I recently posted regarding an antenna that Roy, W7EL designed back in
the 80's for backpacking (FD Special: directional array). I was a
little disappointed at no response but such is life.

Any thoughts as to whether this is a good approach to a home QTH antenna?

I was considering reconfiguring it for 17 meters and trying EZNEC for
the first time (if I can get the program to work on my new MacBook).

The antenna (20M version) consists of two elements separated by about 8
feet and the ends connected to a PVC pipe for support on each end
---[======]---

The antenna is 300 ohm twin lead and the feedpoint is in the center with
a 1/2 twist phasing line to the other element. 330 pF caps are used at
the feedpoint for matching.

I asked whether it might not be too difficult to reverse directionality.
(there's an article in QEX about that, in general, this month).

Any thoughts are appreciated.

2nd (OT) comment:
Compared to monitoring HF ham bands back in the 70's, is it true that
more QSOs are in nets now than individual QSOs?

I am very aware of the aging of hams (myself included)...many
conversations concerning healthcare interventions.

My impression is that the HF ham bands are LESS crowded than previously
(and this seems to conflict with what I am reading in ARRL, etc.)

thanks,

John
AB8O

Sorry, I missed the first posting.

It's a simple matter to reverse the directionality. Self-extracting ZIP
file http://eznec.com/misc/fdsp~.exe contains a program for designing
the antenna and a text file FDSP.txt with extensive notes including
information on how to reverse it. (The original article is at
http://eznec.com/Amateur/Articles/Field_Day_Special.pdf. See the added
notes at the end.)

It's a difficult antenna to model with EZNEC, because there's no direct
way to account for the effect of the dielectric material between
conductors in the twinlead, and this has a significant effect on
performance. The best approach is to use the design program (which does
account for the dielectric) to tell you what the current ratio is, then
model a simple, unfolded 2 element array with that ratio. The example
file FDSP.ez which comes with EZNEC can easily be modified to suit the
purpose. See the accompanying Antenna Notes file for more information.

Roy Lewallen, W7EL

jawod wrote:
I recently posted regarding an antenna that Roy, W7EL designed back in
the 80's for backpacking (FD Special: directional array). I was a
little disappointed at no response but such is life.

Any thoughts as to whether this is a good approach to a home QTH antenna?

I was considering reconfiguring it for 17 meters and trying EZNEC for
the first time (if I can get the program to work on my new MacBook).

The antenna (20M version) consists of two elements separated by about 8
feet and the ends connected to a PVC pipe for support on each end
---[======]---

The antenna is 300 ohm twin lead and the feedpoint is in the center with
a 1/2 twist phasing line to the other element. 330 pF caps are used at
the feedpoint for matching.

I asked whether it might not be too difficult to reverse directionality.
(there's an article in QEX about that, in general, this month).

Any thoughts are appreciated.

2nd (OT) comment:
. . .

Roy Lewallen wrote:
Sorry, I missed the first posting.

It's a simple matter to reverse the directionality. Self-extracting ZIP
file http://eznec.com/misc/fdsp~.exe contains a program for designing
the antenna and a text file FDSP.txt with extensive notes including
information on how to reverse it. (The original article is at
http://eznec.com/Amateur/Articles/Field_Day_Special.pdf. See the added
notes at the end.)

It's a difficult antenna to model with EZNEC, because there's no direct
way to account for the effect of the dielectric material between
conductors in the twinlead, and this has a significant effect on
performance. The best approach is to use the design program (which does
account for the dielectric) to tell you what the current ratio is, then
model a simple, unfolded 2 element array with that ratio. The example
file FDSP.ez which comes with EZNEC can easily be modified to suit the
purpose. See the accompanying Antenna Notes file for more information.

Roy Lewallen, W7EL


Roy, Thanks for the response. Soounds like I might have bit off more
than I can chew...but I may still try it...installation, at least, seems
a fairly easy project in Ohio winter.

John
AB8O

2nd (OT) comment:
Compared to monitoring HF ham bands back in the 70's, is it true that
more QSOs are in nets now than individual QSOs?

I am very aware of the aging of hams (myself included)...many
conversations concerning healthcare interventions.

My impression is that the HF ham bands are LESS crowded than previously
(and this seems to conflict with what I am reading in ARRL, etc.)

thanks,

John
AB8O
I have felt there is less QRM now days too. When I consider my own
circumstances, I never had the Technical abilities I have now. I think
my TenTec Jupiter with its accurate tuning and variable bandwidth
makes a big difference. I have noted that most QSO's take place on 1
mhz increments, which results in informal "channelizing" of the bands.
I am usually exactly on the other fellows frequency. While there are
probably more high power stations than ever, the rigs are cleaner in
general. I would be embarrassed to key up some of the unstable HB rigs
of the past. I think a higher percentage of the Ham population is
satisfied with a decent antenna and a clean 100 watt rig. Rigs that
enforce 50 ohm transmission lines have reduced interference too.

We are making better use of the allocated Spectrum.
John Ferrell W8CCW

John Ferrell wrote:
I have noted that most QSO's take place on 1
mhz increments, which results in informal "channelizing" of the bands.

Wow, I've been missing most QSO's. I'll have to
listen to 4, 7, 14, 21, and 28 mhz from now on. :-)
--
73, Cecil http://www.w5dxp.com

jawod wrote:

Roy, Thanks for the response. Soounds like I might have bit off more
than I can chew...but I may still try it...installation, at least, seems
a fairly easy project in Ohio winter.

It's really not hard to design, build, or set up. I used one at Field
Day this year as I have for the past 20 or so(*), and I had ones for 20
and 15 at home for quite a few years. One Field Day many years ago when
the kids were little and we "car camped" with friends, we put FD Special
antennas for 40, 20, and 15 up about 90 feet with a slingshot. Were the
top of our class that year. Quite a few have been built for various
bands and reports I've gotten is that they work as designed. Have fun!

(*) For a non-rotatable Field Day antenna from this location, the
pattern is just about ideal. It's wide enough to cover most of the U.S.
and without any significant power being wasted to the rear. I use only
one feedline on Field Day since there's no real need to switch the
direction.

Roy Lewallen, W7EL

On Wed, 01 Nov 2006 16:45:22 GMT, Cecil Moore
wrote:

John Ferrell wrote:
I have noted that most QSO's take place on 1
mhz increments, which results in informal "channelizing" of the bands.

Wow, I've been missing most QSO's. I'll have to
listen to 4, 7, 14, 21, and 28 mhz from now on. :-)
Oooops!
John Ferrell W8CCW