Tuesday, June 19, 2012

An Untanglable Twinlead 20-Meter Dipole


The March 2010 Trail-Friendly Radio column in WorldRadio Online magazine features a 20-meter folded dipole that is great for backpacking. Click here to visit the WRO Web site. It's free.

The secret for this antenna's success is an easy-to-build L-C matching network, whose schematic is shown above, and pictures below. A center support was fashioned from one-quarter-inch clear plastic and insulated nuts and bolts.

A view of the antenna's configuration inside the garage at KI6SN during testing is shown at the bottom.

For enlarged views, click on the images.




Tuesday, November 22, 2011

Schematic of LED Absorptive SWR Bridge-Indicator, Circa 2000, Featured in the January 2012 WRO

Details on how to build a "cardboarded" -  as opposed to a "breadboarded" - version of this T-FR LED Absorptive SWR Bridge-Indicator appears in the January 2012 edition of WorldRadio Online magazine: http://www.WorldRadiomagazine.com

Saturday, May 14, 2011

Reader Feedback: 2-Meter 300-Ohm Twinlead J-Pole, January 2011 WRO

I was quite interested to read the article on the “Loose-Wire Double Radiator 300 ohm
Twinlead 2-meter J-Pole antenna” in the January issue of WRO.

From what I understand, this is a modification of a J-Pole, modeled by the late L.B. Cebik,
taking into account the unconnected “loose wire” opposite the normal ½ wave radiator.

This design is also based on what Cebik calls “a non-standard” J-Pole design, where the ½ wave element is made shorter than a “normal” ½ wavelength, and the ¼ wave matching section is made longer than a “normal” ¼ wavelength.

What concerned me, however, was that the build dimensions published for the J-pole construction, appear to be those taken from what Cebik calls his "...bare-wire proof of
principle model”.

Note especially this term “bare-wire”, which clearly could not apply to anything made
from 300-ohm plastic insulated twinlead. Cebik also repeats several times throughout
his text, his reference to his "...bare-wire proof of principle model”.

Cebik points out that there are many varieties and shapes of flat, insulated, twinlead,
making modeling with antenna design software like NEC-4 a challenge, so he states
that "Therefore, models of twinlead must begin with bare-wire versions, with the caution
that the dimensions that emerge may not be close to the dimensions demanded by
vinyl-covered twinlead."

In other words, Cebik does not expect his "...bare-wire proof of principle model” to be
built as-is, without substantially modifying the theoretical dimensions, to account for the
effect of both wire insulation and most importantly the velocity factor of the particular
twinlead used.

I still can’t quite believe that many hams could have built up J-Poles using these
dimensions, without finding performance issues. Also strangely, in all the positive
reports that WRO mentions, no one seems to have actually measured SWR! I keep
looking for some other rational explanation, but it still looks to be related to misinterpretation
of Cebik’s “bare-wire proof of principle model”.

In order confirm this to myself, I have built a J-Pole as close as possible to the
information provided in the WRO January 2011 issue. Although I could not obtain any of
the pictured semi-clear TV twinlead, (no longer available) I doubt that it would have
made any difference.

The Twinlead I used was Radio Shack # 15-1174, with a published velocity factor (Vf) of
0.733. (in my testing I measured the actual Vf on a sample as 0.77)

To sum up, my findings were that for the J-Pole sample I built from the published
dimensions, the swr performance is extremely poor. The SWR was high across the
band from 144 - 149 MHz (9.2 – 4.5) and was not resonant anywhere.

Frankly, I would not want to use this antenna on any radio of mine.
Details of my results are given in the table that follows the text.

You will see that I tried to modify some of the published dimensions by adjusting some
of them for Vf, and obtained at least some improvements over the original test results.
These “experiments” are highlighted in the table.

In the end, it proved a larger task than I was prepared to continue, to come up with a
final set of dimensions that would yield a resonant low-SWR design from Cebik’s model.
I have included the dimensions below only to illustrate what I had done.

For comparison purposes, I also measured using the same set-up, a “conventional”
twinlead J-Pole I made some years ago based up a design published in the 1994
September QST issue.

This J-Pole clearly outperforms the WRO J-Pole under discussion.
There are many references in the literature illustrating practical dimensions for similar
“conventional” or standard twin-lead J-Poles.

I have listed some below:

“The DBJ-2: A Portable VHF-UHF Roll-Up J-pole…”, QST March 2007
“More on the Ribbon J-Pole Antenna”, QST June 2003
“The DBJ-1: A VHF-UHF Dual Band J-Pole”, QST February 2003
“The Twin-lead J-Pole” by WB3GCK, 1998
“An Easy Dual Band VHF-UHF Antenna”, QST September 1994
“144-148 MHz PVC Water Pipe J-Pole antenna”, K5LN, 6/22/97
“The 300-ohm Ribbon J Antenna for 2 meters; A Critical Analysis”, April 1982


Don Dorward, VA3DDN

Thursday, October 21, 2010

KI6SN T-FR Single-Lever CW Paddle

November 2010's Trail-Friendly Radio, in Worldradio Online magazine by Richard Fisher, KI6SN, features a modified version of NB6M's renowned single-lever CW paddle you can build. It's fortified for rugged field operation. Click here to see the full article. Additional photographs and dimensions for the paddle's dual-sided PC board parts are shown below.

For an enlarged view, click on the images

Friday, May 21, 2010

'Where Am I Going to Operate?' - Frequencies

For an enlarged view, click on the image.

Darrell Swenson, KØAWB, of Omaha, Nebraska, put together this handy chart of HF and VHF frequencies regularly monitored by various amateur communities and organizations. It can be printed out and used as a handy "cheat sheet" for determining on what frequencies to operate when on trail-friendly radio expeditions.

Additions and corrections to the chart are welcome. Please write Trail-Friendly Radio columnist Richard Fisher, KI6SN, at KI6SN@aol.com.

Monday, April 12, 2010

KI6SN LM380 Audio Amplifier For the Field

KI6SN's Trail-Friendly Radio column in the May 2010 edition of WorldRadio Online magazine features an easy-to-build audio amplifier that's great for adding headphone punch in the field. Utilizing a 14-pin LM380 / NTE740A chip, the circuit requires only a small handful of parts.

Here are some photos of the KI6SN version of the amplifier:

For an enlarged view, click on the images.

Links to parts sources for the amplifier include: 

Dan's Small Parts and Kits

Digi-Key Corp.

Mouser  Electronics

Friday, March 19, 2010

Feedback On the KI6SN OM Antenna Mast

 This photo shows the bottom portion of N2EIK's PVC mast arrangement.

Here's the mid-portion of the mast at N2EIK.

 A look at the top portion of the mast at N2EIK.

Click here for a look at Euler’s Laws.

Click here to see more photographs of KCØBMF’s PVC antenna mast. Look on the left side, click on Field Day and then look at 2009.

Click here to view the January 2010 Trail-Friendly Radio column featuring the KI6SN OM Mast.

Tuesday, January 19, 2010

Diana Eng, KC2UHB: From the 'Runway' to the trail

Diana Eng, KC2UHB, a star of the hit Bravo reality series Project Runway, has the lead role in her own You Tube video: How To: Set Up An HF portable radio while hiking. The world-renowned fashion designer and author of Fashion Geek: Clothes Accessories Tech, enjoys trail-friendly radio as a way to get out of the concrete canyons of New York City and onto the hiking trails of New Jersey, Connecticut and beyond.

Featured in KI6SN's Trail-Friendly Radio column in the February 2010 edition of WorldRadio Online, 'UHB often goes on T-FR excursions with David Clausen, W2VV; and Tom Tumino, N2YTF. Here's a gallery of photographs from some of their outdoor adventures - which include sojourns to New Jersey, Connecticut, Turks and Caicos Islands and satellite operation from NYC.

ABOVE: KC2UHB in New York City, above, holds a hand-held antenna in preparation for making VHF/UHF contacts via a passing satellite.
BELOW: An engraved plate marks the summit of Mt. Carmel in Connecticut.

ABOVE: KC2UHB relaxes during a recent T-FR outing.
BELOW: KC2UHB and N2YTF ready their radio gear before hitting the trail.

ABOVE: At an indoor operating post, KC2UHB listen while she tunes.
BELOW: Operating VP5 from Turks and Caicos Islands in the Caribbean, 'UHB makes HF contacts near the beach.

BELOW: Diana Eng, KC2UHB, and Dave Clausen, W2VV, pose for a picture during a T-FR outing.


(Photography courtesy of Dave Clausen, W2VV)

Tuesday, December 15, 2009

The KI6SN 'Old Man' Mast - Bending all the rules

The January 2010 edition of WorldRadio Online's Trail-Friendly Radio column features the KI6SN "Old Man Mast," an easy-to-carry, lightweight mast that is particularly useful for field operation where antenna supports are few and far between - such as above the treeline on mountain-top excursions.

The antenna derives its name from the Old Man's crooked stature, due to the many PVC joints along its length. The antenna support may suffer from a case of scoliosis, but it's a trusty, solid performer that can get your skywires to where they might not otherwise go.

This illustration above shows the nuts-and-bolts of the "Old Man," even though it's made solely of PVC materials

Several PVC joints connect the short sections of PVC mast material:

The "Old Man" is guyed at two different heights to achieve strength and stability. Here's a shot of the upper guy:

The following three photographs show the method for determining the circumference of the circle that marks where your guying stakes will be placed:

The mast is put up in two phases. Pictured below is what the top of the first phase looks like. The upper portion of the antenna is added to the PVC joint coupling shown here (after the lower portion's guy lines are already staked in place):

For an enlarged view, click on the illustrations.

Saturday, November 14, 2009

WA3ZBJ takes field-based antennas to a new height

As featured in KI6SN's December '09 Trail-Friendly Radio column in WorldRadio Online magazine, Don McBride, WA3ZBJ, operated a newly-completed Hendricks QRP PFR-3, above, “from a great spot near a fire watch tower on a hilltop in Cook Forest State Park in Pennsylvania.” His favorite portable antenna is a jumper dipole “for 20-30-40 suspended in an inverted V configuration from one of the many trees in the area and fed with lightweight coax.”

With a set-up along the St. Johns River in DeLand FL, 'ZBJ used a Wilderness Radio Sierra transceiver portable with an inverted V antenna suspended from 33-foot pole (left).

'ZBJ says that putting an eye-hook into a used golf ball makes for a great launch vehicle when the goal is to get your antenna as high into a tree as possible. Tie lightweight nylon line through the eye and you've got a wonderful projectile for those out-of-reach branches. It's quick and inexpensive to make and lightweight and easy to carry into the field.


(For an enlarged view, click on the images)

Monday, October 19, 2009

A simple, useful tuner for the venerable EFHW

KI6SN's November 2009 Trail-Friendly Radio column in WorldRadio Online magazine focused on a useful, popular and easy-to-manage HF field antenna: the EFHW - or End Fed Half Wave, with a counterpoise.

Above, you'll see the schematic for a simple EFHW tuner for the popular 40- and 20-meter CW bands. Dan Tayloe, N7VE; Charlie Lofgren, W6JJZ; Bill Jones, KD7S; and David Bixler, WØCH; share design credit for the tuner and LED-based SWR bridge.

(For an enlarged view, click on the images.)

Saturday, September 12, 2009

High-flying with the Bottle Bag Antenna Launcher

The Trail-Friendly Radio column by KI6SN in the October 2009 edition of WorldRadio Online magazine features a simple antenna launching scheme known as the Bottle Bag. Accompanying photographs show the bag's configuration for both carrying and launching.

Click here to see a video on how to tie a bowline knot, which is useful in using this launching method.

Also, you may want to check out "In the Bag: Throwing Antenna Woes to the Wind" by John Kalotai, N1OLO, which was published in the Adventure Radio Society's ARS Sojourner online magazine in 2005. Click here for the link.

Click here for the latest edition of WorldRadio Online magazine. It's free.

(For an enlarged view, click on the images.)

Friday, August 21, 2009

W6JRY reflections on the PRC-64 'Spy Radio'

The September 2009 Trail-Friendly Radio column in WorldRadio Online magazine features a retrospective on the Vietnam-era PRC-64 "Spy Radio." Jerry Fuller, W6JRY, shared his insights on restoration of this renowned trail-friendly radio and his experiences using it on the air.

Click here to view a military paper dated April 1967 by Stanley D. Peirce of the U.S. Army War Laboratory at Aberdenn Proving Ground, Maryland, that chronicles the research and development of the PRC-64. (Please allow a few minutes for this PDF to download.)

For an UNCLASSIFIED assessment of this famed spy radio, click here.

Below is a photograph of W6JRY at the helm of his Forest Ranch, CA station.

Monday, July 20, 2009

The W5JH Baby Black Widow keyer paddle

The August 2009 edition of WorldRadio Online magazine's Trail-Friendly Radio column, by Richard Fisher, KI6SN, features Jerry Haigwood, W5JH's, new Baby Black Widow keyer paddle that is perfect for trail operations - especially when using the Elecraft KX1 or Hendricks QRP PFR3 transceivers.

Below is a photograph showing how the Baby Black Widow can easily be adapted for use with any transceiver by fashioning an eighth-inch stereo headphone jack (available from Radio Shack) as an attachment to your key line.

Also, there's a photograph showing how a piece of thread can be used as a tether when you're installing the paddle's tension spring during construction. Simply reel off a 10 to 12-inch piece of sewing thread and loop it through the center of the spring. If the spring "decides" to fly off into the wild blue yonder during construction, it'll only go as far as the tether allows. And, after you've successfully installed the spring, simply cut the thread or pull it away from the spring. Voila!

Click here to visit the W5JH Website.

(For enlarged views, click on each image.)