G8MNY > TECHNI 07.10.21 11:00l 88 Lines 3706 Bytes #999 (0) @ WW
BID : 48821_GB7CIP
Subj: Inverter Petrol Generators
Sent: 211007/0845Z @:GB7CIP.#32.GBR.EURO #:48821 [Caterham Surrey GBR]
To : TECH@WW
By G8MNY (Updated Jan 14)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
N.B. THESE ARE NOT SUITABLE FOR SENSITIVE MF/HF HAM WORK!
At a recent summer camp we tested out a new 2.2kW generator...
.==˙'(__) │ Modern electronic inverter type
/ │ generators (Honda/Clark) produce
Ů  : ° ° │ excellent stable power output, with
│ │ good sine wave under heavy changing
│° │ rectified mains loads. (e.g. 400W SSB Tx Valve PA)
Unlike conventional generators that run at a constant 3000 RPM, the inverter
type can tick over quietly at low revs & save energy (fuel) under light loads,
& rev up to well over 3000 RPM (e.g. 500-10000 RPM). The higher revs means a
lighter smaller CC engine is used. But it is still quite noisy at full load!
┌────────────┐ 380V DC ┌──────────────┐ ┌───────────┐
│HIGH VOLTAGE├───┬──────┬──┤L & N HF PULSE├─┤GENNY MAINS├──>230V
│ ALTERNATOR │ │ C === │ WIDTH SINE │ │ FILTER │ 50Hz
└────────────┘ \│/ │ │ WAVE INVETER │ └─────┬─────┘ SINEWAVE
Engine └──────────────┘ _│_
Speed Feedback 10kHz-50MHz ///
The engine throttle feedback is used to maintain the high voltage DC. A large C
ensures there is enough DC stored to meet the sudden demands until the engine
You don't get something for nothing. The genny mains filter used to clean up
the output is quite good for domestic/industrial use, but not LF/HF work! The
inverter produces LOTS of broadband noise with a slight buzzy hum content.
EXTRA MAINS FILTERING
The interference mode to the Rx was found to be "common mode" via the mains to
PSU & PA etc, & not radiated to the nearby balanced aerials. (to the limit of
band noise floor).
Tests were done at a quiet /P site with HF Rx Preamp ON, with various mains
filters showed on the S meter something like this..
Genny None Normal -------------- Inverter Type Genny with ----------------
On 4 stroke No Plug Plug Large Both Earth Filter with
Band Batt Genny Filter Top Top x2 Filter Filters Only Earth Choke
20m S1 S1 S7 S4 S3 S3 S2 S6 S2
40m S2 S2 S9 S5 S4 S5 S4 S8 S3
80m S3 S3 S9+ S5 S4 S6 S4 S9 S4
The "Normal 4 Stroke Genny" had fully suppressed ignition. The "Plug Top"
filter was old BT type, & the "Large Filter" was a huge "brick" sized standard
motor type. As they performed slightly differently, they were also tested
together "Both" for a slight improvement over either one.
The tests with "just the earth wire" connected, proved there was quite a bit of
conducted RFI on it & a mains filter with an earth choke would help. One was
found, wired up & tested.
INVERTER = = = === │ LOAD
GENNY N────())))────┬─┴──(─────> N
─┬─ E──────(((()──┴────┴─────> E ┬
_│_ F I L T E R _│_
/// Genny /// RF Earth
The choke in earth filter, did work the best of all the filters tested, but the
QRM is still well above the GOLD STANDARD of no added noise! An end fed wire
for 160m was also a lot worse!
See also buls on "Mains Plugtop Filter Adapter", "Cheaper Generators",
"Regulating 12V Generator Output" & "Madusa SIP 2300 Generator Repair"
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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