HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: Captainenema on October 29, 2013, 0610 UTC
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A friend who lives in a very bicycle friendly city on the West Coast raised the idea of mounting a transmitter in a saddle bag and then go for a nice long bicycle ride.
The question that remains, what sort of antenna would be best? We've bandied around the idea of a 1 watt transmitter as well if that bit of information helps.
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A friend who lives in a very bicycle friendly city on the West Coast raised the idea of mounting a transmitter in a saddle bag and then go for a nice long bicycle ride.
The question that remains, what sort of antenna would be best? We've bandied around the idea of a 1 watt transmitter as well if that bit of information helps.
If you can put a transmitter on a boat, then i dont see too many problems with a bike being used. Try it, CE, and I'll try to hear you
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It shall be tried, one of these days, just need to figure out what sort of antenna to use.
And build a radio.
and test it.
and sort out the bike.
And record 40 minutes of porn noise to play at full power the next University of Oregon home game is broadcasted. Ok, kidding about that, but serious, U of O ducks are terrible. :(
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The question that remains, what sort of antenna would be best? We've bandied around the idea of a 1 watt transmitter as well if that bit of information helps.
What frequency? 6900 range, or FM b'cast, or other? It's a great idea CE, but operating frequency will be the primary driver concerning antenna choice. Please keep us posted on your progress...
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Yeah, living near the Appalachian Trail, I've often wondered about the possibility, range, etc. of some through hiker broadcasting with a low-power transmitter in the backpack & a tall whip antenna. If they operated live, it'd make for some interesting broadcasts.
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RF in the bike's frame would be the main problem, IMO. The frame will behave like RF ground. Anything on the bike is going to be part of it, including you.
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Jeesh how could you do 40 meters on a bike? A commercial coil and extree long whip which I may have used is like 9 feet tall on top of the car. I might have had trouble with overpasses and trees and stuff. I may have taken things for a drag down the highway a few times and not been heard at all running 10 watts. I might have given up after halfa dozen times. CB range/10/11 meters I think would be the only realistic thing without being a freak magnet for the popo. You will attract enough attention with an antenna of any sort on a bike. And even if you did have a 10 foot monstrosity coming out of the bike, the ground plane would be nonexistent. You could get at least a few miles I bet but don't know about NVIS regional stuff. I would bet against getting out regionally like that.
Maybe consider a 10 meter up to 25 watt radio that runs on 12VDC? Cheap Radio Shack 20 year old ssb radio on the cheap(HTX 10 or 100 is it?), 12 v gel cell, coiled CB antenna cut to resonance?
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40 meters on a motorcycle
been there done that ;)
nice rf exposure fix :o
if you gonna try fm band try a vertical dipole
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The other option is to get a baby carrier trailer like this: http://www.ebay.com/itm/Double-Swivel-Red-3in1-Bicycle-Bike-Trailer-Baby-Stroller-Jogger-Carrier-30RB-/231035135912?pt=LH_DefaultDomain_0&hash=item35cac467a8 (http://www.ebay.com/itm/Double-Swivel-Red-3in1-Bicycle-Bike-Trailer-Baby-Stroller-Jogger-Carrier-30RB-/231035135912?pt=LH_DefaultDomain_0&hash=item35cac467a8)
Keep everything buttoned up inside until a suitable vantage point is attained, rig antenna, hit the transmit button, quietly mosey away to a discrete distance and watch. Reverse the process when finished and quietly ride away.
Upside, I hate driving, could use the brat carrier for hauling groceries when not in use for other purposes. Will look up vertical dipole in a bit.
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It's a lot of trouble to go through if you are simply trying to minimize the risk of being caught. A more practical compromise is to pedal off to a park, toss a wire over a tree branch, and enjoy a picnic while your show plays. Then pack it back up and pedal home.
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Also, mountain bikes are also good for getting further out into remote locations.
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It's a lot of trouble to go through if you are simply trying to minimize the risk of being caught. A more practical compromise is to pedal off to a park, toss a wire over a tree branch, and enjoy a picnic while your show plays. Then pack it back up and pedal home.
Any suggestions for a transmitter?
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Any suggestions for a transmitter?
Again, Cap'n - what band(s) are you interested in operating on?
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fm
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fm
OK. That narrows things down. I agree with Beerus, the best way is to operate from a fixed location. Even on FM, where you could easily rig up a bicycle antenna, your signal will be constantly "picket fencing" and any listeners will probably tire of that quickly. You could easily rig up a quarter wave antenna from an SO-239 connector with a length of stiff wire like #12 solid (234/freq in MHz gives you length in feet) soldered to the center contact. Then take four hunks of the same wire about 18 inches long and attach to each of four corner holes on the SO 239 and bend down to a 45 degree angle. These are easy and work pretty well. If you are a bit more ambitious you could build a J-Pole.
For FM transmitters, I'm sure you'll get many different opinions on the HFU. My only advice is to buy and build a kit. You will NOT save money by trying to roll your own VHF device. That's a recipe for disaster - unless you are an RF engineer... or a masochist ;) Have fun.
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Check eBay for FM band transmitters. If you can manage to filter out all of the VERY low power FM transmitters typically used for transmitting MP3 players, you'll find some probably-not-legal-but-hey-it's-eBay offerings around 1-10 watt. An example is this one which can transmit up to 6 watts:
http://www.ebay.com/itm/CZH-5C-1W-6W-76-108Mhz-FM-Stereo-Transmitter-Power-Supply-Antenna-/300802160628?pt=US_Ham_Radio_Transmitters&hash=item460934b7f4
I don't know anything about these, but transmitters like this are abundant on eBay. 6 watts, with a decent antenna, would certainly provide coverage of a few neighborhoods, depending on terrain and such.
It appears the 1 watt Veronica design is still on the market:
http://www.aareff.com/en/1w-pll-fm-transmitter-kit.htm
I HAVE used this transmitter (about 15 years ago, statute of limitations is way passed baby!) and it worked very well, if you can assemble and tune it up correctly. I ultimately had this transmitter working with a matching stereo generator board and an amplifier (maybe 30 watts total if I recall?) and it covered a large east coast city very well.
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I operate from a fixed area. I couldn't imagine broadcasting mobile. But thats mainly because i have a huge studio set- up going. My station sounds quite professional I must say. And so do the others who tune in.
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I operate from a fixed area. I couldn't imagine broadcasting mobile.
I hear ya atrain, but portable operation using pre-recorded programming works quite well and is a great way to keep out of the Fed's grasp. Back in the 80s when I used to play with FM (statute of limitations, nah nah nah! ;D), one of our favorite ploys was to drive up to the rooftop of a downtown parking garage, plant a 1 watter with a whip and a portable cassette deck with auto reverse by one of the lamp posts. Everything ran from a couple of 6 volt lantern batteries wired in series. We would leave it running the same 90 minutes of programming until the batteries ran down, which would be about 18-20 hours. Then we'd retrieve the package a couple days later. The one thing about the FM band is: few people tune around on it. If you aren't on for long long stretches, or run a regular sked, no one will hear you. This way we could saturate the downtown area of the city and be on long enough to be noticed.
Nowadays, there's a LOT more cameras around to avoid and everyone is FAR more aware of things like unattended bags laying around than they were in the 80s. BUT - Tiny MP3 players and tiny FM transmitters - both of which are able to run on much lower power requirements (much smaller battery pack) make this form of operation still possible, given a little creativity. The whole point of this type of operating atrain, is to reach a lot of casual listeners - not just the dozen or so Buddies that listen for your signal.
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Great advice here, will consider it carefully. I realize now my biggest problem isn't lack of knowledge, its is being able to understand the information being imparted here.
So what I'll do is get my HAM licenses and spend some time learning more about radio and electronics before getting a little crazy with it all.
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You don't have to get a license, just read the ARRL Antenna guides, some stuff on audio processing, and go have fun. FM antennas are dead easy to make.
BTW, the oddest thing happened the day after this thread turned up. One of the local heathens stashed a mountain bike in the bushes next to my house. It's a sign from the Radio Gods.
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BTW, the oddest thing happened the day after this thread turned up. One of the local heathens stashed a mountain bike in the bushes next to my house. It's a sign from the Radio Gods.
can you still ride a bike :D
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BTW, the oddest thing happened the day after this thread turned up. One of the local heathens stashed a mountain bike in the bushes next to my house. It's a sign from the Radio Gods.
The Radio Gods desire a VOTAB resurrection... ;)
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Outhouse, I was wondering the same thing. LOL.