Greetings from UK.
I recently learned that POTA [is now in the] UK so I am really looking forward to it.
I also recently put an order for [the Discovery TX-500] so I am really excited as well.
I would like to create a very compact setup pouch for field use to pair with this radio; one that I could take to summits or parks and also travel abroad.
What battery and antenna would recommend?
Would you recommend an ATU?
Or would you compromise to fewer bands or pack a secondary antenna?
I love to know your opinion.
Great questions, Vitor! In truth, these sorts of questions are easy to ask but quite complicated to answer due of the insane number of options and possibilities available. It’s impossible to cover them all so I’ll try to give you some suggestions based on what I tend to use in the field.
I’m a big fan of LiFePo4 batteries for a few reasons. Most notably:
- they’re stable and safe,
- they offer a longer cycle life than Li-ion, NiMH, NiCad, or Lead Acid batteries,
- they have a constant discharge voltage,
- they’re lightweight,
- and LiFePo batteries have a lower self-discharge.
I go into way more detail about batteries in this article on QRPer. I’d encourage you to read through it before making a decision.
I’m such a big fan of 3 Ah LiFePo4 batteries for SOTA and POTA, I recently purchased two more from Bioenno! They’re a great size for the average park/summit activator using a QRP radio like the TX-500. If you were using a 50-100 watt radio, you would need a larger battery.
There are so many amazing antenna options to choose from! Of course you can purchase one that is rugged, tested, and pre-built, or you can very easily build one yourself from a kit or from a few spare parts!
There are so many options, in fact, whole series of books have been written about wire field antennas. It’s beyond the scope of this post to take a seriously deep dive.
Putting this topic in a huge nutshell:
Resonant antennas are excellent because they require no impedance match (ATU) and are typically more efficient than non-resonant antennas.
A couple multi-band resonant designs that are very popular among field operators are the End-Fed Half-Wave (EFHW) and the Linked Dipole. You can easily find finished products and build-at-home kits for both of these designs. Since you’re in the UK, check out the offerings at SOTAbeams.
Again, there are dozens of other field-proven designs out there. I would suggest you join the SOTA reflector and read through the archives to discover various options summit activators are using.
In short: there are a wide variety of effective resonant antennas out there.
ATUs and non-resonant antennas
With that said…
I’m a huge fan of pairing antenna tuners (a.k.a. trans-matches) with non-resonant antennas. Why?
To make a long story short, if you have an ATU, it opens up a world of very inexpensive antenna experimentation. For example, with a good ATU, you can turn 28.5 feet of speaker wire into a very useful field antenna. Or, you can build a multi-band doublet.
Non-resonant antennas tend to be more portable than a resonant antenna with the same frequency coverage.
Even if you only plan to use a resonant antenna, I think every field op should carry a good portable ATU. Why?
- Think of it as an antenna first aid kit. If your antenna breaks or fails in the field, an ATU can save the day by at least matching the impedance so that your transceiver will be happy. This happened to me last year, in fact, when I broke my antenna on a remote summit. My ATU saved the day.
- Most multi-band field antennas are designed to be resonant on 80, 40, 20, 15, and 10 meters. If you happen to be activating on a contest day and the bands are crowded, an ATU will help you find a match on 60 meters and the WARC bands (30, 17, and 12 meters) where contesting is not allowed. This sort of frequency agility also comes in handy on days when some bands may be unstable or local QRM is wiping out a particular band.
Portable ATU options
It’s extremely rare that I hit the field without an ATU. Many are so small and lightweight, you don’t even notice them in the pack.
Here are a few of my favorites:
The ZM-2 is a manual field antenna tuner that can match almost anything. I once matched two trampoline frames and made contacts using the ZM-2.
There is a very modest learning curve with the ZM-2–check out this article where I break down the process.
The ZM-2 is one of the most affordable tuner options out there. I checked and you should be able to purchase a fully-assembled and tested unit for roughly $123-125 shipped from the US. Of course, the kit version will be less expensive.
LDG Z-100 Plus
The LDG Z-100 Plus is a workhorse of an ATU. It’s also one of the more affordable automatic antenna tuners on the market. The Z-100 Plus has a very wide matching range and requires very little of a battery since it sports latching relays.
It is a little bulkier and heavier than the other two potable ATU options I mention here, but it can also handle more power output if you decided to pair it with a larger radio at some point.
The Z-100 Plus retails for roughly £170 in the UK ($150 in the US).
The Elecraft T1 is my favorite portable QRP automatic antenna tuner.
I love the T1 because it’s so compact/portable, lightweight, and easy to use. It also has a very wide matching range. The T1 has never let me down in the field–it can match almost anything you connect to it. I frequently pair the T1 with my TX-500.
The T1 is also one of the pricier options on the market at time of posting–noting we’re still experiencing pandemic supply chain issues–and there may even be a lead time. Personally, I think it’s worth the wait and price.
I hope this gives you a starting point, Vitor. Again, it’s always difficult to answer questions like this because there are simply so many options and directions one could go. Everyone will have their own opinions.
On that note, my hope is that readers will comment with the antennas, ATUs, and batteries they use!
I’d like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I really appreciate the support.
Cheers & 73,