Amateur radio station since 1993
RA3WDK `s Homepage
How make Flag and Preamplifier + some Life Hacks
Bi-Directional Flag 160/80m band on Club Station RA3W
Test temperature of AD8129 chip
Is importante, if you overload chip or chip is fake (beware to buy chip on Ebay from China) Temperature must be not more 45C degree
For protection from water need to use acryl Plastik by CRAMOLIN
Cramolin plastik is a transparent acrylic resin designed to be sprayed on your electronics components, PCBs, wires and cables. The conformal coating forms a flexible protective film to protect your components from acids, salt, alkalis, alcohol, fungus and other tough conditions in the environment.
How use Silica Gel for adsorb water and decrease humidity in box.
Attention - Silica Gel specifically designed for adsorb water and use far of food products! Silica gel packs should NOT GO NEAR FOOD. In addition, some types of silica gel designed to change color to indicate they water content (as in if they are full) contain several carcinogenic chemicals (cobaltous chloride)!
Silica Gel with humidity indicator - blue color - is OK , pink - need change adsorber. Adsorber is easy to recovery by heating to 100 С about 4-6 hours.
How make inductive choke in injector (150-200uH)?
I use Home made instrument transformators for tune and measure preamplifier and balance filter
Very useful thing (Core from TV CRT direction system) for making feed choke
About 12 turn of coaxial cable give 100 uH
So much better Common-mode current chokes with EPCOS core inside
Old version Injector inside
First swith switches Flags (N/S flag or W/E flag for example), second swith switches the direction for each flag
(S or N for N/S Flag ... or E or W for W/E Flag)
Filters for preamplifier
Spectr evening with about -40 dbm level of SW BC band (with filter LPF 1.8 MHz)
Biggest level of SW BC station from west direction (power SW station in South Europe)
Spectr from 0 to 10 MHz 1 hours before sunset (near Gray Line) with filter
Spectr of preamp with filter for 2 hours after sunset, west direction, max level HF BC station -45 db about 6 MHz
Differential filters for preamplifier
Balanced bandpass filter (BBPF) with stable bandwidth from 400 to 900 Ohm for 160 m Bi-Directional Flag and PreAmp
Narrow Balanced bandpass filter (BBPF) with stable bandwidth from 400 to 900 Ohm for 160 m Bi-Directional Flag and PreAmp
Balanced bandpass filter (BBPF) with stable bandwidth from 400 to 900 Ohm for 80&160 m Band
Real frequency response of BPF 160m by transformer 1:9 in input of preamplifier
BPF 160m for 800 Ohm has been simulate by Electronic Workbench
LPF 160m for 800 Ohm has been simulate by Electronic Workbench
LPF 80m for 800 Ohm has been simulate by Electronic Workbench
Real frequency response of LPF 160/80 m and LPF 160 m Band by transformer 1:9 in input of preamplifier
I recommed those LPF filter for preamplifier
Before Front-End my SDR i use additional filter for 160-80m Band
Old Version injector for Bi-Directional Flag
Shield current choke for suppression current in shield of feed from my Magnetic Loop. About 30 db loss on 3,5 MHz for current on shield of feed to my Magnetic Loop. Very BroadBand Common-mode current chokes from 1 to 50 MHz
RF transformer with separate coil and only connection by magnetic field
Loss and SWR in transformer, look here for 1,8 and 3,5 MHz
Isolation between two coil by capacity with grounded shield of transformer
Isolation between two coil by capacity without grounded shield of transformer