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

Richard Clark wrote in
:

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


Not just my wallet. This is cool though, I have encountered both bucket
brigade IC's and shift registers. Offtopic question: Did the bucket brigade
lead directly to the switched capacitor filter? I ask because they seem
related, and the BB seems to have become obsolete, but the SCF, anything but.

On Sun, 03 Jan 2010 13:10:17 -0600, Lostgallifreyan
wrote:

Did the bucket brigade
lead directly to the switched capacitor filter?

Same thing if I read you correctly.

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

On Sun, 03 Jan 2010 13:10:17 -0600, Lostgallifreyan
wrote:

Did the bucket brigade
lead directly to the switched capacitor filter?

Same thing if I read you correctly.

73's
Richard Clark, KB7QHC


Interesting. I guess fabrication accuracy and timing accuracy improvements
led to its sharp cutoff and improved ability. I'm using one in some project I
have on hold, a way to get pitched sounds to control MIDI signals for musical
instrument control. I'll stop that line of thought there though, I'm not
ready to go into that project for a while.

Lostgallifreyan wrote in
:

It was
the subject of my first class that I taught in the Navy

Curious... You might have experiences that give useful insight into something
I'm discussing in another group, some off-the-wall topic I entered into
during a quiet new-year's moment in alt.lasers... I can accept that you might
not want to get into that at all once you see it but if you do I welcome the
input because as I state there, one issue is to find helpful signals rather
than the noise such discussions usually provoke. But it might be a lengthy
misdirection if you're busy so I won't push the point. But I will say now
that my dad was a naval officer when he was younger and he SAW that thing I
described right there with me, and he had no clue either. I just keep
thinking that some people in the navy might be better able to explain it than
most, especially if they have a strong science or engineering background.

On Sun, 03 Jan 2010 13:25:30 -0600, Lostgallifreyan
wrote:

Lostgallifreyan wrote in
:

It was
the subject of my first class that I taught in the Navy

Curious... You might have experiences that give useful insight into something
I'm discussing in another group, some off-the-wall topic I entered into
during a quiet new-year's moment in alt.lasers... I can accept that you might
not want to get into that at all once you see it but if you do I welcome the
input because as I state there, one issue is to find helpful signals rather
than the noise such discussions usually provoke. But it might be a lengthy
misdirection if you're busy so I won't push the point. But I will say now
that my dad was a naval officer when he was younger and he SAW that thing I
described right there with me, and he had no clue either. I just keep
thinking that some people in the navy might be better able to explain it than
most, especially if they have a strong science or engineering background.

Well, I'm not sure what you are trying to bring up here. As far as
I'm concerned, any topic is open for discussion. If others fume and
fulminate about this being an antenna group, I can easily turn the
discussion into one that is antenna specific.

What did your Dad see? (We used to joke that after the Pueblo
incident they put Marine guards outside of the radio shack for
security. If the ship was in danger of being boarded they were to
step into the shack and shoot the operators. Then I went into the
submarine navy, aboard a tender, the USS Holland, AS-32. We had an
escort sub that followed us at sea - to sink us if the Ruskies got too
close. Ah, the humor of those days.)

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

On Sun, 03 Jan 2010 13:25:30 -0600, Lostgallifreyan
wrote:

Lostgallifreyan wrote in
5:

It was
the subject of my first class that I taught in the Navy

Curious... You might have experiences that give useful insight into
something I'm discussing in another group, some off-the-wall topic I
entered into during a quiet new-year's moment in alt.lasers... I can
accept that you might not want to get into that at all once you see it
but if you do I welcome the input because as I state there, one issue is
to find helpful signals rather than the noise such discussions usually
provoke. But it might be a lengthy misdirection if you're busy so I
won't push the point. But I will say now that my dad was a naval officer
when he was younger and he SAW that thing I described right there with
me, and he had no clue either. I just keep thinking that some people in
the navy might be better able to explain it than most, especially if
they have a strong science or engineering background.

Well, I'm not sure what you are trying to bring up here. As far as
I'm concerned, any topic is open for discussion. If others fume and
fulminate about this being an antenna group, I can easily turn the
discussion into one that is antenna specific.

What did your Dad see? (We used to joke that after the Pueblo
incident they put Marine guards outside of the radio shack for
security. If the ship was in danger of being boarded they were to
step into the shack and shoot the operators. Then I went into the
submarine navy, aboard a tender, the USS Holland, AS-32. We had an
escort sub that followed us at sea - to sink us if the Ruskies got too
close. Ah, the humor of those days.)

73's
Richard Clark, KB7QHC


Antennas? In this case you'd have your work cut out for you. Wasn't just
him who saw it. I saw it first, for an hour and a half, before I decided it
would stick around long enough to justify getting my parents to look at it
too. I'm a bit embarrssed to mention it here other than to point to it there,
but it was two crossed 'beams' in the sky. Trust me, it's hell of a
misdirection if you're not up for it, you'd have to go to alt.lasers and take
a shufti at the posts there.. But I agree, opening it to discussion is good.
I spend about 99.999999% of the time keeping it to myself but I'm getting too
old to want to leave it as unresolved as it is now. If it has to be, ok, but
I ought to try..

Submarines? Those scare me. I never had to go in one, I don't know if
claustrophobia would have beaten me. I have found the sound of water passing
all round me as I waited for sleep in a crew cabin below decks in a ship's
bow to be one of the most comforting sounds I ever knew, so maybe I wouldn't
have.

Richard Clark wrote in
:

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.


True. I'm interested in using a single antenna for all of LW up to around 30
MHz as a simple starting point though, so Dallas Lankford's scheme seems to
fit the bill.

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....


Safety is important, even though lightning strike isn't that big a risk here.
Actually it's risen because nearly all large trees have been removed in the
last two years, and I'd be held reponsible for any damage caused that way.

If you look at that PDF you'll see the 15' whip antenna is directly connected
to ground through 80 turns of wire on a ferrite toroid. I might add a spark
gap in parallel as that wire is not a high current path. So long as it is
much more likely to go to ground rather than along the line in to the house,
I'll have done what I'm supposed to do. The trouble would only exist (other
than unpreventable natural excesses) if it were evident that I had not done
this.

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).


That PDF shows the coupling in this case. It's similar to other ideas
recommended for similar small SW listening setups. Once I have all I need to
try it I'm just as happy to try experimenting to see what happens as to try
any plan. There are some limits though, the location is too built up to
expect much from anything intended to be directional. I'm just intending to
look around, not looking out there for something specific.

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.


Well, a ground rod isn't going to cost much, and making and breaking
connections to it is one of the easiest and cheapest things I'll be able to
do, so I'll test that empirically when I'm ready. I won't try to predict it
now. Whenever I find some new ground noise problem in anything I do here, I
usually manage to isolate it and solve it acceptably within an hour or less,
so I'll trust my chances. Usually the purpose hasn't been for RF, but quite
often the sources did involve RF too so my instincts might help me more than
my knowledge.

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.


Well, I did think of that. And I didn't state it because I didn't know for
sure. As I imagine that local RF couplings from various digital devices might
place small currents on the local ground, I imagine that grounding a shield
at the remote ground makes sense. Doesn't matter to me though. It's far
easier and faster to experiment than to try to predict because there are only
two ways to try. Dallas Lankford directly states that no shield is even
required, and I doubt he'd have said that if he couldn't demonstrate it, and
as that line is a two-wire loop that has no direct contact with anything, it
should reject any common mode noise that hits it. Even in audio this matters
because the same method is used to reject RF pickup on audio lines. I think
some people persist in baluns instead of op-amp common mode rejection specs
for this reason, despite the chances of modest distortion in audio bands from
the transformers used. Not entirely relevant but it illustrates how people
can find themselves choosing between two less-than-ideal circumstances for
best effect.

I understand that noise context matters for a real attempt to plan for it,
but that's far more difficult that presenting the basic antenna scheme.