On Tue, 29 Jun 2004 15:34:42 -0600, John Doty
wrote:

You are making the assumption that that the antenna only picks
up radiated modes.

I am making no such assumption and all following commentary does
absolutely nothing to separate the concerns of SWLers from Ham
activity.

Non-radiated electromagnetic modes are also
troublesome, particularly common mode on the transmission line. This
tends to be the way that locally generated noise from household gadgets
gets into an antenna system.

Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.

Let's work with exactly that scenario you offered.

S6 (Calibrated) on my Drake TR-7 is -88dBm - so close to your 10µV to
be indistinguishable. My TS-430 varies from -80dBm to -73dBm. There
is no calibrated S-Meter for my DX-440, but for a $200 SW set, its
sensitivity is -90dBm for a full scale meter indication (about 7dB
range from top to bottom).

All very well and good. Now if we regard this speculation of 10mW (it
is, after all, the epitome of a wild ass guess, isn't it?); then,
let's reverse engineer that 10nW product from 6kHz buckets over the
range of 30MHz to find 50µW which is 23dB below the original power
presumably suppressed 60dB. Well, I have either pencil-whipped you,
or you me, or each other - the numbers don't add up. Hardly matters
given the original specification had no basis in fact.

However, if I return to the original "problem" of noise derived from
household sources; then that is also something I have closely
measured.

Across time, frequency, antennas, and known noise sources I have found
it as low as S1 for my longwire (an antenna supposedly unused by Hams)
to as high as S7 (for that same longwire). My loops, dipoles and
verticals hardly fell outside of this range to present any gilt-edge
design.

With every circuit in the house broken (operating battery power in the
dark), average noise level was either S2 for a vertical, or S1 to S3
for a loop (rather upsetting the voodoo of loops being quiet and
verticals being noisy). When I returned power to the house by stages,
I insured every opportunity of injecting noise by setting dimmers to
their worst position (about 50%). In the low bands, I suffered as
much as S8 noise levels with an average of S5 when the house was full
lit (also including fluorescents) and all noise sources adding to the
cacophony of reception. This was for a loop antenna.

On the other hand, if your transmitter puts out 1 kW, 60 dB of loss
means it only delivers 1 mW of RF to the dimmer, an amount unlikely to
interfere with its operation. Reciprocity does not mean *consequences*
are symmetrical.

This effect of reciprocity has been reported so frequently in this
group so as to negate your premise. We have many queries for how to
solve this problem.

To this point, you have not offered any particularly receive dominated
issue that is not already a heavily trafficked topic with transmission
antennas.

A deep, steerable null can be extremely useful for reception, but its
not generally useful for transmission.

This really goes off the deep edge. Barring loss introduced for the
sake of jimmying the logic, transmitters AND receivers enjoy the GAIN
derived from the introduction of a null not otherwise part of the
characteristic. This is a commonplace of theory and practice. Where
ever you can design or contribute to a null; then this must of
necessity result in an increase in signal outside of its region.
These are all commonplace observations discussed here that are
observable for either Ham or SWL operations. There is NO differential
offered in these observations that separate SWL from Ham activities.

Such examples of small loops used for MF are proof positive how poor
an antenna can be, and the RF gain knob resurrecting its pitiful
efficiency.

But for MWDX reception, efficiency simply isn't an important virtue.

I believe I have said that at least 3 to 5 times already.

Gain is cheap. What matters is the steerable nulls. An efficient
*steerable* MW antenna is enormous and expensive.

Who needs an efficient MW antenna?

This does NOT demonstrate some illusion of superior
receive antenna design; rather it is more smoke and mirrors as an
argument. Inverting the argument, if you had a full sized antenna for
that band, you would only need a galena crystal and cat whisker to
power your hi-Z headset. For DX you would only need a $5 AF
amplifier. The smaller antenna clearly needs more dollars expended to
offset the debilities of the poorer efficiency.

Sensitivity is the cheapest, easiest virtue to put into a receiver.
Essentially all modern receivers have plenty. Indeed, the cheap ones
often overload when presented with an efficient antenna: you have to
spend the dollars to be able to handle the big signals!

All of $20 if you have any technical capacity. Otherwise push the
credit card across the display counter and spend as much as they can
sell you. This argument is like driving your car into the shop to get
the air changed in your tires every 100 miles.

Again, front end overload is a very common complaint offered here by
SWLers who are then advised in how to simply AND cheaply combat this
problem.

Speaking of strawmen, have you ever actually tried DXing with a crystal
radio?

Sure, what is so remarkable about that? Beyond this simple design,
ever hear of a super-Regen receiver? You don't need to spend half a
kilo-buck to get the same sensitivity and filtering is dirt cheap.
How about Q-multipliers? All such topics barely spread the wallet as
much as the illusion of more buttons make a better rig.

I love designing and building antennas: applied physics is fun. But it's
good engineering to go with the strengths of your technology. For my
inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of
effective bandwidth, something that is perhaps of little use to hams,
but is very useful to an SWL in conjunction with the frequency agility
of a modern receiver. 4 dB of efficiency loss is of negligible
consequence at HF and below if your receiver has a decent noise figure.

As I pointed out to Yahoo, if you choose to cripple yourself, then
slide on over to the shoulder and enjoy kicking up dust and rocks as
you travel down the road. a 4dB loss for an inverted L (hardly a SW
invention) is far too simple to remedy to make its suffering a boast
of martyrdom. It is a strange argument to offer that you can't afford
a $20 solution for your $500 set and $2 worth of wire.

I've never seen mention of this efficiency/bandwidth tradeoff in the ham
literature,

You haven't looked. Either contrived, wholly fictional, or accurately
represented, it is part of the stock in trade for selling antennas.
In this group, I would wager its discussion consumes more bandwidth
than bragging about how many QSL cards have been pasted to the wall.

but it's not hard to find in the professional literature.
For details of a specific calculation, see:

http://anarc.org/naswa/badx/antennas/SWL_longwire.html

-jpd

It would do you well to note that this "professional" whom you rely
upon, John Kraus, is one of the most notable Ham Radio Operators
frequently acknowledged and referred to here.

Do you or others have any actual differentiable discussion, or is this
simply an outlet for appoligia for why it isn't worth the strain to
lift a soldering iron when you can bench press a credit card?

73's
Richard Clark, KB7QHC

In article ,
(RHF) wrote:

RC (KB7QHC),

Spoken (written) like a True Amateur, and precicly why most SWLs
ignore what is written in reply to SWL 'type' Antennas questions
by HAMs.

Richard Clark is a goof that hangs out in rec.radio.amateur.antenna
which is a good reason to ignore him.

News group header sniped to RRS.

--
Telamon
Ventura, California

Richard Clark wrote:
On Tue, 29 Jun 2004 15:34:42 -0600, John Doty
wrote:


You are making the assumption that that the antenna only picks
up radiated modes.


I am making no such assumption and all following commentary does
absolutely nothing to separate the concerns of SWLers from Ham
activity.


Non-radiated electromagnetic modes are also
troublesome, particularly common mode on the transmission line. This
tends to be the way that locally generated noise from household gadgets
gets into an antenna system.

Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.


Let's work with exactly that scenario you offered.

S6 (Calibrated) on my Drake TR-7 is -88dBm - so close to your 10µV to
be indistinguishable. My TS-430 varies from -80dBm to -73dBm. There
is no calibrated S-Meter for my DX-440, but for a $200 SW set, its
sensitivity is -90dBm for a full scale meter indication (about 7dB
range from top to bottom).

All very well and good. Now if we regard this speculation of 10mW (it
is, after all, the epitome of a wild ass guess, isn't it?); then,
let's reverse engineer that 10nW product from 6kHz buckets over the
range of 30MHz to find 50µW which is 23dB below the original power
presumably suppressed 60dB. Well, I have either pencil-whipped you,
or you me, or each other - the numbers don't add up.

10 uV into 50 ohms is 2 pW, not 10 nW (E^2/R). 2 pW = -117 dBW = -87
dBm. Multiplying by 30000/6 = 5000 buckets makes 10 nW or -50 dBm.
Cancel the assumed 60 dB loss and I get +10 dBm, or 10 mW. The numbers
add up fine.


However, if I return to the original "problem" of noise derived from
household sources; then that is also something I have closely
measured.

Across time, frequency, antennas, and known noise sources I have found
it as low as S1 for my longwire (an antenna supposedly unused by Hams)
to as high as S7 (for that same longwire). My loops, dipoles and
verticals hardly fell outside of this range to present any gilt-edge
design.

Just because you couldn't doesn't mean others can't. Look at the rest of
the articles on the BADX site. Taking steps to minimize common mode
coupling has worked very well for me, and many people tell me it works
for them too.

You might also find the articles at http://www.qsl.net/wa1ion/
interesting, especially the one entitled "Another Look at Noise Reducing
Antennas". Mark's antenna designs are generally useless for
transmitting, but they make superb MWDX receiving antennas.


With every circuit in the house broken (operating battery power in the
dark), average noise level was either S2 for a vertical, or S1 to S3
for a loop (rather upsetting the voodoo of loops being quiet and
verticals being noisy). When I returned power to the house by stages,
I insured every opportunity of injecting noise by setting dimmers to
their worst position (about 50%). In the low bands, I suffered as
much as S8 noise levels with an average of S5 when the house was full
lit (also including fluorescents) and all noise sources adding to the
cacophony of reception. This was for a loop antenna.


On the other hand, if your transmitter puts out 1 kW, 60 dB of loss
means it only delivers 1 mW of RF to the dimmer, an amount unlikely to
interfere with its operation. Reciprocity does not mean *consequences*
are symmetrical.


This effect of reciprocity has been reported so frequently in this
group so as to negate your premise. We have many queries for how to
solve this problem.


To this point, you have not offered any particularly receive dominated
issue that is not already a heavily trafficked topic with transmission
antennas.

A deep, steerable null can be extremely useful for reception, but its
not generally useful for transmission.


This really goes off the deep edge. Barring loss introduced for the
sake of jimmying the logic, transmitters AND receivers enjoy the GAIN
derived from the introduction of a null not otherwise part of the
characteristic. This is a commonplace of theory and practice. Where
ever you can design or contribute to a null; then this must of
necessity result in an increase in signal outside of its region.
These are all commonplace observations discussed here that are
observable for either Ham or SWL operations. There is NO differential
offered in these observations that separate SWL from Ham activities.

Certainly there is. A narrow null takes little power from the pattern:
you get little gain by putting that in a broad lobe. For example, an
elementary dipole has, theoretically, infinitely deep nulls yet it only
has about 2 dBi gain. Now consider a phased array: small phasing errors
have little effect on the gain, but they can have a large effect on the
null depth.

When transmitting, you're generally interested in putting the power in
the right place, but when receiving you're often more interested in
avoiding picking up power from the wrong place. These considerations are
only weakly related.



Such examples of small loops used for MF are proof positive how poor
an antenna can be, and the RF gain knob resurrecting its pitiful
efficiency.

But for MWDX reception, efficiency simply isn't an important virtue.


I believe I have said that at least 3 to 5 times already.


Gain is cheap. What matters is the steerable nulls. An efficient
*steerable* MW antenna is enormous and expensive.


Who needs an efficient MW antenna?

People who transmit, of course!

Speaking of strawmen, have you ever actually tried DXing with a crystal
radio?


Sure, what is so remarkable about that? Beyond this simple design,
ever hear of a super-Regen receiver? You don't need to spend half a
kilo-buck to get the same sensitivity and filtering is dirt cheap.

Sure. Used them. Selectivity is *lousy*. For SW, I've gotten better
results with a plain regen. Still, my Drake R-8 is better for DX, my
Sony ICF-SW100 travels easy, and my Stromberg-Carlson 58-T sounds
wonderful, so I haven't played with a regen in quite a while.

How about Q-multipliers? All such topics barely spread the wallet as
much as the illusion of more buttons make a better rig.

I have a Heathkit Q-multiplier I built in 1965. It's pretty good at
nulling out unwanted carriers, but in peak mode the shape factor of a
single resonance is pretty poor. At the moment I don't have a working
receiver it's really suited to, but I have a Halli S-40 one of my
in-laws gave me, and one of these days I'll find the time to repair it
(it's in really poor shape). The S-40 could probably use a Q-multiplier
once I've got it in working order.



I love designing and building antennas: applied physics is fun. But it's
good engineering to go with the strengths of your technology. For my
inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of
effective bandwidth, something that is perhaps of little use to hams,
but is very useful to an SWL in conjunction with the frequency agility
of a modern receiver. 4 dB of efficiency loss is of negligible
consequence at HF and below if your receiver has a decent noise figure.


As I pointed out to Yahoo, if you choose to cripple yourself, then
slide on over to the shoulder and enjoy kicking up dust and rocks as
you travel down the road. a 4dB loss for an inverted L (hardly a SW
invention) is far too simple to remedy to make its suffering a boast
of martyrdom. It is a strange argument to offer that you can't afford
a $20 solution for your $500 set and $2 worth of wire.

How would you undo that 4 dB loss without loss of bandwidth? I'm hardly
boasting of martyrdom anyway: a broadband inverted L is a fine general
purpose receiving antenna.



I've never seen mention of this efficiency/bandwidth tradeoff in the ham
literature,


You haven't looked. Either contrived, wholly fictional, or accurately
represented, it is part of the stock in trade for selling antennas.
In this group, I would wager its discussion consumes more bandwidth
than bragging about how many QSL cards have been pasted to the wall.

Examples?

but it's not hard to find in the professional literature.
For details of a specific calculation, see:

http://anarc.org/naswa/badx/antennas/SWL_longwire.html

-jpd


It would do you well to note that this "professional" whom you rely
upon, John Kraus, is one of the most notable Ham Radio Operators
frequently acknowledged and referred to here.

He knew a great deal about the full range of antenna designs and
applications, not just ham radio. And he sure knew his physics.


Do you or others have any actual differentiable discussion, or is this
simply an outlet for appoligia for why it isn't worth the strain to
lift a soldering iron when you can bench press a credit card?

When a soldering iron is the best tool to get the job done, I lift a
soldering iron. The Stromberg-Carlson was a "bare chassis" restoration:
most of the resistors were 50% off value, the paper capacitors were
leaking, the electrolytics were dry, and one of the RF coils was open
(disassembling and reassembling the coil turret was a real pain). Still,
it was worth the work to get that wonderful sound.

The NASA certified techs I work with professionally tell me I'm pretty
good with a soldering iron, considering I'm a physicist. From them,
that's high praise :-)

-jpd

On Tue, 29 Jun 2004 22:41:44 -0600, John Doty
wrote:
Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.

10 uV into 50 ohms is 2 pW, not 10 nW (E^2/R). 2 pW = -117 dBW = -87
dBm. Multiplying by 30000/6 = 5000 buckets makes 10 nW or -50 dBm.
Cancel the assumed 60 dB loss and I get +10 dBm, or 10 mW. The numbers
add up fine.

As I said, one of the two of us was being pencil-whipped. This does
nothing to change the fact that the original term has no basis in
fact. It could as easily be laid to the effects of a nuclear EMP 2000
miles away. There will always be something to blame, and that is NOT
a solution nor is it differentiable between Ham and SWL antennas.

However, if I return to the original "problem" of noise derived from
household sources; then that is also something I have closely
measured.

Across time, frequency, antennas, and known noise sources I have found
it as low as S1 for my longwire (an antenna supposedly unused by Hams)
to as high as S7 (for that same longwire). My loops, dipoles and
verticals hardly fell outside of this range to present any gilt-edge
design.

Just because you couldn't doesn't mean others can't.

Can't WHAT? The numbers I offer are shown of direct experience
correlatable to real world conditions and conform to 3 Sigma of SWL
conditions. Being correlatable they were also resolved and reduced to
that same unpowered baseline without forcing me off the grid into
darkness. My station sits with a noise flicker based upon
atmospherics and radiation borne products, not the usual household
pollution that I both describe above and eliminated through techniques
described as commonplaces in this group.

There are no magic antennas and no magic rituals equal to these
commonplace practices that are offered here.

Look at the rest of
the articles on the BADX site. Taking steps to minimize common mode
coupling has worked very well for me, and many people tell me it works
for them too.

This material is NOT novel by any stretch of the imagination.
However, it is hardly fully encompassing and falls short of the entire
treatment. The notion that a spike in the ground solves common mode
reveals a very limited experience in the matter, and simply devolves
to the misty eyed sentimentality of "it works for me, so there is no
better way for you." Testimonial is a poor substitute for how and why
- especially when the suggested solution inevitably fails for someone.
The common response in that situation is to sneer them away as somehow
deserving their predicament - again, with no one knowing the basis of
the problem, they can hardly help but repeat the same nostrum now
shown to fail somewhere (an anathema in religion).

You might also find the articles at http://www.qsl.net/wa1ion/

These suggestions grow more bizarre by the posting where the
correspondent offers that SWLers ignore Amateur advice as poor quality
(a remark from a noted Yahoo), and then offer proof of their own
beguiling theories through quotes from - Amateur references.

interesting, especially the one entitled "Another Look at Noise Reducing
Antennas". Mark's antenna designs are generally useless for
transmitting, but they make superb MWDX receiving antennas.

I cannot see how injecting the notion of uselessness is a boon for an
argument upon a physicist who can understand the notion of symmetry or
what is called in this field of study, reciprocity. If it is useless
as a transmit antenna, is it useless as a receive antenna? Of course
not, as such the injection of this comment serves no purpose other
than rhetorical noise.

The problem with such a degraded S/N in the correspondence of ideas is
that the larger body of uninitiated SWLers come to the conclusion that
this "uselessness" is a positive boon to be sought in every antenna
design. Our eminent Yahoo wears this badge of anti-intellectualism as
a patronizing populist.

This discussion also reveals a poverty of alternative designs that
have equal or superior merits, even if devoid of transmitting
application. Those designs are widely discussed here and their merits
are weighed not in prejudicial terms but rather in technical
comparisons and their correlation to application. That is to say,
anyone can make an informed decision on the basis of these evaluations
offered here where we typical discard "testimonials" to the rubbish
heap.

A narrow null takes little power from the pattern:
you get little gain by putting that in a broad lobe. For example, an
elementary dipole has, theoretically, infinitely deep nulls yet it only
has about 2 dBi gain. Now consider a phased array: small phasing errors
have little effect on the gain, but they can have a large effect on the
null depth.

Again, this exposes a lack of experience in the matter. Those nulls
are balanced against the theoretical radiator called an isotropic
source. This is the i of the 2dBi (and in fact is actual;y higher
than that value).

Worse yet, this lack of experience further pollutes the uninitiated
SWLer's notion of this balance of ledger because no one on this earth
is ever going to experience that 2dB gain (nor the supposed sharp
nulls) - and simply due to earth being nearby (an irreconcilable fact
of life that extends out beyond 6 Sigma for the population of
listeners). A simple dipole one quarterwave above earth exhibits an
additional 3dB gain above and beyond your cited number. This goes to
show how your casually abandoned 4dB for an inverted L is so simply
recovered - through real comparisons rather than xeroxed theories.

The level of discussion is so unbalanced with myth, superstition and
hearsay that the casual SWLer seeking advice faces the problem of
sorting out the **** from the shinola. If I were to hike the dipole a
little more, it shows 8dB gain after allowing a real world loss of
1dB. To tell that same casual SWLer 4dB is no great loss gives a
spread of 10dB.

The consequence of this challenging this poor coverage of intellectual
offering is that the casual SWLer having the facts known, can in fact
choose to build a less optimal antenna, one that suits his real world
limitations, and enjoy a design that does not simply discard signal
with abandon. Alternatively, a simpler receiver can perform with an
excellent antenna as well as a box full of expensive knobs can with an
air cooled resistor.

When transmitting, you're generally interested in putting the power in
the right place, but when receiving you're often more interested in
avoiding picking up power from the wrong place. These considerations are
only weakly related.

This has been spoken too, the limitation is found in the signal and
noise being aligned along the same meridian. If there is any weak
relation it is found in the chance of distribution. The laws of
reciprocity are not violated by chance, and both Ham operator and
SWLer suffer the same odds. There is NOTHING separable here.

Who needs an efficient MW antenna?

People who transmit, of course!

And SWLers are not transmitting are they? Really, these specious
arguments do not advance any notion of this being separate issues.
There is nothing in the circularity of logic that demands poorer
transmit antenna designs are better receive antenna designs. Nearly
every beneficial description from your sources cited above lie outside
of the antenna and reside in the coupling or in the receiver. Such
commonplaces are not novel; they are not unique and special knowledge;
and they are certainly not universally applicable.

How would you undo that 4 dB loss without loss of bandwidth?

That has been responded to above. Loss of bandwidth is a chimera
suited for argument rather than operation. To say it is frequency
agile is the crowning claim for someone who is fain to turn a switch
and set a capacitor in 5 seconds. This isn't rocket surgery, children
learn such techniques within minutes of explanation and faithfully
demonstrate far less loss consistently for ever after.

Further, the usage of a tuner solves many other ills related to noise
and front end overload. The argument of the 9:1 transformer to ease
operation comes at the expense of simple cheap solutions - to no great
benefit, and further, to 4 dB additional loss as you describe. What
boon is to be found in that combination?

I find it laughable that one web site offered claims that a resonant
system is bad for your reception. What a crock! This has all the
logic of buying square wheels to increase your gas mileage.

I'm hardly
boasting of martyrdom anyway: a broadband inverted L is a fine general
purpose receiving antenna.

And what distinguishes it as a poor transmitting antenna? The
inclusion of the engineering decoration of the 9:1 transformer? This
logic is destroyed by a conventional tube transmitter (the original
application suited to this design).

Once again, every issue in relation to even this point is discussed as
a commonplace in this group with simple and cheap solutions that
perform without the concurrent 4dB loss. Such a cavalier attitude of
discarding signal is evidence of purchasing power, not technical
competence.

I've never seen mention of this efficiency/bandwidth tradeoff in the ham
literature,


You haven't looked. Either contrived, wholly fictional, or accurately
represented, it is part of the stock in trade for selling antennas.
In this group, I would wager its discussion consumes more bandwidth
than bragging about how many QSL cards have been pasted to the wall.

Examples?

As I offered, you need to look rather than claim. They are so common
that if they escape your attention, no work on my part is going to
satisfy you.

So, the question remains:
Do you or others have any actual differentiable discussion, or is this
simply an outlet for appoligia for why it isn't worth the strain to
lift a soldering iron when you can bench press a credit card?

73's
Richard Clark, KB7QHC

"Mark1" wrote in message
...
pse remove the nl newsgroup from this discussion.

Loop niet zo te zeuren Mark1, deze draad is gestart door een Nederlander
(Kees) en ge-crosspost naar twee engelse groepen. Dus dat deze heren hier
steeds weer terugkomen is gewoon deel van de originele discussie.

Meindert

Meindert Sprang bracht volgend idée uit :
"Mark1" wrote in message
...
pse remove the nl newsgroup from this discussion.

Loop niet zo te zeuren Mark1, deze draad is gestart door een Nederlander
(Kees) en ge-crosspost naar twee engelse groepen. Dus dat deze heren hier
steeds weer terugkomen is gewoon deel van de originele discussie.

Meindert

Wat een onzin Meindert, ik vraag gewoon of ze deze nieuwsgroep eruit
willen halen, het is en blijft een Nederlandse nieuwsgroep.

De 'draad' is gestart door Kees met reclame maken voor zijn website met
daarop zijn eigen gebouwde antenne, daar staat netjes bij dat hij wel
vragen wilt beantwoorden, nou prima maar dan wel op zijn e-mail adres
graag.

John Doty wrote:

Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.

What is the actual coupling process between common and differential mode
at the far (antenna) end of the coax?


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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RC,

The initial poster cross-posted the original Post to three NewsGroups.
1. rec.radio.shortwave
2. rec.radio.amateur.antenna
3. nl.radio.amateur

Then to just two:
1. rec.radio.shortwave
2. rec.radio.amateur.antenna

This reply is ONLY to: Rec.Radio.Shortwave {RRS}

I can see by your "WPE" Call-Sign that at one time you were a
SWL'er. But you have gone way beyond that now and are a Licensed
Amateur Radio Operator. I concede that you have far superior
technical expertise then myself in the area of antennas and more.

I simply remain a SWL'er

I will repeat part of my prior post:
"Spoken (written) like a True Amateur, and precisely why most SWLs
ignore what is written in reply to SWL 'type' Antennas questions
by HAMs."

As an Amateur 'you' talk down to me as a SWL and use your knowledge
and expertise to Attack and attempt to humble me as a SWL.

Everything that you have said may be true. But IMHO it is way
beyond what a SWL needs to know to simply build a SWL Antenna to
meet their listening needs with a 'portable' SW Radio or may be
a table top General Coverage Receiver. An Antenna that will fit
the 'limits' of their Available Space and other building and
property restrictions. A SWL Antenna that will make their
SWL'ing more interesting and enjoyable.

RC - What you have written and the tone that you take would
simply turn most new SWL'ers off.

iane ~ RHF
..
..
= = = Richard Clark wrote in message
= = = . ..
On 29 Jun 2004 11:30:01 -0700, (RHF) wrote:

RC (KB7QHC),

Spoken (written) like a True Amateur, and precicly why most SWLs
ignore what is written in reply to SWL 'type' Antennas questions
by HAMs.

Strange logic to offer that a listener comes here to post a query they
will ignore in anticipation. Rather self serving argument isn't it?

Most SWLs work to get the best signal (cleanest signal and lowest
noise) they can to be able to listen to what they what to hear.

There is nothing in this statement that distinguishes amateur from
listener. Further, it contains absolutely no technical material to
support any sense of this exclusivity of concern. To respond in kind,
you don't even rise to amateur status.

But there is a real difference between the radio receiving focus
of a SWL'er and a HAM.

I simply offered my opinion and nothing more; but feel free to
use all the Technical Material you feel necessary to support
your position.

I have never claimed 'amateur' "Status"; and I did not think
that on Rec.Radio.Shortwave a License was required.
..
..

The HAM would hardly ever consider a 'random' wire Antenna;

Now this is a statement that is clearly in error.
The archives will attest to this.

This may be a matter of perception and degree.
..
..

but to the SWL'er the "Random" Wire Antenna 'concept' is a
natural to fill their available space. Power handling, gain
and antenna design characteristics are the focus of the HAM.

As they are no more or less for a listener. If you find some other
motivation, it is strictly your own prejudice.

? motivation ? prejudice ?
..
..

As far as the AM/MW Loop Antenna's are concerned. For the AM/MW
DX'er these Antenna's perform the best for their size and the
available space that the average Broadcast Listener (BCL) has
for these Medium Wave Band. The SWL'er wants to hear any Radio
Station out there from any direction.

Perhaps you should attend this board more often to learn the
fundamentals. There is no impediment to hearing any Radio Station out
there from any direction with simple verticals. SW sets come with
them you know.

Yes many 'portable' SW Radio have small Whip Antennas built-in
to the radios. But to the SWL'er attempting to use an External
Antenna to Hear-More. A Vertical Antenna that is subject to
more RFI/EMF would not be my first suggestion. A Horizontal
Random Wire or Inverted "L" Antenna using Low Noise design
concepts would be what I would recommend.

Here are Three Links to give you an idea of what I am talking about:
http://www.anarc.org/naswa/badx/ante...e_antenna.html
http://www.anarc.org/naswa/badx/ante..._longwire.html
http://www.anarc.org/naswa/badx/antennas/grounding.html
..
..

The 'focus' of the SWL'er is simpy different then the Amateur;
and the majority of SWL'ers are Program Listeners who seldom
listen to the HAM Bands.

So why are you posting to an amateur group? Why an antenna group?
You would be better served through your self-imposed limitations by
staying out of the fast lane.

The initial poster cross-posted the original Post to three NewsGroups.
1. rec.radio.shortwave
2. rec.radio.amateur.antenna
3. nl.radio.amateur

Then to just two:
1. rec.radio.shortwave
2. rec.radio.amateur.antenna

This reply is ONLY to: Rec.Radio.Shortwave {RRS}

I have never claimed 'amateur' "Status"; and I did not think
that on Rec.Radio.Shortwave a License was required.
..
..

73's
Richard Clark, KB7QHC, WPE0EPH

p.s. if the WPE0EPH is unknown to you, it denotes my having been a
Shortwave listener for 40 years and registered with the Popular
Electronics DX club (as well as a sack full of others from around the
world).

"Were You a WPE ?"
http://www.qsl.net/wb1gfh/swl.html
http://www.w8pgw.org/node/view/386
http://www181.pair.com/otsw/WPE.html

WDX Monitor Services
P.O. Box 9
Collingswood, NJ 08108
http://kc5jk.tripod.com/sitebuilderc...files/wdx.html

Short Wave Listening group issues call signs and awards
http://ej.typepad.com/k8zrh/2003/10/...wave_list.html
Short Wave Amateur Radio Listening (SWARL)

COMMENTARY: SWL CALL SIGNS / DYING HOBBY
http://www.worldofradio.com/dxld3169.txt
DX LISTENING DIGEST 3-169,
September 21, 2003
Edited by Glenn Hauser

..

starman wrote:
John Doty wrote:

Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.


What is the actual coupling process between common and differential mode
at the far (antenna) end of the coax?

Consider first an open circuited coax cable hanging in mid air. In coax,
the common mode is carried only on the shield, while the differential
mode is carried by opposing currents on the shield and center conductor.
Since the shield is open circuited, the sum of the common mode and
differential mode currents on the shield must be zero at the end. But
the differential mode current must also be zero, since the center
conductor is open circuited. We therefore conclude that the common mode
current must also be zero at this point: the shield current cannot be
balanced by driving a differential mode current.

Now attach a wire to the center conductor. Now a current can flow out
from the center conductor to the wire, so the common mode shield current
can be balanced by a differential mode shield current: the common mode
energy thus drives a differential mode current.

The misnamed "magnetic longwire balun" doesn't help here, since it can't
suppress this coupling without also suppressing the coupling of the
antenna to the differential mode: it has no way of distinguishing the
current from energy coming down the wire from the current due to energy
coming up the coax.

If you connect the shield to an infinite, perfectly conducting ground
plane, all of the common mode current flows that way. This is why a
ground stake at the feedpoint helps (although in real life it's not
perfect).

With a balanced antenna things are generally better, but more
complicated: without a balun, the common mode on the coax will excite a
combination of common and differential modes on the antenna. A balun can
help, but practical baluns are not ideal devices.

Furthermore, the common mode on the coax can couple electrostatically or
magnetically to nearby conductors like the antenna. Careful orientation
of the line with respect to a balanced antenna can minimize this, but
it's difficult to avoid some coupling in practice.

Given that the methods for decoupling the common mode from the
differential mode at the antenna are imperfect, it's often a good idea
to try to keep the common mode energy away from the antenna in the first
place.

-jpd

Nou weet ik wat ze in plaats van dat Morse hadden moeten doen: Engels.

73 Hans, PA0H

"Mark1" wrote in message
...
Meindert Sprang bracht volgend idée uit :
"Mark1" wrote in message
...
pse remove the nl newsgroup from this discussion.

Loop niet zo te zeuren Mark1, deze draad is gestart door een Nederlander
(Kees) en ge-crosspost naar twee engelse groepen. Dus dat deze heren
hier
steeds weer terugkomen is gewoon deel van de originele discussie.

Meindert

Wat een onzin Meindert, ik vraag gewoon of ze deze nieuwsgroep eruit
willen halen, het is en blijft een Nederlandse nieuwsgroep.

De 'draad' is gestart door Kees met reclame maken voor zijn website met
daarop zijn eigen gebouwde antenne, daar staat netjes bij dat hij wel
vragen wilt beantwoorden, nou prima maar dan wel op zijn e-mail adres
graag.