A matching transformer can have some common mode rejection depending on its design. A common mode filter like snap on ferrite beads over the coax is specifically for reducing common mode currents and isolating the antenna from the feedline.Then which is better; a balun, matching network or neither as this is receive only? All of those choices in that MiniCircuits page is beyond confusing.
State a frequency range, 100-200MHz, 50 or 75 ohm and DC isolation and configuration A-B-C doesn't matter. Impedance ratio 1 up to 1.5 that means that if you get a 50 ohm type it will be 75 ohm with a 1.5 ratio that will equal a dipoles impedance or the non folded driven element in a yagi. Connect to the outer windings and do not use center if the transformer has that. Devices that are EZ marked can be had as samples. Select a cheap one like $2 and then state in a document they provide that you are gonna use it for an antenna experiment.Then which is better; a balun, matching network or neither as this is receive only? All of those choices in that MiniCircuits page is beyond confusing.
With these, the cable runs straight thru, no wrapping?For VHF and RG-58 size coax I would use something like this with three in series giving a good 750 ohms choking impedance.
2X44-4281P2
Ferrite Toroids, Iron Powder Toroids, Ferrite Beads, Split Cores, Cable clamp-ons, Balun Cores, W2FMI Baluns and Ununs, Inductive, power supplies, HAM radio.www.amidoncorp.com
Yes, that why you hot glue it to the antenna and also the wiring to it after the soldering. Use a tie-wrap or two around the coax to secure it. It's for a temporary direction finding and not a permanent install on a mast pole, but can be used as such if put inside a weather proof box.
One does nothing, two does a little, three is just right for VHV/UHF.
Seems like you only get reception from the coax alone and not from the antenna elements. There has to be some sort of short circuit as two metal elements connected to a coax should work equal to the antenna on the scanner, and even better when you get the match done properly.
All is apparent well.
The U is for matching and will raise the impedance. A dipole sandwiched between other elements in a Yagi can be in the 25 ohm range and the hairpin match can bring that up to the 50 ohm range but you have to tune its length. The hairpin match will not affect directionality on the antenna but if the match is really bad the coax can interact more and radiate.Whenever I make up most any 'patch cords' especially for RF, I almost always check resistance of the center conductor, then the shield/ground and lastly for a short between the center and shield.
Note I said "almost".
There was a dead short across the BNC fitting.
I did some initial tests using the local US Weather Service (162.55) as a reference signal since it's continuous and found differences with and w/o the 7 turn coil and/or tat 'U' shaped shorting jumper. It seems sensitivity is slightly better w/ the U jumper in place. The 'coil' mod did seem to change things, but not apparently for the better.
I don’t know. I start with some #12 wire longer than needed and trim it for the best match, then make a permanent one out of copper or aluminum. The length is not super critical.
Yes.
