{"id":819,"date":"2014-08-13T20:26:55","date_gmt":"2014-08-13T18:26:55","guid":{"rendered":"http:\/\/www.pa3hcm.nl\/?p=819"},"modified":"2021-01-18T17:16:04","modified_gmt":"2021-01-18T16:16:04","slug":"70cm-bicycle-antenna","status":"publish","type":"post","link":"https:\/\/www.pa3hcm.nl\/?p=819","title":{"rendered":"70cm bicycle antenna"},"content":{"rendered":"\n
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My bicycle with 70cm J-pole antenna attached to the carrier.<\/figcaption><\/figure><\/div>\n\n\n\n

During the summer season I sometimes travel to work by bike. It’s a 21 km trip through the countryside, passing cornfields, orchards, deer and spoonbills. The road includes dikes and bridges, and even a ferry to cross one of the branches of the river Rhine. Especially in the early morning it’s a real pleasure to enjoy all the surrounding nature.<\/p>\n\n\n\n

I thought it would be nice to chat with some local radio amateurs on my way back home. I often talk to Adrian PA0RDA while driving home (by car) after work, using the local 70cm repeater PI2ZST, so I decided to prepare my bike for this UHF band.<\/p>\n\n\n\n\n\n\n\n

I already own a Kenwood TH-F7 handy. I bought a small lightweight headset to allow easy operation of this radio: the Kenwood KHS-22. It includes an adjustable boom microphone, a small windscreen and an inline PTT button. The wire is long enough to attach to the radio, which is placed in a small bag attached to the saddle.<\/p>\n\n\n\n

I needed just one more thing: a lightweight 70cm antenna, mountable on a bike. I went into my shed and within an hour I built a small aluminium J-pole antenna on a boom. I attached it to one of the carrier stands, as far as possible to the rear side of my bike. The tip of the antenna is about 160cm above the road.<\/p>\n\n\n\n

Last week it was perfect weather to travel by bike, so I gave it a try. I left work, went on the road and gave a call on the repeater. Adrian replied and first thought I was in my car, still parked at work. Then I told him I was cycling through the village, he was really surprised. There was some wind, but the windscreen did a good job, my modulation was not interfered by the wind at all.<\/p>\n\n\n\n

I went on while talking with Adrian, the distance to the repeater increased. During the whole trip the QSO continued without any problems. Sometimes people along the road looked a bit funny, wondering about that strange guy passing by, with a headset and some strange pole on the back of the bicycle. Even when I was at the ferry (which is very low, just above the water and behind a dike) I was able to continue the QSO, maritime mobile with my bike (outstanders could think I was on a paddle boat hi).<\/p>\n\n\n\n

This project learned me that the J-pole is a very nice antenna for the 70cm band. I really love its simplicity (construction) and characteristics, especially on VHF and UHF. In the past I successfully built J-poles for 2m, 10m, 15m and 17m. Now I have one for 70cm as well.<\/p>\n\n\n\n

Construction details<\/h2>\n\n\n\n
\"[Image]\"<\/a>
Drawing of the 70cm bicycle antenna, showing the construction and sizes.<\/figcaption><\/figure><\/div>\n\n\n\n

Parts list:<\/p>\n\n\n\n