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Old February 1st 05, 03:24 AM
 
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Default Question about noise

Before leaving the topic of noise and quiet receivers, I have a
question. Tonight I was listening to a couple of Spanish language
stations on 6185 and 6125 khz. On the Drake R8B, there was a background
noise behind these signals and in fact behind most of the signals on
this particular band. (It sounds like atmospheric noise--a vague, hissy
sound that fades in and out a bit, just as the signal fades in and
out). On the other hand, when I listened to these two stations on the
Lowe HF-150, there was almost no trace of the noise. Both receivers
were connected to the same antenna. I experimented with different power
sources. Powering the R8B from it's internal power supply vs. an
external power supply didn't have any effect on what I heard.

This noise isn't always there, although I've heard it before. What
puzzles me is the Lowe receiver's failure to be affected by it. Why was
it interfering with the Drake, but not the Lowe? The receivers were
sitting right next to each other (I tried separating them, just for the
heck of it, but it made no difference.)

Any thoughts?

Steve


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Old February 1st 05, 04:16 AM
ShortwaveMan
 
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I'd hazard a guess that the digital circuitry in one radi does not exist in
the other and that circuitry is causing some noise in the other receiver. On
the other hand, maybe the sensitivity of one receiver is different than the
other. was the gain on both receivers set the same ?

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Before leaving the topic of noise and quiet receivers, I have a
question. Tonight I was listening to a couple of Spanish language
stations on 6185 and 6125 khz. On the Drake R8B, there was a background
noise behind these signals and in fact behind most of the signals on
this particular band. (It sounds like atmospheric noise--a vague, hissy
sound that fades in and out a bit, just as the signal fades in and
out). On the other hand, when I listened to these two stations on the
Lowe HF-150, there was almost no trace of the noise. Both receivers
were connected to the same antenna. I experimented with different power
sources. Powering the R8B from it's internal power supply vs. an
external power supply didn't have any effect on what I heard.

This noise isn't always there, although I've heard it before. What
puzzles me is the Lowe receiver's failure to be affected by it. Why was
it interfering with the Drake, but not the Lowe? The receivers were
sitting right next to each other (I tried separating them, just for the
heck of it, but it made no difference.)

Any thoughts?

Steve



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Old February 1st 05, 09:24 AM
jimg
 
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jimg wrote:

first disconnect the antenna from both receivers and short the antenna
terminals...turn up the rf gain and audio...both real quiet, i bet?
good.

then it's from the antenna-ground-rf front end combo... are you using
the 50ohm input on both, or the long wire input?

lets say, the long wire inputs....well, i doubt they have the same
input impedance...if your not using coax and don't have a reasonable
impedance match, then the antenna's are going to act very
diffferently...( how are they grounded? tied together? hmmmm)

if your using the 50 ohm inputs, have a well designed antenna with
good matching, then we have to discuss the reactive component at the
antenna input...and even the selectivity of the first if stage....
you really want to know, we'd have to take 'em into a lab with very
controlled conditions to trace out the diff...but it's not
magik...just complicated

wrote:

Before leaving the topic of noise and quiet receivers, I have a
question. Tonight I was listening to a couple of Spanish language
stations on 6185 and 6125 khz. On the Drake R8B, there was a background
noise behind these signals and in fact behind most of the signals on
this particular band. (It sounds like atmospheric noise--a vague, hissy
sound that fades in and out a bit, just as the signal fades in and
out). On the other hand, when I listened to these two stations on the
Lowe HF-150, there was almost no trace of the noise. Both receivers
were connected to the same antenna. I experimented with different power
sources. Powering the R8B from it's internal power supply vs. an
external power supply didn't have any effect on what I heard.

This noise isn't always there, although I've heard it before. What
puzzles me is the Lowe receiver's failure to be affected by it. Why was
it interfering with the Drake, but not the Lowe? The receivers were
sitting right next to each other (I tried separating them, just for the
heck of it, but it made no difference.)

Any thoughts?

Steve


Are you saying the noise could also be heard on the Lowe but it was just
lower?

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jimg
Oregon
USA
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Old February 1st 05, 12:57 PM
[email protected]
 
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Thanks for all of the input guys.

Although the noise sounded like atsmopheric noise, part of me thought
it might be something else...and I turned out to be right. After
staying up half the night, I discovered a laser printer that had been
left turned on in a different room. I turned the printer off, not
really thinking that it would be the cause of the noise on the Drake.
But when I then walked into the room where the Drake sits, it was on
and there wasn't a trace of noise. Just for the heck of it, I had to
turn the printer back on to see if the noise returned...and it did.

It's amazing to me that the Drake could have been affected so much more
severely than the Lowe by the noise from this printer, but now I'm just
glad that the noise is gone. Everything sounds the way it should now.
Steve



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