[GreenKeys] On PVC poles

Fri Jul 17 19:20:09 EDT 2020

    If the antenna is a resonant circuit high Q would mean narrow 
band, however, if there is a coupled circuit it may be the case. 
I don't remember exactly how these antennas are supposed to work 
other than it sounds like using a distributed inductance to get 
slower wave propagation along the length thus increasing the 
effective length of the antenna. I would think high losses would 
negate whatever advantage there is in the method.

On 7/17/2020 4:04 PM, hwhall at compuserve.com wrote:
> Actually the original question is whether PVC would be an 
> acceptable support material for a spiral (linearly loaded) 
> antenna that can be concealable.
>
> Unless I'm mistaken, doesn't a hi-Q antenna normally mean a 
> narrow-band antenna which is usually not exactly what the 
> average amateur is looking for? And apparently not what the 
> original poster is looking for (he deemed magnetic loops to be 
> too hi-Q).
>
> I recall the original post's concern was "concealable", hence a 
> usable though less than optimal antenna. More power input may 
> be needed to communicate as well as a full sized optimal 
> antenna but it can be made to work. I suggest building the PVC 
> antenna & see if it gets too hot. I see an awful lot of 
> articles on building antennas wound onto PVC pipe material.
>
> Wayne
> WB4OGM
>
> -----Original Message-----
> From: Richard Knoppow <1oldlens1 at ix.netcom.com>
> To: greenkeys at mailman.qth.net
> Sent: Fri, Jul 17, 2020 1:30 pm
> Subject: Re: [GreenKeys] On PVC poles
>
>    I have lost something in this thread. It appears to be about
> the effect on the loss of a coil when winding it on a plastic
> former. In fact, even at communications frequencies, that is
> 30Mhz and below, the coil former has an definite effect on Q. For
> frequencies above about 10Mhz a very low loss material like
> polystyrene is necessary. There may be other plastics with
> similarly low loses.
>    Keep in mind that the loss is not just a matter of some power
> loss but of the effect on the Q of the inductor. If the reactance
> and resonance is important to the function of the antenna the Q
> may be critical and losses in the former are important.
>    There are charts showing losses of various materials on the
> web. Make sure the loss is measured at the range of frequencies
> you are going to use. A Q meter is very helpful with practical
> materials.
>
> On 7/17/2020 6:21 AM, Bob kb8tq wrote:
> > Hi
> >
> > What frequency(s) is the antenna targeted at? For < 30 MHz, 
> just about anything
> > that is “plastic” will be reasonably low loss. Consider that 
> a lot of people have
> > trapped antennas with trap Q’s around 10 to 20. They seem to 
> work fine.
> >
> > If you are building something for UHF then indeed the 
> “microwave test” makes
> > a lot of sense.
> >
> > =====
> >
> > When you do the “coil” part of the helical, turn spacing is 
> one of the variables.
> > You may find that a wide spaced coil works better than a 
> close wound one.
> >
> > Bob
> >
> >> On Jul 16, 2020, at 11:50 PM, Dave Horsfall 
> <dave at horsfall.org <mailto:dave at horsfall.org>> wrote:
> >>
> >> (Somewhat on topic, as I did use "glass" RTTY[*] some years 
> ago, and am trying to find room for a real one).
> >>
> >> I have a need to make a helical (easily concealed etc), but 
> I am somewhat baffled by "common knowledge" so I figured that 
> this list is the best resource :-)  A magnetic loop is too 
> directional for my tastes, as is also far too high-Q i.e. needs 
> to be re-tuned if you shift by a just a few kHz.
> >>
> >> Metal is obviously right out, and I understand so is wood 
> (because of its water content), so I thought about a length of 
> PVC pipe with the helical wound around it.
> >>
> >> Now, herein lies the tale...
> >>
> >> Apparently PVC pipe may or may not contain carbon, and the 
> only way to find out (apart from deciphering the manufacturer's 
> code) is to place piece of it inside a microwave oven (with the 
> wife not looking) with a glass of water to act as a dummy load 
> to protect the magnetron.
> >>
> >> If the PVC is warm, it contains carbon and is therefore 
> unsuitable...
> >>
> >> So, what is the veracity of this claim?
> >>
> >> [*]
> >> And yes, I know about the CR/LF problem, as with 72 columns.
> >>
> >> -- Dave VK2KFU
> >> ______________________________________________________________
> >> GreenKeys mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:GreenKeys at mailman.qth.net 
> <mailto:GreenKeys at mailman.qth.net>
> >>
> >>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: 
> https://teletype.net/gksearch
> >>>>> 2002-to-present greenkeys archive: 
> http://mailman.qth.net/pipermail/greenkeys/
> >>>>> 1998-to-2001 greenkeys archive: 
> http://mailman.qth.net/archive/greenkeys/greenkeys.html
> >>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: 
> http://comcents.com/tty/greenkeyssearch.html
> >> This list hosted by: http://www.qsl.net <http://www.qsl.net/>
> >> Please help support this email list: 
> http://www.qsl.net/donate.html
> >> Message delivered to kb8tq at n1k.org <mailto:kb8tq at n1k.org>
> > ______________________________________________________________
> > GreenKeys mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:GreenKeys at mailman.qth.net 
> <mailto:GreenKeys at mailman.qth.net>
> >
> >>>> Jordan Spencer Cunningham's GreenKeys Search Tool: 
> https://teletype.net/gksearch
> >>>> 2002-to-present greenkeys archive: 
> http://mailman.qth.net/pipermail/greenkeys/
> >>>> 1998-to-2001 greenkeys archive: 
> http://mailman.qth.net/archive/greenkeys/greenkeys.html
> >>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: 
> http://comcents.com/tty/greenkeyssearch.html
> > This list hosted by: http://www.qsl.net <http://www.qsl.net/>
> > Please help support this email list: 
> http://www.qsl.net/donate.html
> > Message delivered to 1oldlens1 at ix.netcom.com 
> <mailto:1oldlens1 at ix.netcom.com>
>
> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com <mailto:1oldlens1 at ix.netcom.com>
> WB6KBL
>
>
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net 
> <mailto:GreenKeys at mailman.qth.net>
>
> >>> Jordan Spencer Cunningham's GreenKeys Search Tool: 
> https://teletype.net/gksearch
> >>> 2002-to-present greenkeys archive: 
> http://mailman.qth.net/pipermail/greenkeys/
> >>> 1998-to-2001 greenkeys archive: 
> http://mailman.qth.net/archive/greenkeys/greenkeys.html
> >>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: 
> http://comcents.com/tty/greenkeyssearch.html
>
> This list hosted by: http://www.qsl.net <http://www.qsl.net/>
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to hwhall at compuserve.com 
> <mailto:hwhall at compuserve.com>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL