K3 Multi-Band antenna thoughts

[Mike Scott-7]

I am considering building a multi-band doublet fed with ladder line to the
window and then 10-12 feet of coax to the K3 from the window interface. I
would let the K3 ATU tune the beast. I have been playing with a coax
calculator and with low loss coax and 10:1 SWR the losses in the short run
of coax up to 30MHz are manageable to ½ dB. The ladder line can handle the
mismatch with small losses. I was thinking of putting a sleeve balun at the
window interface from the coax to ladder line. I could of course put two
different length doublets in parallel at the feed point if that would tame
problem bands. I don’t need this antenna to go to 50 MHz as I will have a
separate antenna for 6M. I don’t have antenna modeling software. I know I
will have pattern issues if I try to push a long antenna too high in
frequency. I am not thinking right now of pushing this antenna to 160M.

So now the questions:

1. Is there a magic doublet antenna length that will end up with less than
10:1 SWR on the most bands? I know Cebik likes 88 feet or 44 feet depending
on lowest operating band but I don’t know that he has solved my exact
problem for 10:1 SWR or less on all bands.
2. Is there a magic feed line length to make this all work?
3. Have any of you tried something similar to this with the K3 ATU? I have
read the reports of just tuning up any old antenna that you have and you get
it to work at some unknown efficiency. I have done this too.

I know it is time for me to bite the bullet and purchase some real antennal
modeling tools.


Mike Scott
AE6WA Tarzana, CA
K3/100 SN508


_______________________________________________
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

[Greg - AB7R]

Mike,

I recently put up a 240ft doublet fed with 600 ohm open wire feeder.  The
feedline is "about" 200 ft long.  It terminates in the Elecraft BL2 balun
set for 4:1 and it tunes all bands 160-6M on the K3.

73
Greg
AB7R



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Mike Scott
Sent: Tuesday, March 11, 2008 7:55 PM
To: [hidden email]
Subject: [Elecraft] K3 Multi-Band antenna thoughts


I am considering building a multi-band doublet fed with ladder line to the
window and then 10-12 feet of coax to the K3 from the window interface. I
would let the K3 ATU tune the beast. I have been playing with a coax
calculator and with low loss coax and 10:1 SWR the losses in the short run
of coax up to 30MHz are manageable to ½ dB. The ladder line can handle the
mismatch with small losses. I was thinking of putting a sleeve balun at the
window interface from the coax to ladder line. I could of course put two
different length doublets in parallel at the feed point if that would tame
problem bands. I don’t need this antenna to go to 50 MHz as I will have a
separate antenna for 6M. I don’t have antenna modeling software. I know I
will have pattern issues if I try to push a long antenna too high in
frequency. I am not thinking right now of pushing this antenna to 160M.

So now the questions:

1. Is there a magic doublet antenna length that will end up with less than
10:1 SWR on the most bands? I know Cebik likes 88 feet or 44 feet depending
on lowest operating band but I don’t know that he has solved my exact
problem for 10:1 SWR or less on all bands.
2. Is there a magic feed line length to make this all work?
3. Have any of you tried something similar to this with the K3 ATU? I have
read the reports of just tuning up any old antenna that you have and you get
it to work at some unknown efficiency. I have done this too.

I know it is time for me to bite the bullet and purchase some real antennal
modeling tools.


Mike Scott
AE6WA Tarzana, CA
K3/100 SN508


_______________________________________________
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

No virus found in this incoming message.
Checked by AVG.
Version: 7.5.518 / Virus Database: 269.21.7/1325 - Release Date: 3/11/2008
1:41 PM

No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.518 / Virus Database: 269.21.7/1325 - Release Date: 3/11/2008
1:41 PM

_______________________________________________
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

[Chuck - AE4CW]

Mike, I'm having very good results with a 136.5 foot OCF dipole (1/3-2/3) fed with 120 feet of 300 ohm ladder line to an Elecraft BL-2 balun and one foot of coax to the K3.  The SWR at the radio is less than 1.8 and as low as 1.2 across all of 80, 40, 20, 17, 12, 2/3 of 10 and even the first 1/4 of 6 meters.  I can send you the detail results measured with an Array Solutions AIM 4170 if you like.  This approach keeps the SWR on the ladder line very low (less than 3:1) on these bands and makes tuner loses very low as well.  Total loss out to the antenna is less than 1 dB.  Plus it works on all the other bands including 160 with SWR's within the range of the K3 tuner, though with greater loss.

The length of the Ladder line is definitely a factor and I found that modeling and theory don't always match reality.  In this case it turned out that 120 feet was close to ideal; 100 feet was OK but not as good.  I also found out that running the ladder line inside, though ceiling and walls, made almost no measurable difference and you avoid the higher loss of coax.

BTW, I did the modeling work on EZNEC and then used TLW to figure out transmission line and tuner losses.  And the good news is that the real world results were even better than the model!

[n6wg]

Hi Mike
I can address part of your concerns.
Here in my QRP contest station, I have a bunch of wire
antennas, because one alone just won't cut it.

My main antenna is a 40m dipole fed with 450 ohm
window line so I can tune it on other bands.  It works
80-40-30 and 20m.  Above 20m, it starts developing
lobes in directions I don't want, and nulls in directions
I do want.  For 15 and 10m I have nested bisquare antennas
supported by the same mast that supports the center of
the 40m dipole.

To make antenna matching easier for the TX, I have a
homebrew relay box that adds in various lengths of more
450 ohm window line to bring the feedpoint reactance
down to close to zero.  This gives the ATU a chance to
match easily and gives the best 2:1 swr bandwidth.  The
single band antennas are coax fed, but still switched
through the relay box.

In summary, for any serious operating, one antenna
won't really do the job.  I suggest you do the best you
can with the antenna you presently propose, and after
a period of using it, find out what directions you are
having trouble with.  Then consider what you can do
for a supplementary antenna at that time.

I truly recommend EZNEC as an antenna modeling program.
I won't pick up a tool or a piece of wire to do antenna
work untill I've checked out what I plan to do with EZNEC.
It has saved me an enormous amount of wasted time and
effort.

Good luck and 73
Bob N6WG

Wire antenna farm here:
40m dipole for 80-40-30-20m for E-W path
10m bisquare E-W
15m bisquare E-W
55 ft dipole for 40-30-20-15m for N-S path
20m half square for N-S path (also seems to work well on 17 and  15m)
55 ft top loaded vertical for 160m.  Also works well as a
    top loaded vertical half wave for 80m.

----- Original Message -----
From: "Mike Scott" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, March 11, 2008 6:54 PM
Subject: [Elecraft] K3 Multi-Band antenna thoughts


I am considering building a multi-band doublet fed with ladder line to
the
window and then 10-12 feet of coax to the K3 from the window
interface. I
would let the K3 ATU tune the beast. I have been playing with a coax
calculator and with low loss coax and 10:1 SWR the losses in the short
run
of coax up to 30MHz are manageable to ½ dB. The ladder line can handle
the
mismatch with small losses. I was thinking of putting a sleeve balun
at the
window interface from the coax to ladder line. I could of course put
two
different length doublets in parallel at the feed point if that would
tame
problem bands. I don't need this antenna to go to 50 MHz as I will
have a
separate antenna for 6M. I don't have antenna modeling software. I
know I
will have pattern issues if I try to push a long antenna too high in
frequency. I am not thinking right now of pushing this antenna to
160M.

So now the questions:

1. Is there a magic doublet antenna length that will end up with less
than
10:1 SWR on the most bands? I know Cebik likes 88 feet or 44 feet
depending
on lowest operating band but I don't know that he has solved my exact
problem for 10:1 SWR or less on all bands.
2. Is there a magic feed line length to make this all work?
3. Have any of you tried something similar to this with the K3 ATU? I
have
read the reports of just tuning up any old antenna that you have and
you get
it to work at some unknown efficiency. I have done this too.

I know it is time for me to bite the bullet and purchase some real
antennal
modeling tools.


Mike Scott
AE6WA Tarzana, CA
K3/100 SN508


_______________________________________________
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

[Vic K2VCO]

Robert Tellefsen wrote:

> To make antenna matching easier for the TX, I have a
> homebrew relay box that adds in various lengths of more
> 450 ohm window line to bring the feedpoint reactance
> down to close to zero.  This gives the ATU a chance to
> match easily and gives the best 2:1 swr bandwidth.  The
> single band antennas are coax fed, but still switched
> through the relay box.

I do something similar, although I use inductors and capacitors rather
than pieces of line. This is very important to make a balun connected
between the balanced line and the coax efficient. I conducted a series
of tests in which I measured the temperature rise in the balun -- a sure
indicator of losses -- when the mismatch was primarily resistive or
reactive. Reactance is poison for balun efficiency!

And yes, you need a balun to reduce noise pickup, line radiation, and
rf-in-the-shack.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
_______________________________________________
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

[n6wg]

Hi Vic
Yes, I didn't mention it, but there is a 1:1 balun
inside the switch box before the feedline exits on
its way to the rig.

After listening to K9YC at our NCCC meetings, I
think I need to increase the impedance of this 1:1
choke balun though.  It's a bit undersized from his
point of view :-)

73, Bob N6WG

----- Original Message -----
From: "Vic K2VCO" <[hidden email]>
To: "Robert Tellefsen" <[hidden email]>
Cc: <[hidden email]>; <[hidden email]>
Sent: Wednesday, March 12, 2008 9:59 AM
Subject: Re: [Elecraft] K3 Multi-Band antenna thoughts

> Robert Tellefsen wrote:
>
> > To make antenna matching easier for the TX, I have a
> > homebrew relay box that adds in various lengths of more
> > 450 ohm window line to bring the feedpoint reactance
> > down to close to zero.  This gives the ATU a chance to
> > match easily and gives the best 2:1 swr bandwidth.  The
> > single band antennas are coax fed, but still switched
> > through the relay box.
>
> I do something similar, although I use inductors and capacitors

rather
> than pieces of line. This is very important to make a balun
connected
> between the balanced line and the coax efficient. I conducted a
series
> of tests in which I measured the temperature rise in the balun -- a
sure
> indicator of losses -- when the mismatch was primarily resistive or
> reactive. Reactance is poison for balun efficiency!
>
> And yes, you need a balun to reduce noise pickup, line radiation,
and
> rf-in-the-shack.
> --
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco

_______________________________________________
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

[Vic K2VCO]

Robert Tellefsen wrote:

> After listening to K9YC at our NCCC meetings, I
> think I need to increase the impedance of this 1:1
> choke balun though.  It's a bit undersized from his
> point of view :-)

Mine is huge, consisting of 13 turns of RG-58/u passing through SIX
FT-240-61 cores. A high common-mode impedance is also important for
efficiency.

We should add that a 1:1 balun is usually indicated for this
application, not a 4:1. Although the ladder line may have a
characteristic impedance of 450 ohms, the actual impedance looking into
the line varies widely with the band, the line length, etc.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
_______________________________________________
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

[Bill Strong]

Mike,

I have been using the 130' Cobra Ultralite Senior Multiband doublet style antenna by < http://www.k1jek.com > for several years. I currently use it with my K2/100 and KAT100. The antenna comes with 100' of twinlead which I attach to a DX Engineering 10KW 4:1 balun (DXE-BAL-200-H11_C) at my window with a short run of RG 213/U coax to the K2/100 and KAT100 Autotuner. I tried using the Elecraft balun but it get very hot at 100W. The DX Engineering balun never gets even warm.

The KAT100 indicates SWR match of 1:1 on most frequencies 160-10m with a maximum of 1.3:1 to 1.5:1 toward a band edge or two. My antenna is only 25' above ground suspended from and strung through pine trees. I routinely operate at 50W  on all bands and have no trouble being heard.

I have also used this arrangement with approximately 30' of the twin lead inside the house where I brought it in through an soffit board and looped it across the rafters to a closet ceiling, then down to the floor and under the closet door across my study along a wall over a wood floor to my desk. I did all of this passing through only wood and sheetrock and trying to maintain a distance of at least a foot from any other wiring. I did not worry about proximity to nails. The twin lead attached to the DXE Balun sitting on my desk with a 24" piece of coax to the K2. This worked extremely well with the lowest SWR's across the bands. I just rolled up the twin lead and left it in the closet when I was not using the antenna. I also detached the twin lead at the point of entry at the soffit when not in use and just left it rolled up at the base of the tree.

My Ultralite survived the 130 mph winds of Katrina to a point. It was anchored at the center and ends to pine trees. It got a severe whipping. It was finally downed by a huge pine tree falling across it. It did not tear the antenna apart other than pulling loose at one of the end insulators. It still worked after I reattached the end connection. I cannot say enough good about this antenna. It is the K2 of radio antennas. You can put it up and literally forget about it. It is one tough customer.

[David Cutter]

Bill

DX Engineering stuff is very well made and I wonder if perhaps some of the
difference between theirs and the Elecraft BL2 is more a question of size.
I'm wondering if you could be getting the same amount of heat in each balun,
but the huge bulk of the metal-encased 10kW DXE product simply absorbs all
you can throw at it, whereas the little Elecraft unit is only 2.5% of that.

Your antenna sounds interesting.  I wonder what the swr is at the bottom of
the feeder on each band.

David
G3UNA


----- Original Message -----

> snip
>
> Mike,
>
> I have been using the 130' Cobra Ultralite Senior Multiband doublet style
> antenna by < http://www.k1jek.com > for several years. I currently use it
> with my K2/100 and KAT100. The antenna comes with 100' of twinlead which I
> attach to a DX Engineering 10KW 4:1 balun (DXE-BAL-200-H11_C) at my window
> with a short run of RG 213/U coax to the K2/100 and KAT100 Autotuner. I
> tried using the Elecraft balun but it get very hot at 100W. The DX
> Engineering balun never gets even warm.
>
> The KAT100 indicates SWR match of 1:1 on most frequencies 160-10m with a
> maximum of 1.3:1 to 1.5:1 toward a band edge or two. My antenna is only
> 25'
> above ground suspended from and strung through pine trees. I routinely
> operate at 50W  on all bands and have no trouble being heard.
>
> >
> -----
> Bill Strong
> WA5KPE
> Hattiesburg, MS
> K2/100  #4454
> KAT100

_______________________________________________
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

[Bill Strong]

David,

I am sure you are correct in your idea that just as much heat is produced in the DXE balun as in the Elecraft balun but the heat is easily absorbed by the huge DXE balun.

I do not have an analyzer to measure impedance at the base of the twin lead. All I can say is that the KAT 100 is able to provide very reasonable matches 160 thru 10. I have not used my Elecraft Balun lately but if memory serves correctly it did not provide as good matches at either 1:1 or 4:1 as the DXE does. Early on I tried shortening the feeder but ended up with the full 100' for best matching.

If you would like I will run a series of matches on different bands and post the SWR readings from the KAT100.

[David Cutter]

Bill

It is quite likely that the heating effect is different on each band and
some bands will prefer a longer feeder than others.  The swr that the
matching unit provides is easy to measure but only tells us what the
transmitter sees.  W8JI has a lot to say on the subject.

73

David
G3UNA

>
>
> I am sure you are correct in your idea that just as much heat is produced
> in
> the DXE balun as in the Elecraft balun but the heat is easily absorbed by
> the huge DXE balun.
>
> I do not have an analyzer to measure impedance at the base of the twin
> lead.
> All I can say is that the KAT 100 is able to provide very reasonable
> matches
> 160 thru 10. I have not used my Elecraft Balun lately but if memory serves
> correctly it did not provide as good matches at either 1:1 or 4:1 as the
> DXE
> does. Early on I tried shortening the feeder but ended up with the full
> 100'
> for best matching.
>
> If you would like I will run a series of matches on different bands and
> post
> the SWR readings from the KAT100.
>
>
> -----
> Bill Strong
> WA5KPE
> Hattiesburg, MS
> K2/100  #4454
> KAT100

_______________________________________________
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