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CX2SA > SATDIG 23.09.08 01:53l 458 Lines 12941 Bytes #999 (0) @ WW
BID : 35637_CX2SA
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Subj: AMSAT-BB-digest V3 479
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Sent: 080922/2344Z @:CX2SA.LAV.URY.SA #:35637 [Minas] FBB7.00e $:35637_CX2SA
From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: Duplexer for Sats (David - KG4ZLB/M?ZLB)
2. Re: Polarity questions (i8cvs)
3. Re: Duplexer for Sats (Jim Jerzycke)
4. Re: FOR SALE ICOM IC-W32A (Stuart Underwood)
----------------------------------------------------------------------
Message: 1
Date: Mon, 22 Sep 2008 12:31:38 -0400
From: David - KG4ZLB/M?ZLB <m0zlb(AT)btinternet.com>
Subject: [amsat-bb] Re: Duplexer for Sats
To: amsat-bb(AT)amsat.org
Message-ID: <48D7C86A.3060105(AT)btinternet.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
A closer look at that document reveals that it was written in September
2006 and towards the end of it mention is made of the possibility of a
second article about tweaking the standard Arrow for more gain - does
anyone know if that article has been written/published or, for that
matter, does anyone have any links to sites that describe Arrow
modifications?
Thanks
David
KG4ZLB
Pughkeithd(AT)cs.com wrote:
> In a message dated 9/22/2008 10:41:01 AM Central Daylight Time,
> satkins(AT)inetdesign.org writes:
>
> Stephen,
>
> Check this out: http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf
>
> A duplexer is built as part of the antenna combination, but could be done
> separately if necessary. Any 50 ohm coax and connectors could be used.
This one
> does feature inductors wound on a pencil.
>
> 73 - Keith, W5IU
>
> _______________________________________________
> Sent via AMSAT-BB(AT)amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
>
--
*David*
*KG4ZLB/M?ZLB*
*www.kg4zlb.com <http://www.kg4zlb.com/>*
*www.m?zlb.com <http://www.m0zlb.com/>*
------------------------------
Message: 2
Date: Mon, 22 Sep 2008 18:32:09 +0200
From: "i8cvs" <domenico.i8cvs(AT)tin.it>
Subject: [amsat-bb] Re: Polarity questions
To: "AMSAT-BB" <amsat-bb(AT)amsat.org>, "Joe" <nss(AT)mwt.net>
Cc: Angus <angus(AT)young5769.freeserve.co.uk>
Message-ID: <005001c91cd0$c3249660$0201a8c0(AT)tin.it>
Content-Type: text/plain; charset="iso-8859-1"
Hi Joe WB9SBD
At the beginning of TV the television set were feed with a 300 ohm
twin lead.
Since the theory of transmission lines is not changed one method to
eliminate TVI was to connect in parallel to the above feed line a 1/4
electrical wave of 300 ohm twin lead cut for the interfering frequency
and with the other end open.
At the interfering frequency the above resonant 1/4 wave transmission
line with open end represented a short circuit at the interfering
frequency
across the input of the television set.
Another method was to connect the same way a 1/2 electrical wave
of 300 ohm twin lead cut for the interfering frequency but with the other
end short circuited.
Since a 1/2 wave represents a full turn around the Smith Chart then
the short circuit made at the other end was seen as a short circuit for
the interfering frequency just at the input of the television set.
If you like to use the above setup for 300 ohm twin lead then you
must use a balun to connect the unbalanced coax cable coming
from the signal generator to a balanced transmission line as a 300
ohm twin lead.
Best 73" de
i8CVS Domenico
----- Original Message -----
From: Joe
To: i8cvs
Cc: Angus ; AMSAT-BB
Sent: Monday, September 22, 2008 2:19 AM
Subject: Re: [amsat-bb] Re: Polarity questions
Howdy all,
I Have a question,,
Will the below set up work with 300 ohm TV type of twin lead?
Joe WB9SBD
i8cvs wrote:
Hi Gus
To know the velocity factor of a coax (known or un-known ) with good
accuracy I make the measurement at about 30 MHz because the velocity
factor do not change with frequency and a low frequency measurement
make the error the smallest as possible.
Get a N coax T and connect the male port of it to the vertical Y channel
of
an oscilloscope.
A spectrum analyser is not necessary because any oscilloscope works at
30 MHz
Connect one female port of the T connector to a RF generator and set it
to 30 MHz
If you don't have a RF signal generator use a low power 30 MHz TX at
1 or 2 watt output power or less using few suitable 50 ohm attenuators.
Connect the other female port of the T connector to an estimated 1/4
electrical wave long of coax cable under test and live open the other
end of it.
______________ _______________
| | | 30 MHz |
| Oscilloscope | | signal generator |
| | | or low power TX |
|___________Y_ | |_______________|
1/4 Lambda /\| \/
open o------------|------------------------|
end T connector
If you suspect that the velocity factor is 0.66 like for solid
polyethylene
(PE) make the 1/4 electrical wave at 30 MHz 1.65 meters i.e. 65" long
The measurement plane of the coax cable under test is the middle of
the T connector just between both female ports where the generator
and the coax under test get in contact each other so that the real lenght
of 1/4 electrical lenght must be taken from the above measurement
plane including the male N connector up to the open end of it.
Because of the theory of transmission line and following the Smith
Chart we see that a 1/4 electrical wave long transmission line becames
a short circuit at his resonating frequency when the other end of it is
open.
While looking at the CRT of the oscilloscope adjust the frequency
of the signal generator until the amplitude of the signal on the CRT
falls abruptly to zero.
The frequency shown by the signal generator is the resonant frequency
of the 1/4 electrical wave.
Knowing the frequency and the physical lenght of 1/4 wave it is
easy to calculate the real velocity factor of the coax cable under test.
No special instruments are necessary because about everyone own a
signal generator for 30 MHz and a CRT oscilloscope.
Using a GDO or an antenna analyser the measurement can be wrong
because it is difficult to know if the above instruments made for
amateur use are well calibrated or not.
73" de
i8CVS Domenico
----- Original Message -----
From: "Angus" <angus(AT)young5769.freeserve.co.uk>
To: <AMSAT-BB(AT)amsat.org>
Sent: Sunday, September 21, 2008 7:57 AM
Subject: [amsat-bb] Re: Polarity questions
Hmmmmm might get shot down in flames for this but.
If you want to know the velocity factor of a coax (known or un-known) try
getting two eaqual lengths of coax which are physically 1/4wavelength long
i.e. 50cms for 2mtrs.
Short out ONE end (join the inner and outers together with a short a link
as
possible) and do this for both pieces of coax.
We are going to make a coaxial dipole so these two shortened ends go on to
a
piece of feeder (try and keep this feeder as short as possible also but
the
dipole needs to be somewhere clear but does not to be 100 feet up either).
Yes you will need to support the dipole elements as they will just hang
down
so perhaps a piece of garden cane or some other RF invisible material.
Trim back both OPEN ends of the dipole until you get the lowest possible
VSWR (on the centre frequency you want to use) and you should have very
close to an electrically 1/2wave dipole for the coax you used (each side
of
the dipole will be a 1/4 wave long). You can use these figures for making
a
1/4wave delay line or if your making a polarity control box you will need
to
know the lengths of both 1/2 and 1/4 of the coax you are going to use, the
dipole will be considerably shorter than a normal wire dipole for the same
frequency because we have used the velocity factor to help reduce its
length.
If you think that the feeder you have used is radiating either do perhaps
6
turns around a small 1" tube to make a balun at the feedpoint or alter the
length of the feeder slightly, if theVSWR alters when you change the
length
of the feeder then the feeder is radiating.
My two pennys worth, should help you get very close to the figures you
need
without the use of a GDO or an antenna analyser.
regards
Gus
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------------------------------
Message: 3
Date: Mon, 22 Sep 2008 10:47:33 -0700 (PDT)
From: Jim Jerzycke <kq6ea(AT)pacbell.net>
Subject: [amsat-bb] Re: Duplexer for Sats
To: amsat-bb(AT)amsat.org, David - KG4ZLB/M?ZLB <m0zlb(AT)btinternet.com>
Message-ID: <381876.58213.qm(AT)web80608.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
IIRC, Ken Brittain (sp?), father of the "Cheap Yagi", had a mention of
this in
his CQ VHF column. It was noted that the original design of the Arrow
apparently used a formula for insulated elements on the UHF side. This
resulted in the elements being about 1/2" too short.
I don't have that issue of CQ VHF with me, but it was published about 2
years
ago.
Jim KQ6EA
--- On Mon, 9/22/08, David - KG4ZLB/M?ZLB <m0zlb(AT)btinternet.com> wrote:
> From: David - KG4ZLB/M?ZLB <m0zlb(AT)btinternet.com>
> Subject: [amsat-bb] Re: Duplexer for Sats
> To: amsat-bb(AT)amsat.org
> Date: Monday, September 22, 2008, 9:31 AM
> A closer look at that document reveals that it was written
> in September
> 2006 and towards the end of it mention is made of the
> possibility of a
> second article about tweaking the standard Arrow for more
> gain - does
> anyone know if that article has been written/published or,
> for that
> matter, does anyone have any links to sites that describe
> Arrow
> modifications?
>
> Thanks
>
> David
> KG4ZLB
>
>
> Pughkeithd(AT)cs.com wrote:
> > In a message dated 9/22/2008 10:41:01 AM Central
> Daylight Time,
> > satkins(AT)inetdesign.org writes:
> >
> > Stephen,
> >
> > Check this out:
> http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf
> >
> > A duplexer is built as part of the antenna
> combination, but could be done
> > separately if necessary. Any 50 ohm coax and
> connectors could be used. This one
> > does feature inductors wound on a pencil.
> >
> > 73 - Keith, W5IU
> >
> > _______________________________________________
> > Sent via AMSAT-BB(AT)amsat.org. Opinions expressed are
> those of the author.
> > Not an AMSAT-NA member? Join now to support the
> amateur satellite program!
> > Subscription settings:
> http://amsat.org/mailman/listinfo/amsat-bb
> >
> >
>
> --
>
> *David*
>
> *KG4ZLB/M?ZLB*
>
> *www.kg4zlb.com <http://www.kg4zlb.com/>*
>
> *www.m?zlb.com <http://www.m0zlb.com/>*
>
>
>
> _______________________________________________
> Sent via AMSAT-BB(AT)amsat.org. Opinions expressed are those
> of the author.
> Not an AMSAT-NA member? Join now to support the amateur
> satellite program!
> Subscription settings:
> http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 4
Date: Mon, 22 Sep 2008 11:34:54 -0700 (PDT)
From: Stuart Underwood <w8stu(AT)att.net>
Subject: [amsat-bb] Re: FOR SALE ICOM IC-W32A
To: AMSAT-BB(AT)amsat.org
Message-ID: <233656.60546.qm(AT)web83809.mail.sp1.yahoo.com>
Content-Type: text/plain; charset=us-ascii
The W32A has been sold. Thanks to all that had interests. 73, Stuart
W8STU
I
have for sale a mint W32A.. It looks like it just came from the store.
That's how nice of shape it is in. This is a 2m/70cm HT. Comes with
radio, stock antenna, wal-wart, manual, HT case, and box. Pix on request.
I
am asking
$225.00 shipped. Paypal or postal money order. If interested please
call 440-639-9547 anytime after 3:00 PM EST or email w8stu(AT)arrl.net
Thanks in advance. 73, Stuart W8STU
_______________________________________________
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------------------------------
_______________________________________________
Sent via amsat-bb(AT)amsat.org. Opinions expressed are those of the
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Not an AMSAT member? Join now to support the amateur satellite program!
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End of AMSAT-BB Digest, Vol 3, Issue 479
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