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- Subj: LOWfer "RB" 186.92 kHz transmitting CW
Date: 6/25/99 4:09:10 PM Eastern Daylight Time
From: bicking mwci (rbicking)
The new Litz wire loading coil is installed and "RB" is back on the air 24 hours and 7 days (except when it interferes with my pursuit of DX on the ham bands or when we are getting a big storm). The current to the class E final went up by more than 3 times (at a constant voltage) compared to the small ferrite tuned loading coil I had previously used. I'm planning a Lowdown article to help people get on the air with a good signal while using a fairly simple antenna like mine.
73, Robert Bicking, W9RB
- Subj: loading coils
Date: 99-06-18 08:26:43 EDT
From: rikstrobbe fyskuleuvenacbe (Rik Strobbe)
When starting on the European 136kHz band I constructed a huge loading coil
with a lot of 'taps' to be able to experiment with various antennas.
The coil did a good job but now I got the (for the moment) final version of
my antenna and want to build a new coil with lower loss.
The 'old' coil was made of 1mm solid CuL wire, gives inductance between 1
and 5mH (in 15 steps, fine-tuned with a small variometer in series) but Q
is only about 130 (probably due to not-so-good diameter/length ratio and
lot of soldering).
So the first question that came up was what wire to use ? The real
Litz-wire is definitely the best, but hard to find and very expensive (and
I would need more than 150 meter).
I decided to do a little test with 1mm and 2mm solid CuL wire : with both
types I made a small 200uH coil on a 10cm PVC former. The result was
dissapointing as for the 1mm CuL I got a Q of 230 and for the 2mm CuL a Q
of 280. Taking into account that the weight of the 2mm CuL coil was over 5
times that of the 1mm CuL coil (and since the CuL wire is sold per weight
also the cost was 5 times higher), hardly worth the slight increase in Q.
So I have to find another way to build my new coil than just using thicker
CuL wire.
An idea that crossed my mind was to make my own 'semi-Litz' wire by
twisting a number of 0.5mm CuL wires. The 2mm CuL wire could be replaced by
16 times 0.5mm (same weight). So my question is : will this improve the Q
significant (in theory YES, but does someone have practical experience) ?
Other questions that came up are :
1. Is 'flexible' wire (non-isolated strands) better suited to counter the
Skin-effect than solid wire of the same diameter (in theory NO as the
strands are not isolated, but what says practice) ?
2. What is the optimal diameter/length ratio of a coil (taking into account
the Q and the copper-weight) - I am talking about a coil in the 2-3mH range ?
As it is rather time and money consuming to build serveral of these big
coils to see what is working and what not I appreciate any advice
(especially based or pracical experience).
73, Rik ON7YD
Villadreef 14 B-3128 Baal BELGIUM (JO20IX)
- Subj: signal reports Hartley Shannon
Date: 99-06-16 14:55:42 EDT
From: wolfgar123 hotmail (Edgar Heinen)
sirs:
My name is Edgar Heinen and am wondering if anyone is familiar with
the Hartley-Shannon law which dictates how well a signal can be heard,
if sig. bit rate is known, and sig-noise. You have a feature of VERY
slow cw on your website. If the bit rate is say 0.1 or 0.001 bit/sec
can you still apply this law? I guess it applies to aurally copied cw.
Noise is expressed in power per 1 hz. If sig is -20 db below Noise
and bit rate is 0.001 b/sec, can one copy this? The passband would be
normal,no narrow filtering used, like 2-4 kc.
Ed
- Reply 1: I know of Prof. Shannon's work in information theory on other levels, but I can't say that I am familiar with the details of this principle; perhaps some of our other readers would care to comment. I can attest, though, that one will not be able to copy a very slow CW signal of the sort described against noise of such magnitude in that bandwidth, by ear. A more frequency selective system than the human ear, capable of integrating both signal and noise over a longer time frame, is needed. Though the ear can discriminate quite sharply between keyed tone and random noise at roughly syllabic rates, its ability to integrate over longer time frames is very poor. - JHD
- Subject: QSL?
Date: Sat, 05 Jun 1999 23:25:48 -0400
From: "Andre' Kesteloot" (akestelo bellatlantic )
The AMRAD Beacon is now operational 24 hours a day, 7 days a week
(except during power cuts, of which we have had a few in recent weeks) We transmit on 136.750 kHz. with about 170 watts RF into a "T"
(Marconi) antenna.
The message sent continuously at 5 wpm is "vvv de wa2xtf/6 qsl via
n4ick at amrad.org ar" followed, for signal/noise calibration
purposes, by a long dash and a silence.
In the future, we will alternate between CW and BPSK transmissions.
If you can hear us, we would appreciate that you QSL c/o n4ick amrad.org
- Subj: Damage Report
Date: 99-06-05 14:25:43 EDT
From: okbill brightok (William Bowers)
Thanks to the unexpected windfall (of an insurance settlement on the spring storm damage), I got some new Litz wire and have built
a new 10 foot loop. This time I used a 4" PVC center pipe and mounted it
four feet lower. This should survive the frequent 50 MPH winds that with out
extra guy ropes.
For "OK", I have ordered a 45 foot aluminum tower from Universal
Towers. I am going to use an idea from Bill Cantrell and mount it upside
down on a insulator.. If every thing goes according to plan, OK (V2.0),
should be on the air by the end of July.
Bill Bowers
- Subj: RL
Date: 99-06-05 13:40:03 EDT
From: RLLaney aol
RL is off the air for the summer, at least, maybe longer. Its performance has been disappointing, so I
need either to make improvements in the antenna or forget it and just
concentrate on improving my receiving capabilities. One encouraging aspect
is that we had a nearby almost overhanging tree cut down recently. This may
now allow some stringing of some horizontal wire and a whole new antenna
design. I wax and wane about this crazy
hobby, but it is hard to get away from completely!
Best regards,
Bob
www.lwca.org
potrzebie