Desktopgrass said: "I understand from reading about the Scosche fmt4 that a short piece of wire on the negative battery spring will extend this antenna.That piece of wire i can mount verticle, i guess this emulates the mid fed L that Carl had success with. Am I correct?"
Yes! That would be an excellent way of achieving a Mid-Fed L antenna.
By the way, an audio cable extension cord would be another way of making the antenna longer, but you wouldn't want too much length... no more than a quarter wavelength of total antenna length.
Oh, and Druid Hills... that is a very clever DIY Groundplane Antenna.
I recommend against doing any circuit changes in the transmitter at this early stage... if your surgery failed you might be off the air until you replace the transmitter.
My internal changes, to remind you, were made on the other version of the Scosche, the FMT4R, which has a different build.
Although the article I linked does show how to modify the antenna in your version, it is a risky operation.
Carl i agree, less is more when it comes to modifying the innards. I will stick with short wires on the negative battery post and a short extension of the audio input to the transmitter.
What kind of whire should i use? Insulated? Bare? Single strand? Twisted strands? Guage? Material? Does it matter?
I use a Sandisk sansa clip for my audio source because it takes micro SD cards for a huge capacity but the point is I originally opened it up and removed the li-ion battery and very carefully soldered 2 wires to the circuit board at the power points and brought them outside the case, closed it up, got a 3 C battery holder(approx voltage of li-ion battery) and using double sided tape attached the MP3 player to the battery holder and I have 3 weeks 24-7 runtime with 15 seconds down time when changing batteries.
Having 5 hours down time every 8 hours is no good with a radio station!
By the way the Broadcastvision would be my choice for the transmitter, and will have no trouble covering the area you want.
Mark
Desktopgrass asked: "What kind of whire should i use? Insulated? Bare? Single strand? Twisted strands? Guage? Material? Does it matter?"
It matters in terms of integrating with the size of the transmitter and the installation location...
Since you'll be attaching the wire to the battery terminal, which is light-weight metal, use a smaller guage wire so the solder point will be easy to manage, probably stranded for good solder flow, and insulated so it poses no risk of shorting to any nearby metal in the surrounding area.
Thanks Mark, I have a cheap mp3 player with no internal storage just micro sd it runs on 1 or 2 aaa batteries.
Could I power both transmitter and mp3 player with a similar power pack?
The RCA mp3 player I will use is 4 gig, it ran almost 24 hours on a dollar store alkaline aaa.
Thanks Carl. I opened up a networking cable, now I have all sorts of small guage, stranded wire. I may not solder the antenna to the battery connection, is that a horrible idea?
The battery connection is a smooth silver metal that might not adhere well with solder, so you might be better to connect the wire to the same location where the audio shield is attached, knowing that the antenna RF output is tied to the shield.
Carl, I am going to put the antenna wire in the spring that holds the battery. The compression of the spring should hold it securely and maintain a good connection and I can easily disconnect the antenna and leave the antenna mounted to the structure if I need to remove my broadcasting rig. Am I off base with this line of thinking?
No, you are not off base, at least not in my opinion...
You will find what works, and if something doesn't work, you will try another approach.
Part of the fun of it is figuring out how to get it all organized.
Keep going.
Yes you can power both the MP3 player and the transmitter if the voltage is the same for both.(you're referring to the Scosche?).
But the Broadcastvision runs on between 9 and 12 volts so you'd need a separate supply for both if you use that one.
On the Scosche since the attached input audio cable is the antenna if you just get an adaptor(male to male coupler) and attach a 6ft audio cable you will have a better antenna. You don't need to do anything with the battery spring.
Mark
Meant to say female to female coupler.
Mark
I believe i need female to male xmitter is male mp3 player is female
Seems the Scosche people had the microbroadcaster in mind. The battery cover has a slit cut in it that easily accomodates a strand of wire I took from an ethernet cable. I eyeballed about 3 feet which seemed about right for 90.9 fm and put it in the spring for the negative battery. The signal was very strong all around the pool and dogpark. I used a cell phone with an fm chip and could pick up a very listenable signal at about 300 feet. The stock regular fm radio in my izusu rodeo gave me listening pleasure almost 1000 ft with my best line of site I could get to in the parking lot. I also covered almost all of a small college parking lot, not so far away but behind a wooded fence row and a bonus for my soon to start broadcasting station.
Questions... I used one single wire from a networking cable as an antenna. I untwisted the two wires that coil around each other. Is this a good antenna? What happens if you leave the other wire that wraps around the wire I used as an antenna? Bad idea?
I also seem to remember some one suggested that the audio cable from the transmitter and the attached mp3 player form a folded dipole effectivly making that audio chain about 14 inches of antenna. Does this jive?
After successful transmitter tests I am ready to move to programming issues. Should I continue here with the programming questions and ideas or should that go into a different category?
Your signal coverage results sound like you are achieving what you set out to achieve and that is good news.
Because the performance is so good, don't worry about the extra (unused) length of wire left wrapped around the antenna... who knows, it might even be adding to the signal strength through inducted energy!
As you add audio cables we hope the performance holds steady and doesn't de-tune, but that can be corrected later if there's a problem.
I'd say you can swing into programming topics right here in this thread since it relates to the same project, but others might express other preferences.
Shouldn't the wire be around 31 inches?