Transmitter help needed
Thread started by
thinkpeace at 07.4.08 - 12:25 am
I'm working on upgrading my transmitter to use on MR rides and am looking for help from anyone knowledgeable about making and tuning antennas.
I'm using a 1 watt PLL exciter, 6 watt transmitter, and a slim-jim J-pole tv-wire antenna. I've checked it with a SWR meter and the SWR reading is in the red (greater than 3:1).
Any radio hobbyist ridazz?
Eric
714-906-8686
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flux capacitor will make it better - if you can pedal 88mph
ideasculptor07.4.08 - 1:36 am
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What frequency does the transmitter use and is the antenna tuned to that frequency? What kind of cable are you using, and what impedance?
PC07.4.08 - 3:00 am
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Also, is there any particular reason why you feel the need to use six watts for this purpose (I assume you want to be able to have multiple trailers broadcasting the same music/commentary)? 500 mW would probably be more than enough, unless you're trying to start a pirate radio station.
PC07.4.08 - 3:03 am
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YA, SEEMS LIKE 'OVERKILL', BUT THEN AGAIN, IF ITS THE SAME ONE FROM THE GYPSY RIDES, THEN THAT SHIT IS NO GOOD, TIME TO GET ANOTHER ONE, SORRY DUDE.
FOR YOU GUYZ THAT 'POWER MORE THAN ONE 'LOAD' ON (2 OR MORE) ON A SINGLE BATERY, ONE DEVICE AFFECTS ANOTHER WHEN SHARING 'JUICE'.
eddieboyinla07.4.08 - 6:22 am
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PC,
We are working on this for the upcoming Midnight Ridazz next Grateful Dead/Tie Dye Shirt ride on the 11th. Last ride with the Transmitter had limited range so we are improving the system. Also, assuming we get say, 500 cyclists, it would be nice to have the trailers spread out at a much greater distance and still have acceptable reception.
Thanks for any and all help with this.
stevo407.4.08 - 8:03 am
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I'm using an antenna like
this one
According to
this website, "Builder beware! The J-Pole, while a magnificient antenna, is perhaps the most difficult antenna to construct! Its resonance point occurs in a very narrow physical tuning range despite the fact that it has a fairly broad electrical bandwidth."
I'm transmitting on 104.7 mHz. The half wave portion is 53.6". The quarter wave portion is 26.8. The feed is about 4" from the bottom.
I'm gonna try making a 1/4 wave whip antenna. It should be more straight forward to tune (and easier to carry).
Thanks for the help.
Eric
thinkpeace07.4.08 - 11:12 am
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RE: the one from the qypsy ride.
Yes, I'm using the transmitter from the gypsy ride. I think the problem I was having at that time was due to high SWR causing the amp to overheat and performance to degrade. Luckily I didn't fry the transmitter and it still seems to work fine.
SWR is the percentage of power reflected by the antenna back into the transmitter. If it's more than 3:1 is can fry your transmitter.
I may actually be OK with 1-watt once I have a good antenna with low SWR (a very difficult task with the antenna mounted on a bike). The SWR is affected by objects around the antenna.
thinkpeace07.4.08 - 11:18 am
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I also need help mounting the transmitter in a box.
Anyone not far from Pasadena have hole punches/drills to mount connectors in a metal box?
The is an SO-239 connector, RCA connector, & 5.5mm barrel jack for power.
thinkpeace07.4.08 - 12:02 pm
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ERIC, GIVE ME A CALL, I CAN HELP WITH THE MOUNTING OF THE TRANSMITTER, IF NEEDED.
eddieboyinla07.5.08 - 3:26 am
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I've had no trouble operating 2m from my bike. I was using a quarter wave whip with a ground plane. I had the whole thing on a mag mount on top of my bike rack.I was pushing out about 2.5 watts and able to hit local repeaters. Using your frequency, you're just outside the 2m band so it shouldn't be any problem getting to other trailers. A J-pole sounds like a lot more than you need. The main thing I needed using the whip was the ground plane. I've even used a pie tin as a ground plane and had it work.
mk452407.5.08 - 6:50 am
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Eddie, I don't have your #. Call me at 714-906-8686.
Mk, what was the typical SWR reading with your 1/4 wave antenna with a pie tin?
thinkpeace07.5.08 - 8:54 am
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I've got it working OK now.
I'm using a 1/4 whip and the SWR is now 2.5:1. From inside my apartment at 2 watts I got a good signal about 1/4 mile away - through several buildings.
thinkpeace07.6.08 - 2:11 pm
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Mike, would it not be possible to use the bike/trailer itself as a ground plane, in the same way that a typical mobile mount 11 meter (or two meter, or whatever) antenna uses the car body?
PC07.6.08 - 2:15 pm
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Mike,
Any chance you are coming on the Grateful Dead Ride this Friday? Any chance your music system is working?
Any chance you'd like to bring it along for the ride?
I'd love as many systems as possible!
Thanks.
stevo407.8.08 - 10:23 am
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We'll be doing a transmitter test ride tonight, 7-10-2008, in Pasadena - 7:30 PM. This is in preparation for the Grateful Dead ride on Friday 7-11.
It will not be a long ride...perhaps an hour - Trader Joes and back perhaps. If you want to test your sound system or just ride along, we'll meet at 861 N Raymond Ave, Pasadena. We'll be done by 10 PM 'cause I need to get to work early.
Eric
714-906-8686
thinkpeace07.10.08 - 11:09 am
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IM EXPERIENCING NO FEELING IN MY LEFT LEG AROUND THE KNEE AREA, WITH PAIN IN THAT SAME HIP AREA, CANT SEEM TO GET OVER IT, SO I DONT THINK I CAN MAKE IT, EVEN THOUGH IT'S JUST A FEW BLOCKS FROM MY PAD, SORRY GUYZ, THIS PAIN IS A RESULT OF MY LAST ACCIDENT, IM TIRED OF 'SELF MEDICTING'!
eddieboyinla07.10.08 - 4:03 pm
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