[TowerTalk] Hygain 18AVT trap for 20mtr/40mtr
GEORGE CORTEZ
ne2i at optonline.net
Wed Apr 14 15:29:24 PDT 2010
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
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
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>>>>>
>>>>>
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