| |
G8MNY > TECH 20.03.04 00:49l 100 Lines 4506 Bytes #999 (0) @ WW
BID : 49002_GB7CIP
Read: DB0FHN GUEST OE7FMI
Subj: Petrol Generators for /P SSB 1/3
Path: DB0FHN<DB0FOR<DB0MRW<OK0PKL<OK0PPL<DB0RES<ON0AR<7M3TJZ<IK1ZNW<GB7CRV<
GB7CIP
Sent: 040319/2142Z @:GB7CIP.#32.GBR.EU #:49002 [Caterham] $:49002_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (new 12/03)
/P POWER NEEDS
A generating set capable of handling several 400W SSB stations at once is very
uneconomical. This is because a typical constant RPM engine & alternator uses
about 30% of it's energy just to overcome the mechanical losses, cooling etc,
as well as the alternator exciting & cooling needs.
Using under rated generator sets is more economical, but obviously very prone
to regulation problems on peak load.
LOAD SHARING/conditioning
By floating a car battery on small power source very large peak power can
easily be drained for SSB work. eg 200W SSB needs 30A peak, & 10A PSU will
easily cope with that. But this is not so good for high power FM, but the
battery will still recover on Rx.
ÚÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄ¿ 13A FUSE 40A FUSE ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ SMALL ÃÄÄ´PSUÃÄÄÄo\oÄÄÄÄÄÄÂÄÄÄÄÄo/oÄÄÄÄ´RIG & QRO PA³
³GENERATOR³ ÀÄÄÄÙ ÚÄÄÄÁÄÄÄ¿ ÀÄÄÄÄÄÄÄÂÄÄÄÄÙ
ÀÄÄÄÄÂÄÄÄÄÙ ³BATTERY³ _³_
_³_ ÀÄÄÄÄÄÄÄÙ ////
////
Ensuring that no Tx station sharing a generator, has to run full carrier power
for tuning up by using "werlos" (not whistles) & PEP meters, can solve
excessive mains dips on heavily loaded generators enabling several 400w SSB
stations to be run from a single 1.5KW generator.
FULL POWER CW/Whistle "WERLO" POWER
400W´-------- - - - MEAN 400W´ -, , - - - PEAK READING METER POWER
200W´ 200W´/' ³ / \ _ _ _ mean power
100W´ 100W´. ³ / ³ generator load!
50W´ 50W´ ³/
25W´ 25W´ ³
0 ÁÄÄÄÄÄÄÄÄ 0 ÁÄÄÄÄÄÄÄÄÄÄ
TIME TIME
eg. 400W station needs 800W DC I/P (class AB2) for full carrier tuning up, but
only 450W DC for spoken "werlo" 400W PEP tuning up.
MAGNETOs
Small generators having no start battery, use magneto ignition, which is housed
in the flywheel. Powerful magnets are built into the flywheel & pass over a
static coil.
SPARK===, __________ IGNITION
PLUG )|( ³ ³ TIMING
)|( C === >< POINTS
MAGNETOÀÄ´ ÀÄÄÄÄÄ´
_³_ _³_
//// ////
The engine axle has a cam on it that operates a set of shorting contacts called
"points". Variable speed engines will have a movable cam, but not constant RPM
generators. These points short out the primary coil with a condenser (0.5uF
high voltage capacitor) across the points as well. The points are arranged to
open a few degrees before "Top Dead Centre", when the magnets are also across
the coil. As the points open the magnetic flux is allowed to enter the coils, &
soon produces a decaying oscillation with the condenser. A second high voltage
coil (that can be an external Ignition transformer coil), produces 15-25KV to
power the spark plug.
SPARK===, __³\³_____________
PLUG )|( ³/³ +ve ³ ³ TIMING
)|( NPN\³____R_³³_____ PULSE
MAGNETOÀÄ´ e/³ _³_ ³³ -ve )³ PICKUP
³ ³ /_\ )³ COIL
_³_ _³_ _³_ _³_
//// //// //// ////
Electronic types replace the points with a high voltage transistor/FET that is
self biased on with a R when the magneto magnet passes trying to produce a +ve
voltage. A separate induction timing pickup coil & small magnet on the
crankshaft produce a precise turn off timing pulse, resulting in the short of
the magneto primary winding being removed & the magnet flux suddenly being
allowed to enter the coil to produce the high voltage.
IGNITION QRM
On a busy band (contests) it is undesirable to use Rx noise blankers to remove
generator ignition noise, as this normally makes the larger band signals very
wide. Instead suppress the ignition noise with a some large coax braid placed
over the ignition lead & earthed only at the cylinder head!
ÄÄÄÄÄÄÄÄ¿
³ÄÄÄÄÄ¿ _ÄÄÄÄÄÄÄ¿ COAX BRAID
CYLINDER³SPARKÀÄ¿ ³ PLUG ³ ================= EHT
HEAD ³PLUG ÚÄÙ_³ CAP ³::::::::::::::::::::: LEAD
³ÄÄÄÄÄÙ ÄÄÄÄÄÄÄÙÚ=================
BOLT³0================Ù AS LONG AS
ÄÄÄÄÄÄÄÄÙTAG TWISTED COAX BRAID POSSIBLE
Suppressing plugs & screened caps are also available, but resistive lead as
used on cars is not normally possible due to the magneto lead connection.
Part 2 has Economy, Alternators, & Regulation.
/QSL
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
