Feb 16, 2009

Beverage antenna

Preparations for the beverage antenna(s)
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.

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

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.

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:

Mark, PA5MW said...

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