Hereâ??s the not-awaited pre-report of our
thinking about a 2016 Utah desert DXPedition.
<http://www.durenberger.com/documents/PRESBT2016.pdf>http://www.durenberger.com/documents/PRESBT2016.pdf
Sass back as appropriate.
Cheers!
Mark Durenberger
There's SO much I don't want to know!
From: <mailto:neilkaz58@xxxxxxxxx>Neil Kazaross
Sent: Monday, March 14, 2016 12:21 PM
To: <mailto:markwa1ion@xxxxxxx>Mark Connelly
Cc: <mailto:contiba@xxxxxxxxx>contiba@xxxxxxxxx
; <mailto:nhp@xxxxxxxx>nhp@xxxxxxxx ;
<mailto:bportzer@xxxxxxxxxxx>Bruce Portzer ;
<mailto:charlesh3@xxxxxxx>Charles Hutton ;
<mailto:bw@xxxxxxx>Bill Whitacre ;
<mailto:dx@xxxxxxxxxxxxx>Guy Atkins ;
<mailto:Mark4@xxxxxxxxxxxxxxx>Mark Durenberger ;
<mailto:mauno.ritola@xxxxxxxxx>Mauno Ritola ;
<mailto:ibbmon.kre@xxxxxxxxx>ibbmon.kre@xxxxxxxxx
; <mailto:victor.goonetilleke@xxxxxxxxx>Victor Goonetilleke
Subject: Re: Bowtie twisted loop
Embedded comments prefaced by (KAZ)
I agree with Neil's observation about need to
vary termination resistance remotely based on
the Bowtie experiments I did here in 2010.
Drawing:
<http://www.qsl.net/wa1ion/pictures1/bowtie_s_yarmouth.gif>http://www.qsl.net/wa1ion/pictures1/bowtie_s_yarmouth.gif
That one had about a 4:1 horizontal / vertical aspect ratio.
I used in-shack termination rather than Vactrol
since I wanted to pattern-switch and possibly
even phase the east side feedline against the
west side for "surgical" single-pest removal during live DX.
(KAZ) Phasing one end against the other
basically maintains the pattern but generates a
deeper null than is possible with Rt alone.
However, said null is very narrowband. If I had
a small yard and did have the SDR need for
wideband F/B I'd certainly phase one end vs the
other as I believe it is the best use of the antenna for a single freq.
Based on this discussion I don't think feedline
pick-up had much of a role in making the
termination resistance for best lowband results
(NY 570, 660, etc.) different from that needed
to take down highband pests (NY 1190, 1280,
1560). It seems that this is inherent to the
antenna and isn't likely to be improved by going
Vactrol, at least with my relatively short (100
ft. / 30m) speaker wire feedlines.
(KAZ) I'm not convinced that we're sure that a
Vactrol won't provide at least slightly better
or more broadbanded F/B with a fixed setting. ie
ideal for Perseus to record the entire band.
Mark if it isn't too much trouble, I recommend
setting up initially with a Vactrol so you can
establish a baseline for how deep nulls can be
and also whether the null can be acceptable at
from 570 to 1560 with a single setting of Rt.
Then you'll know with certainly if things
degrade with you switch to the dual feed line and pot method.
As I think Bruce's small lot would also result
in short feedline lengths, I think that the way
to go would be dual feedlines and in-shack pot
termination, the same as what I do here on the
TA SuperLoop and eventually also on the Bowtie that will replace it.
(KAZ) Then Bruce could phase one end vs the
other as desired for enhancement of F/B vs specific pests.
I also think that if the feedpoints need to be
more than about 8 ft. above ground, you might as
well just have them halfway up the sides and be
done with it. With any luck you won't have to
drop the antenna for maintenance that often once
everything is operational. Obviously you want
your transformer boxes and all connections thereto robust / weather-hardy.
(KAZ) I agree as my modeling shows that Bruce's
antenna should perform significantly better with center feed and terminated.
The Bowtie I'll be putting up soon, in roughly
the same location as the 2010 one, should be
about 3:1 aspect, 90 ft. / 27m horizontal to 30
ft. / 9m vertical. The plan is for the bottom
corners of the antenna to be about 5-6 ft. above
ground and the tops 35-36 ft. with UV-resistant
dacron ropes over the tops of the black locust trees up around 50 ft.
Feedpoints in the center of each vertical side
with 9:1 transformers initially installed to
supply speaker-wire feedlines to the in-shack
500 ohm termination pot switch-swappable with
2:1 transformer to W7IUV amp to receiver (or
phaser, with south SuperLoop being 'input B').
(KAZ) My modeling and live experience phasing a
west loop vs a south one for example, do show
that while you can null a specific pest, the
resultant pattern isn't very good. Of course
this can luck out along the coast when the DX is
from one wide beam direction but is unacceptable
here in the Midwest where I need a more narrow
beamwidth and a clean pattern. Better to phase
one end vs the other if you need to crush a NYC pest down 40-50 dB for example.
Fortunately the area between the trees is
primarily open grass and vegetable garden plots
about 20 ft. ahead of the barn / workshop.
At some point I could think of going over to a
Vactrol scheme with DC passed out on the east
feedline and choke-coupled through the antenna
elements to get to the Vactrol box halfway up
the west side. This will be an offshoot of
what's shown in my 2000 Pennant article:
<http://www.qsl.net/wa1ion/doc1/pennant.pdf>http://www.qsl.net/wa1ion/doc1/pennant.pdf
That method gets rid of any need for a separate
control line heading to the termination end
(west, more or less, in my case). You do, of
course, give up the switchable pattern reversal
so this method would only come into play if
there was a clear advantage in null-depth /
broadbandedness versus the dual feedline approach.
(KAZ) This is convenient but I presume can't be
used with amplification at the feed point like
Bill and I and some others here do with the FLG100LN.
At this time Chuck Hutton, Bill Whitacre, Colin
Newell, and a few others have been hashing over
different variations on Vactrol control
circuits. Smoothness of operation in the
typical 400-1600 ohm termination range, along
with circuit simplicity and low cost, are key
topics. It will be interesting to see what comes out of that.
There is a lot of good circuit modelling, d-i-y,
and real-world DXpeditioning research going on
with people on this distribution as well as guys
like Lankford and hams on the Topband list. Not
even to mention Gary DeBock's unique world of portable receiver enhancements.
An interesting time in a hobby that isn't ready
to roll over and play dead yet.
(KAZ) Believe me, this hobby isn't dead yet!
On Sat, Mar 12, 2016 at 10:46 PM, Mark Connelly
<<mailto:markwa1ion@xxxxxxx>markwa1ion@xxxxxxx> wrote:
I agree with Neil's observation about need to
vary termination resistance remotely based on
the Bowtie experiments I did here in 2010.
Drawing:
<http://www.qsl.net/wa1ion/pictures1/bowtie_s_yarmouth.gif>http://www.qsl.net/wa1ion/pictures1/bowtie_s_yarmouth.gif
That one had about a 4:1 horizontal / vertical aspect ratio.
I used in-shack termination rather than Vactrol
since I wanted to pattern-switch and possibly
even phase the east side feedline against the
west side for "surgical" single-pest removal during live DX.
Based on this discussion I don't think feedline
pick-up had much of a role in making the
termination resistance for best lowband results
(NY 570, 660, etc.) different from that needed
to take down highband pests (NY 1190, 1280,
1560). It seems that this is inherent to the
antenna and isn't likely to be improved by going
Vactrol, at least with my relatively short (100
ft. / 30m) speaker wire feedlines.
As I think Bruce's small lot would also result
in short feedline lengths, I think that the way
to go would be dual feedlines and in-shack pot
termination, the same as what I do here on the
TA SuperLoop and eventually also on the Bowtie that will replace it.
I also think that if the feedpoints need to be
more than about 8 ft. above ground, you might as
well just have them halfway up the sides and be
done with it. With any luck you won't have to
drop the antenna for maintenance that often once
everything is operational. Obviously you want
your transformer boxes and all connections thereto robust / weather-hardy.
The Bowtie I'll be putting up soon, in roughly
the same location as the 2010 one, should be
about 3:1 aspect, 90 ft. / 27m horizontal to 30
ft. / 9m vertical. The plan is for the bottom
corners of the antenna to be about 5-6 ft. above
ground and the tops 35-36 ft. with UV-resistant
dacron ropes over the tops of the black locust trees up around 50 ft.
Feedpoints in the center of each vertical side
with 9:1 transformers initially installed to
supply speaker-wire feedlines to the in-shack
500 ohm termination pot switch-swappable with
2:1 transformer to W7IUV amp to receiver (or
phaser, with south SuperLoop being 'input B').
Fortunately the area between the trees is
primarily open grass and vegetable garden plots
about 20 ft. ahead of the barn / workshop.
At some point I could think of going over to a
Vactrol scheme with DC passed out on the east
feedline and choke-coupled through the antenna
elements to get to the Vactrol box halfway up
the west side. This will be an offshoot of
what's shown in my 2000 Pennant article:
<http://www.qsl.net/wa1ion/doc1/pennant.pdf>http://www.qsl.net/wa1ion/doc1/pennant.pdf
That method gets rid of any need for a separate
control line heading to the termination end
(west, more or less, in my case). You do, of
course, give up the switchable pattern reversal
so this method would only come into play if
there was a clear advantage in null-depth /
broadbandedness versus the dual feedline approach.
At this time Chuck Hutton, Bill Whitacre, Colin
Newell, and a few others have been hashing over
different variations on Vactrol control
circuits. Smoothness of operation in the
typical 400-1600 ohm termination range, along
with circuit simplicity and low cost, are key
topics. It will be interesting to see what comes out of that.
There is a lot of good circuit modelling, d-i-y,
and real-world DXpeditioning research going on
with people on this distribution as well as guys
like Lankford and hams on the Topband list. Not
even to mention Gary DeBock's unique world of portable receiver enhancements.
An interesting time in a hobby that isn't ready
to roll over and play dead yet.
Mark Connelly, WA1ION
South Yarmouth, MA
-----Original Message-----
From: Neil Kazaross <<mailto:neilkaz58@xxxxxxxxx>neilkaz58@xxxxxxxxx>
To: Bruce Conti <<mailto:contiba@xxxxxxxxx>contiba@xxxxxxxxx>
Cc: Nick Hall-Patch
<<mailto:nhp@xxxxxxxx>nhp@xxxxxxxx>; Mark
Connelly
<<mailto:markwa1ion@xxxxxxx>markwa1ion@xxxxxxx>;
Bruce Portzer
<<mailto:bportzer@xxxxxxxxxxx>bportzer@xxxxxxxxxxx>;
Charles Hutton
<<mailto:charlesh3@xxxxxxx>charlesh3@xxxxxxx>;
Bill Whitacre <<mailto:bw@xxxxxxx>bw@xxxxxxx>;
Guy Atkins
<<mailto:dx@xxxxxxxxxxxxx>dx@xxxxxxxxxxxxx>;
Mark Durenberger
<<mailto:Mark4@xxxxxxxxxxxxxxx>Mark4@xxxxxxxxxxxxxxx>;
Mauno Ritola
<<mailto:mauno.ritola@xxxxxxxxx>mauno.ritola@xxxxxxxxx>;
Vlad Titarev
<<mailto:ibbmon.kre@xxxxxxxxx>ibbmon.kre@xxxxxxxxx>;
Victor Goonetilleke
<<mailto:victor.goonetilleke@xxxxxxxxx>victor.goonetilleke@xxxxxxxxx>
Sent: Sat, Mar 12, 2016 6:24 pm
Subject: Re: Bowtie twisted loop
Hopefully TA cx improve and you can do a good
test. But for now, how much, if at all, do you
think back end QRM has been reduced? Are you
getting stations from Maine better than before?
I do think you'll want some way to vary Rt from
the shack. This is probably more important for
your compromise antenna than for ones with full dimensions.
73 KAZ
On Sat, Mar 12, 2016 at 1:44 PM, Bruce Conti
<<mailto:contiba@xxxxxxxxx>contiba@xxxxxxxxx> wrote:
On Sat, Mar 12, 2016 at 6:47 PM, Neil Kazaross
<<mailto:neilkaz58@xxxxxxxxx>neilkaz58@xxxxxxxxx> wrote:
My modeling shows that you'd clearly improve
things if you could feed and terminate this at
the centers of the ends. However, I found a
decent compromise for you and that is to feed
and terminate it 22% of the way up... In that
case the end radials do help... The issues here
are that the aspect ratio is too low for best
patterns. But if you go to something like a 3:1
aspect ratio then you have 20 ft x 60 ft and
that won't provide much low end signal. If only
you had a couple of usable trees 90 or 100 ft apart!
Thanks for taking a look. I wish I had 100-ft
or more room for antennas. My lot is only 100 x
100-ft, and I have to use the trees toward a
back corner of the lot, otherwise the antenna
would be too close to power lines and houses, in
addition to becoming too visible. The
termination and matching transformer are
actually about 5% or 2-ft of the way up if that
makes any difference. Can't reach any higher
with the ladder, and lowering the height of the
antenna would make it too conspicuous. Being in
a city lot and antenna restrictive private
neighborhood requires many compromises in antenna design.
--
Bruce Conti
B.A.Conti Photography <http://www.baconti.com>www.baconti.com
¡BAMLog! <http://www.bamlog.com>www.bamlog.com