Ham Radio Help Desk

I am preparing for the Virginia QSO Party and want to add an alternative 20 meter solution for my 43 foot vertical plus get better 15 and 10 meter coverage; I have been working plenty of 15 meter contacts with the 43 foot vertical so I know that band is open. Plus you never know if the sunspots might give us some 10 meter fun too

So…

I have been eagerly absorbing all there is to know about the hex beam style of HF antennas.

If you are the least bit interested in building or buying your own hex beam a must read web site is the G3TXQ study of the hex beam…
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A friend is exploring antenna choices at his QTH and needs advice on some new antenna styles to try.

I stopped by for a visit to discover a very large yard with ample room for all kinds of wires antennas.

One issue my friend has it noise on his current antenna.

While his home is an excellent blank canvas waiting for lots of amateur radio antenna possibilities, I thought a full-wave loop might be a real good next-antenna to try.

Which full-wave loop to try first: 40 meter, 80 meter, 160 meter, more?

Google Earth comes to our aid with the excellent program.

Here is a view of my friend’s home…

Using the excellent tools in Google Earth I added two notional loop possiblities: a red line loop as large as the yard, and a 160 meter full wave loop in white. Isn’t this a nice big yard?

For the while loop I included the feed line as part of the total loop length to ensure a reasonable loading appears at the feed point in the house.

Using Google’s measuring tools I confirmed the white loop’s length to be around 525 feet or so including both sides of the transmission line. The red loop is about 680 feet total.

Simulations reveal the usual big lobes at higher frequencies and good behavior at low frequencies.

The big question is do we take full advantage of the yard and make the great big loop, or do we stick with a 160 meter full wave loop and live with that?

Anyone have any thoughts?

A fellow club member is preparing to put up a big 160 meter horizontal loop antenna. Nice. We have discussed many options and conclude ladder line is the best approach to connect the loop to the operating point.

He went shopping online only to find many vendors are low in stock of many items including the 400ish ohm windowed ladder line. We both agree making our own is a viable option.

So here is a photographic step by step we took in 2005 to construct the spreaders of our ladder line fed dipole antenna we use for Field Days, JOTA and other events requiring a simple antenna.

Since our antenna is used for various events it is not in the weather long. We opted to use wood spaces soaked in paraffin.
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I just came back from helping prep a ham station for a Camporee coinciding with the world wide Jamboree on the Air (JOTA) event.

They have just two antennas: a two meter omni and a ladder line fed 135 foot dipole. The dipole is inverted V style atop 12 sections of 48 inch aluminum military mast. The top of the antenna is about 54 feet AGL. Coupled with a good balanced tuner, this thing can work quite well on most of the bands.

The first contact from Virginia was with Japan on 20 meters phone. Not too shabby for such a simple antenna.

Tomorrow we will give it the big test. I know it will work fine because it has already proven its worth during many field days.

If the only antenna you have it a ladder line fed dipole, put it up and go for it.

Here are some details regarding the next, and probably last, phase of my 43 Foot DX Engineering vertical installation.

This post is very late. The actual date of the events within it are just before March 2009 in preparation for the Virginia QSO Party.

In the many posts within this site, it is no secret my examination of various vertical antenna solutions with comparison between BigIR and the 43 Foot products a big part of this. Check out all the 43 Foot posts on HHD here…
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It seems the hexagonal beam has come of age as multiple manufacturers square off in an attempt to claim market share of the growing market for this style of antenna.

Ever since the 2009 QST article many folks, myself included, became aware of the simple elegance of the Hexagonal Beam (also known as Hexbeam generally and Hex-Beam® by Traffie Technology).
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Tom, ke6ynh, asks…

“Why don’t hams like vertical dipole antennas.
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Type “J-Pole” into any search engine and you will see dozens of not hundreds plans to build your very own J-Pole antenna. Many are variations on the tried and true 1/2 wave design with the 1/4 wave stub at the bottom. Be it a plumber’s delight with copper pipe or ladder line heaven using a trimmed up 450 ohm feed line, many folks have successfully created their own J-Pole antenna with a surprising variety of materials.

However, there appears to be some kind of mystical attraction to the 5/8 wave radiator. Several of the J-Pole designs attempt to make the radiator 5/8 wave in length and adjust the phasing stub to make for a good match.

Let’s compare the two approaches using the models available from the late Larry Cebik’s NEC collection. Here are the contenders each using 3/8 inch diameter copper pipe…
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In a previous post I discussed the attributes of using two dipoles arranged ninety degrees from each other and mounted in an inverted V configuration. If fed with RF energy in quadrature, one signal delayed ninety electrical degrees from the other, you have a form of turnstile antenna.

Turnstile antennas are provide circular polarization straight up and at large angles from zenith. Originally I was going to just connect the two antennas together at my switch so I could select one, the other or both. The electrical delay would be provided by one longer feed line. However, one attribute considered essential by the scarce resources on the Internet insisted on switchable polarization: RHCP to LHCP and back by simple inverting the connection to ONE of the antenna feed lines.

With these thoughts I changed the plan a bit. Instead of using my switch and two very long feed lines, I now have one single feed line from the switch to the base of my 50 foot high antenna mast. Here I will provide a relay box with three relays, one coaxial cable in and two coaxial cables out. The two output coaxial cables will each feed one 75 meter dipole on the antenna mast. One cable is ninety electrical degrees longer than the other.

Here is a schematic of the relay box…

All this will be going into a weather proof enclosure with cables directly connected to the relays where noted.

What about perfect matching John?

I am not too worried about the perfect 1:1 SWR for this setup. In fact I don’t worry much about SWR under 3:1. The impedance presented to the radio side coaxial cable will be the two antennas in parallel although I admit I am not quite sure how these signals combine if they are ninety degrees different in phase. I forgot to look at that in EZNEC. I do remember it was not too high.

In another post I will show some photos of the resulting assembly.

As my local club in northern Virginia prepares for the March Virginia QSO Party many questions are asked about how best to take full advantage of Near Vertical Incident Skywave (NVIS) communications so critical to maximizing contacts on HF within the state.

In particular one member has a magnificent full wave 160 meter loop up around 50 feet or so. He is contemplating using it for NVIS on 80 meters. He desires to lower it to about 15 feet to improve the NVIS characteristics.

It is true lowering a dipole will focus more energy straight up while reducing the energy towards the horizon. This is a tried and true technique on 80 and sometimes 40 meter NVIS and offers a potential added benefit of less sensitivity to far away thunderstorm noise. This is a method of diminishing returns; Lowering the antenna favors the sky more, but the overall gain is reduced. In other words, less signal is focused in a better NVIS favoring pattern.

Full wave loops are quite different as this EZNEC simulation suggests. Here is a simple four sided loop with 128 foot sides and fed near one corner – just like my friend’s 160 meter loop.
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