I've grown very fond of internet radio broadcasts while working in my basement shop. I listen on an HP mini plugged into a stereo. I'd like to be able to listen to the broadcasts over any handy fm radio while gardening, working in the garage, etc. I live on four acres in a lightly populated area and the xmitter I've chosen is well below the xmitting power threshold of the average that the hobbiest Christmas display enthusiast crowd utilizes to broadcast to passersby in their automobiles.
What I liked about this little unit was the dead simple plug and play usb connectivity and the dead simple GUI for adjusting frequency and range. And it was less than seven dollars with free ship! All information links are below.
Since there are so many very helpful members here (as I discovered while researching OTA antennas recently) I'm hoping I might get some advice on implementing a little 1/4 wave antenna with this little USB xmitter.
I ordered it and....
Arrived well packaged in bubble wrap three days ahead of estimate. Unit itself surprisingly well built with crimped metal clasps joining the halves of the case. Installed driver and plugged in unit. Selected an empty space on the dial of an fm radio, opened my last.fm scrobbler and typed in Steve Earle, and it worked just beautifully. Truly plug-n-play for the novice.
Slight ambient hum noticeable between songs that was eliminated simply by touching the metal side clasps with fingertips. Range sufficent for one large room.
I removed side clasps and split the case. 3.5 inch antenna wire was doubled over and bare end of it was simply tucked behind the metal side clip. Guess they were using the side clip as part of the antenna element. No solder. Must have been the source of the spotty ground and subsequent hum.
Ran xmitter as bare board with antenna wire extended and range improved to the other end of the house very clearly. No hum. Never owned a xmitter to compare but I"m pretty impressed.
Does not, however, reach the back yard or garage. That is my goal actually to have web broadcast music available while wrenching the motorcycles or gardening in the back, or sitting around the fire with a cheap radio. High fidelity is not a premium for me but the quality so far compared to actual stations on the dial is quite good.
So can anyone help me with a couple of antenna questions specific to this little unit?
Is a 1/4 wave ground plane antenna, built according to this calculator,
http://www.fmuser.com/uploadfile/201004/8/2349199801.png
inherently balanced and therefore SWR (which I have no means to measure) not a concern for me?
Are the tiny SMA connectors and associated tiny coax common to wifi applications compatible with FM frequencies? I'd like to use these connectors and coax to fab the antenna. And where is the best tap on the board for the ground elements? Right off of one of the solder pads of of the USB shield?
I've read that varying "skin effects" between different element choices can affect the length calculation. Copper, alum, steel.... different diameters of wire... insulated or bare....
Is this correct? It is supposedly sufficient to require adjustment of length by as much as an inch on a 30 inch element? I'm planning on using 3/32 steel tig welding filler rod for the elements on the antenna. Any advice here?
Ebay Link
USB2.0 FM Audio transmitter Wireless adapter | eBay
GUI
http://images52.fotki.com/v1551/photos/8/1799248/10530209/FM1-vi.gif
GUI
http://images15.fotki.com/v588/photos/8/1799248/10530209/FM2-vi.gif
Package Contents
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14265.jpg
Antenna was tucked under metal side clasp
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14268.jpg
Bare wire end was simply clasped behind the metal side clip. I noted during operation that
minor hum was eliminated simply by grounding the metal clip with my fingers.
Top of board
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14269.jpg
Bottom of board
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14270.jpg
Bottom closeup left
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14280.jpg
Bottom closeup right
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14279.jpg
Top closeup right
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14277.jpg
Top closeup left
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14275.jpg
Primary IC closeup
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14293.jpg
IC closeup
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14291.jpg
What I liked about this little unit was the dead simple plug and play usb connectivity and the dead simple GUI for adjusting frequency and range. And it was less than seven dollars with free ship! All information links are below.
Since there are so many very helpful members here (as I discovered while researching OTA antennas recently) I'm hoping I might get some advice on implementing a little 1/4 wave antenna with this little USB xmitter.
I ordered it and....
Arrived well packaged in bubble wrap three days ahead of estimate. Unit itself surprisingly well built with crimped metal clasps joining the halves of the case. Installed driver and plugged in unit. Selected an empty space on the dial of an fm radio, opened my last.fm scrobbler and typed in Steve Earle, and it worked just beautifully. Truly plug-n-play for the novice.
Slight ambient hum noticeable between songs that was eliminated simply by touching the metal side clasps with fingertips. Range sufficent for one large room.
I removed side clasps and split the case. 3.5 inch antenna wire was doubled over and bare end of it was simply tucked behind the metal side clip. Guess they were using the side clip as part of the antenna element. No solder. Must have been the source of the spotty ground and subsequent hum.
Ran xmitter as bare board with antenna wire extended and range improved to the other end of the house very clearly. No hum. Never owned a xmitter to compare but I"m pretty impressed.
Does not, however, reach the back yard or garage. That is my goal actually to have web broadcast music available while wrenching the motorcycles or gardening in the back, or sitting around the fire with a cheap radio. High fidelity is not a premium for me but the quality so far compared to actual stations on the dial is quite good.
So can anyone help me with a couple of antenna questions specific to this little unit?
Is a 1/4 wave ground plane antenna, built according to this calculator,
http://www.fmuser.com/uploadfile/201004/8/2349199801.png
inherently balanced and therefore SWR (which I have no means to measure) not a concern for me?
Are the tiny SMA connectors and associated tiny coax common to wifi applications compatible with FM frequencies? I'd like to use these connectors and coax to fab the antenna. And where is the best tap on the board for the ground elements? Right off of one of the solder pads of of the USB shield?
I've read that varying "skin effects" between different element choices can affect the length calculation. Copper, alum, steel.... different diameters of wire... insulated or bare....
Is this correct? It is supposedly sufficient to require adjustment of length by as much as an inch on a 30 inch element? I'm planning on using 3/32 steel tig welding filler rod for the elements on the antenna. Any advice here?
Ebay Link
USB2.0 FM Audio transmitter Wireless adapter | eBay
GUI
http://images52.fotki.com/v1551/photos/8/1799248/10530209/FM1-vi.gif
GUI
http://images15.fotki.com/v588/photos/8/1799248/10530209/FM2-vi.gif
Package Contents
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14265.jpg
Antenna was tucked under metal side clasp
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14268.jpg
Bare wire end was simply clasped behind the metal side clip. I noted during operation that
minor hum was eliminated simply by grounding the metal clip with my fingers.
Top of board
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14269.jpg
Bottom of board
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14270.jpg
Bottom closeup left
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14280.jpg
Bottom closeup right
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14279.jpg
Top closeup right
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14277.jpg
Top closeup left
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14275.jpg
Primary IC closeup
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14293.jpg
IC closeup
http://i802.photobucket.com/albums/yy303/svejkovat/SDC14291.jpg
Last edited: