A place to talk about everything Radio and Scanning


Postby Chris P » Tue Jan 01, 2019 2:07 pm

waxmax wrote:
Chris P wrote:A band specific such as the scanmaster airmaster will be better than a wideband "white stick" If you are only interested in the civil airband .Have you tried a simple vertical dipole made from two 600mm lengths of stiff wire connected to a coax lead with chocbloc I found this performed better than any of the commercially available civil airband antennas and as it will be fitted in the loft no weather proofing is required . Mine was suspended from the roof timbers with the coax feed held at right angles for about 1m using tape or string . You can progress to a more sturdy version using copper tube once you have found the "sweet spot" in the loft . Moving a VHF antenna around by only a few feet can improve signals considerably .

My dipole gives me s9 signals from the chedburgh Nats site which is some 30 miles south east of me and carries Essex radar allowing me to monitor inbound traffic (both aircraft and Ground station) into Stansted . The aircraft can be received down to about 500 ft on approach but I am unable to hear the ground stations ( stansed tower or ground )

The other advantage is that this sort of homebrew antenna costs almost nothing to make .
If you want a wideband antenna try a bowtie made from two 800 mm pieces of stiff wire ( I use seperated 2.5mm twin and earth cable) each piece bent into a Vshape with the open end being about 340mm and the coax connected to the centre again with choc bloc, the outer to the lower V and the core to the upper V the elements should be vertical and the coax should feed horizontally away from the centre for a wavelength or so if possible

How far is stansted from you?

Stansted is approx 47 miles as the crow flies . there are a few hills in the way and the curvature of the earth prevents a line of sight path
Regards Chris aka G8FFF nipper or tazmin88
Chris P
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Postby radiostationx » Tue Jan 01, 2019 2:57 pm

Agree with Chris P, making your own antennas can be challenging but fun at the same time.
The Bow-Tie was a firm favourite in the 1960s and it later evolved into the bi-cone we sometimes see with airband fans.
Speaker wire/red/black rig power lead dipoles are good performers as they have an impedance at the feedpoint of around 72 ish ohms and as Chris says its a good move to run the feeder at 90 degrees to the feedpoint for about half a metre.
Coaxial double bazooka dipoles are easy to make if you are accurate with the cutting.

The d-777 is quite tall, around 6ft I think and from memory its a 5/8 wave loaded co-linear, which looks like a variant born out of the x-50 2m/7cm base station ant, diamond antennas are usually beautifully made with high quality fittings which is an important factor if mounting outside.

Getting full bars isnt the end game if you are using a micro handheld like the icom r-2 , often these can be over driven by an s-9 signal and their small raspy half watt speakers sound awful trying to cope. With these receivers a decent extension speaker with the right frequency response (tailored for voice) can make a huge difference to listening experience.
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