THE MULTI- BAND ANTENNA
Lightweight & Strong
Cost Effective Solutions
The HF Spectrum (2 > 30MHz) has many communication users around the world including commercial/marine and others, most of the end users use wideband/broadband antennas which are very inefficient the tilted folded dipole being one version, the radiation losses on this type of wideband HF antenna are huge due to the matching network part of the antenna being a mega load resistor and impedance matching transformer, however, to increase RF power radiation requires the use of resonant antennas on the frequency to be used rather than using a wideband unit. Many radio/antenna suppliers always seem to recommend a 2 to 30MHz antenna which is 30 mtrs long and requires 2 mast fixing points, in many cases this is not convenient especially in sandy conditions, also the whole spectrum of 2 to 30MHz is never used by commercial operators and there are many reasons for this.
Our technical notes and propagation book is available free, this shows how to get the most out of your equipment
Radio Amateurs use the whole spectrum but that is because they want to communicate Worldwide and achieve vast distances, the commercial user does not want to do this, the user needs to communicate IN country only and so a few thousand kilometres is sufficient.
The commercial user needs 2 or 3 daytime and 2 or 3 nightime frequencies probably between 3 to 16MHz as radio propagation changes between daylight and night time due to the reflection angle of the earths layers.
Diagrams showing and explaining how signal distances and frequencies change from day to nightime
There is a solution and RFCOMMS have been successful in this field for the past decade in using a newly designed matching transformer that has negligible insertion losses (1.3db) and can be resonant on many spot HF frequencies, just a single wire is used with a matching transformer. Several different impedance matching units have been developed for frequency ranges and power levels.
The matching unit does not contain any resistors or active components and is constructed using up to 3 special custom made ferrite cores wound with Mil Def 210 PTFE wire which is then housed in a UV protected enclosure and fully resin potted to protect it from the elements (IP68). The transmission line used is Kevlar based for strength and durability and is terminated with a UV protected insulator.
We can make a custom antenna offering a major increase on any wideband antenna using the above techniques, the length of the transmission line will depend on the lowest frequency that is required. Mounting is simple using very low cost installation items.
Tables show operating frequncies versus time of day
The units are VERY cost effective, small, lightweight and totally IP68 rated as they are resin filled. All external parts are Marine A4 Stainless and the kevlar wire has a breaking strain of 90 kgs, other transmission lines can be offered like Phosphor Bronze multi strand pre stretched @ 300kgs BS. Many other options can also be offered.
Power handling is 125 watts pep which suits most commercial HF transceivers and can handle ssb, (data, subject to lower power) ALE etc. Higher power units also available on request.
Ultra low cost
Free samples available
Available as just a matching unit or as a complete antenna built to your frequencies.
Commercial users only.