PAR Electronics EF-SWL Antenna
 

On 7 abr, 14:24, "Geoffrey S. Mendelson"
wrote:
Wimpie wrote:
Universal Radio mentions USD 66.95 for the antenna. It is probably
worth the price, but it doesn't mean it is better then a home brew
construction or give better reception with respect to your current
setup.

As I said before, a friend of mine has their ham version, which is what I
base the following comment on. The quality of construction and materials
used is very high. It is not an antenna that your average guy is going to
duplicate for a lot less money.

Assuming I could figure out the wiring for the loading coil and the traps
(his has traps, I don't know if this one does), I could duplicate it,
but it would look like something someone with knowledge, but little skill
had built (becuase it would be built that way).

If I were in the US, I would buy one. Since ordering things like this is
difficult, and delivery services cost a small fortune (an order sent via
UPS or FEDEX would cost at least $50 and probably $20 in taxes), I would make
one an live with what I had. :-)

The transformer/common mode choke has same functionality as the PAR
antenna. In addition I can disable the 1:9 impedance transformer
(while the common mode filter remains). I use a narrow band tunable
preselector to avoid "noise" from intermodulation products.

Can you describe it better? a 1:9 balun as it were is easy to make, and 1:4
VHF TV/FM radio ones are getting harder to find, but are still out there.

Thanks, and 73,

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel *N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.

PAR Electronics EF-SWL Antenna
 

Wimpie wrote:


As far as I know the proposed antenna is a single wire (without traps)
in combination with a 1:9 impedance transformer. www.parelectronics.com/swl-end.php
shows some details. It uses a two-hole ferrite core and is for receive
only. You can disconnect the antenna side ground from the 50/75 Ohms
cable braid to optimize for minimum noise.

The one I made myself is an autotransformer with a separate common
mode choke. The autotransformer enables me to extend the useful
bandwidth downward without getting too much leakage inductance.

As my transformer has no galvanic isolation, I needed a separate
common mode choke. The common mode choke is a series circuit of 2
wound ferrite cores. The first core with RG174 has best performance at
the middle and upper part of HF. The second core with RG174 coaxial
cable has its highest common mode impedance around 3 MHz.

If you need further clarification, don't hesitate to contact me.

Best regards,

Wim
PA3DJS
www.tetech.nl
remove abc first before hitting the send button.

http://www.bobsamerica.com/9-1balun.html

PAR Electronics EF-SWL Antenna
 

On Apr 7, 5:24*am, "Geoffrey S. Mendelson"
wrote:
Wimpie wrote:
Universal Radio mentions USD 66.95 for the antenna. It is probably
worth the price, but it doesn't mean it is better then a home brew
construction or give better reception with respect to your current
setup.

As I said before, a friend of mine has their ham version, which is what I
base the following comment on. The quality of construction and materials
used is very high. It is not an antenna that your average guy is going to
duplicate for a lot less money.

Assuming I could figure out the wiring for the loading coil and the traps
(his has traps, I don't know if this one does), I could duplicate it,
but it would look like something someone with knowledge, but little skill
had built (becuase it would be built that way).

If I were in the US, I would buy one. Since ordering things like this is
difficult, and delivery services cost a small fortune (an order sent via
UPS or FEDEX would cost at least $50 and probably $20 in taxes), I would make
one an live with what I had. :-)

The transformer/common mode choke has same functionality as the PAR
antenna. In addition I can disable the 1:9 impedance transformer
(while the common mode filter remains). I use a narrow band tunable
preselector to avoid "noise" from intermodulation products.

Can you describe it better? a 1:9 balun as it were is easy to make, and 1:4
VHF TV/FM radio ones are getting harder to find, but are still out there.

Thanks, and 73,

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel *N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.

PAR Electronics EF-SWL Antenna
 

On Apr 7, 7:45*am, dave wrote:
Wimpie wrote:

As far as I know the proposed antenna is a single wire (without traps)
in combination with a 1:9 impedance transformer. *www.parelectronics.com/swl-end.php
shows some details. It uses a two-hole ferrite core and is for receive
only. You can disconnect the antenna side ground from the 50/75 Ohms
cable braid to optimize for minimum noise.

The one I made myself is an autotransformer with a separate common
mode choke. * The autotransformer enables me to extend the useful
bandwidth downward without getting too much leakage inductance.

As my transformer has no galvanic isolation, I needed a separate
common mode choke. The common mode choke is a series circuit of 2
wound ferrite cores. The first core with RG174 has best performance at
the middle and upper part of HF. The second core with RG174 coaxial
cable has its highest common mode impedance around 3 MHz.

If you need further clarification, don't hesitate to contact me.

Best regards,

Wim
PA3DJS
www.tetech.nl
remove abc first before hitting the send button.

http://www.bobsamerica.com/9-1balun.html- Hide quoted text -

- Show quoted text -

This looks like a basic good design, but it is different from PAR's.

Bruce

PAR Electronics EF-SWL Antenna
 

dave wrote:


http://www.bobsamerica.com/9-1balun.html

Interesting - Bob is a local friend - didn't realize he had that up on
his website.

He's got a wealth of information on his web site for people who enjoy
building accessories.

PAR Electronics EF-SWL Antenna
 

On Apr 7, 2:44*pm, wrote:
On Wed, 7 Apr 2010 14:19:12 -0700 (PDT), bpnjensen





wrote:
On Apr 7, 2:16*pm, wrote:
On Wed, 7 Apr 2010 13:28:18 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 1:20*pm, dave wrote:
bpnjensen wrote:

Dale at PAR advertises that his matching transformer is wound on a
binocular core...but he does not go into precise detail. You'd have to
buy one and disassemble the unit casing to find out.

Bruce

Maybe we shouldn't have chased him away...

We've lost more smart people that way...

I think it was the part about buying one and disassembling it. Could
be using one of these. Probably type 43.http://www.surplussales.com/Inductor...FerMisc-5.html

Jim

Indeed! *I bet I know which one Dale uses ;-)

Maybe even cheaper with instructions and diagram:http://www.aytechnologies.com/TechData/9-to-1_XFMR.htm

Jim

Thanks Jim - I have two compound questions about this diagram that he
does not answer in the FAQ:

1 - In this wrapping technique, does the 50 ohm node at upper left
lead electrically to the 450 ohm node at upper right, or the feedline
ground? I assume the latter, but...this technically creates a half-
wrap somewhere, which would give either 2.5 or 3.5 turns. Same for
the 450 ohm node. It is not obvious from the diagram or the text.

2 - Is it automatically assumed that the feedline ground also goes to
a ground rod (somewhere?), or just the coax outer conductor? What
happens if there is no radio ground, just one at the antenna ground,
or vice-versa? What if both grounds are at the same rod?

Just wonderin'... :-)

Bruce

PAR Electronics EF-SWL Antenna
 

On Wed, 7 Apr 2010 21:42:14 -0700 (PDT), bpnjensen
wrote:

On Apr 7, 2:44*pm, wrote:
On Wed, 7 Apr 2010 14:19:12 -0700 (PDT), bpnjensen





wrote:
On Apr 7, 2:16*pm, wrote:
On Wed, 7 Apr 2010 13:28:18 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 1:20*pm, dave wrote:
bpnjensen wrote:

Dale at PAR advertises that his matching transformer is wound on a
binocular core...but he does not go into precise detail. You'd have to
buy one and disassemble the unit casing to find out.

Bruce

Maybe we shouldn't have chased him away...

We've lost more smart people that way...

I think it was the part about buying one and disassembling it. Could
be using one of these. Probably type 43.http://www.surplussales.com/Inductor...FerMisc-5.html

Jim

Indeed! *I bet I know which one Dale uses ;-)

Maybe even cheaper with instructions and diagram:http://www.aytechnologies.com/TechData/9-to-1_XFMR.htm

Jim

Thanks Jim - I have two compound questions about this diagram that he
does not answer in the FAQ:

1 - In this wrapping technique, does the 50 ohm node at upper left
lead electrically to the 450 ohm node at upper right, or the feedline
ground? I assume the latter, but...this technically creates a half-
wrap somewhere, which would give either 2.5 or 3.5 turns. Same for
the 450 ohm node. It is not obvious from the diagram or the text.

You would have 3 turns on one side and technically 2.5 turns on the
feed side but this would be completed in the connection to the radio.
Same for the other connection to the antenna. 9 turns on the opposite
side and 8.5 turns to antenna. This is how I see it.

2 - Is it automatically assumed that the feedline ground also goes to
a ground rod (somewhere?), or just the coax outer conductor? What
happens if there is no radio ground, just one at the antenna ground,
or vice-versa? What if both grounds are at the same rod?

Since there is no ground available the feedline ground just goes to
the coax outer conductor. Connnect the antenna and feedline grounds
together at the balun. Also, try them disconnected. Whatever gives the
least noise, best signal.

If something close to ground like a window frame or metal railing is
avaliable connect that to either or both ground connections. It
depends on where the noise is coming from which will work best.

Whatever you do, always disconnect the antenna if there is lightning
in the area.

Just wonderin'... :-)

Bruce

PAR Electronics EF-SWL Antenna
 

On Apr 8, 6:40*am, wrote:
On Wed, 7 Apr 2010 21:42:14 -0700 (PDT), bpnjensen

snips

Thanks Jim - I have two compound questions about this diagram that he
does not answer in the FAQ:

1 - In this wrapping technique, does the 50 ohm node at upper left
lead electrically to the 450 ohm node at upper right, or the feedline
ground? *I assume the latter, but...this technically creates a half-
wrap somewhere, which would give either 2.5 or 3.5 turns. *Same for
the 450 ohm node. *It is not obvious from the diagram or the text.

You would have 3 turns on one side and technically 2.5 turns on the
feed side but this would be completed in the connection to the radio.
Same for the other connection to the antenna. 9 turns on the opposite
side and 8.5 turns to antenna. This is how I see it.

2 - Is it automatically assumed that the feedline ground also goes to
a ground rod (somewhere?), or just the coax outer conductor? *What
happens if there is no radio ground, just one at the antenna ground,
or vice-versa? *What if both grounds are at the same rod?

Since there is no ground available the feedline ground just goes to
the coax outer conductor. Connnect the antenna and feedline grounds
together at the balun. Also, try them disconnected. Whatever gives the
least noise, best signal.

If something close to ground like a window frame or metal railing is
avaliable connect that to either or both ground connections. It
depends on where the noise is coming from which will work best.

Whatever you do, always disconnect the antenna if there is lightning
in the area.

Thank you Jim - this clears up quite a few questions I have had for a
long time :-)

Bruce

PAR Electronics EF-SWL Antenna
 

On 8 abr, 06:42, bpnjensen wrote:
On Apr 7, 2:44*pm, wrote:



On Wed, 7 Apr 2010 14:19:12 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 2:16*pm, wrote:
On Wed, 7 Apr 2010 13:28:18 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 1:20*pm, dave wrote:
bpnjensen wrote:

Dale at PAR advertises that his matching transformer is wound on a
binocular core...but he does not go into precise detail. You'd have to
buy one and disassemble the unit casing to find out.

Bruce

Maybe we shouldn't have chased him away...

We've lost more smart people that way...

I think it was the part about buying one and disassembling it. Could
be using one of these. Probably type 43.http://www.surplussales.com/Inductor...FerMisc-5.html

Jim

Indeed! *I bet I know which one Dale uses ;-)

Maybe even cheaper with instructions and diagram:http://www.aytechnologies.com/TechData/9-to-1_XFMR.htm

Jim

Thanks Jim - I have two compound questions about this diagram that he
does not answer in the FAQ:

1 - In this wrapping technique, does the 50 ohm node at upper left
lead electrically to the 450 ohm node at upper right, or the feedline
ground? *I assume the latter, but...this technically creates a half-
wrap somewhere, which would give either 2.5 or 3.5 turns. *Same for
the 450 ohm node. *It is not obvious from the diagram or the text.

2 - Is it automatically assumed that the feedline ground also goes to
a ground rod (somewhere?), or just the coax outer conductor? *What
happens if there is no radio ground, just one at the antenna ground,
or vice-versa? *What if both grounds are at the same rod?

Just wonderin'... :-)

Bruce

Hello Bruce and others,
[large text]

You make one complete turn when you pass both ferrites.

When you start from the left side (that is the 50 Ohms side), you end
at the left side also. So when you use green wire for the left side,
you have two green wire ends at the left side. For the secondary
side, you start from right en ends at the right side.

One full turn is like putting a hairpin through the cores (as
mentioned in the article).

The purpose of this type of transformer is:

#1. To get more output from a wire (and also more interference that
comes from outside). Mostly (in the receiving case), {wire length}
0.25 lambda. Therefore the wire has relative high impedance ( 50
Ohms). The transformer reduces the mismatch. Where the wire length is
about 0.25 lambda + n*0.5 lambda, your wire has relative low
impedance. In that case the transformer increases mismatch and this
will result in less output. This is mostly not a problem as
interference/noise coming from the antenna receiver's noise level.

#2. To separate the antenna circuit from the common mode coaxial
circuit to reduce indoor interference from domestic equipment.

When you connect both grounds together and have a high impedance
ground, the coaxial common mode circuit partly shares the antenna
circuit (they have the ground impedance in common). When indoor
interference couples to your coaxial cable, this interference is
coupled to your antenna via the common ground impedance. By
connecting "coaxial ground" only to the coaxial braid (and not to the
ground provision outside), there is no common ground anymore. This
reduces the coupling between common mode indoor interference on your
cable and the antenna.

The challenge with unbalanced antennas is to find a (floating) ground
that is relatively clean. Large metal surfaces can act as ground, even
when there is no physical connection to mother earth. In my experiment
I used a large metal window frame. I will try to connect this to the
window frame on the lower floor.

What if you have no large metal surface at hand? You can create one
artificially with wire (wires in star connection). You can omit the
ground and connect both grounds of the transformer together (so you
get an autotransformer). In that case, the cable that runs from the
transformer to your receiver functions as ground provision. If this
cable is several meters long, this will result in reasonable receive
signal strength. But there is a big however.

You decided to use an outdoor antenna (maybe) to reduce noise/
interference level. By using the cable braid as ground, your antenna
is partly inside your house again, as the cable is now part of your
antenna. When you like, you can use this transformer with a dipole
also. For the case that {dipole size} 0.5 lambda, you get more
signal and noise output.

The problem with the design of these transformers is the trade-off
between low frequency response, capacitance between sec. and prim.
and high frequency response. When you use a ferrite toroid and keep
sec. and prim. apart (no overlap), you create lowest coupling
capacitance, but worst high frequency performance because of leakage
inductance. When you want good low frequency performance (for
example down to long wave), you need sufficient turns to get
sufficient inductance, however this comes with increased coupling
capacitance, hence reducing the transformer's ability to separate the
common mode cable circuit from the antenna circuit (at higher
frequencies).

There are several reviews about this type of transformers that they
reduce interference significantly. If it does, it is mostly not
because of the transformer ratio, but because of the isolation between
primary and secondary (when you don’t connect the grounds together).

When the interference that reaches your antenna comes from outside,
the transformer increases signal as well as noise, and you will only
gain S/N ratio when in the old situation the receiver's noise was
dominant.

Best regards,


Wim
PA3DJS
www.tetech.nl
in case of PM, please remove abc first.

PAR Electronics EF-SWL Antenna
 

On Thu, 8 Apr 2010 10:40:56 -0700 (PDT), Wimpie
wrote:

On 8 abr, 06:42, bpnjensen wrote:
On Apr 7, 2:44*pm, wrote:



On Wed, 7 Apr 2010 14:19:12 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 2:16*pm, wrote:
On Wed, 7 Apr 2010 13:28:18 -0700 (PDT), bpnjensen

wrote:
On Apr 7, 1:20*pm, dave wrote:
bpnjensen wrote:

Dale at PAR advertises that his matching transformer is wound on a
binocular core...but he does not go into precise detail. You'd have to
buy one and disassemble the unit casing to find out.

Bruce

Maybe we shouldn't have chased him away...

We've lost more smart people that way...

I think it was the part about buying one and disassembling it. Could
be using one of these. Probably type 43.http://www.surplussales.com/Inductor...FerMisc-5.html

Jim

Indeed! *I bet I know which one Dale uses ;-)

Maybe even cheaper with instructions and diagram:http://www.aytechnologies.com/TechData/9-to-1_XFMR.htm

Jim

Thanks Jim - I have two compound questions about this diagram that he
does not answer in the FAQ:

1 - In this wrapping technique, does the 50 ohm node at upper left
lead electrically to the 450 ohm node at upper right, or the feedline
ground? *I assume the latter, but...this technically creates a half-
wrap somewhere, which would give either 2.5 or 3.5 turns. *Same for
the 450 ohm node. *It is not obvious from the diagram or the text.

2 - Is it automatically assumed that the feedline ground also goes to
a ground rod (somewhere?), or just the coax outer conductor? *What
happens if there is no radio ground, just one at the antenna ground,
or vice-versa? *What if both grounds are at the same rod?

Just wonderin'... :-)

Bruce

Hello Bruce and others,
[large text]

You make one complete turn when you pass both ferrites.

When you start from the left side (that is the 50 Ohms side), you end
at the left side also. So when you use green wire for the left side,
you have two green wire ends at the left side. For the secondary
side, you start from right en ends at the right side.

One full turn is like putting a hairpin through the cores (as
mentioned in the article).

The purpose of this type of transformer is:

#1. To get more output from a wire (and also more interference that
comes from outside). Mostly (in the receiving case), {wire length}
0.25 lambda. Therefore the wire has relative high impedance ( 50
Ohms). The transformer reduces the mismatch. Where the wire length is
about 0.25 lambda + n*0.5 lambda, your wire has relative low
impedance. In that case the transformer increases mismatch and this
will result in less output. This is mostly not a problem as
interference/noise coming from the antenna receiver's noise level.

#2. To separate the antenna circuit from the common mode coaxial
circuit to reduce indoor interference from domestic equipment.

When you connect both grounds together and have a high impedance
ground, the coaxial common mode circuit partly shares the antenna
circuit (they have the ground impedance in common). When indoor
interference couples to your coaxial cable, this interference is
coupled to your antenna via the common ground impedance. By
connecting "coaxial ground" only to the coaxial braid (and not to the
ground provision outside), there is no common ground anymore. This
reduces the coupling between common mode indoor interference on your
cable and the antenna.

The challenge with unbalanced antennas is to find a (floating) ground
that is relatively clean. Large metal surfaces can act as ground, even
when there is no physical connection to mother earth. In my experiment
I used a large metal window frame. I will try to connect this to the
window frame on the lower floor.

What if you have no large metal surface at hand? You can create one
artificially with wire (wires in star connection). You can omit the
ground and connect both grounds of the transformer together (so you
get an autotransformer). In that case, the cable that runs from the
transformer to your receiver functions as ground provision. If this
cable is several meters long, this will result in reasonable receive
signal strength. But there is a big however.

You decided to use an outdoor antenna (maybe) to reduce noise/
interference level. By using the cable braid as ground, your antenna
is partly inside your house again, as the cable is now part of your
antenna. When you like, you can use this transformer with a dipole
also. For the case that {dipole size} 0.5 lambda, you get more
signal and noise output.

The problem with the design of these transformers is the trade-off
between low frequency response, capacitance between sec. and prim.
and high frequency response. When you use a ferrite toroid and keep
sec. and prim. apart (no overlap), you create lowest coupling
capacitance, but worst high frequency performance because of leakage
inductance. When you want good low frequency performance (for
example down to long wave), you need sufficient turns to get
sufficient inductance, however this comes with increased coupling
capacitance, hence reducing the transformer's ability to separate the
common mode cable circuit from the antenna circuit (at higher
frequencies).

There are several reviews about this type of transformers that they
reduce interference significantly. If it does, it is mostly not
because of the transformer ratio, but because of the isolation between
primary and secondary (when you don’t connect the grounds together).

When the interference that reaches your antenna comes from outside,
the transformer increases signal as well as noise, and you will only
gain S/N ratio when in the old situation the receiver's noise was
dominant.

Best regards,


Wim
PA3DJS
www.tetech.nl
in case of PM, please remove abc first.

Wim,

In a few paragraphs you have covered so much. Excellent information
about grounding and excellent points about ferrites and coupling at
different frequencies.

If we had a few more people like you Wim, we would have a lot more
people in this newsgroup. Hope you stay around. Thanks.

Jim