I haven't been in much of this discussion, but is your trailer metal or 
fiber glass.  If made of a conductive material, you need the radiating 
part of the antenna a above the metal.  If this is the case, the mast 
should be conductive and part of the ground system as the entire body of 
your trailer should be.  My friend just has his mounted on a trailer 
hitch which mounts to the frame, not two foot above ground.  Remember, 
your mobile antenna is just a vertical.  You can move it higher, but if 
it is way above ground, say on a non conductive mast, you're changing the 
impedence of the thing.  I see no reason at all for it to be 
non conductive.  If you want, give me a call some time on phone or radio 
and we can discuss things.  I once had a discussion with the a e s 
people in Vegas who really had no clue on antenna theory or radiation. 
We were mounting an antenna on a club trailer and I said I wanted the 
longer piece under the coil.  Their comment was, "just mount the antenna 
higher"  I tried to explain them it wasn't the height, but that you 
want more of the current radiating part under the load.  That is which a 
top load is best, although not practical.  Center load is next best and 
a base load will work, but not quite as well.  Although much is made of 
s w r, standing waves on the antenna is what makes it radiate.  AT the 
feed point of 50 ohms, current is high and voltage low.  As you move out 
toward the end, voltage goes up and current drops.

73
Butch
WA0VJR
Node 3148
Wallace, ks.


On Tue, 16 Aug 2011, 
Tom Behler wrote:

>    So, Butch, what is your thought on whether the mast should be conductive
> or non-conductive?
>
> Can you tell me more about exactly what your friend uses to support his
> mobile antenna?
>
> Thanks, and 73 from Tom Behler:  KB8TYJ
>
> ----- Original Message -----
> From: "Butch Bussen" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, August 15, 2011 10:10 PM
> Subject: Re: Need suggestions for better mast arrangement to safely raise HF
> screw-driver antenna on RV
>
>
>> If you get it above the roof of your trailer, the heighth isn't going
>> to make that much difference.  You need a good bround.  I have a friend
>> who has one mounted on the gack of an ex tera on a trailor hitch and he
>> just took third place in an antenna contest at a ham fest last week end
>> and he always puts out one of the best mobile signals I've heard.  I'm
>> considering getting a scorpion to put on top of this metal house I live
>> in as a second and spare antenna. ]
>> 73
>> Butch
>> WA0VJR
>> Node 3148
>> Wallace, ks.
>>
>>
>> On Mon, 15 Aug 2011, Pat Byrne wrote:
>>
>>> How about PVC?
>>> Pat, K9JAUAt 09:00 AM 8/15/2011, you wrote:
>>>> Hi, all.
>>>>
>>>> Well, I attempted to check into yesterday's 20-meter Cross-Country blind
>>>> ops
>>>> net from the RV, but was not successful.
>>>>
>>>> I believe my screw-driver antenna simply is not high enough on the back
>>>> of
>>>> the RV to allow me to get out well.
>>>>
>>>> The antenna is mounted with u-bolts on the back bumpber on a piece of
>>>> pipe
>>>> that is probably about thre or four feet high.  This gets part of the
>>>> screwdriver antenna and whip above the roof line of the RV, but it does
>>>> not
>>>> get it completely above the roof line by any means.  The RV is
>>>> approximately
>>>> 12 feet high.
>>>>
>>>> Originally, I had used an arrangement with a longer piece of mounting
>>>> pipe,
>>>> but it turns out that the pipe was de-tuning the antenna, especially on
>>>> 10
>>>> and 15 meters.
>>>>
>>>> So, my question is this:  Does anyone know of a fiber-glass or other
>>>> type of
>>>> non-conductive mast that I might try to get the screw-driver up higher?
>>>> Obviously, I want to be safe here, and don't want to have to mess with
>>>> guys.
>>>>
>>>> Something telescopic might be the best, but again, I would think it
>>>> would
>>>> have to be of fairly high quality.
>>>>
>>>> If anyone has any suggestions, I'll save them for future reference.
>>>>
>>>> Due to a number of other things going on right now that will put a crimp
>>>> in
>>>> the budget, I probably won't be able to do anything until next year's
>>>> camping season, but it's always good to start thinking and planning in
>>>> advance.
>>>>
>>>> 73 from Tom Behler:  KB8TYJ
>>>
>>>
>>
>
>