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KN5L EFHW Unun

 

Hi Allison,

The quest was an 80 to 10 Meter Unun. Correct, for 20M and higher
frequency, 61 material can be used with reduced loss. Similar stack of
two FT114-61 with four turn primary, about 2.4uH, will result with
approximately 0.04 dB loss at 14 MHz, as shown in:


John KN5L

On 6/16/19 12:55 PM, ajparent1/kb1gmx wrote:
For the 14mhz model, try using mu 125 material (FT240-61)
as you getting near the point with hard ferrites (31 and 43)
where their absorption properties are becoming significant.
ajparent1/kb1gmx
 

John,

I was aware of that. I have such an antenna, of good utility but for
trying to get an specific area on a given band I go to mono-band
antenna as the pattern is predictable even if the peak gain is lower.
The side effect is not transformer loss, it is that the direction I want to
work on 15 and 10 in my case is only broadside to the wire and that
is not a strong direction due to pattern. Hence the monobands.

Generally I always ask the person why 80-10 and often the answer is
"because I can't fit 160 -10" and often the user rarely uses more than
two maybe three bands. Its a curious thing to me.

The work your doing show how to optimize the transformer for all
band use is a good thing many do not understand where and why.
It also highlights one area of compromise that antennas for too
many bands may suffer. For those wishing to get optimal results
on a narrower set of bands a pair of transformers for 80 and 40
plus tricks to get 60 or 30 in the wire and a separate for 20 through
10 and maybe the intermediate bands as well.

Allison
 

Different operators have different goals. An operator who is trying to
minimize equipment weight, like KD1JV during his walks of the
Appalachian Trail, might prefer to carry just one antenna. (Steve also
designs ultra lightweight and ultra low power radios for that type of
operation to keep his pack weight down.) In that type of operation you
often have no choice in how to orient your antenna in any case because
the supply of suitable antenna supports such as trees is limited, so
antenna pattern is a secondary consideration. Low dipoles aren't very
directional in any case, and on the higher frequency bands you just
take what you get.

One wire trick I like is the removable jumper scheme used in PAR's
EFT-MTR multi-band antenna. It has a little stub with an SMA connector
on it that you can remove to shorten the wire. (The short coax stub
really just serves to make it a bit larger so you don't lose the
jumper, and give you something to grab.) So a 40m EFHW also serves on
20 using second harmonic operation, and on 30 by removing the jumper
to shorten the wire.

For the ham who is willing to carry a bit more gear, I like your idea
of separate antennas for the higher and lower bands.

On Sun, Jun 16, 2019 at 6:45 PM ajparent1/kb1gmx <kb1gmx@...> wrote:

John,

I was aware of that. I have such an antenna, of good utility but for
trying to get an specific area on a given band I go to mono-band
antenna as the pattern is predictable even if the peak gain is lower.
The side effect is not transformer loss, it is that the direction I want to
work on 15 and 10 in my case is only broadside to the wire and that
is not a strong direction due to pattern. Hence the monobands.

Generally I always ask the person why 80-10 and often the answer is
"because I can't fit 160 -10" and often the user rarely uses more than
two maybe three bands. Its a curious thing to me.

The work your doing show how to optimize the transformer for all
band use is a good thing many do not understand where and why.
It also highlights one area of compromise that antennas for too
many bands may suffer. For those wishing to get optimal results
on a narrower set of bands a pair of transformers for 80 and 40
plus tricks to get 60 or 30 in the wire and a separate for 20 through
10 and maybe the intermediate bands as well.

Allison
ajparent1/kb1gmx
 

Shirley.

I know Steve being a SB1/II builder and just about every one of his test
gear and digital dial bits over the last 15 or more years. He designs
really slick radios.

I have two of the PAR EF40/20/10s. I have them setup with stackable
wires for any band from 60M through 10M. I found some connectors
that are like spade lugs but they latch into each other in a hook like
way so the don't pull apart. I have to find more of them. Killer for
segmented wires. Usually used for 40 or 20M in my case so one
wire does it.

The idea of multiple antennas is not a killer for portable as often many
bands are unsuitable for the next few years or not a best choice.
The 10M antenna weighs in as fairly light (3.7 oz with the antenna
wire) but If I'd used a BNC connector and a QRP sized coil it would
be very light. I was thinking of FD and back yard use not packing it.
At the QRP power level I've gotten under 1oz for the box and the
wire can be very light as well (#26 Polystealth at .38 pounds per
1000ft ). After all I think in terms of .050 braided nylon cord
for hanging wires for temporary use as I often change and add
antennas here. Reality is often the antenna can be the lighter
part of the radio kit.

I also understand light weight. Usually the trail friendly radios are not
FT817 DC to daylight radios and typically 1 to 3 bands so a 80-10
antenna makes for much extra weight. I've watched people try and
get a 80M antenna up and mostly not succeed when the highest
thing around is maybe a 15ft high rock. Dense wooded areas
present challenges as well, its the branches in the way. Biggest
issue is an antenna that is viable on a hilltop with 25mpg gusts
and not a tree in sight.

I feel that's even more divergent from Johns work here as he is
working on Baluns and transformers that don't melt at 100 to
QRO power levels. A pair of FT240-43 are not light when put
in a Polycarbonate box. At QRP levels the problem is
manageable and the losses can be kept down. Its a big
part of the considerations that go into matching the radio
to whatever antenna..

That and I'm likely one of the few that does things like run 10M
and do DX country hunting at the bottom of the solar cycle when
everyone else feels 20 is dead for DX. ;) I chalk it up to my
many years of VHF/uhf commercial work and my affinity to
VHF and UHF. That and I tend to favor phone(SSB) so
some bands like 30M are not my tea and digtial modes
means dragging a computer of some form.

However with that, going to the field with a portable radio
weight is a big factor, and the bands most likely to get contacts
typically have been 40 and 20. An 80M antenna is big and
daytime absorption is high and bands above 20 and likely to
be the level of sketchy most want to take on. So 60-20M
are the likely ones.

FYI: my favorite antenna for odd cases on the 160 and 80/75M
bands is the Grasswire, lossy and long at about 130ft but
universal rubber duck for HF and flat places. With the
transformer its under a half pound mostly for the ferrite.

Allison
 

Allison:

I think you are referring to "KNIFE DISCONNECTS" used in aviation.
They take a heavy pull load without disconnecting.
Quick and easy disconnect with a 90 degree rotation of the terminal.
If you slide a clear piece of spaghetti insulation over the connection,
there is no way it will come apart in the wind.



--- Graham / KE9H

On Sun, Jun 16, 2019 at 9:33 PM ajparent1/kb1gmx <kb1gmx@...> wrote:

Shirley.

I know Steve being a SB1/II builder and just about every one of his test
gear and digital dial bits over the last 15 or more years. He designs
really slick radios.

I have two of the PAR EF40/20/10s. I have them setup with stackable
wires for any band from 60M through 10M. I found some connectors
that are like spade lugs but they latch into each other in a hook like
way so the don't pull apart. I have to find more of them. Killer for
segmented wires. Usually used for 40 or 20M in my case so one
wire does it.

The idea of multiple antennas is not a killer for portable as often many
bands are unsuitable for the next few years or not a best choice.
The 10M antenna weighs in as fairly light (3.7 oz with the antenna
wire) but If I'd used a BNC connector and a QRP sized coil it would
be very light. I was thinking of FD and back yard use not packing it.
At the QRP power level I've gotten under 1oz for the box and the
wire can be very light as well (#26 Polystealth at .38 pounds per
1000ft ). After all I think in terms of .050 braided nylon cord
for hanging wires for temporary use as I often change and add
antennas here. Reality is often the antenna can be the lighter
part of the radio kit.

I also understand light weight. Usually the trail friendly radios are not
FT817 DC to daylight radios and typically 1 to 3 bands so a 80-10
antenna makes for much extra weight. I've watched people try and
get a 80M antenna up and mostly not succeed when the highest
thing around is maybe a 15ft high rock. Dense wooded areas
present challenges as well, its the branches in the way. Biggest
issue is an antenna that is viable on a hilltop with 25mpg gusts
and not a tree in sight.

I feel that's even more divergent from Johns work here as he is
working on Baluns and transformers that don't melt at 100 to
QRO power levels. A pair of FT240-43 are not light when put
in a Polycarbonate box. At QRP levels the problem is
manageable and the losses can be kept down. Its a big
part of the considerations that go into matching the radio
to whatever antenna..

That and I'm likely one of the few that does things like run 10M
and do DX country hunting at the bottom of the solar cycle when
everyone else feels 20 is dead for DX. ;) I chalk it up to my
many years of VHF/uhf commercial work and my affinity to
VHF and UHF. That and I tend to favor phone(SSB) so
some bands like 30M are not my tea and digtial modes
means dragging a computer of some form.

However with that, going to the field with a portable radio
weight is a big factor, and the bands most likely to get contacts
typically have been 40 and 20. An 80M antenna is big and
daytime absorption is high and bands above 20 and likely to
be the level of sketchy most want to take on. So 60-20M
are the likely ones.

FYI: my favorite antenna for odd cases on the 160 and 80/75M
bands is the Grasswire, lossy and long at about 130ft but
universal rubber duck for HF and flat places. With the
transformer its under a half pound mostly for the ferrite.

Allison
 

Hi Allison,

On 6/16/19 9:33 PM, ajparent1/kb1gmx wrote:
I feel that's even more divergent from Johns work here as he is
working on Baluns and transformers that don't melt at 100 to
QRO power levels. A pair of FT240-43 are not light when put
in a Polycarbonate box. At QRP levels the problem is
manageable and the losses can be kept down. Its a big
part of the considerations that go into matching the radio
to whatever antenna..
Very correct. The design I've suggested is using two FT114-43 cores, not
2.4" cores. The Selection was a compromise between size and loss,
attempting to keep core loss below 0.3 dB for a QRP 80M to 10M device. A
single FT114A-43 could be used with just slightly greater loss. I had
114's in my inventory.

Selecting a -43 core and turn count based on core loss can be performed
using:

Examples:
FT82-43 4T primary 7.5uH @ mi -> ~0.7dB core loss
FT82-43 3T primary 4.2uH @ mi -> ~1.1dB core loss
FT82-43 2T primary 1.9uH @ mi -> ~2dB core loss

John KN5L
ajparent1/kb1gmx
 

Graham,

Thank you, I had to go back to my aircraft maintenace logs to
find the part name and source I used. I are a pilot and aircraft
owner. And Aircraft Spruce has acquired many of my AMUs
(aircraft maintenance units, they come in increments of 1000$)
over the years. ;)

John,
What might help if you can find a ferrite with a Mu of 400ish
(lower than 43 and higher than 61) and that exists but
I haven't used it in toroid form (it was bars for the task).

Either way there is a trade for Ampere-turns, core loss
Vs working inductance and total turns on the core. The
range that works for a decade frequency range is fairly
narrow as you've shown.

Allison
 

I wonder what would be the optimum UNUN (lowest losses) for 40m-20m end fed? That is the frequency range for a trail antenna nowadays due to solar minimum.
 

On 6/18/19 2:18 AM, Vojtech Bubnik wrote:
I wonder what would be the optimum UNUN (lowest losses) for 40m-20m end fed? That is the frequency range for a trail antenna nowadays due to solar minimum.
Hi Vojtech, Good Question, and SimSmith to the rescue!

Evaluating 4T FT114A 61 and 43 material for critical low frequency
inductance and core loss:



The first plot evaluates mismatched loss for evaluation where inductance
causes a mismatch. Note SWR curve for 61 material, light blue trace, is
below 1.5 at 7 MHz.

Second plot evaluates core loss using a matched source. Note 61 material
has significantly reduced loss from 43 material.

John KN5L
 

Graham,
Thanks, I picked up a box of the red ones at a hamfest and always wondered what they were called.They work well on my QRP EFHW antennas to add/subtract a 1/2 section of wire.
73 - Dave, N4ELM
ajparent1/kb1gmx
 

For a lot of common ferrites and iron powder toroids are color coded and
researchable.

RED toroids are generally -2 material (iron powder) Mu of about 9-10.
They are good for low loss tuned circuits and some transformer formats.

You can get the specification by measuring OD, ID and comparing to known
parts listed at Kitsandparts.com or other sources.

Allison
ajparent1/kb1gmx
 

Knife disconnects...

Definitely the winner for antennas. I found that the right size shrink tubing
was handy as the sleeve. The right size is one that does not shrink tight
to the wire and can slide, shrink one side and its slide over the connector.
The thick wall type of shrink works well.

Found my supply in 4 colors and two sizes at that. I thought I'd used
them up but at the time I bought boxes of 100. Never thought to look
for them in the aircraft material storage to replenish the crimp kit.

Allison

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