Thursday, March 28, 2019

Considering Portable Operation

Portable operation

Portable operation is probably the best option when one has a postage stamp back garden and located only 7m A.S.L. From a VHF point of view, the obvious choice is a high location with the use of a 20ft telescopic "light weight" mast secured with a drive on mast support. This is not the ideal height for 2 or 4 metre operation but will suffice for most operations on 70cms and frequencies above and is quite manageable for a solo operation. 

H.F. operation requires careful consideration of antenna types for use in the field especially if the activity is going to be a solo operation . Vertical antennas would be the first option and these may come in several forms. If there are trees around it is possible to suport a variety of antennas. Unfortunately the west of Ireland does not have an abundance of trees in useful portable locations so other options are considered.

The Kite Antenna

The Kite antenna is an excellent choice as it is possible to hoist up a quarter wave antenna for top-band using a Sled 24 Kite. A set of 1/4 wave elements for 160, 80 and 40 metres would not take up an excessive amount of room. Even a random length of wire with an ATU gives reasonable results. A kite is quite manageable by one person alone but the obvious precautions of ensuring that there is a bleed system to remove static from the antenna. A bleed resistor of at least 1 M-Ohm would be required.

Naturally one should ensure that the kite is flown well away from power lines or obstacles.

A typical set up would be as shown:
There are a couple of choices of kite but the Power Sled 24 available from Premier Kites is lightweight and very portable with no breakable parts. The Sled Kite is very stable in flight and doesn't dart around the sky if there is a sudden gust. The Sled 36 is much bigger and capable of lifting heavier wire antennas but can be difficult to reel in if there is any appreciable wind speed. The Cody Kite or the box kite are also very good alternatives and are generally quite stable.

The Fibreglass Pole

A 10 or 12 metre Fibreglass telescopic pole is a good basis for a portable antenna system. It is possible to wind a 1/4 wave length of wire in the form of a wide spaced coil around the pole to form a vertical which is fed at the bottom.

The Fibreglass Pole may be used to support an Inverted-Vee antenna

A sloping dipole is also possible using the Fibreglass pole:

SOTA Beams produce a three band dipole that may be used as a sloper or an Inverted-Vee. The different bands are selected by adding links in each leg.

The Windcamp Dipole

This is a small and simple lightweight dipole with a 1:1 balun at the centre.

Tuning is achieved by unwinding the antenna to points indicated by clour coded shrink wrap on the wire.

This is easily stowed in a back pack with a length of feeder and possibly a lightweight SWR Bridge.

The Buddipole

The Buddipole is a professionally constructed portable antenna for 40 to 2m which has found a huge popularity worldwide. The exceptionally good quality and care of details make this antenna an ideal companion for vacations and other portable activities. The transport length of the dipole is only 56cm, with a weight of only 900 g nearly any pole is suitable for carrying it. A coaxial cable (380cm) with PL and BNC connectors is supplied, equipped with a choke on the antenna side. Power rating: 250W.

All items can be stowed in a carrying bag which makes it easy to transport.

All of the contents piece together to make a coil loaded dipole making it easy to tune to the various bands of choice. Coils are available for 80 and 60 metres and spare parts are available to extend the capabilities of the kit.

The buddipole is pictured above with all components in place. The coils in each leg may be tuned by moving links up and down the length of the coil to resonate on the desired frequency as shown below:

HF Equipment for Portable Use

The transceiver is a matter of choice and can be either QRP operated from a 12 volt battery of perhaps something capable of higher power.

The personal preference that would cover all requirements and operate from a larger car battery would be the FT817 and a Tokyo High power Linear amplifier.

The FT817 ND QRP Transceiver covering HF bands from 1.8 to 30 MHz plus 6m, 2m, and 70cms. This tranceiver has an internal power pack but it is better to have a 7 AH lead acid gel battery to ensure adequate operating time. The LDG tuner is powered by AA cells and a great addition to the kit.

To increase the output for more serious portable activity the Tokyo HF50L can be added in line to give 50 watts P.E.P. output.  Sadly the Tokyo Hy-Power company closed in 2013 and these linear amplifiers rarely appear on the market. Ebay occasionally comes up trumps but they are often very expensive.

Both the FT817ND and Linear amplifier are an excellent combination for both voice and data communications.

The addition of the a Signalink USB driven by a portable notebook will be used to complete the set up.

Driven by a suitable data modes program, the signalink USB is a versatile system and additional programs such as JT65, FT8 and the WSPR suites, the best of QRP data modes may be enjoyed.

Of course one could go one better and employ an ARD 9000 Digital voice modem to the system. Whilst this is not hugely popular there is still some operation in this area and the results can be impressive at QRP levels.

With all the equipment in place it will be necessary to make up a Go Kit to contain the whole station in one easily deployable case. Watch this space for the next part of the project. A few large heavy duty plastic cases, a similar size to the TW7000 case, had been purchased from Maplin Electronics before they closed in Galway

In the mean time a shack in a case is already available in the form of the Transworld TW7000 which is an ex-govt HF transceiver operating from both mains and portable power. The power supply and ATU are built into the system. This is however not the most portable system as it is fairly heavy.

Everything required for a portable operation is in the case including a rapid deployable length of wire with a throw weight easily tuned for the HF bands. The power supply will auto sense the mains voltage. The Aut0-ATU will tune any random wire length. This is an excellent system for communication on all HF bands and capable of 125 watts P.E.P. output. There is also an ALE system built in but probably better with a pre-tuned multi-band antenna for the bands required.

Hopefully some reasonable weather for the fortcoming year will make portable operation more attractive.