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Author Topic: bicycle mobile help!  (Read 2026 times)
M3MFZ
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Posts: 12




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« Reply #15 on: March 05, 2010, 12:58:41 PM »

WB6BYU, not as easy as i thought you would have said, but i might well give it a try one time.
Cheers
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KL7AJ
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Posts: 329


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« Reply #16 on: March 09, 2010, 09:55:58 AM »

Book racks make great platforms for bicycle mobile antennas.  If you can move the antenna a few feet back from your body, you won't detune it as much.

There should be no problem getting the SWR down to the vanishing point mounted in such a way.  Where is your antenna resonant?

eric
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M3MFZ
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Posts: 12




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« Reply #17 on: March 09, 2010, 10:28:46 AM »

Antenna for 2m. Somewhere on 2m, is all i know, sorry.

Im going to try and mount it on the rear rack on the bike. Just got to get some bolts that are the right size, then we should be away. Hopefully.

Book rack? Are you meaning the racks for the back of bikes, or some other type or rack made for books?

Cheers

Joe
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KL7AJ
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« Reply #18 on: March 09, 2010, 03:22:52 PM »

Yeah, same thing, if they're the type with the spring-loaded clamp.

Can you tell if the SWR is any higher on one end of 2 meters than the other?

eric
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M3MFZ
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« Reply #19 on: March 09, 2010, 03:25:02 PM »

No, no spring loaded clip.
Ill try the SWR again tomorrow and report back if its lower on one side then the other. I been SWRing in the middle at 145.500

Cheers

Joe
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KQ6Q
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Posts: 968




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« Reply #20 on: March 17, 2010, 08:48:56 PM »

The coax run from the HT to an antenna is going to be less than 6 feet. Don't bother measuring SWR, just see if you can hit the repeater. BUT can you hit the repeater with the HT and the standard antenna? If not, you're not likely to do it with a bike lashup.
What can work - get a bike safety flag - on a fiberglass pole, and make or buy a rollup J-Pole. They radiate well and don't need a ground plane. Tape or cable-tie the rollup j-pole to the bike flag pole. Connect to the HT and go.


Fred, KQ6Q
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WX7G
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Posts: 5948




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« Reply #21 on: March 18, 2010, 02:13:21 PM »

KQ6Q got me to thinking. An HT with a rubber duck is about 10 dB below what the bicycle antenna should do.

You might find a repeater that you hit a bit under full quieting on the handheld and rubber duck at high power. Now connect the HT to the bicycle antenna and switch to low power. If it still hits the repeater with about the same signal strength things are working well.
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KC7JXF
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« Reply #22 on: April 11, 2010, 05:56:39 PM »

I am a professional bicycle mechanic, and set up a bike/mobile rig to provide support/participation communications during the local century ride last year.

My road bike has a 60cm lugged steel frame, with carbon front forks. I mounted a plate of 1/4" aluminum, about 4" wide, above the rear tire. The plate is supported by fender stays at the rear, and curves up and tapers towards the seat tube. The plate mounts to an aluminum clamp on the seat tube.

I drilled and tapped a hole for a 2" UHF coupler (The coupler has the same threading as the oversized pedal taps we use at the bike shop to repair stripped cranks). You may wish to use a NMO connector instead.

I mounted my radio on the handlebars, with a remote PTT switch under the shifter/brake hood. I ran a piece of mini-8 coax to the UHF coupler, and a mini TRS jack up to the seat, to connect a headset.

I used a car antenna on the aluminum plate, a Comet fold-over (it doesn't fold anymore, broke too many times) designed for a mag-mount. Worked like a charm, full quieting into the local 2M repeaters.

Let me know if this helps, I can probably get together a picture of my setup if it would help. Let me know.

KC7JXF
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N8EKT
Member

Posts: 371




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« Reply #23 on: April 11, 2010, 06:40:15 PM »

You need a 1/2 wave antenna.

The 32 inch long Larsen 270bk works well with very little under it.

And so will any 1/2 wave design
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