"How far" does 1 milliwat (and 1 watt) go?
Michael Barney
transmissions.
I seem to recall some "Hamfest" communications going 100's or thousands
of miles on less than 1 watt transmit power (and not at microwave
frequencies w/ large Parabolics either).
I'm specifically looking for "how far" on "how little power" under
*relatively ideal conditions* for 1 milliwatt and 1 watt.
Thanks in advance,
Direct reply or post appreciated,
Michael Barney
mi...@tdc.dircon.co.uk
Paul H. Bock
>Could anyone enlighten me on "low power contest" for distance
>transmissions.
>I seem to recall some "Hamfest" communications going 100's or thousands
>of miles on less than 1 watt transmit power (and not at microwave
>frequencies w/ large Parabolics either).
>I'm specifically looking for "how far" on "how little power" under
>*relatively ideal conditions* for 1 milliwatt and 1 watt.
As early as the 1920s, a U.S. ham set a record for a U.S. to
Australia contact using the (then fairly new technique) CW mode.
(Note: By "new technique" I mean the use of continuous waves as
opposed to spark. Today, "CW" to most hams means "radiotelegraphy"
but *spark* was radiotelegraphy, too. Don't be confused.)
The *input* power was less than 1/2-watt; I'll dig up the info
tonight and bring it in. It's in the book "200 Meters and Down"
which was publihed in 1936.
Since that time, many QRPers have made contacts with only a few
milliwatts, and probably microwatt contacts as well when using
directional antennae.
(|_|) Paul H. Bock, Jr. K4MSG Internet: pb...@melpar.esys.com
| |) Principal Systems Engineer Telephone: (703) 560-5000 x2062
"You can have my bug when you can pry my cold, dead fingers from
around it....." - anonymous radiotelegraph operator
r...@vectorbd.com
: Could anyone enlighten me on "low power contest" for distance
: transmissions.
: I seem to recall some "Hamfest" communications going 100's or thousands
: of miles on less than 1 watt transmit power (and not at microwave
: frequencies w/ large Parabolics either).
: I'm specifically looking for "how far" on "how little power" under
: *relatively ideal conditions* for 1 milliwatt and 1 watt.
Well, 1 watt at microwave frequencies aren't going to get you as
far as at HF, no matter how large your antenna. :-)
I've never run more than 4 watts in the 1.5 years that I've had
my licence, and usually stay down at about 1 watt unless conditions
are *REALLY* bad. :-) My contacts average out to about 400+ miles
on the 40M band, although my longest-range contact was approximately
2800 miles with 2 watts. It's not unusual for dedicated QRP
enthusiasts to get several thousand miles per watt.
So, in short, you can work around the world if you have patience,
a good antenna, and someone who is willing to dig your peanut-whistle
signal out of the noise.
- Rich
Jeffrey Wittich
|> Could anyone enlighten me on "low power contest" for distance
|> transmissions.
|>
|> *relatively ideal conditions* for 1 milliwatt and 1 watt.
|>
|> mi...@tdc.dircon.co.uk
Hi Michael. My first DX contact was made from here in Raleigh NC
to the Canary Islands on February 15, 1993. Thats 3600
miles great circle route. Output power was 700 mw to a dipole
up 18 feet. Freq was 14.031 mhz and time was about 0240z.
10 cm Solar flux index was about 88 and the K index was 1. He
gave me a very weak signal report but did not require any
repeats.
Never got his card though (sigh). He was EA8QJ.
Hope this helps, 73.
Jeff
--
*******************************************************************************
jwit...@b4pph107.bnr.ca *** CW ops let their fingers do the talking.
AC4ZO *** BNR claims they know nothing of my employment here.
*******************************************************************************
Paul H. Bock
>Michael Barney (mi...@tdc.dircon.co.uk) wrote:
>: I seem to recall some "Hamfest" communications going 100's or thousands
>: of miles on less than 1 watt transmit power (and not at microwave
>: frequencies w/ large Parabolics either).
>: I'm specifically looking for "how far" on "how little power" under
>: *relatively ideal conditions* for 1 milliwatt and 1 watt.
> I've never run more than 4 watts in the 1.5 years that I've had
>my licence, and usually stay down at about 1 watt unless conditions
>are *REALLY* bad. :-) My contacts average out to about 400+ miles
>on the 40M band, although my longest-range contact was approximately
>2800 miles with 2 watts. It's not unusual for dedicated QRP
>enthusiasts to get several thousand miles per watt.
> So, in short, you can work around the world if you have patience,
>a good antenna, and someone who is willing to dig your peanut-whistle
>signal out of the noise.
From "200 Meters and Down" by Clinton B. DeSoto, published in 1936,
page 112:
"But this paled before the performance of Loren G. Windom, 8GZ-8ZG,
of Columbus, Ohio, who on December 30th (1925) communicated with (Henry A.)
Kauper, a5BG (of Dulwich, Adelaide, South Australia) using an input of only
0.567 watts to a UV-199 receiving tube! With the distance given as 10,100
miles, this figured out to be 17,820 miles per watt. On January 3, 1926,
contact was established with Major J. G. Swart, oA6N, in Capetown, South
Africa, using 0.54 watts input. On February 28th, 8GZ worked George H.
Shrimpton, z2XA, in Wellington, New Zealand, a distance of 8500 miles,
with 0.493 watts input, giving 17,250 miles per watt. A filament poten-
tial of 4 volts was applied to the UV-199 tube during these tests, and
a plate voltage from 70 to 75. So far as is known, these completely
incredible records - in which much less power was used than is consumed
in the ordinary flashlight bulb - still stand unbroken."
Two comments: First, I didn't check the *frequency* used for these
tests, but it was most likely 20 meters (possibly 40 at night). Of
course, there was no QRM in those days and very little electrical
interference, so receiving conditions must have been stupendous
compared with today. Second, recall that *wire* antennas were the
norm in those days - no big yagis on towers with rotators!
BTW, does the name "Windom" ring a bell? Was 8GZ "the" Windom, or
is that just a coincidence?
Scott Richard Rosenfeld
More correct is to wonder how far an E-M wave of a certain power
can travel.
Say you're transmitting 1 watt to a real "isotropic" radiator.
Your "power flux" is then 1 watt/(4*pi*r^2), or the power radiated
divided by the surface area of the sphere at some given distance.
By determining that some solid angle containing power will direct
to your desired location, you can figger out just how much power is
going into the ionoshphere along your desired path. Chances are
PRETTY GOOD that not all of that 1 watt is going along the desired
path...
Now use a beam. Integrate over the beamwidth that's going in the
direction of the skip, and you'll find that considerably more power
than with the isotropic radiator is going in the desired direction.
So if you've got a 10 dbi antenna, you need 1/10 the power to
achieve the same results if it's pointed in the right direction.
I've been heard in OK/OM on 3 watts to a dipole with a 6 element
monobander on the other end...
And don't forget about "effective gain" of CW over phone, either.
SSB carries more information, but must spread the power out over
a wide spectrum in order to do so. CW has a very narrow BW...
--
73, _________ _________ The
\ / Long Original
Scott Rosenfeld Amateur Radio NF3I Burtonsville, MD | Live $5.00
WAC-CW/SSB WAS DXCC - 130 QSLed on dipoles __________| Dipoles! Antenna!
hamilton on BIX
This talk of distance/watt records has me thinking: it certainly
isn't amateur stuff, but aren't all the real QRP records held by
the space probes? Voyager was transmitting back to earth out
beyond Jupiter! And wasn't that on only a few watts?
'Course, it DID take a hell of antenna back here. I trust you've
all seen pictures of Aracebo!
Regards,
Doug Hamilton KD1UJ hami...@bix.com Ph 508-358-5715 FAX 508-358-1113
Hamilton Laboratories, 13 Old Farm Road, Wayland, MA 01778-3117, USA
Ross Alexander
> Second, recall that *wire* antennas were the
>norm in those days - no big yagis on towers with rotators!
I'll take a proper rhombic over a yagi any day. It's a wire antenna
with an attitude! On 20m, they aren't even all that big. Terminated
rhombics are lovely broadbanded creatures, unlike yagis.
I seem to recall that the rhombic has a long history; that's why the
ARRL logo is shaped the way it is. So a QRP'er using them in the
mid-20's wouldn't surprise me.
regards,
Ross ve6pdq
--
Ross Alexander VE6PDQ r...@cs.athabascau.ca,
(403) 675 6311 r...@auwow.cs.athabascau.ca
Television is chewing gum for the eyes. -- Frank Lloyd Wright
Ed Hare (KA1CV)
/125 event -- a blast!!!), I was using 250 milliwatts to get my Worked All
States award. One day I was chatting with a ham in Florida (sure wish I
remembered his call!), who was running 100 watts. When he heard I was 250
mW, he decided to drop power, too.
He cut back to 50 watts, whereupon I told him I couldn't tell the
difference. He then cut back to 10 watts, then 5 watts, then one watt. At
the latter I told him he was down to only 10 dB over S9! He then came back
to me at RST 579 and said that he couldn't even see his power meter moving.
I told him he was still Q5.
Then he told me to wait. About 15 seconds later he was in there, as weak as
I could imagine. I copied most of what he had to say, but told him he did
have to increase the power as he was only about Q3 and I was having a real
hard time. He came back with the CW HI HI, and told me that I had just
copied 5 watts into his dummy load.
I think we both learned something that day. :-)
73 from ARRL HQ, Ed
--
Ed Hare, KA1CV, ARRL Laboratory, 225 Main, Newington, CT 06111
203-666-1541 eh...@arrl.org
bre...@cruzio.com
> This talk of distance/watt records has me thinking: it certainly
> isn't amateur stuff, but aren't all the real QRP records held by
> the space probes? Voyager was transmitting back to earth out
> beyond Jupiter! And wasn't that on only a few watts?
> 'Course, it DID take a hell of antenna back here. I trust you've
> all seen pictures of Aracebo!
You don't even need Arecebo. In the book FIRST CONTACT, author/hams
Cullers and Alschuler describe an amateur SETI station composed of a
3-4 meter dish, an ICOM 7000, a GaAs FET amplifier providing a system
noise temperature of about 100k. With a digitizer board and a computer
software capable of Fourier Transform spectrum analysis you would have
a competent system.
The authors recommended using Voyager II (then at about 30 A.U. from
Earth) broadcasting at 20 watts on 8 GHz as a test target! I wonder if
anyone actually did this?
Now when someone actually picks up ETI, that will probably set a few
interesting records. ;@} And who said microwave wasn't good for DX? ;@}
--
Brett Breitwieser (bre...@cruzio.com)
Clinical Hypnotherapist (Certified by the National Guild of Hypnotists)
Director, Axis Mundi: *Axis Mundi* as the Image of *Proto Phallos*
Member, Therapists for Social Responsibility
Shawn C. Masters
: I seem to recall some "Hamfest" communications going 100's or thousands
: frequencies w/ large Parabolics either).
: I'm specifically looking for "how far" on "how little power" under
: *relatively ideal conditions* for 1 milliwatt and 1 watt.
It's not a matter of how far will your signal go, but who can
receive it at what distance. Their Noise Figure plays a large part in
determining how small of a signal they can receive. If your signal is
10^-23 Watts and their noise at the input stage and first amp is roughly
the same, then they probably will only be able to get real crappy CW through,
if that. If your signal is say 10-20dB higher (I know that's two orders of
magnitude), then you can get a large data rate at a low Probability of
bit error.
So the question is, does the liquid helium to cool the front end
become more practical then the antenna array for QRP operations:-).
73,
Shawn
KE4GHS
jdow on BIX
> 73,
> Shawn
> KE4GHS
Here is a quicky analysis I just posted to Delphi tonite:
3397 10-OCT 03:42 General Information
RE: QSO's from aircraft (Re: Msg 3376)
From: JDOW To: BUMPKIN (NR)
Figure sensitivity of 0.3uV (-117dBm), transmitter of 5 watts (+37dBm), and
HT antennas (maybe -2dB or -3dB gains.) Path loss is 36.6dB + 20log(freq)
+20log(dx) with freq in MHz and dx in miles. Let's figure 2 meters for grins.
That is about 43dB for the frequency. So 43+37+20log(dx)+5 = 37-(-117) = 154dB.
85+20log(dx) = 154 -> 20log(dx) = 69dB. Or dx = 2800 miles. Of course that
assumes pure line of sight. And at 450MHz you drop to about 930 miles all other
things being equal.
Yeah - those little things can go a LONG ways when conditions are right.
{^_-}
{^_^} Joanne Dow, Editor Amiga Exchange, BIX
jd...@bix.com
Zack Lau (KH6CP)
: Michael Barney (mi...@tdc.dircon.co.uk) wrote:
: : I seem to recall some "Hamfest" communications going 100's or thousands
: : of miles on less than 1 watt transmit power (and not at microwave
: It's not a matter of how far will your signal go, but who can
: receive it at what distance. Their Noise Figure plays a large part in
: determining how small of a signal they can receive. If your signal is
: 10^-23 Watts and their noise at the input stage and first amp is roughly
: the same, then they probably will only be able to get real crappy CW through,
: if that. If your signal is say 10-20dB higher (I know that's two orders of
: magnitude), then you can get a large data rate at a low Probability of
: bit error.
: So the question is, does the liquid helium to cool the front end
: become more practical then the antenna array for QRP operations:-).
Liquid Helium is only useful in the microwave spectrum. The background
noise temperature at 144 and lower frequencies is too high to derive any
significant benefit from cooling your preamp (room temperature designs can
exhibit 0.2 to 0.3 dB NF, if cost is not a factor). To obtain a low
system noise figure, not only must you have a low noise preamplifier, but
you must also have an antenna with a clean pattern that isn't pointed at
any warm objects (milky way, the sun, the ground....). The professionals
do this with huge horn antennas.
--
Zack Lau KH6CP/1 2 way QRP WAS
8 States on 10 GHz
Internet: zl...@arrl.org 10 grids on 2304 MHz
Ken A. Nishimura
>
>Figure sensitivity of 0.3uV (-117dBm), transmitter of 5 watts (+37dBm), and
>HT antennas (maybe -2dB or -3dB gains.) Path loss is 36.6dB + 20log(freq)
>+20log(dx) with freq in MHz and dx in miles. Let's figure 2 meters for grins.
>That is about 43dB for the frequency. So 43+37+20log(dx)+5 = 37-(-117) = 154dB.
>85+20log(dx) = 154 -> 20log(dx) = 69dB. Or dx = 2800 miles. Of course that
>assumes pure line of sight. And at 450MHz you drop to about 930 miles all other
>things being equal.
>
>Yeah - those little things can go a LONG ways when conditions are right.
>{^_-}
>
>{^_^} Joanne Dow, Editor Amiga Exchange, BIX
> jd...@bix.com
Well, let's do this for the generic case. Assume 50 ohm signal source
and 290K temperature. The 1 Hz noise power is -174 dBm due to Johnson
or thermal noise. The above path loss formula is correct. You can
figure out your own Tx and Rx antenna gains and Tx line losses. The
recevier sensitivity is then:
-174 dBm + 10 log (BW) + C/I + F
where BW is bandwidth of the receiver (noise BW) in hertz,
C/I is the required Carrier to Interference ratio needed, and
F is the receiver noise figure (the TOTAL receiver, not just the LNA).
C/I can be around 0 dB for OOK (CW) signals, 1 to 2 dB for wideband FM,
3 to 4 dB for NBFM, and as high as 10-12 dB for AM. Note that you get
audio SNR to C/I gain with FM and none with AM.
F is typically in the range of 5 to 10 dB. A good communications receiver
has a F of about 6 dB, with most commercial stuff around 8 dB. Your HT
and cellphone are probably around 7 to 8 dB.
So, if your received power (Tx power + Tx AG + Rx AG - Path Loss - TxLine
losses on both sides) is greater than your sensitivity, you get a QSO.
Consult a communications textbook for exact formulae required for C/I
for various systems.
==ken
Shawn C. Masters
: Liquid Helium is only useful in the microwave spectrum. The background
: noise temperature at 144 and lower frequencies is too high to derive any
: significant benefit from cooling your preamp (room temperature designs can
: exhibit 0.2 to 0.3 dB NF, if cost is not a factor). To obtain a low
: system noise figure, not only must you have a low noise preamplifier, but
: you must also have an antenna with a clean pattern that isn't pointed at
: any warm objects (milky way, the sun, the ground....). The professionals
: do this with huge horn antennas.
I wasn't thinking about 2 meters, even though the original article
had posted it. Thanks for correcting the oversight. Although I think the
background noise is low enough to allow cooling to benefit the UHF band. It
may not be much of a gain, but some should be available.
73,
Shawn
KE4GHS
David Stockton
: Now when someone actually picks up ETI, that will probably set a few
: interesting records. ;@} And who said microwave wasn't good for DX? ;@}
Yeah, but the contact won't be good for anything until the cards
arrive !
How big an envelope will be needed to get the right number of green
stamps to fit in ?
Cheers
David GM4ZNX