[IW5EDI] 7 element Yagi for 20 Meters band

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

IW5EDI Simone - Ham-Radio

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7 element Yagi for 20 Meters band

Posted: 03 May 2020 02:01 AM PDT
http://www.iw5edi.com/ham-radio/4369/7-element-yagi-for-20-meters-band-2







They say if it didnt blow down it was not big enough, this one was big
enough and it did blow, not off but up and over the top of the tower like
an umbrella one very windy day in January 1974. I was at work and the XYL
called and said the thing blew off the top of the tower- WOW, I imagined it
in somebody’s living room. In fact it did not blow off it blew over the
top, broke in two and slid down about ten feet an hung on the safety
cable. When I originally built the thing I rigged this safety line of 3/8
inch aircraft cable from the tower to the four inch diameter boom just in
case. I remember I used to laugh when I told people about the safety cable
never thinking it would actually blow off the tower. The storm was really a
bad one, very high winds with ice covering the boom and elements. In fact
a drive in movie screen blew over just down the street from me. It was a
very sad occasion, I was the one sad and the neighbors were glad. The
obliging neighbors called the building inspector and he was waiting for me
when I got down from the top after attaching a rope, disconnecting safety
cable and cutting the coax cable and letting it down, smoothly. The
inspector notified me that one of my neighbors said that it had blown down
three times already this year. This beam worked very well for me for
several years.








I apologies for the quality of the photo. Its the only one I have. What
you see is what you get. Very narrow beam pattern, thats not QSB man
thats my beam swinging in the wind.




The omega match was motorized because it was so far out on the boom.

The post 7 element Yagi for 20 Meters band appeared first on IW5EDI Simone
- Ham-Radio.


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Long Loopstick Antenna

Posted: 03 May 2020 01:58 AM PDT
http://www.iw5edi.com/ham-radio/4365/long-loopstick-antenna



Wound on a 3 foot length of PVC pipe, the long loopstick antenna was an
experiment to try to improve AM radio reception without using a long wire
or ground. It works fairly well and greatly improved reception of a weak
station 130 miles away. A longer rod antenna will probably work better if
space allows. The number of turns of wire needed for the loopstick can be
worked out from the single layer, air core inductance formula:




Inductance = (radius^2 * turns^2) / ((9*radius)+(10*length))




where dimensions are in inches and inductance is in microhenrys.













The inductance should be about 230 microhenrys to operate with a standard
AM radio tuning capacitor (33-330 pF). The 3 foot PVC pipe is wound with
approximately 500 evenly spaced turns of #24 copper wire which forms an
inductor of about 170 microhenrys, but I ended up with a little more
(213uH) because the winding spacing wasnt exactly even. A secondary coil of
about 50 turns is wound along the length of the pipe on top of the primary
and then connected to 4 turns of wire wound directly around the radio. The
windings around the radio are orientated so that the radios internal
antenna rod passes through the external windings. A better method of
coupling would be to wind a few turns directly around the internal rod
antenna inside the radio itself, but you would have to open the radio to do
that. In operation, the antenna should be horizontal to the ground and at
right angles to the direction of the radio station of interest. Tune the
radio to a weak station so you can hear a definite amount of noise, and
then tune the antenna capacitor and rotate the antenna for the best
response. The antenna should also be located away from lamp dimmers,
computer monitors and other devices that cause electrical interference.

The post Long Loopstick Antenna appeared first on IW5EDI Simone - Ham-Radio.


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Small Loop Antennas

Posted: 03 May 2020 01:56 AM PDT
http://www.iw5edi.com/ham-radio/4355/small-loop-antennas



Low profile operating SMALL LOOP ANTENNAS




Magnetic loops are very effective small antennas. these 3 to 3 1/2+ foot
antennas perform close to and in some cases (low mounting heights for one)
better than even a small beam. The reason is that a magnetic field is much
more concentrated than an electrical one, for example a small horizontal
loop at 17 feet performs better (lower radiation angle) than a full size
dipole at 35 feet, in fact better for DX than a beam at that height because
of the much lower takeoff angle. If you place a beam 1 foot off the ground
it will only radiate straight up while a vertical loop will still work DX
stations quite well.




This smaller more intense magnetic field also has the advantage of greatly
reducing TVI RFI potential if the loop is more than 15 feet or so away
from TV antennas, electronics ect. Another advantage of this magnetic field
is the very low background noise heard on the loop because most man made
noise is electrical fields. For example if you lived next to a Shopping
Mall the loop would not hear all that lighting and power transformers. Also
reducing interference is the loops Hi Q which means that it receives &
transmits on a narrow band range compared to the full size antennas.




This effect is very pronounced on the lower bands that the loop will work.
I have built several loops and along the way have learned quite a bit about
these little wonders. Usually I use the parts from one to make the next but
my ugly loop is one that I keep in service.








While looking thru old QSTs I read up on the Cushcraft R-3 vertical
antenna. I made a mental note that the remote controlled variable capacitor
looked like it would make an ideal loop component. I found this one on
E-Bay for about $25, this was nice considering the most expensive part of
the loop is the High Voltage Variable Capacitor and motor drive and
controller.The only drawback to this capacitor was the metal mounting
(which increases the stray capacitance) and the fact that it was a single
stator type not the less lossy butterfly type.




To reduce the losses I directly connected (metal braid) the shaft on the
capacitor to the loop itself and polished the capacitor plates to increase
power handling. The range of this setup was around 30 thru 180 pf and it
will handle 100 watts. I could of reduced the minimum value of the
capacitor by eliminating the metal half (future project ?) of the mounting
but instead used it as part of the loop. I wanted to test some of the
current theories of loop design and this setup was ideal. I built up a PVC
frame (easy change of dimensions) and used of all things roof flashing
(very thin aluminum) for the loop itself. This cheap material made
dimension testing easy, the final size of the loop is 42 in diameter by 1.6
wide. One thing that the loop programs (like mloop32) do not take into
account is the fact that if the material is too wide it starts acting like
a capacitor not just an inductor. This loop is completely assembled with
mechanical (nuts & bolts) connections.




This is a big no no in loop construction which I used to make testing of
different configurations easy and to test that all connections must be
welded theory. On the air tests, field effects and bandwidth checks have
shown that this loop is very efficient until you tune to 40 meters (around
7%), not that surprising since that band is below the theoretical range of
a 42 loop. It sure is fun to stretch it that far and to make 40 meter
contacts on such a small antenna. The loop is feed with an 8 diameter
faraday loop not on the centerline (null) of the loop, this is because the
capacitance circuit break is on the side of the capacitor assembly.




The pictures show how the control wires are routed off center but this is
in the null of this loop, if you dont do this the wires will couple with
the magnetic field and detune the antenna. I found very little performance
change with the feed loop off center so I left it there for mechanical
simplicity. I learned the hard way about the high voltages (8,000 V +) in
the loop when insulators in the path of RF flow started burning thru (bad)
until redesigned. The R-3 controller does a good job of tuning the loop 19
thru 7 MHZ, its meter is a position feedback that lets you know where the
capacitor is tuned. A loop like a commercial version like the MFJ HI Q Loop
(below) or a home brew may have the unique properties that may help you out
in your situation.




NOHC Article originally available at www.geocities.com/n0hc

The post Small Loop Antennas appeared first on IW5EDI Simone - Ham-Radio.


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MFJ-940 modification

Posted: 03 May 2020 01:52 AM PDT
http://www.iw5edi.com/ham-radio/4348/mfj-940-modification



The MFJ-940 VERSA TUNER II is a useful little antenna tuner for the
HF-bands. However it suffers from a minor design error, which can be easily
rectified.
As other antenna tuners may show the same kind of weakness, the
modification described here can be used to improve other types.




The connection between the components in the tuner coax connectors,
switch, coils and variable capacitors are made of rather long pieces of
tinned copper wire.









These wires act as small selfinductances. In normal operation stray
inductances are absorbed by the tuning components, however when the tuner
is switched into bypass mode, it affects the 50 ohm match between antenna
and transmitter. This is worst on the highest frequencies.
You can check an antenna tuner by measuring the VSWR through of the tuner,
when it is terminated by a good 50 ohm load. In my case I could measure a
VSWR on 30MHz of 1.8:1 not very good for a simple bypass!





The solution is to compensate the series L from the wires with parallel Cs.
By doing this in the upper end of the frequency range a broadband match can
be obtained.




In the MFJ-940 five 15pF capacitors are used. Four from each of the four
coax centerpins to ground and one from the switch rotor to ground. This
completely tunes out the reactance of the internal wirering. see modified
diagram.




The capacitors must be able to handle high voltages Im using 500V ceramic
tubular types and have no problems at the 100W level.




This modification improves the return loss at 30 MHz from -12dB to -30dB
and at the same time reduces through loss (attenuation) from 0.3dB to only
0.1dB.
By OZ2OE originally at hjem.get2net.dk/ole_nykjaer/oz2oe

The post MFJ-940 modification appeared first on IW5EDI Simone - Ham-Radio.


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Six Meter Wavelength Band Antennas

Posted: 03 May 2020 01:48 AM PDT
http://www.iw5edi.com/ham-radio/4344/six-meter-wavelength-band-antennas



The advent of new, affordable MF/HF/VHF radios in the last few months from
virtually all the major manufacturers, has spurred a migration by more and
more Hams to the Six Meter band. Im often asked, What antennas are best for
Six Meters?. Before answering a question like this, I must first ask the
Ham what he or she knows about the band, and in what sort of activity they
want to engage. Often times Ill get a response such as, Well, I just want
to get on six!.

Next Ill want to find out what sort of a Six Meter station the person might
already have. As often as not, my preconceived notion of the Ham owning an
MF/HF/VHF transceiver is dispelled. They may tell me that they have a 50
Watt FM transceiver, or maybe a Six Meter hand-held radio. They usually
follow this response by indicating that they are really anxious to work
some of that Six Meter DX they have been hearing about! My task has at this
point fallen to explain the entirety of activity on the band, and what is
needed for each of the various modes of communication available on the band.









You see, the Six Meter band works almost as if it were two distinctly
different bands rolled into one. Down at the low end of the band most
operators are interested in working distant DX states and countries on
Single Sideband (SSB) or Morse code iCW. At the upper end of the band the
predominant mode is Frequency Modulation (FM).

Most of the people that youll find at the top of this band have used it for
years and years as a sort of quiet intercom channel to talk with college
buddies or other friends. In this upper portion of the band the activity is
similar to the two meter band, with perhaps a better sense of manners and
operating skill. The lower end of the band is where the Big Fun is! In this
lower spectrum, distant (DX) signals are often found, resulting from a
myriad of propagation sources. This is why Six Meters is known as the Magic
Band!

Why 6 Meter Hams Design The Best Antennas
At this particular juncture in time we are quickly approaching what
seasoned Six Meter Hams call F season. This is because in the next several
months we will see a transition from relatively low Solar Indices numbers
hovering at about 100, to an increase that we all hope will exceed the 168
solar indices peak of 1958. During this 1958 peak, many Hams worked all
states within our country, and several zealous individuals worked all
continents.

Other signal propagation modes are also common on this band. Even at times
when signal propagation is shut down on the HF bands due to solar storms
called proton events, Six Meters will often yield Auroral skip. This can be
really fun to operate, and is distinguished by the eerie and gravelly
sounding phase distortion that occurs.

Another mode of propagation I have enjoyed over the years is Meteor
Scatter. The best meteor skip I have successfully worked is during the
Geminids and Ursids showers in December. I have also though had good luck
on occasion with the many showers that occur in June and July. Here is a
listing of these, and the approximate dates of their peak:

Scorpids June 2 through 17    Perseids June 4 through 6    Arietids June 8
Pons Winnecke June 27 though 30    Taurids June 30 through July
2    Cygnids July 14
Capricornids July 18 through 30    Perseids July 25 through August 4    

Meteor skip allows about ten to twenty minute conversations or QSOs as the
earth rotates below the ionized meteor trail. You might think of this sort
of propagation as the billiards of Ham Radio. The way this works is that
signals from my station in Anaheim go up and bounce off the meteor trail
and come down in Texas. As the earth rotates, twenty minutes later I can
talk to a station or stations in New Mexico. The arc of this propagation
will ultimately yield contacts for me in Utah, Idaho, Washington and Canada
before the signal starts coming down in the Bering Sea. I have seldom
worked Alaskan stations via this mode of propagation but, I hope to as more
Hams acquire Six Meter equipment! It would be nice to follow this
propagation all the way to Russia. I have never worked any Russian stations
however, probably due to the economic and political situation of the then
Soviet Union.

A final form of skip that is often mis-judged by Hams who exploit it even
on 10 or 12 Meters is Sporadic E-Layer skip. The ionospheric E layer
resides above the earth at approximately 80 miles up. The F1 and F2 Layers
by contrast are about 60 to 200 and some miles higher. This is why F layer
skip typically yields further contacts because of the consequential lower
angle of propagation. E skip on Six Meters is a very common occurrence
during the months of April through July. It is believed that stimulation of
the E layer occurs at this time because of high thunder head conditions
during spring storms. I have tracked and confirmed this sort of activity in
the past by correlating it to weather warnings given to airline pilots.
Generally speaking, the Six Meter activity will come about a day or two
after the highest thunder storm activity. This sort of skip yields single,
double and even triple hop skip. During one E season when two E-clouds were
simultaneously over the midwest and southwest on the weekend of the June
VHF contest, stations all over the country were talking to one another on
Six Meters. It was an unusual sort of gentlemanly bedlam that covered
better than 300 KHz. at the lower end of the band!

Back to Antennas
If youre interested in Upper Sideband (USB) you will run into folks who
will tell you that you should use a horizontally polarized antenna,
probably a Yagi Uda beam. If you want to work FM, everyone will tell you to
use a vertically polarized antenna such as a Ground Plane or a J, since
thats what the mobile stations and everyone else is running. Well, heres
the low down scoop so you can have your cake and eat it too!

Use a vertical omni-directional antenna for both modes, actually all modes,
and you will have the best of all possible worlds! I say this based on my
own experience, as well as others who have worked a great deal of DX with
vertically polarized antennas. For about 31 years now I have used vertical
omnis on this band to very good success. Ive worked all 50 states, and four
countries, most times running not more than about 100 watts of power.

I’m not knocking beam antennas such as Yagis or Cubical Quads, I have used
them too! What I’m really saying though is that I have learned to put them
up vertically polarized as opposed to using them in horizontal
polarization. One station I can think of has worked all states more than
twice over, as well as working all continents using a pair of vertical five
element Yagi beams.

The reasoning behind this becomes more clear if you consider that
propagation on this band is more often similar to that of an High Frequency
(HF) band, rather than a VHF band. On bands like 2 Meters or 222 MHz., when
you operate Single Sideband (SSB) you would probably be foolish not to use
a horizontal antenna. In my experience on the Six Meter band, signal
propagation comes in most times at an angle that is closer to the vertical
plane, than it is to horizontal.

About the only time using a vertical antenna would be a disadvantage would
be trying to talk to a horizontally polarized station within your direct
wave range. This would be a station within about 50 miles of you. In this
circumstance about an additional 20 Decibels of attenuation would be
imposed between the cross polarized stations. In reality though all Six
Meter stations should have an omni-directional vertical antenna. With such
an antenna you will be aware of the prevailing activity on the band, even
if you then switch to some other antenna to optimize that activity.

So what sort of vertical omnis are desirable? Ground Planes work well,
either the 5/8 wavelength variety or even simple 1/4 wavelength versions.
These can often be fabricated from easily modified Citizens Band antennas.
The venerable J antenna is though, probably both the simplest to build, and
the best overall performer. One major reason the voltage fed J is nice is
that it can be constructed to provide enough bandwidth to utilize almost
all of the band. This allows you to have one antenna that can be used for
FM, AM, SSB, or CW. So, what must be done to provide this wide bandwidth J
antenna?

Bandwidth in an antenna is a function of the antennas circuit Q, or circuit
quality factor. If the antenna provides the lowest possible reactance, the
Q will be improved, and consequently so will bandwidth. To provide the
lowest possible reactance, or Alternating Current (AC) resistance, we could
either use large diameter conductors, or maybe plate the antenna with some
nice low resistance conductive material like Silver. I think using fat
large diameter tubing is probably the better and more economical approach!

Usually 3/4 inch diameter tubing is used for Six Meter J antennas. If this
seems like a desirable mechanical configuration to you, here are the
dimensions for such an antenna fabricated from copper tubing. Actually it
uses 1/2 diameter tubing also but, hang in here with me, well make use of
this smaller diameter tubing in a later modification for higher frequency
bands!

First, let me explain how we do these measurements! Start all your
measurements from the top edge of the bottom of the antenna. This means the
top edge at the bottom of the Q-Line or Linear Impedance matching
transformer that is formed by the two parallel quarter wavelength tubes. So
lets get started by listing the parts you will need.

The J Shopping List

    * One 10 foot length of 1/2 inch copper tubing
    * Two 10 foot lengths of 3/4 inch copper tubing
    * One 3/4 inch T fitting
    * One 3/4 inch to 1/2 inch reducer
    * One 3/4 inch elbow fitting
    * Two 3 inch by 2 inch by 1/2 inch thick pieces of Plexiglas flat stock
    * One coaxial SO-239 chassis mount connector, or maybe a chassis mount
N connector
    * 6 inches of #12 American Wire Gauge (AWG) THHN solid copper wire
    * One ring type crimp-on terminal to attach to the connectors flange

You will also need 4 appropriately sized screws, nuts and lockwashers for
the connector and, also eight (8) 3/16 inch machine screws and lock nuts
for mounting the Plexiglas plates.

[6mtrJ.gif] Putting This Puppy Together
Remember to clean and polish all these copper pieces, as well as the tip
ends of the tubing that will fit onto them before soldering! Use non-acid
solder!

Use a tubing cutter so as to make nice smooth even cuts. Cut one length of
3/4 inch tubing such that it is 59 inches long when seated with the elbow
fitting and mated to the shorter leg of the T fitting. You will need a
short piece of tubing to accomplish this so that proper spacing can later
be accomplished. Next cut the second piece of 3/4 inch diameter tubing such
that when it is fitted within the top port of the T fitting, it is parallel
to the 59 inch piece, and its total length is 109 inches. When this has
been done, adjust the center to center spacing between the two parallel
tubes to 2.750 inches. Make sure they are still exactly parallel, and
solder these pieces together.

Place the reducer on top of the longer piece, and cut a 1/2 inch diameter
piece to exactly 50.25 inches. Clean up this last piece and solder it in
place. Let the antenna cool off while you fabricate the Plexiglas bracing
plate, and feed-point connector assembly.

Drill a 5/8 inch hole in the exact center of one of the Plexiglas plates.
Place the coaxial connector you are using in this hole, and mark the plate
for each of the small mounting screws. Drill these four holes, and also
four holes near the corners of the plate where it will be mounted to the
Q-line.

Snip the 6 inch wire in half. From one end of each wire, strip about a 1/2
inch of insulation. Strip about 3 inches from each of the other two ends.
One piece of wire will be soldered to the center pin of the connector at
the 1/2 inch stripped portion. The other piece of wire will have a ring
connector installed at this point. The ring connector will later attach to
one of the flange screws for the connector.

Place this finished Plexiglas connector assembly such that it is straddling
the two parallel tubing pieces. Using a pencil, mark positions beneath this
plate to drill holes for soldering the 3 inch stripped portions of wire.
The center pin wire will connect to the longest piece of tubing, and the
shank side of the connector will be soldered to the 59 inch Q-line. These
connections will be made exactly 5.300 inches above the top edge of the
lower end of the Q-line. This is a very critical dimension! It affects the
feed point impedance, and the resulting antenna Standing Wave Ratio (SWR).
Bolt this plate assembly in place with four 3/16 screws and lock nuts.
Place the second similar plate on the Q-line about six inches below the top
end of the Q-line, and bolt it in place.

When the antenna is mounted high and in the clear of all nearby objects, it
should provide a good low VSWR over most of the lower two and one half to
three megacycles of the band. It is desirable to mount this antenna at
least 30 feet in the air, and higher if possible. I would also recommend
the use of high quality 50 Ohm coaxial cable such as Belden RG- 213/U. To
mount the antenna, you can use a threaded plumbing fitting, or make a
mounting bracket fabricated from 1/4 inch thick aluminum plate stock and TV
antenna type U-bolts.

Later modifications to this antenna could also allow it to be used on the 2
Meter band, as well as the 135, and 70 Centimeter bands. This can be done
by exploiting the odd order harmonics of the Six Meter band, or better, by
adding Q-lines for these other bands.

Other Antennas for 6 Meters
While we are thinking about the Six Meter band, lets consider some antennas
that will work on this band that are not often appreciated. The
manufacturer Hustler makes such an antenna, and so does Larson.

The Hustler top loaded HF mobile antennas will work on 6 Meters. This is
because the supporting mast is 54 inches long, which is 1/4 wavelength on
the Six Meter band. You can use this antenna on Six, even while one or more
resonators are attached above the mast for various HF bands. This is
because the inductively loaded resonators become RF Chokes at 50 MHz.

This way if you have resonators on the antenna for lets say the 40 Meter,
20 Meter, and 10 Meter bands, you have a 4 band antenna as it will also
work on Six! It will even work on the 2 Meter band. This is because 54
inches is pretty close to 3/4 of one wavelength on 2 Meters, and this odd
order harmonic relation will allow the antenna to be close to a 50 Ohm
impedance match as well. The radiation pattern on 2 Meters won’t be the
greatest but, you will probably find that as a mobile antenna on your car,
this system works well for the entire HF through 2 Meter spectrum.

Another 2 Meter antenna that will also work on 6 is the Larson 5/8 wave
mobile antenna, or the Hustler 2 Meter Buckbuster 5/8 wave 2 Meter antenna.
Electrically this 47 inch antenna looks like a base loaded 1/4 wavelength
antenna on 6 Meters, and up on the roof of your car, it will be quite
efficient!

A Super Six Meter Setup!
Finally, let me suggest an approach that should yield both good electrical
performance, and provide the signal gain of a beam antenna. This system
should prove to be a good way to go for the Ham who has not yet installed
an antenna tower. It also has the advantage of allowing the Ham to
electrically switch the antennas position randomly, and in effect, scan for
signals. This approach is to take four vertical omni-directional antennas
and point them by means of a coaxial phasing arrangement.

I am quite enthusiastic about this antenna because it might allow, in a
later configuration, an antenna that can be automatically operated by a
computer. If another plan of mine comes to fruition, 6 Meter Sporadic E
layer, or Meteor Scatter could be worked automatically on 6 Meter Packet
radio. The national 6 Meter Band Plan uses 50.620 MHz. as the Experimental
Packet frequency. This allows for any legal baud rate (which would
practically mean any baud rate from 300 to 9600 baud) and encourages
experimentation. No one that I am aware of up to this point in time has
utilized packet for working this sort of DX ! It would be a beautifully
workable scheme, and allows for some good and timely scientific activity.
We as a hobby avocation need to use computers for more than (stupidly 1200
baud) slow packet messaging!

The vertical omni I would prefer is this same design J antenna. This
particular sort of antenna provides excellent control of reactive matching
impedances via its quarter wavelength linear impedance matching
transformer. It also by happenstance gives us a physical advantage, as we
can get what might prove to be a cumbersome configuration of antennas a bit
higher in the air. My design thoughts for this antenna system should allow
for putting the high current point of the antenna at about 25 feet, when it
sits atop the roof of a house that is ten feet tall. This puts the
radiating portion of the antenna about 1.3 wavelengths above ground. This
then can be done with what would otherwise become the wastage of the copper
tubing not used for the one antenna itself.

The configuration of these antennas is commonly known as a 4 Square
arrangement. This configuration places the four antennas at points of a
square that are one quarter wavelength per side. The mathematical dimension
calculation for this physical mounting works out this way. :

300/50 MHz. = 5.88 Meters
5.88 X 39.37 = 231.59 inches
231.59 Meters/4 = 57.89 inches

The above formula embodies these perameters. Three hundred (300) is the
velocity or speed of the signal transmission. Actually this is 300,000,000
meters per second but, since we are dealing in Mega cycles, we can truncate
six zeros. At this point in the formula we have the actual metric
wavelength of signal propagation at 51 MHz. 51 MHz. is chosen to put the
design frequency in the middle of the antennas practical bandwidth.

If we then multiply this by the number of inches contained in one meter
(39.37) we have this same wavelength converted to inches. Dividing this
231.6 inches by four gives us 57.89 inches. Placing the antennas in a
square that is 58 inches per side is quite close enough and accurate for
practical purposes. Take note that the length for phasing Delay Lines for
electrically feeding these antennas will be further modified to allow for
the Velocity Factor of the coax cable used!

The above described antenna system should in theory result in 5.2 decibels
of directional signal gain. In a future article I will explain the
mechanical mounting components as well as the phasing lines and switch box
control. A future iteration of this design may allow for computer control.
This would actually be quite easy to do, and as soon as I can justify
building the system myself, or finding someone who finds this idea as
attractive as I do, we might collaborate together. It would be great to
find someone in the Texas up through Washington state one hop skip zone
that is a single skip zone away from me. This would allow for initial
testing on a more or less regular basis! Send me some e-mail if your
interested!




Article by Wa6BFH originally at
/www.geocities.com/SiliconValley/2775/6mjant01.html

The post Six Meter Wavelength Band Antennas appeared first on IW5EDI Simone
- Ham-Radio.


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Stacked Yagi Antennas

Posted: 03 May 2020 01:44 AM PDT
http://www.iw5edi.com/ham-radio/4328/stacked-yagi-antennas



This article was obtained from VE3GK experiences, constructing and
designing full size, single band stacked yagi antenna arrays, special
rotating, electric powered, telescoping towers and rotators. All the test
results are from first hand experiments. VE3GK kept a record of these
experiments and construction details and offer them for your interest.












HISTORY




I started out in amateur radio with wire antennas. Directional antennas
were next and I erected a commercial tri-band antenna, tower and rotator.
Another amateur, nearby, used a wide spaced mono-band 20-meter beam, which
blew me away every time. From this experience I felt that my set up left a
lot to be desired.




I started with a 5-element 20-meter mono-band yagi on a 48-ft boom. As the
years passed several different home made full size long boom multi-element
yagis were mounted singly and in the stacked array configuration on
modified lattice towers. These towers were modified to rotate to
accommodate the stacked array set up.




Antennas were eventually mounted on two home designed and home made
continuous heavy duty telescoping rotating tubular steel towers. Stacking
separation distances and overall height above ground experiments were
conducted on the large tower on a small mountain 65 miles south of Ottawa
at our summerhouse. In the winter time, in Ottawa, I experimented with a
smaller, 75 ft rotating telescoping home made tower. The tower is designed
for continuous operation. I try to lower the thing out of sight in the
trees, in its parking position, every time I leave the shack for over 30
minutes or so. Out of sight, out of mind, for my neighbors. (My stealth
equation HI) This tower also tilts over electrically with a permanent 5 in
diameter, 12 ft high gin pole mounted in the cement base.








This in a neat arrangement for ease of antenna installation and adjustment.
With the exception of the commercial tri-bander all of the hardware
presented in this paper is home constructed and home designed.




My present radiating system is a 20- meter, four over four stacked array
with yagis on 40-foot [12m] booms at the summer place. All of my mono-band
yagis use odd spacing with a close coupled first director and placed 0.1-
wave length in front of the driven element. The top beam is usually at
90-feet [27m] and the bottom one at 42-feet [12.6m] when in the stacked
arrangement.




The Gk Hb 44 20 Meter Stacked Array On A Hb Skyneedle Tubular Steel Tower.




Two 4 element 40 foot boom yagis fed in phase. When up, one at 95 feet and
the other at 38 feet. When nested, one at 28 feet and the other at25 feet
above ground. Nesting happens automatically in wind gusts above 60 kph,
when I leave the property and at the end of operating hours or evening shut
down. The time travel is 7 minutes 40 seconds up or down. There is a manual
crash descent, (Letting the tower free wheel down), of 30 seconds in case
of a sudden storm. The estimated tower weight is 2.5 tons, 2 tons are
active when the tower is under power. This weight is supported by the lift
cables (16 tons capacity) at all times. The tower is freestanding,
telescopic, rotating, remote control, double safety devices on all tower
sections and lift cables. Automatic end stops on the tower extension and
nesting positions. Also safety devices on full cw and ccw rotation
parameters. The hoist and rotator parameters are monitored on close circuit
tv using two tv cameras. Audio feed-back information is feed back with a
baby monitor.




The following conclusions are based on my own full size live tests, and are
to be weighed accordingly.




I want to thank those people who helped me with all the antenna tests. I
especially want to thank those who were patient enough not to shoot me off
the top of the towers during the tests.




NOTE:




In the commercial antenna market their seams to be an emphasis on working
as many bands as possible on one boom with mediocre results on any one
band. Don’t believe the claims that multi-band beam antennas exist that can
compete with antennas designed for one band. Log periodic beam antennas are
not high gain antennas, they are wide band coverage devices that have gain
compared to that of a 3 element beam antenna , designed for one frequency.




In Ottawa I use a commercial 5-element tri-band yagi on the telescoping,
rotating, 75-ft tower. This fall and Winter it is my intention to stack
another identical tri-band yagi on the tower at 25 ft. These experiments
are possible because I can adjust the stacking separation distance for 10
and 15 meters. I will not be able to stack on 20 because the top beam is
not high enough. (The tower is higher but not capable of supporting the
weight of the heavy tri-bander on the top section








MEASURING GAIN WITH REFERENCE TO A DIPOLE:




Measuring gain with absolute certainty is very difficult because of all the
variables. However, as far as I can determine the gain of the present 4X4
array is about 11 DBD. [db reference to a Dipole]. The single 40 ft long 4
element beam is responsibly for about 8-DBD and the stacks at 3/4 wave
separation with the top one at 90-ft add another 3-DBD to the results for a
total of 11-DBD.




Antenna gain is measured with reference to power gain. For example; when
the power of an amplifier is doubled from 100 watts to 200 watts, the
resulting gain would be 3 DBP; the P stands for the previous condition or
situation. This 3 DB factor comes from the formula that states that power
and therefore, antenna gain is equal to 10 times the log, to the base 10,
of the new situation divided by the old situation. Here the new power
divided by the old power equals 2, the log of 2 equals 0.3 and 10 times 0.3
equals 3, 3DBP gain.




A practical antenna gain measurement could be done as follows: Mount a
20m-reference dipole and oriented it at the proper height, far enough away
to de-couple any interaction with the test array. Apply 100 watts to a
dipole as indicated on a good wattmeter such as the BIRD 43. Have another
amateur, at least one skip distance away, and note his S meter reading.
Then apply power to the test array and reduce the power and one should get
the same S meter reading with lower power. This operation has to be done
very quickly to out-run any QSB on the band. In my case with the present 44
array I am able to get the same S meter reading with only eight watts.
Divide this 8-watt power level into the 100-watt reference and the results
will be approximately 12. The log of 12 is about 1.1 and 10 times 1.1
equals 11, 11DB. Arriving at an honest DBD gain factor is very simple.




THE GAIN STORY:




1. The mathematical Isotropic RF point source. zero gain (RF point source
inside a sphere>>>> NO RF BURNS).




2. The dipole, approx. gain over the isotropic point 2.15-DBI




(Because of its butterfly pattern)




3. 2-el 80 meter rotating diamond quad, 40-ft [12m] boom diamond tip at
117-ft. [35m](North American QRM down 7-S units on the side when working
Europe)(GK 91) gain 5-DBD




NOTE: from this point on, all reference to gain is related to the dipole.
[DBD].




20 METER ANTENNAS:




4. 2-el quad 12-ft [3.6m] boom. (GK 67) approx. gain 5-DBD




5. 3-element 19-ft [5.7m] boom. (GK. 69) approx. gain 5-DBD




6. 4-element 26-ft [7.8m] boom. (204BA) approx. gain 7-DBD




7. 4-element 40-ft [12m] booms. (GK. 91) approx. gain 8-DBD




8. 5-element 50-ft [15m] booms. (GK. 85) approx. gain 9-DBD




Probably the limit for practical HF gain return for effort




and money with single yagis)




9. 7-element 65-ft [19.5m] boom. (GK. 74) approx. gain 9-DBD




(I KNOW, I KNOW, BOOM TOO SHORT)




10. 3 X 3 stacks, 25-ft [7,5m] (GK. 75) approx. gain 9-DBD




(Each of the following stacks had a minimum of 0.75 stacking separation)




{booms}




11. 4 X 4 stacks, 30-ft [9m] (GK. 76) approx. gain 10-DBD




12. 4 X 4 stacks, 42-ft [12.6m](GK. 77) approx. gain 11-DBD




PRESENT ARRAY:




13. 4 X 4 stacks, 40-ft [12m] (GK. 97) approx. gain 11-DBD




14. 5 X 5 stacks, 42-ft [12.6m](GK. 80) approx. gain 10.5-DBD [BOOMS TOO
SHORT]




15. 5 X 5 X 5, stacks 50-ft [15m] .. approx. gain 13-DBD




(15. probably the limit for effort and gain return for HF




single stacks) listen to Ivor, GI0AIJ.




16. 4 X 4 by 4 X 4 collinear stacks, approx. gain 14-DBD




17. 5 X 5 by 5 X 5 collinear stacks, approx. gain 15-DBD




(17. probably the limit for effort and gain return for HF collinear stacks)




Simon, OH8OS, in Finland, had a 6X6 by 6X6 by 6X6, 60-ft booms




horizontal separation of 60-ft, Top antenna over 200-ft




above ground. A total of 36-el. Approx. Gain ??-DBD




WOW! Is this a 20-meter monster antenna array or what?




Note: A dipole would have to be driven with a bunch of kilowatts of power
to equal the output from the OH8OS array with bare-foot power. All that
power into a dipole with no receiver gain. WOW! For instance, you would
have to drive a dipole with about 700-watts to equal the output power of a
204-BA, Hygain 4-element beam with only 100 watts drive power. Can you
imagine the legal power limit to the array OH6OS used, don’t fry, oh sorry
fly, in front of the sucker if Simon were to sneezed into the microphone.
HI.




GAIN




GAIN REALLY HARD TO COME BY:




LONG BOOM SINGLE BAND YAGIS:




When a person asks what’s that big aerial thing doing up there..EH ? I
always say. If you think the aerial is big, you should see the size of the
TV set.




That’s not QSB man. It’s the wind blowing my antenna around. My 7-element
on a 65-ft [19.5m] boom had a very narrow beam pattern. It was also big
enough because it blew up and over the top of the tower in a January
ice-wind storm in 1975, more later. It was my first JC antenna. People
would drive by and fall off the road. Other amateurs would drive by with
their spouses and suggest a tri-bander! If you hear a big signal break the
pile up, listen to the description of that station. I can assure you, a lot
of time, money and effort has gone into the signal. Some people rationalize
the strength of a very strong signal by assuming high-power. I’m accused of
running over power. I sometimes say, I’m running illegal antennas.




Note: the reflector for this ve3gk 6 element 20-m yagi is sitting on the
ground at the base of the tower




This antenna was used as a reference source for my 5X5 and 4X4 stacked
arrays for a period of time. My QTH was about 6 KM away.




<<




Ve3gk, doing his walk the boom trick in my younger stupid days! Near home
brew 60-ft 20-m yagi at 90-ft




VE3GK antennas..




Over the years, there has been some big, long boom yagis up. The photo to
the right shows W4GNR sitting at the top of his 140 ft high tower on the
120 ft long boom 20 meter yagi up at 140 ft. I remember a 20-meter yagi in
the early 1960`s in the mid west USA, a real monster. The thing had 12
elements on a 150-foot [45m] boom up 150-feet [45m]. A real cannon, it
surely would have been a sight to behold. With what we know now this
antenna would have worked more efficiently with fewer elements. It was also
up too high for in close DX such as Europe because of its very low launch
angle.




Remember; gain from a long boom single band Yagi comes from the focusing of
the frontal lobe by the extra director’s way out on the boom. From my
experience, when you have a long boom the forward gain and the front to
back ratio is one and the same because of the refined frontal pattern.




The take off angle to the horizon is mostly related to the antenna height
above true flat ground for single yagis. If one gets involved with a
stacked system its a different ball game. A tacked system modifies the take
off angle with startling results. From my experience, it eliminates one
skip distance to Europe. My advice is that you do the best you can with
what you have and go for it. As a rule, single antennas will work really
well at one wavelength above ground. The antenna performance will really
come alive at 1.5 wave-lengths above ground (99-ft for 20 meters). You will
be amazed with your new signal. If the antenna is placed much higher the
in-close path to Europe from North America will suffer. Asia and the Indian
Ocean area will be better so you have to make a choice. The next paragraph
could solve this Delrina.




THE TELESCOPING TOWER:




With a remote controlled, telescopic tower, one can experiment with the
launch angles for changing DX openings. As far as I can tell the towers
that I have built are the only ones that have the ability to fully rotate
and are free standing. Also, most telescoping towers are not designed for
continuous height adjustments so it’s not feasible to run the experiments.
The towers that I have are specially designed to perform these tasks. The
large 118-ft tower at my DX location at the summerhouse is designed to
modify the take off angle for the ideal skip condition. I dont know of any
company offering this tower commercially.




The 100 ft tower on its way




On a lighter note, with a telescoping tower you can let the tower grow on
the neighbor’s say a foot every day HI. Maybe make the hoist system ultra
fast about 1-ms for full up or full down in the trees. You could put a
neighbor sensor on the thing and when they look out the window down it
comes. What tower, what antenna? EH All kidding aside, its interesting to
be able to adjust the take off angle for different areas and times of the
day.




My second 80-ft (24m)-telescoping tower in Ottawa tilts over. This is
fantastic for the initial erection and flexibility for future
modifications. Most importantly, is that initially you don’t have to have a
high profile crane come in. That’s high profile City. Neighbor: You know
when that BIG CRANE came over to your yard and you had the big erection,
well ever since that thing went up my washing machine has been over sudsing!




BAND WIDTHS AT THE HALF POWER




From my experiments the yagis that I constructed had wide low
reflected-power bandwidths that usually cover the entire band with less
than 2 percent reflected power. I am fully aware of the theory that a
narrow bandwidth results in a larger gain factor. However, I seam to have
more than enough gain from my practical experiments and the ability to roam
the entire band with low vswr in very appealing to me. VSWR curves above
1.5 to 1 on my long yagis were usually occurred outside the band on
20-meters. The half power points were awesome at plus or minus < 30
degrees. Half power beam density points are those points that are out to
the sides of the beam pattern and are 3-DB down with reference to the
maximum density of the middle of the beam pattern.




There are certain construction techniques used when building short yagis
that seam to indicate that one can tune either for maximum front to back or
maximum forward gain. Usually, the frontal lobe will be skewed and the
forward gain suffers a little. I should not comment further because I have
real problems relating to antenna things that I have not experienced first
hand. I have always worked with long boom yagis and in this situation one
works both on the front to back and with the focussing of the energy in the
frontal lobe. Elements, far out on the boom, focus the energy. The gain
comes from the missing density from the mods in the rear lobe by the
reflector and the side’s lobes by the directors and more importantly the
long boom. From these experiences, I find it very difficult to separate the
front to back with the forward gain. Again, I feel the forward gain of the
array is directly related to the re-arranged flux density both on the back
and the sides.




THE NEIGHBOR ANXIETY INDEX:




Large antenna arrays are prone to all sorts of problems, not the least, the
anxiety level of all the neighbors. My large telescoping tower with the
stacks is mounted in the trees on the edge of a large lake in eastern
Ontario. This QTH is the highest area in eastern Ontario. About a mile of
water separates my QTH from a large campsite across the bay. I ventured
over their one day and was asked, what do you think that strange structure
is across the bay? The thing is there sometimes, and sometimes it’s not.
WOW! .. Very strange. I said, I thought it was some sort of secret
government installation, an area to be avoided at all costs. When people
bring your antenna system up in conversation, just say thank you, thank
you, and tell them that the thing will protect them from lightening storms,
just my little contribution to the well being of the neighborhood.




Watch for the gun barrels out the windows. Maybe you should only climb the
tower at night in the city.




THE PUBLIC RELATIONS CAPER:




On a more practical note, last year I used my snow blower to clear several
neighbors’ lane ways while they were at work. HI




Start with the popular, Hy-Gain, 204BA, a 4-element Yagi on a 26-ft boom
and double the length to 52-ft, [15.6m]. You should only add one extra
director for a total of 5-elements in this project. (Obviously, I think the
present design of the 204BA is over-populated with elements.) However I
still admire the design of this antenna because it’s a strong competitor on
band. I know this sounds odd but for what it’s worth I think the 204BA is
actually a 3-element beam with an extra director. The first director is a
foot [0.3m] longer than the other directors and is always placed
0.1-wavelength (7-ft) [2.1m], in front of the driven element on 20-m. Some
amateurs have called it the phantom element. I use this odd, close-coupled,
over size, director design on all my yagis and feel that the results are
really worthwhile.




The spacing on the 205GK, 5-element were, starting from reflector end:
12-ft [3.6m], 7-ft [2.1m], 15-ft [4.5m], and 18-ft [5.4m]. The element
lengths stay the same as the 204BA and the last director is 2 inches [5cm]
shorter than the one before it. I also substituted an OMEGA match for the
original 204BA-matching network. Complete details are in another chapter.
Wait until you try this new super 205GK modification to make the 204BA into
a 5-element on a 52-ft [15.6m] boom. This antenna will astound you. You can
throw out the theoretical 2-DBP-gain figure. It seemed most of the time to
be around two S units. I remember a five element made by a well-known beam
manufacturer on a 46-ft boom that outperformed their 6-element on the same
boom. However, the company made the 6-element available for those who
wished to say they were running six elements. Some beams have several
driven elements to cover the bandwidth. My long yagis designs cover the
whole band with lots to spare, more later. I understand that the antennas
should work better at some point in the band, but I don’t see any change in
performance over the entire band. Five element yagis were a passion of mine
in the 70`s and 80`s and I built several of them. The largest one was on a
53-ft (17.6m) boom. I also built a 7-element on the 63-ft (21m) boom, and
fun learning project. I know, I know, 7-elements on this length of boom was
too crowded, the boom should have been about 100-feet [30m] long, but you
learn as you go. I describe these home brew beams in other chapters.




THE THREE ELEMENT YAGI:




I have to say that I have never had any real success with a 3-element yagis
design. Oh, I got them to work but they didn’t have that magic touch in a
crowd, even when I stacked them. I think all mono-band beams need the magic
short-coupled first director, so there has to be a minimum of 4-elements.
So I guess the three-element beam for 20 meters is not in the big game.
Remember if you don’t agree with my observations turn the dial, HI. From my
point of view, the 4-element single band is the most popular competitive
beam in use today on 20-meters.




DO NOT READ THIS PARAGRAPH:




You know it appears to me a lot of people are just relying on other
so-called experts to do they’re experimenting for them. Some of the gain
figures are really inflated as far as my experiments dictate. I hear that
there is a magic 2-element on 20 meters on an 18-ft boom, crowded with
other bands, that has a 10-DBD + gain figure. Must be some magic here.
Think about it, would operating 100 watts to the thing be the same as
running 1100 watts to a dipole in the same spot? NOT!!!!!!!




Let me run your design by my computer program and see if it’s a good
design. This is right after I have broken a force 10 or 12 pile-up with 200
watts bare foot on the first call into Asia. No, you run your program by my
design and see if it measures up.




Because of gusty winds and heavy ice in some areas, the life expectancy of
large beams is short. The big guys require special towers and extra special
rotating systems. I used to rotate the big beams with long drive tubes with
the rotator mounted at the base of the tower at ground level. Steel wires
ran down the side of the tower to show the beam heading independent of the
backlash of the long tube. The main reason for the tube was to eliminate
the need for the tower to handle the severe torque power from the long
booms in heavy winds. Is it ever neat to be able to get at the rotator at
ground level, especially in the dead of winter? As an added torque
absorber, I over-lapped two diameters of the torque tube just above the
rotator. Then I welded a large automobile front-end suspension coil spring
onto each tube so that the spring was in series with the drive system. This
spring idea came from Gib, VE3BGX in Ottawa.




Special rotators had to be designed for the new rotating towers. One design
used four VEE belts in parallel. (I think this was the best design).
However, the belts had a short life span because of the proximity to oil
and grease. Because the tower had to be lifted out by crane in order to
change the belts, a second method was designed using small diameter steel
cable. The cable design was not unlike the winch method mounted on its
side. This is the method I use at present on the large tower. The smaller
1.5 ton tower uses a new design using a linear drive consisting of a 30
inch, [75CM], 3/4, [2-CM] inch diameter, 10 turns per inch threaded rod
driven by a one third horse power electric motor. This new design does not
require an expensive gearbox reduction drive assembly. Also this rotator
could be located at ground level and drive cables could run several hundred
feet to the top of the tower. This cable rotating method also relieves the
tower of any responsibility for torque restraint. A heavy-duty relief
spring is installed in series with the drive cable to relieve any bumps in
torque due to gusting winds. The rotator has more than enough power to
rotate the largest 80-M beam -tower at a fraction of the cost. There are no
expensive gears to strip and the unit is self-braking. A triangle tower
could be rotated this way quite easily because the wire winch drive can’t
tell the difference between rotating a circle or a triangle. One would have
to re-calibrate the beam indicator because of the difference in the
diameter from the point of the triangle to the side of the triangle. The
other option would have steel drum welded to the tower so that the radius
of the tower remain constant.




THE NEW ERA OF THE SHORT BOOM YAGI ANTENNA.. MAGIC GAIN ANTENNAS?




Don’t let anybody claim they have a magic antenna on a shortened boom, with
less elements, that works as good as or better than a longer one because
they are just fooling themselves and trying to fool you. Logic dictates
that a boom with other elements for other bands on it will not work as well
as a boom dedicated to one band.




THE BRONTOSAURUS GUN:




REMEMBER..Combine the gain from several long boom yagis in the stacked
array and you have a real brontosaurus gun.




My brontosaurs gun the 7 element on the 68-ft boom at 90 ft

The post Stacked Yagi Antennas appeared first on IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
Ameritron AL-80A restoration project

Posted: 03 May 2020 01:39 AM PDT
http://www.iw5edi.com/ham-radio/4325/ameritron-al-80a-restoration-project



W7TDC article on restoration of the AL-80A RF amplifier.




The Ameritron AL-80A uses a single 3-500Z triode to produce over 1KW of
power with only 65 watts of drive.





I purchased it in the beggining of July 2003. It had several problems when
I got it. The tube was bad, a VHF parastitic had occurred, causing several
components to fail. As far as mechanically, there was only one problem. The
plate tuning capacitor has a plastic coupler that connects it to the knob.
This coupler was cracked were it slipped over the capacitor rod, allowing
it to slip.




What is a VHF Parasitic? This is when a VHF voltage causes an self-resonant
fly-wheel type occilation in the tube. When this happens, all hell beaks
loose and many things make a day turn bad. There are two things that need
to be done to solve this problem. First, the Q of the VHF self-resonant
circuit needs to be reduced, and to reduce the VHF voltage-gain of the
amplifier stage. To solve this problem so that a parasitic is less likely
to occur, the anode and cothode self resonant frequencies need to be
farther apart by reducing inductive reactance. This is done by shortening
lead length and tuning it out by bypassing the grid to the chassies by
using small capacitors. This increases the self-resonant frequency of the
grid circuit to point where the tube will have less amplifing and
osccilation ability.




Below is a list of all the things I did to the amplifier with an
explanation.




1) Replace the VHF Parasitic Supressor
2) Add a step-start circuit
3) Add an additional capacitor to the anode choke
4) Add fast T/R switching
5) Adjust filament voltage to 4.8VAC
6) Add diodes across meter shunt resistors for glitch protection
7 ) Add rectifiers across HV filter caps.
8 ) Replaced the cathode bias zener dipode with several rectifiers.




1* I replaced the original VHF parasitic supressor which was a 100ohm
resistor with a inductor around it, with Nichrome wire and two 100ohm
resistors in parallel. The Nichome wire has an extremely small amount of
resistance and handles large current and voltage being close to 22AGW.




2* The step-start circuit I added used a simple 10A 120VAC DPDT relay and 2
25ohm 10watt resistors.
Current went through the resistor and after about 1 second the voltage was
high enough for the transformer to produce 120V. This closed the relay
contacts allowing current to bypass the resistors. This simply protects the
circuity and especially the filament from voltag skikes and current inrush.




3* The original capacitor was .001uF 7.5V. I added another capacitor to
make it 10pf.




4* Even though I dont do QSK often I do use Vox during the heat of a
contest. The amplier does switch to transmit pretty fast when I key down.
Thats not really the issue. The issue, is that the T/R relay is hot
switching. In other words, the radio is keying down and putting power out
before the amp relay can even think about switching the relay. So the amp
relay is switching while 100 watts is on it, which is very bad for the
contacts. You can tell by seeing a SWR spike when you first key down. To
fix this, I made an entire new circuit board that not only contained the
fast T/R switching, but the electronic cathode bias switching also. There
are two different relays for the fast T/R switching. One input and output.
The output relay is a high speen Kilovac HC-1 vacuum relay, while the input
relay is a RF reed-relay. This will insure that when the tranceiver Xmit is
brought to ground, the amp will switch the relays before power is put
through it.




5* One of the most important things is filament voltage. A 3-500Z has a
minimum of 4.8V with a max of 5VAC. If there is a 3% increase above 5VAC,
it will decrease the life of the tube by one half. I measured the voltage
of mine and it was 5.2volts, which is way to high. I replaced the filament
wire with 24AGW and added some resistive wire to one end. Using smaller
wire is much easier then trying to find a .25ohm resistor. This brought it
down to a perfect 4.8VAC. Even worse than 3% higher voltage is a under
voltage. That will literally kill the tube in a very very short time.




6* If there is ever a glitch, where the HV arcs to ground, the meters will
be blown out of the panel. I added some 200A PIV diodes across the meter
leads to that they would be destroyed rather than the meters.




7* The next thing I did was add rectifiers across each HV filter cap.
Electrolytic caps are detroyed very easily be a reverse voltage, especially
that high. So if the HV were to ever arc to ground, the diodes would be
destroyed while the capacitors are beeing nicly bled down by their
resistors.




8* The next thing to do was replace the 7.5V 10watt cathode bias zener
diode with a string of rectifiers in the foreward operating position. This
not only allows adjustment to 75mA of plate current wich is optimum, but
also helps retain 5v of cathode bias voltage. My fast T/R circuit contains
a transistor used as a switch to auto switch the bias when transmitting.

The post Ameritron AL-80A restoration project appeared first on IW5EDI
Simone - Ham-Radio.


///////////////////////////////////////////
WinPSKse

Posted: 03 May 2020 01:36 AM PDT
http://www.iw5edi.com/ham-radio/4322/winpskse



This free application developed by KA1DT is no more developped but still
offer interesting features and is just 970Kb.








Download WinPSKse v 2.23 

The post WinPSKse appeared first on IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
AM Antennas

Posted: 03 May 2020 01:34 AM PDT
http://www.iw5edi.com/ham-radio/4319/am-antennas













An AM loop antenna is one of the true marvels of electronics. Requiring no
power, it takes advantage of the resonant properties of an
inductor and a capacitor connected in parallel to receive weak AM stations.
The loop part of the antenna is the inductor, and the
tuning capacitor makes it resonate at a desired frequency.



AM_loop_antennasDownload

The post AM Antennas appeared first on IW5EDI Simone - Ham-Radio.


///////////////////////////////////////////
Kenwood Smart Memory KSM

Posted: 03 May 2020 01:30 AM PDT
http://www.iw5edi.com/ham-radio/4315/kenwood-smart-memory-ksm



KSM Kenwood Smart Memory is a program to read and update the memory
channels of a Kenwood amateur radio.




The current supported types are: TS-450S, TS-570D, TS-570S, TS-690S,
TS-870S, TS-940S,TS-950S.








Software by PP1ETL has changed various download sites during years.




Kenwood radio memory manager software to manage kenwood radios memories can
now be Downloaded from here

The post Kenwood Smart Memory KSM appeared first on IW5EDI Simone -
Ham-Radio.