View Single Post
  #16  
Old 01-20-2012, 11:47 AM
DaveInDenver's Avatar
DaveInDenver DaveInDenver is offline
Hard Core 4+
 
Join Date: Jun 2006
Location: Larimer County
Posts: 6,561
Default

Quote:
Originally Posted by nakman View Post
And yes, you could technically blast any frequency through any antenna with some reduced capacity
NO!

The relationship of 145MHz to 445MHz is such that they do not share a 1/4λ multiple fundamental. If you key on 70cm into a 2m antenna it's probably going to see a high reflection.

There are ways to make this work, a gamma match or making the antenna into a sleeved dipole, etc. But typically mobile monopole whips use a trap to make a long antenna electrically correct for 70cm, say a 1/4λ 2m into a 3/4λ 70cm or 1/2λ 2m into a co-linear 70cm.

All solid state radios made now necessarily (tube radios tolerate high SWR much, much better) shut down on high SWR, which is why you could probably key up and not ruin your radio. It might even leak a little RF onto the antenna, but it won't be much (like milliwatts).

If you do it long enough with high enough power, you'll fry the protection shunt. It's all about heat, any power not doing work exciting electrons (which requires antenna resonance or apparent resonance with caps and inductors helping) is converted to heat, which is the sworn enemy of transistors.
__________________
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29

"They say the test of literary power is whether a man can write an inscription. I say, 'Can he name a kitten?'" -- Samuel Butler
Reply With Quote