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• dBi or dBd?
• Should I take into account the theoretical gain of an antenna in free space or over real ground?
• Does the height of the antenna affect its performance?
• Do metal guys influence the performance of an antenna?
• Can rain or icing affect antenna performance?
• How should VSWR be interpreted: the lower, the better?
• Why my analyzer meter doesn't give the same reading at a certain time of day or night?
• Is a 1:1 balun necessary for DXBeam HF antennas?
• Is a grease advisable during the assembly of an antenna?
• Can I mount a DXBeam antenna on a tower that uses the "Hazer Tram" type of system?
• Is the assembly of a DXBeam antenna complicated?
• How and by whom are manufactured DXBeam antennas?
• How much time is needed for the fabrication of an antenna?
• How do I order a DXBeam antenna?
• What must I do if the parcel appears to be damaged at delivery?
• What are the warranty conditions?
• Who are the users of DXBeam antennas?
dBi or dBd?
With specifications quoted in dBi, dBd, gain in free space or above ground, the beginner can be puzzled ... Exploiting this confusion, certain manufacturers claim antenna gains beyond belief (see gain vs boom length). DXBeam decides to specify antenna gain in dBi (gain in decibels when compared to an isotropic radiator). Should forward gain be given in dBd (gain in decibels when compared to a dipole), 2.15 dB should be added to find the respective dBi value (i.e. 4 dBd = 6.15 dBi). Buyers beware, there is no "magic antenna"!
Should I take into account the theoretical gain of an antenna in free space or over real ground?
Both approaches are of interest:
1/ If you wish to compare the performance (forward gain, F/B ratio, etc.) of a given antenna to another, then modelling it in free space will generally give you the desired data.
2/ If you wish to evaluate the angle of radiation and F/B ratio depending of your antenna height, then modelling it over real ground will give you the desired radiation patterns. An elevation plot is generated for each antenna above ground level.
All simulations have been realized (and sometimes cross-checked) using MMANA, AO or EZNEC programs. Tests showed excellent correlation with the computer-simulated models.
Does the height of the antenna affect its performance
Many factors affect the antenna performance such as height above ground or surrounding objects, and could be responsible for moving its resonant frequency/feed impedance. You may experience difficulty on 40 or 30 meters if your antenna is not mounted at a reasonable height: all aerials were tested at 14.5 meters (47.6 ft) above ground with no other antennas in the vicinity. Although the DXBeam antennas do not require tuning, some fine adjustments may be made on the radiator element tips to move the resonant frequency. Any attempt to modify the other dimensions in order to improve the VSWR is not recommended.
Do metal guys influence the performance of an antenna?
Wire mast guys, because of their unforeseeable resonant effects, can influence considerably the radiation pattern of antennas. When directional antennas are installed at the top of the mast such guys can necessarily induce stray current which result in an absorption effect and a degradation of the radiation lobes. The current induced in the guy system can reach a maximum of twice the wavelength. If it is desired to limit this it would be necessary to insert insulators into the guys at least every half wavelength for the frequency worked. If, for example,the mast carries antennas for 28MHz it would be necessary to insert insulators at least every 5 metres. (See Resonance of Guys by F5AD - french language)
However, a far simpler solution exists: Use non-metallic guys such as those supplied by DX AVENUE.
Can rain or icing affect antenna performance?
Rain, but particularly freezing rain, often detunes antennas. They are vulnerable to icing which has the same effect as electrically lengthening their elements with a negative impact on both the gain and F/B characteristics of directional antennas. They can become temporarily unusable due to high VSWR. Resign yourself to your fate until the ice melts!
How should VSWR be interpreted: the lower, the better?
The question of VSWR is one that is too often misunderstood. Contrary to popular belief, a low VSWR doesn’t mean your antenna is radiating properly (e.g., a dummy load). Be skeptical if the VSWR remains low and flat across the band (except for wide-band design like log-periodic antennas). A high VSWR shows that the matching between the antenna and its feed is incorrect but it is not always a sign of degradation in efficiency. Also it does not indicate that the feeder will radiate. The important thing is to ensure that the antenna is working perfectly, e.g. with on-air performance evaluation on both transmit and receive.
Why my analyzer meter doesn't give the same reading at a certain time of day or night?
Don’t rely blindly on your antenna analyzer: these devices use broadband detectors and are sensitive to RF fields which can cause erroneous readings. On several occasions, measurement anomalies have been observed on 160, 80 or 40m during nocturnal periods. The culprits are high-power broadcast stations capable of overloading the analyzer’s front end. If in doubt, use your transmitter through an SWR meter to double check the accuracy of your measurements.
Is a 1:1 balun necessary for DXBeam HF antennas?
DXBeam antennas does not require any balun. To avoid having stray current on the braid of a coaxial cable (often the cause of RF and/or TVI/BCI), you can make your own choke balun with coaxial cable. Explanations are provided with each antenna assembly instructions. (See: The Use of Baluns and the Symmetry of Antennas, by F5AD - french language).
Is a grease advisable during the assembly of an antenna?
Not only is it advisable, but also DX AVENUE supplies it with your antenna. You will be supplied with an aluminum contact grease for all the tube connections, in order to avoid binding, corrosion and the formation of aluminum oxide, as also copper conductive grease for steel/aluminum contacts. Note: Pre-assembled elements are already made with these greases and so you will have no need to disassemble them to add grease.
Can I mount a DXBeam antenna on a tower that uses the "Hazer Tram" type of system?
If you have this type of tower, then attention must be paid to the type of antenna you are purchasing. Some models of the DXBeam’s have elements that are close to the boom-to-mast mounting plate which is the balance point of the antenna and are not suitable. In some cases however, it is possible to move the mounting plate, but do note that a counter weight would have to be added to the boom thus maintaining balance at the new mounting point. Failure to observe this precaution would result in excessive rotator bearing wear and possible seizure of the antenna rotation.
Is the assembly of a DXBeam antenna complicated?
Not at all. All our antennas are delivered pre-assembled and checked. Unlike other brands, the installation of a DXBeam antenna does not require wracking of brains or a hundred pieces delivered in a bundle with (sometimes) a parts list. All the hardware is pre-installed and the various tubes which cannot be assembled because of transportation are marked with specific labeling. An instruction leaflet (French or English) is included with each antenna. Obviously this minute attention to detail in our workshops has a cost, but is also a measure of our commitment (and of peace of mind for the purchaser).
How and by whom are manufactured DXBeam antennas?
DXBeam antennas are exclusively produced in France by F2DX (DX Avenue). Despite the presence of modern machines for making meticulous work, the antennas are made one by one in a traditional way and no steps are outsourced.
How much time is needed for the fabrication of an antenna?
When the model is in stock it will be shown on our website. If not, DXBeam antennas are normally available in 1 to 2 months. Don't wait to the last minute to order ; the timing depends on the model, but also on our order book (especially for 50Mhz antennas if you wish to benefit from the good DX openings in June/July) ; furthermore you only pay a deposit when you order.
How do I order a DXBeam antenna?
Ordering an antenna is a little different from that of the other material sold by DXavenue.com for at least two reasons: The method of payment and the means of delivery.
The ordering process therefore consists of completing a proforma (request for a quotation) clarifying the model of antenna and possible options required (Balun). On receipt of your request, DX AVENUE will calculate the cost of transport by courrier (usually UPS or Fedex) and will send you a quotation in PDF format. If you accept the quotation, you are then required to make a 30% deposit of the total amount (with the right to withdraw within a 7 day cooling off period) and the balance of the total just before your antenna is despatched to you. We only accept the following methods of payment: Bank Transfer in Euros (there is the possibility that there will be an additional charge for countries outside the EU - that will be notified to you on the quotation), bank draft in Euros (limited to Metropolitan France and its overseas Departments and Territories) cash postal draft (limited to Metropolitan France, her overseas Departments, Monaco and Andorra). Payment by PayPal (PayPal account or Bank Credit Card) is also possible on condition that you accept at your charge the costs of PayPal which are currently 3.4% (this will be made clear on the quotation).
What must I do if the parcel appears to be damaged at delivery?
If you receive a parcel which seems clearly to have been damaged during transportation, you must ask the driver to wait whilst you open it to check the contents. If after inspection, you determine that the goods are damaged, you must note this as precisely as possible on the courrier's delivery note and then send an e-mail to DX AVENUE within 48 hours. You also have the option to refuse the parcel.
What are the warranty conditions?
We warrant our antennas against manufacturing defects for TWO YEARS from the date of shipment. During this period, DXBeam may repair or replace parts as deemed necessary. To obtain warranty, antennas must have been handled, installed and used under normal working conditions in accordance with DXBeam’s recommendations and specifications. Warranty will not be honored if product has been modified without our permission.
Who are the users of DXBeam antennas?
Radioamateurs throughout the whole world amongst whom are well known DXers and Contesters whose results are high in the lists of antennas used. They haven't all supplied us with photos, but you can already have sight by consulting the photos published with each model of antenna or in our photo gallery.
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