On Fri, 28 Oct 2005 11:02:18 -0400, TRABEM wrote:
Is my mission to purposely isolate the loop so that anything happening
in the receiver doesn't impact the loops Q?

The advantage of Q is that it multiplies I and V giving you
sensitivity. As I have pointed out before, your current design could
work without any changes. I cannot answer this for myself much less
you and the advice I would have to offer is that you build your
receiver with flexibility in mind. We are not talking big changes in
components. That is the long answer. The short answer is yes.

If this is the case, an active buffer amp seems inevitable.

Easy enough to include, or remove depending on need.

If I do not buffer the loop from the RX, wouldn't a 2K loop fed into a
2K RX also cause similar loss of Q (just like the 2 ohm over 2 ohm
example you gave previously)?

Certainly, but not similarly. The Q is not going to plunge to 2 or 3.

And, I am definitely not avoiding the I/Q issue. I know of successful
hardware handling examples of the I/Q and also of successful software
handling methods. I just haven't decided which one to use yet.

That is the point of my questions. They are veiled implications, not
tests of knowledge. No one in your list of links, much less those
I've read over the years knows the PRACTICAL implication of the "I"
and "Q" channels. So, I may as well drop the other shoe.

One does the demodulation of AM signals, the other provides
demodulation of FM and SSB signals. I'm not sure which and what
particular arrangement of supporting circuitry is required beyond
simple AM amplifiers because my construction for that application was
back in 68-69. Building tube models and guaranteeing design
considerations was not as simple as the Tayloe circuit offers now.

However, one of the fascinating characteristics of this style of
detector is that you can feed each channel to the earpieces of a
stereo headset. "I" for one, "Q" for the other earpiece. This gives
you the chance to use your wet-ware instead of someone's software and
hardware.

The brain does all the necessary fourier analysis automatically and in
real time. The upshot of it is that when listening to a CW signal,
and hearing the field of signals around it, you perceive those signals
in a mind-space. The signal that is center tuned sounds like it is
between your ears, in the middle of your, as I described it,
mind-space. Those signals that are above it in frequency sound as
though they are coming from the right, and those signals that are
below it in frequency sound as though they are coming from the left.

The advantage of this detector, in this configuration, with this kind
of perception, is that your mind is separating the signals
psychologically. Even though the signals you hear on the left and
right are in equal amplitude to the center, you can exclude them
mentally. Imagine taping a conversation in room full of people and
the microphone is not at your, or your partners lips, but between you,
and you are both standing off a couple of feet talking over the crowd.
You full know that you could understand your partner at the time of
the recording, and you probably know that the tape would be a bitch to
make sense of, even though it makes a faithful record of the
conversation in that free-for-all.

The difference is that your binaural perception with its phase
separation capability could be brought to bear to ignore the field of
noise to concentrate on your partner. When you hear the mono
recording, the phase information is lost and your partner's
conversation merges with the background noise.

I cannot personally vouch for this effect because the payoff in my
construction back then didn't come down to finally evidencing this
effect for myself. This wet-ware characteristic was reported to me to
be one of the attractions of building for my professor. I have also
played with bucket-brigade delay lines to create this effect. At one
time Paul McCartney was using it with his music. Aural phase
relationships have a strong psychological information content that is
taken for granted.

73's
Richard Clark, KB7QHC

Hi Richard,

I feel SO MUCH better now!!!!!!!!

Just read and replied to Reg's latest comments a few minutes ago and
it seems I am on the right track-my major error was not realizing that
my series loop impedance as originally suggested was very much lower
than I thought it to be ...and I've finally realized that it COULD NOT
POSSIBLY be matched to a receiver that had 2 (or 10) ohms input Z.

Now that I've realized my originals series loop antenna had an
impedance in the milliohm region, the other explanations that you gave
made perfect sense.

At least, I feel like I made it to the first level::

I'm a little hesitant to make this suggestion, but let me ask the
question(s) at the risk of taking to large a step forward and
stumbeling::

If you would, just give me a yes or no answer to these questions so I
can make sure I don't have seriously flawed remnants of the old
thinking.....

-------------------------

With the current model of parallel loop...

If my receiver was 2K input impedance (whether tuned input or not),
could I connect it to my loop with a piece of 2000 ohm open wire line
and expect the net (or loaded) Q to be around 100 (assuming a 2K
impedance open wire line could be built and that my unloaded antenna Q
was 200 to start with).

Yes or No?

-------------------------

With the current model of parallel loop...

If I elected to use a buffer amp with megohms of input impedance,
would I preserve the unloaded Q and end up with a net Q of about 200
because I haven't loaded the loop?

Yes or No?

-------------------------

I believe my receiver is microvolt sensitive and that the loop will
deliver a relatively good signal to the receiver even though the loop
isn't terribly efficient. If I build selectivity into the front end of
the receiver, do I really need high Q (200)??

I think the answer is NO.....

Since my receiver is quite sensitive (characterized at uV before I
convert it to VLF), I think I could save a lot of money by sacrificing
some antenna Q and building modest selectivity into the front end.

Or, I could elect to use the antenna as planned (impedance matched,
but no front end tuned circuit) and instead convert the receiver to an
untuned input (allowing the antenna Q to be the sole form of tuning).

Is this reasoning basically correct or seriously flawed?

-------------------------


However, one of the fascinating characteristics of this style of
detector is that you can feed each channel to the earpieces of a
stereo headset. "I" for one, "Q" for the other earpiece. This gives
you the chance to use your wet-ware instead of someone's software and
hardware.

The brain does all the necessary fourier analysis automatically and in
real time. The upshot of it is that when listening to a CW signal,
and hearing the field of signals around it, you perceive those signals
in a mind-space.

OK, I am an avid cw operator, often operating as a hired gun at m/m HF
contest efforts. So, I completely understand the concept of having the
brain do the processing. The brain is a very seriously viable filter
that is adaptive with regard to the audio spectrum sent to it by a
conventional receiver.

I haven't tried actual binaural operation, but have heard others talk
about it. The users claim it is a different world from the very first
second of listening to it and are constantly amazed at the effect and
improvement.

I have a friend who isn't quite local...but we chat from time to time
although we don't see each other that often. He has a high frequency
hearing loss in one ear and has a great deal of difficulty with cw. He
built a binaural project from a QST article and was stunned to hear
the results. He was sold ont he idea in short order!

But I never though much about hooking up a stereo headphone to the i/q
audio streams.

The difference is that your binaural perception with its phase
separation capability could be brought to bear to ignore the field of
noise to concentrate on your partner. When you hear the mono
recording, the phase information is lost and your partner's
conversation merges with the background noise.


OK, I am with you with respect to the brain filtering out unwanted
conversations to let you focus on your conversational partners distant
voice. But, I thought traditional binaural receiver meant that the
frequencies higher than a certain point went to one ear and that the
all the frequencies lower than the same frequency went to the other
ear. In this manner the listener has a feeling of 'depth' or
'richness' that isn't present in a mono setup.

This is interesting though.

But, I never thought that the brain could process the I and Q to
provide opposite (unwanted) sideband rejection...which is why I
thought the primary function of the I/Q precessing was about (whether
it be hardware or software based).

Are you suggesting that the brain can also process the I/Q output
streams and provide opposite sideband rejection as well as selective
frequency and adaptive filtering?

I have also
played with bucket-brigade delay lines to create this effect. At one
time Paul McCartney was using it with his music. Aural phase
relationships have a strong psychological information content that is
taken for granted.


I'll investigate this over the Winter season, which is long and hard
here. Thanks for planting a bug in my ear (no pun intended) about
this. I probably would not have thought of it otherwise.

Regards,

T

On Fri, 28 Oct 2005 14:19:14 -0400, TRABEM wrote:
With the current model of parallel loop...

If my receiver was 2K input impedance (whether tuned input or not),
could I connect it to my loop with a piece of 2000 ohm open wire line
and expect the net (or loaded) Q to be around 100 (assuming a 2K
impedance open wire line could be built and that my unloaded antenna Q
was 200 to start with).

Yes or No?

You have too many suppositions to give a straight answer. First,
there is no such thing as a 2000 Ohm open wire line. As for the gist
of the question:
Yes.

With the current model of parallel loop...

If I elected to use a buffer amp with megohms of input impedance,
would I preserve the unloaded Q and end up with a net Q of about 200
because I haven't loaded the loop?

Yes or No?

Yes.

However, as Tom has pointed out separately, this may not be the
optimal solution.

I believe my receiver is microvolt sensitive and that the loop will
deliver a relatively good signal to the receiver even though the loop
isn't terribly efficient. If I build selectivity into the front end of
the receiver, do I really need high Q (200)??

I think the answer is NO.....

Well, this is a good opportunity to examine that tumble down the slope
to the Q = 2 (caused by the severe loading of your proposed design).

The correlative to this is, how much selectivity do you need in a
field where stateside VLF is relatively rare? Further, by the action
of the strong filtering that usual attends the "I" and "Q" channel
processing, you could easily repair any shortfall.

However, back to that Q = 2. That still offers respectable (not
fantastic) selectivity against signals out at the bottom of the AM
band which is 10f (one decade) away.

OK, I am with you with respect to the brain filtering out unwanted
conversations to let you focus on your conversational partners distant
voice. But, I thought traditional binaural receiver meant that the
frequencies higher than a certain point went to one ear and that the
all the frequencies lower than the same frequency went to the other
ear. In this manner the listener has a feeling of 'depth' or
'richness' that isn't present in a mono setup.

Binaural is what the fellows in white coats mean by listening with two
ears.

This is interesting though.

And rarely reported for this style of detection. What a pity.

Are you suggesting that the brain can also process the I/Q output
streams and provide opposite sideband rejection as well as selective
frequency and adaptive filtering?

The rejection is psychological, not actual. It is what I meant by
"mind-space." The vectors do not add up to zero, the mind simply
ignores the off-band content like you would at a party listening to
that cute office temp's whispers when your wife is yelling across the
room at you.

Listen to a recording of that same scenario in mono and you WILL hear
your wife!

The brain reassembles all delay/phase information content at the party
to sort out what to pay attention to. When that same information is
passed through a monaural channel, the phase information is lost and
everything competes equally lousy given the S/N ratio.

73's
Richard Clark, KB7QHC

On Fri, 28 Oct 2005 13:35:19 -0700, Richard Clark
wrote:

The rejection is psychological, not actual. It is what I meant by
"mind-space." The vectors do not add up to zero, the mind simply
ignores the off-band content like you would at a party listening to
that cute office temp's whispers when your wife is yelling across the
room at you.

Listen to a recording of that same scenario in mono and you WILL hear
your wife!


I understand the Bell Labs explored this effect (which they referred
to as the "cocktail party effect") when exploring the nature of
conversation for the purposes of novel approaches to telephony
multiplexing.

I don't think they developed a technology solution to exploit the
cocktail party effect, but they did incorporate their knowledge of the
statistical / syllabic / sentence characteristics in their Time
Assignment Speech Interpolation (TASI) equipments, and TASI was quite
successful.

I think the term we would use for the cocktail party effect on a phone
channel is "a crossed line", and you may be right in that the loss of
spatial information because of the mono channel may have been the
reason it didn't work.
--

On Fri, 28 Oct 2005 21:10:04 GMT, Owen Duffy wrote:

I don't think they developed a technology solution to exploit the
cocktail party effect, but they did incorporate their knowledge of the
statistical / syllabic / sentence characteristics in their Time
Assignment Speech Interpolation (TASI) equipments, and TASI was quite
successful.

Hi Owen,

This mimics Paul McCartney's use of phase mixing in his music in the
late 70s. Earlier, I was using Reticon bucket-brigade chips to
develop a frequency independent delay line such that I could mix input
and output (much like the FIR/IIR topology of today's DSP technology,
except I was doing it in analog rather than digital) to obtain a
variable phase. I still have the breadbox sitting on the shelf. I
was anticipating using this device to place "voices" in the
stereo-space of program content that I was mixing for. The concept
was much too cerebral for the producer who simply wanted matched
levels.

73's
Richard Clark, KB7QHC

I believe my receiver is microvolt sensitive and that the loop will
deliver a relatively good signal to the receiver even though the loop
isn't terribly efficient. If I build selectivity into the front end of
the receiver, do I really need high Q (200)??

I think the answer is NO.....

Well, this is a good opportunity to examine that tumble down the slope
to the Q = 2 (caused by the severe loading of your proposed design).

The correlative to this is, how much selectivity do you need in a
field where stateside VLF is relatively rare? Further, by the action
of the strong filtering that usual attends the "I" and "Q" channel
processing, you could easily repair any shortfall.

However, back to that Q = 2. That still offers respectable (not
fantastic) selectivity against signals out at the bottom of the AM
band which is 10f (one decade) away.



OK, I'm not sure how we got back to the Q=2 scenario. I think my
proposed design is the old series tuned loop, which I have firmly
rejected.

With no tuning in the front end, the Q of the receiver would approach
1.......Yes, I understand that.

I understand the answer you gave initially, which was 'I think the
answer is NO....'.

I understand the degree of protection against signals in the bottom of
the bc band.

When you said "Well, this is a good opportunity to examine
that tumble down the slope to the Q = 2 (caused by the severe
loading of your proposed design)"...................did you mean
to say or to infer '(caused by the severe loading of your old (now
defunct) series resonant loop design"???

All is in agreement above EXCEPT in not sure why the reference to the
old design.

Thanks again.

T

On Fri, 28 Oct 2005 18:33:23 -0400, TRABEM wrote:

When you said "Well, this is a good opportunity to examine
that tumble down the slope to the Q = 2 (caused by the severe
loading of your proposed design)"...................did you mean
to say or to infer '(caused by the severe loading of your old (now
defunct) series resonant loop design"???

Yes
of course.

You have asked a number of questions outside of this old (now
defunct) design, but you haven't, as far as I can tell, formalized a
replacement.

The ancillary point that I've made is that the original could work.
However, you've never stated any operating specification to test that
against. I've offered that all components need to be scrutinized in
the face of your goal. We saw where that lead.

You've only specified your desire for High Q capacitors (properly, low
D capacitors). I offered that ESRs vary widely and could easily
derail your goal. The presence of an ESR equal to the 0.06 Ohm of the
loop is very well within being guaranteed. It still is. Reg
dismissed this as inconsequential. So be it, but being that it is
easily remedied through selection, then why toss away half your Q to
casual indifference?

What Reg actually meant, and he has a hard time with that given he can
often be found on both sides of an argument, is that such loss may not
matter. There I agree, but this does not advance the topic of High Q
Caps for VLF Loop Antenna when they can be obtained.

73's
Richard Clark, KB7QHC

On Fri, 28 Oct 2005 17:03:55 -0700, Richard Clark
wrote:

On Fri, 28 Oct 2005 18:33:23 -0400, TRABEM wrote:

When you said "Well, this is a good opportunity to examine
that tumble down the slope to the Q = 2 (caused by the severe
loading of your proposed design)"...................did you mean
to say or to infer '(caused by the severe loading of your old (now
defunct) series resonant loop design"???

Yes
of course.



Agreed!

Just wanted to be sure I didn't miss something, so I asked.

And, your're right, I haven't formulated a replacement. I bought a 250
foot poll of cable, and it has not been cut. So, it's still in one
piece and returnable if I decide not to use it.

I was just pondering the alternative of allowing the front end to be
untuned. The receiver is susceptible to harmonics, each harmonic of
the tuned frequency is down 6 db though. Since the loop would be
resonant somewhere on HF, it is probably a bad idea to leave the front
end untuned as HF can be unpredictable. so, I am thinking I need some
front end selectivity.

Reg gave me an example of what he might do. And his antenna came out
much cheaper to build and probably easier to put up.

I'm also thinking about the method of feeding the signal to the house.
It will be around 70 feet from the house, so 90 feet of cable of some
sort is needed. I can easily go 700 feet in any of 3 directions, but
there is probably no practical need to go that far out into the woods.
Since the house is a noisy place for LF and VLF, I have to be
concerned about how I feed the antenna. I also think I'd like to have
it fed with balanced line to minimize the possibility of the feed line
acting as an antenna. If a preamp is used, I have to feed power to the
antenna as well, so I will have to wind a common mode filter to do
that job as well. So, I got a lot to think about.

Although I haven't formulated a plan for a replacement antenna, the
series loop is 99.99 percent history.

So, I am thinking about it.

I have a reading session planned for the late night here so I can
reinforce the lesson(s) you and Reg have taught me. And, will probably
work on the actual antenna design tomorrow. My caps are on order from
Mouser, should be here next week

There are a few preamp designs around the web, but none of them seems
very well thought out...although they might be well planned. It's
possible they are solidly designed, but that the authors haven't
shared all the gory details in their web presentation(s).

Thanks again. I'll keep you posted if you like......I'd appreciate
sending up a red flag if I attempt to commit additional acts of
stupidity with regard to whatever I come up with for a design.

Regards,

T

On Fri, 28 Oct 2005 09:02:14 -0700, Richard Clark
wrote:



That is the point of my questions. They are veiled implications, not
tests of knowledge. No one in your list of links, much less those
I've read over the years knows the PRACTICAL implication of the "I"
and "Q" channels. So, I may as well drop the other shoe.


Didn't Don Stoner describe a synchronous detector way back. I think I
remember reading an article in the mid sixties in "The Sideband
Handbook" or similar.

I was about 15 then, so a detector that had something like 17 bottles
in it seemed overkill when I was copying CW and SSB on an AM receiver
(ie diode detector) with BFO.

The appeal being an all-mode detector (including DSBSC), but
synchrounous detectors didn't seem to catch on in comms receivers,
well not until DSP detection... well I don't recall coming across them
anyway.

Owen
--

On Fri, 28 Oct 2005 20:12:48 GMT, Owen Duffy wrote:

Didn't Don Stoner describe a synchronous detector way back. I think I
remember reading an article in the mid sixties in "The Sideband
Handbook" or similar.

I was about 15 then, so a detector that had something like 17 bottles
in it seemed overkill when I was copying CW and SSB on an AM receiver
(ie diode detector) with BFO.

The appeal being an all-mode detector (including DSBSC), but
synchrounous detectors didn't seem to catch on in comms receivers,
well not until DSP detection... well I don't recall coming across them
anyway.

Hi Owen,

17 bottles indeed. That seems to strike a resonant chord in the
ganglia because my construction was on a utility box of about 3" x 9"
x 15" (not counting power supply requirements). We were working from
a printed article certainly; and to confirm your recollection, there
was a list of modes that could be detected that was long.

My perception of the resurgence of interest in synchronous detection
(it seems to have many names) is that a considerable body of knowledge
evaporated in the 70s and 80s to leave only fragments of what this
detector was useful at.

73's
Richard Clark, KB7QHC