Make your own T2FD
Kees
More info to make a T2FD yourself, like I did mine, please have a
look at:
http://members.home.nl/rita.kees/t2fdmake.html
I hope you can appreciate it and use it for your practice.
I will be glad to answer your questions.
73/cheers
Kees
m II
http://members.home.nl/rita.kees/t2fd1.gif
I found that my garage is WAY to far away to use this setup.
Following the formula, I took an average frequency of 10 Megahertz. I
divided into 100, as per the formula. I got an antenna length of
(100ft/10,000,000) = 1 X 10^-5 feet, or 0.00012 inches.
I then thought that this just couldn't be right. I redid it using Meters
instead of feet and arrived at 0.00001 meters length. MUCH BETTER! The
problem now is that the store only sells full length rolls of wire.
Where can I mail order a smaller chunk? Can they just wrap the postage
stamp around it to save shipping costs?
Being ever on the watch for cheap alternatives, what is a cheap way of
relocating the far end antenna support?
I don't want to pay to have the garage moved.
Any insights appreciated.
mike
--
__ __ __ __ __ __ __ __
/ /\ / /\ / /\ / /\ / /\ / /\ / /\ / /
/ /\ \/ /\ ohmwork...@spots.ca \/ /\ \/ /
/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/
..let the cat out to reply..
ŠDensa International
'Think tanks cleaned cheap'
G.Beat
news:aelbd0pvdvu6rv64t...@4ax.com...
The Tilted Terminated Folded Dipole ("T2FD") is a broadband folded dipole
antenna design that provides a relatively
stable feed point impedance over about a five to one frequency range. The
antenna
length in meters is approximately 100 divided by the lowest desired
operating
frequency in megahertz. The upper element of the folded dipole is opened in
the
center and a non-inductive terminating resistor of around 350-400 ohms is
inserted.
The bottom element is fed in the center through a 6-to-1 balun for a good
match to
50 ohm feed line.
The antenna is not as efficient as a matched half wave dipole at any
specific
frequency, but it also does not require an antenna tuner for operation,
making it
easy to use. The loss of receiving efficiency is not generally noticeable
in the high frequency range (2-30 MHz), amounting to less than 6 db (one
standard
S-unit) during extensive on-the-air testing.
Here is additional information on the T2FD antenna.
Barker & Williamson actually applied for a US patent (US Patent #4423423)
for their specific T2FD antenna design.
http://www.fact-index.com/t/t2/t2fd_antenna.html
While this may be acceptable for SWL operation, the resistor does not have
sufficient wattage for
any station attempting to use this for a transmitting antenna.
http://www.tuberadio.com/tfd.html
http://www.universal-radio.com/catalog/sw_ant/0562.html
w9gb
Hans
or horsepower
Hans
m II
> In physics always use meters, kilograms, joules and not inches, pounds
> or horsepower
Of course. Sorry about my retrograde calculations, however, the numbers
provided on the site need to be clarified, as they don't work either in
either method.
An example at the bottom of the page using the proper units would be in
order. The confusion is what caused me to post to begin with.
100 anything divided by millions of other units is bound to cause very
small numbers and in this case very small numbers give birds no place to
perch.
mike
RHF
= = = news:<UdtBc.152030$Ly.30888@attbi_s01>...
W9GB,
B&W makes two general statements about the T2FD:
* For example, an {T2FD} Antenna for the lower portion of
Shortwave (3 - 18 MHz) will be roughly 33m (110 feet) long,
with conductors spaced 1m (3.3 feet).
[With a Top End mounted about 60 Feet High at 30 Degrees.]
* In order to cover the higher portion of Shortwave (5 - 30 MHz),
this {T2FD} Antenna will be roughly 20m (66 feet) long,
with a spacing of 60 cm (24 inches).
[With a Top End mounted about 40 Feet High at 30 Degrees.]
Build one size or the other = No Formula Required.
Read: T2FD Antenna - WOW ! ! ! {One SWL's Experiance}
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/293
iane ~ RHF
.
.
>
> While this may be acceptable for SWL operation, the resistor does not have
> sufficient wattage for
> any station attempting to use this for a transmitting antenna.
> http://www.tuberadio.com/tfd.html
>
> http://www.universal-radio.com/catalog/sw_ant/0562.html
>
>
> w9gb
.
Jim Haynes
T2FD antenna suggests that an equally-long dipole would give good results
across the frequency spectrum if used with an antenna tuner. What the
T2FD really buys you is the ability to avoid an antenna tuner.
There is an amateur antenna out there consisting of an 80-meter dipole
(I mean one that is a half wave at 80 meters, not one physically 80 meters
long) fed with about 100 feet of 450 ohm ladder line. It turns out that
100 feet of line is within about 10% of the idea length to match the
antenna to 50 ohms on all amateur bands. One design of this antenna uses
a tuner to correct for the mismatch, while another uses various lengths
of 450 ohm line added to the feedline to achieve a match.
--
jhhaynes at earthlink dot net
Tam/WB2TT
reisistor is very complicated. May I suggest:
Connect the two wires to a normal dog-bone insulator, and solder the
resistor across the insulator to the two wires. Insulate if you wish. For
receive only, a 1/2 W resistor is as good, or better.
Tam/WB2TT
JGBOYLES
>reisistor is very complicated. May I suggest:
Hi Tam, For receive only, a doublet antenna, as high as possible, with 50
ohm,or 75, or 300 ohm feedline will work well. I have no idea why people want
to complicate receive antennas with resistors. Do you?
73 Gary N4AST
Tam/WB2TT
"JGBOYLES" <jgbo...@aol.com> wrote in message
news:20040621183246...@mb-m28.aol.com...
Hi Gary,
I use my 75 m antenna, which tops out at 70 feet for SWL listening. For 99%
of SWL listeners the limiting things are the poor IF filtering and overload
prone front ends. Also, I dont think you see a noise blanker in a sub $300
radio.
Tam
M1LCR
after carrying out experiments using terminating resistors. Numerous
variations have appeared over the years, usually accompanied by warnings
that as a transmitting aperiodic multiband antenna, its performance may
leave something to be desired. This is because the transmitting power may be
wasted in the terminating resistor.
As mentioned previously the antenna developed from US Naval experiments to
broaden the bandwidth of a folded dipole to a reasonable degree. The was
first described publicly in 1949, after Navy Captain C.L. Countryman tested
it for long periods in California during WWII. The T2FD (also known as a
tilted, centre fed, terminated, folded dipole) can offer claimed gains of
4-6dB over a dipole, depending on the frequency, although 1-3dB is nearer
the mark with some frequencies exhibiting 1dB, as the resistor absorbs the
RF power in transmission. The main attraction of the T2FD is not its gain
however; it's its broadbandedness. It was, and still is, being publicized
in journals as a broadband aerial suitable for use between 3.5 and 28 Mhz.
In addition the T2FD has some attractive properties in terms of noise
reduction, which some long wires / dipoles and ATU combinations are
susceptible too.
In addition the T2FD can be used at higher frequencies than its design
frequency. Some sources claim that it can be used over a range of 5 or even
6:1, although my own observations indicate 4:1. None the less a 40-meter
version will cover 7Mhz to 25 Mhz, with some useful performance up into the
27 Mhz CB band.
See http://www.gb4iom.co.uk/new_page_4.htm for more information.
73
Adrian
M1LCR
"Kees" <PA8...@home.removeee-thisss.nl> wrote in message
news:aelbd0pvdvu6rv64t...@4ax.com...
RHF
= = = news:<Ke2dnTic5aZ...@comcast.com>...
WB2TT - Simplier is better ~ RHF
.
yea right
> between 3.5 and 28 Mhz. In addition the T2FD has some attractive
> properties in terms of noise reduction, which some long wires / dipoles
> and ATU combinations are susceptible too.
>
I live in a suburb. My dipoles and long wires had so much noise that I
hardly ever would listen to HF. Once I read about the noise immunity
provided by a T2FD antenna, I constructed one to try. It was the best
thing I could have done! It made HF livable in my high noise urban
environment. I almost don't notice the noise I had before. I am able to
pick up signals that my neighbor with a tri-band 3 element yagi is unable
to hear due to his noise.
I would recommend this design to anyone combating local QRM.
Kees
That's indeed what it is:
a very low-noise antenna.
Look at : http://members.home.nl/rita.kees/t2fdmake.html
for my "version ".
adddress@spamfree.com CW
only antenna on this newsgroup, there are always many responses saying to
just put up a piece of wire and run it strait to your radio. That will work,
assuming that you live out in the middle of nowhere, have no neighbors and
have no electrical appliances. For the rest of us, noise is a consideration
and more thought needs to be put into an antenna system.
"Kees" <PA8...@home.removeee-thisss.nl> wrote in message
news:lbfjd09u1bo8pbuhg...@4ax.com...
Uncle Peter
"CW" <no adddress@spam free.com> wrote in message
news:ANWdnS-vW_T...@comcast.com...
> Yes, that is an advantage. Everytime someone asks a question about a
receive
> only antenna on this newsgroup, there are always many responses saying to
> just put up a piece of wire and run it strait to your radio. That will
work,
> assuming that you live out in the middle of nowhere, have no neighbors and
> have no electrical appliances. For the rest of us, noise is a
consideration
> and more thought needs to be put into an antenna system.
>
How does the antenna differentiate between "noise" and a valid signal?
(Perhaps these are going to be the solution to BPL.)
Pete
Telamon
" Uncle Peter" <radiocon...@cox.netSPAM> wrote:
Antennas are not intelligent agents able to differentiate between noise
and a broadcast signal. If the noise signal is generated a long
distance from the antenna it will be received right along with
broadcast signals. The only advantage some antennas would have here is
its reception pattern where the antenna could be orientated to be
relatively insensitive in the direction of the noise signal. This
generally is not helpful for short wave signals though because they are
generally too spread out directionally instead of looking like a point
source to take advantage of antenna nulls. Another problem for most
people is the fact that they cannot get the antenna up high enough for
it to exhibit its directional characteristics to a great degree.
A local noise is another matter greatly affecting many peoples
reception of short wave signals since many electronic devices around
the home and neighbor零 homes generate noise. Here the type of antenna,
how it is connected to the receiver, and where it is located on the
user零 property makes a huge difference on what may be heard.
Fundamentally, you want the entire antenna system to reject common mode
noise since to a local antenna this is the mode in which, the local
noise will couple to the antenna. You will want to use an antenna that
is balanced (Hertzian) instead of unbalanced (Marconi). You might also
want to consider using an antenna type that responds more to the
magnetic field component of the radio wave instead of the electric.
These two suggestions encompass the fact that most of the local noise
energy reaching and coupling to the antenna is a common mode electric
field and since the far field broadcast signals you want to receive is
composed of both electric and magnetic the later will be enhanced at
the expense of the former.
The connection from radio to antenna is best shielded so you would use
coax. You could use a balance line but they are harder to acquire, use,
and still will not work as well as coax shielding against local noise.
The antenna would be located as far from the majority of local noise
sources as possible on the property. Distance reduces the coupling to
local noise sources.
--
Telamon
Ventura, California
Uncle Peter
"Telamon" <telamon_s...@pacbell.net.is.invalid> wrote in message
news:telamon_spamshield-E...@news.sf.sbcglobal.net...
> In article <sBEDc.1168$Rr2.4@lakeread03>,
> " Uncle Peter" <radiocon...@cox.netSPAM> wrote:
>
> > > > How does the antenna differentiate between "noise" and a valid
> > signal?
>
>
SNIP
>
> Fundamentally, you want the entire antenna system to reject common mode
> noise since to a local antenna this is the mode in which, the local
> noise will couple to the antenna. You will want to use an antenna that
> is balanced (Hertzian) instead of unbalanced (Marconi). You might also
> want to consider using an antenna type that responds more to the
> magnetic field component of the radio wave instead of the electric.
> These two suggestions encompass the fact that most of the local noise
> energy reaching and coupling to the antenna is a common mode electric
> field and since the far field broadcast signals you want to receive is
> composed of both electric and magnetic the later will be enhanced at
> the expense of the former.
>
> The connection from radio to antenna is best shielded so you would use
> coax. You could use a balance line but they are harder to acquire, use,
> and still will not work as well as coax shielding against local noise.
>
> The antenna would be located as far from the majority of local noise
> sources as possible on the property. Distance reduces the coupling to
> local noise sources.
>
> --
> Telamon
> Ventura, California
You'd also have to decouple the coax shield from the antenna to
prevent signals or noise from carried on the outside of the shield
common-mode fashion from being coupled back into your
remotely located antenna.
Pete
John Doty
> A local noise is another matter greatly affecting many peoples
> reception of short wave signals since many electronic devices around
> the home and neighbor零 homes generate noise. Here the type of antenna,
> how it is connected to the receiver, and where it is located on the
> user零 property makes a huge difference on what may be heard.
>
> Fundamentally, you want the entire antenna system to reject common mode
> noise since to a local antenna this is the mode in which, the local
> noise will couple to the antenna.
Yes!
> You will want to use an antenna that
> is balanced (Hertzian) instead of unbalanced (Marconi).
With an unbalanced antenna you must take more care to keep common mode
out of the feed system. It is not terribly hard, however, to reduce
common mode coupling to negligible levels, even with an unbalanced
antenna (see
http://www.anarc.org/naswa/badx/antennas/low-noise_antenna.html). One
may want an unbalanced system for other reasons. A balanced dipole close
to the ground generally has a poor vertical radiation pattern, while an
inverted-L is much better.
> You might also
> want to consider using an antenna type that responds more to the
> magnetic field component of the radio wave instead of the electric.
> These two suggestions encompass the fact that most of the local noise
> energy reaching and coupling to the antenna is a common mode electric
> field and since the far field broadcast signals you want to receive is
> composed of both electric and magnetic the later will be enhanced at
> the expense of the former.
This claim is widely made in the hobbyist literature, but I've never
seen any measurements to back it up. I've tried to check it myself, and
found the opposite: close to modern sources of EMI, the field tends to
be predominantly magnetic. You have to be very close the source to see
any effect at all: beyond ~0.1 wavelength induction balances the field
pretty effectively.
> The connection from radio to antenna is best shielded so you would use
> coax. You could use a balance line but they are harder to acquire, use,
> and still will not work as well as coax shielding against local noise.
>
> The antenna would be located as far from the majority of local noise
> sources as possible on the property. Distance reduces the coupling to
> local noise sources.
Yes!
-jpd
adddress@spamfree.com CW
group, you run an unshielded lead in (part of the antenna) right into the
shack (big noise source). When I made my prior comments about the lack of
consideration given to receive antenna, I was referring to the antenna
group. I didn't realize that the message was cross posted. It just amazes me
that they will debate a transmitting antenna to minute detail but receiving
antennas deserve no consideration other than a random piece of wire thrown
into a tree. Despite their often one sidedness I have learned a great deal
from them and mean no disrespect.
" Uncle Peter" <radiocon...@cox.netSPAM> wrote in message
news:sBEDc.1168$Rr2.4@lakeread03...
adddress@spamfree.com CW
" Uncle Peter" <radiocon...@cox.netSPAM> wrote in message
Quite true.
>
>
Richard Clark
wrote:
> When I made my prior comments about the lack of
>consideration given to receive antenna, I was referring to the antenna
>group. I didn't realize that the message was cross posted. It just amazes me
>that they will debate a transmitting antenna to minute detail but receiving
>antennas deserve no consideration other than a random piece of wire thrown
>into a tree.
Hi OM,
As generalizations go, this one falls short with them all.
We here at rec.radio.amateur.antenna often recite the credo that
"reciprocity rules." This means that all considerations given to a
transmitting antenna are equally applied to receiving antennas.
However, I am sure you are responding to the disparity in coverage
between receiving and transmitting antennas - and this is for good
reason. Reception and Transmission are NOT reciprocal operations. A
receiver has far more latitude to accomplish its goal than does a
transmitter. Unless you have an abysmal receiver poorly connected to
an inadequate whip, the stock receiver with a simple length of wire is
often very close to doing a good job. If the receiver suffers from
any of a multitude of issues, there is generally a solution that
answers the problem specifically. About the only thing you can do for
the transmitter is to turn up the power, or lower the transmission
loss. It stands to reason that our focus is on optimizing the loss
side of the balance ledger.
Returning to the credo of "reciprocity rules," any gain to the
advantage of a transmitter is enjoyed by the receiver and the SWLer
stands the same advantage. But if that advantage is measured at 3dB,
this has the significance of 50W in 100W compared to the SWL S-Meter
change from S5 to S6 (BFD). Even though it is the same 3dB, there is
the illusion of perspective (my 50W compared to your 5ÁV). If the SW
station is buried in S9 noise, then this is not an antenna problem
(unless you can null the noise out through careful lobe positioning).
Filtering and/or DSP stand to answer the problem, but these are
obviously not remedies to transmission issues.
There is another thread discussing the goal of constructing a small
loop for 80M reception (and how well 5 turns might achieve some
benefit). The same issues of loss prevail for the comparison of
Radiation Resistance to Ohmic Resistance for a 1 Meter loop. The loop
Rr is in the thousandths of an Ohm and about on par for a small wire's
Ohmic loss. There's that 3dB again and what concerns the transmission
efficiency is far easier to tolerate with the receiver and its surplus
of gain. If the SWLer pays attention to this issue as it concerns the
transmission problems, then that SWLer stands to gain in the
efficiency returned. However, this is not to suggest that there is an
actual need to obtain this efficiency; but if the SWLer mismanages the
construction, the topic is discussed to the necessary depth to correct
it.
A simple basis of comparison will illustrate. Many SW radios have a
ferrite stick antenna that will work with at least some stations (VOA,
WWV, BBC and a host of others). Try transmitting through that same
ferrite stick and it will be like trying to shout through a straw.
Our only alternative is to add an amp, but the big KW is only going to
render smoke.
73's
Richard Clark, KB7QHC
Telamon
John Doty <j...@whispertel.LoseTheH.net> wrote:
> Telamon wrote:
>
< Snip >
>
> This claim is widely made in the hobbyist literature, but I've never
> seen any measurements to back it up. I've tried to check it myself,
> and found the opposite: close to modern sources of EMI, the field
> tends to be predominantly magnetic. You have to be very close the
> source to see any effect at all: beyond ~0.1 wavelength induction
> balances the field pretty effectively.
First off I did not realize this was cross posted so this is my last
post to this thread.
I'm not not regurgitating hobbyist claims but my experience in this
matter. Although 0.1 wavelength is more than enough to cover a urban
lot and your neighbor at short wave frequencies theory does not do
justice to a non homogenous environment we all live in. Most electronic
noise generators do not have efficient antennas attached to them where
the environment easily distorts the electric fields. I have repeatedly
experienced predominantly voltage common mode coupling of local noise
sources. Without exception mitigation methods against voltage common
mode noise were always successful and current mode antennas always
picked up less local noise.
--
Telamon
Ventura, California
BDK
@news.sf.sbcglobal.net>, telamon_s...@pacbell.net.is.invalid
says...
My main problems with noise have been the next door neighbors dimmer and
the transformer that threw out hash galore and took the electric company
about 2 years to fix. When it rained, or was cold enough for dew to
form, it was like a really annoying buzzer from about 0 to 10 MHZ. I was
overjoyed the night it blew up. It was "on the list" due to my nagging
them, but lightning did the job...
BDK
flightless steaming duck
You are posting this hole trhead on two dutch newsgroups!
Telamon a écrit
RHF
> They don't but if you go by the advice you generally get on the antenna
> group, you run an unshielded lead in (part of the antenna) right into the
> shack (big noise source). When I made my prior comments about the lack of
> consideration given to receive antenna, I was referring to the antenna
> group. I didn't realize that the message was cross posted. It just amazes me
> that they will debate a transmitting antenna to minute detail but receiving
> antennas deserve no consideration other than a random piece of wire thrown
> into a tree. Despite their often one sidedness I have learned a great deal
> from them and mean no disrespect.
>
>
CW,
That is 'why' I set-up the "Shortwave Listeners (SWL) AM/FM Antennas"
eGroup on YAHOO !
SWL-ANT=> http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
Most HAM are concerned about getting the most power transfer
into the Antenna and the greatest Signal Output from the
Antenna. This may not result in the best receiving antenna.
A better SWL Receive ONLY Antenna is usually a result of
a Clean 'outside' Signal with a "Low Noise" factor.
Yes the topic is SWL Receive ONLY Antennas.
SWL-ANT=> http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
iane ~ RHF
.
RHF
= = = news:<jb5vd0pb48mj0jb3l...@4ax.com>...
RC,
In the same location using the same Antenna:
100uV of background noise being re-radiated by a Transmitting
Antenna that is being powered at 50W or 100W is simply not an
issue for the Amateur/HAM.
- Background Noise is NOT an Issue when thinking of Transmitting
Antennas that are Radiating Power in the Tens and Hundreds of Watts.
- For the HAM Signal-to-Noise is NOT a Transmission Antenna Parameter.
100uV of background noise being received by a Receiving Antenna
that is seeking a 25uV Signal is unacceptable for a SWLer.
- Background Noise IS an Issue when thinking of Receiving Antennas
that are 'acquiring' Radiated Power in the Milliwatts or micro-watts.
- For the SWLer Signal-to-Noise IS a key Receiving Antenna Parameter.
iane ~ RHF
.
Shortwave Listeners (SWL) AM/FM Antennas eGroup on YAHOO !
SWL-ANTENNA=> http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Richard Clark
wrote:
>RC,
>
>In the same location using the same Antenna:
>
>100uV of background noise being re-radiated by a Transmitting
>Antenna that is being powered at 50W or 100W is simply not an
>issue for the Amateur/HAM.
Hello iane,
The construction of this "argument" is called a strawman. Who is to
say it "is simply not an issue?" Further, who is to say it is?
Amateur radios, as last I noted, contain receivers too and suffer
every much any debility as a SWL set. Simply put, there is no
separation to argue.
>- Background Noise is NOT an Issue when thinking of Transmitting
>Antennas that are Radiating Power in the Tens and Hundreds of Watts.
>- For the HAM Signal-to-Noise is NOT a Transmission Antenna Parameter.
Then why would you presume this is a fault in discussion here in an
antenna group? True this is cross-posted, but again, we have every
concern with reception that a SWLer would also have. Again, there is
no separation of issues to argue.
>100uV of background noise being received by a Receiving Antenna
>that is seeking a 25uV Signal is unacceptable for a SWLer.
Again, Amateur radio is just as concerned and seeks every remedy where
ever it may be found. To continue:
>- Background Noise IS an Issue when thinking of Receiving Antennas
>that are 'acquiring' Radiated Power in the Milliwatts or micro-watts.
>- For the SWLer Signal-to-Noise IS a key Receiving Antenna Parameter.
Antennas have no capacity to reduce Signal to Noise ratios except by
virtue of narrowing lobes to eliminate noise by placing it in a null
(if that is in fact a viable option either in the sense of having a
null, or having a null to a noise source that is not on the same
meridian as the signal of interest).
To this point, you have not offered any particularly receive dominated
issue that is not already a heavily trafficked topic with transmission
antennas. In fact, the presumption there are unique reception
antennas that are more suitable than their transmission cousins is
simply the artifice of my aforementioned advantage of the RF Gain
control. It has been long established (through the simple act of
purchase power) that receivers have far more gain available than
needed except for the worst of antenna designs (and that has to be an
exceptionally vile design).
Such examples of small loops used for MF are proof positive how poor
an antenna can be, and the RF gain knob resurrecting its pitiful
efficiency. This does NOT demonstrate some illusion of superior
receive antenna design; rather it is more smoke and mirrors as an
argument. Inverting the argument, if you had a full sized antenna for
that band, you would only need a galena crystal and cat whisker to
power your hi-Z headset. For DX you would only need a $5 AF
amplifier. The smaller antenna clearly needs more dollars expended to
offset the debilities of the poorer efficiency. The specious argument
is tailored for the technically effete who would rather push a credit
card across the display counter than build their own cheap solution.
Take heart that this not simply a cheap shot, there are as many Hams
who don't know which end of the soldering iron to pick up either.
Mark1
Richard Clark plaatste dit op zijn scherm :
Richard Clark
<vonkenboer2004(geen-rommel)@hotmail.com> wrote:
>Zeg hallo, dit is een Nederlandse nieuwsgroep hoor :-P
>
probeer de vertaaldiensten van bable vissen bij
http://babelfish.altavista.com/
Mark1
LOL, we zien hoe goed de vertaalmachine werkt (not)
Gert-Jan Dam PG0G
Dit even ter illustratie...Tis niet te lezen.
Dergelijke voorbeelden van kleine lijnen die voor MF worden gebruikt
zijn bewijspositief hoe armen een antenne kan zijn, en de de
aanwinstenknop van rf doend herleven zijn meelijwekkende efficiency.
Dit toont niet aan één of andere illusie van meerdere antenneontwerp
ontvangt; eerder is het meer rook en spiegels als argument. Omkerend
het argument, als u een volledige met maat antenne voor die band had,
zou u slechts een van de loodglanskristal en kat bakkebaard nodig
hebben om uw hoofdtelefoon aan te drijven hallo-z. Voor DX zou u
slechts een $5 AF versterker nodig hebben. De kleinere antenne vergt
duidelijk meer dollars besteed om debilities van de slechtere
efficiency te compenseren. Het specious argument wordt gemaakt voor
technisch uitgeput wie eerder een creditcard over de vertoningsteller
dan bouwt hun eigen goedkope oplossing zou duwen. Neem eenvoudig hart
dat dit niet een goedkoop schot, zijn er zo vele Hammen die don't weten
welk eind van de soldeerbout om één van beiden op te nemen.
--
Met vriendelijke groet,
Gert-Jan Dam
HF knutselhoekje: http://www.pg0g.net
De nieuwsgroepronde Homepage: http://www.nieuwsgroepronde.tk
http://members.hostedscripts.com/antispam.html
Mark1
hebben om uw hoofdtelefoon aan te drijven'
rofl
Mark
Na rijp beraad schreef Gert-Jan Dam PG0G :
Gert-Jan Dam PG0G
> uw hoofdtelefoon aan te drijven'
Ja haha. Lachen zo'n vertaal programma :D
> rofl
> Mark
Richard Clark
<gertjandam...@fastmail.fm> wrote:
>Dit even ter illustratie...Tis niet te lezen.
>
>Dergelijke voorbeelden van kleine lijnen die voor MF worden gebruikt
>zijn bewijspositief hoe armen een antenne kan zijn, en de de
>aanwinstenknop van rf doend herleven zijn meelijwekkende efficiency.
>Dit toont niet aan één of andere illusie van meerdere antenneontwerp
>ontvangt; eerder is het meer rook en spiegels als argument. Omkerend
>het argument, als u een volledige met maat antenne voor die band had,
>zou u slechts een van de loodglanskristal en kat bakkebaard nodig
>hebben om uw hoofdtelefoon aan te drijven hallo-z. Voor DX zou u
>slechts een $5 AF versterker nodig hebben. De kleinere antenne vergt
>duidelijk meer dollars besteed om debilities van de slechtere
>efficiency te compenseren. Het specious argument wordt gemaakt voor
>technisch uitgeput wie eerder een creditcard over de vertoningsteller
>dan bouwt hun eigen goedkope oplossing zou duwen. Neem eenvoudig hart
>dat dit niet een goedkoop schot, zijn er zo vele Hammen die don't weten
>welk eind van de soldeerbout om één van beiden op te nemen.
Hi OM,
Één of andere goede vertaling, slecht wat. Wat kwamen uit zeer goed
zelfs daarna twee vertalingen.
Richard Clark
<gertjandam...@fastmail.fm> wrote:
>Op dinsdag 29-6-2004 krabbelde Mark1 op mijn schermpje
>> 'zou u slechts een van de loodglanskristal en kat bakkebaard nodig hebben om
>> uw hoofdtelefoon aan te drijven'
>
>Ja haha. Lachen zo'n vertaal programma :D
>
>> rofl
>> Mark
Hi OM,
het van het kattenbakkebaard en loodglans kristal is de oude
componenten van de tijddetector. De bakkebaard van de kat is fijne
draad. Het kristal van het loodglans is semiconducting mineraal (waar
de draad raakt en contact met een oxyde opneemt). De twee componenten
maken een diode.
Gert-Jan Dam PG0G
> On Tue, 29 Jun 2004 11:46:03 +0200, Gert-Jan Dam PG0G
> Één of andere goede vertaling, slecht wat. Wat kwamen uit zeer goed
> zelfs daarna twee vertalingen.
Ik heb een willekeurig stuk vertaald. Dit kwam eruit en het is gewoon
onleesbaar.
> 73's
> Richard Clark, KB7QHC
--
Richard Clark
<gertjandam...@fastmail.fm> wrote:
>Ik heb een willekeurig stuk vertaald. Dit kwam eruit en het is gewoon
>onleesbaar.
>
Mijn fout toen. De kortere zinnen zijn nodig.
Gert-Jan Dam PG0G
> het van het kattenbakkebaard en loodglans kristal is de oude
> componenten van de tijddetector. De bakkebaard van de kat is fijne
> draad. Het kristal van het loodglans is semiconducting mineraal (waar
> de draad raakt en contact met een oxyde opneemt). De twee componenten
> maken een diode.
Ik zal eens van een bakkebaard van een kat en wat loodglans een diode
maken hi.
Sorry, _This_ is a Dutch newsgroup!
> 73's
> Richard Clark, KB7QHC
--
RHF
Spoken (written) like a True Amateur, and precicly why most SWLs
ignore what is written in reply to SWL 'type' Antennas questions
by HAMs.
Most SWLs work to get the best signal (cleanest signal and lowest
noise) they can to be able to listen to what they what to hear.
The HAM would hardly ever consider a 'random' wire Antenna;
but to the SWL'er the "Random" Wire Antenna 'concept' is a
natural to fill their available space. Power handling, gain
and antenna design characteristics are the focus of the HAM.
As far as the AM/MW Loop Antenna's are concerned. For the AM/MW
DX'er these Antenna's perform the best for their size and the
available space that the average Broadcast Listener (BCL) has
for these Medium Wave Band. The SWL'er wants to hear any Radio
Station out there from any direction.
The 'focus' of the SWL'er is simpy different then the Amateur;
and the majority of SWL'ers are Program Listeners who seldom
listen to the HAM Bands.
iane ~ RHF
.
.
= = = Richard Clark <kb7...@comcast.net> wrote in message
= = = news:<le32e0phhbq88f46t...@4ax.com>...
Richard Clark
<gertjandam...@fastmail.fm> wrote:
>Sorry, _This_ is a Dutch newsgroup!
Of course it is: nl.radio.amateur
This is an amateur antenna discussion. This discussion originated
from this group (nl.radio.amateur). If this is a mistake, take it up
with the original poster.
Richard Clark
>RC (KB7QHC),
>
>Spoken (written) like a True Amateur, and precicly why most SWLs
>ignore what is written in reply to SWL 'type' Antennas questions
>by HAMs.
Strange logic to offer that a listener comes here to post a query they
will ignore in anticipation. Rather self serving argument isn't it?
>Most SWLs work to get the best signal (cleanest signal and lowest
>noise) they can to be able to listen to what they what to hear.
There is nothing in this statement that distinguishes amateur from
listener. Further, it contains absolutely no technical material to
support any sense of this exclusivity of concern. To respond in kind,
you don't even rise to amateur status.
>The HAM would hardly ever consider a 'random' wire Antenna;
Now this is a statement that is clearly in error. The archives will
attest to this.
>but to the SWL'er the "Random" Wire Antenna 'concept' is a
>natural to fill their available space. Power handling, gain
>and antenna design characteristics are the focus of the HAM.
As they are no more or less for a listener. If you find some other
motivation, it is strictly your own prejudice.
>As far as the AM/MW Loop Antenna's are concerned. For the AM/MW
>DX'er these Antenna's perform the best for their size and the
>available space that the average Broadcast Listener (BCL) has
>for these Medium Wave Band. The SWL'er wants to hear any Radio
>Station out there from any direction.
Perhaps you should attend this board more often to learn the
fundamentals. There is no impediment to hearing any Radio Station out
there from any direction with simple verticals. SW sets come with
them you know.
>The 'focus' of the SWL'er is simpy different then the Amateur;
>and the majority of SWL'ers are Program Listeners who seldom
>listen to the HAM Bands.
So why are you posting to an amateur group? Why an antenna group?
You would be better served through your self-imposed limitations by
staying out of the fast lane.
73's
Richard Clark, KB7QHC, WPE0EPH
p.s. if the WPE0EPH is unknown to you, it denotes my having been a
Shortwave listener for 40 years and registered with the Popular
Electronics DX club (as well as a sack full of others from around the
world).
Mark1
Translation, : it from it cat-sideburn and leadshine cristal is the old
components of the timedetector. The sideburn of the cat is fine thread.
And so on.
So pse remove this group from future postings.
Tam/WB2TT
> So why are you posting to an amateur group? Why an antenna group?
> You would be better served through your self-imposed limitations by
> staying out of the fast lane.
>
> 73's
> Richard Clark, KB7QHC, WPE0EPH
>
> p.s. if the WPE0EPH is unknown to you, it denotes my having been a
> Shortwave listener for 40 years and registered with the Popular
> Electronics DX club (as well as a sack full of others from around the
> world).
Richard,
Probably to a lot of people a radio or electronic hobbyist is an "amateur".
Impression I get is that some CBers think so also. From looking at old
literature, the search for the holy grail of a noise free antenna, seems to
back to around T=0. It would help, if the manufacturers of SWL receivers
would add noise blankers in sub $500 radios. I did not see any in the AES
catalog below that price that claimed to have a noise blanker. I won't even
delve on IF filter shape factor.
ps. I can beat your 40 years by about 10.
Tam/WB2TT
John Doty
> Antennas have no capacity to reduce Signal to Noise ratios except by
> virtue of narrowing lobes to eliminate noise by placing it in a null
> (if that is in fact a viable option either in the sense of having a
> null, or having a null to a noise source that is not on the same
> meridian as the signal of interest).
Not true. You are making the assumption that that the antenna only picks
up radiated modes. Non-radiated electromagnetic modes are also
troublesome, particularly common mode on the transmission line. This
tends to be the way that locally generated noise from household gadgets
gets into an antenna system.
Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
common mode on the mains, finds its way to the power cord of your
transceiver, rides out on the feedline to the antenna, and then couples
back through differential mode to your receiver input. That's not a very
efficient coupling path, so suppose it has a loss of 60 dB. You'll still
get 10 nW to the receiver. This is a lot: even if it's spread over 30
MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
very serious quantity of noise.
On the other hand, if your transmitter puts out 1 kW, 60 dB of loss
means it only delivers 1 mW of RF to the dimmer, an amount unlikely to
interfere with its operation. Reciprocity does not mean *consequences*
are symmetrical.
> To this point, you have not offered any particularly receive dominated
> issue that is not already a heavily trafficked topic with transmission
> antennas.
A deep, steerable null can be extremely useful for reception, but its
not generally useful for transmission.
> In fact, the presumption there are unique reception
> antennas that are more suitable than their transmission cousins is
> simply the artifice of my aforementioned advantage of the RF Gain
> control. It has been long established (through the simple act of
> purchase power) that receivers have far more gain available than
> needed except for the worst of antenna designs (and that has to be an
> exceptionally vile design).
>
> Such examples of small loops used for MF are proof positive how poor
> an antenna can be, and the RF gain knob resurrecting its pitiful
> efficiency.
But for MWDX reception, efficiency simply isn't an important virtue.
Gain is cheap. What matters is the steerable nulls. An efficient
*steerable* MW antenna is enormous and expensive.
> This does NOT demonstrate some illusion of superior
> receive antenna design; rather it is more smoke and mirrors as an
> argument. Inverting the argument, if you had a full sized antenna for
> that band, you would only need a galena crystal and cat whisker to
> power your hi-Z headset. For DX you would only need a $5 AF
> amplifier. The smaller antenna clearly needs more dollars expended to
> offset the debilities of the poorer efficiency.
Sensitivity is the cheapest, easiest virtue to put into a receiver.
Essentially all modern receivers have plenty. Indeed, the cheap ones
often overload when presented with an efficient antenna: you have to
spend the dollars to be able to handle the big signals!
Speaking of strawmen, have you ever actually tried DXing with a crystal
radio?
> The specious argument
> is tailored for the technically effete who would rather push a credit
> card across the display counter than build their own cheap solution.
> Take heart that this not simply a cheap shot, there are as many Hams
> who don't know which end of the soldering iron to pick up either.
I love designing and building antennas: applied physics is fun. But it's
good engineering to go with the strengths of your technology. For my
inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of
effective bandwidth, something that is perhaps of little use to hams,
but is very useful to an SWL in conjunction with the frequency agility
of a modern receiver. 4 dB of efficiency loss is of negligible
consequence at HF and below if your receiver has a decent noise figure.
I've never seen mention of this efficiency/bandwidth tradeoff in the ham
literature, but it's not hard to find in the professional literature.
For details of a specific calculation, see:
http://anarc.org/naswa/badx/antennas/SWL_longwire.html
-jpd
Mark1
John Doty schreef op 29-6-04 :
Richard Clark
<j...@whispertel.LoseTheH.net> wrote:
>You are making the assumption that that the antenna only picks
>up radiated modes.
I am making no such assumption and all following commentary does
absolutely nothing to separate the concerns of SWLers from Ham
activity.
>Non-radiated electromagnetic modes are also
>troublesome, particularly common mode on the transmission line. This
>tends to be the way that locally generated noise from household gadgets
>gets into an antenna system.
>
>Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
>common mode on the mains, finds its way to the power cord of your
>transceiver, rides out on the feedline to the antenna, and then couples
>back through differential mode to your receiver input. That's not a very
>efficient coupling path, so suppose it has a loss of 60 dB. You'll still
>get 10 nW to the receiver. This is a lot: even if it's spread over 30
>MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
>very serious quantity of noise.
Let's work with exactly that scenario you offered.
S6 (Calibrated) on my Drake TR-7 is -88dBm - so close to your 10猩 to
be indistinguishable. My TS-430 varies from -80dBm to -73dBm. There
is no calibrated S-Meter for my DX-440, but for a $200 SW set, its
sensitivity is -90dBm for a full scale meter indication (about 7dB
range from top to bottom).
All very well and good. Now if we regard this speculation of 10mW (it
is, after all, the epitome of a wild ass guess, isn't it?); then,
let's reverse engineer that 10nW product from 6kHz buckets over the
range of 30MHz to find 50琺 which is 23dB below the original power
presumably suppressed 60dB. Well, I have either pencil-whipped you,
or you me, or each other - the numbers don't add up. Hardly matters
given the original specification had no basis in fact.
However, if I return to the original "problem" of noise derived from
household sources; then that is also something I have closely
measured.
Across time, frequency, antennas, and known noise sources I have found
it as low as S1 for my longwire (an antenna supposedly unused by Hams)
to as high as S7 (for that same longwire). My loops, dipoles and
verticals hardly fell outside of this range to present any gilt-edge
design.
With every circuit in the house broken (operating battery power in the
dark), average noise level was either S2 for a vertical, or S1 to S3
for a loop (rather upsetting the voodoo of loops being quiet and
verticals being noisy). When I returned power to the house by stages,
I insured every opportunity of injecting noise by setting dimmers to
their worst position (about 50%). In the low bands, I suffered as
much as S8 noise levels with an average of S5 when the house was full
lit (also including fluorescents) and all noise sources adding to the
cacophony of reception. This was for a loop antenna.
>On the other hand, if your transmitter puts out 1 kW, 60 dB of loss
>means it only delivers 1 mW of RF to the dimmer, an amount unlikely to
>interfere with its operation. Reciprocity does not mean *consequences*
>are symmetrical.
This effect of reciprocity has been reported so frequently in this
group so as to negate your premise. We have many queries for how to
solve this problem.
>> To this point, you have not offered any particularly receive dominated
>> issue that is not already a heavily trafficked topic with transmission
>> antennas.
>
>A deep, steerable null can be extremely useful for reception, but its
>not generally useful for transmission.
This really goes off the deep edge. Barring loss introduced for the
sake of jimmying the logic, transmitters AND receivers enjoy the GAIN
derived from the introduction of a null not otherwise part of the
characteristic. This is a commonplace of theory and practice. Where
ever you can design or contribute to a null; then this must of
necessity result in an increase in signal outside of its region.
These are all commonplace observations discussed here that are
observable for either Ham or SWL operations. There is NO differential
offered in these observations that separate SWL from Ham activities.
>> Such examples of small loops used for MF are proof positive how poor
>> an antenna can be, and the RF gain knob resurrecting its pitiful
>> efficiency.
>
>But for MWDX reception, efficiency simply isn't an important virtue.
I believe I have said that at least 3 to 5 times already.
>Gain is cheap. What matters is the steerable nulls. An efficient
>*steerable* MW antenna is enormous and expensive.
Who needs an efficient MW antenna?
>> This does NOT demonstrate some illusion of superior
>> receive antenna design; rather it is more smoke and mirrors as an
>> argument. Inverting the argument, if you had a full sized antenna for
>> that band, you would only need a galena crystal and cat whisker to
>> power your hi-Z headset. For DX you would only need a $5 AF
>> amplifier. The smaller antenna clearly needs more dollars expended to
>> offset the debilities of the poorer efficiency.
>
>Sensitivity is the cheapest, easiest virtue to put into a receiver.
>Essentially all modern receivers have plenty. Indeed, the cheap ones
>often overload when presented with an efficient antenna: you have to
>spend the dollars to be able to handle the big signals!
All of $20 if you have any technical capacity. Otherwise push the
credit card across the display counter and spend as much as they can
sell you. This argument is like driving your car into the shop to get
the air changed in your tires every 100 miles.
Again, front end overload is a very common complaint offered here by
SWLers who are then advised in how to simply AND cheaply combat this
problem.
>Speaking of strawmen, have you ever actually tried DXing with a crystal
>radio?
Sure, what is so remarkable about that? Beyond this simple design,
ever hear of a super-Regen receiver? You don't need to spend half a
kilo-buck to get the same sensitivity and filtering is dirt cheap.
How about Q-multipliers? All such topics barely spread the wallet as
much as the illusion of more buttons make a better rig.
>I love designing and building antennas: applied physics is fun. But it's
>good engineering to go with the strengths of your technology. For my
>inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of
>effective bandwidth, something that is perhaps of little use to hams,
>but is very useful to an SWL in conjunction with the frequency agility
>of a modern receiver. 4 dB of efficiency loss is of negligible
>consequence at HF and below if your receiver has a decent noise figure.
As I pointed out to Yahoo, if you choose to cripple yourself, then
slide on over to the shoulder and enjoy kicking up dust and rocks as
you travel down the road. a 4dB loss for an inverted L (hardly a SW
invention) is far too simple to remedy to make its suffering a boast
of martyrdom. It is a strange argument to offer that you can't afford
a $20 solution for your $500 set and $2 worth of wire.
>I've never seen mention of this efficiency/bandwidth tradeoff in the ham
>literature,
You haven't looked. Either contrived, wholly fictional, or accurately
represented, it is part of the stock in trade for selling antennas.
In this group, I would wager its discussion consumes more bandwidth
than bragging about how many QSL cards have been pasted to the wall.
>but it's not hard to find in the professional literature.
>For details of a specific calculation, see:
>
>http://anarc.org/naswa/badx/antennas/SWL_longwire.html
>
>-jpd
It would do you well to note that this "professional" whom you rely
upon, John Kraus, is one of the most notable Ham Radio Operators
frequently acknowledged and referred to here.
Do you or others have any actual differentiable discussion, or is this
simply an outlet for appoligia for why it isn't worth the strain to
lift a soldering iron when you can bench press a credit card?
John Doty
10 uV into 50 ohms is 2 pW, not 10 nW (E^2/R). 2 pW = -117 dBW = -87
dBm. Multiplying by 30000/6 = 5000 buckets makes 10 nW or -50 dBm.
Cancel the assumed 60 dB loss and I get +10 dBm, or 10 mW. The numbers
add up fine.
>
> However, if I return to the original "problem" of noise derived from
> household sources; then that is also something I have closely
> measured.
>
> Across time, frequency, antennas, and known noise sources I have found
> it as low as S1 for my longwire (an antenna supposedly unused by Hams)
> to as high as S7 (for that same longwire). My loops, dipoles and
> verticals hardly fell outside of this range to present any gilt-edge
> design.
Just because you couldn't doesn't mean others can't. Look at the rest of
the articles on the BADX site. Taking steps to minimize common mode
coupling has worked very well for me, and many people tell me it works
for them too.
You might also find the articles at http://www.qsl.net/wa1ion/
interesting, especially the one entitled "Another Look at Noise Reducing
Antennas". Mark's antenna designs are generally useless for
transmitting, but they make superb MWDX receiving antennas.
Certainly there is. A narrow null takes little power from the pattern:
you get little gain by putting that in a broad lobe. For example, an
elementary dipole has, theoretically, infinitely deep nulls yet it only
has about 2 dBi gain. Now consider a phased array: small phasing errors
have little effect on the gain, but they can have a large effect on the
null depth.
When transmitting, you're generally interested in putting the power in
the right place, but when receiving you're often more interested in
avoiding picking up power from the wrong place. These considerations are
only weakly related.
>
>
>>>Such examples of small loops used for MF are proof positive how poor
>>>an antenna can be, and the RF gain knob resurrecting its pitiful
>>>efficiency.
>>
>>But for MWDX reception, efficiency simply isn't an important virtue.
>
>
> I believe I have said that at least 3 to 5 times already.
>
>
>>Gain is cheap. What matters is the steerable nulls. An efficient
>>*steerable* MW antenna is enormous and expensive.
>
>
> Who needs an efficient MW antenna?
People who transmit, of course!
>>Speaking of strawmen, have you ever actually tried DXing with a crystal
>>radio?
>
>
> Sure, what is so remarkable about that? Beyond this simple design,
> ever hear of a super-Regen receiver? You don't need to spend half a
> kilo-buck to get the same sensitivity and filtering is dirt cheap.
Sure. Used them. Selectivity is *lousy*. For SW, I've gotten better
results with a plain regen. Still, my Drake R-8 is better for DX, my
Sony ICF-SW100 travels easy, and my Stromberg-Carlson 58-T sounds
wonderful, so I haven't played with a regen in quite a while.
> How about Q-multipliers? All such topics barely spread the wallet as
> much as the illusion of more buttons make a better rig.
I have a Heathkit Q-multiplier I built in 1965. It's pretty good at
nulling out unwanted carriers, but in peak mode the shape factor of a
single resonance is pretty poor. At the moment I don't have a working
receiver it's really suited to, but I have a Halli S-40 one of my
in-laws gave me, and one of these days I'll find the time to repair it
(it's in really poor shape). The S-40 could probably use a Q-multiplier
once I've got it in working order.
>
>
>>I love designing and building antennas: applied physics is fun. But it's
>>good engineering to go with the strengths of your technology. For my
>>inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of
>>effective bandwidth, something that is perhaps of little use to hams,
>>but is very useful to an SWL in conjunction with the frequency agility
>>of a modern receiver. 4 dB of efficiency loss is of negligible
>>consequence at HF and below if your receiver has a decent noise figure.
>
>
> As I pointed out to Yahoo, if you choose to cripple yourself, then
> slide on over to the shoulder and enjoy kicking up dust and rocks as
> you travel down the road. a 4dB loss for an inverted L (hardly a SW
> invention) is far too simple to remedy to make its suffering a boast
> of martyrdom. It is a strange argument to offer that you can't afford
> a $20 solution for your $500 set and $2 worth of wire.
How would you undo that 4 dB loss without loss of bandwidth? I'm hardly
boasting of martyrdom anyway: a broadband inverted L is a fine general
purpose receiving antenna.
>
>
>>I've never seen mention of this efficiency/bandwidth tradeoff in the ham
>>literature,
>
>
> You haven't looked. Either contrived, wholly fictional, or accurately
> represented, it is part of the stock in trade for selling antennas.
> In this group, I would wager its discussion consumes more bandwidth
> than bragging about how many QSL cards have been pasted to the wall.
Examples?
>>but it's not hard to find in the professional literature.
>>For details of a specific calculation, see:
>>
>>http://anarc.org/naswa/badx/antennas/SWL_longwire.html
>>
>>-jpd
>
>
> It would do you well to note that this "professional" whom you rely
> upon, John Kraus, is one of the most notable Ham Radio Operators
> frequently acknowledged and referred to here.
He knew a great deal about the full range of antenna designs and
applications, not just ham radio. And he sure knew his physics.
>
> Do you or others have any actual differentiable discussion, or is this
> simply an outlet for appoligia for why it isn't worth the strain to
> lift a soldering iron when you can bench press a credit card?
When a soldering iron is the best tool to get the job done, I lift a
soldering iron. The Stromberg-Carlson was a "bare chassis" restoration:
most of the resistors were >50% off value, the paper capacitors were
leaking, the electrolytics were dry, and one of the RF coils was open
(disassembling and reassembling the coil turret was a real pain). Still,
it was worth the work to get that wonderful sound.
The NASA certified techs I work with professionally tell me I'm pretty
good with a soldering iron, considering I'm a physicist. From them,
that's high praise :-)
-jpd
Richard Clark
<j...@whispertel.LoseTheH.net> wrote:
>>>Consider a lamp dimmer that generates 10 mW of RFI, which rides out in
>>>common mode on the mains, finds its way to the power cord of your
>>>transceiver, rides out on the feedline to the antenna, and then couples
>>>back through differential mode to your receiver input. That's not a very
>>>efficient coupling path, so suppose it has a loss of 60 dB. You'll still
>>>get 10 nW to the receiver. This is a lot: even if it's spread over 30
>>>MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a
>>>very serious quantity of noise.
>10 uV into 50 ohms is 2 pW, not 10 nW (E^2/R). 2 pW = -117 dBW = -87
>dBm. Multiplying by 30000/6 = 5000 buckets makes 10 nW or -50 dBm.
>Cancel the assumed 60 dB loss and I get +10 dBm, or 10 mW. The numbers
>add up fine.
As I said, one of the two of us was being pencil-whipped. This does
nothing to change the fact that the original term has no basis in
fact. It could as easily be laid to the effects of a nuclear EMP 2000
miles away. There will always be something to blame, and that is NOT
a solution nor is it differentiable between Ham and SWL antennas.
>> However, if I return to the original "problem" of noise derived from
>> household sources; then that is also something I have closely
>> measured.
>>
>> Across time, frequency, antennas, and known noise sources I have found
>> it as low as S1 for my longwire (an antenna supposedly unused by Hams)
>> to as high as S7 (for that same longwire). My loops, dipoles and
>> verticals hardly fell outside of this range to present any gilt-edge
>> design.
>
>Just because you couldn't doesn't mean others can't.
Can't WHAT? The numbers I offer are shown of direct experience
correlatable to real world conditions and conform to 3 Sigma of SWL
conditions. Being correlatable they were also resolved and reduced to
that same unpowered baseline without forcing me off the grid into
darkness. My station sits with a noise flicker based upon
atmospherics and radiation borne products, not the usual household
pollution that I both describe above and eliminated through techniques
described as commonplaces in this group.
There are no magic antennas and no magic rituals equal to these
commonplace practices that are offered here.
>Look at the rest of
>the articles on the BADX site. Taking steps to minimize common mode
>coupling has worked very well for me, and many people tell me it works
>for them too.
This material is NOT novel by any stretch of the imagination.
However, it is hardly fully encompassing and falls short of the entire
treatment. The notion that a spike in the ground solves common mode
reveals a very limited experience in the matter, and simply devolves
to the misty eyed sentimentality of "it works for me, so there is no
better way for you." Testimonial is a poor substitute for how and why
- especially when the suggested solution inevitably fails for someone.
The common response in that situation is to sneer them away as somehow
deserving their predicament - again, with no one knowing the basis of
the problem, they can hardly help but repeat the same nostrum now
shown to fail somewhere (an anathema in religion).
>You might also find the articles at http://www.qsl.net/wa1ion/
These suggestions grow more bizarre by the posting where the
correspondent offers that SWLers ignore Amateur advice as poor quality
(a remark from a noted Yahoo), and then offer proof of their own
beguiling theories through quotes from - Amateur references.
>interesting, especially the one entitled "Another Look at Noise Reducing
>Antennas". Mark's antenna designs are generally useless for
>transmitting, but they make superb MWDX receiving antennas.
I cannot see how injecting the notion of uselessness is a boon for an
argument upon a physicist who can understand the notion of symmetry or
what is called in this field of study, reciprocity. If it is useless
as a transmit antenna, is it useless as a receive antenna? Of course
not, as such the injection of this comment serves no purpose other
than rhetorical noise.
The problem with such a degraded S/N in the correspondence of ideas is
that the larger body of uninitiated SWLers come to the conclusion that
this "uselessness" is a positive boon to be sought in every antenna
design. Our eminent Yahoo wears this badge of anti-intellectualism as
a patronizing populist.
This discussion also reveals a poverty of alternative designs that
have equal or superior merits, even if devoid of transmitting
application. Those designs are widely discussed here and their merits
are weighed not in prejudicial terms but rather in technical
comparisons and their correlation to application. That is to say,
anyone can make an informed decision on the basis of these evaluations
offered here where we typical discard "testimonials" to the rubbish
heap.
>A narrow null takes little power from the pattern:
>you get little gain by putting that in a broad lobe. For example, an
>elementary dipole has, theoretically, infinitely deep nulls yet it only
>has about 2 dBi gain. Now consider a phased array: small phasing errors
>have little effect on the gain, but they can have a large effect on the
>null depth.
Again, this exposes a lack of experience in the matter. Those nulls
are balanced against the theoretical radiator called an isotropic
source. This is the i of the 2dBi (and in fact is actual;y higher
than that value).
Worse yet, this lack of experience further pollutes the uninitiated
SWLer's notion of this balance of ledger because no one on this earth
is ever going to experience that 2dB gain (nor the supposed sharp
nulls) - and simply due to earth being nearby (an irreconcilable fact
of life that extends out beyond 6 Sigma for the population of
listeners). A simple dipole one quarterwave above earth exhibits an
additional 3dB gain above and beyond your cited number. This goes to
show how your casually abandoned 4dB for an inverted L is so simply
recovered - through real comparisons rather than xeroxed theories.
The level of discussion is so unbalanced with myth, superstition and
hearsay that the casual SWLer seeking advice faces the problem of
sorting out the shit from the shinola. If I were to hike the dipole a
little more, it shows 8dB gain after allowing a real world loss of
1dB. To tell that same casual SWLer 4dB is no great loss gives a
spread of 10dB.
The consequence of this challenging this poor coverage of intellectual
offering is that the casual SWLer having the facts known, can in fact
choose to build a less optimal antenna, one that suits his real world
limitations, and enjoy a design that does not simply discard signal
with abandon. Alternatively, a simpler receiver can perform with an
excellent antenna as well as a box full of expensive knobs can with an
air cooled resistor.
>When transmitting, you're generally interested in putting the power in
>the right place, but when receiving you're often more interested in
>avoiding picking up power from the wrong place. These considerations are
>only weakly related.
This has been spoken too, the limitation is found in the signal and
noise being aligned along the same meridian. If there is any weak
relation it is found in the chance of distribution. The laws of
reciprocity are not violated by chance, and both Ham operator and
SWLer suffer the same odds. There is NOTHING separable here.
>> Who needs an efficient MW antenna?
>
>People who transmit, of course!
And SWLers are not transmitting are they? Really, these specious
arguments do not advance any notion of this being separate issues.
There is nothing in the circularity of logic that demands poorer
transmit antenna designs are better receive antenna designs. Nearly
every beneficial description from your sources cited above lie outside
of the antenna and reside in the coupling or in the receiver. Such
commonplaces are not novel; they are not unique and special knowledge;
and they are certainly not universally applicable.
>How would you undo that 4 dB loss without loss of bandwidth?
That has been responded to above. Loss of bandwidth is a chimera
suited for argument rather than operation. To say it is frequency
agile is the crowning claim for someone who is fain to turn a switch
and set a capacitor in 5 seconds. This isn't rocket surgery, children
learn such techniques within minutes of explanation and faithfully
demonstrate far less loss consistently for ever after.
Further, the usage of a tuner solves many other ills related to noise
and front end overload. The argument of the 9:1 transformer to ease
operation comes at the expense of simple cheap solutions - to no great
benefit, and further, to 4 dB additional loss as you describe. What
boon is to be found in that combination?
I find it laughable that one web site offered claims that a resonant
system is bad for your reception. What a crock! This has all the
logic of buying square wheels to increase your gas mileage.
>I'm hardly
>boasting of martyrdom anyway: a broadband inverted L is a fine general
>purpose receiving antenna.
And what distinguishes it as a poor transmitting antenna? The
inclusion of the engineering decoration of the 9:1 transformer? This
logic is destroyed by a conventional tube transmitter (the original
application suited to this design).
Once again, every issue in relation to even this point is discussed as
a commonplace in this group with simple and cheap solutions that
perform without the concurrent 4dB loss. Such a cavalier attitude of
discarding signal is evidence of purchasing power, not technical
competence.
>>>I've never seen mention of this efficiency/bandwidth tradeoff in the ham
>>>literature,
>>
>>
>> You haven't looked. Either contrived, wholly fictional, or accurately
>> represented, it is part of the stock in trade for selling antennas.
>> In this group, I would wager its discussion consumes more bandwidth
>> than bragging about how many QSL cards have been pasted to the wall.
>
>Examples?
As I offered, you need to look rather than claim. They are so common
that if they escape your attention, no work on my part is going to
satisfy you.
So, the question remains:
>> Do you or others have any actual differentiable discussion, or is this
>> simply an outlet for appoligia for why it isn't worth the strain to
>> lift a soldering iron when you can bench press a credit card?
73's
Richard Clark, KB7QHC
Meindert Sprang
news:mn.ed907d46c...@hotmail.com...
> pse remove the nl newsgroup from this discussion.
Loop niet zo te zeuren Mark1, deze draad is gestart door een Nederlander
(Kees) en ge-crosspost naar twee engelse groepen. Dus dat deze heren hier
steeds weer terugkomen is gewoon deel van de originele discussie.
Meindert
Mark1
Wat een onzin Meindert, ik vraag gewoon of ze deze nieuwsgroep eruit
willen halen, het is en blijft een Nederlandse nieuwsgroep.
De 'draad' is gestart door Kees met reclame maken voor zijn website met
daarop zijn eigen gebouwde antenne, daar staat netjes bij dat hij wel
vragen wilt beantwoorden, nou prima maar dan wel op zijn e-mail adres
graag.
J.W.Siebelink
73 Hans, PA0H
"Mark1" <vonkenboer2004(geen-rommel)@hotmail.com> wrote in message
news:mn.f2327d46b...@hotmail.com...
Mark1
dat dat dus niet het probkeem is, maar wel dat dit een Nederlandse
Nieuwsgroep is en dus de voertaal Nederlands is.
J.W.Siebelink plaatste dit op zijn scherm :
Mark1
>> Als je mijn vertaling van het stukje babbelfish hebt gelezen weet je
>> dat dat dus niet het probkeem is, maar wel dat dit een Nederlandse
>> Nieuwsgroep is en dus de voertaal Nederlands is.
>
> groepen uit de lijst, dus jij zit nu Nederlands te lullen in een
> engelstalige nieuwsgroep.
>
> De pot verwijt de ketel...
>
> Meindert
Dit is niet de pot verwijt de ketel, enkel het laten zien aan de
engelstalige nieuwsgroeppen hoe hindelijk het is als er iemand in een
andere taal schrijft, als ze het dan proberen te vertalen in babbelfish
of een andere vertaalprogramma zullen ze zien dat er geen barst van
klopt.
Vandaar dat ik nu dus weer die engelstalige groepen die jij eruit hebt
gehaald erbij heb gezet :-P