one. Who needs a chain of notch filters when
one would work as well for the entire band?

73's
Richard Clark, KB7QHC

RST Engineering wrote:
Because he's got a SINGLE frequency interfering with his station. To hell
with covering the entire band. A single parallel resonant network will do
something in the order of 80 dB of rejection if the L and C are at LEAST
something reasonable for Q.

Care to calculate the order of filter that will do 80 dB as a low pass
filter? And the Q of the components necessary to make the insertion loss
negligible at 160 meters?


Jim


Krist! Whatever was I thinking?

Yanno, if he even just sits back and thinks about it long enough, he
might be getting excited over his present problem for nothing!

Maybe if he just practiced a little Zen he could learn to actually enjoy it?

Many roads lead to the same destination--the high pass is but one ...

Regards,
JS

"RST Engineering" ) writes:
Because he's got a SINGLE frequency interfering with his station. To hell
with covering the entire band. A single parallel resonant network will do
something in the order of 80 dB of rejection if the L and C are at LEAST
something reasonable for Q.

Care to calculate the order of filter that will do 80 dB as a low pass
filter? And the Q of the components necessary to make the insertion loss
negligible at 160 meters?

At the very least, it's far easier to put in a single LC notch filter to
see what it does to the offending signal.

I was trying to think of things that could be done easily to determine
whether the problem is actually the transmitter or simply receiver overload.
One can easily assemble an LC circuit in the broadcast band with available
parts to try this out, while a high pass filter requires paying good
money for it and likely mail-ordering, or at the very least ordering
multiple coils to build up such a thing.

My first receiver was a cheap low end solid-state Hallicrafters in 1971,
and it overloaded terribly. I don't think anything could have been
done to fix it, but I know one time I took the parts list from the Handbook
for the high pass filter that was in there to solve the problem of AM
broadcast stations, and the parts store said they didn't have the
coils in stock, and they'd cost a pretty penny (certainly a pretty
penny for a 12 year old).

Michael VE2BVW

On Wed, 24 Jan 2007 17:50:56 -0800, "RST Engineering"
wrote:

Because he's got a SINGLE frequency interfering with his station.

He reported a single frequency, that does not limit the problem to a
single frequency. I already explained that.

Care to calculate the order of filter that will do 80 dB as a low pass
filter?

That is not particularly difficult, quite common in fact. Standard
engineering syllabus teaches us that you enjoy a 6dB/Octave or
10dB/Decade roll-off for each reactive element in a filter. I already
suggested a 6 or 8 pole filter which brings us up to your 80dB for an
entire band, much less a single frequency. Slam dunk simple.

I am quite sure that many here that are experienced in actual bench
work would nod in agreement that the better part of a project is
building the things around the electronics - like an enclosure,
connectors and such - than with the electronics. 8 off the shelf
items (actually 4 pairs) vs. 2 with one of the two needing to be
variable AND tuned? Is that such a major demand on the bench skills
of an amateur radio operator?

And the Q of the components necessary to make the insertion loss
negligible at 160 meters?

For receive? C'mon now. And 160M instead of the band he is
interested in, 80M? Anyone can contrive to fail, that's plug simple.
The next set of restrictions will have us going down the garden path
to build a crystal lattice filter for the sake of unneeded
astronomical Q and to achieve spectacularly low insertion loss - turn
up the RF gain.

The issue is moot with the probability the issue revolves around spurs
from corroded, weather beat connections. I have a buddy who suffered
identical issues from an AM station 1 mile away. He wire brushed poor
joints and solved the problem that filters couldn't solve.

73's
Richard Clark, KB7QHC