Fm antenna matching and SWR.
Disclaimer. I live in the country five miles from any neighbor. I'm frankly not worried about potential FCC violations for 1/10 watt FM broadcasting. That said, the following application (i have no access to measuring devices) almost certainly falls far short of even that signal strength.
I went shopping for the cheapest, easiest to use, fm xmitter available so that I could listen, anywhere in the house, yard, basement, or garage, to internet radio broadcasts of which I've recently come to enjoy IMMENSELY. I really liked the idea of dialing into any broadcast I please via any little transistor radio handy while I'm working.
I ordered the following for six dollars with free shipping.
It arrived today. I installed the driver, plugged it in, found a vacant spot on the FM dial and was EXTREMELY impressed with the quality. Good for use in the same room. Unbelievable that this six dollar item has a very useful desktop GUI that provides settings and slidebars for a variety of control over frequency, xmission strength, and other.
So, removing the tiny board from its case I find a roughly three inch antenna lead bunched up along the side. I unfurled this and the broadcast was even better. About 50 ft clear reception.
What I'd like to do is the use the following utility....
...to mate this up with a better gain quarter wave ground plane antenna of the type drawn in the gui of that utility.
There are many diy pages on the net that provide the details of construction. My antenna "mast" and ground plane segments will be 3/32 steel welding rod.
I'll connect the usb xmitter directly to the antenna via about two inches of the tiny coax attached to a common SMA connector pigtail (since it's extremely thin and flexible) and then mount the xmitter rigidly to the underside of the "spider"....
...solder the coax to the tiny USB xmitter board at the antenna points and connect the female end of that pigtail to one of these
... as the body of the antenna "spider" keeping it as lightweight and simple as possible
As a novice, all I seem unable to glean from diy antenna sites and tutorials is SWR matching. Do I need to be concerned with it here?
And lastly, I've seen mention of adjusting the length of the elements after you've calculated them to compensate for different wire materials. Steel, alum, or copper,clad or unclad, exhibit different "skin" effects in these frequencies. Compensation for that can be on the order of an inch or more. Is this correct? What would I calculate for 3/32 steel elements?
If this is beyond the scope of this forum, can anyone please suggest another more appropriate?
Thanks so much.