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DL4YHF > VLF 08.09.97 16:01l 50 Lines 1736 Bytes #-10535 (0) @ DL
BID : 08971EDB0EAM
Read: GUEST
Subj: LF-TX, english short description
Path: DB0KCP<DB0ZKA<DB0ABH<DB0SRS<DB0SIF<DB0NHM<DB0FC<DB0EAM
Sent: 970908/1331z @:DB0EAM.#HES.DEU.EU [Kassel DB8AS] $:08971EDB0EAM
de DL4YHF @ DB0EAM.#HES.DEU.EU (Wolfgang)
to VLF @ DL
FROM: DL4YHF @ DB0EAM.#HES.DEU.EU
TO: VLF @ EU
Hello VLF - experimenters,
yesterday i sent a circuit diagram and a short description of a
homemade LF-transmitter to the "VLF" - Bulletin in germany.
This morning i received orders for correction files, not only from
germany, but also from scandinavia. Something must have gone wrong
when sending it via S&F !
So my apologies to all of you who downloaded the useless description
(in german language). My intention was first to test the circuit in
germany by experienced home-brewers.
I will try to create a "nice" layout for a printed circuit board
(single-sided) and spread it via VLF @ EU when the work is finished.
For those of you who want to know what that .GIF - file is all about,
here a short description of the transmitter:
- frequency synthesis with an LC-Oscillator running at 2.2 MHz, followed
by a frequency divider (division by 16)
- semi-BK-circuit for RX/TX-switching with a relais
- pulse-with-modulator used to create "soft" keying edges
(to aviod "clicks")
- final stage with power-MOSFET (BUZ 71 A, BUZ 11 , IRF 640 , ... )
in switching-mode giving quite good efficiency
but requiring good filtering !
- narrow-band impedance-transformation with a serial-resonant circuit
- additional rejection of harmonics with a PI-filter
- integrated SWR-Meter
(measuring of forward and reverse flow at the same time)
- protection of the PA-Transistor by reducing the output power
if the SWR is too high
- output power is about 20 watts after filtering
hope to see you on 137 kHz one fine day...
73's de Wolf(gang), DL4YHF @ DB0EAM.#HES.DEU.EU
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