Topband: Fine sigs from George, FO/AA7JV on 80 cw this morning
W3HKK at roadrunner.com
W3HKK at roadrunner.com
Tue Apr 4 13:09:15 EDT 2023
I looked for George for the 3rd straight day on 160, but no copy.
However there he was on 3527.5 at 1107z, with a very nice 579 sig and
I quickly put him in the log. Well after my sunrise hr in Ohio I saw
spots for him on 160 cw from several West Coast US stations.
Havent heard a dx station on 160 at my SR for at least three days now,
but had some nice short contacts with assorted VK's on 40 and 20 ssb
around 1130z. Pulled 9U5RU out of the noise on 10m ssb shortly
thereafter, so some sigs have been there for the taking.
The VKs on 20 ssb were 5 S units stronger on the LP when I first
contacted them, but at the end of the qso they were just 2 S units
stronger LP. Wonder what else was coming through that I may have
missed?
-----------------------------------------From:
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To: topband at contesting.com
Cc:
Sent: Tuesday April 4 2023 12:00:44PM
Subject: Topband Digest, Vol 244, Issue 4
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Today's Topics:
1. Re: High Impedance RX Antennas (Dennis W0JX)
2. Re: High Impedance RX Antennas (Frank W3LPL)
3. Re: High Impedance RX Antennas (Tree)
4. Re: High Impedance RX Antennas (Don Moman VE6JY)
5. Re: High Impedance RX Antennas (John Kaufmann)
6. Re: [PVRC] 2-element receiving arrays (Dave Cuthbert)
7. Re: High Impedance RX Antennas (Jim Brown)
----------------------------------------------------------------------
Message: 1
Date: Mon, 3 Apr 2023 16:42:37 +0000 (UTC)
From: Dennis W0JX
To: "topband at contesting.com"
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset=UTF-8
There is an old saying "The enemy of good is perfect."? You will be
driven crazy by chasing down every slight variance from the ideal.
That being said, it is important to check out the obvious areas where
flaws can create big problems. Indeed, the feedline coax, typically
RG6 CATV line, is a major contributor to array performance problems.?
The cheap, big box cable is covered with PVC and that stuff hardens
and tightens up over the years. This allows water to enter the shield
and the water easily migrates for long distances, creating a high
resistance. Spend the money upfront and buy quality cable that is
flooded.
The idea of using cable that has a solid copper conductor has merit.
But even with that, a bare copper conductor will oxidize over time. I
find myself cleaning these conductors on an annual basis with the
eraser end of a pencil (recommended by Lee K7TJR).
I have also had F connector failures on my combiner box and on a
common mode choke. Sometimes the imported female connector center
contact just fails for no reason. The alternative Amphenol connectors
are very expensive at about $8+ each but I am considering replacing
the connectors with these higher grade parts.
Also, the so-called "water-proof" compression connectors are often
not. The connection must be waterproofed effectively.? Also,
condensation from humidity can be a big problem. Here is northeast
Ohio, the environment is humid for the majority of the year. I have
poured water out of a 75 ohm preamp that was sheltered in a good
enclosure!
These complex phasing arrays are by no means plug and play. Each
installation will be unique depending on layout and surrounding
objects. There are three tools necessary to get them and keep them
working:? 1.) a good portable signal source to feed the antenna
preamps (I use an Elecraft XG-3 with a home brew impedance transformer
at the input);? 2.) a portable transceiver to measure signal out of
the system at various points (My KX3 does a great job); and an
accurate antenna analyzer to measure impedances and to measure
feedlines and phasing lines for the proper electrical lengths. N6RK is
right. There can be considerable difference in RG6 impedance so you
need to check it out.?
73 Dennis W0JXMilan, OH
------------------------------
Message: 2
Date: Mon, 3 Apr 2023 13:11:27 -0400 (EDT)
From: Frank W3LPL
To: topband
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset=utf-8
Another highly recommended tool is a Time Domain Reflectometer.
Tt easily detects any abnormalities in my 8-circle and 4-square
arrays and stacked HF Yagi arrays and switches.
Other than my hand held antenna analyzer, my hand held TDR is my
most often used and most valuable tool for proving that the
performance
of my antennas and feedlines has not changed from prior measurements
and identifying and isolating faults before they cause partial or
total failure. A TDR can detect, diagnose and locate feedline and
antenna faults from the comfort of your ham shack.
Affordable TDRs are often available on eBay. Some antenna
analyzers have rudimentary TDR capabilities but I've never used
an antenna analyzer with TDR capabilities comparable in
performance to a TDR.
Long before moisture causes coax failure, it causes the impedance
of the coax to change, a potentially big problem in a phased array
or stacked Yagis. A TDR easily detects and locates the problem
before it causes a failure.
An antenna analyzer can also detect that moisture has caused
an impedance shift in coax cable. Place a dummy load (with the
same impedance as the coax) at one end of the coax cable. Sweep
the antenna analyzer frequency. As you do a frequency sweep the
VSWR and impedance should not change. If it does, moisture is
probably eating away inside your coax.
73
Frank
W3LPL
----- Original Message -----
From: "Dennis W0JX via Topband"
To: "topband"
Sent: Monday, April 3, 2023 4:42:37 PM
Subject: Re: Topband: High Impedance RX Antennas
There is an old saying "The enemy of good is perfect."? You will be
driven crazy by chasing down every slight variance from the ideal.
That being said, it is important to check out the obvious areas where
flaws can create big problems. Indeed, the feedline coax, typically
RG6 CATV line, is a major contributor to array performance problems.?
The cheap, big box cable is covered with PVC and that stuff hardens
and tightens up over the years. This allows water to enter the shield
and the water easily migrates for long distances, creating a high
resistance. Spend the money upfront and buy quality cable that is
flooded.
The idea of using cable that has a solid copper conductor has merit.
But even with that, a bare copper conductor will oxidize over time. I
find myself cleaning these conductors on an annual basis with the
eraser end of a pencil (recommended by Lee K7TJR).
I have also had F connector failures on my combiner box and on a
common mode choke. Sometimes the imported female connector center
contact just fails for no reason. The alternative Amphenol connectors
are very expensive at about $8+ each but I am considering replacing
the connectors with these higher grade parts.
Also, the so-called "water-proof" compression connectors are often
not. The connection must be waterproofed effectively.? Also,
condensation from humidity can be a big problem. Here is northeast
Ohio, the environment is humid for the majority of the year. I have
poured water out of a 75 ohm preamp that was sheltered in a good
enclosure!
These complex phasing arrays are by no means plug and play. Each
installation will be unique depending on layout and surrounding
objects. There are three tools necessary to get them and keep them
working:? 1.) a good portable signal source to feed the antenna
preamps (I use an Elecraft XG-3 with a home brew impedance transformer
at the input);? 2.) a portable transceiver to measure signal out of
the system at various points (My KX3 does a great job); and an
accurate antenna analyzer to measure impedances and to measure
feedlines and phasing lines for the proper electrical lengths. N6RK is
right. There can be considerable difference in RG6 impedance so you
need to check it out.?
73 Dennis W0JXMilan, OH
_________________
Searchable Archives: http://www.contesting.com/_topband [1] - Topband
Reflector
------------------------------
Message: 3
Date: Mon, 3 Apr 2023 10:20:26 -0700
From: Tree
To: Frank W3LPL
Cc: topband
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset="UTF-8"
I guess most people have some kind of small antenna analyzer that has
a TDR
kind of function.
I have not warmed up to them yet as the results I see seem to be "all
over
the place". Maybe I just don't know how to use them yet.
My goto TDR is homebrew - using an analog scope.
Here is one design pretty similar to what I am using:
A very simple TDR from W2AEW ? PierpaLab.com
[2] I put a
switch on it to slow down the rep rate as an option since some of my
"stuff" is pretty long.
It works wonderfully to check feedlines and beverages. I have one
beverage
that has transformers and feedlines on both ends and I can see the
difference between open/short/terminate on the "far end" (which is
physically in the shack).
73 Tree N6TR
On Mon, Apr 3, 2023 at 10:11?AM Frank W3LPL wrote:
> Another highly recommended tool is a Time Domain Reflectometer.
> Tt easily detects any abnormalities in my 8-circle and 4-square
> arrays and stacked HF Yagi arrays and switches.
>
> Other than my hand held antenna analyzer, my hand held TDR is my
> most often used and most valuable tool for proving that the
performance
> of my antennas and feedlines has not changed from prior
measurements
> and identifying and isolating faults before they cause partial or
> total failure. A TDR can detect, diagnose and locate feedline and
> antenna faults from the comfort of your ham shack.
>
> Affordable TDRs are often available on eBay. Some antenna
> analyzers have rudimentary TDR capabilities but I've never used
> an antenna analyzer with TDR capabilities comparable in
> performance to a TDR.
>
> Long before moisture causes coax failure, it causes the impedance
> of the coax to change, a potentially big problem in a phased array
> or stacked Yagis. A TDR easily detects and locates the problem
> before it causes a failure.
>
> An antenna analyzer can also detect that moisture has caused
> an impedance shift in coax cable. Place a dummy load (with the
> same impedance as the coax) at one end of the coax cable. Sweep
> the antenna analyzer frequency. As you do a frequency sweep the
> VSWR and impedance should not change. If it does, moisture is
> probably eating away inside your coax.
>
> 73
> Frank
> W3LPL
>
>
>
>
>
> ----- Original Message -----
> From: "Dennis W0JX via Topband"
> To: "topband"
> Sent: Monday, April 3, 2023 4:42:37 PM
> Subject: Re: Topband: High Impedance RX Antennas
>
> There is an old saying "The enemy of good is perfect." You will be
driven
> crazy by chasing down every slight variance from the ideal. That
being
> said, it is important to check out the obvious areas where flaws
can create
> big problems. Indeed, the feedline coax, typically RG6 CATV line,
is a
> major contributor to array performance problems. The cheap, big box
cable
> is covered with PVC and that stuff hardens and tightens up over the
years.
> This allows water to enter the shield and the water easily migrates
for
> long distances, creating a high resistance. Spend the money upfront
and buy
> quality cable that is flooded.
> The idea of using cable that has a solid copper conductor has
merit. But
> even with that, a bare copper conductor will oxidize over time. I
find
> myself cleaning these conductors on an annual basis with the eraser
end of
> a pencil (recommended by Lee K7TJR).
> I have also had F connector failures on my combiner box and on a
common
> mode choke. Sometimes the imported female connector center contact
just
> fails for no reason. The alternative Amphenol connectors are very
expensive
> at about $8+ each but I am considering replacing the connectors
with these
> higher grade parts.
> Also, the so-called "water-proof" compression connectors are often
not.
> The connection must be waterproofed effectively. Also, condensation
from
> humidity can be a big problem. Here is northeast Ohio, the
environment is
> humid for the majority of the year. I have poured water out of a 75
ohm
> preamp that was sheltered in a good enclosure!
> These complex phasing arrays are by no means plug and play. Each
> installation will be unique depending on layout and surrounding
objects.
> There are three tools necessary to get them and keep them working:
1.) a
> good portable signal source to feed the antenna preamps (I use an
Elecraft
> XG-3 with a home brew impedance transformer at the input); 2.) a
portable
> transceiver to measure signal out of the system at various points
(My KX3
> does a great job); and an accurate antenna analyzer to measure
impedances
> and to measure feedlines and phasing lines for the proper
electrical
> lengths. N6RK is right. There can be considerable difference in RG6
> impedance so you need to check it out.
>
> 73 Dennis W0JXMilan, OH
> _________________
> Searchable Archives: http://www.contesting.com/_topband [3] -
Topband
> Reflector
> _________________
> Searchable Archives: http://www.contesting.com/_topband [4] -
Topband
> Reflector
>
------------------------------
Message: 4
Date: Mon, 3 Apr 2023 11:33:10 -0600
From: Don Moman VE6JY
To: "Topband at Contesting. Com"
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset="UTF-8"
A used Tek 1502 TDR is the "gold standard" to me anyway and they can
be
quite cheap at flea markets etc. They are "arm held" and self
contained
portable so ideal for up to 1000' runs and have enough resolution
that you
can "see" defects that you don't really need to worry about. The
advantage
over some of the VNWA's that have a TDR function, is that the 1502 is
real
time so intermittents can easily be spotted. And it measures
impedance so
you can easily see how long and what Z that unknown roll of flea
market
coax is!
I built the scope based TDR from the QST articles years ago, but that
version isn't even close to the 1502. I also have a Tek 1503 for
checking
longer runs of control cable etc.
73 Don
VE6JY
On Mon, Apr 3, 2023 at 11:21?AM Tree wrote:
> I guess most people have some kind of small antenna analyzer that
has a TDR
> kind of function.
>
> I have not warmed up to them yet as the results I see seem to be
"all over
> the place". Maybe I just don't know how to use them yet.
>
> My goto TDR is homebrew - using an analog scope.
>
> Here is one design pretty similar to what I am using:
>
> A very simple TDR from W2AEW ? PierpaLab.com
> [5] I put a
> switch on it to slow down the rep rate as an option since some of
my
> "stuff" is pretty long.
>
> It works wonderfully to check feedlines and beverages. I have one
beverage
> that has transformers and feedlines on both ends and I can see the
> difference between open/short/terminate on the "far end" (which is
> physically in the shack).
>
> 73 Tree N6TR
>
> On Mon, Apr 3, 2023 at 10:11?AM Frank W3LPL
> wrote:
>
> > Another highly recommended tool is a Time Domain Reflectometer.
> > Tt easily detects any abnormalities in my 8-circle and 4-square
> > arrays and stacked HF Yagi arrays and switches.
> >
> > Other than my hand held antenna analyzer, my hand held TDR is my
> > most often used and most valuable tool for proving that the
performance
> > of my antennas and feedlines has not changed from prior
measurements
> > and identifying and isolating faults before they cause partial or
> > total failure. A TDR can detect, diagnose and locate feedline and
> > antenna faults from the comfort of your ham shack.
> >
> > Affordable TDRs are often available on eBay. Some antenna
> > analyzers have rudimentary TDR capabilities but I've never used
> > an antenna analyzer with TDR capabilities comparable in
> > performance to a TDR.
> >
> > Long before moisture causes coax failure, it causes the impedance
> > of the coax to change, a potentially big problem in a phased
array
> > or stacked Yagis. A TDR easily detects and locates the problem
> > before it causes a failure.
> >
> > An antenna analyzer can also detect that moisture has caused
> > an impedance shift in coax cable. Place a dummy load (with the
> > same impedance as the coax) at one end of the coax cable. Sweep
> > the antenna analyzer frequency. As you do a frequency sweep the
> > VSWR and impedance should not change. If it does, moisture is
> > probably eating away inside your coax.
> >
> > 73
> > Frank
> > W3LPL
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Dennis W0JX via Topband"
> > To: "topband"
> > Sent: Monday, April 3, 2023 4:42:37 PM
> > Subject: Re: Topband: High Impedance RX Antennas
> >
> > There is an old saying "The enemy of good is perfect." You will
be
> driven
> > crazy by chasing down every slight variance from the ideal. That
being
> > said, it is important to check out the obvious areas where flaws
can
> create
> > big problems. Indeed, the feedline coax, typically RG6 CATV line,
is a
> > major contributor to array performance problems. The cheap, big
box
> cable
> > is covered with PVC and that stuff hardens and tightens up over
the
> years.
> > This allows water to enter the shield and the water easily
migrates for
> > long distances, creating a high resistance. Spend the money
upfront and
> buy
> > quality cable that is flooded.
> > The idea of using cable that has a solid copper conductor has
merit. But
> > even with that, a bare copper conductor will oxidize over time. I
find
> > myself cleaning these conductors on an annual basis with the
eraser end
> of
> > a pencil (recommended by Lee K7TJR).
> > I have also had F connector failures on my combiner box and on a
common
> > mode choke. Sometimes the imported female connector center
contact just
> > fails for no reason. The alternative Amphenol connectors are very
> expensive
> > at about $8+ each but I am considering replacing the connectors
with
> these
> > higher grade parts.
> > Also, the so-called "water-proof" compression connectors are
often not.
> > The connection must be waterproofed effectively. Also,
condensation from
> > humidity can be a big problem. Here is northeast Ohio, the
environment is
> > humid for the majority of the year. I have poured water out of a
75 ohm
> > preamp that was sheltered in a good enclosure!
> > These complex phasing arrays are by no means plug and play. Each
> > installation will be unique depending on layout and surrounding
objects.
> > There are three tools necessary to get them and keep them
working: 1.) a
> > good portable signal source to feed the antenna preamps (I use an
> Elecraft
> > XG-3 with a home brew impedance transformer at the input); 2.) a
> portable
> > transceiver to measure signal out of the system at various points
(My KX3
> > does a great job); and an accurate antenna analyzer to measure
impedances
> > and to measure feedlines and phasing lines for the proper
electrical
> > lengths. N6RK is right. There can be considerable difference in
RG6
> > impedance so you need to check it out.
> >
> > 73 Dennis W0JXMilan, OH
> > _________________
> > Searchable Archives: http://www.contesting.com/_topband [6] -
Topband
> > Reflector
> > _________________
> > Searchable Archives: http://www.contesting.com/_topband [7] -
Topband
> > Reflector
> >
> _________________
> Searchable Archives: http://www.contesting.com/_topband [8] -
Topband
> Reflector
>
------------------------------
Message: 5
Date: Mon, 3 Apr 2023 14:09:32 -0400
From: "John Kaufmann"
To: "'Topband at Contesting. Com'"
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset="utf-8"
Another tool I've found indispensable for setting up and
troubleshooting phased vertical RX arrays is a two-port VNA. I use an
Array Solutions VNA-2180 (now discontinued) for critical measurements.
I also have a NanoVNA H4 (https://nanovna.com/) [9] which is a very
"affordable" VNA that can be used as a portable, handheld, standalone
instrument and that you can take out in the field. In most cases, the
NanoVNA H4 is more than good enough.
There is a learning curve to using a VNA. However, once you learn it,
you'll be able to make very accurate measurements of delay line
lengths, preamplifier gain and phase, phase combiner gain and phase.
Most VNA's also have a TDR function, although it is usually based on
frequency domain measurements that are transformed to the time domain.
I'm running a homebrew RX array and it would have been almost
impossible to get it running as well as it is now without a VNA.
73, John W1FV
------------------------------
Message: 6
Date: Mon, 3 Apr 2023 09:04:26 -1000
From: Dave Cuthbert
To: Frank W3LPL
Cc: topband , PVRC
Subject: Re: Topband: [PVRC] 2-element receiving arrays
Message-ID:
Content-Type: text/plain; charset="UTF-8"
It seems that padding the element capacitance as needed for equal
capacitance would help.
Dave KH6AQ
On Thu, Mar 30, 2023 at 4:48?PM Frank W3LPL wrote:
> Hi Dave,
>
> Anyone who has experimented with a high impedance antenna such
> as an end fed half wave has experienced the extreme environmental
> influence on the feedpoint impedance of a high impedance feed.
>
> The required spacing to trees and buildings is very difficult to
predict
> with any confidence. The impedance of a high impedance element
> -- and hence the amount of voltag if feeds into the preamp --
> is heavily influenced by its immediate environment.
>
> If all of the high impedance verticals in an array do not produce
the
> same voltages from the signals received by the array, the pattern
> of the array and especially its nulls are significantly degraded.
>
> 73
> Frank
> W3LPL
>
>
>
>
>
>
>
> From: "K3ZJ David Siddall"
> To: "Frank W3LPL"
> Cc: "topband" , "PVRC" ,
> "Pete N4ZR N4ZR"
> Sent: Friday, March 31, 2023 12:34:28 AM
> Subject: Re: [PVRC] Topband: 2-element receiving arrays
>
> Frank,
> " wrt to-negative effects of nearby trees and buildings." for high
> impedance verticals:
>
> Is there any data measuring how much loss if placed in the woods?
Minimum
> distance from a tree to minimize the loss? Are their other effects
too,
> such as less directionality?
>
> 73, Dave K3ZJ
>
>
>
> On Thu, Mar 30, 2023 at 1:38 PM Frank W3LPL < [ mailto:
> donovanf at starpower.net | donovanf at starpower.net ] > wrote:
>
>
> Hi Pete,
>
> For a monoband receiving array, you might consider using low
impedance
> resonant verticals rather than high impedance verticals.
>
> The primary advantages of high impedance verticals are
> - very short verticals (but taller verticals produce stronger
signals)
> - multi-band operation
> - no radials
>
> The primary disadvantages are
> - reliability issues with outdoor electronics
> - lightning susceptibility of outdoor electronics
> - higher cost
> - much lower signal levels
> - extreme care required to suppress common mode signals (buried
feedlines
> are highly recommended)
> - negative effects of nearby trees and buildings.
>
> The primary advantages of low impedance verticals are
> - much stronger signal levels
> - much less criticality of common mode signal suppression,
> - much lower cost
> - much higher reliability
> - immunity to lightning damage
> - much less affected by nearby trees and buildings
>
> The primary disadvantages are
> - taller verticals (typically about 24 feet)
> - radials (they can be very short if many radials are used)
> - mono band operation (switchable matching networks can be used for
> multi-band operation).
>
> I highly recommend the DX Engineering Receiving Antenna Phasing
System.
> Its expensive but well worth the investment especially for a small
array.
>
> [ https://www.dxengineering.com/parts/dxe-ncc-2 [10] |
> https://www.dxengineering.com/parts/dxe-ncc-2 [11] ]
>
> If you have 120 feet for a three element array, the YCCC array is a
great
> choice
> It can use high impedance or low impedance verticals
> Unfortunately its no longer available from DX Engineering
> The nine element YCCC array uses only three active elements at any
time,
> so its really a three element array switchable in many directions.
>
> [
>
https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w
/> > |
>
https://static.dxengineering.com/global/images/instructions/dxe-yccc-switch.pdf?_gl=1*1cv0fc9*_ga*MjEyMDA1Nzc3MS4xNjUyMzAyMjc0*_ga_NZB590FMHY*MTY4MDE5NTk1OC40My4xLjE2ODAxOTYwNTYuNTAuMC4w
/> > ]
>
> [ https://www.youtube.com/watch?v=dl-crM5Kb6A [12] |
> https://www.youtube.com/watch?v=dl-crM5Kb6A [13] ]
>
> [ https://www.youtube.com/watch?v=lVW1CmrzP7c [14] |
> https://www.youtube.com/watch?v=lVW1CmrzP7c [15] ]
>
> A two element array occupies only 60 feet or even a little less.
>
> 73
> Frank
> W3LPL
>
>
> ----- Original Message -----
> From: "Pete N4ZR N4ZR" < [ mailto:pete.n4zr at gmail.com |
> pete.n4zr at gmail.com ] >
> To: "topband" < [ mailto:Topband at contesting.com |
Topband at contesting.com
> ] >
> Sent: Thursday, March 30, 2023 12:54:30 PM
> Subject: Topband: 2-element receiving arrays
>
> Thinking ahead to next winter on 160, I'm interested in replacing
my
> K9AY Loop with a 2-vertical phased array. I'd like to homebrew the
> antennas and just buy or build the remote control unit for the
shack.
> I'm looking for sources of components (antenna-located preamps and
an
> in-shack controller), and would prefer not to completely homebrew
them,
> but the prices at the usual suspects are awfully high. Any ideas?
>
> I have pretty reasonably-priced access to 25 and 31-foot fiberglass
> poles (used for wind-socks by model airplane enthusiasts). I'm
thinking
> that one relatively low-cost approach might be to attach, say, #14
wire
> to the poles, with preamps at the base, but wonder if there is a
> downside to using such small-diameter antenna elements rather than
1 or
> 1.5 inch tubing? Alternatively, are clones of the DX Engineering 8'
> short verticals with preamps a good alternative?
>
> --
> 73, Pete N4ZR
> _________________
> Searchable Archives: [ http://www.contesting.com/_topband [16] |
> http://www.contesting.com/_topband [17] ] - Topband Reflector
> ______________________________________________________________
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Topband
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------------------------------
Message: 7
Date: Mon, 3 Apr 2023 12:18:02 -0700
From: Jim Brown
To: topband at contesting.com
Subject: Re: Topband: High Impedance RX Antennas
Message-ID:
Content-Type: text/plain; charset=UTF-8; format=flowed
On 4/3/2023 10:20 AM, Tree wrote:
> I guess most people have some kind of small antenna analyzer that
has a TDR
> kind of function.
In my professional life in pro audio, I started doing Time Domain
Spectrometry in 1982, so I have a pretty good handle on how it works.
There is a mathematical relationship between the frequency response
of a
system and its time response -- one is the inverse of the other. The
Fourier Transform of the time response yields the frequency response,
and the Inverse Fourier of the frequency response yields the time
response. Modern antenna analyzers produce a swept frequency
response,
and associated software running on the computer does the Inverse
Fourier
Transform of a sweep to produce the TDR.
For more than 10 years, the best of the low cost Vector Network
Analyzers has been the VNWA3SE, built and sold as a finished and
tested
unit, by SDR Kits, run by hams in UK. The unit, its firmware, and
associated software, was designed by DG8SAQ, an EE prof. Support from
both DG8SAQ and SDR Kits is excellent -- both read and respond to
their
support email reflector. Current cost with shipping is about $560
(depending on currency).
https://www.sdr-kits.net/introducing-DG8SAQ-VNWA3
/>
Greatest precision (ability to see small things) is provided by a
sweep
over a very wide frequency range. I usually sweep from 50-500 MHz.
Once
the sweep is done, the TDR is simply a few more button pushes in the
menu system.
73, Jim K9YC
------------------------------
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End of Topband Digest, Vol 244, Issue 4
***************************************
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[2] https://pierpalab.com/2022/04/30/a-very-simple-tdr-from-w2aew/%3E
[3] http://www.contesting.com/_topband
[4] http://www.contesting.com/_topband
[5] https://pierpalab.com/2022/04/30/a-very-simple-tdr-from-w2aew/%3E
[6] http://www.contesting.com/_topband
[7] http://www.contesting.com/_topband
[8] http://www.contesting.com/_topband
[9] https://nanovna.com/)
[10] https://www.dxengineering.com/parts/dxe-ncc-2
[11] https://www.dxengineering.com/parts/dxe-ncc-2
[12] https://www.youtube.com/watch?v=dl-crM5Kb6A
[13] https://www.youtube.com/watch?v=dl-crM5Kb6A
[14] https://www.youtube.com/watch?v=lVW1CmrzP7c
[15] https://www.youtube.com/watch?v=lVW1CmrzP7c
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