“What battery, antenna, and ATU should I pair with the Discovery TX-500?”

Many thanks to Vitor Morais who asked the following question in the comments section of my YouTube video:

Hi,

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.
Thanks

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.

Battery

There’s an abundance of battery choices out there.

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.

Also, knowing that you’re in the UK, you might check out this article and, specifically, the comments section where you’ll find links to UK LiFePo4 retailers.

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.

Resonant Antennas

The MFJ-1984LP EFHW is an affordable, fully-assembled antenna.

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.

There are many EFHW kits on the market including this simple one by KM4ACK.

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

If you’re on a tight budget as you piece together your first field kit, stick with a resonant antenna as it is an effective and affordable way to get on the air quickly!

With that said…

I’m a huge fan of pairing antenna tuners (a.k.a. trans-matches) with non-resonant antennas. Why?

To avoid repeating myself, you might check out this post and video I put together a few months ago…a “hike and talk” on this very topic:

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?

  1. 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.
  2. 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:

Emtech ZM-2

I’ve often said that the ZM-2 is one of the best values in the ham radio world. Every QRP field operator should have one in my humble opinion.

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.

Click here to check out the Emtech ZM-2.

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).

Elecraft T1

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.

You can purchase the Elecraft T1 for £249.00 from Waters and Stanton in the UK (or $260 in the US directly from Elecraft).

More suggestions?

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!

Thank you

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,

Thomas (K4SWL)

23 thoughts on ““What battery, antenna, and ATU should I pair with the Discovery TX-500?””

  1. I run a very similar setup to Tom’s. The last time I took the TX-500 out I used a Chameleon 40 meter OCF dipole. It is a 66′ antenna and I had it about 20′ off of the ground at the apex. It worked really well. For an ATU, the Elecraft T-1 is hard to beat and I also use Bioenno batteries. The 3 amp/hour is great for POTA/SOTA.

  2. ATU10 is hard to get, but worth checking out. It’s a qrp version of ATU100, with full automation support for ic705. It a little bit thicker than T1, but has OLED display and rechargeable lithium batteries.

  3. Now let’s talk about making sure your POTA kit includes a pint of Guinness! “Every ounce counts!”

  4. Thank you Vitor for the question; thank you Thomas for tackling the answer.
    This article helps cement my thoughts as I learn more and get out there in the field. I also use a ZM2 and really like it.

    73
    WB8YXF

  5. Also check out the mat tuner (mat-10) from dx engineering. Its like the elecraft t1 but with a metal case instead of plastic. And a rechargeable battery.

    W4SOU

  6. My new field (and back-porch-activation) kit is an Icom 705, LDG Z100+, Elecraft AX2 (including the 40m extender it fits perfectly with the base inductor unscrewed in a MaxPedition “skinny” pocket organizer! Thanks for that recommendation too. BTW the pocket organizers are still BOGO!) and/or an EndFedz EFT 10/20/40. As you’ve noted before, the LDG ATU is SIMPLE to use, sips on internal AAs, is much less expensive than the Elecraft and really not too big for someone looking to start out with drive-ins or very easy hikes (vs. all-day SOTA).
    The LDG ATU was recognized immediately by the 705, and quickly tuned up the non-resonant AX2 – could hear Quebec and Cape Town, SA from my NC back porch, but couldn’t break the pile ups w 5w SSB. The LDG ATU also barely burped tuning the EndFedz on 40m – looking forward to getting it length-resonant on 40/20 and running 10w SSB.
    (Unfortunately had to return/exchange the 705 after one evening due to bad speaker/mic jacks that kept cutting out. BIG props to DX Engineering for their customer service. New one due any day.)
    73
    W4LTC

    1. The MaxPedition skinny was one of my Christmas presents. I asked for it as I want to get an AX-2 for my QRP POTA setup after seeing Thomas’ recommendation.

      I am not the pack geek that Thomas is and I can’t afford most of his stuff. But I am a guru at long range planning. All of my purchases have an end goal of fitting into the QRP dream kit that is my long range goal. I am good at researching equipment needs and finding options. I constantly re-evaluate as I learn new stuff or as new rigs come on the market. I also like the modular approach that Thomas uses so that I can grab a bag from one setup to use in another comm go bag.

      My son gave me some good advice; buy once, feel the pain once. No regrets.

      1. Marshall, not sure what QRP radio you have, but my Icom 705 WITH the Peovi cage and plastic front cover fit perfectly in the MaxPedition large (12″x5″) bottle holder pouch with plenty of room for the mic and cord on top. Front pocket has room for power cord, and small adapters.

        The “Skinny” pouch is perfect for the AX2 (and would work for AX1 too). I tried the “Fatty” for my LDG Z-100+ tuner, it fit, but VERY tight. The “Beefy” pouch is larger and easily holds the tuner with PL-259 to BNC adapters attached, 20′ of RG-318 coax, interface cable and extra adapters. (I went a little nuts with the BOGO pouch sale – BTW, it’s STILL active on the MaxPedition site today!)
        73
        W4LTC

        1. Hi Walt.

          Thanks for the info. My current QRP filed rig is a Xiegu G90. I wrap it in a Domke Protective Wrap (https://smile.amazon.com/dp/B00009R88F?ref=ppx_yo2_dt_b_product_details&th=1) and I carry it in a tactical shoulder bag.

          My long range goal is to get Lab599 Discovery TX-500. I have several resonant antennas and the G90 has a built int tuner so the Elecraft antenna and tuner will be for the TX-500. I want a complete shack in a small bag.

  7. Don’t forget to check m1ecc antennas in the UK. I’ve only just received my “slidewinder” portable antenna this week, so haven’t had a chance to play, but paired the KX3, I am hoping to get out to play sometime real soon. I certainly was able to tune it to be resonant on 20m, rendering the ATU in the rig un-necessary. Mike G4TVP.

  8. Chuck,
    There are 15 other eHam reviews of the TX-500 since the first one I did back in Nov 2020. Do search under Product Reviews for “TX-500”.

    73,
    Henry – K4TMC

  9. Good article – the battery box coming from theqrpstore looks interesting and fits the radio well – also a while ago Lab599 showed of a protype aluminum battery box that fits on the back of the TX500. Agree – resonant antennas are the best way to go – the power amplifier from DIY599 has a built in ATU – see the reviews by OH8STN – it also fits the 705

  10. Having recently purchased a TX500 (an amazing radio) I was able to try it extensively over the Christmas holidays whilst visiting relatives.

    Recognising that this doesn’t have the tuner of my KX2 I deliberately purchased a QRP EFHW to use that would be resonant and strung this up across the lawn into an adjacent tree. I got some really good results and was suitably impressed. In the UK I sourced the EFHW from WireAntennas.co.uk, the actual model being the beautifully built “SOTA HWEF KEVLAR ANTENNA QRP 49:1 10 WATTS”.

    For a battery I used my existing TalentCell Rechargeable 36W 12V/6000mAh LiOn battery pack, which naturally limited me to about 4w peak output – not a perfect solution in terms of pwoer but one charge lasted all holiday and even then wasn’t even half depleted – the TX500 is an efficient radio. These oacks can be purchased at Amazon.co.uk

    Long and short this combination gave a deployment time in a few minutes and hours of fun on both SSB and CW!

    And yes, longer term I am looking for a suitable 3Ah LiPo, but for some reason these seem difficult to obtain in the UK; Bioenno cells are not available over here.

    Richard M0RGM

  11. Hi.
    What length of wire and what length of counterpoise do you use when connecting a long wire directly to your ELECRAFT-T1 ?
    73

  12. Great article. I have an Emtech ZM2 tuner. Have not used it yet, I am building a QRP GO KIT. I have also used the 16 GA speaker wire from wally world and made an antenna from it. It made the trip from NC to PA on 5 watts so I will attest it works.. what type of coax are you using and how long for your MFJ1984LP EFHW? 73s de KD8VSP

    1. Hi, Steven,

      I use both RG-58 and RG-316–depending on the application. Since the MFJ EFHW has an SO-239 connector, I tend to use RG-58 which is terminated in PL-259s.

      The ZM-2 will treat you well–it’s a brilliant little tuner!

      Cheers,
      Thomas

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