Building a EWB/UHF Yagi – Part 1, by Tunnel Rabbit


The focus in my recent SurvivalBlog articles has been to promote communication methods, means, and technical solutions, that are easy to implement at the community level. The grassroots is where this counts most, and where it is needed most, as we will likely be on our own, and forced to be as self-sufficient as possible. In a worst-case catastrophe that we might anticipate, there will be no disaster relief agencies to assist us. Without communications of some sort, we’ve got nothing. Communications, even if limited, enable those who can to provide assistance, a local barter economy, and can be the backbone of a community’s security. One can provide better security measures for their family and closest friends, but why not have another layer that accesses some or all of the community?

In a nonpermissive and chaotic environment such as presently seen in Ukraine, we too would desperately need communications. The “Exceptionally Wide Band/Ultra High Frequency (EWB/UHF) Yagi” is my own concoction (variation of an invention). The acronym may overstate, but it sounds good, and it is mostly accurate. It is the widest-banded 3-element UHF yagi that I am aware of.

If readers can afford to step into a truly super-wide banded directional antenna, then check into a VHF or UHF Log Periodic Directional Antenna (LPDA). Here is an example of a VHF LPDA that covers 138 to 174Mhz, and claims a gain of 8Dbd. 8Dbd? No, that is not a misprint on my part. I suspect they might meant to have used Dbi, instead of Dbd. If you are asking about the price of these antennas, then you might not want know. And here is a link to a VHF/UHF line of LPDAs that advertises a price. Mine is an exceptionally wide banded yagi that costs about only a few dollars in low-cost and/or salvaged parts, and it is plenty good enough.

In the Snippets column on April 13, 2022, ‘Mike in Alaska’ provided us with a link to an outstanding overview of a situation that we might face in the future that would not be entirely unlike what is occurring in the Ukraine today: Survival Radio & Emergency Communications Ukraine. It is an excellent overview of the role that radio communications can play on several levels. Thanks Mike, it is good stuff. It spurred me on to write this article.

Note that the video stresses that there is a serious risk of being ‘direction-found’ (DF’ed). Although, there is no mention of directional antennas, or detailed instructions, aka Signal Operating Instructions (SOI), it was a sorely needed, and an impressively well-done overview. Some of the details on how to get it done, is some of the information I am providing that is hopefully digestible for most folks who are not so technically inclined. Hopefully, there is something here for everyone, including us radio geeks as well. A word of warning. As a self-proclaimed geek, via a lifelong experience speaking and working with non-geeks, it does no good to totally geek out, as the audience will simply turn the geek (me) off. A blank stare is the usual and painful indicator that I encounter. Yet we’ve gotta engage our brain, and get the job done. We’ve gotta get serious, and get focused so that we can crack this tough and critically important nut that is radio communications. As the Army folks say, “Without commo, you’ve got nothing“.

As it could provide the context to better understand the purpose of this article, please see this outstanding video if you are at all interested in radio communications: Survival Radio & Emergency Communications Ukraine. I’ve been striving to learn everything and more covered in this video for more than a decade. After the video, come back to this article, or read it again. It will make this article much more interesting and useful.

What is the Tunnel Rabbit EWB/UHF Yagi?

What I’ve dubbed the Tunnel Rabbit  Exceptionally Wide Band/Ultra High Frequency (EWB/UHF) Yagi is a home built 3-element UHF yagi antenna that anyone is welcome to duplicate, and I hope they will. Or they could do so long after the Internet is no longer accessible as they can refer to a copy of this article. In my opinion, it is a much better choice than a discone that is truly an ultra wide band omni-directional, yet it does nothing to control the signal. As with all my antennas, it was designed and built for a non-permissive and austere environment. After certain modifications were made to make it wide banded, it was found to have an impressively flat SWR of less than 1.8:1 between 411 to 475 Mhz, rather than only 462 to 468 Mhz needed for GMRS. It could be that only a LPDA could do much better.

There are many nodes that are 1.1:1, and it rare exceeds 1.5:1. It covers the entire 70 cm Ham band, the UHF business band, and GMRS, and more on both ends. Note that the UHF business band is from 450 to 469 Mhz, and that there are business band frequencies interspersed within a range that includes the GMRS/FRS frequencies that is generally considered to be 462 to 468Mhz. GMRS and FRS are actually clustered together between 462 to 463Mhz, and 466 to 467 Mhz. Because GMRS and FRS are crowded together, to avoid interference with FRS, and to remain Part 95 compliant, be sure to use the narrow band setting when programming in the GMRS/FRS frequencies. Most VHF/UHF frequencies on most radio services, except the Ham bands, require narrow band. By using narrow band on GMRS, we can better avoid spilling over onto FRS, and you might avoid being overheard on FRS. Tactical communications necessarily means that we should limit our audience. Always use narrow band unless on the Amateur frequencies.

For What Frequencies Can This Yagi Be Used?

If you are a licensed Amateur Radio Operator, then you can use the 70cm band, 420 to 450 Mhz. The rest of what this yagi can use is channelized, and requires a license to use the business band. The business band is everything that is not the 70cm, or GMRS/FRS frequencies.

Family Radio Service (FRS)
462.5625 M FRS Ch. 1 (shared with GMRS)
462.5875 M FRS Ch. 2 (shared with GMRS)
462.6125 M FRS Ch. 3 (shared with GMRS)
462.6375 M FRS Ch. 4 (shared with GMRS)
462.6625 M FRS Ch. 5 (shared with GMRS)
462.6875 M FRS Ch. 6 (shared with GMRS)
462.7125 M FRS Ch. 7 (shared with GMRS)
467.5625 M FRS Ch. 8
467.5875 M FRS Ch. 9
467.6125 M FRS Ch. 10
467.6375 M FRS Ch. 11
467.6625 M FRS Ch. 12
467.6875 M FRS Ch. 13
467.7125 M FRS Ch. 14

General Mobile Radio Service (GMRS)
462.55 R GMRS (also may be used simplex)
462.575 R GMRS/White Dot (also may be used simplex
462.6 R GMRS (also may be used simplex)
462.625 R GMRS/Black Dot (also may be used simplex)
462.65 R GMRS (also may be used simplex)
462.675 R GMRS/Orange Dot (also may be used simplex)
462.7 R GMRS (also may be used simplex)
462.725 R GMRS (also may be used simplex)
467.55 GMRS (also may be used simplex)
467.575 GMRS (also may be used simplex)
467.6 GMRS (also may be used simplex)
467.625 GMRS (also may be used simplex)
467.65 GMRS (also may be used simplex)
467.675 GMRS (also may be used simplex)
467.7 GMRS (also may be used simplex)
467.725 GMRS (also may be used simplex)

UHF Itinerants
451.8 M
451.8125 M
456.8 M
456.8125 M
464.5 M Brown Dot
464.55 M Yellow Dot
464.6 M
464.625 M
464.65 M
464.7 M
464.725 M
464.75 M
467.75 M
467.7625 M J Dot
467.775 M
467.8 M
467.8125 M K Dot
467.825 M
467.85 M Silver Star
467.875 M Gold Star
467.9 M Red Star
467.925 M Blue Star
469.5 M
469.55 M
469.6 M
469.625 M
469.65 M
469.7 M
469.725 M
469.75 M

Motorola UHF Radios
461.0375 M
461.0625 M
461.0875 M
461.1125 M
461.1375 M
461.1625 M
461.1875 M
461.2125 M
461.2375 M
461.2625 M
461.2875 M
461.3125 M
461.3375 M
461.3625 M
462.7625 M
462.7875 M
462.8125 M
462.8375 M
462.8625 M
462.8875 M
462.9125 M
464.3250 M
464.4875 M
464.5125 M
464.5375 M
464.5625 M
464.8250 M
466.0375 M
466.0625 M
466.0875 M
466.1125 M
466.1375 M
466.1625 M
466.1875 M
466.2125 M
466.2375 M
466.2625 M
466.2875 M
466.3125 M
466.3375 M
466.3625 M
467.7875 M
467.8375 M
467.8625 M
467.8875 M
467.9125 M
469.2625 M
469.4875 M
469.5125 M
469.5375 M
469.5625 M

Why Build the EWB/UHF Yagi?

First, you may ask, why build a GMRS yagi? Because GMRS is the most common transceiver that our neighbors are most likely to have. So why build an exceptionally wide-banded, ultra high frequency (EWB-UHF) yagi? To talk to transceivers other than GMRS transceivers. It is better to have the ability to use a single antenna that can transmit on many bands, or radio services, and if it is also a directional antenna, it is even more versatile. If we wanted to cover as much of the VHF/UHF radio spectrum with one antenna, and potentially, with one transceiver, then we would choose a discone antenna such as the Tram 1411. However, if we would like to control our RF footprint to improve Communications Security (COMSEC), and perhaps increase the range of our handheld or mobile at the same time, while reducing the odds of interception, then a moxon or yagi antenna that is broad-banded is the best choice. It is not merely convenient, it is a wise choice that not only reduces cost, but also increases our capabilities, and therefore improves COMSEC.

The EWB yagi is, in part, a solution to the risks mentioned in the video, and enables the user with a simple Baofeng UV-5R (or similar), to operate in large part as the aforementioned video discusses, across several radio services, or bands. Ideally, we should also be able to do the same on VHF. If a person only had this UHF yagi, they would have a versatile antenna that also transmits to the most common transceiver in the U.S., GMRS.

Estimating Range

What kind of range can this yagi provide if it has a gain of 7.5Dbi? Estimating range can be a tricky thing, but with an educated assessment (guess) based upon empirical knowledge (experience obtain by trial and error), we can estimate what it might be its range in ideal terrain, and what the range might be, given the least favorable terrain that we would likely be operating in. Before we can estimate range, a number of variables need to be considered.

Without deducting for coaxial cable line loss, using a Baofeng transmitting with 4 watts and connected to the yagi using only a few feet of cable, the ERP would be around be 13.4 watts. That is if we are using a handheld antenna when working out of a backpack. If at a base station, we’ll need 30 to 50 feet cable. Because of the cost, most will use RG58, or RG8x. If 40 feet of RG58 is used, then the ERP would only be around 6 watts out the front. This is not necessarily a bad thing as we would have a narrow footprint, and a low power level puts a limit on the range, yet it has a usable range that can be reduced by pointing the yagi toward the ground right in front of the target station. Or it can be pointed into a hillside or mountain, and the receiving station could hear the side lobes.

If using 40 feet of LMR-400 coaxial cable we would have an ERP of around 11 watts. If two stations pointed two of these yagis directly at each other, they might be able to successfully use GMRS at a range greater than 20 miles in favorable terrain, if the antennas are mounted high enough. If the station is located 1,500 feet above the average terrain and no obstruction inside of the line of sight to the target, then the distance that 11 watts can travel would be considerably further, perhaps, as far as the visible mountain tops in the distance.

In a pine forest, such as in my area of operations (AO), the increased gain might be necessary to make a reliable communications circuit if used within a range of under 5 miles. Here, we do not have ideal terrain for UHF. Pine trees soak up UHF. If using a Baofeng, and extra power in terms of ERP is needed to get through the pine trees, they can use 40 feet of LMR400 for an ERP of 11 watts.

If 40 feet of RG58 were used, the ERP would be reduced to 6 watts. We could use a ‘lossy’, or inefficient cable to intentionally reduce the power out! And we’d have the benefits of a directional antenna. But more often than not, especially if located in a pine forest, then we’ll need to use the equivalent of the more expensive LMR-400 as it would provide the much-needed extra power to go the distance through a pine forest.

Design Goals Met

Most of my friends and neighbors would benefit from a GMRS yagi, and the community would be safer if a homemade yagi, and any GMRS antenna for that matter, could be easily produced at home at a time when purchasing a new yagi might not be possible. While I appreciate the much higher front to back ratio of a moxon that I would use to contain a signal within an AO, this 3 element GMRS yagi has it’s place, because of the ease and lower cost of manufacture, the higher gain of 7.5Dbi, versus 5.75 Dbi for the moxon. And as it happened, with a little trial and error, it became very broad-banded, and capable of not only GMRS, but 70cm, the UHF business band, and more. With two of these yagis produced, I am confident that my design is reproducible by others. Because it is exceptionally broad-banded, any attempt to reproduce it would likely be satisfactory and useful even it were only good for GMRS, or 70CM, because the builder made a mistake or two, and the yagi will not tune up for the expanded bandwidth. Even if the attempt was poorly executed it could still be useful.

The second attempt at producing a EWB yagi was the best example. It has an SWR of less than 1.8:1 between 411 to 475 Mhz. The prototype has a SWR of less than 1.7:1 from 428 to 474 Mhz. I doubt that it is possible, and there is now little need to improve its range at this point. “Perfection is the enemy of good enough.”

(To be concluded tomorrow, in Part 2.)