"Shouldn't the wire be around 31 inches?"
Probably, I didn't calculate the length. I just took a guess.
and I suppose I'll be the one to say it. Pushing the limits of a transmitter such as yours is interesting and you have been successful in extending the original range but be aware that there is a legal limit which is easily exceeded.
Operation of an unlicensed transmitter in the FM band is governed by the FCC rules Part 15.239 which sets a maximum allowable field strength. Since you are most likely not in a position to measure the field strength of your transmitter the next best thing is to go by the range you achieve.
Range depends on many things but it is usually accepted that the legal field strength will provide a range of 200 to 300 feet using a portable receiver. This is a miserable way to estimate compliance but it is the best we have.
Neil
Good point Neil, but isn't sad that the FCC has limited the FM part 15 transmitters as severely as they do, but allows more range on AM. It is kind of interesting that FM is the holy Grail but AM is who cares. Sad situation indeed, I think AM deserves more respect than that.
Maybe someday the FCC will realize the mistakes they have made and make better decsions in the future.
Desktopgrass I am a bit slow with some of my projects, I have a lot of hobbys and some take away from the others.
I have had some MP3s uploaded on the ALPB site, that covers the time, the temperature and the realative humidity weather statements. Zara Radio Free has the ability to play these files at a pre-determined time that you, yourself program into Zara Radio's "events" feature.
What I mean by my having too many hobbies on my agenda is I am supposed to be writting a pictorial in Adobe Reader explaining how to program those files to play automatically and what needs to be updated in Zara Radio for the current temperature and humidity to play out over the air.
I have been having issues with getting good quality photos (screen shots) of Zara Radio's features for the pictorial portion of the instruction manual.
The time files work with the time on the clock set in Zara radio based on your Windows OS clock setting.
The files in question, are already available for download just the same, at the ALPB web site.
Need more information about that, please feel free to ask me.
Bruce.
I have been having issues with getting good quality photos (screen shots) of Zara Radio's features for the pictorial portion of the instruction manual.
Not meaning to derail the thread.. But I just want to mention, Bruce, something just occured to me about capturing screengrabs..
I recall capturing several screenshots of pages from some old magazines in googlebooks - which I often do, however this particular time I was at an old friends house and using his computer.. I had saved the images to a flash drive, and later opened them on my own computer to find them displayed a little fuzzy and soft, which puzzled me becuase I use the same method quiet often and always get satisfactory results..
So I went back to googlebooks and did it again, but this time they looked great!
The problem ended up being that the screen resolution of my friends computer was set very low (like 1024 x 768) so that the images would appear bigger on the screen (he was very elderly and had poor eyesight), wheras my own computer was set higher (1440 x 900).
I am suspecting perhaps you have your screen resolution set low?.. either that or your just saving them at too low a dpi, try 96dpi maybe..
As I exampled before, do you find this screengrab to be unsastifactory?: 
RichPowers in post # 49
RichPowers Your suggestions are well taken thank you!
Your photo looked very clear to me, I am going to download it and add it to Adobe Acrobat 3D and see how it looks. I'll post about the results here, but also will add a link here leading to my original topic related to my pictorial screen shot issues, to keep this here topic on topic.
By the way..very good topic so far, let us NOT, get this one locked...Okay guys?
Bruce.
"Range depends on many things but it is usually accepted that the legal field strength will provide a range of 200 to 300 feet using a portable receiver. This is a miserable way to estimate compliance but it is the best we have."
Neil good point. I'm trying not to be too greedy with range. My hope is if i keep my signal to my complex I wont draw fcc attention.
200 to 300 feet is closer to a city block, and your complex probably is more like a standard lot, perhaps 70 X 100', so I'm guessing that Desktopgrass is within conventional FCC allowed space.
Here is an update on my project.
I received 8 rechargeable aaa batteries from ebay Ni-MH rated at 1500 mAh. The side of the battery says charge 14 hours at 150mAh but my charger is rated 50mAh with a 15 hour charging cycle. Does this mean I will have to charge these batteries through almost 3 cycles on my charger to fully charge these batteries?
I also received, from ebay, a headphone extension cable. Unfortunately, it is 6 feet long. I want to cut it to complete the antenna which is the ground on the audio plug on the Sosche transmitter.
2 questions.... how would you describe the sosche antenna? It is basically everything connected to ground, right? So it is transmitter, audio cable, and mp3 player forming an antenna. What kind of antenna design best describes this arrangement?
If cut the headphone extension cable, how long should it be? Keep in mind i have a 31 inch wire attached to the negative spring battery terminal. This wire will be mounted verticle but the rest of the rig will have to be horizontal.
90.9fm is my best bet for frequency.
Ok, go crazy with your ideas
The batteries will just take longer to charge.
You could get a faster charger(1 hour) or even the 15 minute chargers. If the charger has a "smart" capability it will know when the batteries are charged and shut off
The antenna on your transmitter is basically a small length of wire on the antenna output from circuit board which is the conductor and it can be any of the wires in the small attached audio cable. By adding the 31 inch wire to the negative battery spring which is ground you are adding the other half of the antenna.
The Antenna on the sosche is not "everything connected to ground"....it's the final output conductor only.
The ideal length to have the antenna you are extending to the audio cable is the same as the ground(battery spring) 31".
The arrangement is basically a dipole or a ground plane with only one ground wire instead of 3 or 4.
Mark
My particular model Scosche has the antenna connected to the shield of the audio cable so that the RF signal will radiate from the outer conductor of the audio cable.
I doubt that any transmitter would connect the RF output to the center audio conductor, because it would be surrounded in the audio cable by the shield conductor and not be very effective at radiating to the outer world.
I would use your audio cables at their length as supplied. Very little would be achieved by the small amount that you might shave off.
I cannot comment on the battery connection because I have not analyzed my Scosche to see what the battery connection is connected to as far as the antenna is concerned.
I don't know if I have a Scotche breed of transmitter to test, but one that I got a discount store a few years ago had a short attached audio cable that was wrapped around it and stored in a clip when not in use.
I was curious as to what kind of antenna it used and opened it up, thinking it might be a long trace on the circuit board like wifi routers and garage door openers have.
I didn't see any kind of antenna like that, but it had a coil in a plastic form with I think a brass screw, and going to the board close by was a yellow or green wire that went up in to the audio cord's jacket for a few inches and connected to nothing, that was the antenna! I found out from pulling on it and it slipped out.
Laying up against the other wires, that would send a signal up the extension cable connected to the mp3 player at the end. Even though the wires are all insulated, the signal can make the jump by capacitive effect.
You could solder a wire to a small washer, then slip that in the negative battery spring terminal, and with the battery in it would hold the spring down on the washer and make contact. That would make a dipole like antenna with the transmitter located at the center. Look up dipole antennas to see how most are fed at the center.
With a simple multi-meter, what can I tell about the condition of my batteries other than voltage?
A multimeter can tell nothing other than voltage....to tell more you need a battery tester that tests under a typical load, or, check the voltage with a multimeter while in your device with it on and you will get the voltage under working condition. That's the true test of battery condition.
Mark
".....check the voltage with a multimeter while in your device with it on and you will get the voltage under working condition."
Battery is new been on a cheap charger for several hours. I put the battery in an mp3 player, I didn't play an mp3 cause this player requires a micro-sd card and I dont have an extra. with the player on the multimeter said ~ 1.3 volts. but the battery indicator in both mp3 players I try only show 2 out of 3 for the battery.
I tried the new recharables last night and I noticed a big drop in my signal. Any Ideas?
The normal operating voltage with rechargable batteries is around 1.2 volts and a new regular alkaline battery is 1.5 to 1.6 volts. Try fresh alkaline batteries and the icon on the MP3 player should show full. When the voltage falls to 1.2 volts with an alkaline that's going to show on the indicator as only half battery life remaining.
The indicator on your MP3 is based on alkaline batteries.
So if you use rechargables the MP3 display will never show 3 bars or full so ignore it.....in your case 2 out of 3 ain't bad.
Mark