[TowerTalk] Hygain 18AVT trap for 20mtr/40mtr

Bob AD5VJ ad5vj at ad5vj.com
Wed Apr 14 17:24:47 PDT 2010


Ok my mind will never be the same after this I am certain.

 I just got into one of the programs and it brought up a terminology of
"winding pitch" not knowing what that was I commenced to Google it to look
it up.

I now have a headache LOL

Bob AD5VJ

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Bob AD5VJ
> Sent: Wednesday, April 14, 2010 6:39 PM
> To: 'Tower and HF antenna construction topics.'
> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> 
> I thought about that thanks for the confirmation.
> 
> Yes it is an air cap. Just the coil on a form and the al tubing the
> form is
> attached to does not even go inside the coil form more than 2-3 inches
> so it
> doesn't go all the way thru the form like I thought it would.
> 
> My understanding is after reading a bit that the outer al cover makes
> the
> cap based on its proximity to the coil. So I guess I just measure that
> carefully and should be reasonably close to the same capacitance.
> 
> Then I read about an idea here to use a cutting board for the spacer
> which I
> found on eBay for 5.00. I found the coil form there also in the form of
> some
> delrin rod that is 1/2" by 12". I found the al wire in the form of
> hobby
> wire, but it is not quite 10 awg but pretty close. Problem is the wire
> is
> only in 4 foot lengths.
> 
> So I may go with the al fence top post wire idea brought up earlier.
> 
> Then it's just making the coil up for resonance. From what I have read
> starting at the feed-point out you put the 10 meter coil then the 15
> meter
> then the 20 meter coil, then the rest of the antenna is 40 meters and
> the
> 'resonator' at the top takes care of 80 along with the top hat.
> 
> But to be honest I am not sure I want to try to do the 80 meter band
> seems
> like too much of a compromise for that band.
> 
> I remember in the old days when I had my Heathkit Apache TX-1 and
> Hallicrafters SX-111, literally loading up a window screen in my second
> story apartment for the 40 meter novice band and then I transitioned to
> an
> indoor dipole. I strung the dipole along the joint where the ceiling
> met the
> wall 18 gauge wire.
> 
> Hihi those were the good ol' days.
> 
> Bob AD5VJ
> 
> > -----Original Message-----
> > From: towertalk-bounces at contesting.com [mailto:towertalk-
> > bounces at contesting.com] On Behalf Of GEORGE CORTEZ
> > Sent: Wednesday, April 14, 2010 5:29 PM
> > To: Tower and HF antenna construction topics.
> > Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> >
> > If its anything like the way they design the traps on their
> tribanders
> > the sleeve is a air capacitor.
> > the size is not really critical but id look at the 15m trap and copy
> > the
> > size for 20 and double it for 40 as a
> > starting point. adjust the length as necessary.
> >
> > George NE2I
> >
> >
> >
> > Bob AD5VJ wrote:
> > > Hi Hans
> > >
> > > Thank you I for some reason never realized it was a linear function
> > that
> > > will certainly help me to estimate with more confidence.
> > >
> > > I in fact opened my calculator on windows 7 ultimate not expecting
> > much of a
> > > calculator but to my surprise, noticed it is much more powerful
> than
> > those
> > > versions of windows before it. There is an engineering side to it
> and
> > a
> > > converter built in. So you were exactly correct.
> > >
> > > I also found a gold mine on Google and went here:
> > > http://webpages.charter.net/crstrode/calcs/RFcalcs.htm
> > >
> > > I am playing with some of the coil and "solenoid" apps to see what
> > they will
> > > do and what they will tell me. So far the one called "trapdip" is
> > pretty
> > > cool. Just can't figure out how to get it to print other then use
> the
> > print
> > > screen function of windows.
> > >
> > > Best of all they are dos and they are free.
> > >
> > > Bob AD5VJ
> > >
> > >
> > >
> > >
> > >> -----Original Message-----
> > >> From: towertalk-bounces at contesting.com [mailto:towertalk-
> > >> bounces at contesting.com] On Behalf Of hanslg at aol.com
> > >> Sent: Wednesday, April 14, 2010 3:55 PM
> > >> To: towertalk at contesting.com
> > >> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>
> > >>
> > >>  25.4 mm = 1 inch and it is a linear function e.g. 50.8 mm = 2
> inch.
> > >> Use that calculator you (probably) have in your computer.
> > >>
> > >> 73 de
> > >>
> > >> Hans - N2JFS
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> -----Original Message-----
> > >> From: Bob AD5VJ <ad5vj at ad5vj.com>
> > >> To: 'Tower and HF antenna construction topics.'
> > >> <towertalk at contesting.com>
> > >> Sent: Wed, Apr 14, 2010 3:23 pm
> > >> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>
> > >>
> > >> John you're a genius great ideas and I appreciate them all. I like
> > the
> > >> one
> > >> about the drinking bottle especially good one there. They are easy
> > to
> > >> come
> > >> by and very adaptive and as you pointed out half of it is already
> > >> formed for
> > >> the task at hand.
> > >>
> > >> Btw I did find some software online for calculating you own coils
> > only
> > >> thing
> > >> is I don't know if it is proven or not. I have also found a mm to
> > >> inches
> > >> calculator online since the application keeps asking me questions
> in
> > >> terms
> > >> of the metric system.
> > >>
> > >> 73
> > >> Bob AD5VJ
> > >>
> > >>
> > >>> -----Original Message-----
> > >>> From: towertalk-bounces at contesting.com [mailto:towertalk-
> > >>> bounces at contesting.com] On Behalf Of John E. Cleeve
> > >>> Sent: Wednesday, April 14, 2010 1:54 PM
> > >>> To: 'Tower and HF antenna construction topics.'
> > >>> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>
> > >>> Hello Bob,
> > >>>
> > >>>   I am not familiar with Folgers Coffee cans, but as long as they
> > >>> are
> > >>> made from aluminium and not tin plate, which would eventually
> rust,
> > >>> they
> > >>> might be fine. If I were in your position, then I would consider
> > >>> literally
> > >>> "rolling" my own. That is obtaining some very thin, soft
> aluminium
> > >>> sheet,
> > >>> such as a used "offset litho printing plate" cut to shape and
> then
> > >>> rolled
> > >>> around a wooden former, if you do not have access to a set of
> > >>>
> > >> "bending
> > >>
> > >>> rolls". You could mechanically seal the two edges together just
> as
> > a
> > >>> tin can
> > >>> would be done.
> > >>>
> > >>>   Or, perhaps you might find a spun aluminium bottle shaped water
> > >>> container, in your hardware or sports store, which could be
> > purchased
> > >>> and
> > >>> sacrificed to the cause, the neck could then provide the fixture
> > for
> > >>> the top
> > >>> of the trap outer, and cutting away the base, would provide the
> > >>> aperture for
> > >>> a plastic disc to provide mechanical stability.....When you see a
> > >>> suitable
> > >>> item, you will instantly recognise its potential for adaptive
> use!
> > >>>
> > >>>   I am sure you will succeed now that you have a clear view of
> how
> > >>> the
> > >>> traps were assembled. Sadly, I cannot provide the exact resonant
> > >>> frequencies
> > >>> that each trap was tuned to, during the factory assembly, but I
> am
> > >>>
> > >> sure
> > >>
> > >>> that
> > >>> somewhere that information must be written down and
> > >>>
> > >> available......best
> > >>
> > >>> of
> > >>> luck with the restoration, sincerely, John. G3JVC.
> > >>>
> > >>>
> > >>>
> > >>> -----Original Message-----
> > >>> From: towertalk-bounces at contesting.com
> > >>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob AD5VJ
> > >>> Sent: 14 April 2010 13:57
> > >>> To: 'Tower and HF antenna construction topics.'
> > >>> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>
> > >>> Hi John
> > >>>
> > >>> The more I look into this the more I want to try to roll my own
> so
> > to
> > >>> speak.
> > >>> I didn't know that the al was used to reduce costs. So I might
> even
> > >>>
> > >> end
> > >>
> > >>> up
> > >>> with more sensitivity with copper. That a good idea thanks.
> > >>>
> > >>> I am thinking in terms of the trap covers. Not sure where to go
> > with
> > >>> this. I
> > >>> think the drink cans might be too flimsy as they are getting
> > thinner
> > >>> and
> > >>> thinner these days.
> > >>>
> > >>> Now a small metal Folgers coffee-can might work and Lord knows I
> > >>>
> > >> drink
> > >>
> > >>> that
> > >>> like its going out of style.
> > >>>
> > >>> Bob AD5VJ
> > >>>
> > >>>
> > >>>> -----Original Message-----
> > >>>> From: towertalk-bounces at contesting.com [mailto:towertalk-
> > >>>> bounces at contesting.com] On Behalf Of John E. Cleeve
> > >>>> Sent: Wednesday, April 14, 2010 7:41 AM
> > >>>> To: 'Tower and HF antenna construction topics.'
> > >>>> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>>
> > >>>> Hello Bob,
> > >>>>
> > >>>>     Pity about the missing traps, but I am glad you were able to
> > >>>> diagnose the problem with the 15m trap. Now you can see how they
> > >>>>
> > >> were
> > >>
> > >>>> made,
> > >>>> it should not be difficult to obtain plastic tube or rod to use
> as
> > >>>>
> > >>> the
> > >>>
> > >>>> former, with the added aluminium tube to fit at each end.
> > >>>>
> > >>>>     The outer trap cover forms the fixed capacitance, coupled to
> > >>>>
> > >> the
> > >>
> > >>>> coil and the lower antenna element, and the plastic spacer adds
> > >>>>
> > >> some
> > >>
> > >>>> mechanical stability; however, it may be possible to re-use
> > >>>>
> > >> aluminium
> > >>
> > >>>> drinks
> > >>>> cans, after you have drunk the contents, to form the basis of
> your
> > >>>> replacement HB traps. You will need to work out the inductance
> and
> > >>>> capacitance to work on the missing bands, but with some
> ingenuity,
> > >>>>
> > >>> and
> > >>>
> > >>>> a
> > >>>> GDO, I am sure you will succeed.  You could use copper wire of
> > >>>>
> > >>> course;
> > >>>
> > >>>> the
> > >>>> aluminium stuff was used by Hygain because it was cheaper!
> > >>>>
> > >>>>     The last resort might be to seek another 18AVT from Ebay or
> > >>>>
> > >> your
> > >>
> > >>>> friends....I have two in my garage, both destined to be used as
> > >>>>
> > >>> phased
> > >>>
> > >>>> verticals at my remote GM site, but both those came from friends
> > >>>>
> > >> who
> > >>
> > >>>> had
> > >>>> upgraded to verticals with WARC capability. The user manual for
> > the
> > >>>> 18AVT is
> > >>>> available as a .pdf on the internet.....best of luck with the
> > >>>>
> > >>> rebuild,
> > >>>
> > >>>> sincerely, John G3JVC.
> > >>>>
> > >>>>
> > >>>>
> > >>>> -----Original Message-----
> > >>>> From: towertalk-bounces at contesting.com
> > >>>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob AD5VJ
> > >>>> Sent: 14 April 2010 13:20
> > >>>> To: 'Tower and HF antenna construction topics.'
> > >>>> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>>
> > >>>> Hi John
> > >>>>
> > >>>> Excellent post!!
> > >>>> Thanks very much for sharing this.
> > >>>>
> > >>>> I had looked at one of the traps late last night and thought it
> > >>>>
> > >> can't
> > >>
> > >>>> be
> > >>>> that hard to take it apart and examine it.
> > >>>>
> > >>>> So I actually did exactly what you described. I took the 15
> meter
> > >>>>
> > >>> trap
> > >>>
> > >>>> apart
> > >>>> and it actually came apart very easily once the screws were
> taken
> > >>>>
> > >> out
> > >>
> > >>>> of the
> > >>>> one end and you turned the spacer a little.
> > >>>>
> > >>>> Just as you said one of the screws holding the inductor wire to
> > the
> > >>>> tubing
> > >>>> had rusted and released its hold on the inductor wire.
> > >>>>
> > >>>> Looks like about 12 awg wire. Now I am seriously considering
> > making
> > >>>>
> > >>> my
> > >>>
> > >>>> own
> > >>>> for 20 es 40 meters since they are missing. I could get some
> 1/2"
> > >>>> delrin rod
> > >>>> to wrap onto for the coil and the al wire. A couple of pieces of
> 1
> > >>>>
> > >>> inch
> > >>>
> > >>>> al
> > >>>> tubing and would be 90 percent home free. Now the trap cover
> might
> > >>>>
> > >> be
> > >>
> > >>> a
> > >>>
> > >>>> different story, not sure how to get that.
> > >>>>
> > >>>> The only problem is I cant find any al wire more than around 14
> > awg
> > >>>>
> > >>> and
> > >>>
> > >>>> it
> > >>>> only comes in 4 foot lengths. Need to find longer spool of wire.
> > >>>>
> > >>>> Bob AD5VJ
> > >>>>
> > >>>>
> > >>>> hn E. Cleeve
> > >>>>
> > >>>>> Sent: Wednesday, April 14, 2010 4:37 AM
> > >>>>> To: 'Tower and HF antenna construction topics.'
> > >>>>> Cc: 'Tower and HF antenna construction topics.'
> > >>>>> Subject: Re: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>>>
> > >>>>> Hello Bob,
> > >>>>>   I have used, and still have and 18AVT/WB which has served me
> > >>>>>
> > >> well
> > >>
> > >>>>> for many years, both in the UK and abroad. However, there have
> > >>>>>
> > >> been
> > >>
> > >>>>> trap
> > >>>>> problems, but all off which were repairable.
> > >>>>>
> > >>>>>   To get to the inside of the trap assembly, you undo the self
> > >>>>> tapping
> > >>>>> screw which fixes the outer cover of the trap to the antenna
> > >>>>>
> > >>> element
> > >>>
> > >>>>> assembly, then you rotate the inner plastic spacer at the
> bottom
> > >>>>>
> > >> of
> > >>
> > >>>> the
> > >>>>
> > >>>>> trap, until you can slide the entire cover etc. down and away
> > >>>>>
> > >> from
> > >>
> > >>>> its
> > >>>>
> > >>>>> original position.
> > >>>>>
> > >>>>>   This will expose the inductor, and at each end of the
> inductor
> > >>>>> you
> > >>>>> will find a self tapping screw which connects the inductor
> wire,
> > >>>>>
> > >> at
> > >>
> > >>>>> each end
> > >>>>> to the antenna element. In my example this self tapping screw
> > >>>>> originally was
> > >>>>> not made of stainless steel, and it did not have a washer
> beneath
> > >>>>>
> > >>> the
> > >>>
> > >>>>> head
> > >>>>> of the screw, and so, on assembly the screw head "bit" into the
> > >>>>> aluminium of
> > >>>>> the inductor wire, and eventually the rust from the screw and
> the
> > >>>>> stress on
> > >>>>> the inductor wire, which caused the inductor wire to fracture
> at
> > >>>>>
> > >>> the
> > >>>
> > >>>>> screw
> > >>>>> head/wire contact, that caused the problems I experienced.
> There
> > >>>>>
> > >> is
> > >>
> > >>> a
> > >>>
> > >>>>> similar situation at each end of the 80m top loading inductor
> > >>>>>
> > >> too.
> > >>
> > >>>>>   So, I suggest you obtain some new stainless steel self tap
> > >>>>> screws,
> > >>>>> plus washers. Obtain some aluminium wire of the right diameter,
> > >>>>>
> > >> and
> > >>
> > >>>>> simply
> > >>>>> rewind the inductors, only a few turns each, in grooved
> formers,
> > >>>>> carefully
> > >>>>> tighten the new self tap screws and then coat the junction of
> the
> > >>>>> screw/washer/inductor wire with a non hardening insulation, and
> > >>>>>
> > >>> then
> > >>>
> > >>>>> reassemble the outer covering, and you should be back in
> > >>>>>
> > >> business.
> > >>
> > >>>>>   Sincerely, John. G3JVC.
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> -----Original Message-----
> > >>>>> From: towertalk-bounces at contesting.com
> > >>>>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob
> AD5VJ
> > >>>>> Sent: 14 April 2010 03:08
> > >>>>> To: towertalk at contesting.com
> > >>>>> Subject: [TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
> > >>>>>
> > >>>>> I was given an old Hygain 18avt vertical and had plans on
> > >>>>>
> > >> mounting
> > >>
> > >>> it
> > >>>
> > >>>>> atop
> > >>>>> my tower since it is low profile and does well in the wind. But
> I
> > >>>>>
> > >>>> just
> > >>>>
> > >>>>> went
> > >>>>> to Hygain's website and it appears they don't stock parts for
> it.
> > >>>>>
> > >>>>> I am needing the 20 meter and 40 meter traps anyone have any
> idea
> > >>>>>
> > >>>> where
> > >>>>
> > >>>>> I
> > >>>>> can find them - Google did not find anything, unless I didn't
> put
> > >>>>>
> > >>> in
> > >>>
> > >>>>> the
> > >>>>> right words -- I just Googled "Hygain assy (and then the 870
> > >>>>>
> > >> number
> > >>
> > >>>> in
> > >>>>
> > >>>>> the
> > >>>>> manual).
> > >>>>>
> > >>>>> 73,
> > >>>>> Bob AD5VJ
> > >>>>>
> > >>>>>
> > >>>>> _______________________________________________
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> _______________________________________________
> > >>>>> TowerTalk mailing list
> > >>>>> TowerTalk at contesting.com
> > >>>>> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>>>> No virus found in this incoming message.
> > >>>>> Checked by AVG - www.avg.com
> > >>>>> Version: 9.0.801 / Virus Database: 271.1.1/2809 - Release Date:
> > >>>>> 04/13/10
> > >>>>> 21:22:00
> > >>>>>
> > >>>>> _______________________________________________
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> _______________________________________________
> > >>>>> TowerTalk mailing list
> > >>>>> TowerTalk at contesting.com
> > >>>>> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>>>>
> > >>>> _______________________________________________
> > >>>>
> > >>>>
> > >>>>
> > >>>> _______________________________________________
> > >>>> TowerTalk mailing list
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> > >>>> 21:22:00
> > >>>>
> > >>>> _______________________________________________
> > >>>>
> > >>>>
> > >>>>
> > >>>> _______________________________________________
> > >>>> TowerTalk mailing list
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> > >>>>
> > >>> _______________________________________________
> > >>>
> > >>>
> > >>>
> > >>> _______________________________________________
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> > >>> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>> No virus found in this incoming message.
> > >>> Checked by AVG - www.avg.com
> > >>> Version: 9.0.801 / Virus Database: 271.1.1/2809 - Release Date:
> > >>> 04/14/10
> > >>> 07:31:00
> > >>>
> > >>> _______________________________________________
> > >>>
> > >>>
> > >>>
> > >>> _______________________________________________
> > >>> TowerTalk mailing list
> > >>> TowerTalk at contesting.com
> > >>> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>>
> > >> _______________________________________________
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> TowerTalk mailing list
> > >> TowerTalk at contesting.com
> > >> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>
> > >>
> > >> _______________________________________________
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> TowerTalk mailing list
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> > >>
> > >
> > > _______________________________________________
> > >
> > >
> > >
> > > _______________________________________________
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> > >
> > >
> >
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> >
> >
> >
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> _______________________________________________
> 
> 
> 
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