20/30/40m trapped dipole

One of the aims of SOTA is to walk in the nature.

So, a light backpack it’s a must !

One the first opportunity I bought a Montain Topper Radio, MTR-3B wich is a 3 band HF (20/30/40 m ), which weights 124 gr.

Because the MTR doesn’t have an ATU or a SWR meter and I don’t want to carry anyone of those, I decided to make an antenna that fit the objective: Been light!

The search for such antenna endup with the trapped dipole or the linked dipole.

Well…I would have quick band changing: The trapped dipole is the way to go!

Searching for antenna traps was an easy one: Sotabeams pico traps!

When they arrived it’s clear that they deliver. Easy to build and tune. Very light weight: 5 gr each!

So a traped dipole was made. On one sunny sunday João, CT7ABE helped to make all measurements at the local public park. After that, all the welding was redone and a liquid rubber coating was applied.

Another set of tests confirm: The antenna was ready to go!

I used a 6m fishing pole but the last meter (tip) wasn’t used because it’s too thin and doesn’t stand the weight.

The 10.45m is an arbitrary dimension, recognising that the 45 degree angle at the  apex wouldn’t be achieved

The details are as follow:



Trapped dipole (final)






Trap (top)


Trap (side view)



Trap (bottom)



Center dipole



Center dipole



Center dipole

Portugal (CT) National SOTA Day – 2016 Notices

On 1st April 2016 we celebrate five years of SOTA program in Portugal. :heart_eyes:

So, we invite all amateur radio operators to take part in those celebrations named National SOTA Day 2016, which will take place on April 2, 2016 (Saturday).
The essence of the celebrations is to have multiple summit activations all over the country on this day.

The activity aims to promote the SOTA program and allow sensitize the amateur radio community for this kind of healthy and funny activity.

Although there are certificates to the participants (activators and chasers), the National SOAT Day – 2016, as well as the SOTA program, it’s not a contest.

It will be a “SOTA party on-the-air” and therefore all amateur radio operators are invited.
All Portuguese clubs were invited to join the activity.

All amateur radio operators who are Activators are specially invited and encouraged to bring other hams or prospective hams for activation, enabling others to experience a SOTA activation.

It is suggested that the activations should take place:
• From 09.00 and 18.30 (local time) on April 2, 2016;
• Using their own call sign (/ p);
• Using the simplest possible equipment (QRP in most cases, including portable radios V / UHF);
• In SOTA summits with the highest possible score:
• In the amateur’s radio operator area;
• In any CT/CU/CT3 summit.

The KISS concept (simplicity, simplicity, simplicity …) will be used throughout the activity: The only rule is to comply with SOTA rules and having fun!

As explained before, there will be certificates to the participants who activate a summit (by SOTA rules) or have a QSO with one activator/summit on that day (chasers or SWL). Other than that, they should send photos or videos of their SOTA activity to CTsotaday@gmail.com

This will be a great opportunity to chasers abroad Portugal. :smiley:

Please feel free to ask any questions to the email.

In behalf of National SOTA day organization

Vy 73


CT National SOTA Day logo


Activator certificate

VHF SOTA Antenna – Slim Jim


I made a couple SOTA activations and there were other stations asking for the 2 m band.
So, I carried my mobile (5/8λ Diamond) a pair of times.

I use it with the Yaesu FT-817ND to do some CW, SSB and FM QSOs , instead of using the rubber duck.

But carrying such antenna was painful and uncomfortable. 😦

So, I search for a more suitable antenna to be used in a summit.

It should be light and foldable. Some gain is also a desirable feature.

I chose the slim jim antenna.
From several sites I made one.

The SWR are better than 1,3:1 at first try. So, it’s ok!

I don’t have equipment to conclude what are the gain, fire angle, etc.

So, I test it against the 5/8 λ mobile one.

The pratical test results are overwhelming: Even at home it shows more performance than the Diamond mobile antenna.
On summits it proof to be THE antenna for SOTA!
One could always use a yagi made of tape measure. I’ve done that. But again, portability…

And, in a windy day it’s difficult to keep the elements straight!…

SLIM JIM 2 m- The construction

This simple antenna can be used inside by supporting from string, nylon cord or used outside by hanging or supported from a fishing pole, etc

Easily made from 1,6 m of 300 Ω ribbon cable (junk box…)


Just follow the drawings…

First : weld the copper on top and bottom and strip about 1 cm, at 10 cm from the bottom.


Second: Cut 2 cm of the wires in one side of the ribbon, at 49 cm from the bottom


Third: make a hole for antenna suspension and weld the centre and braid of the coax (almost done…)


Finish details are :

Shrinkable sleeve cover the welded wires.
A hole was made in the ribbon. In this hole passes a nylon yarn which, in turn, uses a plastic hook for antenna suspension



(of one of the conductors 49 cm from the bottom)

Shrinkable sleeve prevent infiltrations and led to a mechanical reinforcement.

The mechanical reinforcement consisted of the use of tips of the plastic cable ties which were used to hold the RG-58 in the bottom of the antenna.



Shrinkable sleeve cover the welded wires at the bottom to cover the ribbon, including the welds of the RG-58 to the ribbon.

In addition to the visible plastic clamp, there is another tying the RG-58 and tape.


In the fields

Using the antenna at SOTA ref CT/ES-004 Monte Manique

6 to 7 turns of RG-58 form an air core RF choke.

Portability is redone every time you mount the antenna… 🙂

ballun field



Adele singing on CU/SM-002, Pico da Barrosa, S. Miguel Island, Azores !!!!

30JAN2016 PM

After the activation of CU/SM-001, Pico da Vara, I decide to change the initial plan and head to Pico da Barrosa (CU/SM-002), making a small detour for a work meeting. And to buy some alkaline batteries. On those last QSOs at CU/SM-001 the battery voltage became dangerously low…
The KX-1 tx started drifting…

This is an easy walk (550 m), the weather is fresh but otherwise ok.

I took a while to choose the best location to install the antenna.

After all, it was easy to install the antenna and… Let’s fire the radio on the 40 m band!

And Adele start singing very loud on the headphone “Hello from the other side…”.This come with a mix of morse signals…
Well…Change to 30m. Adele still singing loud, very loud!
20 m band. The morse signal seems to increased.

Then the commercials started. I became aware of what were the best deals at Lagoa city… 😦

I thought to move to another location within the AZ but my time was short by now and maybe the plane do not wait for a delayed SOTA op…

So, 20 m will be “the band”…

I logged 14 QSOs in less than 30 min, taking only the powerful signals because of the local radio QRM.
Even though it was difficult to have readable signals…
Then the batteries (including the cheap alkalines ones) went down and my power (guess) was well under 1 w!

All QSOs made after 1543, starting with CT7AGT, were QRPp.

Nevertheless I manage to do a few more QSO, connecting the LiPo (external) and the alkaline batteries (internal) at the same time.
For instance, a QSO was logged with N4EX which was 4700 km away. Even if we know how effective are the QRP CW signals, it still amazed me!

I apologize to all chasers who contact me or tried to do so, because either I can’t hear them or my power is low.

On the next few days listen to Adele could drive me crazy!…


The lake view from a viewpoint on the ascent road – Lagoa do Fogo (Lake of Fire)


The summit view from a viewpoint on the ascent road


Close view of the summit


West view


This a landscape from a summit !!!! Lagoa do Fogo (Lake of Fire)


“Populated” summit


View to the North shoreline


The endless road (across the top)


Op position just before turning on the KX-1…To listen to Adele!

S. Miguel Island, Azores – CU/SM-001 Pico da Vara


The highest point in S. Miguel Isl (1104 m, 3622 ft).

A Natura 2000 site and a Special Protected Area: Beautiful!

A walking distance of  +1h45min to reach Pico da Vara, in a wet and cold weather.
The temperature drop to 6 C while climbing. A light wind was blowing and when exposed the temperature feel like 2 or 3 C.

The first third of the track was on a track over the peatbogs, with several small wood bridges across the Plateau of Graminhais.

Then comes the muddy track with some wooden steps on the most difficult places.

All the time I just saw 2 couples on the mountain.

In some places along the track it’s possible to have a view of north and south shoreline just by turning the head.

The wind at the trig was very cold and all the ground was wet. Because of luggage constrains (low cost airplane on the trip to S. Miguel) I hadn’t my full gear. So I could not sit me all the time!

The start was rough. I had very strong QRM (7 MHz, 1145Z) from EA5UF that were using too much bandwith (more than 5 KHz)…He his CQing over and over. A true alligator…

First QSO was with my neighbour in Lisbon Joao CT7ABE on 40m. Propagation was not that good, so I switched to 30 m and after 4 QSO I switch again for the 20 m band.
16 QSOs and to cover the distance to m

ainland (Lisbon) my signal traveled at least 1 500 Km!

The endfed performed well but the battery started to show low voltage. I forgot that I’m not using the MTR but the KX-1, which were the original plans … 11,5 V is too short for the KX-1!
That was a mistake that could cost me this activation!

After 45min at the summity I start the descent. The weather improved lightly and views were better than before.

My rented Smart was waiting for me to take me to the next summit, CU/SM-002 Pico da Barrosa, just after a work meeting and a stop at a local shop to buy alkaline batteries.

Enjoy the photos!

Pedro, CU3HF/p




CU SM 001 Map_fotos

Map from Azores trails


Trail start


Peatbogs track (East view)


Peatbogs track (West view)


Trails junction


landmark: Air France Crash 1949


View to Lombas (Povoação)


Landmark: Portugues Air Fore crash – 1943


North shore (Maia)


South Shore – Povoação


Wooden steps


Other summits (to East)


The view(and weather) from the summit


SOTA Shack! 🙂


Antenna farm at the summit


Ready to depart


On the descent – View to Southeast


On the descent – View to East


Explanation about this protected area


Explanation about this protected area