antenna noise reduction ideas
 

Hey group,


I build a PI network antenna tuner with 2 variable caps and an air
form coil. Is there a componant I can add to this device to reduce
noise from my random wire? I have heard a 1-1 transformer may help.

I have a few toroids with very high Al (79uH per hundred turns)
kicking around. Can I wind one of these to use a noise reducer?

any other suggestions to reduce noise?

can someone toss me a link to a howto?

thanks,

mike

mike wrote in message

form coil. Is there a componant I can add to this device to reduce
noise from my random wire? I have heard a 1-1 transformer may help.

I have a few toroids with very high Al (79uH per hundred turns)
kicking around. Can I wind one of these to use a noise reducer?


it depends upon what kind of noise you are fighting.
1) the single wire antenna might be picking up noise that is the your
receiver room. the most probable source is your PC. try switching off
the PC (and the one in the neighbouring rooms) to see if that effects
the noise. If PC is the source of noise, you will have to use a
shielded cable to get the antenna off your house. start the long wire
outside.
2) it might be electric discharge from flourescent lights. again, try
switching them out. the electric discharge can go a long way. there
might be little you can do about it except move the antenna away. look
for noisy water pumps and fan regulators (they use SCRs that create
noise).
3) receiver front-end. A poorly matched receiver might overload
itself. Turn off the RF amp (if you can) or try using a 200 ohms
potentiometer as an attenuator between the rx and the antenna. cut the
signal level with the attentuator and boost the audio gain.


single wires are a problem with electrical noise, what i would suggest
is use a coax from your receiver to your roof or some place where the
you can mount your antenna tuner. DONT use an antenna tuner between
the receiver and the coax. that way, it will convert the coax into a
part of the antenna and the sheild of the coax will pick up the noise.
ground the coax and both ends to ensure proper sheilding. get onto the
roof and move the wire around until you can null noise the most.
the other effective scheme might be to use two antennas. (a vertical
and a long wire). and connect them both together through a phasing
network that will cancel out the common signals. you will need to
adjust the phase and amplitude together to achieve a noise null. it is
tricky but it can be done. check the passing comment on wes hayward's
home page about his experience. (it is on the page where he describes
his current home setup).

- farhan

mike wrote in message

form coil. Is there a componant I can add to this device to reduce
noise from my random wire? I have heard a 1-1 transformer may help.

I have a few toroids with very high Al (79uH per hundred turns)
kicking around. Can I wind one of these to use a noise reducer?


it depends upon what kind of noise you are fighting.
1) the single wire antenna might be picking up noise that is the your
receiver room. the most probable source is your PC. try switching off
the PC (and the one in the neighbouring rooms) to see if that effects
the noise. If PC is the source of noise, you will have to use a
shielded cable to get the antenna off your house. start the long wire
outside.
2) it might be electric discharge from flourescent lights. again, try
switching them out. the electric discharge can go a long way. there
might be little you can do about it except move the antenna away. look
for noisy water pumps and fan regulators (they use SCRs that create
noise).
3) receiver front-end. A poorly matched receiver might overload
itself. Turn off the RF amp (if you can) or try using a 200 ohms
potentiometer as an attenuator between the rx and the antenna. cut the
signal level with the attentuator and boost the audio gain.


single wires are a problem with electrical noise, what i would suggest
is use a coax from your receiver to your roof or some place where the
you can mount your antenna tuner. DONT use an antenna tuner between
the receiver and the coax. that way, it will convert the coax into a
part of the antenna and the sheild of the coax will pick up the noise.
ground the coax and both ends to ensure proper sheilding. get onto the
roof and move the wire around until you can null noise the most.
the other effective scheme might be to use two antennas. (a vertical
and a long wire). and connect them both together through a phasing
network that will cancel out the common signals. you will need to
adjust the phase and amplitude together to achieve a noise null. it is
tricky but it can be done. check the passing comment on wes hayward's
home page about his experience. (it is on the page where he describes
his current home setup).

- farhan

mike wrote in
:

any other suggestions to reduce noise?

loop

mike wrote in
:

any other suggestions to reduce noise?

loop

If you are working at low frequencies, I have seen an idea using a very long
wire (say 4-5 wavelengths) at a low height above ground (say about 6 feet).
The antenna can be directive in it's long axis. It can help to reduce QRM
from a particular direction. Of course you need a fair bit of room...

Richard

mike wrote in message
...
Hey group,


I build a PI network antenna tuner with 2 variable caps and an air
form coil. Is there a componant I can add to this device to reduce
noise from my random wire? I have heard a 1-1 transformer may help.

I have a few toroids with very high Al (79uH per hundred turns)
kicking around. Can I wind one of these to use a noise reducer?

any other suggestions to reduce noise?

can someone toss me a link to a howto?

thanks,

mike

If you are working at low frequencies, I have seen an idea using a very long
wire (say 4-5 wavelengths) at a low height above ground (say about 6 feet).
The antenna can be directive in it's long axis. It can help to reduce QRM
from a particular direction. Of course you need a fair bit of room...

Richard

mike wrote in message
...
Hey group,


I build a PI network antenna tuner with 2 variable caps and an air
form coil. Is there a componant I can add to this device to reduce
noise from my random wire? I have heard a 1-1 transformer may help.

I have a few toroids with very high Al (79uH per hundred turns)
kicking around. Can I wind one of these to use a noise reducer?

any other suggestions to reduce noise?

can someone toss me a link to a howto?

thanks,

mike

On Thu, 25 Sep 2003 22:17:35 +0800, "Richard Hosking"
wrote:

If you are working at low frequencies, I have seen an idea using a very long
wire (say 4-5 wavelengths) at a low height above ground (say about 6 feet).
The antenna can be directive in it's long axis. It can help to reduce QRM
from a particular direction. Of course you need a fair bit of room...

Richard, back in the '80s we set up several of these for the SES for
poin-to-point operation from Perth to Carnarvon and Port Hedland.
They offer a huge number of positives for p2p and point-to-area.

There is a CCIR publication "Handbook on High-Frequency Directional
Antennae" published in 1966 which is very good background for anyone
into this area.

More specifically, there is a very specialised report from the
Communications Research Centre in Ottawa titled "Beverage Antennas for
HF Communications, Direction Finding and Over-the horizon Radars" (CRC
Report #1282 - August 1976). This gives in vol2 all sorts of
parameters for HF beverage-type antennae. Gain, takeoff angle,
beamwidth, impedance etc as a function of ground type/condition, wire
length, wire height above ground etc. One VERY good read.

Both are decades old, but the laws of physics and iononspheric
behaviour are pretty stable ;-)

On Thu, 25 Sep 2003 22:17:35 +0800, "Richard Hosking"
wrote:

If you are working at low frequencies, I have seen an idea using a very long
wire (say 4-5 wavelengths) at a low height above ground (say about 6 feet).
The antenna can be directive in it's long axis. It can help to reduce QRM
from a particular direction. Of course you need a fair bit of room...

Richard, back in the '80s we set up several of these for the SES for
poin-to-point operation from Perth to Carnarvon and Port Hedland.
They offer a huge number of positives for p2p and point-to-area.

There is a CCIR publication "Handbook on High-Frequency Directional
Antennae" published in 1966 which is very good background for anyone
into this area.

More specifically, there is a very specialised report from the
Communications Research Centre in Ottawa titled "Beverage Antennas for
HF Communications, Direction Finding and Over-the horizon Radars" (CRC
Report #1282 - August 1976). This gives in vol2 all sorts of
parameters for HF beverage-type antennae. Gain, takeoff angle,
beamwidth, impedance etc as a function of ground type/condition, wire
length, wire height above ground etc. One VERY good read.

Both are decades old, but the laws of physics and iononspheric
behaviour are pretty stable ;-)

On Fri, 26 Sep 2003 01:45:14 GMT, budgie
wrote:

(snip)

More specifically, there is a very specialised report from the
Communications Research Centre in Ottawa titled "Beverage Antennas for
HF Communications, Direction Finding and Over-the horizon Radars" (CRC
Report #1282 - August 1976). This gives in vol2 all sorts of
parameters for HF beverage-type antennae. Gain, takeoff angle,
beamwidth, impedance etc as a function of ground type/condition, wire
length, wire height above ground etc. One VERY good read.

First report cited at:
http://shekel.dgcp.crc.ca/web2/tramp...m/A15glkni.000