Re: (OT) EFHW Vertical Antenna (Mike Morrow)

[k6mgo]

Stan and group, I found this post and referenced video very interesting. However I am bothered by several things.

First, a multi-band antenna cannot be a “end-fed half wave” on all bands. only on one band, as far as I know.

I’ve read many articles about “end-fed half wave” antennas over the years, and they have always been single band antennas with special matching circuits to tune them, and most have agreed that when they are a half wave on the frequency used, a counterpoise or radial is not required.

Which leads me to question the statement that a counterpoise or radial other than maybe a one meter or less one is required for this antenna. A 30’ antenna will only be a half wave near 20 meters, what happens on the rest of the bands? I know that sometimes using 5 watts or less, you might not notice a hot chassis or RF floating around, but, what is going to happen when you load this antenna with 100 watts?

I would appreciate hearing from others and what they think about the questions I have raised.

73, Bill, k6mgo
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[stan levandowski]

Bill - and group!

I sure wish I had the brains and experience to answer these questions
but I don't.  My expertise lies in other fields.  When they named us
"amateurs" they must have meant me ;).

Hopefully, other listers with deeper technical knowledge will comment.
I can only address my actual experiences.

  I can tell you is that this antenna WORKS GREAT if the measure of
*success* is a practical one -- how many QSOs can I make, can I hold a
QSO for more than the usual (unfortunately) 30 seconds it takes to get a
"599 and a TU",  and are my rig's finals happy.  Most of all, can I add
new countries to my list?

What my video shows is an end-fed (i.e. awful high impedance!) vertical
piece of wire that uses its coax feedline's shield for the small current
return at this impedance (as I *think* I understand it).  Above this
halfwave, it works better than below.  So yes, it most certainly is
*only* a halfwave antenna for 20 meters.  But I've worked DX with it on
30 and 40 meters also.   On 20, 17, 15, 12, and 10 it's super -
practically speaking.

Bill, my station at home is grounded to a *real* cold water pipe; I
don't have any RF floating around at home.  Touching my rig produces
none of the usual indications of  floating RF.  When I brought it to
Tony's house for the video, it was not grounded.  Still didn't exhibit
any bad habits.

I sure didn't mean to cause any controversy and I never intended to
suggest that *my* antenna is something special - rather, it is an
effective and far less costly alternative to the many commercial
"portable" antennas that so many hams turn to when they decide to try
away-from-home operating or, like me, they face rather severe antenna
restrictions.

I don't mean to impugn the many commercial products out there.  I happen
to own an HFp vertical and it's a good portable antenna that fits in an
18" nylon bag.  If I'm going somewhere on an airplane, that's what I'd
pack!  But if I want to operate closer to home - or, in my case - I want
an alternative to the 44' non-resonant doublet in my attic which is
oriented East-West, I can just push this vertical solution up in about
30 seconds and have fabulous success with it.

73 to all and to all a good night (hey, Christmas is around the corner
;)

Stan WB2LQF




On Sun, Nov 13, 2011 at 3:47 PM, Bill Ross wrote:

> Stan and group, I found this post and referenced video very
> interesting. However I am bothered by several things.
>
> First, a multi-band antenna cannot be a “end-fed half wave” on all
> bands. only on one band, as far as I know.
> I’ve read many articles about “end-fed half wave” antennas over the
> years, and they have always been single band antennas with special
> matching circuits to tune them, and most have agreed that when they
> are a half wave on the frequency used, a counterpoise or radial is not
> required.
> Which leads me to question the statement that a counterpoise or radial
> other than maybe a one meter or less one is required for this antenna.
> A 30’ antenna will only be a half wave near 20 meters, what happens on
> the rest of the bands? I know that sometimes using 5 watts or less,
> you might not notice a hot chassis or RF floating around, but, what is
> going to happen when you load this antenna with 100 watts?
>
> I would appreciate hearing from others and what they think about the
> questions I have raised.
>
> 73, Bill, k6mgo
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Brian Hunt]

I've been using a EFHWA vertical for a couple years now as a portable
antenna for 20, 30 and 40 meters.  It is 33 ft tall and supported by the
MFJ fiberglass pole.  It uses a small, tapped inductor located about 6
feet from each end to provide electrical half wave length on 30 and 40
meters.  The coils are shorted for 20 meters.  The only downside is you
have to pull the antenna down to change bands.  The matching network is
a tuned tank using a toroid wound coil and air variable.  The tank
circuit is matched to 50 ohm coax using a secondary winding with several
taps.  Full credit goes to N0LX for the design and construction details
( http://www.n0lx.com/efhwa.html ).

I usually use it with a short (10 ft) counterpoise wire and about 10-15
ft of coax to the rig. I suppose a bead style choke balun could be used
on the coax but I've never noticed problems with RF at the tranceiver  I
typically run 5 - 15 watts into the antenna.

YMMV

Brian
K0DTJ
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Nick Kennedy]

The EFHW looks pretty similar in terms of matching on the full wave
frequency (EFFW?) too.  That is, it's purely resistive and a couple
thousand ohms.  Actually a little lower on the higher band but not
much.  I use the same matcher for both bands.  So it's a good dual band
antenna.

My field QRP efforts the past few years have been on 40 and 20 meters.  
I use a single 66 foot long EFHW on both 40 and 20.  It works quite
well.  Also, my radiator is #22 or maybe #24 AWG Teflon insulated wire.

73-

Nick, WA5BDU


"
First, a multi-band antenna cannot be a “end-fed half wave” on all
bands. only on one band, as far as I know. I’ve read many articles about
“end-fed half wave” antennas over the years, and they have always been
single band antennas with special matching circuits to tune them, and
most have agreed that when they are a half wave on the frequency used, a
counterpoise or radial is not required.
"

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html