Thanks Jack,
Long answers are good and indicate your willingness for full
disclosure.
(Manufactures antenna specifications tend to be BS generators?
Second only to the HiFi industry.??
Remember the kids in the mid 1980's with their "Ghetto Blasters"
advertised with 780 Watts of stereo music power, and all from 8X D
cell batteries.
In fairness some of the manufactures provided revised figures when
used on mains power, nearly a KW.
Man those things must have being efficient, and all through a skinny
power cord....)
I couldn't find on the pacciffic66 site what
they reference
their figures to, on that initial page at least?
hopefully it's something real and not against some theoretical
property.
One of which, the proper name escapes me at this time.
(my numbers for instance :-)
6ft of wire whether straight or coiled is a larger percentage nearer
a useful wavelength ie: 1/4wave?? at say 28MHz (approx 8ft) than the
same 6ft of wire to 14MHz
I interpret this to It's a simple expression of comparison of
physical length to wavelength, nothing to do with the antenna
efficiency and devoid of losses in the matching networks that are
necessary, etc, etc.
Even if it's a real antenna they are referencing it to, it in it's
self could be a compromised reference gives great headline numbers.
Check the fine print!
Suggestion:- At least do the theoretical model of what ever you
choose to use as the loop reference antenna against a full size
centre fed dipole at identical heights, even if not a real world
test.
Granted it's monoband & optimally performs mounted half
wavelength above the ground but it's a good indicator &
reference, and as cheap & simple?? to construct as it gets.
if you don't like what you see in the comparison it's between you
and your conscience.
You can cripple it's performance and justifiably conclude an XYZ
antenna, is greatly more efficient than?? a halfwave dipole when
mounted at 15ft agl for example....
:-)
Saw the reports of doing A/B comparisons, however quick the
changeover there is always the element of doubt as to propagation.
the ideal is simultaneous TX to both antennas in the same lot but
far enough not to interact is the goal.
In the real world two antennas one each in the same town is good
enough. What's a mile over a propagation distance of say 6,000??
everyone has their preferred mode, be it CW, WSPR the latest
digimode.???? Reality it doesn't matter?
The requirement is for as many & widespread coverage of
receiving stations as possible??
That said, QRP-Labs kits are cheap enough to utilise two, and
compare like for like WSPR time slots to each of your and AL's
callsigns allocated to each different antenna?
regards Alan
On 01/06/2019 17:27, Jack Purdum via
Groups.Io wrote:
toggle quoted message
Show quoted text
Alan:
The results right now are modeled using the usual Pacific66
app. However, we do plan "real" tests in an attempt to get
some useful data. Our reference antenna will likely be an
80-10M EFHW which we both use. Al also has a vertical that we
might test against. However, the EFHW is always available; not
so with the vertical.
We read in a paper that someone added a ground plane and
said it "made a difference", whatever the hell that means.
Anyway, because of that, we want to try it and see if it does
have an impact. We have already noticed that the shape of the
feed loop makes a difference, as does its position in the
vertical plane. The effect is small, but real.
Al and I have talked about this a lot, and our feeling is
to publish the results of the "Double-Double" as a
construction article. (I want to call it the "Luggable
Double-Double" but Al's not happy with that.) There are
controllers out there (Loftur Jonasson) so my feeling is that
will be kept for the book only. Also, it will be somewhat
unique in that we hope to add a TFT display that shows the SWR
in realtime as a plot. We have arranged to have all of the
projects' PCB's available at a reasonable price.
Al and I are writing the book in a strange way. We are
going to finish it before signing with a publisher. The reason
is because I know the time pressures that editors put on
authors with respect to deadlines and we want to get this
right rather than to market fast. Our TOC has 18 chapters, of
which the first 4 are really setting up the software for the
Arduino, Teensy, STM32, and ESP32 ??C's and giving the
beginning reader enough C instruction to read our code (and
shoot themselves in the foot a few times?) We see 12 projects
in the book, some of which (e.g., the ML) are two
chapters--construction and software. Some are "end products"
(e.g., the ML, a different antenna tuner, CW messenger, CW
decoder, CW Tutor) while others are test equipment (e.g.,
programmable power supply, AC voltmeter, signal generator).
The last chapter is on using what you've built to troubleshoot
a receiver. We think it will be a very unusual, but useful,
book. Our goal is to have it done by the fall. We currently
have 9 chapters done.
Long answer to a short question...
Jack, W8TEE
On Saturday, June 1, 2019, 12:01:46 PM EDT, Alan de
G1FXB via Groups.Io
<g1fxb@...>
wrote:
Hi Jack,
Sounds like you are on to something special with 90% and
even the 40% are impressive figures.
(Noted that they are modelled?? efficiencies at this
point in time, here's hoping with can you can achieve
something approaching in practical tests.)
To what reference antenna (also at the same modelled
height to compare like for like) ?
Interested in your comment the trials of a counterpoise,
Previous papers indicate loop type antennas were
considered a free space antenna requiring no ground
plane / radials
I guess it's the feed / matching & counterpoise is
where the magic happens?
As it's using an auto tuner is the write-up destined for
your new book is there an ETA, or another perhaps
magazine article release?
(One gotcha about some of the previous, (not your) small
"miracle" antenna's.
Check it's actual the antenna doing the radiating and
not the feed line, or counterpoise even the mounting
pole has being known to be "accidentality" hot with RF.
(However disguised, generally any antenna employing a
braid breaker / balun in the coax away from what they
make you believe is the feed point or suggested feeder
or support lengths perhaps warrants a second look.))
regards Alan
On
31/05/2019 18:45, Jack Purdum via Groups.Io wrote:
We are also trying to assess other factors, too,
such as a counterpoise and its affect on
performance. We may find that these "other factors"
play no significant role in the antenna's
performance. Still, learning that something doesn't
matter is as helpful as learning what does matter.
Jack, W8TEE
Alan de G1FXB