There is a book that goes above and beyond antennas called the arrl handbook for antennas
Thank you for the suggested reading.. Everyone has to start somewhere... Marketing claims are always optimistic (if not outright lies) -- which is why I have a bit of skepticism.
ultimately, I'd like to achieve a 'best case' for the conditions I'm working with; which for me, is trial and error.. as long as the book doesn't go too far over my head,maybe it will reduce my error count...
There's alot of info in the radiorefernce forum.
Indeed... but filtering it out, or finding what's applicable is the hard part-- I'm specifically looking at receive-only performance...I mean,the comtelco antenna I have looks like a coat hanger... then I look at a different antenna and it has a coil; both claim the same frequency coverage...
Thank you for the links.. 1st read was good reading, with most of it over my head.. hopefully the 2nd read after a cup o coffee will help...
Also, if you are comparing the antennas by looking at the gain claims, you really need to take that with a grain of salt.
Marketing claims are.... well; yea. I do.
Gain, measured in dB, or Decibels has to be in relation to something. What the base is is where it can get confusing.
Indeed... There are things I know, there are things I think I know, there are things I do not know. Antennas are somewhere between the last latter two. Which is dangerous; but at least I know to ask questions and learn something...
dBi, or Decibels - isotropic is the antenna gain given in relation to an isotropic radiator, a perfect antenna.
dBd, or Decibels - half wave dipole.
Any time you see an antenna gain given as just dB, you've got to realize that they are not giving you the reference, so it's kind of a pointless thing.
Some companies will use dBi, since it will make the antenna look better than it really is. Most antenna manufacturers will us dBd. The difference between dBi and dBd is about 2.1dB, so using dBi will make a particular antenna look 2.1dB better than the same antenna that is measured as dBd.
I hadnt noticed that; but it's a good point to remember -- compare apples to apples...
I had to double check to make sure I posted in the correct area...
I'm talking strictly scanner/receiver stuff -- no transmit...
A 50 watt transmitter with theoretical lossless coaxial cable connected to a quarter wave antenna would have an "effective radiated power" or ERP of 50 watts.
Swap that quarter wave out with a 5/8 wave antenna and your ERP would jump to 100 watts.
This I knew, albeit not from a science point of view... People with 1/4 wave cb antennas could not get out as far as people with 5/8 - but usually (not always) this equaled "bigger is better" -- but after doing a base station with limited roof space, I learned "not always"....
Thanks for the info -- food for thought; after coffee -- I am looking to get a best-case scenerio recieving signals in a less than optimal antenna mounting location...
I'm trying the
scannermaster antenna -- but it just seems (gut feeling) to me that I can do better by using a taller/larger (ie: 4') antenna mounted in a less than optimal position (rear of truck cab) than I can using a smaller antenna mounted in a more optimal, but still not optimal, position.
Given various mounting positions: (The roof is not available.)
I can go bumper, hood, mirror, or back of cab,
near the roof line.
Current plan, from reading & suggestions, is to use the hood with the scannermaster antenna ... but it just seems to me, I'm doing more "listening forward" than "all around" since signals from the rear is blocked by the cab.
Mirrors (to me) is the least ideal, with the rear bumper right in there with the mirror.
Going off the rear of the cab, close to the roof line, with a taller antenna, just seems to make the most sense -- however, talking to folks, I get a "use a proper antenna with a ground plane" which brings me back to the engine hood as the best spot with a smaller antenna...
From the links/info here; seems to be; that's the best spot (available) ... I just wish I understood
why.
Thanks
-j