Crosstalk from ground?
 

Hi,

I just noticed that when I disconnect the ground from my 180
meters long beverage antenna signal levels drop a whole lot, but crosstalk
from a local broadcaster that would cover all of the MW band and a lot
both above and below almost completely disappears. I don't remember
reading about anything like this anywhere. What's going on?

The ground is just a iron rod that I drove half a meter into wet ground
about where I connect the antenna to the coaxial. I connect it directly to
the shield of the BNC connector about a meter above ground. Not elegant,
but that shouldn't cause crosstalk, should it?

My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

Crosstalk from ground?
 

"Ceriel Nosforit" wrote in message
...
Hi,

I just noticed that when I disconnect the ground from my 180
meters long beverage antenna signal levels drop a whole lot, but crosstalk
from a local broadcaster that would cover all of the MW band and a lot
both above and below almost completely disappears. I don't remember
reading about anything like this anywhere. What's going on?

The ground is just a iron rod that I drove half a meter into wet ground
about where I connect the antenna to the coaxial. I connect it directly to
the shield of the BNC connector about a meter above ground. Not elegant,
but that shouldn't cause crosstalk, should it?

My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.



You could have some rectification and creation of intermods going on at some
bad, corroded junction. Check the connections.

Yuri, K3BU.us

Crosstalk from ground?
 

Yuri Blanarovich wrote:
"Ceriel Nosforit" wrote:
My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

You could have some rectification and creation of intermods going on at some
bad, corroded junction. Check the connections.

That front end is so broad-banded that there is probably
no corrosion needed to generate intermod. I had an ICOM
2m handheld that was useless in downtown Phoenix while
mobile on a dual band mobile antenna. I suspect a notch
filter would be the way to go to reduce the intermod
while keeping full functionality of the Beverage.
--
73, Cecil http://www.w5dxp.com

Crosstalk from ground?
 

On Mar 11, 11:45 am, Ceriel Nosforit wrote:
Hi,

I just noticed that when I disconnect the ground from my 180
meters long beverage antenna signal levels drop a whole lot, but crosstalk
from a local broadcaster that would cover all of the MW band and a lot
both above and below almost completely disappears. I don't remember
reading about anything like this anywhere. What's going on?

The ground is just a iron rod that I drove half a meter into wet ground
about where I connect the antenna to the coaxial. I connect it directly to
the shield of the BNC connector about a meter above ground. Not elegant,
but that shouldn't cause crosstalk, should it?

My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

Crosstalk from ground?
 

On Mar 11, 11:45 am, Ceriel Nosforit wrote:
Hi,

I just noticed that when I disconnect the ground from my 180
meters long beverage antenna signal levels drop a whole lot, but crosstalk
from a local broadcaster that would cover all of the MW band and a lot
both above and below almost completely disappears. I don't remember
reading about anything like this anywhere. What's going on?

The ground is just a iron rod that I drove half a meter into wet ground
about where I connect the antenna to the coaxial. I connect it directly to
the shield of the BNC connector about a meter above ground. Not elegant,
but that shouldn't cause crosstalk, should it?

My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

You are probably getting intermod from the local station. Obviously
removing the ground made the antenna perform poorer for the desire as
well as the undesired frequencies. My guess is that there was a
considerable change in impedance of the antenna. Assuminng the radio
was a reasonable match for the antenna with the ground stake connected
the radio may well look like a short tot the antenna now.

Crosstalk from ground?
 

On Sun, 11 Mar 2007 10:30:53 -0700, JIMMIE wrote:

On Mar 11, 11:45 am, Ceriel Nosforit wrote:
Hi,

I just noticed that when I disconnect the ground from my 180
meters long beverage antenna signal levels drop a whole lot, but crosstalk
from a local broadcaster that would cover all of the MW band and a lot
both above and below almost completely disappears. I don't remember
reading about anything like this anywhere. What's going on?

The ground is just a iron rod that I drove half a meter into wet ground
about where I connect the antenna to the coaxial. I connect it directly to
the shield of the BNC connector about a meter above ground. Not elegant,
but that shouldn't cause crosstalk, should it?

My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

You are probably getting intermod from the local station. Obviously
removing the ground made the antenna perform poorer for the desire as
well as the undesired frequencies. My guess is that there was a
considerable change in impedance of the antenna. Assuminng the radio
was a reasonable match for the antenna with the ground stake connected
the radio may well look like a short tot the antenna now.

Ah, alright. I gotta look into that now that I know what I'm looking for.
I've got some ideas about what the problem could be too. Thanks a bundle! =)

--
Nos

Crosstalk from ground?
 

On Sun, 11 Mar 2007 17:06:00 +0000, Cecil Moore wrote:

Yuri Blanarovich wrote:
"Ceriel Nosforit" wrote:
My receiver is an Icom-R5 handheld scanner, 0.150 to 1300MHz continuous.

You could have some rectification and creation of intermods going on at some
bad, corroded junction. Check the connections.

That front end is so broad-banded that there is probably
no corrosion needed to generate intermod. I had an ICOM
2m handheld that was useless in downtown Phoenix while
mobile on a dual band mobile antenna. I suspect a notch
filter would be the way to go to reduce the intermod
while keeping full functionality of the Beverage.

The entire ground rod is covered with rust. I checked that there was a
connection with a multimeter, but it could be that's not enough of a check.


I don't think I could make enough band-stop filters to cover all crosstalk
I'm hearing. I'd fill up the greenhouse, for sure!

The R5 has an attenuation function that sometimes is a bit of help...
Maybe the entire receiver is getting overloaded, causing some sort of
overmodulation? The signals are pretty strong after all...

Thanks for the replies!

--
Nos

Crosstalk from ground?
 

Most handheld receivers are designed to be used with a very short duckie
antenna. The front end is totally overwhelmed if connected to an antenna
of reasonable size. Besides having a whole lot of extra gain to
accommodate the short antenna, compromises have to be made in the front
end filtering because of the unit's small physical size. Keeping the
power consumption low further limits the dynamic range of the stages.

I have an Icom R1 and it's full of crossmod birdies even with its own
antenna. When connected to a real antenna, it's totally unusable, the
front end being overloaded and blocked by just about anything. I have to
use a 20 or more dB pad if I ever connect it to a decent antenna. I'll
bet a substantial attenuation pad would do wonders for yours.

Roy Lewallen, W7EL

Ceriel Nosforit wrote:
. . .
The R5 has an attenuation function that sometimes is a bit of help...
Maybe the entire receiver is getting overloaded, causing some sort of
overmodulation? The signals are pretty strong after all...

Thanks for the replies!

Crosstalk from ground?
 

On Sun, 11 Mar 2007 15:31:19 -0700, Roy Lewallen wrote:

Most handheld receivers are designed to be used with a very short duckie
antenna. The front end is totally overwhelmed if connected to an antenna
of reasonable size. Besides having a whole lot of extra gain to
accommodate the short antenna, compromises have to be made in the front
end filtering because of the unit's small physical size. Keeping the
power consumption low further limits the dynamic range of the stages.

I have an Icom R1 and it's full of crossmod birdies even with its own
antenna. When connected to a real antenna, it's totally unusable, the
front end being overloaded and blocked by just about anything. I have to
use a 20 or more dB pad if I ever connect it to a decent antenna. I'll
bet a substantial attenuation pad would do wonders for yours.

Roy Lewallen, W7EL

Hm. I _thought_ it looked kinda funny having such a puny receiver for such
a long antenna...

Thanks for the tip on the attenuator. I'll look into that. =)

--
Nos

Crosstalk from ground?
 

On Mon, 12 Mar 2007 19:05:27 +0200, Ceriel Nosforit wrote:

On Sun, 11 Mar 2007 15:31:19 -0700, Roy Lewallen wrote:

Most handheld receivers are designed to be used with a very short duckie
antenna. The front end is totally overwhelmed if connected to an antenna
of reasonable size. Besides having a whole lot of extra gain to
accommodate the short antenna, compromises have to be made in the front
end filtering because of the unit's small physical size. Keeping the
power consumption low further limits the dynamic range of the stages.

I have an Icom R1 and it's full of crossmod birdies even with its own
antenna. When connected to a real antenna, it's totally unusable, the
front end being overloaded and blocked by just about anything. I have to
use a 20 or more dB pad if I ever connect it to a decent antenna. I'll
bet a substantial attenuation pad would do wonders for yours.

Roy Lewallen, W7EL

Hm. I _thought_ it looked kinda funny having such a puny receiver for such
a long antenna...

Thanks for the tip on the attenuator. I'll look into that. =)

An update, for the sake of archiving if nothing else; I made a high-pass
filter of nothing but a varicap at its lowest capacitance and now the 80
meter band is a joy listening to. I decided to try this since I noticed
that signals were much more powerful at lower frequencies, and suspected
that getting rid of those would improve my reception.

I did try various types of attenuation, but I wasn't quite happy with the
result. The high-pass filter is better. I'm going to make a low-pass
as well to put in series to see if I can improve reception further, and
look into better high-pass filters.

--
Nos