2m J-Poles and a Slim Jim

Last summer an attempt was made to homebrew a couple of 2m antennas, using parts salvaged from a disused VHF TV Yagi Beam.

The radiating element (folded dipole) provided the stub portion for two J-Poles. Bakelite pieces were used to ensure rigidity and also to locate the BNC connector.

2m J-poles and a Slim Jim

The moulded plastic box was used for the second version of the J-Pole. For the stub portion, the 2 elements were shorted inside the box. A BNC connector was located at the lower end of the box. A length of PVC pipe was fastened to the box to facilitate mounting of the antenna.

Close-up of the J-poles

'M-Seal’(epoxy sealant in dual component lump form) was used at the joints and to waterproof the connections.

The dimensions were arrived at using 'K4ABT's J-Pole Calculator'.

Absolutely no trials / adjustments were required to get the SWR very close to 1:1!

With the remaining material a Slim Jim came into being.

Construction was on similar lines and with good results.

Related post: Homebrew ¼ λ Magmount for 2m

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UHF on a VHF Rig

This circuit enables fair copy of strong 444 MHz signals, off a local repeater, using a 2m rig and an indoor 70cm ¼λ ground plane antenna.

UHF Converter 

The 300 MHz 5th harmonic of the local oscillator, mixing with the incoming signal, delivers output on 144 MHz.

UHF Converter - Schematic

The enclosure is a plastic trinket box reworked to fit two BNC sockets plus one RCA for the DC supply and also to screw the cover in place.

UHF Converter - inside view

The converse (VHF on a UHF Rig) is also possible by just changing over to a 2m antenna and a 70cm rig.

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