Balun

[Richard Soennichsen]

Hi All,

            I (a Ham to be) am planning to buy a K2 in the future.  I am
planning my antenna now and am going to borrow a radio in the mean time.  I
am planning on building a simple dipole that will stretch from my rooftop to
a neighbor's tree.  I would like it to be a total of 131' long but I will
have to see.  The antenna will be fed by 450 ohm ladder line.  Some
questions:

 

Does the ladder line connect directly to the K2?

 

Do I need a balun with this setup?

 

If I cannot squeeze in the full 131" is it better to make the antenna
shorter or can I run one end of the dipole around the edge of my (flat)
rooftop to get 131'.  In otherwords one end of the dipole would be straight
will the other would have a couple of doglegs.  This scenario is also
appealling as it would place the feedline out of view of my wife.  (Feng
Shui detractor)

 

Can I use pieces of plexiglass for insulators and dipole center assembly?

 

Thanks

 

Rich

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[Vic K2VCO]

Richard Soennichsen wrote:

> Does the ladder line connect directly to the K2?

No, the K2 has unbalanced output.  But see below.

> Do I need a balun with this setup?

You need some means of connecting the ladder line to the K2 without
unbalancing the feedline.  The best way to do this is with a true
balanced tuner.  There are several on the market, or you can find an old
Johnson Matchbox (made in the '50's or '60's, they are still around).
I'm assuming that you want to use your antenna on more than one band.  A
4-1 balun would work on 80 meters, but whether or not it would be
useful, useless, or a hinderance on other bands depends on the feedline
length.

Note that a balanced tuner, unbalanced tuner, a balun, or nothing at all
will 'work', allowing you to make QSOs.  There will be differences in
efficiency, noise pickup on reception, and possible RFI.

> If I cannot squeeze in the full 131" is it better to make the antenna
> shorter or can I run one end of the dipole around the edge of my (flat)
> rooftop to get 131'.  In otherwords one end of the dipole would be straight
> will the other would have a couple of doglegs.  This scenario is also
> appealling as it would place the feedline out of view of my wife.  (Feng
> Shui detractor)

If the legs are straight for about half their length, the doglegs would
be better.  In general, I prefer bending the antenna to shortening it.

> Can I use pieces of plexiglass for insulators and dipole center assembly?

Yes, plexiglas is a very good insulator.

--
73
Vic, K2VCO
Fresno, CA
http://www.qsl.net/k2vco
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[Steven Pituch]

Hi all,

OK, I think I have all the upgrade modes working on my K2 #402.  It was
a lot more work than I thought it would be; lots of changes.  The CW
filters seem significantly better than before.  And the SSB filter looks
quite flat.

However, I just installed the KDSP2, and based on the manual the auxbus
isn't communicating with the dsp unit.  I seem to be able to use the
default filters, but when I hit "display" I still get the voltage and
current readout.  Also I think I was supposed to get a clock setting
routine when I first powered up.

Everything seemed to go together OK, except the width of the socket for
the clock IC is significantly narrower than the IC pins.  I had to
actually bend the pins inwards in order to get them into the socket.
That's the first time that has happened.

I am studying the schematic now.  Any suggestions?

Also, what happens if I want to do a cal pll or something.  Don't I need
the freq counter probe plugged in to do that?  Would I need to remove
the DSP unit and then short out the connector where r18 and r19 are shown?

As good as the radio was before the mods, its gonna be a killer once I
get this dsp working.  I'm impressed.

Thanks,
Steve, W2MY
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[Stuart Rohre]

Rich,
You will need the Elecraft balun kit for the feeder at the rig before it
connects to K2 by a short coax jumper.

You can use any plastic that has no conductive material in it as insulators.
The one you mention is fine, (plexiglas).  You can also use PVC plumbing
fittings from Home Depot, or buy the grey conduit pvc and cut insulators out
of that.  In the beige PVC plumbing fittings are Tees for center insulator,
and nipples for end insulators.  Or just buy the grey conduit as it is more
resistant to sunlight, and cut to needed lengths.

You can dogleg the ends of your dipole, (doublet since it is non resonant,
131 ft.).  That would be symmetric and better than folding only one end.
You need to keep the center and feeder part in straight line for 60 per cent
of total length for most efficiency.  Do not shorten the doublet, in fact
usually an all band doublet is made of 135 feet of wire, center fed by
ladder line, and of course you need a tuner at the end of the line, after
your balun.

I think I covered all your points.   Use as much wire as you can, up to 135
feet, as straight as you can get mid part of it.   Plastic is fine for
insulators.
Darker plastic resists the sun more.  You will need a tuner for all bands
coverage.  You can fold, droop, bend the ends of a doublet to make it fit.

You could put up a PVC "flag pole" and run the ladder line inside it, and
hang the doublet as an inverted Vee from the top.  Use smaller wire, like
no. 16 for low visibility and use dark wire, flat black if possible. It will
tend to blend into sky background.
GL and 72,
Stuart
K5KVH

It might be better to let them hang down rather than be up close to roof
edge.

Some roofing has a foil backing or metal at edges.




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[KK7P]

> ... I just installed the KDSP2, and based on the manual the auxbus
> isn't communicating with the dsp unit.  I seem to be able to use the
> default filters, but when I hit "display" I still get the voltage and
> current readout.  Also I think I was supposed to get a clock setting
> routine when I first powered up.

Be sure the RTC mode is ON or you won't be able to communicate with the
DSP (initial Checkout, Page 18 of KDSP2 manual).

If the DSP chip itself is having a problem, there would be no audio.

Lyle KK7P

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[Stuart Rohre]

I guess one of the issues, are you ordering a K2 with its auto tuner?

In that case, my suggestions apply, to adding the Elecraft balun, and using
the internal K2 tuner for your antenna.  It is also true that a balanced
line tuner will work after the K2, and before your ladder line.

Since surplus Johnson Match Boxes do not match on all bands and are harder
to find in surplus; you might check out the new line of MFJ balanced tuners.
They have a double Tee network, and use large, well suited components.  They
go between the K2 and the ladder line, for manual tuning like a Match box
did.

I was impressed with them at Ham Com where they were on display.
In addition to a double network to balance the tuner, they float the tuner
input with a RF choke isolation, to insure you do not couple RF back to the
rig on outside of coax.

-Stuart
K5KVH



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[Vic K2VCO]

Stuart Rohre wrote:
> I guess one of the issues, are you ordering a K2 with its auto tuner?
>
> In that case, my suggestions apply, to adding the Elecraft balun, and using
> the internal K2 tuner for your antenna.  It is also true that a balanced
> line tuner will work after the K2, and before your ladder line.

A K2 with auto tuner followed by a balun will work well on some bands,
and poorly on others.  The balun's effectiveness and efficiency will
depend on the 'common mode impedance' it sees on various bands.  This
depends on the length of the antenna and feedline.  There will most
likely be combinations of frequency and dimensions in which the balun
will heat up and waste power, as well as combinations in which it will
not do its job, and power will be lost by radiation from the feedline
(with associate noise pickup and possible RFI).

Again, almost anything will 'work'.  The question is, How Well?

--
73
Vic, K2VCO
Fresno, CA
http://www.qsl.net/k2vco
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[Steven Pituch]

Aaaaaaaaaah, OK Lyle.   Stupid, stupid, stupid, stupid, stupid me.

I guess I should have read page 18.  I was so careful reading the manual
when I was building it, but I guess I got a bit lax after getting to the
  installation part.  Thanks for the good advice.  I am relieved that I
didn't screw up the building of it.

I lost the sidetone after changing the RTC setting but got it back after
several tries.

The DSP is incredible.  Especially after I studied the manual and
fiqured out some of the basic procedures, like knocking the noise
reduction in and out quickly on CW, changing the center frequency, etc.

Thanks a million,
Steve, W2MY


Lyle Johnson wrote:
> Be sure the RTC mode is ON or you won't be able to communicate with the
> DSP (initial Checkout, Page 18 of KDSP2 manual).
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[KK7P]

> The DSP is incredible.  Especially after I studied the manual and
> fiqured out some of the basic procedures, like knocking the noise
> reduction in and out quickly on CW, changing the center frequency, etc.

Keep in mind the front panel shortcut with the latest K2 firmware.
AFIL+REC will toggle the denoiser on and off without being in the DSP
menus, and AFIL+SPLIT will similarly toggle the automatic notch filter
on and off.

Enjoy the KDSP2!

73,

Lyle KK7P

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[Ron D'Eau Claire-2]

Since you aren't trying to make the antenna self-resonant, you will need to
have an antenna tuner, as others observed. The tuner will convert whatever
impedance the antenna presents at the end of the feedline to 50 ohms as
required by the K2. That impedance will vary depending upon the band, and a
KAT2 (for the QRP K2) or KAT100 for the K2/100 will do FB. I do NOT
recommend the MFJ "T-Match" tuners for this duty, and I especially do not
recommend using their built-in baluns.  

About the length, unless you are going to work 160 meters, any length over
66 feet will be FB. The difference in performance between a half-wave center
fed antenna and a 1/4 wave center fed antenna is virtually nil. Once you are
over 1/4 wave long, the most important thing is height, especially for
working DX on the lower bands.

I wouldn't invest one bit of energy getting an doublet like you are
contemplating any longer than 90 or 100 feet for 80-10 meter operation.
There's nothing to be gained by doing so.

The ideal antenna tuner for you is a balanced tuner. None of the Elecraft
tuners are inherently balanced, although they are starting to show up on the
market again as more and more hams go to the type of doublet you are putting
up in order to easily work all the HF bands. A balun will probably work
okay, but they become unpredictable when the SWR on the line is high, as it
will be in your antenna. Sometimes people actually get out better simply
hooking one side of the open wire feeder to the K2 case and the other to the
center pin on the output of the ATU. That produces a large degree of
imbalance in the feeders, so they'll radiate. That can actually be a help if
your feeders are out in the clear and pretty much vertical.

Nothing is as much "black magic" in his Hobby as antennas!

Ron AC7AC

 

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Stuart Rohre
Sent: Thursday, June 09, 2005 3:39 PM
To: Vic Rosenthal; Richard Soennichsen
Cc: [hidden email]
Subject: Re: [Elecraft] Balun


I guess one of the issues, are you ordering a K2 with its auto tuner?

In that case, my suggestions apply, to adding the Elecraft balun, and using
the internal K2 tuner for your antenna.  It is also true that a balanced
line tuner will work after the K2, and before your ladder line.

Since surplus Johnson Match Boxes do not match on all bands and are harder
to find in surplus; you might check out the new line of MFJ balanced tuners.
They have a double Tee network, and use large, well suited components.  They
go between the K2 and the ladder line, for manual tuning like a Match box
did.

I was impressed with them at Ham Com where they were on display. In addition
to a double network to balance the tuner, they float the tuner input with a
RF choke isolation, to insure you do not couple RF back to the rig on
outside of coax.

-Stuart
K5KVH



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[Geoffrey Mackenzie-Kennedy-2]

Rich,

I would like to second Ron's (AC7AC) comments about tuners. Personally I
would stay away from 'T networks' for use in antenna tuners, and use the old
fashioned link coupled form of balanced tuner. T networks can be mistuned to
provide a 50 ohm load for the transmitter, but not deliver much power to the
antenna, in other words become a fairly good dummy load. Quite a lot has
been written about this.

Although some commercial 'old fashioned' balanced tuners might run out of
steam, there are ways to cure this problem - without modifying the tuner. If
of interest to you, we could discuss this off list at a later date. The
other option is to build one!!

About the antenna, and assuming centre feed. As Ron has said, reducing the
length of the wire even down to a quarter wave has little effect on the
radiated signal at the frequency where the length is a quarter wave, less
than 0.75db down from a full size halfwave dipole at the same frequency. The
radiation resistance does decrease quite a lot, but is still manageable. The
important thing is to keep the antenna wire away from tree branches, roof
and other objects. The same applies to the feeder. If you feel happier with
the longer wire and bend the ends downwards, the radiation pattern on the
higher bands could be quite different from that of a straightforward flat
top depending on how much wire droops. This comes about because the drooping
ends at some frequencies become 'elements' of a broadside (or end fire)
beam, whose radiation adds to (or subtracts from) the radiation from the
horizontal wire. Murphy's law states that the high gain lobes will always
point in the wrong directions! Dog legging the wire will have some effect,
although not as much perhaps if gentle. Personally I would stick with a
straight doublet, hung clear of other objects.

Good luck,

73
Geoff
GM4ESD


----- Original Message -----
From: "Richard Soennichsen" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, June 09, 2005 9:30 PM
Subject: [Elecraft] Balun


> Hi All,
>
>             I (a Ham to be) am planning to buy a K2 in the future.  I am
> planning my antenna now and am going to borrow a radio in the mean time.

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[Mike Markowski]

Ron D'Eau Claire wrote on 06/09/05 21:57 ET:
> A balun will probably work
> okay, but they become unpredictable when the SWR on the line is high, as it
> will be in your antenna.

I use a classic Zepp and found this out first hand!  A 4:1 balun might
not give a true 4:1 change in that case or could show losses.  In the
other extreme, sometimes the impedance can go low to begin with on a
multiband wire and a 4:1 makes it too low to match.

> Sometimes people actually get out better simply
> hooking one side of the open wire feeder to the K2 case and the other to the
> center pin on the output of the ATU. That produces a large degree of
> imbalance in the feeders, so they'll radiate. That can actually be a help if
> your feeders are out in the clear and pretty much vertical.

If your feeders aren't out in the clear, a 1:1 balun like the w2du type
with ferrite beads does a much better job of suppressing common mode
currents in the shack.  Of course, you might lose the ability to tune
80m without the 4:1 and then have to play with feedline length.  I like
your line Ron:

> Nothing is as much "black magic" in his Hobby as antennas!

73,
Mike  AB3AP
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[N2TK]

Tried the shortcuts listed below. I just get a message - "not inst". Yet the
DSP works fine. Any thoughts? I have software versions 2.04P, 1.09
Tnx
N2TK, Tony



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Lyle Johnson
Sent: Thursday, June 09, 2005 8:32 PM
To: Steven Pituch
Cc: [hidden email]
Subject: Re: [Elecraft] KDSP2 problem

> The DSP is incredible.  Especially after I studied the manual and
> fiqured out some of the basic procedures, like knocking the noise
> reduction in and out quickly on CW, changing the center frequency, etc.

Keep in mind the front panel shortcut with the latest K2 firmware.
AFIL+REC will toggle the denoiser on and off without being in the DSP
menus, and AFIL+SPLIT will similarly toggle the automatic notch filter
on and off.

Enjoy the KDSP2!

73,

Lyle KK7P

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[KK7P]

Hello Tony!

> Tried the shortcuts listed below. I just get a message - "not inst". Yet the
> DSP works fine. Any thoughts? I have software versions 2.04P, 1.09

 > Keep in mind the front panel shortcut with the latest K2 firmware.
 > AFIL+REC will toggle the denoiser on and off without being in the DSP
 > menus, and AFIL+SPLIT will similarly toggle the automatic notch filter
 > on and off.

If you are in CW mode, the notch will not work and you will get "not
inst".  In RTTY mode, neither the notch nor the denoiser will work.  In
USB or LSB mode, both shortcuts ought to work.

Lyle KK7P

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[N2TK]

Hi Lyle,
I get the same message no matter whether in CW or SSB modes.
N2TK, Tony



-----Original Message-----
From: Lyle Johnson [mailto:[hidden email]]
Sent: Monday, June 13, 2005 1:50 PM
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] KDSP2 problem

Hello Tony!

> Tried the shortcuts listed below. I just get a message - "not inst". Yet
the
> DSP works fine. Any thoughts? I have software versions 2.04P, 1.09

 > Keep in mind the front panel shortcut with the latest K2 firmware.
 > AFIL+REC will toggle the denoiser on and off without being in the DSP
 > menus, and AFIL+SPLIT will similarly toggle the automatic notch filter
 > on and off.

If you are in CW mode, the notch will not work and you will get "not
inst".  In RTTY mode, neither the notch nor the denoiser will work.  In
USB or LSB mode, both shortcuts ought to work.

Lyle KK7P


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[KK7P]

Hello Tony!

> I get the same message no matter whether in CW or SSB modes.

Then I suspect you have older DSP firmware.  The current version, which
supports the front panel shortcuts, is "Ctl 3.10"  Please see the KDSP2
errata sheet on the Elecraft website in the Manuals section.

73,

Lyle KK7P

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