Butch:
The RV is metal, hence the probable need for a conductive mast.
This is what I originally tried to do with a piece of pipe that got the
entire antenna above the roof line.
My problem, then, was that that pipe seemed to become part of the antenna,
and I was unable to tune the thing on 10, 15, or 17 meters, no matter what I
tried.
This is why I'm now leaning toward some sort of a telescopic mast that I can
maybe raise or lower to get the right conbination of elements for proper
tuning on the bands I want to operate.
Kind of tricky for sure.
This will be a long-term project that I will work on as I can in the coming
months, so I may be tapping into people's wisdom here from time to time as I
proceed.
I am getting the impression, though, that a conductive mast continues to be
the best way to go, given that my RV is metal.
73 from Tom Behler: KB8TYJ
----- Original Message -----
From: "Butch Bussen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 16, 2011 8:13 AM
Subject: Re: Need suggestions for better mast arrangement to safely raise HF
screw-driver antenna on RV
>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
>>>>
>>>>
>>>
>>
>>
>
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