lunes, 3 de mayo de 2021

Portable radio setup

 As the age goes ahead, portable setup optimization becomes a must. Rig, batteries, antenna, mast,.. all must be adapted to minimum weight and size if your plan includes hiking more than a few kilometres. Of course, the rest of the equipment must pass by the same process. Water, food, raincoat, spare clothes, emergency medical kit, mobile phone, etc. are continuosly being examined/changed to get the best results with the less possible weight.

At this moment -and leaving apart VHF/UHF activations- I managed to design and carry this CW equipment, which I consider basic and light enough. All items divided in 3 parts: equipment, antenna, and antenna support. Let's see all them!

Equipment: All of it fits in a small hard box of 17,5 x 12,5 x 6,5 cm.

All parts -except the antenna and pole- are carried inside this small bag:

  1. 20/30/40m QRP CW-only SW-3B transceiver. The last I've bought, gives you the three most commonly used bands with a weight of only 180g. For more flexible activations I will grab the heavier but much better Elecraft KX2 in a bigger box.
  2. 11.1v 2500mAh 5C LiPo battery (147g). This is the smallest useful size to carry up to 3 hours of operation without recharging it. The 10 w power output of the KX2 is obviously more demanding than the SW-3Bs 5w. 
  3. Earphones: In case I use the Elecraft KX2, I carry a model with integrated microphone and using the vox or PTT button, in case I would want to make some SSB contacts (very unlikely).
  4. CW keyer: Now the Hands Free Nanokeyer, made with a 3D printer. You can find all details at As an alternative I use the excellent Portable Paddles made by Andrés EA3PP. Both of them leave my hands free to write down the log or operate the transceiver. 
  5. An Anderson Powerpole adapter fits any battery I have, as this year -at last- I standardized all my rigs and batteries to this connectors. 
  6. BNC male to female 90deg adapter.

In adition to this, I carry a small waterproof notepad and a pencil inside the rucksack. Plans to upgrade to digital logging are being evaluated, and I have already carried on some short VHF activations using the free excellent android app VK-Port-a-log.

Don't also forget the rest of components of the Ten Essentials! small knife, medical kit, etc.

Antenna: I usually carry several types of antenna: a Norcal Doublet , a recently made end fed half wave trapped dipole for 20, 30 and 40 m bands or a non-resonant 10,6m long endfed dipole. 

In my opinion, the Norcal is a very light antenna and has being largely tested for a good performance on all bands from 10 m to 40 m. Unfortunately, you must use it with an antenna tuner and its weight would be added to the total. On the other hand, the EFHW dipole doesn't need it at all, but the operation position cannot be chosen as well as with the Norcal. You must sacrifice some operability in order to -again- optimize the weight you will carry. Anyway, both antennas are carried inside the ruckshack, using self-made wire winders.

 Antenna support: Being portable means that you must also carry some system to put the antenna high enough on the field. As you cannot expect being trees available in all the places you want to transmit, the obvious choice is carrying a some kind of pole. 

In my case, and if the path to walk is not too long, I bring a 10 m pole which gives me a good height and better isolation of the antenna from the ground characteristics. However, it is not at all the lightest thing you can use. If  I would carry it for more than 1 hour, my choice will be a 7.2 m Chinese fishing rod (found on an on-line chinese store). It doesn't seem to be very tough, but it is very light and quite cheap (about 9€ shipping included. 

For raising the pole at the summit, I use 3  3mm thick polypropylene guy ropes and 3 aluminium pegs, or some velcro strips of different lengths if some kind of support is available to be attached to.

Finally, and if I -rarely- planned some V/UHF activity to be made, I would carry the smallest walky-talkie I have, covering 2 m and 70 cm bands, analog & digital (DMR Brandmeister). That us the Alinco DJ-MD5 with a bigger antenna than standard (43 cm long) or the fiberglass boom 3 elements yagi Blandiblu (home made too) if the activation site would be near some populated area. Otherwise, I will be able to make S2S QSOs only. But up to date, the V/UHF items together make more weight than the HF ones, so sometimes I am quite reluctant to put them into the backpack... 

I wish some of these ideas would be useful to you, have a nice day and portable radio activity!

73, Mikel EA2CW

miércoles, 22 de julio de 2020

Filtro pasabanda 2m


Uno de los problemas que nos encontramos al hacer activaciones desde el monte en VHF es la presencia, cada vez mas numerosa, de emisoras y repetidores de V y UHF en las cimas. La potencia de transmisión de estas torres provocan a menudo el bloqueo de nuestros receptores. Estos, especiamente los mas modernos, muchas veces adolecen de la falta de un filtrado pasa-banda suficiente. Así, nos podemos encontrar que, aun siendo escuchados, somos incapaces de recibir a nuestros interlocutores. El nivel de ruido de RF es muy alto o, por contra, nuestro receptor parece haber fallecido.
Para intentar mitigar el problema, recientemente adquirí un filtro pasabanda de la marca SOTABeams, especialmente diseñado para su uso en portable. Su tamaño y peso son muy adecuados como complemento a un talkie típico de VHF. También hay que señalar que no se conmuta en emisión/recepción, sino que permanece continuamente insertado.

Sus características mas reseñables son (del fabricante):
Peso: 25 gramos
Tamaño: 4,5 x 2 x 1,8 cm 
Potencia máxima en emisión: 5 w FM
Paso de banda: 144-146 MHz
Atenuación en la banda de paso: 3 dB
Atenuación en frequencias "dañinas":
    155 MHz +- 25dB
    FM broadcast band >70dB
    Air band > 50 dB

Una vez recibido, se realizaron las pruebas de campo desde dos de los montes mas afectados por "contaminación" de RF de la zona: Sollube y Oiz.
Previamente se comprobó la atenuación de inserción en transmisión que se corresponde con las especificadas por del fabricante. Con una potencia sobre carga ficticia de 4 w, la salida tras la inserción del filtro era de 2 w. (FM, 145.500 MHz)

Para las pruebas se usaron los siguientes equipos: talkies Yaesu FT-60 (FM V/UHF 5 w ), Baofeng UV-5R y Alinco DJ-MD5 (FM/DMR V/UHF 5w max). También se usó un FT-817ND en VHF, como equipo "estandar" en activaciones, usando 5 watios y el conector BNC delantero. Con este último fué mas fácil apreciar las diferencias de señales e interferencias.

El filtro viene provisto de 2 conectores SMA hembra, por lo que hubo que utilizar los correspondientes adaptadores doble macho SMA y BNC hembra a SMA macho, dependiendo del equipo. Esto puede provocar las consiguientes pérdidas adicionales, que en el mejor de los casos suele rondar los 0,3 dB por conector.

Las antenas usadas fueron las de los propios equipos y una yagi de 4 elementos de VHF, esta conectada a los equipos mediante 5 metros de coaxial de RG-174 de buena calidad (att de 9,8 dB x 100m @ 100 MHz)

La situación de la posición de operación en ambas cumbres fué a menos de 100 metros de las estaciones emisoras comerciales, a fin de apreciar mejor el comportamiento del filtro en las situaciones mas desfavorables. En los dos montes de las pruebas hay también repetidores analógicos de la banda de 2 metros y de DMR en 70cm, que podrían afectar también a la recepción.

Las pruebas consistieron en la recepción de estaciones corresponsales alternando la inserción del filtro.Las estaciones contactadas fueron tanto en portable desde otros montes como estaciones fijas.
Volver a hacer hincapié en que los lugares elegidos lo fueron por sus condiciones excepcionalmente desfavorables, a efectos de comprobar la efectividad del filtro.

En resumen, las observaciones mas significativas podrían ser las siguientes:

- La recepción de señales mejoró significativamente al insertar el filtro. En muchos casos, la diferencia era de recibir a no recibir al corresponsal. En estos casos -la mayoría- fue imposible medir la atenuación efectiva de la señal.

- El fondo ruido del receptor disminuyó de forma drástica al insertar el filtro, tanto usando sus antenas como la yagi. Incluso era posible usar esta apuntando casi directamente a las fuentes de ruido.

- En algunas recepciones (en ambas cumbres) se solapaba a la señal del receptor, otra con un patrón de "cliqueo" de unos 50 Hz de origen desconocido, que disminuía pero no impedía la recepción.

En la mayoría de los casos el comportamiento de los distintos equipos en recepción fué muy similar, incluso en los de rango de modo y banda mas amplios, que podrían ser a priori mas susceptibles al bloqueo. 

Configuración Mt Sollube
 Por otro lado, como aspectos negativos cabría destacar:

- Dada la significativa pérdida de inserción del filtro (3 dB) y la potencia máxima permitida (5w), la potencia de salida efectiva está limitada a 2,5 w. Esto podría compensarse usando un pequeño lineal entre el filtro y la antena (con el consiguiente aumento del peso del propio lineal mas la batería para alimentarlo). 
Una solución alternativa sería usar antenas con ganancia (yagi, cúbica, etc.) que sin el uso del filtro sería impensable utilizar, ya que los problemas de bloqueo de los receptores se ven agravados al usarlas.

- Las dimensiones del filtro hacen que, dependiendo del modelo de talkie, no sea posible instalarlo directamente en la salida de antena, ya que tropieza con los mandos. Esto obligaría a usar un pequeño latiguillo o bien una serie de adaptadores que "alejen" el filtro de los botones.

Nota: Todo lo aquí expresado lo es a título personal y con fines meramente informativos. No tengo ninguna vinculación con el fabricante ni ningún interes comercial al respecto.

viernes, 10 de julio de 2020

"Blandiblu" 2m portable yagi antenna

Blandiblú ver 2 at Sollube, EA2/BI-033
The goal of the project was to make a light and portable antenna for the 144-146 MHz band.  The design of reference was the pretty IZ2UUF 100 gr. yagi, but I chose to make the elements of brass, to be able to solder them later. I don't like aluminium. Although this material can be lighter than brass, it's harder to work with. Finally, the antenna will be a 50 ohm 4 elements vertical yagi on a non-conductive boom.

So, here we go. I found some sort of 25 mm aluminium wire, teoretically covered with a thin copper layer, that later shown not to be able to be soldered at all. After the first try, the elements were so soft that they bent too easily. This was not the most appropiate material at all, and thus, the name of "blandiblú" comes from here (you can search its meaning on the web to find why).

Blandiblú ver. 1 with aluminium "proactive" elements

The boom, from the very beginning, was a 1 meter piece of a broken fishing rod, formerly used as SOTA mast. I have 3 of them, so more designs are to come for sure.
The elements, finally, were 4 x 1m length, 4mm outer diameter, 0.25mm thickness brass rods, which are available at local bricolage stores. They make a good compromise between weight and strength. 

The lengths and positions of the elements were brought from IZ2UUF website and are (all measures in mm):

1st director900660
2nd director840990

The most difficult parts of the antenna were two: the boom_to_mast adaptor and the feeding_point of the driven element. They were made with a 3D printer (this is the bad side of the design, as not everybody has easy access to one). The desing was made using Wings3D free software. Here they are:

boom to mast adapter

driven element feeder (1)

driven element feeder (2)

The 4 mm wide brass rod were drilled to allow 2 x 2mm diam x 10mm length screws, which will later connect the center conductor and the braid of the coaxial cable to each side of the driven element. I used a total of 6 meters of RG-174 from antena to rig. 

Driven element feeder

A short length of  the coaxial (+- 1m) is used to make a choke. This is made of several turns of the coaxial with a length of about 34,5 cm. The number of turns may vary depending of the diameter of the boom, just keep that length. Tape it later to the boom and drive the rest of the coaxial back until it falls behind the reflector. Keep it perpedicular to the driven element. A longer length of the same coaxial is then connected (4-5m) to the talkie or transceiver using SMA type connectors.

The elements "hang" on the boom, so they are not vertically aligned with it. The size of the feeder will give you the amount of deviation. Being of brass, I soldered small pieces of copper wire to set them in their positions. Be sure to mark in some way which side of the rod must go up. 

boom to mast and elements set details

Boom to mast, feeder and elements

The holes must be carefully made to mantain the same orientation along the boom. IZ2UUF gives a well explained procedure about how to make this right.

The antenna was first tested on tuesday from Sollube, SOTA EA2/BI-033, and the results were apparently good, making several long distance QSOs. Later this week I will try to use it from other "rf noisy summits" around my home.

Finally, this and other alternative designs were tested using free antenna design software MMANA-GAL. The results obtained are more or less coherent with the actual developement.

I hope all this would be useful to SOTA VHF adicts. See you on the air!

73, Mikel EA2CW