Last weekend we secured a potential new contest site. So now it's time to test & verify new RX antennas.
First stage: compare high performance beverage antennas.
From the junk-closet I digged out some 4 similar built beverage boxes. We need 5 pcs for the stage 1 test, so I used this evening to copy cat a final 5th one. I have used this type of box from 1990 onwards, and this is the latest portable version. These are very comfortable for field day style use.
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Above picture shows two finalized beverage connection boxes. These consist of the following parts:
- TEKO plastic box with alum top cover
- Connection terminal with both wire and banana plug entries
- BNC female chassis part
- 4x M3 bolts & nuts
- Silver coated 3mm solder lug
- Teflon coated wire
- Binocular ferrite type 73
- Hot glue
- Wet Basis Protect performance spray
- Liquid tape
The balun consists of 6 primary windings and 2 secondary windings using thin teflon coated hookup wire.
Hot glue is used to fixate the balun. This avoids broken wires when the box drops on a concrete floor.
The Wet Basis Protect performance spray protects electrical components against moisture- and humidity-related short circuits, malfunction and corrosion. It prevents subsurface penetration of moisture and performs a permanent protective film. I have used this for 2 years now and it has shown great performance on outdoors applications. It is sprayed on all metal parts in- and outside of the box.
The liquid tape is used to protect the M3 bolts and the box from moisture via the BNC chassis connector.
Test & verify and re-test again
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There is no room for building errors in our next RX antenna experiment. I need to be absolutely sure the beverage connection boxes work as predicted.
The antenna analyzer shows a flat response from 1.5Mhz (start freq. of the analyzer) till 10Mhz (and even above that but who cares?) with a 470 Ohm resistor connected to the beverage box. All 5 boxes with top cover mounted are DC measured as well as tested on the antenna analyzer.
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Five finished & tested beverage connection boxes. You will appreciate the builder's consistency in the construction.
On the right an already newer version is shown. This one has a full weather proof box, better suited for permanent installations.
What's next?
- Copper ground pipes + termination resistor + beverage wire connection terminal
- Ground connection cables to the box
- Time to put that pizza in the oven
1 comment:
The antenna analyzer does show a slight offset in impedance because:
1. batteries were almost empty
2. it is out of calibration
Although I must admit I do not know wat the metal-film resistor does at 1800KHz. I need to get a bunch of various carbon types from RF Parts soon.
'73 Mark
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