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Old September 1st 14, 08:00 AM posted to rec.radio.shortwave,rec.radio.info
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 88
Default Phone line as SW antenna [12-Jul-06]

[Last modified 12-Jul-06]

The latest version of this file can be accessed via my web page at:
http://www.rdrop.com/users/billmc

Phone line as SW antenna
Bill McFadden


Changes preceded by "|".

WARNINGS AND DISCLAIMERS

Connecting unapproved devices to phone lines may be illegal in your area.
Telephone lines present a potential shock hazard. Do not use this antenna
for transmitting. Use at your own risk.


INTRODUCTION

This article describes how to use a phone line as a shortwave receiving
antenna. Performance will vary depending on the kind of phone line you
have. Overhead lines usually make okay antennas, while underground lines
| usually don't. Phone lines carrying DSL service may be unsuitable because
| DSL operates over a wide spectrum. A phone line antenna will generally
pick up more power line noise than a dedicated antenna, so don't expect to
| use it for DX work. Nevertheless, I found that it outperformed the
| telescopic whip antennas built into many portables.

A reader sent in this suggestion: If you're concerned about connecting
the phone line directly to the receiver, try wrapping the phone cord
several times around the receiver's telescopic whip antenna instead.
Performance may not be as good as a direct connection, but it will
probably be better than the whip antenna by itself.

Someone else wrote asking about lightning protection. I haven't thought
much about it because thunderstorms are rare in my area. Most phone lines
have lightning arrestors on them where they enter the house, but the
lightning arrestors may pass enough energy during a lightning strike
damage a receiver. My suggestion is to disconnect the antenna when not in
use if you experience frequent thunderstorms.


HOW TO DO IT

The simplest connection is a single capacitor between the phone line and
receiver. The capacitor eliminates all phone line voltages, including
| ringing, so that they will not harm the receiver. The capacitor should
| be rated 250 volts or higher.


Phone line RF connector
red .01 uF center cond. / \
or o--------||------------------------------|-o | To receiver
green \ /
50 ohm coax |
ground |
or o------------------------------------------+
N.C. shield


N.C. = no connect. I originally connected the phone line ground (yellow
wire) to this terminal, but reception was better without it (if you do
this, play it safe and put a .01 uF capacitor in series). If another
ground is available, you can connect it to this terminal.

If you are picking up local AM or FM radio stations on the shortwave
bands, it is likely that your receiver is overloaded. Inexpensive and
portable receivers usually lack the filtering needed to eliminate this
interference, but you can make your own filters. Filters can also be
| purchased from shortwave dealers (see below for recommendations).

A high-pass filter can be used to remove signals below the shortwave
bands. It rejects interference from local AM stations and presents a high
impedance to the phone line at audio frequencies so that the phone line
remains balanced.

A low-pass filter can be used to remove signals above the shortwave bands.
It rejects interference from FM and TV stations, as well as VHF 2-way
radio transmitters. If you use both filters, connect the output of the
first filter to the input of the second (don't forget to connect their
ground terminals together). It doesn't matter which filter is connected
first.

These filters also work well with random wire antennas. Just connect the
antenna in place of the phone line.

The filter(s) should be connected to the phone line in this manner:


Phone line RF connector
red -------- center cond. / \
or o----| |--------------------------|-o | To receiver
green | | \ /
| FILTER | 50 ohm coax |
ground | | |
or o----| |----------------------------+
N.C. -------- shield


| RECOMMENDED FILTERS
|
| If you don't want to make your own filters, the following have good
| performance, are well-built and affordable:
|
| Model 400 BCB interference filter (3.5 MHz highpass)
|
http://www.iceradioproducts.com/filtersrf.html#bcb
|
| Model 420 HF lowpass filter (30 MHz lowpass)
| http://www.iceradioproducts.com/filtersrf.html#3
| (scroll down a bit to see the model 420)
|
| If you have a random-wire antenna, the following unit will provide
| impedance matching and lightning protection (connect antenna to 450-ohm
| terminal):
|
| Model 182A beverage matching unit
| http://www.iceradioproducts.com/reconly.html#Beverage Matching


FILTER PLANS

The original credit for the high-pass and low-pass filters goes to Paul
Blumstein and John Shalamskas, respectively. Edited versions of their
articles are included he


Date: 09 Jan 91 00:54:08 GMT
From: (Paul Blumstein)
Subject: BC Band Hi-Pass Filter

The following ascii-schematic diagram is a high pass filter that will
filter out Broadcast Band (MW) stations. I found it a great boon to my
shortwave listening since local MW stations overload my ATS-803A front
end & appear in SW, especially with a long antenna.

If you remember my antenna saga, I went from 50 feet to 150 feet & had
overload problems causing me to cut back to 50 feet. (Even at 50 feet,
I still have some MW interference). I took the advice of Gary Coffman
and looked up filters in the ARRL Handbook. With the filter in place, I
intend to try to increase my antenna length again.

Anywho, here is the filter, for interested parties.


--------||---+----||-----+----||-----------
} }
{ {
} }
-------------+-----------+-----------------

The outer capacitors are 1500 pf ceramic disks.
The inner capacitor is 820 pf ceramic disk.
The squiggly things are coils (two total). Each one is 2.7 uh.
(a close value will do).


Date: 12 Jan 91 00:44:25 GMT
From:
(William K. McFadden)
Subject: BC Band Hi-Pass Filter

I built the filter that Paul Blumstein posted recently and measured it
on a gain-phase analyzer. Here are its characteristics:

100 kHz -120dB
500 kHz -68dB
1000 kHz -38dB
1600 kHz -15dB
2100 kHz -3dB

The source and load impedances were 50 ohms. Because the filter has
five elements, the attenuation is 30dB per octave. The measurements
confirmed this.

This filter seems to be a good compromise between interference
attenuation and passband response. There is very little attenuation in
the 120m band and above. It could use a little more attenuation at the
upper end of MW, which could be done with more stages or a higher cutoff
frequency. Alternatively, you could build two of these filters and put
them in series. (Since two 1500pF capacitors in series are really
750pF, you could eliminate one cap.)

Just for fun, I put 470 ohms in series with the input to see how the
filter performed with an antenna mismatch. The response was:

100 kHz -105dB
500 kHz -60dB
1000 kHz -35dB
1600 kHz -15dB
2300 kHz -3dB

These figures are normalized to the passband response of -15dB, which is
due to the impedance mismatch between the source and load and would have
been there without the filter. Hence, the filter works almost as well
in spite of the mismatch, which is good news to those who use long-wire
antennas.


Date: 22 Apr 92 08:59:33 GMT
From:
(John Shalamskas)
Subject: Construction of filters for SW reception

Several people have asked for construction details of the filters I
built for my DX-440.

The high-pass filter helped some, but in my location the VHF/UHF
broadcasters are also causing problems. So, I dug out the ARRL handbook
and chose a 7-element Chebyshev low-pass design that is -3 dB at 35 MHz,
-20 dB at 43 MHz, and -50 dB at 64 MHz (all calculated; it works well in
practice!)


LOW-PASS FILTER (Rejects FM, TV, etc.)

0.36 uH 0.42 uH 0.36 uH
signal -------+--UUU--+--UUUUU--+--UUU--+------- signal
| | | |
82 ___ 180___ 180___ ___ 82
pF --- pF--- pF--- --- pF
shield | | | | shield
braid -------+-------+----+----+-------+------- braid
|
chassis ground


I had to do a little more improvising at this point. I used .33 uH
instead of .36, and .66 uH instead of .42, but it works fine.

The 5-lug terminal strips were perfect for these circuits, since there
are 4 lugs plus a grounded lug. All "ground" connections go to the lug
that is mounted to the chassis, and the other 4 lugs are used for each
of the connections on the signal line. One terminal strip is used per
filter. Since both filters were necessary to clean up the hash, I am
going to put them both into one box when I get the time.

The proper way to connect them is in series, i.e.

signal in ------- filter 1 -------- filter 2 -------- signal out

There is no difference between ends. They are "bilateral" which means
you can't possibly hook them up backwards. (In the above schematics,
left and right ends are interchangeable.)


COIL WINDING

You can make the coils yourself using this formula:

L = 0.2 * B^2 * N^2 / (3B + 9A + 10C)

L is the inductance, in uH
A is the length of the coil, in inches
B is the mean diameter of the coil, in inches
C is the diameter of the wire, in inches
N is the number of turns

For small wire, you can assume C = 0.


PARTS SOURCE

Parts for the filters can be obtained from the following source:
http://www.digi-key.com/

--- end ---

--
Bill McFadden http://www.rdrop.com/users/billmc
CAUTION: Don't look into laser beam with remaining eye.
  #2   Report Post  
Old September 1st 14, 01:01 PM
Senior Member
 
First recorded activity by RadioBanter: Jan 2011
Posts: 390
Default

Why not use a antenna as a antenna..

Too many LAZY hams out there that wants to get something for nothing!
__________________
No Kings, no queens, no jacks, no long talking washer women...
  #3   Report Post  
Old September 1st 14, 03:43 PM posted to rec.radio.shortwave
external usenet poster
 
First recorded activity by RadioBanter: Mar 2008
Posts: 618
Default Phone line as SW antenna [12-Jul-06]

On Mon, 1 Sep 2014, Channel Jumper wrote:


Why not use a antenna as a antenna..

Too many LAZY hams out there that wants to get something for nothing!

This is rec.radio.shortwave, not one of the rec.radio.amateur.*
newsgroups.

It's not about ham radio (and ham radio is of course more than the
shortwave bands). It's just a reasonable short name for radio receiving
DXing. Which means it includes scanner listening (though there is a
newsgroup or two for that), and AM broadcast band DXing, and FM broadcast
band DXing, listening to shortwave broadcast, and monitoring shortwave
utility stations. It even includes listening to the ham bands.

When I was a kid, everyone knew that "swling" might be broader than the
actual shortwave bands, and this is shorthand for this.

The newsgroup is not intended for talking about transmtting on the ham
bands, or anything related to licensed ham activity (though there's
probably some slip room to point people if they ask about how to get a ham
license). It's not intended for politics even if it's heard on the radio.
It's not intended for everyday radio listening. And it's not for
off-topic posts about movies or whatever, which we certainly suffered from
at one point, and some of that still continues today with the village
idiot spewing whatever into this newsgroup.

So this has nothing to do with "cheap hams", and again, why is it that
every time I see "channel jumper" I think you must have previously been a
CB'er? You spout the talk, yet the lack of depth too often indicates
otherwise.

Michael

  #4   Report Post  
Old September 1st 14, 04:57 PM
Senior Member
 
First recorded activity by RadioBanter: Jan 2011
Posts: 390
Default

Quote:
Originally Posted by Michael Black[_2_] View Post
On Mon, 1 Sep 2014, Channel Jumper wrote:


Why not use a antenna as a antenna..

Too many LAZY hams out there that wants to get something for nothing!

This is rec.radio.shortwave, not one of the rec.radio.amateur.*
newsgroups.

It's not about ham radio (and ham radio is of course more than the
shortwave bands). It's just a reasonable short name for radio receiving
DXing. Which means it includes scanner listening (though there is a
newsgroup or two for that), and AM broadcast band DXing, and FM broadcast
band DXing, listening to shortwave broadcast, and monitoring shortwave
utility stations. It even includes listening to the ham bands.

When I was a kid, everyone knew that "swling" might be broader than the
actual shortwave bands, and this is shorthand for this.

The newsgroup is not intended for talking about transmtting on the ham
bands, or anything related to licensed ham activity (though there's
probably some slip room to point people if they ask about how to get a ham
license). It's not intended for politics even if it's heard on the radio.
It's not intended for everyday radio listening. And it's not for
off-topic posts about movies or whatever, which we certainly suffered from
at one point, and some of that still continues today with the village
idiot spewing whatever into this newsgroup.

So this has nothing to do with "cheap hams", and again, why is it that
every time I see "channel jumper" I think you must have previously been a
CB'er? You spout the talk, yet the lack of depth too often indicates
otherwise.

Michael
Aye Rodger - that is a big 10-4
__________________
No Kings, no queens, no jacks, no long talking washer women...
  #5   Report Post  
Old September 1st 14, 07:46 PM posted to rec.radio.shortwave
external usenet poster
 
First recorded activity by RadioBanter: Oct 2013
Posts: 2
Default Phone line as SW antenna [12-Jul-06]

On Monday, September 1, 2014 10:00:05 AM UTC+3, William Mcfadden wrote:
[Last modified 12-Jul-06]



The latest version of this file can be accessed via my web page at:

http://www.rdrop.com/users/billmc



Phone line as SW antenna

Bill McFadden





Changes preceded by "|".



WARNINGS AND DISCLAIMERS



Connecting unapproved devices to phone lines may be illegal in your area.

Telephone lines present a potential shock hazard. Do not use this antenna

for transmitting. Use at your own risk.





INTRODUCTION



This article describes how to use a phone line as a shortwave receiving

antenna. Performance will vary depending on the kind of phone line you

have. Overhead lines usually make okay antennas, while underground lines

| usually don't. Phone lines carrying DSL service may be unsuitable because

| DSL operates over a wide spectrum. A phone line antenna will generally

pick up more power line noise than a dedicated antenna, so don't expect to

| use it for DX work. Nevertheless, I found that it outperformed the

| telescopic whip antennas built into many portables.



A reader sent in this suggestion: If you're concerned about connecting

the phone line directly to the receiver, try wrapping the phone cord

several times around the receiver's telescopic whip antenna instead.

Performance may not be as good as a direct connection, but it will

probably be better than the whip antenna by itself.



Someone else wrote asking about lightning protection. I haven't thought

much about it because thunderstorms are rare in my area. Most phone lines

have lightning arrestors on them where they enter the house, but the

lightning arrestors may pass enough energy during a lightning strike

damage a receiver. My suggestion is to disconnect the antenna when not in

use if you experience frequent thunderstorms.





HOW TO DO IT



The simplest connection is a single capacitor between the phone line and

receiver. The capacitor eliminates all phone line voltages, including

| ringing, so that they will not harm the receiver. The capacitor should

| be rated 250 volts or higher.





Phone line RF connector

red .01 uF center cond. / \

or o--------||------------------------------|-o | To receiver

green \ /

50 ohm coax |

ground |

or o------------------------------------------+

N.C. shield





N.C. = no connect. I originally connected the phone line ground (yellow

wire) to this terminal, but reception was better without it (if you do

this, play it safe and put a .01 uF capacitor in series). If another

ground is available, you can connect it to this terminal.



If you are picking up local AM or FM radio stations on the shortwave

bands, it is likely that your receiver is overloaded. Inexpensive and

portable receivers usually lack the filtering needed to eliminate this

interference, but you can make your own filters. Filters can also be

| purchased from shortwave dealers (see below for recommendations).



A high-pass filter can be used to remove signals below the shortwave

bands. It rejects interference from local AM stations and presents a high

impedance to the phone line at audio frequencies so that the phone line

remains balanced.



A low-pass filter can be used to remove signals above the shortwave bands.

It rejects interference from FM and TV stations, as well as VHF 2-way

radio transmitters. If you use both filters, connect the output of the

first filter to the input of the second (don't forget to connect their

ground terminals together). It doesn't matter which filter is connected

first.



These filters also work well with random wire antennas. Just connect the

antenna in place of the phone line.



The filter(s) should be connected to the phone line in this manner:





Phone line RF connector

red -------- center cond. / \

or o----| |--------------------------|-o | To receiver

green | | \ /

| FILTER | 50 ohm coax |

ground | | |

or o----| |----------------------------+

N.C. -------- shield





| RECOMMENDED FILTERS

|

| If you don't want to make your own filters, the following have good

| performance, are well-built and affordable:

|

| Model 400 BCB interference filter (3.5 MHz highpass)

|
http://www.iceradioproducts.com/filtersrf.html#bcb

|

| Model 420 HF lowpass filter (30 MHz lowpass)

| http://www.iceradioproducts.com/filtersrf.html#3

| (scroll down a bit to see the model 420)

|

| If you have a random-wire antenna, the following unit will provide

| impedance matching and lightning protection (connect antenna to 450-ohm

| terminal):

|

| Model 182A beverage matching unit

| http://www.iceradioproducts.com/reconly.html#Beverage Matching





FILTER PLANS



The original credit for the high-pass and low-pass filters goes to Paul

Blumstein and John Shalamskas, respectively. Edited versions of their

articles are included he





Date: 09 Jan 91 00:54:08 GMT

From: (Paul Blumstein)

Subject: BC Band Hi-Pass Filter



The following ascii-schematic diagram is a high pass filter that will

filter out Broadcast Band (MW) stations. I found it a great boon to my

shortwave listening since local MW stations overload my ATS-803A front

end & appear in SW, especially with a long antenna.



If you remember my antenna saga, I went from 50 feet to 150 feet & had

overload problems causing me to cut back to 50 feet. (Even at 50 feet,

I still have some MW interference). I took the advice of Gary Coffman

and looked up filters in the ARRL Handbook. With the filter in place, I

intend to try to increase my antenna length again.



Anywho, here is the filter, for interested parties.





--------||---+----||-----+----||-----------

} }

{ {

} }

-------------+-----------+-----------------



The outer capacitors are 1500 pf ceramic disks.

The inner capacitor is 820 pf ceramic disk.

The squiggly things are coils (two total). Each one is 2.7 uh.

(a close value will do).





Date: 12 Jan 91 00:44:25 GMT

From:
(William K. McFadden)

Subject: BC Band Hi-Pass Filter



I built the filter that Paul Blumstein posted recently and measured it

on a gain-phase analyzer. Here are its characteristics:



100 kHz -120dB

500 kHz -68dB

1000 kHz -38dB

1600 kHz -15dB

2100 kHz -3dB



The source and load impedances were 50 ohms. Because the filter has

five elements, the attenuation is 30dB per octave. The measurements

confirmed this.



This filter seems to be a good compromise between interference

attenuation and passband response. There is very little attenuation in

the 120m band and above. It could use a little more attenuation at the

upper end of MW, which could be done with more stages or a higher cutoff

frequency. Alternatively, you could build two of these filters and put

them in series. (Since two 1500pF capacitors in series are really

750pF, you could eliminate one cap.)



Just for fun, I put 470 ohms in series with the input to see how the

filter performed with an antenna mismatch. The response was:



100 kHz -105dB

500 kHz -60dB

1000 kHz -35dB

1600 kHz -15dB

2300 kHz -3dB



These figures are normalized to the passband response of -15dB, which is

due to the impedance mismatch between the source and load and would have

been there without the filter. Hence, the filter works almost as well

in spite of the mismatch, which is good news to those who use long-wire

antennas.





Date: 22 Apr 92 08:59:33 GMT

From:
(John Shalamskas)

Subject: Construction of filters for SW reception



Several people have asked for construction details of the filters I

built for my DX-440.



The high-pass filter helped some, but in my location the VHF/UHF

broadcasters are also causing problems. So, I dug out the ARRL handbook

and chose a 7-element Chebyshev low-pass design that is -3 dB at 35 MHz,

-20 dB at 43 MHz, and -50 dB at 64 MHz (all calculated; it works well in

practice!)





LOW-PASS FILTER (Rejects FM, TV, etc.)



0.36 uH 0.42 uH 0.36 uH

signal -------+--UUU--+--UUUUU--+--UUU--+------- signal

| | | |

82 ___ 180___ 180___ ___ 82

pF --- pF--- pF--- --- pF

shield | | | | shield

braid -------+-------+----+----+-------+------- braid

|

chassis ground





I had to do a little more improvising at this point. I used .33 uH

instead of .36, and .66 uH instead of .42, but it works fine.



The 5-lug terminal strips were perfect for these circuits, since there

are 4 lugs plus a grounded lug. All "ground" connections go to the lug

that is mounted to the chassis, and the other 4 lugs are used for each

of the connections on the signal line. One terminal strip is used per

filter. Since both filters were necessary to clean up the hash, I am

going to put them both into one box when I get the time.



The proper way to connect them is in series, i.e.



signal in ------- filter 1 -------- filter 2 -------- signal out



There is no difference between ends. They are "bilateral" which means

you can't possibly hook them up backwards. (In the above schematics,

left and right ends are interchangeable.)





COIL WINDING



You can make the coils yourself using this formula:



L = 0.2 * B^2 * N^2 / (3B + 9A + 10C)



L is the inductance, in uH

A is the length of the coil, in inches

B is the mean diameter of the coil, in inches

C is the diameter of the wire, in inches

N is the number of turns



For small wire, you can assume C = 0.





PARTS SOURCE



Parts for the filters can be obtained from the following source:

http://www.digi-key.com/



--- end ---



--

Bill McFadden http://www.rdrop.com/users/billmc

CAUTION: Don't look into laser beam with remaining eye.


What about phone line voltage in case the cap opens up? No risks there, William?


  #6   Report Post  
Old September 1st 14, 10:01 PM posted to rec.radio.shortwave
external usenet poster
 
First recorded activity by RadioBanter: May 2012
Posts: 341
Default Phone line as SW antenna [12-Jul-06]

On Monday, September 1, 2014 2:46:29 PM UTC-4, wrote:
On Monday, September 1, 2014 10:00:05 AM UTC+3, William Mcfadden wrote:

[Last modified 12-Jul-06]








The latest version of this file can be accessed via my web page at:




http://www.rdrop.com/users/billmc








Phone line as SW antenna




Bill McFadden












Changes preceded by "|".








WARNINGS AND DISCLAIMERS








Connecting unapproved devices to phone lines may be illegal in your area.




Telephone lines present a potential shock hazard. Do not use this antenna




for transmitting. Use at your own risk.












INTRODUCTION








This article describes how to use a phone line as a shortwave receiving




antenna. Performance will vary depending on the kind of phone line you




have. Overhead lines usually make okay antennas, while underground lines




| usually don't. Phone lines carrying DSL service may be unsuitable because




| DSL operates over a wide spectrum. A phone line antenna will generally




pick up more power line noise than a dedicated antenna, so don't expect to




| use it for DX work. Nevertheless, I found that it outperformed the




| telescopic whip antennas built into many portables.








A reader sent in this suggestion: If you're concerned about connecting




the phone line directly to the receiver, try wrapping the phone cord




several times around the receiver's telescopic whip antenna instead.




Performance may not be as good as a direct connection, but it will




probably be better than the whip antenna by itself.








Someone else wrote asking about lightning protection. I haven't thought




much about it because thunderstorms are rare in my area. Most phone lines




have lightning arrestors on them where they enter the house, but the




lightning arrestors may pass enough energy during a lightning strike




damage a receiver. My suggestion is to disconnect the antenna when not in




use if you experience frequent thunderstorms.












HOW TO DO IT








The simplest connection is a single capacitor between the phone line and




receiver. The capacitor eliminates all phone line voltages, including




| ringing, so that they will not harm the receiver. The capacitor should




| be rated 250 volts or higher.












Phone line RF connector




red .01 uF center cond. / \




or o--------||------------------------------|-o | To receiver




green \ /




50 ohm coax |




ground |




or o------------------------------------------+




N.C. shield












N.C. = no connect. I originally connected the phone line ground (yellow




wire) to this terminal, but reception was better without it (if you do




this, play it safe and put a .01 uF capacitor in series). If another




ground is available, you can connect it to this terminal.








If you are picking up local AM or FM radio stations on the shortwave




bands, it is likely that your receiver is overloaded. Inexpensive and




portable receivers usually lack the filtering needed to eliminate this




interference, but you can make your own filters. Filters can also be




| purchased from shortwave dealers (see below for recommendations).








A high-pass filter can be used to remove signals below the shortwave




bands. It rejects interference from local AM stations and presents a high




impedance to the phone line at audio frequencies so that the phone line




remains balanced.








A low-pass filter can be used to remove signals above the shortwave bands.




It rejects interference from FM and TV stations, as well as VHF 2-way




radio transmitters. If you use both filters, connect the output of the




first filter to the input of the second (don't forget to connect their




ground terminals together). It doesn't matter which filter is connected




first.








These filters also work well with random wire antennas. Just connect the




antenna in place of the phone line.








The filter(s) should be connected to the phone line in this manner:












Phone line RF connector




red -------- center cond. / \




or o----| |--------------------------|-o | To receiver




green | | \ /




| FILTER | 50 ohm coax |




ground | | |




or o----| |----------------------------+




N.C. -------- shield












| RECOMMENDED FILTERS




|




| If you don't want to make your own filters, the following have good




| performance, are well-built and affordable:




|




| Model 400 BCB interference filter (3.5 MHz highpass)




|
http://www.iceradioproducts.com/filtersrf.html#bcb



|




| Model 420 HF lowpass filter (30 MHz lowpass)




| http://www.iceradioproducts.com/filtersrf.html#3




| (scroll down a bit to see the model 420)




|




| If you have a random-wire antenna, the following unit will provide




| impedance matching and lightning protection (connect antenna to 450-ohm




| terminal):




|




| Model 182A beverage matching unit




| http://www.iceradioproducts.com/reconly.html#Beverage Matching












FILTER PLANS








The original credit for the high-pass and low-pass filters goes to Paul




Blumstein and John Shalamskas, respectively. Edited versions of their




articles are included he












Date: 09 Jan 91 00:54:08 GMT




From: (Paul Blumstein)




Subject: BC Band Hi-Pass Filter








The following ascii-schematic diagram is a high pass filter that will




filter out Broadcast Band (MW) stations. I found it a great boon to my




shortwave listening since local MW stations overload my ATS-803A front




end & appear in SW, especially with a long antenna.








If you remember my antenna saga, I went from 50 feet to 150 feet & had




overload problems causing me to cut back to 50 feet. (Even at 50 feet,




I still have some MW interference). I took the advice of Gary Coffman




and looked up filters in the ARRL Handbook. With the filter in place, I




intend to try to increase my antenna length again.








Anywho, here is the filter, for interested parties.












--------||---+----||-----+----||-----------




} }




{ {




} }




-------------+-----------+-----------------








The outer capacitors are 1500 pf ceramic disks.




The inner capacitor is 820 pf ceramic disk.




The squiggly things are coils (two total). Each one is 2.7 uh.




(a close value will do).












Date: 12 Jan 91 00:44:25 GMT




From:
(William K. McFadden)



Subject: BC Band Hi-Pass Filter








I built the filter that Paul Blumstein posted recently and measured it




on a gain-phase analyzer. Here are its characteristics:








100 kHz -120dB




500 kHz -68dB




1000 kHz -38dB




1600 kHz -15dB




2100 kHz -3dB








The source and load impedances were 50 ohms. Because the filter has




five elements, the attenuation is 30dB per octave. The measurements




confirmed this.








This filter seems to be a good compromise between interference




attenuation and passband response. There is very little attenuation in




the 120m band and above. It could use a little more attenuation at the




upper end of MW, which could be done with more stages or a higher cutoff




frequency. Alternatively, you could build two of these filters and put




them in series. (Since two 1500pF capacitors in series are really




750pF, you could eliminate one cap.)








Just for fun, I put 470 ohms in series with the input to see how the




filter performed with an antenna mismatch. The response was:








100 kHz -105dB




500 kHz -60dB




1000 kHz -35dB




1600 kHz -15dB




2300 kHz -3dB








These figures are normalized to the passband response of -15dB, which is




due to the impedance mismatch between the source and load and would have




been there without the filter. Hence, the filter works almost as well




in spite of the mismatch, which is good news to those who use long-wire




antennas.












Date: 22 Apr 92 08:59:33 GMT




From:
(John Shalamskas)



Subject: Construction of filters for SW reception








Several people have asked for construction details of the filters I




built for my DX-440.








The high-pass filter helped some, but in my location the VHF/UHF




broadcasters are also causing problems. So, I dug out the ARRL handbook




and chose a 7-element Chebyshev low-pass design that is -3 dB at 35 MHz,




-20 dB at 43 MHz, and -50 dB at 64 MHz (all calculated; it works well in




practice!)












LOW-PASS FILTER (Rejects FM, TV, etc.)








0.36 uH 0.42 uH 0.36 uH




signal -------+--UUU--+--UUUUU--+--UUU--+------- signal




| | | |




82 ___ 180___ 180___ ___ 82




pF --- pF--- pF--- --- pF




shield | | | | shield




braid -------+-------+----+----+-------+------- braid




|




chassis ground












I had to do a little more improvising at this point. I used .33 uH




instead of .36, and .66 uH instead of .42, but it works fine.








The 5-lug terminal strips were perfect for these circuits, since there




are 4 lugs plus a grounded lug. All "ground" connections go to the lug




that is mounted to the chassis, and the other 4 lugs are used for each




of the connections on the signal line. One terminal strip is used per




filter. Since both filters were necessary to clean up the hash, I am




going to put them both into one box when I get the time.








The proper way to connect them is in series, i.e.








signal in ------- filter 1 -------- filter 2 -------- signal out








There is no difference between ends. They are "bilateral" which means




you can't possibly hook them up backwards. (In the above schematics,




left and right ends are interchangeable.)












COIL WINDING








You can make the coils yourself using this formula:








L = 0.2 * B^2 * N^2 / (3B + 9A + 10C)








L is the inductance, in uH




A is the length of the coil, in inches




B is the mean diameter of the coil, in inches




C is the diameter of the wire, in inches




N is the number of turns








For small wire, you can assume C = 0.












PARTS SOURCE








Parts for the filters can be obtained from the following source:




http://www.digi-key.com/







--- end ---








--




Bill McFadden http://www.rdrop.com/users/billmc




CAUTION: Don't look into laser beam with remaining eye.




What about phone line voltage in case the cap opens up? No risks there, William?


Only when ringing-about 100VAC,very small current.
  #8   Report Post  
Old September 3rd 14, 07:30 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Jul 2014
Posts: 2
Default Phone line as SW antenna [12-Jul-06]

I lived in a very rural area. I successfully used the phone line for
transmitting and receiving back in 1953 when I was 12 years old. I had
it tuned up for 40 meters cw. I had a novice ticket. I made lots of
contacts and had a lot of fun. I was only running about 20 watts maximum.

I had to stop using it and put up an antenna that did not work as well
when the phone company seemed like they might not like it. One day I
looked out my bedroom window where I was operating and saw a phone
company truck. There were two guys there about a two blocks away with
very long bamboo poles with coils at the top. They were listening with
head phones. I stopped transmitting immediately. I got on my bicycle and
went over to them and asked them what they were doing. My worst fears
were confirmed. They were looking for someone injecting RF into the
phone line. I knew my father would whip me for doing this. He had no
idea that I was using the phone line for an antenna. I have never tried
this again.

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