Antenna Projects

A few antennas and related projects I have built.

HF

Current Balun/Choke

1:1 current balun/choke built with FT140-43 and RG-174. Built this to cure RF-In-The-Shack problems I got with a commercial OCFD antenna. Apparently the 1:4 balun on the one was a voltage balun and didn't keep the RF from the coax shield.

Current Balun/Choke

Also built one with a balanced output.

1:4 Dual Core Current Balun Winding

Two current 1:1 current baluns can be connected in to one 1:4 current balun by connecting the inputs in parallel and shorting the hot side of one to the ground side of the other and using the remaning two leads as the output. Here done with two FT114-43 toroids.

Enclosure

Enclosure is ready for the balun to be mounted.

1:4 Dual Core Current Balun Winding

Done!

VHF/UHF

Wire hanger Quarter Wave Ground Plane

As seen in ARRL Antenna Book etc. Using a N connector instead of the traditional SO-239 connector. Very easy build, did most of it sitting on the sofa watching TV. Elements are cut from wire-hangers which are 2mm in diameter.

Connector

The crimped ring terminals make it easy to remove the groud radials for transport. They bend to so can be used to adjust the antennas impedans, although I wouldn't try that more than a couple of times. At 90 degree angle the antennas impedans should be around 30 Ohm and raise to about 50 Ohm if the radials are at 45 degree angle.

70cm Ground Plane Done

Got very good reception of APRS packets at 431.04 MHz inside the apartment. Will probably need scavenge more wire hangers to build a 2m version.

2 Element Wire Hanger Yagi

After building the quarter wave it seemed doable to build a small light Yagi for the 70cm band from wire-hangers too. Although it models pretty good I wouldn't use it for transmitting before tuning it carefully cause millimeters matter.

The elements were cut and for boom I used a length of MDF board I had left over. Not the best material probably but worked well for a prototype. Two grooves where cut and the reflector glued into the back one. The driven element soldered to a BNC connector and glued into the front groove.

Driven element in groove

A light Yagi like this could come in handy for receiving a 70cm satellite downlink like that of SO-50.

Pointed to the sky

SWL

A few shortwave antennas I tried with very little success. After a while I discovered where I live have severe interference pretty much across the whole HF spectrum and very little I can do about it. Shortwave on a hold until move somewhere else.

SWL Random Wire

Rx Random Wire No Un-Un

Hanging on our apartment balcony in Shibuya, Tokyo.

9:1 Un-Un

A 9:1 Un-Un built with a FT114-43.

SWL Magnetic Loop

Rx Magnetic Loop Coupling Loop Feedline Connection


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