How do the Bushcomm BBA-100, SWC-100 & FD-100 broadband HF dipole antennas actually operate? What technology is used?
These antennas work using a Travelling Wave design. Bushcomm engineers also add a little of our own twist on this technology to improve both VSWR response & overall performance
How can I improve my short range 20 ~200 km HF transmission - NVIS (Near Vertical Incidence Skywave) antenna configurations?
Communications over a distance of 20-200 KM can be a little tricky via HF. Unfortuntely this range is in the middle of a grey zone, whereby it is too far for "Groundwave" comms, but any "Skywave" signal is more or less bouncing straight over the top of any receiving station.
Without going too deep into technical details, the easiest way to improve short distance (NVIS) comms on a vehicle is to run a long-ish whip (say 2.5-4M), and tie it back over the vehicle. Its likely you may have seen military vehicles in the media with this type of configuration. The other important tip is to stick to frequencies betweem 2 and 8 Mhz
I should mention that Bushcomm offer quality 2.7M stainless steel whips which are compatible with most popular mobile tuner manufacturers such as Barrett, Codan & Icom.
As for base station antenna NVIS configurations, you may wish to look at an inverted Vee installation. Not only will this normally improve your shorter distance performance, it has the added benefit of giving you a relatively omnidirectional radiation pattern from a dipole .
There is also plenty of info on the net relating to NVIS communications if you wish to delve deeper.
Coaxial Tuners Vs Random length wire tuners - What is better?
Like most things there are pros and cons for both styles of HF Tuners/Couplers.
Inline Coaxial Tuners.
Pros: Generally lower cost, easy installation
Cons: Will normally require a 4:1 balun to be fitted directly to the antenna radiating elements, can be quite lossy, particulary with longer coaxial runs
Popular manufacturers: LDG, MFJ
Longwire (Outdoor) style Tuners.
Pros: Generally improved performance, better tuning stability
Cons: Higher cost, needs to be installed close to the feed point of the antenna, shorter lifespan if mounted outdoors in the weather
Popular Manufacturers: SGC
Does fitting a longer whip to my mobile auto-tune antenna improve performance?
Yes, absolutely. Even adding an extra 1M to a standard 1.6M whip length, can make a noticable improvement in on air performance.
Be careful not to make the overall length your whip any longer than a 1/4 wavelength of your highest frequency, or you may find that the tuner may not tune up on the higher frequencies. This is particulary relevent for screwdriver antennas antennas such as the Codan 9350.
For normal land mobile use of frequencies between say 2-15 Mhz, the recommendation is to not go over about 4M in length.