sjx305
Newbie
Hi! I have an ICOM IC-R2500 connected to a long wire (20Mtr braided steel core, plastic coated washing line) terminated at ground level outside through a 9:1 UNUN Transformer, grounded via a 4ft solid earth rod in soil less than 2ft from the termination box.
something similar to RG6 coax (solid copper conductor, foam dilectric, twin shield - braid and foil)
runs from termination box around my house and up to second floor level into my radio room, about 10 meters or so.
I have a CB (Midland Alan 78Plus multi) connected via RG213/U to an MFJ-993B auto tuner. This in turn is connected to a 5/8 antenna outside via RG213/U on a short run about 5 Meters across my outer upper floor wall.
The 2 coax's only get close when going through some round conduit to get from outside to inside, once outside they run the 3ish meters across my outer wall in parallel about 18 inches apart, then the RG213 goes up a 6 foot pole to the 5/8 artificial grounded antenna and the RG6 type goes down to almost ground level and continues its journey round the back of the house to the termination box with the UNUN inside it.
At this point I am beginning to imagine that the 2 braids are acting like a big di-pole on my outer wall although never actually physically connected inside or outside the house.
The 2 cables inside the house are at least 22 inches apart from each other at their closest point. The tuner sits on a shelf away from the Icom and the CB sits under the shelf, well away from the Icom. I never use both at the same time. If Icom is in use, CB is turned off and power supply switched off. However the tuner has a power supply that is always on when the PC, monitor and Icom are on though the tuner can be turned off on its front panel.
I am trying to give as much information as possible.. Here is the phenomenon..
If the tuner is turned off I can tune the Icom as normal and experience all the usual noise, signals and broadcasts as you would expect from a longwire. However.. I noticed that when tuned to something on 4625Khz (you maybe know what it is) it was faint in the background with a lot of noise over it. By sheer boredom I decided to turn on the tuner ( it always resets to no C and no L on the CB side ) and as such is in a bypass mode. It was when I turned it on I heard a static click on my Icom and the noise dropped revealing a strong 4625Khz signal
?
This shouldn't be possible?? So I turned it off again and the noise 'glided' back into place like a cap was discharging inside the tuner. Turn it on, noise went away.
I experimented by tuning to 3, 4, 5, 6, 7 MHz each time turning tuner on , then off and sure enough noise either glided in, or out of the received signal.
My question is, how on earth is this possible, and what is happening ?
Its like the tuner is shifting the noise and interference further up the tuning range when turned on and allowing it to glide back in when turned off even though it is not connected to the Icom in any way, and is not using any components as its in bypass mode at switch on. Im confused.
Using the LC switches does have an audible effect on noise etc.. through the icom.. but its not connected to the tuner!
Is it doing something to the properties of the 213 cable which is passing its effect on to the RG6 cable or is it doing something to the 5/8 antenna which is affecting the longwire outside through an air-gap?
Any ideas, suggestions, discussions would be more than welcome.
As this isn't an equipment specific question I posted here as its more an effect of equipment maybe other people have noticed? Thank you
something similar to RG6 coax (solid copper conductor, foam dilectric, twin shield - braid and foil)
runs from termination box around my house and up to second floor level into my radio room, about 10 meters or so.
I have a CB (Midland Alan 78Plus multi) connected via RG213/U to an MFJ-993B auto tuner. This in turn is connected to a 5/8 antenna outside via RG213/U on a short run about 5 Meters across my outer upper floor wall.
The 2 coax's only get close when going through some round conduit to get from outside to inside, once outside they run the 3ish meters across my outer wall in parallel about 18 inches apart, then the RG213 goes up a 6 foot pole to the 5/8 artificial grounded antenna and the RG6 type goes down to almost ground level and continues its journey round the back of the house to the termination box with the UNUN inside it.
At this point I am beginning to imagine that the 2 braids are acting like a big di-pole on my outer wall although never actually physically connected inside or outside the house.
The 2 cables inside the house are at least 22 inches apart from each other at their closest point. The tuner sits on a shelf away from the Icom and the CB sits under the shelf, well away from the Icom. I never use both at the same time. If Icom is in use, CB is turned off and power supply switched off. However the tuner has a power supply that is always on when the PC, monitor and Icom are on though the tuner can be turned off on its front panel.
I am trying to give as much information as possible.. Here is the phenomenon..
If the tuner is turned off I can tune the Icom as normal and experience all the usual noise, signals and broadcasts as you would expect from a longwire. However.. I noticed that when tuned to something on 4625Khz (you maybe know what it is) it was faint in the background with a lot of noise over it. By sheer boredom I decided to turn on the tuner ( it always resets to no C and no L on the CB side ) and as such is in a bypass mode. It was when I turned it on I heard a static click on my Icom and the noise dropped revealing a strong 4625Khz signal
?This shouldn't be possible?? So I turned it off again and the noise 'glided' back into place like a cap was discharging inside the tuner. Turn it on, noise went away.
I experimented by tuning to 3, 4, 5, 6, 7 MHz each time turning tuner on , then off and sure enough noise either glided in, or out of the received signal.
My question is, how on earth is this possible, and what is happening ?
Its like the tuner is shifting the noise and interference further up the tuning range when turned on and allowing it to glide back in when turned off even though it is not connected to the Icom in any way, and is not using any components as its in bypass mode at switch on. Im confused.
Using the LC switches does have an audible effect on noise etc.. through the icom.. but its not connected to the tuner!
Is it doing something to the properties of the 213 cable which is passing its effect on to the RG6 cable or is it doing something to the 5/8 antenna which is affecting the longwire outside through an air-gap?
Any ideas, suggestions, discussions would be more than welcome.
As this isn't an equipment specific question I posted here as its more an effect of equipment maybe other people have noticed? Thank you
