Us inverted L users must be thinking alike these days!
I've started on this same project and decided to build my own coil/cap trap
to use my 160m inverted L on 80m using ON4UN's Low Band DXing book as a
guide.
This was my thought process:
1. I have been using the Reyco traps for almost 3 years on my 80/40/17
inverted vee. They work quite well, but I what I don't like about them is
the mechanical and electrical connection to the rest of the antenna and the
seemingly small aluminum wire size used for the trap (I guess about 16
gauge, US).
2. While coaxial cable traps seem to be all the rage, with slightly above
average fractional db losses (per trap), I've taken a contrarian view. In
my early days of ham radio, I would have given up a few fractions of a db
here and there. Now, I am working on removing these few fractions of a db
loss, since after a while they start to add up. Plus they help for both
receive and transmit. My current station is more of a rabbit, even after
running 500W. I think the weight of a coaxial trap can be a negative as
well.
This all lead me to the "roll your own" approach. Not having to build two
identically matching traps is also a benefit.
73,
Cliff K3LL/6
> -----Original Message-----
> From: topband-bounces@contesting.com [mailto:topband-
> bounces@contesting.com] On Behalf Of Joe Subich, W4TV
> Sent: Saturday, September 26, 2009 8:40 AM
> To: 'Alex'; topband@contesting.com
> Subject: Re: Topband: INV-L with traps
>
>
> If you already have a wire inverted L, it's not that
> hard to convert to a trapped antenna using either the
> Reyco traps or home made coaxial traps. See the info
> from K1ZM many years ago concerning the wire version
> of the BC Special:
> http://lists.contesting.com/_topband/1998-02/msg00057.html
>
> I'm including an edited version of the AA8U "Ugly-as-L
> Dxpedition Antenna" using Reyco (Unadilla) traps since I
> can't find the original e-mail in the archives. Some have
> reported problems with trap failure when running high power.
> The Reyco traps seem to survive reasonable power levels but
> not "big" amplifiers.
>
> The Reyco/Unadilla available from many amateur shops seem
> to be the only off the shelf wire antenna traps covering
> all of the HF bands I can find these days.
>
> 73,
>
> ... Joe, W4TV
>
>
>
> > -----Original Message-----
> > From: Bruce (AA8U)
> > Subject: "Ugly-as-L" DXpedition Antenna
> >
> >
> > I have been building an antenna to take on a DXpedition in
> > July to the South Cook Islands. I have received many requests
> > for dimensions and construction details since this design was
> > first mentioned on the reflector.
> >
> > This design evolved from a simple 160M inverted-L to its
> > present four-band form, as I realized we would likely have
> > some restrictions placed on the number of antennas we could
> > erect at the Rarotongan Resort Hotel.
> >
> > The first 160M version was a straight forward 234/f length
> > antenna with 60' vertical and the rest horizontal. It only
> > had 5 ground radials, each 133' spread out and laying on the
> > ground. It was fed with a 28:50 ohm Un-Un (W2FMI design). As
> > I added traps to get additional bands, the overall length
> > decreased. I think the single band antenna would probably
> > perform slightly better than the final version.
> >
> > Bandwidth is adequate on the final version, but not generous,
> > except for the narrow 30M band.
> >
> > Ground losses for this design haven't been measured.
> >
> > The feed point resistances and SWR figures below were
> > obtained at the feed point using an MFJ-259 Antenna Analyzer.
> > A real nifty piece of test equipment!!! It has a calibration
> > error on the bands tested as indicated in the notes below. It
> > does give reliable indications when this factor is taken into
> > account.
> >
> > ==============================================================
> > Dimensions To Trap Centers Fo SWR Feedpoint R
> > --------------------------------------------------------------
> > Feed point to KW-30 = 21' 4" 10.12 mHz. 1.10:1 50
> > KW-30 to KW-40 = 7' 8" 7.05 mHz. 1.15:1 44
> > KW-40 to KW-80CW = 23' 3.61 mHz. 1.20:1 36
> > KW-80 to insulator = 39' 1" 1.83 mHz. 1.60:1 28
> >
> > MFJ-259 resistance calibration: 50 ohms = approx. 42 ohms
> > actual @ 1.0:1 SWR.
> >
> > Feed point 1' 6" above ground, mounted on short ground rod 2'
> > in earth.
> >
> > Radials: 5 @ 133'
> > 5 @ 68'
> > 10 @ 33'
> >
> > Wire use for the radiator and radials is #14 MTW (600 V
> > Insulation). Using bare copper wire for the radiator will be
> > require these dimensions to be increased by about 2%.
> >
> > ################################################################
> > # The "Ugly-as-L" 160/80/40/30M DXpedition Inverted-L #
> > # Antenna Designed and tested by AA8U #
> > ################################################################
> > # Tall Tall #
> > # Tree HI-Q Insulator HI-Q Insulator Tree #
> > # O---Dacron---====....39'1"........====------5/32"Dacron----O #
> > # [=] KW-80CW #
> > # : #
> > # : #
> > # : #
> > # : 23' #
>
> > # : #
> > # : #
> > # : #
> > # [=] KW-40 #
> > # : #
> > # : 7' 8" #
> > # : #
> > # [=] KW-30 #
> > # : #
> > # : #
> > # : 21' 4" #
> > # : #
> > # : #
> > # X feed point (w/28:50 Un-Un on 160M) #
> > # : 1' 6" #
> > # _____________radials__________________________________ #
> > # (on ground) #
> > ################################################################
>
>
>
>
>
> > -----Original Message-----
> > From: topband-bounces@contesting.com
> > [mailto:topband-bounces@contesting.com] On Behalf Of Alex
> > Sent: Saturday, September 26, 2009 9:33 AM
> > To: 'cris blak'; topband@contesting.com
> > Subject: Re: Topband: INV-L with traps
> >
> >
> > Hi Cristi,
> >
> > What a coincidence! I just finished building 80m and 40m
> > traps last night myself and was going to build the "Battle
> > Creek Special" this weekend. I have already an inverted L
> > (coaxial version), but supports in my small backyard are hard
> > to come by and always thought it was a waste to use the one
> > 60ft support I use for the inverted L for just one band (and
> > the radials!).
> >
> > There are a lot of myths out there about traps being very
> > lossy (just like with anything else in hamradio). Some of
> > these myths are propagated by antenna manufactures who sell
> > antennas without traps. The loss incurred by traps is
> > actually not all that great. I found this article by W8JI very
> > helpful:
> >
> > http://www.w8ji.com/traps.htm
> >
> > That pretty much convinced me to go ahead and build the
> > Battle Creek Special to get the best bang for my buck (and
> > who can't use that these days). The loss for coaxial traps
> > seems to be about 1.6 dB for TWO traps (he evaluates
> > dipoles). Of course some will cry tears over that kind of loss.
> >
> > The nice thing about the BCS antenna is that it will fit
> > using the same supports I have now for the coaxial inverted
> > L, which is only 125 feet in length.
> >
> > I have no experience to share with you, but I thought it was
> > funny that you were thinking and doing the same thing at the
> > same time. :)
> >
> > 73,
> > --Alex KR1ST
> > http://www.kr1st.com
> > http://www.airlinkexpress.org
> >
> >
> > > -----Original Message-----
> > > From: topband-bounces@contesting.com [mailto:topband-
> > > bounces@contesting.com] On Behalf Of cris blak
> > > Sent: Friday, September 25, 2009 5:09 PM
> > > To: topband@contesting.com
> > > Subject: Topband: INV-L with traps
> > >
> > > Hello,
> > >
> > > I have an INV-L for 160m which is working fine along with its 30
> > > radials. The vertical part is about 16m. I intend to add
> > two traps in
> > > order to use it on 80m and 40m. Is there anybody who use
> > such a design
> > > for DX (meaning "in practice"). What is the difference in terms of
> > > quality between an 160m INV-L and an 160m INV-L with trap or traps
> > > (80/40m)? I already build the traps for 80 and 40m with
> > RG58 coaxial
> > > cable and tune it with my miniVNA. The Q factor is around 20.
> > >
> > > Thanks for any advice/ report.
> > >
> > > 73 de YO3FFF
> > > Cristi
> > >
> > >
> > >
> > > _______________________________________________
> > > Topband mailing list
> > > Topband@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/topband
> >
> > _______________________________________________
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>
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