Antennas for use with Elecraft T1 ATU

[thomaskd]

I have an Elecraft T1  ATU and am looking for some simple
antenna ideas for using it with my QRP rigs including my
Wilderness Radio Sierra and SWL-20.  I am new to this outdoor
portable QRP operations...so I apologize if the questions seem
very basic.

I would like a setup that uses the T1 and is easy to deploy at a
park or when camping.  I have been doing a lot of reading on
the W3EDP antenna and think I will start with that.  Is this a
good place to start?

It seems like a lot of people somehow manage to cut the right
length of wire and shoot it over a tree and make contacts.  
Then there are other articles that talk about cutting the wires to
exact lenghts for performance.  Then there is another article
explaining that there is no magic in the length defined by the
previous article.

Any and all advice  on where to start would be helpful.  I have
a lot of band modules in the Sierra and would like an antenna
that lets me move around a bit.

Thanks in advance....

73 de Keith KB3ILS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stuart Rohre]

Keith, the absolute all around easy, and works every time, antenna is the
simple balanced dipole; a half wave long for the band in use.  You can use a
tuner with it and ladder line or TV twin lead feeder on higher bands.

The other simple portable antenna is the loaded ground plane.  You can do
20, thru 10m with a simple coil in the base of a vertical about 9 feet tall.
You can use simple, four, zip cord radials with it.  One such commercial
version of this is called The Minuteman antenna and is on the web.

Off center feeds can work, but then in some earth conditions you may have RF
on the rig chassis problems, and they may not work well.  They have the
disadvantage of bringing the high current antenna feedpoint right to the
radio, increasing the chance for lossy coupling to nearby conductors.

-Stuart
K5KVH


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[thomaskd]

Stuart,

Thanks for the quick response.  For a field dipole I could use
that in an inverted V format I assume?  I did purchase a
collapsable pole to try some of those out.  If I used ladder line
or twinlead....would I need a balun in-line before connecting to
the T1?

If I understood you correctly, I could cut the dipole for 40M and
then use the T1 to use it on other bands.  For my base setup I
use a dipole setup and it works well on multiple bands....I am
just not real clear on how to make this work on a portable
setup with the T1 ATU.

Is there any special twinlead or ladderline I should stock for
these projects?  I hope to try a bunch of antenna designs for
different locations and learn from them...so I may as well stock
some wire.

I think a recent QRP Quaterly that had a plan for a portable
vertical...I will check it out.

Thanks again for all the advice.

73 de Keith KB3ILS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Craig Smith]

<>For a field dipole I could use
<> that in an inverted V format I assume?  I did purchase a
<> collapsable pole to try some of those out.  If I used ladder line
<> or twinlead....would I need a balun in-line before connecting to
<> the T1?  
<> If I understood you correctly, I could cut the dipole for 40M and
<> then use the T1 to use it on other bands.  


You're on the right track Keith.  If 40 is the lowest frequency you normally
will use, then I would recommend you make your doublet 44 ft long (22 ft
each side) and feed it with any twinlead or ladder line.  The exact
impedance of the feedline isn't important.  The inverted V configuration
will work well and is very convenient with a single pole for supporting the
center.  Put one of the Elecraft 4:1 baluns at the T1 output and connect the
feedline to it and you will easily be able to tune all bands from 40 to 10.
You really don't want a resonant full size 40 meter dipole as it will be
difficult/impossible to tune on 20.  I think you will enjoy this setup.

           73
                     ... Craig   AC0DS


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[thomaskd]

Craig,

Thanks for the info.  I checked out the Elecraft baluns you
mention and will order one up.  This sounds like a reasonable
size setup for the times when I can get up a center pole to
support the antenna.  Is there a preferred height for the apex
or do I just go "as high as I can"?

I do have the 80M band module for the Sierra.  Is it possible to
make the doublet long enough to cover 80M and down?

73 de Keith KB3ILS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Kieth,

A dipole cut for 40 meters will provide a high feedpoint impedance on 20 -
and the L network used in the Elecraft tuners do not do high impedances very
well.

Of course, all that does depend on your feedline length as well as the
flattop length - the feedline will act as an impedance transformer when it
has SWR on the feedline, so unless you can state the length and impedance
and velocity factor of your feedline, we cannot answer your question with
any degree of certainty.

I use an antenna cut at 22 feet each side of center with a 25 foot feedline
for portable use, and it works FB on all bands except that it is marginal on
30 meters - adding an additional 10 feet of feedline allows it to tune 30
meters just fine with the Elecraft L network tuners.

I deploy my portable antenna as a horizontal dipole, or and inverted VEE, or
as a vertical with a single radial, whichever is convenient for the location
I have at the moment - I do carry a 32 foot collapsible mast to deploy the
antenna if I have no other suitable supports.

73,
Don W3FPR

> -----Original Message-----
>
> Thanks for the quick response.  For a field dipole I could use
> that in an inverted V format I assume?  I did purchase a
> collapsable pole to try some of those out.  If I used ladder line
> or twinlead....would I need a balun in-line before connecting to
> the T1?
>
> If I understood you correctly, I could cut the dipole for 40M and
> then use the T1 to use it on other bands.  For my base setup I
> use a dipole setup and it works well on multiple bands....I am
> just not real clear on how to make this work on a portable
> setup with the T1 ATU.
>
> Is there any special twinlead or ladderline I should stock for
> these projects?  I hope to try a bunch of antenna designs for
> different locations and learn from them...so I may as well stock
> some wire.
>
> I think a recent QRP Quaterly that had a plan for a portable
> vertical...I will check it out.
>
> Thanks again for all the advice.
>
> 73 de Keith KB3ILS
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Karl Larsen]

Don Wilhelm wrote:
> Kieth,
>
> A dipole cut for 40 meters will provide a high feedpoint impedance on 20 -
> and the L network used in the Elecraft tuners do not do high impedances very
> well.
>  
    I find the T1 does very well with a very high impedance. I end feed
1/2 wave wire connected right to the T1 with a counterpoise and it
matches right up! I ran a test and the T1 can match a 4700 ohm resistor.
So it's not bad with high resistance.

73 Karl

> Of course, all that does depend on your feedline length as well as the
> flattop length - the feedline will act as an impedance transformer when it
> has SWR on the feedline, so unless you can state the length and impedance
> and velocity factor of your feedline, we cannot answer your question with
> any degree of certainty.
>
> I use an antenna cut at 22 feet each side of center with a 25 foot feedline
> for portable use, and it works FB on all bands except that it is marginal on
> 30 meters - adding an additional 10 feet of feedline allows it to tune 30
> meters just fine with the Elecraft L network tuners.
>
> I deploy my portable antenna as a horizontal dipole, or and inverted VEE, or
> as a vertical with a single radial, whichever is convenient for the location
> I have at the moment - I do carry a 32 foot collapsible mast to deploy the
> antenna if I have no other suitable supports.
>
> 73,
> Don W3FPR
>
>
>  
>> -----Original Message-----
>>
>> Thanks for the quick response.  For a field dipole I could use
>> that in an inverted V format I assume?  I did purchase a
>> collapsable pole to try some of those out.  If I used ladder line
>> or twinlead....would I need a balun in-line before connecting to
>> the T1?
>>
>> If I understood you correctly, I could cut the dipole for 40M and
>> then use the T1 to use it on other bands.  For my base setup I
>> use a dipole setup and it works well on multiple bands....I am
>> just not real clear on how to make this work on a portable
>> setup with the T1 ATU.
>>
>> Is there any special twinlead or ladderline I should stock for
>> these projects?  I hope to try a bunch of antenna designs for
>> different locations and learn from them...so I may as well stock
>> some wire.
>>
>> I think a recent QRP Quaterly that had a plan for a portable
>> vertical...I will check it out.
>>
>> Thanks again for all the advice.
>>
>> 73 de Keith KB3ILS
>>
>>    
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>  

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[thomaskd]

Don,

Right now my feedline length is 0.  I have not built the antenna
yet.  I work about 20 mins from HRO and hope to swing over
there at lunch.  I have seen ladder line there before.

It sounds like the 22 feet per side is a common length that
works for people.  I will start with that. It also sounds like I
should test different feedline lengths as well to get the best
setup.   I also like the idea that was posted about using
Anderson Power Pole connecters to extend the dipole for good
80M coverage.  I have those lying around and will see about
giving that a try.

I have a bunch of wire ready to cut to various lengths to try
this stuff out.  The goal is to get a couple of antennas built so I
can operate outside and hone the CW that I have been
practicing.  After that...I can move into experimentation mode.

With your 25 foot feedline, are you using open ladder line or
some twinlead from Radio Shack etc?

Thanks for all the advice.  I am learning a lot.

73 de Keith KB3ILS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Ron D'Eau Claire-2]

Keith, KB3ILS wrote:
It sounds like the 22 feet per side is a common length that
works for people.  I will start with that. It also sounds like I
should test different feedline lengths as well to get the best
setup.  

------------------------------------------

Another approach many use to get around an out-of-range impedance on some
bands is to put an Elecraft BL2 balun at the rig end of the feeder and
switch it between 1:1 and 4:1 impedance ratios as needed. That has the same
effect as changing the length of the feedline.

I've used that antenna with excellent results on 40-10 meters. It was
between 25 and 30 above the ground. At that height it's a FB short-skip
antenna (NVIS) on 40 that gave me excellent signals out to 1,000 miles or so
with the occasional contact well beyond that when cdx were just right. On 20
meters, where it was almost 1/2 wave up (the optimum height for a half wave
horizontal antenna), and above I "worked the world" without hesitation
whenever the bands were open/

44 feet (22 each side of the feed point) is a good compromise length for a
doublet 7MHz and above. You don't start to see significant loss of radiated
signal until the radiator gets shorter than 1/4 wavelength, or about 33 feet
on 40 meters, as long as you "make up" the missing radiator length in the
feedline (keep in mind that the feeder has two  wires, so 15 feet of feeder
equals 30 feet of radiator).

So 22 feet gets you a fairly short doublet for easier installation that is
still virtually as good as a full half wave on the lowest band, and is as
good or better than a dipole on the higher frequencies.

I think that length became popular, in part, due to the work by Cebik in an
article he wrote about his "ideal" multiband dipole (see
http://www.cebik.com/radio.html). L.B. Cebik's (W4RNL) web site is a
treasure trove of excellent data and observations about antennas for anyone
tinkering with them! Cebik observed that is the ideal length that provides
the must useful radiation pattern up through 10 meters. Longer antennas
start breaking up their pattern in ways that aren't always helpful on the
higher frequencies where they are  well over one wavelength long.

Ron AC7AC

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Kieth,

This is a portable field antenna for me, and I have made the feedline from a
pair of twisted #22 teflon insulated wires.  Some years back, someone on
QRP-L did some tests on various feedlines, and this turned out to have good
loss characteristics, and it is flexible and lightweight which are two major
advantages for my use.  It rolls up nicely and the teflon insulation helps
keep it from tangling and snarling on other objects.  YMMV.  Jim N2GO is my
source of the teflon wire, he posts occasionally on QRP-L.

If I were using either a 44 or 88 foot flatop as a permanent antenna, I
would do it differently.  I would use #14 wire for the radiating section and
well positioned 450 ohm ladder line (or homebrew parallel line spaced about
4 inches apart) for the feedline.  The advantage of the 44 foot antenna is
that you know that the radiation is broadside to the antenna and without
side lobes for operation on 40 through 10 meters, and the 88 foot length is
similar for 80 through 20 meters.  Yes, it is only 2/3 of a half wave long
on the lowest band, and is not as efficient there, but this is a multiband
antenna, and some compromises must be made for any antenna, particularly a
multiband one.  In my case, I have accepted compromises both for portable
usability and multi-band use, but 'it don't work too bad'!

The feedline length of 25 feet is just what is convenient for my situation.
The proper feedline length should always be 'long enough to reach from the
shack to the antenna'!  The feedline length will change the impedance seen
at the shack end, but if your tuner will match that impedance, the exact
value is unimportant.  If you want information on how this impedance
transformation works in laymen's terms, take a look at the Antenna,
Transmission lines, and Tuners article on my website
http://w3fpr.qrpradio.com - There really is no magic in antennas, it just
seems that way at times especially if you do not know some basic
principles - at least enough to be aware of the ridiculous claims made by
some.  The fact that someone worked DXCC in 2 months with a wet noodle does
not say anything about the real characteristics  of that antenna.

73,
Don W3FPR

> -----Original Message-----
>
> Right now my feedline length is 0.  I have not built the antenna
> yet.  I work about 20 mins from HRO and hope to swing over
> there at lunch.  I have seen ladder line there before.
>
> It sounds like the 22 feet per side is a common length that
> works for people.  I will start with that. It also sounds like I
> should test different feedline lengths as well to get the best
> setup.   I also like the idea that was posted about using
> Anderson Power Pole connecters to extend the dipole for good
> 80M coverage.  I have those lying around and will see about
> giving that a try.
>
> I have a bunch of wire ready to cut to various lengths to try
> this stuff out.  The goal is to get a couple of antennas built so I
> can operate outside and hone the CW that I have been
> practicing.  After that...I can move into experimentation mode.
>
> With your 25 foot feedline, are you using open ladder line or
> some twinlead from Radio Shack etc?
>
> Thanks for all the advice.  I am learning a lot.
>
> 73 de Keith KB3ILS
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Rick Dettinger-2]

>     I find the T1 does very well with a very high impedance. I end feed
> 1/2 wave wire connected right to the T1 with a counterpoise and it
> matches right up! I ran a test and the T1 can match a 4700 ohm resistor.
> So it's not bad with high resistance.
>
> 73 Karl
==========================================
I wonder if an end fed  half wave antenna is a high resistance if a
counterpoise is used.  This actually would look like a 3/4 wave (with a
quarter wave counterpoise) offset fed antenna with no feedline.  This would
be a resonant antenna with a few hundred ohms at the feedpoint.  Most of the
radiation should be from the half wave section so should be an efficient
antenna.
73
Rick Dettinger
K7MW

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Rick,

Like everything else "It all depends"...

In your particular case, it depends on how the elements are oriented - and
that includes the counterpoise.  It also depends on the proximity of ground
and other objects.  Is the counterpoise in the air, or is it laying on the
ground?

That is the stuff that antenna modeling is made of - but modeling has limits
if you do not feed it proper information, a wire isolated in space behaves
differently than one 20 feet off the ground.  Often it is easier to just put
it up and measure it - an electrical halfwavelength of feedline will repeat
the feedpoint impedance of the antenna, so yes, you can use your antenna
analyzer to measure it with the antenna in the air.

73,
Don W3FPR

> -----Original Message-----
> I wonder if an end fed  half wave antenna is a high resistance if a
> counterpoise is used.  This actually would look like a 3/4 wave (with a
> quarter wave counterpoise) offset fed antenna with no feedline.
> This would
> be a resonant antenna with a few hundred ohms at the feedpoint.
> Most of the
> radiation should be from the half wave section so should be an efficient
> antenna.
> 73
> Rick Dettinger
> K7MW
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[thomaskd]

Thanks to everyone who provided advice on my antenna
question.

My Elecraft balun kit showed up today and I am going to get it
built.  I will try out of some of the ideas from this message
thread and hopefully get some good outside operating in over
the next month.  I think I have everything I need.

If you hear an unsteady CW fist and a signal that sounds like
the antenna is waving around in the wind.....check to see if it is
me!  If the prosigns are messed up....then it is even more
likely that it is me.

73 de Keith KB3ILS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com