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SOTA Antenna Advice


#1

Hey folks,

I’m farily new to amateur radio and even newer SOTA and QRP, but I do know that QRP is where my main motivation and desire lies (despite the cursed solar cycle). So after much deliberation and research, I’m putting together my QRP HF setup. I was inexorably torn for a while between an FT-818 and a KX2. I’ve finally narrowed that down to the FT-818 (at this moment anyway) mainly because of the cost difference once you take into account the ‘extras’ like the ATU and the hand mic (which are necessities in my mind if you’re buying a KX2).

My question comes with an antenna to go with the FT-818. I’m somewhere between a linked 40/20 dipole and a 40m EFHW with a mountain tuner and the knowledge that will work on 20m, but not as well as a 20m EFHW. 40m and 20m are the two main bands I’m concerned with right now (Yes, KX2 with a random wire would’ve been a different story).

So I’m turning those much more experienced than I - What would be the best compromise for a SOTA antenna setup with a collapsible mast?

And, yes, I may cry if you say I should suck it up and go with the KX2…but I would listen to reason. The FT-818 was mainly because of cost (and fear of the fragility of the KX2).

73,

  • Sean/W4BKR

#2

Hi Sean,

In regards to your antenna queries I’d recommend that you start with a simple linked dipole for SOTA. You’ll find that they’re quite resilient to different operating environments and will provide good efficiency. If you’ve got your heart set on an EFHW then things get a bit more complicated with regards to the matching transformer. In any case it’s good to have a couple of options and the dipole can make a great backup antenna anyway. The Pico balun from sotabeams (https://www.sotabeams.co.uk/pico-balun-1-1-or-4-1-balun-kit/) makes a good building block, don’t go smaller than 22 AWG wire (I like the silicone insulated stuff), and the linked antenna designer on sotamaps (click the appropriate tab: https://www.sotamaps.org/extras.php ) will put you pretty much at resonance.

In regards to the transceiver I’d recommend the KX2. I’ve used both, own an FT-817, and I’d take the KX2 over the FT-817/818 any day of the week. They’re both good rigs, but when comparing things like receiver performance, size/weight, output power, future updates, and ease of use the KX2 comes out on top every time. The construction is robust enough that you’re not going to notice the difference between the two (except for the weight.) I’m perfectly comfortable going skiing, mountaineering, and alpine climbing with a KX2 in my pack. If you’re going to spend money on a transceiver for SOTA then spend it once and get a better rig.

Cheers,
John VA7JBE


#3

Hi Sean,

Since the FT-818 has no tuner I’d recommend a no-tune antenna. I prefer my 3 band endfed for 20, 30, and 40m band. It has traps at 14 MHz and 10 MHZ. With a 1:49 transformer and about 5 m of lightweight RG 316 koax the SWR on all bands is better than 1.8:1 (at the band limits. Around e.g. 14.280 MHz mine shows 1.3:1.
There is one big advantage of the endfed versus the linked dipole: you can change bands very quickly (e.g. for a quick summit to summit contact) without getting up and lowering the mast to reach the links.

73
Peter


#4

Antennas can be home made for very little cost. There is no rule saying you are restricted to one antenna - you can build ten antennas and learn how they compare over time. I have 3 currently in frequent use for hf. I often take both a linked dipole and a vertical with me, on backpack excursions. My preference is to use the vertical on 20 and 30m but use the linked dipole on lower bands.

Experiment!

Andrew VK1DA/VK2UH


#5

I am using single band dipoles for my SOTA activations, and my most common used antenna is 20 m dipole. If you will build it by yourself - materials may cost less than $1.


#6

Hi Sean!

I started with an FT-817. I now have a KX2 and an MTR3B (for backpacking trips). I wouldn’t go back to the FT-817. It was an ok radio, but the KX2 is a superior rig. I am primarily a CW op, so keep that in mind. The 817 does bring 440/2m/6m to the table, so if those bands are important to you that might be a factor. I always carry an APRS capable H/T for spotting and 2m/440 FM contacts.

The KX2 isn’t as fragile as you might think. Mine has been on about 100 summits now, and is holding up fine. It has been wet a number of times, and I’ve had to remove the display cover to get dirt out of it a couple of times. The tuner is fantastic, the receiver is amazing, and the filtering is really nice. You don’t have to use the Elecraft mic - you can modify a cheap H/T mic and it will work. I’ve seen threads on this reflector with details.

You will be successful with either radio, so you just need to decide what your priorities are.

You asked about antennas. I’ve mostly used inverted V dipole antennas that don’t require a tuner - important for my MTR3B. My current favorite is a 20/30m linked dipole. Works great and cost me a couple bucks to make. Support the center with a tree or one of those cheap 20’ fishing poles from eBay - I think mine was $12 shipped and packs down small enough to fit inside my pack.

A lot of people also use various end fed antennas. There are several designs, and they all work quite well. They are easier to set up on some summits, and generally work as well as a dipole. Build a couple of each and try them out - you will find that when properly constructed they all work very well and you will have no trouble making contacts. Biggest advantage with end fed + KX2 tuner - no fooling around with links on the dipole to change bands.

Very important: make sure you post alerts before you go on a summit. When you get to the summit, make sure you spot yourself. If you get spotted you are very likely to make enough contacts. There are lots of ways to get spotted, and you should become familiar with them. SMS (requires prior set up), APRS, RBN Hole (CW only) are a few that I use frequently. I’d say that APRS has saved my bacon on a growing number of summits and is well worth taking along.

Good luck - whatever you get you will have a blast. SOTA is the MOST fun I’ve had in my 20 years of ham radio. But beware, you get high and its very addictive! =)

-Josh WU7H


#7

I’m currently using an end fed with a tuner. Before that my go-to was a speaker wire doublet. I’m planning to make a linked efhw for 20-30-40 in the near future so I can ditch the tuner.

Wire is cheap. Have fun experimenting :smiley:

Also, +1 for the Elecraft rigs. They are very nice, and can be used for your base station at home too.


#8

Hi Sean!
After numerous experiments, I came to the conclusion that the 1/4 lambda GP antenna on a fiberglass rod is the most optimal solution for working from the top of the mountain.
This is when the top is free of trees!
If there is a forest at the top, then half-wave dipoles work more efficiently.
I prefer to use a dipole in the sloper configuration, if there is at least a small glade.
Everything is very dependent on local conditions.
http://reflector.sota.org.uk/uploads/db9433/optimized/2X/f/ff8e79f0ef07e467a2f9e4a51f1ae4210313c470_1_333x500.jpg

The time factor at the top is usually very important.
The GP on the fishing rod is installed very quickly, but it is a single-band antenna. I solved this problem by installing an LDG Z-817 tuner at the base of the antenna. The exact solution turned out to be very convenient, fast and easy. A 14 MHz GP becomes a multi-band antenna, with good efficiency at 18, 21 and 24 MHz, and a not bad at 10 MHz.
If you add additional (quarter-wave) radials, then the efficiency at 10 and even 7 MHz can be significantly improved.
http://reflector.sota.org.uk/uploads/db9433/optimized/3X/1/6/16e08815dba585f5baed54bccd98a5c2e1e803c7_1_690x460.jpg
I especially like that the height of the antenna from the surface, the location of the radials, icing and other factors are no longer a problem in terms of matching )
As for the dipole, this tuner is also useful for solving the problem of its multi-bandwidth. It is only necessary to change the coaxial feeder to a symmetrical line …
73!
Vlad
RX9WT


#9

Wow! Thanks for the replies. They had the effect I figured they would. I’m leaning back towards the KX2. I tried to rationalize myself out of the buy-once-cry-once mentality, but the KX2 just has a lot more room for me to grow into. The lack of a built-in tuner was my one nagging issue with the FT-818. Definitely something that could be overcome though. I just didn’t like the idea of dragging two or three different antennas and having to swap them out. I like the idea and six of the MTR-3B, but I have yet to grasp CW so it’s primarily SSB for me for now. It’s good to hear that the KX2 is hardier than I thought. That’s part of the problem with the inter web - it’s hard to get a unified opinion. Regarding antennas, I didn’t mean to make anyone think that I had plans to just buy an antenna. My intention was to build one. I’m still fairly wet behind the ears and actually doing it myself is the only way I’ll really learn.

The linked antenna designer is going to extremely useful. I didn’t see that in all my SOTA scouring.

Thanks again for all the awesome advice!

  • Sean/W4BKR

#10

I’ve been using a linked dipole almost exclusively since 2011.
Started out with just 20m and 80m. My current antenna is cut for 10, 12, 15, 20, 40 and 80m.
I also have a shorter antenna for 12, 20 and 40m.

http://vk3zpf.com/link-dipole


#11

As a slight variant on the quarter wave vertical, mine is actually a linked vertical. I inserted a link for 12m when we had the 12m challenge and also added more wire and another link to take it to 30m. I increased the radial length to suit 30m and while it still works ok on 20m with the 30m radials (7.5m instead of 5m) I recently bought some larger slide switches to use for retuning the radials for 20m. Ie. open the switch for 20m, close it for 30m. With 20m not returning many contacts at present I have not been too concerned about 20m and have used other antennas there.

The link connectors I use are auto electrical spade lugs. I would go for the bullet shape next time, spade lugs are probably good electrically but they are hard to connect and disconnect with stressing the wires.

Although the vertical with 3 radials is basically a single band antenna, what you get for the “inconvenience” is a very efficient antenna. I’ve worked lots of dx at 10watts with mine.

With QRP power levels, don’t waste limited power with substandard antennas. Loading is generally wasteful, a full size resonant wire is much more effective. IMHO…

73 Andrew VK1DA/VK2UH


#12

As you can see Sean, ask a simple question and get lots of answers. There’s no right answer just people telling you what they use. You can read all the books on antenna design etc. and you can learn how they work and how to design them for the bands you are interested in. Then you need to take on board that SOTA operating adds a whole set of extra requirements to your antenna.

The first is deployability. Whatever you make you need to be able to deploy it on your own. In wind and rain and snow and more wind? Can you rig it up with gloves on? Can you connect it with gloves on?

The second is durability. The antenna will be setup and taken down at least once per trip and then coiled up. If you do several summits in a day then your antenna will be up and down all the time. All that will take its toll on connectors. So every connection needs to have some kind of strain relief or it will fail after repeated use. You need to use wires that will cope with this kind of abuse.

The third is weight. You have to carry it on your back. Up and down. So don’t make it out wire you could use to tie up a super-tanker. Whilst you can now run 100W for a good few hours without needing a team of sherpas to carry the batteries, 100W level is still relatively rare. 25-40W is not uncommon but the vast majority will be using 5W (817 class) 10-15W (Elecraft KX2/3) or less (Altoids radios). So you don’t need to use massive cables. But don’t overlook item 2!

As for the antenna, it will depend on your location and what you want to do. Most of the time “make SOTA contacts” is the requirement. Sometimes we have special activity sessions (EU<>VK or EU<>USA) and you may want to select different antennas and powers for those from normal “vanila” SOTA antennas.

For me in Scotland, I have few summits that have trees and so this makes a small telescopic fishing rod essential. That needs some method of fixing, either lash the pole to fence post or use a set of guys. I use 5m rods and the top section is generally unable to support much weight hence the feed point is around 4.5+m (about 15ft). An inverted dipole at that height for lower bands is a different beast to a horizontal dipole 1/2 wavelength above ground. It will be much more omni than you would expect and it wont be a DX antenna.

I mainly use a 60m/40/30m link dipole with a SOTArised clone of a Buddistick for 30m/20m/17m/15. The Buddistick clone works well and is quick to deploy but it is obviously down in performance compared against full sized 1/4w GP antennas. When the sun is very active, a wet noodle lets you work DX. But at the solar minimum, the lower performance stands out. I’ve just built a 17m/20m/30m dipole which in testing seemed a lot more lively.

EFHW (end fed half waves) are very popular because if you have trees on most summits, you can thrown one end of the wire up into the trees and let the antenna drop back to your radio or slope back. So you don’t need the fishing pole a lot of the time.

For a dipole, you need a length of coax that runs up your fishing pole plus a few metres to reach to where you are sitting. This will have some loss for the very lightweight cables. Less loss means more weight. An EFHW can be attached without any real feeder and so saves on this weight and loss. But you need a matching unit which is simple to make but can be lossy. Horses for courses!

As a newbie, I’d make a link dipole to begin with. Not because I think it’s the best but it’s the easiest to make and get working with limited experience and tools. Have a play with that. Likewise 1/4wave GP is a great antenna but needs a bigger pole quickly as it will be 1/4w + 1/8w in height. Also do try an EFHW. Making the matching unit is not hard and there are loads of designs to follow as well as kits of components available.

When you have all the kit ready, pack your bag and go and setup in a local park. Then you can make a list of everything you used and everything you forgot. That will help you pack the kit you definitely need along with stuff that may be useful but wasn’t needed. You don’t want to find out you forgot some essential gizmo when you’ve driven for 2hrs and walked for 3hrs. In miserable weather!

Above all, go out and have fun.


#13

Two comments:

  1. if your summits are packed in with trees (as they often are in the northeast USA), an EFHW (single ended) will be easier to deploy than a doublet (double ended).

  2. I’m not a fan of linked antennas - they make band changes too cumbersome/slow especially if the weather is very cold or I’m trying to chase an S2S on another band. I prefer either trapped multi-band antennas or non-resonant antennas using my KX2’s ATU.

73 Barry N1EU


#14

Sean

As stated earlier, EFHW are popular in the US and I like others have been very happy with the LNR Precision Trail Friendly.

https://www.lnrprecision.com/store/EFT-10-20-40-Trail-Friendly-p39885475

I think you are based in VA and if your activations are generally in that area maybe 20m and 40m will do you just fine.

For what its worth I support my end fed with a carbon fibre fishing mast that works fine and never use trees even if they are around.

And also for what its worth, the Elecraft KX2 is fabulous radio which has worked for me for many activation. I like that fact that the battery is internal and sufficient to run 5-10w for 2+ hours.

Paul


#15

At the moment, due to the solar cycle, the vast majority of my contacts are on 40m. With this in mind, you could try a monoband end-fed for 40m from SOTABEAMS:

It will work well with an FT-818 if you decide to go down that route, and would be about the lightest option possible. You could buy the Laserbeam filter for your 818 at the same time:

There is also a speech compressor available. Then again, if you’re going to shell out for so many accessories, mabye you would be better off with a KX2. I love mine.
de OE6FEG / M0FEU
Matt


#16

Hi Sean,

It’s normal for me to try a different antenna each month looking for a better compromise or just wanting to do a field test of an idea that has been buzzing around in my head. The gold standard for me is the SOTABEAMS 80/40/30/20 linked dipole. It is a bit slow to change bands but there is no ATU to carry and no toroid match required. Inevitably some signal is lost in the ATU or the toroid but the convenience in band changing might be seen as worth the loss.

Last Friday I used a tuned feeder to a 30 m half wave with an ATU on one summit and the SOTABEAMS linked dipole on the second summit. I had the same number of contacts on each.

I use an FT817 for backpacking trips - owned it before the KX2 or KX3 were around.

As Andy said there is a diversity of opinions and some hold to their favorites like a much loved child. Whatever you decide on you have made a start and should not be afraid to experiment and make changes later.

Don’t wait hoping for perfection, get out and enjoy the activity.

73
Ron
VK3AFW


#17

MM0FMF has nailed it for me with the antennas and trialing in your local recreation area or field.

I’ve owned both and both are great for their respective price points and it the age old adage of you pays yours money…

I have a KX3 and it’s head and shoulders above the Yeasu, as I would expect for something nearly twice the money. But Is it worth it - I’d buy mine again and wish I hadn’t wasted money by buying the FT817 first, so a cautionary tale here. There are so many happy users and stalwarts of the Yeasu out there so they can’t all be wrong. No one can tell you how to spend your money it depends on how serious you want to be. My KX3 would double as a base rig - it’s that good. Good luck :wink:


#18

It does indeed :slight_smile:
I use mine to chase at home; no amp - the noise is so bad that the weak link is hearing the incoming signal.

73,
Rod


#19

Do you use it in conjunction with HDSDR?

http://www.hdsdr.de/

I have found it makes a big difference when the KX3 is used as an SDR. I am able to resolve signals so weak that they would never hear me if I didn’t turn on the linear, and some of the noise where I live is pretty bad.


#20

I asked the same question a year or two ago. And I still use the linked SOTA dipoles.

It isn’t much of a fag changing bands. Its not as though you’re centre support is an immovable object.

No tuner, less to go wrong and less to carry / pack.