Topband: insulated vs:bare radial wires

[Tod -ID]

Thanks for the note Bill.

As you say, Physics doesn't cut any special deals with anyone. 

That of course is the good news delivered simultaneously with the bad news. 

The way to deal with radials is to have none -- just put your 1/4 wave
vertical out on a rock in the ocean and go from there.

I think you characterize it correctly when you point out that the efficiency
with no radials or just a few radials is low. 

I did a little thought experiment to get to the 'screening' idea.

I started out imagining that there were an infinite number of radials spaced
an infinitely short distance apart and "sufficiently" long. That would allow
the field return to have very low losses. Then, as one removes radials and
positions the remaining ones an equal distance apart there will be more and
more of the field travelling through the lossy medium [earth] with
correspondingly greater losses. It doesn't take a lot of imagination to
conclude that 'more is better' and more close to the feed point is better
since the current is higher there for the 1/4 wave and shorter verticals.

I am not sure how to reconcile that concept with the elevated radials setup
or with the ground plane antenna systems used on high frequencies. I guess I
have never looked closely at the elevated radial system losses -- not much
chance of me ever being able to install such an antenna I am afraid. 

My experience has been the same as Gene's and Lee's --- insulated wire works
best for me on a long term basis. I happen by good fortune to have captured
at no cost about 2 miles of insulated #15 stranded copper wire. It was
originally sent down holes in the oil filed [who knows why}. A bit stiff
when handling, but once inserted just below the grass it seems to not
deteriorate. I add a few radials each year in the hope that it will make it
easier for me to be heard when transmitting.

On the other hand I make changes every year in the RX antennas hoping to
hear people who have heard me calling and want to call back. A vicious
circle I am afraid. 


Tod, K0TO

M

> -----Original Message-----
> From: Wolfert, William R. [mailto:WWolfert at columbuspolice.org] 
> Sent: Saturday, December 05, 2009 9:13 AM
> To: Tod -ID
> Subject: RE: Topband: insulated vs:bare radial wires
> 
> Todd
> 
> You don't have the wrong idea about radials. You are dead-on 
> as to what they do. They are (obviously) called a screen 
> because that is what they
> do- just as you stated. Your view is not flawed! Even casual 
> users of vertical antennas have proven that more is better- 
> they just don't realize it. A guy buys a multi-band vertical 
> and just puts down a few radials. He checks the SWR and 
> Voila, nice and low; so he thinks all is well. As you know, 
> it's not. He's probably only radiating 10% of his transmitted 
> power. Upon advice from a knowledgeable ham, he adds a bunch 
> more radials and his match gets worse but now he's radiating 
> 60% of his transmitted power. 
> 
> I'm sure you're aware of the Brown, Lewis and Epstein report 
> to the IEEE in 1937. It's still the standard. More recently, 
> N6LF and W8JI&W7EL did similar experimental measurements of 
> the effect of radials. Their independent results agree with 
> each other and all of them agree with the BLE report of 70 
> years ago. I don't know if you've ever read through the 
> Topband archives, but N7CL gives an excellent explanation of 
> what's happening with radials and our vertical antennas. 
> 
> Sorry to make you bleed from the eyes, but all this to say 
> your understanding is correct. I'm not an expert, but have 
> read an awful lot about verticals and radials over the years. 
> My own personal experiences merely confirm the experimental 
> results of the above mentioned individuals.
> Physics, just like the Ionosphere, is no respecter of 
> persons. It is what it is for all of us! With some things, 
> there just are no shortcuts!
> 
> 
> 73, Bill WR8K 
>