Richard Clark wrote in
:

On Sat, 02 Jan 2010 13:21:03 -0600, Lostgallifreyan
wrote:

Well, my plan is to use a ground at the antenna end, right
underneath it.

This bodes ill if you do not tie that ground directly to the service
ground. Further, a "ground" as you describe it (incompletely) sounds
suspiciously like a ground rod. This is NOT the same thing as RF
ground - not even close unless you live within several meters of low
tide along a major ocean shore.

I'll get a
good 4' ground rod and rig up an 18' vertical whip as I learned of in
details I posted about earlier.

Suspicions confirmed....

I understand that good reception depends on a good
compromise between selectivity and sensitivity, and no doubt the antenna
'tuner' helps with that, though I'll mainly be concerned with good
ground and local common mode noise rejection.

This does not acknowledge the significance of INTERMOD problems.
Experience may have to teach that (when you make all these
improvements and have poor results for your effort).

My first attempt at the line between
antenna and receiver will be a balanced line with a toroid at each end
for current isolation

This is a very, very curious novelty. You do not describe a
"balanced" system with a ground rod and vertical, so any effort at
"balanced" lines is window dressing only. The reason for placing
"balanced" within quotes is due to the inordinate care and skill
required in obtaining a balanced design. It is more often achieved
with coax. Too often, "balanced line" is approached with the
mysticism of universal relief for whatever ails a listener.

and possibly the suggested Norton preamp on the receiver
input,

I must have missed that posting. Sounds like another elaboration.

but I'll try without it first as I suspect I'll get enough signal
strength to satisfy me for a while. If I have to use coax I will but
I'll try the easier options first. This basic plan does involve a 10:1
ratio in windings on the far end toroid which should help smooth out
peaks of resonance as described by John Doty and others as mentioned
before, and if nothing else, drives a stronger current in the balanced
line part of the system.

This is the doohickey I spoke of. It is basically the refuge
accessory of the lowfers where the span of frequencies is, maybe,
three to one and not like the ten to one of HF SWLing.

I'm no longer much concerned about matching impedances, but I will be
watching for results of changing antenna length if resonance seems to be
an issue.

This is at cross purposes. You don't have many realistic options of
changing antenna length (height) as you do with a simple tuner when it
comes to matching.

My interest in the 'doohickey' or any other widget was mainly in what
appeared to be a means of reducing the difference in signal strength
extremes due to resonance. I understand that if I subsequently have to
select the weaker of two close stations I'll either have to add some
'trap' for a specific offender, such as a trimmed lengh of unterminated
coax (though as far as I know, that trick is usually reserved for much
higher frequencies), or use a manually tuned system which I'll explore
if it becomes a dominant concern.

Traps don't work very well for adjacent AM/SSB stations, you need
cascade XTAL ladders to do that. Tuners, also, can only operate
within the combination of number of reactive elements and Q.

Please respond to your perception of the problem of INTERMOD as it is,
as I said, the silent killer of reception.

73's
Richard Clark, KB7QHC


I haven't a clue about intermod, yet. One thing at a time. Right now I see at
least three contradictions (re ground rods, transformers, and feedlines) with
advice from several people, one of which (the guy who wrote the description
of the antenna and balanced line I mentioned) is part of a group of hams who
is turned to for advice by the others. No guarantee of correctness, perhaps,
but if I keep on being told I'm wrong when my stuff is coming as directly as
I can get it from others with experience, then as far as I'm concerned I'll
do what I think best and get out of the crossfire. Specifically, many times
I've seen advice that service grounds are not adequate because of common mode
noise and local currents, hence the ground rod you vehemently negate. I can
ground to service ground at near end but if the receiver is on batteries, not
connected to anything except a transformer coupling RF from the antenna, then
the ground only needs to be at the antenna end, according to advice I've seen
in several places. Even if I do ground to a water pipe or other local ground,
all advice I see until now insists on having a ground rod as close to the
antenna as possible, no matter what else I do, yet now you urge against this.
I will stop asking for advice if all I see is vigorous contradiction between
people who claim knowledge I do not have. Diverting that disagreement to one
with me doesn't alter this, I did not originate the info behind the choices I
am considering. Even if all the various contributors come here and duke it
out between them it appears I'll be none the wiser.

Lostgallifreyan wrote in
:

...several people, one of which (the guy who wrote the description
of the antenna and balanced line I mentioned) is part of a group of hams
who is turned to for advice by the others.

To save time:
"http://www.kongsfjord.no/dl/Antennas/The%20Best%20Small%20Antennas%20For%20M
W,%20LW,%20And%20SW%20rev%202.pdf

The start page for that link is here;
http://www.kongsfjord.no/dl/dl.htm"

(Copied from a post by 'amdx' earlier in this thread). The line IS balanced,
as it carries only its own internal current, driven by an isolated coupling
with the antenna circuit. Anyway, if he's wrong, there's not much point in
taking it up with me, for obvious reasons. He wrote that. I didn't.

Lostgallifreyan wrote in
:

He wrote that. I didn't.

Sorry amdx, potential for confusion there... I mean the guy who wrote what
you linked to..

"Lostgallifreyan" wrote in message
. ..
Lostgallifreyan wrote in
:

He wrote that. I didn't.

Sorry amdx, potential for confusion there... I mean the guy who wrote what
you linked to...

The Sangean ATS-909 along with similar radios are designed to resolve
signals from the whip antenna or in built ferrite antenna. Attaching 8 to 10
feet of wire to the whip will bring in more stations but depending on
location may well pick up so much extra signal as to cause intermodulation
and AGC limiting preventing reception of the weak signals you want to
receive.

As stated earlier, the front end of these receivers is wide open and the
front end is exposed to the complete spectrum of transmissions received by
the antenna.

There is nothing inherently wrong with the receiving system you have decided
upon but it will undoubtably overload your receiver with signals and you
will be puzzled as to why the reception seems poorer with more noise pickup
rather than less.

As Richard has stated you need some form of preselection to filter out the
unwanted signals before they get into your radio. Basically this is a
tuneable filter which only allows through a single band of frequencies at a
time. The following site explains the essentials.

http://www.dxing.com/tnotes/tnote07.pdf

You can buy commercial preselectors but they will probably cost as much as
your radio. As they are generally passive devices built from a set of
switched coils and a variable capacitor they last forever and old ones do
come up from time to time at junk sales and the like. It is possible to make
a simple filter to cover just one or two bands that interest you.

By all means, try the external antenna system but be prepared to buy a
'better' receiver with front end band pass filters or a preselector.

You can have too much of a good thing when it comes to receiving antennas. A
bigger receiving antenna won't bring in signals from further away. If they
are there, the receiver is probably sufficiently sensitive to pick them up
already. What the bigger antenna will do is raise the level of all the
signals it is picking up and feeding into the receiver and that includes
noise, and other unwanted stations. That is why you need additional
filtering to cut down the unwanted signals and allow your receiver a fair
chance of demodulating what you actually want to hear.

Regards

Mike G0ULI

"Mike Kaliski" wrote in
:

There is nothing inherently wrong with the receiving system you have
decided upon but it will undoubtably overload your receiver with signals
and you will be puzzled as to why the reception seems poorer with more
noise pickup rather than less.


One reason I chose it is that it isn't trying that hard for extreme signal
capture. It appeared to be small, easy to use where I have limited space, and
include a transformer that I have read in numerous places partially solves
one of the main reasons for strongly differing signal strength with
frequency.

As Richard has stated you need some form of preselection to filter out
the unwanted signals before they get into your radio. Basically this is
a tuneable filter which only allows through a single band of frequencies
at a time. The following site explains the essentials.

http://www.dxing.com/tnotes/tnote07.pdf


Looks good, I'm not keen on lots of widgets as it happens, fewer and better
widgets that co-operate well works better for me.

You can buy commercial preselectors but they will probably cost as much
as your radio. As they are generally passive devices built from a set of
switched coils and a variable capacitor they last forever and old ones
do come up from time to time at junk sales and the like. It is possible
to make a simple filter to cover just one or two bands that interest
you.

By all means, try the external antenna system but be prepared to buy a
'better' receiver with front end band pass filters or a preselector.


The pre-selection thing isn't a problem, I can see why that helps, and did so
much earlier than now. The point that disconcerts me strongly is what appears
to be significant difference of opinion between experts, especially when it
applies to things as well established as ground rods. Again, this is why I
won;t just ask questions. Context is clearly everything, so instead I
describe the whole scheme I'm considering. Ultimately it's quicker that way.

On Sat, 02 Jan 2010 17:33:03 -0600, Lostgallifreyan
wrote:

To save time:
"http://www.kongsfjord.no/dl/Antennas/The%20Best%20Small%20Antennas%20For%20M
W,%20LW,%20And%20SW%20rev%202.pdf

An example of invention driving the discussion rather than the need
being satisfied.

Simply put, there is absolutely no reason to use a "balanced" line. It
is window dressing for the circuit which IS balanced (and balanced for
no apparent reason for this unbalanced source). Metaphorically, it is
like adding a clutch to an automatic shift. Yes, you can do it. It
might appear to be elegant. It will certainly work. But why?

Try asking why the trappings of this novel design don't bring some
solution in a new thread. You might stumble at offering the problem
it pretends to solve. (I will anticipate it has something to do with
noise, THIS will certainly raise a lot of catcalls.)

73's
Richard Clark, KB7QHC

On Sat, 02 Jan 2010 17:20:24 -0600, Lostgallifreyan
wrote:

I haven't a clue about intermod, yet. One thing at a time.

The term Intermod is probably mis-direction if you research it.
Basically, if an nearby AM/FM/TV transmitter (and nearby can be on the
scale of several miles) happens to excite your antenna; then its
developed voltage will overload the frontend (Intermod follows, but
the products are not what I am emphasizing here). This overload can
be many, many kHz, or MHz from the intended and tuned signal; and yet
this frequency remote signal will develop an AGC that drives down gain
on your intended signal.

This characteristic is VERY common for untuned frontends in modern
receivers. It is not often noted for poor antennas (those whips, when
they are used for SW), but when a real antenna is attached *BINGO*
sensitivity goes down the toilet. By providing a tuned input, the
side-signal that would otherwise silently drive AGC is attenuated, and
AGC is developed only by the in-band signals.

Right now I see at
least three contradictions (re ground rods, transformers, and feedlines) with
advice from several people, one of which (the guy who wrote the description
of the antenna and balanced line I mentioned) is part of a group of hams who
is turned to for advice by the others. No guarantee of correctness, perhaps,
but if I keep on being told I'm wrong when my stuff is coming as directly as
I can get it from others with experience, then as far as I'm concerned I'll
do what I think best and get out of the crossfire.

A reasonable posture.

Specifically, many times
I've seen advice that service grounds are not adequate because of common mode
noise and local currents, hence the ground rod you vehemently negate.

I don't negate its use, I say that it is NOT RF ground. If you tie
this ground rod to the service ground, then that wire will probably
act more in your behalf than either "ground." There is a world of
difference between safety grounds (what those rod-thingies are) and RF
grounds (which often don't go into ground at all).

Ground is a long and rich story that has been celebrated in this group
for years. It deserves respect and attention well beyond these few
words.

I can
ground to service ground at near end but if the receiver is on batteries, not
connected to anything except a transformer coupling RF from the antenna, then
the ground only needs to be at the antenna end, according to advice I've seen
in several places.

To your specific arrangement - quite true. However, many who have
claimed to have made every precaution then connect their receiver to
an amplifier, computer, what-you-might-call-it and a new path to
ground winds its way through interesting environments that are RF
rich.

Even if I do ground to a water pipe or other local ground,
all advice I see until now insists on having a ground rod as close to the
antenna as possible, no matter what else I do, yet now you urge against this.

I urge against mixing grounds. Such things arrive by the most benign
and seemingly inconsequential actions.

I will stop asking for advice if all I see is vigorous contradiction between
people who claim knowledge I do not have. Diverting that disagreement to one
with me doesn't alter this, I did not originate the info behind the choices I
am considering. Even if all the various contributors come here and duke it
out between them it appears I'll be none the wiser.

Attention to one detail at a time helps, but a lot of this arrived
through responding to the query for antenna port Z. Those adjuncts
that massage input/output Z also fold in the discussion of ground.

Convention has it that you start a new thread for each side-topic that
drives you into conniptions. Asking about the facts and foibles of
ground would be a good start on a new thread - especially when Art's
wet-dreams descend into discussion of particle duality self
annihilation driving all participation away from antenna design. For
instance "Why are ground rods considered insufficient for RF
application?"

I am content to respond to either discussion.

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

On Sat, 02 Jan 2010 17:20:24 -0600, Lostgallifreyan
wrote:

I haven't a clue about intermod, yet. One thing at a time.

The term Intermod is probably mis-direction if you research it.
Basically, if an nearby AM/FM/TV transmitter (and nearby can be on the
scale of several miles) happens to excite your antenna; then its
developed voltage will overload the frontend (Intermod follows, but
the products are not what I am emphasizing here). This overload can
be many, many kHz, or MHz from the intended and tuned signal; and yet
this frequency remote signal will develop an AGC that drives down gain
on your intended signal.

This characteristic is VERY common for untuned frontends in modern
receivers. It is not often noted for poor antennas (those whips, when
they are used for SW), but when a real antenna is attached *BINGO*
sensitivity goes down the toilet. By providing a tuned input, the
side-signal that would otherwise silently drive AGC is attenuated, and
AGC is developed only by the in-band signals.


Ok, this is cool, I understand that, and I also see that it doesn't really
concern intermodulation products as the initial problem is a bigger one if it
occurs. Can't help wondering why a receiver doesn't do some tuning before the
AGC for exactly this reason, but never mind...

Right now I see at
least three contradictions (re ground rods, transformers, and feedlines)
with advice from several people, one of which (the guy who wrote the
description of the antenna and balanced line I mentioned) is part of a
group of hams who is turned to for advice by the others. No guarantee of
correctness, perhaps, but if I keep on being told I'm wrong when my
stuff is coming as directly as I can get it from others with experience,
then as far as I'm concerned I'll do what I think best and get out of
the crossfire.

A reasonable posture.

Specifically, many times
I've seen advice that service grounds are not adequate because of common
mode noise and local currents, hence the ground rod you vehemently
negate.

I don't negate its use, I say that it is NOT RF ground. If you tie
this ground rod to the service ground, then that wire will probably
act more in your behalf than either "ground." There is a world of
difference between safety grounds (what those rod-thingies are) and RF
grounds (which often don't go into ground at all).

Ground is a long and rich story that has been celebrated in this group
for years. It deserves respect and attention well beyond these few
words.


True, I don't doubt that for an instant, but it's also a question of what is
practical, and what is recomended by most people I've read words from at
times during the last 30 years or more. While I know that CB'ers would just
stick a magmount on their car's steel rooftop as often as not, and have read
of other schemes that place some small horizontal plate below the antenna,
there's a lot of scope between that and a rod driven into salty ocean
shoreline. Most people I ever came across asserted the importance of a ground
rod local to the antenna to couple with the local water table which is as
close as most ever get to the ocean unless they really like getting their
feet wet while they sit around at home. The proximity is as close to the
point where they want to pick up RF as they're going to get, and means less
noise from buildings full of electrical stuff picked up on metal between
antenna and whatever other ground might be provided elsewhere. This has been
the ONE common factor in pretty much everything I've seen on land-based AM
reception. Anything that directly appears to negate that advice makes it hard
to know what to trust, and certainly needs to be clearly explained.

I can
ground to service ground at near end but if the receiver is on
batteries, not connected to anything except a transformer coupling RF
from the antenna, then the ground only needs to be at the antenna end,
according to advice I've seen in several places.

To your specific arrangement - quite true. However, many who have
claimed to have made every precaution then connect their receiver to
an amplifier, computer, what-you-might-call-it and a new path to
ground winds its way through interesting environments that are RF
rich.


I agree. The moment I try to connect to a system that includes a computer,
mixer, multiple supply grounds, as mine does, I'll be using a local
service ground and improving it the same as I would for audio, though it's
currently ok for that, at least. It already uses a star grounding system
where possible, as recommended by audio studio designers and others. There's
actually a supply ground rod outside the front door too, which presumably
helps more than the original wiring 15 years ago which didn't have that. (But
note below, where I mention isolation).

Even if I do ground to a water pipe or other local ground,
all advice I see until now insists on having a ground rod as close to
the antenna as possible, no matter what else I do, yet now you urge
against this.

I urge against mixing grounds. Such things arrive by the most benign
and seemingly inconsequential actions.


Hence the star network I mentioned, advised for audio setups.. It's kind of
why I wonder about what many suggest, grounding a coax at both ends, and even
in the middle if you want, and certainly to bury it. More importantly it's
why the Dallas Lankford design appeals to me. Isolation baluns that transfer
energy rather than use direct contact coupling look like a good way to avoid
the ground problems while also avoiding local noise pickup because the twin
cable will have good common mode rejection as it passes into the electrically
noisy bulding. (Though I can't help wondering if Dallas Lankford also tried
balanced microphone cable with a screen grounded at one end, just to see what
happened) Such methods have long been used in audio; is RF below 30 MHz
really so different in this case? So long as that line doesn't have dire
resonances of it's own, isn't attenuation the only big risk? Dallas Lankford
certainly thinks it works after working with it for at least 2 years. He says
that if you do it as described it will be low noise. (As opposed to
'reducing'). I don't think he's claiming any means of reduction, just saying
it's lower relative to inherently noisier systems, if wired as decribed.
Based on what I know, the claim seems good.

I will stop asking for advice if all I see is vigorous contradiction
between people who claim knowledge I do not have. Diverting that
disagreement to one with me doesn't alter this, I did not originate the
info behind the choices I am considering. Even if all the various
contributors come here and duke it out between them it appears I'll be
none the wiser.

Attention to one detail at a time helps, but a lot of this arrived
through responding to the query for antenna port Z. Those adjuncts
that massage input/output Z also fold in the discussion of ground.


Agreed. But this is why instead of asking more questions whose answers I am
probably not prepared for, I described the simplest and apparently best
scheme I'd learned of so people see it whole and work from there...

Convention has it that you start a new thread for each side-topic that
drives you into conniptions.

Ah. Well, I thought that's exactly what would annoy people most. If
something directly arises from discussion in a thread, most people tend to
keep it there. I already do start a new one if I'm certain the issue is
different, and if I'm originating it.

Asking about the facts and foibles of
ground would be a good start on a new thread - especially when Art's
wet-dreams descend into discussion of particle duality self
annihilation driving all participation away from antenna design. For
instance "Why are ground rods considered insufficient for RF
application?"

I am content to respond to either discussion.

73's
Richard Clark, KB7QHC


Well, sure, if I am asking a direct technical or practical question. But
while I'm still slightly reeling from what appears to be a dissention with
what otherwise appears to be good advice, I like to keep the discussion in
one place, otherwise confusion reigns and spreads to many threads. Trust me,
that might annoy people. At least in this thread it might be useful to
anyone who has that radio.

On Sun, 03 Jan 2010 05:26:32 -0600, Lostgallifreyan
wrote:



Most people I ever came across asserted the importance of a ground
rod local to the antenna to couple with the local water table which is as
close as most ever get to the ocean unless they really like getting their
feet wet while they sit around at home.

In fact, this almost always NEVER happens. Skin effect defines the
layer depth of RF in ground. An 8 foot rod is like a splinter when
you are trying to harpoon a Blue Whale.

Ground rod engineering has been discussed in this forum to great depth
(pun intended, or not). The rods are as well understood as water
witching forks. In the HF region, single or several rods have no
practical RF use whatever. Above HF, absolutely no one gives them any
thought.

The proximity is as close to the
point where they want to pick up RF as they're going to get, and means less
noise from buildings full of electrical stuff picked up on metal between
antenna and whatever other ground might be provided elsewhere. This has been
the ONE common factor in pretty much everything I've seen on land-based AM
reception. Anything that directly appears to negate that advice makes it hard
to know what to trust, and certainly needs to be clearly explained.

When you can't do anything else that is effective, a ground rod seems
like more than enough. It is certainly a need for safety's sake,
especially when your vertical could be a lightning magnet. Consider
that same antenna: is it directly GROUNDED? Or is it floating? If
ground is a panacea, I bet most of your advisors immediately isolate
their antenna from it. One has to wonder about faith....

Either design works with equal efficiency. You simply need a coupling
system to the grounded antenna design. One method is using a folded
monopole. Other methods abound (which are often confined to yagi
driven element discussion, but are eminently applicable here).

The moment I try to connect to a system that includes a computer,
mixer, multiple supply grounds, as mine does, I'll be using a local
service ground and improving it the same as I would for audio, though it's
currently ok for that, at least. It already uses a star grounding system
where possible, as recommended by audio studio designers and others. There's
actually a supply ground rod outside the front door too, which presumably
helps more than the original wiring 15 years ago which didn't have that. (But
note below, where I mention isolation).

The Star system is great for exactly as you understand and describe
it, but for antenna applications that remote ground could act as a
suicide adapter if it does not have its own path to the service
ground. Yes, this violates the star, but when path lengths include a
lot of resistance and leakage current, voltages can become
considerable when you supply a new avenue through your home. This is
the story of the classic ground loop.

Hence the star network I mentioned, advised for audio setups.. It's kind of
why I wonder about what many suggest, grounding a coax at both ends, and even
in the middle if you want, and certainly to bury it. More importantly it's
why the Dallas Lankford design appeals to me. Isolation baluns that transfer
energy rather than use direct contact coupling look like a good way to avoid
the ground problems while also avoiding local noise pickup because the twin
cable will have good common mode rejection as it passes into the electrically
noisy bulding. (Though I can't help wondering if Dallas Lankford also tried
balanced microphone cable with a screen grounded at one end, just to see what
happened) Such methods have long been used in audio; is RF below 30 MHz
really so different in this case? So long as that line doesn't have dire
resonances of it's own, isn't attenuation the only big risk? Dallas Lankford
certainly thinks it works after working with it for at least 2 years. He says
that if you do it as described it will be low noise. (As opposed to
'reducing'). I don't think he's claiming any means of reduction, just saying
it's lower relative to inherently noisier systems, if wired as decribed.
Based on what I know, the claim seems good.

I'm not familiar with Dallas Lankford, but isolation and shielding
techniques are topics I have visited professionally throughout the
years and they are not simple. Without a concommitant discussion of
the noise source, one wrong ground selection can wipe out all pursued
benefits. Let's revisit one of your statements above:
balanced microphone cable with a screen grounded at one end
Which end? Any choice stands an equal chance of being the wrong
choice.

73's
Richard Clark, KB7QHC

On Sun, 03 Jan 2010 08:52:46 -0800, Richard Clark
wrote:

I'm not familiar with Dallas Lankford

I have since visited your suggested page to casually view his works.
Interesting set of circuits too (although, some of the phasing systems
have been superceded with shift registers - I used to use
bucket-brigade chips).

I was especially touched to see wide coverage of the R390A. It was
the subject of my first class that I taught in the Navy (along with
the Collins URC-32). Cadillac equipment. I note in his discussion of
stabilizing the BFO, he uses a Rubidium standard for comparison. I
calibrated quite a few of those Rubidium standards too with my Cesium
Beam whenever a Boomer came along side. An URQ-12 would have worked
as easily, but this discussion no doubt exceeds the capacity of your
wallet (the Navy provided such a candy store for my Metrology Lab).

73's
Richard Clark, KB7QHC