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Frequently Asked Questions Q. What can I expect for reception with antennas like these? A. Because of the different ways these antennas can be built this is a big question, a 2 bay without a reflector is good for urban areas where signals are strong. 4 bays are a good choice for suburban areas and adding a reflector can make it into a decent rural antenna especially when used with a decent quality pre-amp. 8 bays are really needed only for fringe reception areas, both the 4 and 8 bays have some decent VHF-HI reception capabilities especially if properly sized. A good place to go for signal strength predictions for your area is tvfool.com using that web site you can get a good idea for your location. Local obstructions like buildings and hills or antennas mounted indoors usually mean that you have to add a reflector or go up a size to get good reception. Generally a 2 bay mounted outside will perform as well or better than a 4 bay mounted inside. In areas where signals are low a quality pre-amp will also give you the same effect as going with a bigger antenna but it's best to go larger with the antenna first. Q. I went to tvfool.com and got a plot of my location so now what? A In rural areas when mounted outdoors it's no uncommon for a curved reflector M4 to get UHF reception down into the single NM numbers on the tvfool chart. With a quality pre-amp reception in the negative range is very possible. In urban/suburban areas the signal becomes more unpredictable due to increases in man made noise and obstructions in the signal path that tvfool can't predict. Indoor installations are almost impossible to predict due to the great variation in building construction. Typical attic installations with a standard wood and shingle roof can cut the signal by around 20db so you will have to subtract 20db from the tvfool NM prediction to be in the ball park. In most markets a properly sized 4 bay with a large reflector will get VHF-hi channels and UHF at about the same strength since the VHF-hi stations are usually a bit stronger which makes up for the smaller gain of the antenna on VHF-HI. Q. Do I need a reflector on my antenna? A. A reflector will almost double the reception power of an M2, M4 or M8 2,4 or 8 bay but comes at a cost of reception mainly in 1 direction and increased wind loading. A reflector 32" wide or larger will make an even larger increase in VHF-hi reception. Reflectors are also helpful in narrowing the beam width of the antenna which can help cut down on interference with other TV stations. Q Angled, Curved or Flat reflector ? A. Angled or curved reflectors used with swept forward whiskers will give more gain and a narrower beam width on UHF. Curved reflectors have a more consistent gain curve than angled. Flat reflectors have a wider beam width with less gain and wider spacings with swept back whiskers can give an even wider beam which can be handy for receiving stations off axis without rotating the antenna. My reflector mount kits are set-up for either curved or flat reflectors. Q. Which is better the long cross-over or short cross-over? A. Both work fine, computer modeling shows very very small gains with the short twist on some channels but the twist must be done precisely to get this slight gain. The long twist is easier to do and more forgiving to mistakes in spacings and take slightly less wire. Q. Which size whisker and bay spacing should I use? A. The best plan is to size the antenna based on your most desired and/or hardest to get stations. Generally any size M4 4 Bay with a reflector will work fine on all the UHF channels but the smaller size will be better on the upper channels and larger sizes on lower UHF the difference is only a db or 2. The same is true for VHF-hi but the differences are more noticeable because the differences in gain are larger changing as much as 6db from one size to another. A 10" x 9 1/2" is best on ch's 7 - 9 and 9 1/2" x 9" best on ch's 9 -11 and a 9" x 8 1/2" is best on ch's 11 - 13. An M8 8 Bay follows the same pattern but the M2 2 bay doesn't work nearly as well on VHF-hi no matter what size. An exception to VHF gain on the M4 4 Bay is when using the wider 14" - 15" reflector spacings which gives a wider gain curve on VHF-hi at the expense of slightly less VHF-HI gain a narrower gain curve on UHF. Q. Will these antennas pick up VHF-Lo stations Channels 2 - 6 or FM radio? A. These antennas are no where tuned for VHF-LO or FM radio, you may get reception of these signals but they have to be quite strong. For the most part the attenuation of FM radio stations are a good thing since it helps cut down on interference from those stations, especially when using an amp. Q. Can the reflector be directly mounted to the mast. A. Yes it can the only thing that need to be isolated from the reflector is the phase lines and whiskers. Q. Do I have to strip the rubber/plastic coating off of the wire I want to use or can I just strip the connection points? A. If you are using my drawings they are calculated for bare wire. Leaving the coating on the wire will
change the velocity factor of the wire (speed that the signal travels
through the wire) That will change the point where the whisker elements
are in phase at a given frequency as compared to bare wire. It will
work with the coating on but the frequency response of the antenna will
be skewed downward because it makes the phase lines appear longer to
the TV signal. To add to that depending on the materials surrounding
the wire the velocity factor will be different for each material and
even more skewed when it gets wet. |
