[Lowfer] Antenna design idea question

[Stan, W1LE]

Hello Mike,

PVC pipe is also available as non-metallic conduit in the electrical 
section at Home Depot/Lowes.
I have not shopped for sched 80, only the common strength sched 40.
Electrical conduit is also more UV proof and so labeled.
I would start looking for sched 80 at a plumbing or electrical supply house.
Home Depot lengths are 10'. Jobber lengths at the supply houses are 20'.

I am happy with the low RF loss of the white plumbing PVC piping,
But I have not evaluated the grey electrical PVC conduit for RF loss.

Filling the hollow pipe, after construction, with an aerosol foam, could 
add some needed rigidity.
No idea on the added RF losses or the change in dielectric 
constant/detuning.

The short pipe reducing sections, used in the normal construction 
application, require support every few feet.
Too bad the different sizes available do not telescope nicely, then glue 
them together with a reasonable overlap.
An overlapping joint would be stronger than a pipe reduction fitting. 
TBD is the real (actual) strength needed.

A wrap of Scotch 33 or 88 electrical tape could provide a durable UV 
proofing with low RF loss.
Possibly using a sealing heat shrink tubing, could also add the UV 
protection needed.

A sealing heat shrink was used on my 80M Gadiator verticals, center 
loading coil section.
CushCraft routinely used a sealing heat shrink on their HF R5 vertical, 
coiled trap sections.
The common wires at Home Depot are not very UV proof.
MTW rated insulation, machine tool wire, nor some PVC insulations are 
durable in UV.

Just some additional thoughts.

Stan, W1LE     Cape Cod


Michael Lodico wrote:
> Hi Stan,
>
> Frequency would be 187 KHz.  The PVC would be schedule 80 for strength 
> with pipe reduction fittings rather than adapters.  I would bolt the 
> sections together so that it is more serviceable. I was planning on 
> using 24 or 26 gauge enameled coil wire although if I could find Litz  
> that wouldn't cost me my first born, hi hi, I would consider using it.  
> The overlap would be the depth of the reduction fittings but I was 
> planning on winding each section separately  and connecting them 
> together after the joints are bolted together.  This antenna would be 
> for Tx but for RX at first with plans to build an active antenna for 
> Rx.  I would also use silicon to seal the joints to keep out moisture 
> because of our temps here in KY.  As for UV protection I am hopping that 
> somebody might have some ideas of what would work without detuning the 
> antenna or causing losses.  I would model this in NEC but I am old 
> school and not that familiar with it so I guess it would be build it and 
> go from there.
>
> 73,
> Mike
> K1EG
>
> Stan, W1LE wrote:
>   
>> Hello Mike,
>>
>> I suspect lotsa folks have considered it and a few have constructed one 
>> with unpublished results.
>> Some variations have been documented, base loading, center loading and 
>> top loading.
>>
>> Depending on your working familiarity with NEC antenna modeling, 
>> consider modeling it first.
>> Or just make one and evaluate it.
>>
>> You did not mention what frequency you are planning to use.   136, 160, 
>> 190, 500 KHz ?
>>
>> For 136 KHz a wavelength is about 7200', so I hope you have a ready 
>> source of wire.
>>
>> By heavy wall PVC do you mean schedule 40 or sched 80 ?
>>
>> Sounds like an interesting venture.
>>
>> Thinking out loud:
>> Glue or bolt the sections together ?
>> What size wire with UV proof insulation ?
>> How much of an overlap of the different sections when stacking and 
>> gluing/bolting ?  1' ?
>> I assume it will be a TX antenna.
>> You will need another antenna to compare it to.
>>
>> Stan, W1LE     FN41sr     Cape Cod
>>
>>
>>
>> Michael Lodico wrote:
>>   
>>     
>>> Good morning all you Lowfer's out there.
>>>
>>> I am trying to plan for an antenna for this winter and came up with an 
>>> idea based upon what a ham did for a shortened 80 meter vertical.  The 
>>> plan is as follows:  you take a 1/2 wavelength of wire and wind it on a 
>>> rod like a solenoid so that it is shortened considerably.  He claims 
>>> that it performs quite well.
>>>
>>> What I have in mind is to take 4 lengths of PVC heavy wall pipe, 4", 3", 
>>> 2" and 1 1/2", and wind a 1/2 wavelength of wire over the 40' length.  I 
>>> would do this in 10' lengths and dope the windings in place to hold them 
>>> and then connect them together at each joint.  At the top I would add a 
>>> 10' diameter capacitor hat.  By using the different diameters this gives 
>>> me  anchor points for  Dacron guys.
>>>
>>> My question is has anybody tried this?  Is it a feasible design idea 
>>> worth pursuing?  Any comments or feedback would be greatly appreciated.
>>>
>>> 73,
>>> Mike
>>> K1EG
>>> ______________________________________________________________
>>>     
>>>       
>
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