Cette page était sur le site de G0FTD; mais le lien ayant disparu, j'ai reproduit ici l'article que j'avais conservé.(F5AD)
Page last updated on: Friday, December 16, 2011
Making a 28MHz rubber duck for the FT817
The main component in this design is the supporting rod, which the wire is wound upon.
I was given two flexible rods by a friend. They are sold as garden rods, used to support flowers and plants. They
also glow in the dark - luminous! They are about 9mm in diameter. Unfortunately, I have not found a local supplier.
The rod needs to be 530mm for the antenna, plus about 15mm, which is inserted into a PL259 for RG8 style coaxial
Solder a suitable length of wire (7/02 guage, 1mm diameter PVC coating) into the centre of the PL259.
Insert flexible rod into the PL259 (it easily fits ok).
Now wind the correct amount of turns on to the 9mm rod, as shown in the diagram.
Then use PVC insulation tape as shown in FIG 3
Add the PL259 <> bnc adapter.
SWR and Tuning
Firstly you must decide how you use your FT817.
Either you hold it with your hand (like FIG ) or it is to be free standing. This is because the human body is part of
the antenna, and must be considered.
Check the SWR using the internal FT817 SWR meter.
Trim the antenna wire by 5mm each time.
WARNING - the 5mm steps are critical, 5mm makes a large difference !
You will also obtain different results when tuning indoors or outdoors - you must decide.
FT817 internal chassis
During the summer of 2006 I made some QSO's with it. Best DX was from G<>EA8, and ES/UA/IK/EA with ease. My QTH was
by the seaside in Whitstable.
I also discovered that the SWR is OK, if I sit down and hold the FT817 between my knee's. It is not a good idea to
use the FT817 at the side of the body when using the carrying strap. There is too much attenuation by the human body.
It is easy to damage the FT817 with ANY antenna which is connected to the BNC socket.
Always be careful with any antenna connected to the front BNC, or damage of the FT817 internal chassis could result.
I have included a photograph of an FT817 internal chassis, which is made of alloy / aluminium.
It is not very strong. Be careful!
Have fun Andy G0FTD