Re: [Elecraft] OT: The day I found out I was going to be an engineer

[John Magliacane via Elecraft]

 On Friday, September 15, 2023 at 08:35:40 PM EDT, Wayne Burdick 
 wrote:

> I was 8 years old. My dad had bought me a Radio Shack Science Fair 8-Note 
> Electronic Organ kit for Christmas, along with a soldering iron.

Sounds like one of their P-Box kits. When I was around the same age, my Father 
bought the 3-transistor regenerative Short-Wave Radio Kit. A listing of the 
P-Box kits can be found here: http://my.core.com/~sparktron/pbox.html

My Father was a Fireman, so there was no way he would trust me with a soldering 
iron at such a young age. Instead, he ended up building the kit himself while I 
watched with great interest.

He wound several coils so the receiver could receive several ham bands as he 
was trying to spark an interest in Amateur Radio, but I don't ever recall 
hearing any hams with the receiver, just the typical short-wave broadcasts of 
the time.

Several years later, he ended up taking the receiver away from me because the 
radiated broadband noise interfered with his Swan 500CX. :-)

It didn't matter much to me anyway as I never heard much with it. But it was 
every educational in the sense that the frequency range of the receiver was 
dictated by the size of the coil wound by the builder. Eventually he gave me 
his old Hammarlund HQ-140-X, so I hardly ever missed that old Radio Shack regen.

Interestingly enough, there's a modernized version of the receiver that employs 
silicon transistors (2N3904 and 2N3906s) instead of the original germanium 
jobs. Details can be found here: 
http://www.netzener.net/images/swradio/swradio.pdf

And that old Hammarlund lives on to this day after I "solid-stated it" not long 
after becoming a ham 40 years ago.


73 de John, KD2BD
  
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Re: [Elecraft] K2: Filter Aliginment software for Apple MACs.

[John Magliacane via Elecraft]

 Francis,

I use Baudline under Linux for various audio spectrum analysis tasks. There's a 
Mac version as well:

https://baudline.com/what_is_baudline.html

https://baudline.com/download.html


73 de John, KD2BD
  
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Re: [Elecraft] Muting the K2

[John Magliacane via Elecraft]

 Ray,

For what it's worth, I've been running a homebrew solid-state QSK CW 
transmitter for the past 4 years. My T/R relay is an AXICOM V23105A5303A201. It 
is a dual SPDT relay where each SPDT section is tied in parallel for greater 
power handling capability. The receiver is connected to the antenna through the 
relay on receive, and is allowed to "float" as an open-circuit on transmit.

The relay is controlled through timing and logic circuitry so that it becomes 
energized before any RF is produced, and de-energized after the RF envelope has 
decayed to zero. While I own a K2/100, I have been using this transmitter with 
either a Drake 2C or R4C receiver until I homebrew my own.

I just ran an experiment where I terminated the RCVE port with a 50 ohm load 
and measured the RF voltage across the load with a scope. On 40 meters where my 
transmitter produces 64 watts, I measured about 0.8v p-p across the terminated 
RCVE port, or about 1.6 mW (2 dBm) of RF. That equates to 46 dB of isolation at 
7 MHz. This seems consistent with the isolation specs on the relay that can be 
found here: https://www.farnell.com/datasheets/1918250.pdf.

The Drake receivers handle this signal level with ease, but I haven't tried the 
K2.

Incidentally, Jim, W6PQL has additional information on using inexpensive relays 
in RF circuits at his website: 
https://www.w6pql.com/using_inexpensive_relays.htm


73 de John, KD2BD
  
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Re: [Elecraft] [OT] WWVB Time Transmissions

[John Magliacane via Elecraft]

 > Bill,
> WWVB added a new modulation format starting around 2012/13 that includes a 
> phase shift that some older clocks can
> no longer resolve.

Gary,

The 2012 addition of BPSK modulation doesn't affect WWVB-controlled clocks -- 
only older carrier phase tracking receivers that use WWVB as a frequency 
reference that were designed prior to the October 29, 2012 modulation format 
change.

NIST has several receivers scattered around the country that monitor WWVB 
signal levels, 24 hours a day. You can check the status any time by going here:

 https://tf.nist.gov/tf-cgi/wwvbmonitor_e.cgi

Occasionally, WWVB is taken off the air for brief periods of time. Information 
on outages can be found here:

 
https://www.nist.gov/pml/time-and-frequency-division/radio-stations/wwvb/wwvb-station-outages

NIST Special Publication 250-67 provides technical details regarding the 
transmitters, feedlines, antenna systems, and routine maintenance procedures 
employed at WWV, WWVB, and WWVH.


73 de John, KD2BD
  
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Re: [Elecraft] Antenna tuners

[John Magliacane via Elecraft]

 On Friday, July 17, 2020, 10:03:24 PM EDT, Fred Jensen  
wrote:

> No antenna has, at any time, anywhere in any of our lifetimes, been
> "tuned" by an "antenna tuner."

Unless the "tuner" is simply a broadband transformer, I might agree.

But if the "tuner" is an LC network, like an adjustable L network, T network, 
Pi network, or a linked-coupled network, then I strongly disagree.

A tuner is a 2-port network. A transmission line is also a 2-port network. Both 
networks obey reciprocity, meaning that what you do to one port of the network 
will have a direct influence on the opposite end.

That being said, if an antenna exhibits a complex impedance at our frequency of 
interest, and that behavior can be corrected (brought to resonance) by the 
application of a particular value of reactance at the antenna's feedpoint, then 
that application of reactance can, for reasons of convenience, be made at the 
"shack end" of the transmission line. As such, the "tuner" in the shack is 
really "tuning" the antenna!

There's no "magic" involved here -- just a simple understanding that things 
that are connected together actually behave like they're connected together. A 
transmission line doesn't isolate the shack from the antenna: It couples them 
together with the highest degree of efficiency we can muster/afford. Therefore, 
what happens at one end of a transmission line DIRECTLY affects the other, and 
vice versa.

And so, properly applying an adjustable LC impedance matching network in the 
shack CAN (and often does) modify the resonant frequency of an antenna.


73 de John, KD2BD
  
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Re: [Elecraft] Antenna tuners

[John Magliacane via Elecraft]

 On Friday, July 17, 2020, 7:10:32 PM CDT, Kurt Pawlikowski  
wrote: 
 
> Ken: In some respects, a "matching device" at the base of the antenna is a 
> tuner! {'-) It accomplishes the same function... {'-) k
> WB9FMC

On Friday, July 17, 2020, 08:21:54 PM EDT, Ken Roberson via Elecraft 
 wrote:

> Kurt,
> We are not tuning the antenna , we are matching the antenna to the coax at 
> the base of the antenna.
> 73 Ken K5DNL

Kurt's correct. A low-loss (non-resistive) matching network connected directly 
at the feedpoint of an antenna will modify its resonant frequency.

A matching network connected to the feedpoint of an antenna through 1 inch 
(25.4mm) of transmission line will also modify the resonant frequency of the 
antenna.

A matching network connected through 1 meter of transmission line will also 
modify the resonant frequency of the antenna.

A matching network connected through 10 meters of transmission line will also 
modify the resonant frequency of the antenna.

And so on, and so forth... all the way back to the shack! ;-)

Why? Because transmission lines obey reciprocity. As such they cannot (aside 
from the effects of losses) separate what's on their source end from what's on 
their load end. What you do to one end directly affects the other, and vice 
versa.

Show me a transmission line that disobeys this property, and I'll show you a 
line that is either opened or shorted.

So, yes, a non-resistive matching network in the shack will bring your antenna 
SYSTEM (antenna + transmission line) into resonance at your operating 
frequency. In the process, the resonant frequency of the antenna is modified, 
as well.


73 de John, KD2BD
  
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Re: [Elecraft] Matching resonant antennas

[John Magliacane via Elecraft]

 On 15/07/2020 20:30, Ken WA8JXM wrote:

> Conversely, a non-resonant antenna can have a 1:1 SWR.

On Thursday, July 16, 2020, 03:33:12 AM EDT, David Woolley 
 wrote:

> You can only have a 1:1 SWR at a single impedance. If the design
> impedance is purely resistive, that means you can only have 1:1 for a
> resistive and therefore on-resonance load (or one that can be treated as
> having no reactive behaviour at the frequencies of interest - e.g. an
> ideal dummy load).

I agree completely, but there's a "catch".

Traveling-wave antennas, such as Rhombics, or Beverages, or leaky transmission 
lines, are, technically, non-resonant. However, they can each present a 50 ohm 
feedpoint impedance that is purely resistive, and produce a 1:1 VSWR as a 
result. ;-)

So, whether an antenna is resonant or non-resonant isn't the issue. The issue 
is whether or not a load impedance contains a reactive component. If it DOES, 
then it can never produce a 1:1 VSWR.

 
73 de John, KD2BD
  
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Re: [Elecraft] Conditions, shmonditions: DXing anyway

[John Magliacane via Elecraft]

On Fri, 9/21/18, Drew AF2Z  wrote:

> I generally use 440 Hz for sidetone/pitch, thinking that it is a familiar 
> standard musical note and perhaps is more recognizable to the
> brain in some way.  I don't know if that has any validity or not...

I've been using a sidetone pitch of 800 Hz on my K2/100 for years, but more 
recently thought I might prefer something a bit lower.

Running alongside a Drake R4C receiver, I've been experimenting with a homebrew 
CW transmitter over the past month that includes a sidetone oscillator.  I 
adjusted the pitch of the sidetone for something that "sounded about right" to 
my ears and left it at that.

Last weekend I decided to measure the frequency of the sidetone and found it 
was within 1 Hz of 800!

I suppose I've been listening to CW at 800 Hz for so long, I just committed the 
pitch it to memory.  :-)


73 de John, KD2BD
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Re: [Elecraft] Magnetic Loop question

[John Magliacane via Elecraft]

On Thu, 10/20/16, Steven Dick  wrote:

> The vertical loop can be horizontally polarized by feeding it in the middle 
> of the top or bottom edges.   It can be vertically polarized by feeding it in
> the middle of the vertical edges.

That's true for a loop having a full-wave circumference, but "Magnetic Loops" 
have circumferences that are typically only a fraction of a wavelength, and as 
such operate under a much different mechanism.

A vertically oriented magnetic loop, regardless of where it is fed, will 
achieve the highest degree of coupling to a vertically polarized signal, and 
have a bi-directional (half-wave dipole-like) radiation pattern.

A horizontally oriented magnetic loop, regardless of where it is fed, will 
achieve the highest degree of coupling to a horizontally polarized signal, and 
have an omni-directional radiation pattern.

This is because a magnetic loop is most responsive to the magnetic component of 
the RF wave.

When we speak of RF polarization, we are speaking of the polarization of the 
electric field.  A vertically polarized signal will have a horizontally 
polarized magnetic field, and vice-versa.  It is the horizontally polarized 
magnetic field from a vertically polarized wave front that will cut through the 
center of a vertically oriented magnetic loop and induce a voltage across its 
terminals.


73, de John, KD2BD
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Re: [Elecraft] Elecraft's linux utilities - somewhat OT, or maybe not

[John Magliacane via Elecraft]

On Tue, 5/27/14, Bill W2BLC w2...@nycap.rr.com wrote:

 I am not trolling, I really would like an honest answer as
 to why Linux is chosen over Windows for similar operations.

Bill,

In a similar way, I'm often asked why I spend so much effort with radio 
equipment, antennas, sunspots, etc. in such a cellphone and Internet dominated 
world.

The reasons are many.  None are simple to explain.

I started dabbling with Linux 20 years ago because it gave me the opportunity 
to run the equivalent of Unix on low-cost, non-proprietary hardware (a PC) that 
I already had in my possession.  I had previous experience with Unix, 
recognized it as a very serious and powerful OS, and wanted to learn more about 
it.  At the same time, I saw Microsoft products as being very poor in quality 
and being targeted toward individuals who knew very little about computers and 
(even worse) didn't want to know anything about computers.  I wasn't one of 
those people.

Slackware was my Linux distribution of choice in 1994, and it still remains so 
today.  I find many of the flashy all singing / all dancing Linux 
distributions difficult to use when doing anything out of the ordinary because 
they often try to think for the user (in their effort to make things easy), 
and more often than not, get things wrong in the process.  To me, these 
distributions aim for a Microsoft-like audience (individuals who know very 
little about computers and want to stay that way).

Having computer experience that dates back to the late 1970s, maybe you find 
yourself in a similar situation for a similar set of reasons.

I also think that the growing do-it-yourself, build-your-own (Linux) 
mentality that Doug (K0DXV) pointed out is also what Elecraft is all about as 
well, so it should come as no surprise that many Linux fans are Elecraft fans, 
too.


73, de John, KD2BD

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Re: [Elecraft] linux K3 utility

[John Magliacane via Elecraft]

On Wed, 5/21/14, Doug Person via Elecraft elecraft@mailman.qth.net wrote:

 I opened a terminal in the directory and
 entered ./k3util and got no such file or directory from
 bash. Huh?  I can see it, the permissions are correct,
 it is executable...  What am I doing wrong?
 
 Doug -- K0DXV

Hi Doug.

You're not doing anything wrong.  It sounds like you downloaded a pre-compiled 
binary that was linked to a library that is not present on your machine.  
That's what the no such file or directory error is referring to.

To see a list of libraries to which your executable file has been linked, type:

ldd k3util

After that, you'll have to determine what libraries you have, which ones you 
need, etc.


73, de John, KD2BD

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Re: [Elecraft] K2 Finals - Chronic Blow-Outs

[John Magliacane]

Hi Ray.

One possibility might be improper assembly of the transceiver that is causing 
the transistors to not mate properly with the heatsink on the bottom chassis.

Been there... done that.  :-)

Here's the story behind repeated 2SC1969 failures in my K2 back in 2003, and 
the mechanics behind the cause:

http://mailman.qth.net/pipermail/elecraft/2003-September/023145.html

http://mailman.qth.net/pipermail/elecraft/2003-September/023307.html

There were never any over-current issues, and it took several transistor 
replacements before I realized the problem was due to the incorrect placement 
of the lock washers associated with the 2-D fasteners.

Good luck!


73, de John, KD2BD

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[Elecraft] K2: KSB2 T1/T2 Turns Ratio Question

[John Magliacane]

Hi Folks.

I've been perplexed for quite some time as to why RF transformers T1 and T2 
that sit at opposite ends of the crystal ladder filter on the KSB2 board have 
different turns ratios.

T1's turns ratio is 22:7. while T2's is 22:4.

The impedance of the crystal ladder network appears to be in the neighborhood 
of 1200 - 1500 ohms.  Since the KSB2 sits inside an IF having a 150 ohm 
impedance, T1's 22:7 turns ratio, which performs a 9.87:1 impedance 
transformation, makes perfect sense.

The Balanced Modulator feeds T2's primary with an impedance close to 1200 ohms, 
which also makes perfect sense.

However, T2's secondary, having only 4 turns, presents an output impedance 
significantly lower than the 150 ohm IF system it is feeding.

What's the deal?   :-)

And I ask this question as I troubleshoot a narrower than expected crystal 
filter response.  I'm curious whether the T2 impedance mismatch is intentional, 
or something else is going on that I'm not aware of.

Any relevant enlightenment on the subject would be appreciated.

Thanks.


73, de John, KD2BD
K2/100 #3563

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Re: [Elecraft] K2: KSB2 T1/T2 Turns Ratio Question

[John Magliacane]

--- On Mon, 4/25/11, Wayne Burdick n...@elecraft.com wrote:

 I started with textbook impedance ratios, then adjust the windings 1 turn at 
 a time to find
 the optimal combination of power transfer and passband flatness. This can 
 vary with crystal
 characteristics, circuit strays, etc.

Thanks, Wayne.

When I built my K2/100 back in 2003, I changed the coupling capacitors in the 
crystal ladder network according to KI6WX's 2.5 kHz bandwidth mod.  I ran a TX 
sweep, and found my 6 dB bandwidth was only around 2.1 kHz.  I never measured 
the bandwidth prior to this change, but I know the change made the rig sound 
wider, with less ripple in the passband.

So, I'm looking for reasons that might explain why the bandwidth is so narrow.  
According to what I've read, the crystals I received with the kit in mid-2003 
should have been matched well enough for the bandwidth mod to work.  This is 
what directed my attention elsewhere, such as the transformers surrounding the 
ladder.

However, I'm beginning to think the crystals I received were not matched well 
enough to provide much beyond a 2 kHz bandwidth.

If crystal matching is indeed the problem, are new crystal sets available to 
match the calibration number (3.7 in my case) from earlier KSB2s, or will all 
14 crystals need to be changed so all filters have well matched center 
frequencies?


73, de John, KD2BD
K2/100 #3563

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Re: [Elecraft] K2: KSB2 T1/T2 Turns Ratio Question

[John Magliacane]

Hi Don.

Thanks for the reply.

  John,
 
 I cannot answer your exact question (the impedance ratios), but I need to ask 
 a
 question about your narrower than expected filter response.

I plotted a sweep of my TX chain a number of years ago, the results of which 
can be seen here:

   http://www.qsl.net/kd2bd/sweep2.png

It's a linear plot, so the ripple and other imperfections really stand out.  It 
was taken by sweeping audio through the KSB2 well below the level of ALC action 
while measuring the corresponding audio level picked up by a nearby crystal 
controlled, direct conversion receiver having no filtering or AGC.

Looking at the red LSB curve, if we estimate the center of the passband to 
average around 70 in amplitude, -3dB would be around 50, and -6dB would be 
around 35.

From this, I estimate the -6 dB bandwidth to be around a 2.2 kHz.  And this is 
with the 2.5 kHz -3dB bandwidth (2.6 kHz -6 dB bandwidth) coupling capacitors 
in the ladder.

And, lastly (although less scientific), if I optimize my CAL FIL settings so 
that my transmitted audio has the identical quality on LSB that it has on USB 
(as observed on a wideband receiver), my BFO settings are only 2.3 kHz apart.  
This is 400 Hz less than the spacing suggested in the KSB2 instruction manual 
for a 2.2 kHz (-6 dB) bandwidth.


73, de John, KD2BD
K2/100 #3563

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Re: [Elecraft] PIC Programming Book

[John Magliacane]

--- On Fri, 2/11/11, Lee Buller k...@swbell.net wrote:

 My friend, Jeff, who is not ham (His wife is...go figure)
 is a computer Linux geek and is trying to figure out how
 to program PIC computers.  I told him the other day that
 some Hams use them all the time in projects.  Not me...but
 some hams do.
 
 He is having some issues with finding information about
 registers.  I wonder if the people on the list could point
 me to books, manuals, information concerning the programming
 of PIC devices?  
 
 
 Lee - K0WA
 

Lee,

I have assembled PIC code under Linux for several different Microchip 
microcontrollers using GPUTILS:

   http://gputils.sourceforge.net/

and have programmed them using Picprog:

  http://hyvatti.iki.fi/~jaakko/pic/picprog.html

Microchip's web site (http://www.microchip.com) provides datasheets, tutorials, 
and sample code for use by anyone interested in making use of their 
microcontrollers.  There are also on-line discussion groups (such as 
http://www.piclist.com) that provide VERY useful information.

I have also learned quite a bit by reading, Programming  Customizing PICmicro 
Microcontrollers, by Myke Predko.

(Incidentally, it was the construction of my K2/100 in 2003 that was the 
driving force behind my getting interested in integrating PICs in many of my 
electronics projects.)


73, de John, KD2BD

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We won't tell. Get more on shows you hate to love 
(and love to hate): Yahoo! TV's Guilty Pleasures list.
http://tv.yahoo.com/collections/265 
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[Elecraft] Re: Band condx Questions from a Liberal Arts Major

[John Magliacane]

--- On Thu, 11/13/08, Jim Brown [EMAIL PROTECTED] wrote:

 Yes, but not necessarily what you think. Most of the in and out
 fading we hear on HF is the result of multipath. That is, the signal
 travels over two paths that differ a bit in time, which puts them
 out of phase. When they out of phase by some odd multiple
 of 180 degrees, they cancel, and by an even multiple of 180
 degrees, they add.

Absolutely correct!

Being a on-air frequency measurement nut (originally started with my K2),
I recently started looking into the issue of fading, and the effects it has
on making accurate frequency measurements.

Here's a short video clip illustrating WWV's carrier phase plotted against a 
local
frequency standard as a Lissajous pattern as received over a 1622 mile path.

Everything you described can be seen through careful observation of this clip:

http://www.youtube.com/watch?v=nf9KWfS9QBs
 
 The DEPTH of fading (that is, the weak part of the fade) depends
 on perfect cancellation of the signal, which happens when the
 two arrivals are almost precisely equal in strength.

Sometimes the second path wins out after the fade, and the resultant signal
emerges 180 degrees out of phase with what it was before the fade.

Aside from multipath, much of the slow and shallow fading seen on low HF 
frequencies
during the day can be the result of variations in D-layer absorption.


73, de John, KD2BD

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Re: [Elecraft] LINUX PCs and ham SW?

[John Magliacane]

 Other than W1HKJ's programs, and jLog - a Java based cross
 platform logging program - I don't know of any Linux ham software
 that is being actively developed.

H

http://www.qsl.net/kd2bd/software.html

And that's just me.  :-)

 And precompiled Linux binaries (unlike Windows
 .EXEs) very often won't run on a different version than
 the one they were compiled on.

It's *ALWAYS* best to compile from source.  That way, the executable
that is produced is tailored specifically for your CPU and computing
platform for best performance.  (Sort of like having all your impedances
matched.)
 
 Three commands may work to compile the very simplest basic
 C programs, but for many others especially GUI programs you first
 need to download and install various development libraries, many
 of which may have dependencies on other software that also needs
 to be installed.

Good distributions (those with enough forethought built into them)
usually come with these pre-installed.  It is appalling that some of
the more popular distros appear to put more effort into ease of
use issues and eye candy than core substance.

I have been using Slackware since around 1994, and haven't had
the need nor desire to change.  Sure, it may take some thought, time,
and effort to finalize configurations, but that makes it no different than
spending the time to build an Elecraft rig over buying a ready-made
transceiver.  I doubt there is an Elecraft builder alive who doesn't fully
believe the small effort to build their kit wasn't worth the reward it
provided in the end.

And so what is true for hardware is also true for software, for very similar
reasons.
 
Don't give up so easily.  ;-)


73, de John, KD2BD

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Re: [Elecraft] dipole antenna efficiency

[John Magliacane]

 John Magliacane wrote:
 
  It's a traveling wave antenna where the helix is wound around a
  supporting vertical mast that serves as a reflector.

David Woolley [EMAIL PROTECTED] wrote:

 None of the references I found (including university course
 notes), when researching this at the weekend, described anything
 other than a dielectric core.  They did suggest a spectrum of
 behaviour from basically linear polarized, to circular polarized,
 depending on the pitch.

Johnson's Antenna Engineering Handbook (McGraw-Hill) among others
describes the antenna design to which I am referring.  A preview of
chapter 28 where the antenna is described is available at:

http://books.google.com/books?id=xTSNJhVlHGgCpg=PP1sig=qdNrli_UaJsiZB_gq3cRqvjy4DY#PPT961,M1

Dielectric Communications (formerly RCA) manufactures such an antenna
(model TCL) for the purpose I originally described.  Their older
print catalog describes the antenna in more detail than what is
available on the web:

http://www.dielectric.com/broadcast/images/tcl1.jpg
http://www.dielectric.com/broadcast/vhf.asp

Jampro does a better job of describing and illustrating the antenna
on-line.  In particular, they state:

The JTC Circularly Polarized Spiral Antenna consists of a supporting
pole around which are multiple stainless steel spirals wound at
specific pitch angles and spaced from the pipe by heavy-duty
fiberglass-reinforced low-loss insulators. The array acts as a
traveling wave antenna, with the main beam broadside to the support
pole and exceptionally low radiation along the axis of the pole. It
produces an omni-directional azimuth pattern with low VSWR.

Full description and photos are available here:

http://www.jampro.com/index.php?page=jtc-circularly-polarized-spiral-tv-antenna


73, de John, KD2BD


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Re: [Elecraft] dipole antenna efficiency

[John Magliacane]

 John Magliacane wrote:
 
  
  I believe the Normal Mode Helix, as is used in HI-VHF television
  broadcasting, is a travelling wave antenna, rather than a
  resonant standing wave antenna, such as a dipole.

David Woolley wrote:

 You are thinking of axial mode helices.  Normal mode helices are
 the most common antennas on VHF hand-helds, and are often called
 rubber ducks.

I suppose various antennas go by the same name, even though their
operation is considerably different.

I was referring to a Normal Mode Helix also known as a Side Fire
Helix.  It's described in the Antenna Engineering Handbook
(Johnson), and used in horizontally and circularly polarized
omni-directional applications (mostly VHF and UHF-TV broadcast). 
It's a traveling wave antenna where the helix is wound around a
supporting vertical mast that serves as a reflector.

Axial mode helices are a different beast.  They are typically used to
provide broadband, UNI-DIRECTIONAL, circular polarization (OSCAR
satellite communications).  Invented by John Kraus, W8JK.

I always considered a rubber duck to be nothing more than a
continuously loaded monopole, and is considerably different in
operation from the other two helical antennas described above.

  When Skin Effect losses become an issue in RF conductors and 
  inductors, Litz wire is typically used.  I see no reason why a 

 One has to ask why this isn't used in all the commercial
 miracle antennas.

Look at some of the older antennas used for FM broadcast, such as the
Collins or RCA ring dipole arrays.  These are physically short,
capacitively loaded, gamma matched dipoles.  Some implementations of
these antennas place a number of identical dipole rings in parallel
with one another to reduce ohmic losses and improve efficiency. 

These antennas may not be made from Litz wire, but the underlying
concept of distributing RF current among closely placed parallel
conductors in an effort reduce resistive losses is still the same.


73, de John, KD2BD


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RE: [Elecraft] dipole antenna efficiency

[John Magliacane]

Ron D'Eau Claire wrote:

 We simply do not have conductors that will handle RF with
 anything like the efficiency they will handle DC or low frequency
 AC. That's because all the RF current 'crowds' onto the very
 surface of a conductor.

When Skin Effect losses become an issue in RF conductors and
inductors, Litz wire is typically used.  I see no reason why a
similar approach cannot be used (one of using multiple conductors
tied in parallel with each insulated from one another).

An El Cheapo approach might be to use multi-conductor cable
instead of a single, fat conductor to minimize Skin Effect losses.

Cookie, K5EWJ wrote:

 The capacitive reactance will require 397 microhenrys
 to cancel out which in turn will require a coil 4
 inches in diameter and about 24 inches long with 160
 turns (about 168 feet of wire).  Then you would need
 an 8333/1 balun transformer with its associated wire
 resistance.

Capacitance hats can be used to reduce the amount of
inductive loading required to establish resonance.

I agree that the impedance transformations appear astronomical,
but if performed in manageable steps (instead of a single
transformation), efficiency might be improved, and the process
might not seem so formidable or lossy.

David Woolley wrote:

 For antennas in practical locations, at least one other thing
 will happen:

 d) The antenna will convert part of the AC power into (near field)
 electromagnetic energy which will induce currents in the ground,
 building structure, wiring, water and gas pipes, etc.  Much of that
 energy will be converted to heat after it has lost, although some
 will be re-radiated (I believe, in extreme cases, if the current
 is induced in something large enough and resonant, the re-radiator
 can become the actual antenna and the antenna act as a feed device,
 but, normally, for low, and indoor antennas, this is where most of
 the energy turns to heat).

I fully agree that the surrounding environment is part of the antenna
SYSTEM, and should be taken into consideration regardless of whether
the antenna is half-wave or an electrically shortened version of a
half-wave antenna.

 This reflection abstraction causes a lot of confusion.  It is
 possibly easier to see it as simply a bad match between the
 transmitter source impedance (which is usually rather different
 from the optimum load impedance) and the antenna impedance,
 causing most of the DC input to the transmitter to end up as
 heat in the output devices.

Provided measures to re-reflect the energy back to the antenna in
phase with the incident power aren't made.  (And the device that
does this very nicely is the antenna tuner.)

Actually, I mentioned reflected power to dispell the untrue but
widely held belief that reflected power cancels forward power
on a transmission line.  Forward and reflected power can peacefully
co-exist on a transmission line without interaction.  If this were
not true, repeater systems using duplexed antenna systems would
be impossible.

 As already pointed out, skin effect means that this is not true.
 People experimenting with small magnetic loops have to use large
 copper pipes to keep ohmic losses manageable.

The problem (in my mind) is that the copper pipe is really only a
single conductor, rather than the more efficient approach taken by
Litz wire where multiple conductors, each a skin depth in diameter,
are operated in parallel.

 For example, the KAT2 has a 10:1 SWR matching specification, but
 matching the antenna discussed here, at infinite height above the
 ground, needs a 250:1 range, or more.  They can also have power
 losses.

Agreed.  The impedance transformation has to (in my opinion) be
step-by-step process -- the same as a modern receiver design.
(In a receiver, we don't try to get all our gain and selectivity
in a single stage.  By the same token, we shouldn't try to make
a large impedance transformation in a single stage, either.)

(Just my opinion...)

  The penalties for using physically shortened antennas are:
 
  (a) Decreased operating bandwidth

 I'm not sure that is inevitably true.  My reference for normal mode
 helices included them in the section on broadband antennas.

I believe the Normal Mode Helix, as is used in HI-VHF television
broadcasting, is a travelling wave antenna, rather than a
resonant standing wave antenna, such as a dipole.

The bandwidth decreases in shortened resonant antennas as a
result of the antenna's increased Q.  The Q rises because the
RF energy must oscillate back and forth between feedpoint and
endpoint of the dipole many more times than it does in a
full-sized antenna before all the energy applied to the antenna
is finally radiated into space.

In travelling wave (non-resonant) antennas (rhombics, Beverages),
the RF energy travels down the length of the antenna just once.
Therefore, they must be very long in terms of wavelength to radiate
all the energy into space on the first shot.

Incidentally, I'm not advocating that everyone 

Re: [Elecraft] dipole antenna efficiency

[John Magliacane]

When it comes to antenna efficiency, it is important to understand
that when RF energy is applied to any antenna, three things will
invariably happen:

a) The antenna will convert a portion of the applied AC voltage
and current into electromagnetic energy and radiate it into space.

b) The antenna will convert a portion of the applied AC voltage
and current into heat energy as a result of resistive losses in the
antenna structure.

c) The antenna will reflect a portion of the applied AC voltage and
current back to the transmitter as a result of an impedance mismatch
between the antenna and that of the source.

Unless steel or nichrome wire is used, or electrically poor
connections exist in the antenna structure, losses due to (b)
will be low.

Effects of (c) can be reduced or eliminated by using intelligent,
low-loss impedance matching techniques and low-loss feedline.
(Technically, reflected power isn't a loss per se, since
energy isn't dissipated when a reflection occurs.)

That leaves us with (a), the desired outcome of applying RF energy to
an antenna.  Since losses due to (b) and (c) are typically low and/or
easily corrected, it is very difficult NOT to achieve high antenna
system efficiency.

Shortening the physical length of an antenna below that of a
half-wavelength DOES NOT reduce its efficiency provided the
necessary efforts to minimize resistive losses in the antenna
structure and the impedance matching networks are made.

That last statement is so important and so often misunderstood,
it bears repeating:

Shortening the physical length of an antenna below that of a
half-wavelength DOES NOT reduce its efficiency provided the
necessary efforts to minimize resistive losses in the antenna
structure and the impedance matching networks are made.

We could make an 80-meter dipole just one foot long and realize
high efficiency if the proper low-loss impedance matching techniques
are employed.

If we were to apply 100 watts to such an antenna, and we get zero
watts reflected back, and the antenna and matching networks remain
cool, then 100 watts of RF energy is being radiated from that one
foot dipole -- the same as if a full-sized dipole were used.

The penalties for using physically shortened antennas are:

(a) Decreased operating bandwidth
(b) Decreased directivity
(c) Somewhat difficult impedance matching

If we're wiling to adjust our impedance matching networks when we
QSY, then (a) isn't much of a problem since our signals are seldom
more than a few kHz wide, anyway.

Dipoles have 2.14 dB gain over isotropic radiators.  As we make
our dipole shorter and shorter (and keep resonating and impedance
matching it in the process), its directivity (b) approaches that
of an isotropic radiator.  If our radiating structure and impedance
matching networks are lossless, an extremely short dipole may be as
much as 2 dB weaker than the signal produced by a half-wave dipole
in the broadside direction.  That's less than half an S-unit!

So, the key to success lies in (c), the impedance matching network.
It needs to have extremely low loss, be capable of matching a very
wide range of impedances, and (unless you're rock-bound) be agile
so the antenna can be operated across a broad range of frequencies.
Ideally, it should be placed at the antenna feedpoint, itself.


73, de John, KD2BD


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Re: [Elecraft] KSB2 OP1 filter USB response...

[John Magliacane]

--- Steve Kallal [EMAIL PROTECTED] wrote:

 It has been a few weeks since I built the KSB2 option. There is one problem
 I haven't yet resolved. The response on the USB side of OP1 is not as broad
 as the LSB side, and has a narrower peak.

Hi Steve.

Assuming your KSB2 is working properly, what you are seeing may very well be a
familiar characteristic of the crystal ladder filter used in the rig.

I ran some sweeps of my K2/100 several years ago, the results of which clearly
illustrate this effect.  Response vs. frequency plots may be found here:

  http://www.qsl.net/kd2bd/ksb2.html

The response is slightly asymmetric, with the roll-off being noticeably sharper
on one side of the passband than the other.

This is normal.

The side with the sharper roll-off will (in my opinion) ring more than the
gentler side.  As such, audio products that hit the sharper edge may appear
to be over-emphasized, so it might be beneficial to tailor your microphone's
audio response and the BFO frequencies to avoid hitting this edge with too much
audio.

Also, be aware that due to the mixing scheme of the transceiver, the audio
characteristics you observed are not only a product of the sideband selected,
but also the frequency band you've on as well.


73, de John, KD2BD


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Re: [Elecraft] Carbon Composition Resistors - Aging

[John Magliacane]

--- Jack Smith [EMAIL PROTECTED] wrote:

 Unlike fine wine, carbon composition resistors do not get better with age.

Yea verily!

I have observed effect myself with quite a number of 1/4-watt 5% tolerance
resistors that have never been used, are probably at least 20 years old, and
have been stored at room temperature.

In particular, a collection of 75 ohm resistors read extremely high -- in some
cases nearly DOUBLE their rated value!

I have not seen this effect as much with carbon film resistors of similar
value, vintage, tolerance, and power rating.

I made this discovery almost by mistake about two years ago.  I had been using
the 75-ohm resistors as terminators in NTSC analog video circuits for quite a
number of years.  While these circuits worked fine when tested on the bench
using a video test pattern generator (that had been previously calibrated using
one of these problem resistors as a terminator), improper video levels were
experienced when these circuits were used outside the test environment.


73, de John, KD2BD


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Re: [Elecraft] K2 and SSB

[John Magliacane]

 I was just wondering how many here use SSB with their 15 watt K2?  Does it 
 meet your expectations?

Hi Gary.

I put my K2 on the air (SSB) and made a number of contacts on 20 and 80 meters
before even opening the KPA100 parts box.

If I didn't tell people I was running only 15 watts at the time, I don't think
many of them would have known.  :-)

There are just s many variables involved in propagation that under many
circumstances, a 10 dB signal deficit may not be as drastic as one might think.


73, de John, KD2BD


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Re: [Elecraft] OT: balun rating exceeded

[John Magliacane]

--- Jozef Hand-Boniakowski [EMAIL PROTECTED] wrote:

 A few years back I bought a Buxcom G5RV and running 600 watts into it, 
 the balun that it came with was toast.  I replaced it with 10 turns of 
 coax wrapped around a Folger's coffee can.

So, you replaced the balun you normally use with New Folger's Crystals.  :-)

Seriously though, I've given this situation a lot of thought, and I'm not
thoroughly convinced an unshielded choke located in the nearfield of a
radiating structure would necessarily attenuate currents flowing on the outside
of the transmission line's shield.

I think even a perfectly functioning, perfectly shielded balun *at the antenna
feedpoint* might be somewhat moot unless the dipole is perfectly straight, and
the feedline is run exactly perpendicular to the dipole (to equalize coupling
to either side of the antenna).

By the same token, I've often wondered just how balanced a balanced feedline
really is under similar circumstances.  Maybe twisting the line might help
improve transmission line balance.  Maybe using a tuner that can compensate for
any voltage/current imbalance might be advantageous, as well.  

There are many complicating factors when it comes to antenna installation and
operation.  Fortunately, few, if any, turn out to be of much significance in
the grand scheme of things...


73, de John, KD2BD


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Re: [Elecraft] K3 roofing filter group delay

[John Magliacane]

 Don't forget Bessel filters.  These are maximally flat for group delay, but 
 have a much slower rolloff.

John,

What penalty (if any) would occur in cascading identical Bessel filters to
improve roll-off and stop-band attenuation?

Would the overall response still be considered Bessel, or will a point be
reached where the response begins to take on Chebyshev characteristics?

Thanks.


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Re: [Elecraft] OT mechanical v crystal filters OT

[John Magliacane]

 Off Topic but with so much expertise flying around I thought I would ask how
 mechanical filters compare with crystal filters.  
 
 I think they were fairly low in frequency (455kHz?), so, not suitable in the
 present discussion,  but it would be good for our education at least.
 
 David
 G3UNA

Hi David.

Mechanical filters, which operate in an acoustical domain, may have somewhat
higher insertion loss and lower dynamic range than properly designed crystal
filters.

However, I've heard some glowing on-air comments regarding the performance of
the old Collins mechanical filters, especially with respect to CW reception.

Well-designed direct conversion receivers are often noted for their superior
audio quality compared to highly filtered superhets.

Recently, I've designed a highly filtered (100 Hz bandwidth) quadrature phasing
direct conversion receiver, and was somewhat amazed by the clarity of CW
reception.

From these observations I have concluded the following:

Narrow-band reception requires sharp selectivity (obviously).  The higher the
frequency at which the selectivity takes place, the higher the required 'Q'. 
The higher the 'Q', the greater the amount of ringing and group delay
distortion that will occur.  Ringing and group delay distortion cause listener
fatigue.

In a direct conversion receiver, a 100 Hz bandwidth can be obtained at 1000 Hz
with a 'Q' of only 10. (Very low ringing)

A 100 Hz bandwidth at an IF of 455 kHz, however, requires a 'Q' of 4550. (More
ringing)

A 100 Hz bandwidth at an IF of 5 MHz requires a 'Q' of 50,000.  (An RF echo
chamber!)

My K2/100 experiences have lead me to believe that these effects occur with HF
SSB crystal filters as well, but more so at the passband edges rather than in
the center, provided it is essentially flat.  The K2's filter shape is slightly
asymmetric, so the filter edge with the sharpest cut-off is the one where the
greatest ringing occurs.

In order to minimize the effects filter ringing can have on SSB audio quality,
I have found it advantageous to attenuate the audio frequencies that strike the
corners of the sideband filter (prior to the balanced modulator), especially
when the filter operates at HF (rather than lower) frequencies because the 'Q'
is so high at these points.

(This isn't so much of an issue in reception because SSB signals have already
been bandwidth limited in the other person's transmitter.)

Just some greatly over-simplified and otherwise totally random thoughts on the
subject...


73, de John, KD2BD


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RE: [Elecraft] OT mechanical v crystal filters OT

[John Magliacane]

Hi Brett.

 John, 
 Please describe the quadrature phasing part of your receiver.

In general terms, the design is very similar to quadrature phasing receivers
used for SSB operation, except that since the bandwidth in this case is very
narrow, the 90 degree audio phase shifting network becomes ridiculously simple
(a single all-pass filter).

The receiver uses a pair of switching mixers (I and Q), an L.O. network with 0
and 90 degree outputs, a 90 degree audio phase shifter in one of the audio
channels (I or Q), a summing network, and three stages of active audio
filtering/amplification overall.

The phasing circuitry is necessary to produce single-signal reception (no
annoying image response on the other side of zero beat).

Tuning is a bit critical as it is possible to tune across a CW signal in
between the dits and dahs, and not even know a signal was there.

 On weak signals, I often find narrower filter settings of the K2
 make the signal harder to copy.
 Part of that might be my bad hearing and the higher pitch
 sidetone I like...
 The noise and the signal seem to blend into one pitch...

I agree.  In narrow bandwidths, the noise-induced ringing in an HF crystal
filter can almost sound like some sort of narrow shift FSK!

  Mechanical filters, which operate in an acoustical domain, 
  may have somewhat
  higher insertion loss and lower dynamic range than properly 
  designed crystal
  filters.
 
 They operate at 455 KHz, I don't think even dogs can hear that high!

Your TV set uses a Surface Acoustical Wave (SAW) IF bandpass filter that
operates at 45 MHz, where the acoustic energy traverses along a lithium niobate
substrate.  The insertion loss is fairly high, but the group delay distortion
is significantly lower than a comparable filter using LC components.

 Was not the old heathkit hw7 a direct conversion receiver?
 I had a lot of fun with that rig...

I believe the HW-7 was direct conversion...


73, de John, KD2BD


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Re: [Elecraft] Frequency counters for Alignment

[John Magliacane]

--- Jack Smith [EMAIL PROTECTED] wrote:

 That was true at one time, but is it still the case? I recall reading 
 that with the switch to digital video distribution color burst is 
 locally generated and hence not tied to the NBS standards.
 
 
 Jack K8ZOA

NBS Special Publication 432 used to describe this method back in the late 70s,
early 80s, but as was pointed out, it is no longer valid.

Personally, I have a homebrew 10 digit frequency counter (99% complete)
combined with a homebrew frequency reference locked to WWVB (60 kHz) (also 99%
complete) which is used as a timebase for the counter.  I can measure WWV and
CHU's HF signals, and resolve the Doppler shift that occurs as the signals from
these stations propagate via the ionosphere.  :-)

I have discovered that AM radio stations that carry IBOC digital broadcasts
have generally VERY accurate and stable carrier oscillators.  Some are based on
Rubidium oscillators tied to GPS clocks!

If you use this method for testing / calibration, just make sure you're
receiving groundwave (not skywave) because of the Doppler effects earlier
described.


73, de John, KD2BD


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Re: [Elecraft] One-Way Propagation?

[John Magliacane]

In addition to the other issues mentioned on this subject, the Earth's magnetic
field causes bending, twisting, and rotation that may not necessarily obey the
law of reciprocity in the reverse direction.


73, de John, KD2BD


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Re: [Elecraft] XV144 paired with Uniden HR-2600?

[John Magliacane]

Hi Cathy.

I've used an HR-2600 with a Microwave Modules 2-meter transverter in the past
with very good results.  I'm sure it can be used with the Elecraft transverter
using an approach similar to the following:

Remove the top cover of the HR-2600.  Towards the rear of the unit you'll find
three prongs supporting a small double-sided PC board.  This board connects
+-Vcc to the transmitter's driver and final power amplifier transistors.

Pull the board out, and solder a jumper between the left-most and right-most
prongs down toward the base of each prong.  This will permanently connect +-Vcc
to the driver transistor with the board removed.

In this configuration, the driver transistor will receive operating power, but
the final amplifier will not.  The output of the transmitter will now be in the
tens of milliwatts region (a guess).

To bring the transmitter power back to 25-watts, simply re-insert the board
into the prongs.

Bob's your uncle.  :-)

Just be aware that in this configuration, the HR-2600 is operating without ALC,
so you may need to back off from the microphone a bit.  Gauge your speaking
volume by the action of the bar graphs on the front of the rig.  The AM mode
probably won't work (but who cares?).

I relied on my transverter's RF-actuated TX/RX switching, but it's probably
best to dig inside the HR-2600 and bring a hard keyed PTT line out to the
transverter.  Several SSB contacts I made commented that they thought I was
using VOX, when in reality, I wasn't.  Perhaps the TX/RX threshold in my
transverter was a bit high.

This approach to 2-meter SSB worked well for me.  I was even able to use the
HR-2600's scanning feature to listen for band openings and CQs.  If the rig
had extended coverage to 30 MHz, I would have made more use of it in the
2-meter satellite sub-band.


73, de John, KD2BD


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Re: [Elecraft] K2: power out issue on some (but not all) bands

[John Magliacane]

Hi Ron.

If you're seeing reduced output on 17-meters and higher frequencies, it might
be an indication that only one of the two final transistors (2SC-1969) is
functioning.


73, de John, KD2BD


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Re: [Elecraft] linux and elecraft

[John Magliacane]

--- ron [EMAIL PROTECTED] wrote:
 
 Hey! No fair! (smile)
 
 Hams use technical terms.
 Linux use unique jargon or talk related to their software, it is 
 NOT technical. Even windoze is in English.

CQ, 73, QRZ?, QSO, Pounding Brass, Silent Key, Rig, XYL, LID,
HI, etc., are all jargon, too.  :-)

As is:

73 FER NW OM CU DN THE LOG DE JOHN KD2BD AR


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Re: [Elecraft] WWV Clocks -- It's really WWVB

[John Magliacane]

Hi Craig.

 We have a total of 8 automatic WWV synched clocks of various types...

 And I live 30 miles from the WWV transmitter.

Incidentially, it is _WWVB_ on 60 kHz, not WWV or WWVH on HF that is used by
these radio controlled clocks for periodic time checks, usually once a day
during the early morning hours (local time).

Despite your short distance to WWVB, you still might be experiencing poor
reception due to local interference sources.  Computer monitors, switching
power supplies, AC operated motors, and thunderstorms tend to generate a
lot of 60 kHz noise.

All three NIST stations transmit DST, leap year, UT1, and leap second
information bits.

With regard to DST flags transmitted by WWVB, NIST Publication 432 states:

Daylight saving time (DST) and standard time (ST) information is
transmitted at seconds 57 and 58. When ST is in effect, bits 57 and 58
are set to 0. When DST is in effect, bits 57 and 58 are set to 1. On the
day of a change from ST to DST bit 57 changes from 0 to 1 at  UTC,
and bit 58 changes from 0 to 1 exactly 24 hours later. On the day of a
change from DST back to ST bit 57 changes from 1 to 0 at  UTC, and bit
58 changes from 1 to 0 exactly 24 hours later.

With this in mind, poor or inconsistant reception might explain some of the
effects you've recently seen.

I'm 1622 miles east of WWVB and own a WWVB-based frequency standard / UTC clock
of my own design.  Even at this distance, when proper receiving techniques are
used, reception of WWVB is generally excellent, day or night.


73, de John, KD2BD


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Re: [Elecraft] Re: WWV DST

[John Magliacane]

Hi Mark.

 Thanks for the reference. However, the idea that this system is
 'superior' would depend upon why one is looking for a time reference.
 If all you want is a relatively high accuracy clock the WWV signal is
 superior IMO. It certainly is easier to decode! As an added benefit it
 includes the DST bit -- you never know when the govt will decide to
 change the DST rules.

Very true, but compared against WWVB and GPS, WWV/WWVH/CHU reception achieves
the poorest accuracy as a time and frequency reference due to the inherent
variability of ionospheric propagation.

NIST claims WWV/WWVH time reception to be accurate to within 1 to 20 ms.
WWVB reception is accurate to within 0.1 to 15 ms.

NIST's Frequency Measurement and Analysis Service, which is GPS-based, is
accurate to within 20 nanoseconds.  This precision is due in part to the fact
that NIST itself monitors the GPS signals while FMAS measurements are made, and
so the readings taken are, in fact, traceable to NIST's atomic standards.

Obviously, this is well beyond the accuracy most hams need in their shacks, but
modern soundcard based weak signal and SSTV modes are demonstrating very
clearly the increasing importance of being able to send and receive highly
accurate, stable, and well timed signals.  I suspect that trend will continue.


73, de John, KD2BD


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RE: [Elecraft] K2 Audio issue

[John Magliacane]

--- Don Wilhelm [EMAIL PROTECTED] wrote:

 As stated many times by Wayne B., the K2 design criteria was for low
 receive current consumption and that is one reason that the K2 has
 limited audio power output.  The current consumed by a higher powered
 audio stage could likely take more current than the rest of the receiver.

For a linear, class AB audio amplifier, I would agree.  However, there are some
very efficient Class D audio amplifiers on the market now that deliver an
amazing amount of audio power from very tiny packages.

Check out:

 http://monolithicpower.com/prd_05_classd_amp.htm

They have a 20-watt amplifier in an 8-pin DIP package.  It's rated at 24 volts,
and can operate down to 9.5.  The quiescent current at 24 volts is a whopping
1.5 mA, and efficiency is 93% at 20-watts!  (I'd assume the power output at 12
volts into 4 ohms is 20/4, or 5 watts.)

The challenge, of course, will be in preventing the switching noise from the
amplifier from destroying the noise-floor of an already very quiet receiver.

As far as getting more volume from an 8-ohm speaker, there may be small 4-to-8
ohm matching transformers available that can do the trick.  An old audio output
transformer with 4 and 8-ohm taps on its secondary can be wired as an
autotransformer to achieve a similar effect.


73, de John, KD2BD


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Re: [Elecraft] Homebrew Autotuner

[John Magliacane]

--- Don [EMAIL PROTECTED] wrote:

 At the moment, though, I am having trouble coming up with a software
 algorithm that finds minimum swr and this message is a request for
 suggestions.
 
 Any ideas?

Hi Don.

Most tuners contain directional couplers to indicate VSWR, but they
are often sandwiched between the transmitter and the tuning network.
The tuning network is then adjusted for zero reflected power using
a trial-and-error approach.

If the directional coupler were instead placed between your tuning
network and the antenna jack (the OUTPUT of the tuner), you could
use the amplitude and phase information returned from the coupler
to determine the complex impedance of the load (antenna) you wish
to match to 50 ohms.

Next, you could calculate what conjugate impedance the tuner needs
to place in series with antenna jack to produce the 50 ohm resistive
output impedance you desire, and then select the appropriate L and C
values in your tuner network to produce that impedance.

Done!


73, de John, KD2BD


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Re: [Elecraft] K2 SSB Mic Input Frequency response?

[John Magliacane]

--- Francis Belliveau [EMAIL PROTECTED] wrote:

 I am now confused by the existence of two different mod's with the same
 goal.

There may be more than just two...

http://www.qsl.net/kd2bd/ksb2.html

It looks like many of us have been down the same road.


73, de John, KD2BD


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RE: [Elecraft] K2 SSB Mic Input Frequency response?

[John Magliacane]

Hi Ron.

 Are you suggesting that those low frequencies are somehow being distorted or
 causing other problems in the audio I.C. in the K2 before they get to the
 filter? 

I would say: YES.

Ideally, the audio frequency response prior to the compressor should
closely match the IF bandwidth of the crystal filter.   Here's why:

Excessive low-frequency response prior to the compressor forces the
compressor to react to audio energy that has no chance of ever making
it through the crystal filter.  If the audio response is too wide, then
the compressor will react to the extraneous audio energy, essentially
desensing the balanced modulator and the stages that follow.

I would hazard a guess that this desense might even produce a
perception of low or muffled audio in some cases when sufficient
gain actually exists.

Since we are working with such a small audio bandwidth, the tighter
the control of the audio response prior to the compressor, the less
variation there will be between different microphones.


73, de John, KD2BD


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[Elecraft] Re: Sad day (Learning CW)

[John Magliacane]

Hi Dan.

--- DAN ABBOTT [EMAIL PROTECTED] wrote:

 I have been reading the comments about the possibility of dropping the
 requirement for CW in order to advance your license. I have great respect for
 those who have passed the code test and one day I would like to be able to
 use CW, but it will take a converter and keyboard to accomplish the task. Let
 me explain.
 I built my K2/100 while trying to learn the code to achieve my General
 license [ it's been three months now] with absolutely no success, my K2 is
 now only a listening device. I have used Ham University and Your Introduction
 to Morse Code from ARRL with no success. If your familiar with the courses, I
 get to the letter L and when you add all the other letters to the sentence it
 sounds like garbage to me.

I know where you're coming from.

I had an *EXTREMELY* tough time learning CW.  I tried learning it for
years starting at an early age using training tapes that ran at 13 WPM,
and had only limited success.

The biggest blow to my confidence came when my grandmother came over to
pay a visit one day, and was able to copy the code on the tape better than
I was after only casually listening to about 10 minutes of the practice!

I never got over that...

I started up again years later, and once I began to re-memorize the tapes,
I started making my own -- at around 3 WPM!  I slowly worked my speed up
to 5 WPM, and then started listening to W1AW's code practice.  I continued
to build my speed through DAILY practice.  I even built a direct conversion
receiver for W1AW reception around a color-burst crystal!  I worked so hard
at learning CW, and put myself under so much pressure to learn this skill,
that sometimes I would wake up at night with my teeth clenched so tightly
I thought for sure they would all be shattered by the morning.

But things slowly started to improve over time...

I eventually earned an ARRL Certificate of Code Proficiency for 10 WPM
copy, and later earned endorsement stickers for 15 WPM and 25 WPM.
(Incidentially, I only knew about this program because it took the
place of W1AW's regular code practice one evening.)  I took my 13 WPM
exam after getting the 15 WPM sticker.

Once I got my license (an Advanced ticket), circumstances left me
little choice but to build my own transmitter to get on the air.
The fastest thing to build was a CW transmitter, and I built
several using tubes (which for me, was a first).  Once on the
air, I spent most of my time in the Novice portion of the 40-meter
band because it was the only crystal I had.

All in all, learning to copy CW by ear was probably the hardest
skill I ever had to master.

Constant practice, along with a dedicated committment to myself
that *NOTHING* was going to stand in my way of learning CW, is
the reason I eventually went on to become KD2BD.

Maybe the same approach will work for you, too.

I haven't been active on CW in probably 20 years, but the lessons
I learned in acquiring that skill will never be forgotten.  I simply
apply them to other things in life with equal success.

I never had an interest in a no-code license.  In fact, the mere
thought of such a thing only gave me MORE energy to break my mental
block and finally master the skill that for years was a formidable
barrier to my success.

Practice, practice, practice!  Identify the reasons you're having
difficuly, and then knock them out of the ballpark!  Don't allow
anything to stand in your way.


73, de John, KD2BD


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Re: [Elecraft] Non-resonant attic loop

[John Magliacane]

 I'm needing to install an antenna in my new home. An attic loop is a 
 necessity ... can't run an outside wire easily.
 
 I'm assuming that an 88-ft loop will be non-resonant in all bands 80-10, 
 and fed with ladder line to the tuner should work.
 
 Other suggestions?


Gene,

A small, closed loop operated below resonance will have a very
low feedpoint impedance.  While it will radiate virtually all the RF
it is fed, its low impedance might be tough to efficiently match to a
50-ohm unbalanced transceiver.

So, instead of making just a single turn loop, how about making a two
(or more) turn loop, instead?  This would bring the natural resonant
frequency of the antenna significantly below that of a single turn loop.

If planned out correctly, you might be able to find the ideal dimensions
of a multi-turn loop that will provide self-resonance on the low end of
80-meters.  Anything above that in frequency should be easy to match
as others have already mentioned.

Just a thought...

Good luck!


73, de John, KD2BD


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Re: [Elecraft] An idea for the K2

[John Magliacane]

 I would like to know more about using a switching mixer for the BM.
 If the circuitry does not get too complex or introduce problems it would
 be worth trying. Please let me have more information.
 
 73
 Stewart G3RXQ

Imagine that you apply audio to a transformer that has a center tapped
secondary winding.  (With respect to the center tap, the output of the
transformer will consist of two independent audio signals, equal in
amplitude, but 180 degrees out of phase with one another.)

Now imagine that you ground the center tap, and connect a SPDT switch to
the free ends of the secondary.  The center pole of the switch doesn't
connect to the transformer, but serves as the output of this circuit.

Finally, imagine that the switch is toggled back and forth at an RF
rate while audio is applied to the transformer.

The end result will be a double sideband suppressed carrier RF signal
on the output of the switch.

In real life, we use OP-AMPs to provide the two out-of-phase audio signals
instead of a transformer, and CMOS analog switches, such as a CD4066 or
CD4053 (or better) in place of the mechanical SPDT switch and apply RF
to the control pins.

The end result is the same.

I use this approach *A LOT* for doubly-balanced mixing, synchronous
detection, phase detection, and modulation through the MF spectrum with
excellent results.

A quick Google search didn't turn up many simple examples of this approach,
but Bat Detectors (ultrasonic downconverters used to chase bats), and
Cave Radios (LF SSB transceivers with magnetic loop antennas used for
underground explorers) that do appear on the net use them quite often.
I used a switching demodulator and modulator in my 1200 baud BPSK Pacsat
Modem (http://www.amsat.org/amsat/articles/kd2bd/Pacsat_Modem/).

More involved examples can be found in Software Defined Radio designs
utilizing Commutating Detectors (so-called Tayloe Detectors).

A high-quality DSB modulator is quite simple compared to these designs.


73, de John, KD2BD


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Re: [Elecraft] An idea for the K2

[John Magliacane]

--- [EMAIL PROTECTED] wrote:

 I use my K2 on CW and SSB. I was wondering how K2 Hams would feel about  
 different
 grades of SSB adapters.

I would sharpen up the skirts on the audio chain (300 - 2700 Hz) with
active filters prior to the compressor.  (There is no reason for any energy
outside this spectrum to be passed along (and influence the operation of)
the compressor and the balanced modulator, since the crystal filter is too
narrow to pass it, anyway.)

Add some gain (accomplished through the active filtering stated above), and
provide a mic gain control (on the board).

It might be nice to replace the NE602/NE612 with a switching-style
balanced modulator for the following reasons:

* The BFO (VXO) injection voltage into the NE612 varies with the BFO
setting and USB/LSB switching.  The NE612, being a linear mixer, is
sensitive to this.  It's DSB output voltage varies according to the BFO
injection voltage, as does it's carrier suppression.

* A well-designed switching mixer is inherently self-balanced (assuming
matched resistors, minimal stray capacitance, and low offset voltage
OP-AMPs are used), eliminating the need for the carrier balance control
and one less adjustment for builders.

* More dynamic range (limited only by the output swing of the audio feeding
the modulator and the supply voltage to the analog switches), leading to
even less SSB TX distortion (IMD) and carrier suppression than is
possible now.

Good luck with the project!


73, de John, KD2BD


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Re: [Elecraft] Atomic Clocks and Aluminum Siding

[John Magliacane]

--- Stephen W. Kercel [EMAIL PROTECTED] wrote:

 Dave:
 
  From the 1 callsign, I expect that you are located in New England. If so, 
 you're on the ragged edge of the normal coverage of WWVB. It is likely that 
 the location is giving you as much trouble as the metal siding.

WWVB is by no means a weak signal.  But like everything thing else in
radio, It's the signal-to-noise ratio, stupid!  :-)

Look for local noise sources.  Much like an AM radio, atomic clocks use a
ferrite loopstick antenna for reception.  The tiny receivers in them have a
sensitivity is on order of 0.5 uV.  A tuning fork crystal provides
selectivity on the order of 10 Hz.

A loopstick antenna responds primarily to the magnetic component of
electromagnetic waves.  Since magnetic fields follow an inverse cube
(rather than inverse square) law, if you've got an interference
problem with a magnetic probe antenna, the source is likey right under
your nose.

Keep your clock as far away from (and at right angles to) gadgets in your
home that might use switch-mode power supplies (EVEN if they are turned off!). 
Our Sylvania color TV set is a prime generator of LF hash at my QTH, even
when the TV is off.  It took me a year and a half to discover this -- by
accident!

Also, the 5th harmonic of any TV's horizontal oscillator is only a few
kHz from 60 kHz.  Computer monitors sometimes cause problems as well.
I've heard that some UPS units use a switched-mode power supply operating
at 60 kHz.  (Manufacturers have discovered the virues of RF, if only they
gave it the respect it deserves.)

Atomic clocks typically sync themselves periodically (typically during
the evening when signals are strongest, and noise levels subside).  They
free-run on a 32.768 kHz oscillator, just like any other quartz-based
clock.  Their speed is not under control of the precise 60 kHz carrier
to which they are tuned.  Only spot checks are made to correct for timing
errors.  In between, you're on your own.

Personally, I don't own an atomic clock...  My story's different, but
directly related to my K2/100.

I'm in the process of developing a WWVB-based frequency standard that was
inspired by building and calibrating my K2/100 in 2003.  When I tried to
beat a harmonic of the 4 MHz oscillator against WWV on 20 MHz for
calibration, and couldn't copy WWV on 20 MHz for many days (weeks?),
I knew I had to find a better approach.  Having a test signal of known
precision would have been a nice way to perform the frequency counter
calibration.

I've made quite a lot of progress with the project, and have even used it
along with my K2 in the past two ARRL Frequency Measurement Tests with
very good results.

My antenna is a 40-turn air-core loop, 4-meters in circumference (that's
over 600 feet of wire!).  I cheated and used 40 conductor ribbon cable to
build the loop.  This feeds an Analog Devices instrumentation amplifier (to
maintain electrical balance) that is remotely powered by the receiver (the
antenna and preamp are in the attic).  The rest is a secret (only kidding!),
but it involves balanced synchronous detection, zero IF (baseband) filtering,
and correlation decoding.

Incidentially, I cannot hear WWVB at all using an LF upconverter, a 75-meter
dipole, and my K2.  All I hear is noise.  Yet, I have SOLID copy, any day,
any time, on my specialized receiver, and I'm over 1600 miles from WWVB.

Kinda make you wonder what else is out there, doesn't it?

 If you cannot get it to come into sync within a week, then you probably do 
 need an outdoor antenna. I'm sure that many participants in this reflector 
 could come up with a practical way to build a 60 kHz external antenna and 
 hook it to your clock. If I were doing it, I would look for one of the 
 commercially made antennas that are designed for the time servers that some 
 computer networks use.

Another approach might be to build a resonant loop (it can be smaller
than the one I described), and place it in proximity, (magnetically coupled)
to your atomic clock.  This would be similar to the Select-A-Tenna
(or similar devices) used to improve AM radio reception in fringe areas.

In closing, don't expect miracles from these clocks.  They are simple
designs that perform best under high SNR conditions.  They appear to be
too easily fooled by noise.  They don't do WWVB justice.


73, de John, KD2BD


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Re: [Elecraft] K2: AGC versus RF Gain versus AF gain

[John Magliacane]

As others have pointed out, only a single I.F. amplifier chip is gain
controlled in the K2.  The RF gain, the gain of post mixer I.F. amplifier
transistor, and the gain of the active product detector are not controlled
through AGC, yet they all contribute to the receiver's total gain.

Since the I.F. amplifier chip has a gain range of about 50 db (min to
max) (if memory serves correctly), that's about all the AGC range you'll
have for the entire receiver as a whole.  The RF attenuator/bypass/RF
amplifier provide about 24 dB (-10 db to +14 db) of manual gain control.
The volume control provides the rest.  :-)

About 20 years ago I converted an old Hammarlund HQ-140-X receiver
to a solid state design.  The Hammarlund's AGC controlled the gain
of the RF amplifier and three I.F. amplifiers (all 6BA6 remote
cutoff pentodes).  I kept the same philosophy after converting
each of these stages to 40673 MOSFETs.

The input of each 455 kHz I.F. stage was (is) through a tap on each
of the I.F. interstage transformers.  This gain deprives each I.F.
amplifier a bit, and is possibly done for maintaining stability, rather
than for reasons of impedance matching.  However, since there's still
more gain than is needed for the receiver, and since ALL of the RF
and IF stages are AGCed, a tremendous amount of AGC range is
available.  (Significantly more than if only 2 I.F. stages were
used without the gain-depriving transformer taps.)

The result of having nearly all of the receiver's total gain under AGC
control is that the difference in volume when tuning between a strong
signal (such as an AM broadcast) and an empty band (10-meter band noise
at night) is almost negligible.

With a large amount of receiver gain under AGC control, the volume
control essentially becomes a set-and-forget adjustment.

Happy Holidays, everyone.


73, de John, KD2BD


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Re: [Elecraft] Circuit Simulation Software

[John Magliacane]

Hi Howard.

 I am looking for software (preferably Linux, open source) to model electronic
 circuitry.  My primary interest is educational.  I want to use the software
 to design and investigate circuits to better understand how they work.  I may
 do a little design, as well.  Does anyone have suggestions?

Yes.  How about ng-spice (Next Generation SPICE)?

   http://ngspice.sourceforge.net/

It's still a work-in-progress, but I've been able to get some
meaningful simulations out of it under Linux.

I have also found the following guides:

   http://www.ibiblio.org/obp/electricCircuits/Ref/REF_7.html

   http://newton.ex.ac.uk/teaching/CDHW/Electronics2/userguide/sec4.html

very useful in running SPICE and in creating SPICE circuit files.


73, de John, KD2BD


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Re: FW: [Elecraft] How to set up SSB

[John Magliacane]

Hi Dan.

 Another idea.
 
 Why not some sort of RF-probe circuit? It would look just like the RF probe
 in the book, but with different component values to get the time constant
 down. The RF probe in the book gives about a 100 Hz bandwidth which isn't
 enough (I'd want at least 5K for SSB audio testing).

This will only work for AM signals (full carrier, and at least one sideband),
not suppressed carrier SSB.  My guess is that even if you were to throw your
balanced modulator WAY out of balance, it still would provide poor and
confusing results due to the carrier attenuation provided by the crystal
(sideband) filter.

A simple, low gain, direct conversion receiver (oscillator, mixer, audio
amplifier) will provide the necessary carrier injection (BFO) for proper
audio demodulation.


73, de John, KD2BD


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[Elecraft] KSB2 filter, IF signal path impedances, T1/T2 turns ratio

[John Magliacane]

Hi Folks.

I have several questions regarding the impedances involved in the K2's
I.F., and their impact on the design of the KSB2's filter and matching
transformers.  I poked around the K2 mail archives and saw a similar
question posted some time ago
(http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-05/msg01686.html),
but found no definitive answer or information.


Several assumptions that I believe are true:

* The impedance of the K2's I.F. signal path is 150 ohms.  The input
  impedance of the MC1350 I.F. amplifier chip is around 2000 ohms.
  This is matched to 150 ohms through T7, a toroidal transformer
  with a 20:5 turns ratio (16:1 impedance transformation).

* The impedance of the crystal filter in the KSB2 is 1500 ohms.
  T1 on the KSB2 board transforms the 150 ohm I.F. impedance
  to 1500 ohms (22:7 turns ratio, 10:1 impedance ratio).  T1
  is terminated either by R11 (150 ohms) on the KSB2 board,
  or the post mixer I.F. amplifier/noise blanker (150 ohms),
  depending on whether the transceiver is transmitting or
  receiving.

* T2, on the OTHER side of the crystal filter, has a 22:4 turns
  ratio, yielding a 30:1 impedance ratio (a 50 ohm impedance,
  rather than 150).

* The KSB2's crystal filter is operated in opposite directions
  in transmit and receive.  On transmit, the input is on the side
  of T2, and on receive, the input is on the side of T1.

* On transmit, the balanced modulator provides a proper 1500 ohm
  source impedance for the crystal filter.  R11 provides the proper
  150 ohm termination after T1.

  --- HOWEVER ---

* On receive, the output of the KSB2's crystal filter is mismatched
  by a factor of 3 to 1 (T2's output is 50 ohms, and it is feeding
  a 150 ohm I.F. amplifier).

* The KI6WX +10db modifications appear to treat the output of T2
  as being 150 ohms (or at least something higher than 82 ohms,
  the value of the emitter follower's emitter resistor), rather
  than 50 ohms, yielding a significant impedance mismatch on
  transmit.


Impact:

* Many of the crystal filter response measurements, such as those
  conducted using programs such as Spectrogram and Baudline, have
  been performed with the K2 in RECEIVE mode only.  Since the filter
  appears to be terminated differently depending on whether the K2
  is in transmit or receive mode, the results may not tell the whole
  story.


Confession:

I built my K2 last year and performed the KI6WX KSB2 filter and
+10dB gain modifications.  The improvement in frequency response
on receive was substantial, but I have never been satisfied with
my on-air audio quality (despite reports to the contrary).

I ran sweeps of the TX chain and found my transmitted frequency
response to be around 2 kHz after performing the 2.5 kHz mod.
Results are posted at http://www.qsl.net/kd2bd/ksb2.html

I put the results of these tests out of my mind for the past
10 months.

Yesterday I checked the batch of 82 ohm resistors I used for the
+10dB gain modification and found they were all measuring between
120 to 140 ohms!  Reflected through T2, this would yield a filter
source impedance of about 6000 ohms, a significant mismatch for
a 1500 ohm filter.

The higher-than-normal source impedance might explain the
narrow filter bandwidth I am experiencing on transmit (but
not on receive).

Before I change the defective resistor, I would like to get a better
understanding of the true terminating impedance of the filter.  T2's
turns ratio might suggest that even an 82 ohm resistor is too high
for proper termination.  If the KSB2 is truly operating in a 150 ohm
I.F. signal path, why aren't T1 and T2 wound with the same turns ratio?


Possible solutions:

* Decrease the resistance of the 82 ohm resistor to provide a
  closer match to the 50 ohm impedance provided by T2.

* Decrease T2's turns ratio to that of T1 to bring the output
  impedance of the filter from 50 ohms to 150 ohms for a better
  match to both the I.F. amplifier on receive, and the KI6WX
  +10dB gain modification on transmit.


Suggestions?  Comments?


Thanks in advance.


73, de John, KD2BD
K2/100 #3563

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