[IW5EDI] A 50 Ohm Dummy Load

[IW5EDI via rec.radio.amateur.moderated Admin]

IW5EDI Simone - Ham-Radio

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A 50 Ohm Dummy Load

Posted: 30 Apr 2020 07:22 AM PDT
http://www.iw5edi.com/ham-radio/4284/a-50-ohm-dummy-load



This idea came about after listening to all you Amateurs tuning-up your
amplifiers while on-air.
It always happens right in the middle of receiving a good SSTV picture!








This may give you the idea of building your own (cheap) dummy load and do
your tuning through this.
You can subsitute the shown value components to handle your mega-watt
amplifiers.
For example, you can use twenty, 1K (1000-ohm), 3W or 5W resistors
connected in parrellel.

The components shown here are two 100-Ohm, 5W resistors connected in
parallel and submerged in a tin of oil.
This will more than handle the few Watts output from the transmitters that
QRPers prefer.








Start by drilling a hole hole in the lid of a 250ml paint tin to suit the
SO259 connector. Solder around it to prevent any leakage when the oil is
added. Next, a leg of each resistor should be soldered to the metal lid and
the opposite ends both/all soldered to a length of stout copper wire which
is taken to the center connector of the socket.

With a multimeter, measure across the SO259. There should be a reading of
50-Ohms and no open/short circuits.
If all is well, fill the tin to the brim with engine oil and attach the lid
firmly in place.
At this point youll probably notice that oil will splurge over the sides so
dont do this on the kitchen table!









If you dont fancy the mess of oil its also possible to fill the tin using
sand. This will also dissipate
any heat generated by the resistors. Ive not tried this method but theres
no reason why it shouldnt work




Now perhaps youll build one and do your tuning-up thru it especially you,
G1!!!
(We know where you live!)




source http://www.keirle.fsnet.co.uk

The post A 50 Ohm Dummy Load appeared first on IW5EDI Simone - Ham-Radio.


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Some Tips on Sound Card Interfacing to Your Rig

Posted: 30 Apr 2020 07:19 AM PDT
http://www.iw5edi.com/ham-radio/4280/some-tips-on-sound-card-interfacing-to-your-rig



Originally, I set out to simply to record and play back received audio in
cases where it was necessary to let other stations hear their own signal as
accurately as possible. I soon discovered that there is software out there
that also allows SSTV and RTTY via the sound card as well. Most likely
there are other programs for different modes and uses, but for now I only
will concern myself with the above three applications.




Here are some tips on hooking up to your rig along with some of the
problems I ran into and how they were solved. For this discussion, the
hardware and software line-up includes Yaesu FT-990 and Kenwood TS-820S
transceivers; a 486DX100 PC with a Creative Labs Sound Blaster 16 sound
card; Sound Blaster utilities (Creative Mixer, SoundoLE, etc.); W95SSTV
(Jim Barber, N7CXI, and Bill Montgomery, VE3EC); BTL (Blaster TeLetype, Rob
Glassey, G0VTQ); Microsoft Windows 95.







Transceiver Audio Interface




Both the FT-990 and the TS-820S have a pair of RCA phono type jacks on the
rear panel for interfacing with external equipment, mostly for phone-patch
units. Both rigs specify the impedance of both audio in and out at 600 W.
The factory settings for the 990 are at 100 mV rms on the AUDIO OUT jack,
and 2 mV rms for the PATCH IN jack. The 820S manual does not provide any
levels for the PATCH IN or PATCH OUT interfaces, but it does reference use
for SSTV and other types of modulators/demodulators. With this in mind, you
should be prepared to do some experimenting with level setting using
divider networks and/or audio transformers between the rig and PC sound
card. Read the manual for your particular rig to identify sources of audio
to the PC and the external input for audio from the PC. Note any given
specifications of typical levels, either in Vrms or Vpk-pk.



Sound Card Interface




Sound cards vary in available means to interface with external equipment.
The Sound Blaster 16 offers a microphone input and a line input for getting
audio into the card. On the output side, there is the standard speaker jack
as well as a line output jack. Other cards offer only a choice between
speaker output or line output from one jack, set by a jumper on the card.
So examine your sound card to determine what is available as this will
influence how you interface with the rig.



Some Key Notes




Sound cards are stereo devices. You will be interfacing with a mono device
(the rig), but you still need to use three-circuit stereo connectors at the
sound card (assuming that it uses the miniature 1/8 or smaller jacks). Do
not attempt to use a standard two-circuit plug in the three-circuit jack on
the sound card. The tip contact is usually longer than on a three circuit
plug and can wind up shorting the left and right inputs or left and right
speaker and/or line outputs together.




Shielded wire for the interconnect is a must-have itemnot only for hum and
noise at audio frequencies, but to minimize RF on transmit from getting
into the sound card and back into the rig and causing distortion.




Get familiar with the sound card software, particularly if it provides a
virtual mixer function. The Sound Blaster Creative Mixer provides a master
volume control for output (speaker and line), separate controls for setting
mike in and line in levels, and tone controls for bass and treble.




The remainder of this discussion refers to Figure 1, which shows the audio
interconnections used between the PC and both of the rigs in my shack. It
is meant as an example; your particular configuration mayand most likely
willvary, but you can get the general idea.



Audio to the Sound Card




I chose to use the microphone input at the time. This input is very
sensitive and easily can be overdriven. The 990 specifies 100 mV rms at the
AUDIO OUT jack. This is adjustable inside the 990, but it is not easily
done as the adjustment must be made by removing the control board, tweaking
a pot, putting it back in and testinga tedious cut and try situation.




I guessed that the mike in of the sound card was probably down in the 2 to
20 mV rms range. Thus, the presence of the resistive divider between the
990 AUDIO OUT jack and the sound card microphone input. I initially started
with a 10:1 divider after having tried a direct connection. With the direct
connection, moderate, distorted audio could be heard in the sound card
speakers, due to severe overloading of the input and cross-talk within the
card. The divider cured this.




If you use the line input on the sound card, which usually works with
higher levels, you may not need the divider, but be prepared to use one.
Shielding is important, however, in my case, I kept the leads of R1 and R2
extremely short as well as the junction of the shields and minimize the
exposed center conductor lengths. So basically it is free air construction.
I have not seen any indication of RF problems getting into the system, even
while running up to the legal limit on voice on all bands (something I dont
do as a rule but did for test purposes). If the kW wont bother it, the
basic 100-200 W should be fine.). If your rig does not offer an auxiliary
audio out connection, you will need to either go inside the rig and find a
take-off point, or simply tap across an external speaker. With this method,
it is essential that the external speaker lead be shielded. I would
recommend a Y connector at the back of the radio as opposed to soldering
leads across the speaker terminals.



Audio to the Rig




If your sound card has a LINE OUT jack, this is the ideal place to start.
If not, then the speaker output is the next choice. This will require
obtaining a stereo Y adapter. Be aware that I have observed an on-air test
with another ham using this last approach and two problems can be present.
First, the speaker leads must be shielded to help guard against RF and hum
on transmit. Second, most power amps in the sound card have a certain
amount of residual hiss, hum, and other noise present even with no audio
present at the input. While low enough in level to not be noticeable in the
speakers unless you stick your ear right up next to them, connecting
directly to a sensitive input on your rig may result in transmitting a very
annoying background noise.




Another problem, generic to either approach, is hum/noise on transmit due
to ground loops. Rob Glassey, G0VTQ, addresses this in his BTL program,
which is why an audio transformer is used in Figure 1where the shield of
the lead from the sound card is isolated from the shield carrying audio to
the rig. This might seem strange since the shield from the rig audio output
to the sound card is not isolated. But it works! Without this approach, I
had considerable hum/noise which even showed on the wattmeter and on the
monitor scope.




Getting audio into the rig is the next task. If you have an external audio
input port on the radio for a phone patch, or similar, this is a good
choice. Others may have to resort to using the normal mike input and doing
a mixing circuit, or simple switch approach to select between the mike and
the sound card. The PATCH IN jack on the FT-990 is rated at 600 W and 2 mV
rms typical sensitivity.




The trick I found is to create a match between the normal microphone gain
setting on the rig for normal transmit audio (using the ALC deflection as a
reference) and the audio from the sound card to produce the same indication
to avoid having to jockey the mike gain control on the rig between modes.




The transformer in Figure 1 (Adobe Portable Document Format (pdf) file) is
an old audio output transformer from a solid state radio that matches the
audio output transistor collector to a 8-16 W speaker. It is wired to step
down the level from the sound card to the rig. The series resistor provides
a degree of impedance matching on the rig side. Without it, there was a
noticeable change in normal mike drive on the rig between having the plug
from the transformer in or out. You can compensate for the sound card audio
drive with the master volume control for the sound card (in software).




The capacitors across the windings of the transformer are there to bypass
RF and should not degrade audio quality due to the impedances involved.
Keep the leads of the capacitors short!. The caps in my installation are
soldered directly across the transformer terminals (leads).




If you have to tap across the sound card speaker for one of the channels,
the transformer should most likely have a ratio of 1:1. If you can find an
older interstage audio transformer (not a speaker/output one), it should
minimize the loading on the speaker output being used. I understand that
Radio Shack still offers a 1:1 transformer, so this might be well worth
checking out. If not, a 8-16 W output transformer can be used only this
time with the speaker winding hooked to the sound card speaker and used as
a step up transformer. Again, do not connect the shields of the cables
between rig and transformer, and transformer to sound card speaker to avoid
ground loops. Use the .001 uF caps for RF bypass.



Testing And Adjusting




I chose to begin with only the link from the rig to the sound card hooked
up. Try to determine if the audio output using the patch out or audio out
jack on the rear of the rig vary with the front panel AF gain. The FT-990
audio jack is independent of the front panel control. If you are getting
the audio from the rig speaker, set the AF gain for a comfortable listening
level.




My RTTY program (BTL) has a bar type graph at the top showing the relative
audio level coming in. The author recommends not exceeding the halfway
point on peaks. It also has a control panel for adjusting the input level
for the mike input on the sound card. I tuned in a reasonably strong RTTY
signal with little QSB. Swapping between the BTL sound card control panel
and the program main screen, I tweaked the mike input level for a peak bar
graph reading slightly less than half scale. Copy was perfect.




I next ran my SSTV program (W95SSTV). This program does not have a separate
control panel for setting the sound card, but does have a level display.
The author recommends no more than half scale (like BTL). I was able to
copy several pictures quite nicely and the level seemed to be set OK. If
your programs do not have a control panel for setting levels, you will have
to use whatever comes with your sound card software. This can be a bit
tedious having to swap between programs but once set, you should not have
to do this too often.




Now for transmit. I connected the cable/transformer link between the sound
card and rig. Prior to this, I turned of the processor on the rig and set
the mike control for normal ALC speech readings. Unlike the receive side,
the mike gain on the FT-990 does adjust the drive from the patch in jack on
the rear panel. Running the RTTY program and using the control panel
function, I transmitted the basic mark-space tones (no text yet) and set
the sound card line output setting for half scale ALC. NOTE: As always, it
is preferred that you use a dummy load during testing so as not to tie up a
frequency.




I ran W95SSTV and found that I had to tweak the mike gain a bit to
compensate for a slight difference in audio drive level. If you see too
much audio to the rig, even at low settings of the sound card output level,
increase the value of R3 in the schematic. If going directly to the mike
input on the rig, you may need to replace R3 with a voltage divider similar
to the one on the receive side. Some cut-and-try may be needed to achieve a
reasonable balance.




Finally, check for residual hum on your transmit signal. There are a couple
of ways to do this. Start with the PC running and ready, but no programs
running. Key the rig and listen in a separate receiver, have a fellow ham
close by (ie, gets you regularly at 59+) to listen, or use the monitor
function in the rig if you have one. There should be no detectable hum or
noise. If there is, start by rechecking the shields on the transmit cable,
being sure to have good connections at the plugs, and that the two shields
at the transformer are not touching and truly isolated from each other.




I would also recommend plugging the PC and accessories into the same power
strips as the radio gear (if you have enough current capacity) as this will
bring the chassis ground prong of the PC power cord somewhat more common
with the chassis ground of the rig. Otherwise, if you can, try a heavy
ground strap between the PC chassis and rig. This may not always be simple
to do with todays PC cases.




If the noise sounds more like a harsh buzz, the monitor may be a candidate.
I run a NEC Multisync XV17+ (17 inch) about a foot from the rig and have
not experienced any problems. This monitor is low-emissions compliant.
However, my older 15-inch VGA monitor, which was not, raised havoc with the
rig, even on receive. Try changing the arrangement of the equipment to
place more distance between the rig and monitor if possible.




One final note. Set the bass and treble controls in the sound card control
panel for a flat response for starters. Depending on the audio transformer
used with regard to the amount of iron in the core, retransmit of voice may
require you to adjust the bass boost upward to compensate for the low
frequency rolloff of the transformer. For RTTY and SSTY, using a flat
response setting should be adequate since these modes generally do not
involve frequencies below 1KHz. If you play music with your sound card,
note the settings for RTTY and SSTV so you can return to them.



Closing Comments




I hope this information will help. None of the above information is a
guarantee that it will work in all situations using the method I use as is.
Rigs vary, PCs and sound cards vary, and programs vary. I present this
material as a guide or starting point.




Also remember that RTTY and SSTV transmissions are high duty cycle modes.
Check your rig for any limitations on transmit time (key down) or
recommendations to reduce the power output for these modes. Working
locally, I set the FT-990 for about 30 W out. For DXing, I sometimes use my
amplifier (when needed) with the rig drive set to generate about 300 W out
of the amplifier. This appears to be more than adequate for almost all
conditions, and both the rig and amp are loafing. In keeping with good
amateur practice, use only the power you need to establish and maintain
good contact.




I have made several fun contacts on RTTY with DX stations and received some
very nice pictures on SSTV. But I have not done much transmitting. I guess
a digital camera is next! Hope you have fun with these modes.




Article originally available at www.arrl.org/news/features/1999/0701/2
Copyright by WA1VOA

The post Some Tips on Sound Card Interfacing to Your Rig appeared first on
IW5EDI Simone - Ham-Radio.


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Simple double-quad Antenna

Posted: 30 Apr 2020 07:16 AM PDT
http://www.iw5edi.com/ham-radio/4275/simple-double-quad-antenna



A simple 2.4 GHz double QUAD Antenna





The post Simple double-quad Antenna appeared first on IW5EDI Simone -
Ham-Radio.


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Why Are Antennas Built to Look Like They Do?

Posted: 30 Apr 2020 06:59 AM PDT
http://www.iw5edi.com/ham-radio/4270/why-are-antennas-built-to-look-like-they-do



We come to recognize the proportionate shape and appearance of antennas. If
we see a half wavelength dipole we recognize it for the antenna it is. When
we see a Ground Plane antenna we know what it is. Its just the same as when
we see a Ford automobile next to a Volkswagen we know which is which. It is
possible though for Ford to build a car that looks like a Volkswagen but,
its not possible to build a dipole that looks like a Ground Plane, or a J
antenna that does not look like the letter J! Lets investigate this, and in
fact we can start with the J antenna as our object model.


J

Observe that the vertical portion of the letter J is about two times higher
than the portion that forms the crook of the J, or we could say that the
height of the J is three times the height of the crook. It is for this
reason that the J antenna got its name.

The crook portion of a J antenna forms a Linear Impedance Matching
Transformer or Q-Line transformer because of these two parallel conductors
that are 1/4 wavelength long. Above this Q-Line is the radiating portion or
radiating element that is 1/2 wavelength long.

At the bottom end of this quarter wavelength Q-Line which is electrically
shorted together, there is a dead short zero Ohm impedance. One quarter
wavelength above this dead short is an infinitely high impedance of
thousands of Ohms. This is how any Q-Line device such as a Bazooka Balun
works.

Now some who have read this article so far might be scratching their chins
about now thinking, he said the radiating element is 1/2 wavelength long.
Gee, a dipole is one half wavelength long! Thats right, a J antenna is
merely an end-fed dipole! Another name for an end-fed dipole is a Zepp,
because this form of dipole was first used on Zeppelins. So how is the more
common version of a dipole different?


In the J antenna we feed the dipole on its end at the high voltage point of
the antenna. If we feed it at the center at its high current point, we will
see a much lower impedance or alternating current (AC) resistance. In fact
the characteristic radiation resistance of a center fed dipole in free
space is 72 Ohms. Free space by the way means that the antenna is several
wavelengths above the ground, or any other conductive object. Usually free
space means at least 10 wavelengths but, for practical design
considerations 3 to 5 wavelengths is often times hard enough to achieve!

What happens if we feed a dipole not at the center, and not at its end but,
half way in between. This sort of dipole we call a Windom named after the
antennas originator. This type of dipole has a characteristic impedance or
radiation resistance of 600 Ohms. This feature allows this sort of dipole
to be operated on almost any frequency within several octaves of its design
frequency, and always present a relatively moderate impedance and
consequently a decent SWR.


Next lets take a look at Ground Plane antennas, afterall, arent they just
another variation on a dipole? Well, its certainly true that they are
current-fed at the center of one half wavelength. If you have ever seen a
Ground Plane fabricated on a chassis mount coax connector you can see how
this antenna works.

You start by cutting five quarter wavelength metal rods, I have always used
Brazing rod. If we were going to make such a Ground Plane for the 2 meter
wavelength band we would cut these rods to about 19.25 inches. If we start
by just soldering on two of them, one to the center connection, and one to
one of the flange holes, we have sort of a dipole. Actually this probably
looks closer to an Inverted V type dipole but, I think you get the picture!
So, now we have one of these 1/4 wave rods connected to the center
conductor of our coaxial transmission line, and one of them connected to
the shield. So, why should we solder on the other three, wont the antenna
work with just these two? It would work as far as the transmitter is
concerned. It would have a characteristic impedance pretty close to 50
Ohms, so the transmitter would be happy! The trouble is that without the
other radials to form a uniform counterpoise , the antenna is not the
omni-directional antenna we were seeking! If we left it looking like an
Inverted-V, it would have a figure-eight radiation pattern broad-side to
the two rods. If we provide three radials 120 degrees from one another, or
four radials 90 degrees from one another, the antenna will have an
omni-directional radiation pattern. By the way, the radials really should
be about 5% longer than the radiating element. Also, if the antenna has 3
radials, they will have to be bent down at a lower more acute angle to
achieve a 50 Ohm impedance match to the transmission line.


So, whats the bottom line to all this palaver? Simply this, all antennas,
any antenna can be analyzed as to its design by analyzing its current and
voltage distribution. The end or tip of the antenna is always going to
represent a high impedance and high voltage point. If we measure down 1/4
wavelength we will find a high current point and a relatively low
impedance. If we follow this process all the way back to the feed-point we
can determine all aspects of the antenna including the antennas aperture
size, and the aperture size will tell us the antennas approximate gain.
Every time you double the aperture size of an antenna you double its gain,
which means you pick up 3 decibels of gain.

Lets check this out by looking at one last J antenna which has come to be
called a Super J. A Super J starts with a normal looking J just like we see
so many of nowadays. At the tip top of this J a quarter wavelength phase
de-coupling stub is added, and then another half wavelength dipole is
placed on top of the phase decoupler. Guess what happens next, we gain 3
dBd, or 3 dBs above a dipole reference! In dBi this would be 5.2 dBs
compared to an Isotropic reference.


Terms

Q-Line, Bazooka Balun, or linear impedance matching transformer: All of
these are electrically speaking the same thing. A Bazooka Balun only
differs in that it is fabricated from two lengths of tubing, as well as a
central coaxial inner conductor. These are all one quarter wavelength long!

Radiating Element: This term is both hard to closely define, and in fact is
a bit of a misnomer. The vertical element in a Ground Plane is sometimes
called the radiator or radiating element but, it really radiates in
conjunction with other associated elements that form part of a half
wavelength.

End-fed, and center fed: These terms are closely associated with the terms,
Voltage Fed and Current Fed&quot.. At the end of a half wavelength there is
an infinitely high impedance and consequently an infinitely high voltage.
At the exact center of a half wavelength is an infinitely high current and
virtually by contrast, no voltage and a very low impedance.

Characteristic Impedance: All conductors or wires have both some amount of
inductance and some distributed capacitance, this in itself provides a
lumped constant derived impedance. In various configurations such as two
wires parallel to one another, a characteristic impedance will result.
Wires that are brought more closely together will have a lower impedance as
parallel capacitance rises, or if they are farther apart this impedance
will rise as capacitance is reduced.

Radiation resistance: All antennas have a characteristic radiation
resistance because of the comparative effects of their distributed
inductance and capacitance. This can also be expressed as a current to
voltage ratio. Whatever this ratio is, a characteristic impedance will
result. For a dipole this is 72 Ohms, for a 1/4 wave Ground Plane with
radials at 90 degrees to the radiating element this is about 34 Ohms, and
for a 5/8 wavelength Ground Plane its about 90 Ohms.

SWR: Standing Wave Ratio is the term given to the measurement of current or
voltage distribution as imposed within the antenna. It is usually measured
as a voltage and therefore the term often used is VSWR&quot.. If an antenna
has a radiation resistance of 72 Ohms and we feed it with 50 Ohm coaxial
cable, the SWR will be 1.44:1. If we fed a 90 Ohm antenna directly with 50
Ohm cable the SWR would be 1.8 to 1 (1.8:1 or 90/50 = 1.8).

Phase de-coupling: When ever the aperture size of an antenna is increased
we have to make provision for the additional antenna elements to work in
phase with the other elements. On vertical omni-directional antennas this
is done by phase de-coupling half wavelength radiators with quarter
wavelength phase de-couplers.

Gain: Antenna gain is often times a controversial subject. It really
shouldnt be, for the following reason. Every time an antennas aperture size
is doubled, its gain will double. If I properly stack one beam antenna of
equal size over its predecessor I will have doubled its aperture size. If I
ignore the losses imposed by the feed line and phasing network, I will have
added 3 dBs of signal gain. Dont forget though, theres no free lunch. If I
put a 10 dB gain antenna on a 100 foot tall tower and use poor or cheap
coax cable to feed it, it may well turn out that I have less signal gain
than I would have had by putting a unity gain J up at 30 feet with good
coax.




Article by Wa6BFH originally at /www.geocities.com/SiliconValley/2775/

The post Why Are Antennas Built to Look Like They Do? appeared first on
IW5EDI Simone - Ham-Radio.


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Low Noise Antenna Connection

Posted: 30 Apr 2020 06:58 AM PDT
http://www.iw5edi.com/ham-radio/4268/low-noise-antenna-connection



From: j...@space.mit.edu (John Doty)
Newsgroups: rec.radio.shortwave
Subject: Low Noise Antenna Connection
Date: 26 Nov 1993 16:55:24 GMT








It doesnt take very much wire to pick up an adequate signal for anything
but the crudest shortwave receiver. The difference between a mediocre
antenna system and a great antenna system isnt the antenna itself: its the
way you feed signals from the antenna to the receiver. The real trick with
a shortwave receiving antenna system is to keep your receiver from picking
up noise from all the electrical and electronic gadgets you and your
neighbors have.



The Problem:




Any unshielded conductor in your antenna/ground system is capable of
picking up noise: the antenna, the lead-in wire, the ground wire, etc. Even
the widely recommended cold water pipe ground can pick up noise if it runs
a significant distance before it goes underground




Symptoms of this problem include buzzing noises, especially at lower
frequencies, clicks as appliances are turned on or off, and whines from
motorized devices. Sometimes the problem can be reduced by running the
radio from batteries.



The Solution:




The solution is to keep the antenna as far as possible from houses, power
lines, and telephone lines, and to use a shielded (coaxial) transmission
line to connect it to the receiver. To get this to work well, two problems
must be avoided: noise currents on the shield must be kept away from the
antenna, and, if you want to listen to a wide range of frequencies, the
cable must be coupled to the antenna in a non-resonant way.




You can keep noise currents away from the antenna by giving them a path to
ground near the house, giving antenna currents a path to ground away from
the house, and burying the the coaxial cable from the house to the antenna.
Resonance can be avoided by coupling the antenna to the coaxial cable with
a transformer.



Construction:




My antenna and feed system are built with television antenna system
components and other common hardware. These parts are inexpensive and
easily obtainable in most places.




The transformer is built around a toroid extracted from a TV matching
transformer. If youre a pack rat like me, you have a few in your basement:
you typically get one with every TV or VCR (or you can buy one). Pop the
plastic case off and snip the wires from the toroid (it looks either like a
tiny donut, or a pair of tiny donuts stuck together). The transformer
windings should be made with thin wire: I use #32 magnet wire. The primary
is 30 turns while the secondary is 10 turns. For a one-hole toroid, count
each passage of the wire down through the hole as one turn. For a
two-holer, each turn is a passage of the wire down through the right hole
and up through the left.




Mount the transformer in an aluminum minibox with a chassis mount F
connector for the coax cable and a binding post or other insulated terminal
for the antenna. Ground one end of each winding to the aluminum box. Solder
the ungrounded end of the primary to the antenna terminal, and solder the
ungrounded end of the secondary to the center conductor of the coax
connector.




Drive a ground stake into the earth where you want the base of your antenna
to be (well away from the house). Mount the transformer box on the ground
stake: its case should make good contact with the metal stake. Drive
another ground stake into the earth near the place where you intend for the
cable to enter the house. Mount a TV antenna grounding block (just a piece
of metal with two F connectors on it) to the stake by the house. One easy
way to attach hardware to the ground stakes is to use hose clamps.




Take a piece of 75 ohm coaxial cable with two F connectors on it (I use
pre-made cable assemblies), connect one end to the transformer box, the
other end to the grounding block. Bury the rest of the cable. Finally,
attach a second piece of 75 ohm coax to the other connector on the
grounding block and run it into the house. Use waterproof tape to seal the
outdoor connector junctions.




Attach one end of your antenna to the antenna terminal on the transformer
box and hoist the other end up a tree or other support(s) (dont use the
house as a support: you want to keep the antenna away from the house). My
antenna is 16 meters of #18 insulated wire in an inverted L configuration
supported by two trees.




If your receiver has a coaxial input connector, you may need an adapter to
make the connection; in any case, the center wire of the coaxial cable
should attach to the antenna connection, and the outer shield should attach
to the ground connection.




Multiple grounds and transformer coupling of the antenna should reduce the
danger posed by lightning or other electrostatic discharge, but dont press
your luck: disconnect the coax from the receiver when youre not using it.



How it works, in more detail:




Coaxial cable carries waves in two modes: an outer or common mode, in which
the current flows on the shield and the return current flows through the
ground or other nearby conductors, and an inner or differential mode in
which the current flows on the inner conductor and the return current flows
on the shield. Theoretically, outside electromagnetic fields excite only
the common mode. A properly designed receiver is sensitive only to the
differential mode, so if household noise pickup is confined to the common
mode, the receiver wont respond to it.




The characteristic impedance of the differential mode is the number youll
see in the catalog or on the cable: 75 ohms for TV antenna coax. The
characteristic impedance of the common mode depends on the distance of the
line from the conductor or conductors carrying the return current: it
varies from tens of ohms for a cable on or under the ground to hundreds of
ohms for a cable separated from other conductors.




A wire antenna can be approximately characterized as a single wire
transmission line. A single wire line has only a common mode: for #18 wire
30 feet above ground, the characteristic impedance is about 620 ohms. For
heights above a few feet the characteristic impedance depends very little
on the height.




If the impedances of two directly coupled lines match, waves can move from
one line to the other without reflection. In case of a mismatch,
reflections will occur: the magnitude of the reflected wave increases as
the ratio of the impedances moves away from 1. A large reflection, of
course, implies a small transmission. Reflections can be avoided by
coupling through a transformer whose turns ratio is the square root of the
impedance ratio.




The basic difficulty with coupling a wire antenna to a coaxial line is that
the antennas characteristic impedance is a poor match to the differential
mode of the line. Furthermore, unless the line is very close to the ground,
the common mode of the line is a good match to the antenna. There is thus a
tendency for the line to pick up common mode noise and deliver it
efficiently to the antenna. The antenna can then deliver the noise back to
the lines differential mode.




Some antenna systems exploit the mismatch between the antennas
characteristic impedance and the lines characteristic impedance to resonate
the antenna. If the reflection at the antenna/line junction is in the
correct phase, the reflection will add to the signal current in the
antenna, boosting its efficiency. While this is desirable in many cases, it
is undesirable for a shortwave listening antenna. Most shortwave receivers
will overload on the signals presented by a resonant antenna, and resonance
enhances the signal over a narrow range of frequencies at the expense of
other frequencies. Its generally better to listen with an antenna system
that is moderately efficient over a wide frequency range.




In my antenna system, grounding the shield of the line at the ground stakes
short circuits the common mode. The stake at the base of the antenna gives
the antenna current a path to ground (while the transformer directs the
energy behind that current into the coax). Burying the cable prevents any
common mode pickup outside the house, and also attenuates any common mode
currents that escape the short circuits (soil is a very effective absorber
of RF energy at close range). Common mode waves excited on the antenna by
incoming signals pass, with little reflection, through the transformer into
differential mode waves in the coax.




A major source of power line buzz is common mode RF currents from the AC
line passed to the receiver through its AC power cord. These currents are
normally bypassed to chassis ground inside the receiver. They thus flow out
of the receiver via the ground terminal. With an unshielded antenna
feedline and a wire ground, the ground wire is a part of the antenna
system: these noise currents are thus picked up by the receiver. On the
other hand, with a well grounded coaxial feed these currents make common
mode waves on the coax that flow to ground without exciting the receiver.



Performance:




A few years ago, I put up a conventional random wire antenna without a
coaxial feed. I was disappointed that, while it increased signal levels
over the whip antenna of my Sony ICF-2001, it increased the noise level
almost as much. I then set up the antenna system described above; in my
small yard, the base of the antenna was only 12 meters from the house.
Nevertheless, the improvement was substantial: the noise level was greatly
reduced. This past year I moved to a place with a roomier yard; with the
base of the antenna now 28 meters away I can no longer identify any noise
from the house.




The total improvement over the whip is dramatic. A few nights ago, as a
test, I did a quick scan of the 60 meter band with the whip and with the
external antenna system: with the whip I could only hear one broadcaster,
unintelligibly faintly, plus a couple of utes and a noisy WWV signal. With
the external antenna system I could hear about ten Central/South American
domestic broadcast stations at listenable levels. WWV sounded like it was
next door.




I have also tried the antenna system with other receivers ranging from
1930s consoles to a Sony ICF-SW55. Ive seen basically similar results with
all.

The post Low Noise Antenna Connection appeared first on IW5EDI Simone -
Ham-Radio.


///////////////////////////////////////////
Antenna mounting height - the higher the better?

Posted: 30 Apr 2020 06:56 AM PDT
http://www.iw5edi.com/ham-radio/4265/antenna-mounting-height-the-higher-the-better



For someone surrounded by houses, power lines and trees, a 30m/98ft high
tower is desirable. A high tower is also desirable for someone situated on
perfectly reflecting ground, such as saltwater.








However, in most real world cases, the 30m/90ft height is less advantageous
than you might think.




Why is this the case?




The angle of radiation can be so low that most of the signal is eaten up by
ground loss. For the 21MHz, 24MHz and 28MHz bands, an antenna on a 30m/98ft
high tower has a radiation pattern of 5 degrees or less (depending on
ground conditions, the electrical height may be even higher and the angle
of radiation even lower). At these low radiation angles, the ground tends
to absorb a large portion of the signal.




To overcome this loss, it would be advantageous to be able to lower the
antenna to increase the angle of radiation at higher frequencies a
remote-controlled variable-height tower. Hams with these towers have
reported up to 12 dB DX-gain (e.g., on 21 MHz) by lowering the antenna from
its full 30m/98ft height to 20m/66ft height.




Note that the low radiation pattern of 4-5 element beams has about 14-15
dB/i ERP DX-gain.. This portion of your DX radiation can be partially or
totally lost, at maximum tower height.




The best (only) solution for maximum DX results at higher HF frequencies?
Provide a variable-height antenna tower.




Check for the most favorable radiation angle on medium-distance and long
distance DX (typically 2000-12,000 miles / 3000 20,000 km) with the help
of the chart above.




Example:




See Figure 1. At a Radiation Angle of 23 Degrees (See Fig. 1A) your
DX-chance at 7 MHz is 25%, while at 18 MHz it is 90%. At a Radiation Angle
of 7 Degrees (See Fig. 1B) your DX-chance at 10 MHz is 10%, while at 30 MHz
it is 50%.




While professional radio applications generally require long-time
connections, such as an S-4 signal for 5 hours, for amateur radio
applications an S9 +40 signal for just ten minutes can often be more
desirable.




Conclusion: Low radiation angles (typically 7-15 degrees) are effective for
big signals over long distances for a relatively short period of time,
which is usually adequate for DX purposes. However, if long-time QSOs are
your goal, higher radiation angles may be better.




Information from Neues von Rohde und Schwarz, Okt./Nov. 1973.

The post Antenna mounting height the higher the better? appeared first on
IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
70 cm Quagi Antenna

Posted: 30 Apr 2020 06:47 AM PDT
http://www.iw5edi.com/ham-radio/4259/70-cm-quagi-antenna



This was my first AO-10 antenna. As goofy as it looked, I managed a few
contacts with 10 Watts, including Brazil on SSB.










This is a pair of 8-element quagis, set up for RHCP. Construction is
simple, with no critical tuning elements. They are made from 1/2 PVC pipe
and # 10 wire (stripped from Romex) for directors and # 12 wire for loops.

 

The 4-element 2 m Yagi is made from 1/4 copper tubing and 3/4 PVC. It has a
50 Ohm dipole feed.

Theory:

The quagi antenna was designed by Wayne Overbeck, N6NB, amd is a high-gain
antenna combining the high-impedance (and easy matching) characteristics of
the quad antenna array and the high gain and ease-of-construction of the
classic Yagi-Uda parasitic beam array. See the original article, N6NBs
webpage, or the ARRL Antenna Book for complete description.

This design is optimized for 436.8 mHz with a 50 Ohm feed. It is a slight
departure from the design shown in the reference above. The graphic on the
right depicts the pattern in free space.









Construction:

The antenna is built using 1/2 PVC pipe (or 3/4 if prefered) and several
fittings. The driven element and the reflector are formed out of 12 gauge
wire (striped from house wiring, but insulation left on) and the directors
are made from 10 gauge wire. The following table is used for cutting the
wire: while the driven element can be trimmed to tune the antenna, the
directors should be cut accurately within 1/16 or performance will suffer.
If 3/16 aluminum rod is used for the directors, another 1/2 dB of gain is
predictedbut hardly worth the effort.

Using stainless steel bolts, nuts, and washers, directly connect the 50 Ohm
coax feed to the driven element. I use crimp-on ring lugs to make a neat
connection. Waterproof the connection with plenty of electrical tape or
Coax-Seal and paint all the PVC parts to prevent UV deteriation.




Performance:






A single one of these quagis will give excelent service for all the LEOs.
The free-space gain is calculated at an impressive 13.15 dBi with a 10.2 dB
F/B ratio. That is a lot of performance in an antenna you can hold in one
hand!

A pair of these will provide circular polarization (see the picture above)
and up to 3 dB more gain, depending on orientation. One also makes a fine
portable antenna for AO-27, easily bringing in that bird full-quieting at
the horizon. As the azimuth plot above shows, the gain is high and the
pattern is narrow (equivalent Yagi model in YagiMax 3.46). The half-power
beamwidth appears to be about 42 degrees. 








Dimensions



Dimmensions (inches)



El. Length Distance



R 27-5/8 0
DE 26-5/16 6-15/16
D1 11-5/8 13-1/8
D2 11-9/16 23-5/8
D3 11-1/2 29-3/8
D4 11-7/16 38
D5 11-3/8 46-11/16
D6 11-5/16 55-5/16

The post 70 cm Quagi Antenna appeared first on IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
G5RV more ideas

Posted: 30 Apr 2020 06:38 AM PDT
http://www.iw5edi.com/ham-radio/4256/g5rv-more-ideas



The G5RV multiband antenna is a very popular design on the HF bands.








The common G5RV is configured as a 3/2-wave dipole on 20 meters, and works
as either a shortened dipole, or a collinear-fed long wire on the other
bands.




In this configuration, the overall length is 102 ft, with a 28 to 34 ft
matching line.




In some cases, this is still too large to fit in ones yard, and not
everyone can convince their neighbors to allow one to stretch the wire
across property lines. In this case, a 1/2-size version, covering 7 to 28
MHz is useable.




Conversely, some amateurs would like to have 1.8 MHz capability, and have
the 204 ft length necessary for this array. I have dimensions included here
for both the half-size, and double-size G5RV antennas.



Bands...................1.8-28 MHz....3.5-28 MHz...7.0-28
MHzFlat-top.....................204 ft...........102 ft...........51 ft
MATCHING LINESOpen wire...............67.3 ft........34 ft......17 ftLadder
line.............62.4 ft........31.5 ft.....21.2 ft"TV" twin
lead........56.9 ft........28.5 ft.....14.4 ft




[ All of the above-mentioned antennas will work on the 6 Meter band,
sometimes without an ATU.]




Of the listed antennas above, the 7-28 MHz version was referred to in
Louis, G5RVs article in the ARRL ANTENNA COMPENDIUM Volume 1, the 1.8 28
MHz version is in use at Evhan, WB2ELBs QTH, (with a single feedine,
directly matched with the internal ATU in his Kenwood, I am also running
the double-scale G5RV here on 160 6 Meters and the 3.5-28 MHz version in
use by more local hams than I can remember right now.




Just for reference, the ladder line is available at most amateur dealers,
over-the-counter, or mail-order, and the polycarbonate (Lucite) plastic for
the spreaders for home-built open wire is available at any major plastic
suppliers

The post G5RV more ideas appeared first on IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
Beverage antenna information

Posted: 30 Apr 2020 06:26 AM PDT
http://www.iw5edi.com/ham-radio/4254/beverage-antenna-information



The Beverage (or wave) antenna was invented in the early 1920s by Dr.
Harold H. Beverage. It was first discussed in a paper titled The Wave
Antenna A New Type of Highly Directive Antenna written by Beverage,
Chester W. Rice and and Edward W. Kellogg for the journal of the American
Institute of Electrical Engineers (Volume 42, 1923). The paper discusses
testing longwave antennas (7,000 to 25,000 meters; 12-43 kHz) that were 7
miles (11 km) long. This work was done at Riverhead, Long Island, NY, and
mentions shortwave tests around 450 meters (665 kHz) as a practical upper
limit in subsequent experiments. While others have since written about the
antenna, if you can find a reprint of this original work in a research
library, youll find the paper is fascinating reading.




In 1938, the Radio Institute of America presented Dr. Beverage with its
Armstrong Medal for his work in the development of antenna systems. The
Beverage antenna, the citation said, was the precursor of wave antennas of
all types. Dr. Harold Henry Beverage, Stony Brook, NY, USA, passed away on
January 27, 1993 (at age 99).




A classic Beverage receiving antenna requires a lot of space. It is a long
wire, one or more wavelengths long, mounted near to the ground and oriented
in the direction of the desired reception. A nominal 9:1 balun is required
at the juncture of the wire and 50- or 75-Ohm coaxial feedline.The far end
is terminated with a nominal 600-ohm resistance. (When available land will
not permit the installation of a full length Beverage, some people install
short Beverages, ranging in length from about 300 feet up to 600 feet or
so.)




The Beverage antenna is highly directional, responsive to low-angle
signals, has little noise pick-up, and produces excellent signal to noise
ratios. Some say the frequency range suitable for Beverage antennas ranges
(from an Amateur Radio viewpoint) from 1.8 MHz on up to about 7 MHz or so
However, consider the following from Frank, W3LPL:




Subject: Beverage antennas effective on entire HF range
From: Frank Donovan (dono...@jekyll.sgate.com)
Date: October 22, 1995
Organization: (Usenets) rec.radio.shortwave




Properly designed Beverage receiving antennas are very effective across the
entire HF frequency range. At the W3LPL DX contest station we use Beverages
from 1.8 to 14 MHz, and during the sunspot maximum we used them up to 28
MHz!
Beverage arrays (multiple Beverages designed to operate as a phased array)
are even more effective on HF. Ive seen Beverage arrays with as many as 128
individual Beverage elements, each 220 feet long and 4 feet high.









ARRL Books:




Low Band DXing:
Low band antennas (TX and RX, including Beverages), operating techniques;
by ON4UN




DXing on the EdgeThe Thrill of 160 Meters:
160-meter operating, TX and RX antennas, and more; by K1ZM (includes an
audio CD, too).




Beverage antenna articlesfrom QST:
Beverage Antennas for Amateur Communications, QST Magazine, January 1983,
pp. 22-27. (Belrose, Litva, Moss, and Stevens)




The Classic Beverage Antenna, Revisited, QST Magazine, January 1982, pp.
11-17
(H. H. Beverage and Doug DeMaw).




The Wave Antenna for 200-Meter Reception, QST Magazine, November 1922, pp.
7-15
(H.H. Beverage).




K9AY receiving-loop antenna articlefrom QST:
The K9AY Terminated LoopA Compact, Directional Receiving Antenna
QST Magazine, September 1997, pp. 43-46 (Gary Breed).





EWE receiving antenna articlesfrom QST:
Is This EWE For You?, QST Magazine, February 1995, p 31 (Koontz).
Feedback, (Re: Is This EWE For You?), QST Magazine, April 1995, p 75
(Koontz).




More EWEs For You QST Magazine, January 1996, p 32 (Koontz).








Further reading:




The Beverage Antenna Handbook
Victor Misek, W1WCR
142 Wason Road
Hudson, NH 03051




Beverage and Longwire Theory
National Radio Club
P.O. Box 164
Mannsville, NY 13661




The Beverage Antenna
Popular Electronics magazine
January 1998 issue; pages 40 to 46
An article by Joseph J. Carr, K4IPV








Where you can purchase hardware for your receive antenna:








K1FZ offers his model KB-1 and the KB-2 *two-wire Beverage* matching
transformers that include:
-High efficiency wound ferrite toroid transformers with isolated 50 ohm
windings for minimum noise transfer.
-Transformers are housed in attractive, rugged plastic project type boxes.
-Each unit is individually calibrated to eliminate variations found in mass
production.
-The use of large core size prevents saturation from adjacent local
stations.
Website: K1FZ Beverage Antenna Transformers
and




Industrial Communication Engineers, LTD.
PO Box 18495
Indianapois, IN 46218-0495
Tel. 800-ICE-COMM (800-423-2666)
Main Office 317-545-5412
Cust Serv (parts) 317-547-1398
Fax 317-545-9645
Telex I.C.E. 27-440
Website: Industrial Communication Engineers, LTD.




About 1/2 the way down the above ICE webpage, youll see that ICE offers
their Model 180A matching box for $39 (plus shipping). The 180A has taps to
select 50 or 75-Ohm coax feedlines; and taps to match 300/450/600 or
800-Ohm Beverage antenna loads. The 180A has dc blocking capacitors and a
gas-discharge lightning protection system. ICE also sells a Model 181A for
$39 (plus shipping), which allows you to apply a dc voltage into your
Beverage for remote switching. Like the 180A, the ’181A has a gas-discharge
protection system.




Finally, they offer a Model 185A resistive load to terminate your Beverage
with ($34 plus shipping). It has same high-impedance taps as the Model
180A. These units are rated for 10 W of continuous RF and 100 W on peaks.
(I was told that these ratings are not specified for transmitting into the
boxes. Rather, they are what the boxes can withstand when your Beverage
picks up energy from nearby transmitting antennas.) All of these boxes are
made of 1/8-inch extruded aluminum (milled and tapped). And, if you’re
looking to buy American, they’re all made in the USA.




Source KB1GW

The post Beverage antenna information appeared first on IW5EDI Simone -
Ham-Radio.


///////////////////////////////////////////
3 Eelements Yagi beam for 6 meters

Posted: 30 Apr 2020 06:20 AM PDT
http://www.iw5edi.com/ham-radio/4248/3-eelements-yagi-beam-for-6-meters


3 elements yagi for 50 MHz





Spacing between elements are 34 and 1/2 inches.




The elements are 1/2 inch aluminum tubing of 1/16-inch wall thickness.(you
can cut up an old TV antenna they work great).




The Boom length is 72 inches (6 feet).The boom is 1 and 1/4 inch tubing.




You can attach 50 ohm coax to this antenna after you add a gamma match.




To attach the gamma rod to the antenna you will need to mount an SO-239
chassis connector to the center of the driven element.




This can be made from a piece of sheet metal about 1 inche wide by 3 inches
long.




Bend the long side of the sheet metal into and L-shape so that you now have
a 21 inch surface and a 11 inch on a 90 degree angle.




Then center punch the 21 side and mount the SO-239 connector in the middle.




Next bend the 11 inch surface onto the center of the driven element and
secure it with 2 sheet metal screws.




Gamma Mount Bracket








Now you will need to get some more sheet metal to build the SHORTENING
strap of the gamma this may vary in size depending on the tubing size and
the space from driven to the gamma match.




The gamma match is mounted along the side of the driven after you have
soldered the innner conductor of the gamma to the center od the SO-239.




The spacing is usally about 1.5 to 2 inches from the driven element (Dosent
make much difference).




To make the SHORTENING strap make a 1 inch strip about 6 inches long. Take
this strip and bend it around the driven and over to the gamma.




Make sure it folds back over so that you can drill 1 hole at each.

The post 3 Eelements Yagi beam for 6 meters appeared first on IW5EDI Simone
- Ham-Radio.