Paul,
You still need to be more specific:
What is the modulating frequency and deviation of the FM signal? Is it the
modulation frequency a single tone or noise-like?. What is the IF bandwidth
of the FM receiver? What is the sweep rate of the interfering signal? We'll
assume the AM signal is modulated with the same frequency at 100%
modulation.

In general, the CW signal would be least intrusive for a given sweep rate
because it's energy is only in the IF of the receiver for a period of time
equal to RXbw/sweeprate. If this time is small compared to the inverse of
the post detection (audio) bandwidth, it might be inaudible. If the
modulation is noise-like and the FM modulation index is high, the
interference will be worse and longer in duration. If the FM modulation
frequency is high, the modulation index is low, and the sweep rate is low,
it could sound like 3 seperate signals sweeping through the passband (AM
would be similar to this last case).

Joe
W3JDR


"Paul Burridge" wrote in message
...
On 17 Feb 2004 04:56:57 GMT, (Avery Fineman)
wrote:

In article , Paul Burridge
writes:

ISTR.......
(through the mists of time) that the excessive bandwidth of an AM
transmission signal can interfere with the reception of a NBFM signal,
though the converse is not true. Can anyone confirm this (or else
flatly deny it/affirm it)?

Paul, you need to be a bit more specific on the above.

Thanks, guys. I think you covered what I wanted to know...

Now I have another question on the same subject. Imagine if you will,
a NBFM recieiver, set to listen on one particular channel. Now
consider 3 seperate sweep transmitters located say 100yds away. Each
sweeps slowly across the band which encompasses the RX's receive
channel.
Sweep transmitter 1 puts out only an unmodulated carrier wave. STX 2
puts out an FM signal of the same power level; STX 3 puts out an AM
signal of the same power. Assume the extent of modulation is likewise
identical - or as identical as it can be given different classes. Now,
which of the three TXs is going to 'take over' the RX channel for the
longest time? IOW, which of the TX signals appears broadest to the FM
RX?

Thanks,

p.
--

The BBC: Licensed at public expense to spread lies.

In article , Paul Burridge
writes:

Now I have another question on the same subject. Imagine if you will,
a NBFM recieiver, set to listen on one particular channel. Now
consider 3 seperate sweep transmitters located say 100yds away. Each
sweeps slowly across the band which encompasses the RX's receive
channel.
Sweep transmitter 1 puts out only an unmodulated carrier wave. STX 2
puts out an FM signal of the same power level; STX 3 puts out an AM
signal of the same power. Assume the extent of modulation is likewise
identical - or as identical as it can be given different classes. Now,
which of the three TXs is going to 'take over' the RX channel for the
longest time? IOW, which of the TX signals appears broadest to the FM
RX?

Whichever signal is strongest is going to "take over."

You CAN determine this yourself, given some frequencies, RF output
levels, approximate gain/loss of the antennas, and the selectivity
(bandwidth) of the receiver and the modulation indexes of the
transmitters. Piece of cake.

Might I suggest you walk slowly away from the interfering RF fields
to avoid ionization the neurons? Any more?

Len Anderson
retired (from regular hours) electronic engineer entity

...and headed back to the Mother Ship...

In article , Paul Burridge
writes:

Now I have another question on the same subject. Imagine if you will,
a NBFM recieiver, set to listen on one particular channel. Now
consider 3 seperate sweep transmitters located say 100yds away. Each
sweeps slowly across the band which encompasses the RX's receive
channel.
Sweep transmitter 1 puts out only an unmodulated carrier wave. STX 2
puts out an FM signal of the same power level; STX 3 puts out an AM
signal of the same power. Assume the extent of modulation is likewise
identical - or as identical as it can be given different classes. Now,
which of the three TXs is going to 'take over' the RX channel for the
longest time? IOW, which of the TX signals appears broadest to the FM
RX?

Whichever signal is strongest is going to "take over."

You CAN determine this yourself, given some frequencies, RF output
levels, approximate gain/loss of the antennas, and the selectivity
(bandwidth) of the receiver and the modulation indexes of the
transmitters. Piece of cake.

Might I suggest you walk slowly away from the interfering RF fields
to avoid ionization the neurons? Any more?

Len Anderson
retired (from regular hours) electronic engineer entity

...and headed back to the Mother Ship...