RE: re: yaesu antenna

First of all, I notice that ya'll are specifying "0" as the low-end
frequency you're interested in; it is impossible for any antenna to actually
receive down to 0 Hz with any significant signal output, and furthermore
there is virtually no signals to be received there anyway as even the ELF
band (3KHz min typ) is difficult to transmit usable signals on and is used
primarily by military submarines for DX infrequently.

 

Susan, I think you probably really mean 1300 MHz for the top end (not KHz),
which is the same as 1.3 GHz or 1300000 KHz.  If you're truly interested in
extremely wide frequency coverage, eg 1-1300 MHz, then expect relatively low
sensitivity which is highly variable across most of that range.  That is
because antennas provide the greatest output signal at the frequency of
their "resonance", which in turn is dependent upon their size.  The lower
the frequency, the larger the antenna.  Manufacturers sometimes specify the
frequency coverage of their antennas without providing the potential buyer
the difference in signal strength across that range (typically expressed in
"gain" decibels as compared to a standard, eg dbi, dbd, and/or SWR which
indirectly indicates performance).  This will nearly always be the case for
antennas intended for transmitting, which always make the "best" receiving
antennas.

 

However, since antennas designed only for receiving are intended for use
across a broad range of frequencies, there are design compromises employed
as compared to antennas used for both transmitting & receiving, most notably
the useful "gain" sensitivity, variability in "pattern", and expense.  Eg,
larger diameter elements, higher resistance metal, multiple differing length
elements and counter-poises, low roll-off traps, even resistors.  This
drives antenna costs up, but always means lower gain (sensitivity) as
compared to antennas used for both transmitting & receiving.

 

SO.what to do?  Here's what I recommend.

 

1)       First decide which bands are of greatest interest to you.  AM
broadcast?  Amateur Radio?  Shortwave broadcast?  Aviation?  FM broadcast?
Satellite?  Police/Fire?  Try to choose those that are located relatively
near each other in frequency.  There are plenty of places on the inet where
you can get lists of major users & applications vs frequencies, so Bing or
Google for that (try "frequency chart", "shortwave listening", etc).  Then,
number then 1 to n with your priority (with no dupe numbers!).  

2)       Now, look at your prioritized list and try to estimate how strong
you expect those signals to be in your area.  Are you interested in very
far-away transmitters ("DX") with relatively low transmitting power?  Those
would typically be AM broadcast stations in far-away cities, or HF shortwave
stations in far-away countries, or many amateur radio operators, or most
orbiting satellites, or emergency responders 150MHz-900MHz in other cities
or in hilly terrain.  Or, are you most interested in relatively local radio
transmissions where you would reasonably expect strong signals?  If the
former, you'll want a receiving antenna with adequate "gain" (measured in
DBi or DBd, eg 4.5 DBi) in the area of those frequencies of primary
interest.  If the latter, then gain isn't as important as other factors and
you may wish to favor gain in those other bands of lesser interest to
provide occasional exploring.  If you can affect such a "balance" of gain
between disparate frequency areas of interest for you, then this will serve
you particularly well with the VR-5000 because that radio is unfortunately
unusually susceptible to overload of it's "front end", which means that
strong signals that are not of interest will degrade your ability to hear
signals you are interested in.

3)       The next thing to consider is: "how much room do I have for the
antenna and where can I mount it?"  Be aware that the lower the frequency
response, the bigger the antenna.  I have antennas here at my place that are
200ft long, 100ft off the ground, and they are best beginning at 3.5 MHz
(although they are more than adequate for AM broadcast reception down to 0.5
MHz for those stations in nearby states because of the transmitting power of
those stations).  Even if you are primarily interested in emergency
responders, aviation, satellites, and VHF+ amateur radio, the antennas can
get large as you look for the ability to pick up very weak signals; eg, if
you want to listen to "moon bounce" "earth-moon-earth" conversations that
amateur radio operators are often doing, you'll need at least a 15 element
yagi antenna at the frequency of interest, which is highly directional thus
you'll need a rotator on a mast ala the TV antennas of olde.  Most
satellites require a directional yagi antenna of at least 3 elements to
receive, and must be movable so that you can track the satellite (or
International Space Station) as it passes overhead.  Some people live in
housing/apartment developments where there are covenant restrictions on
putting up antennas, and they may to look at antennas they can put into
their attics, along the eaves, camouflage, lay along the roof eaves
perimeter, disguise as "yard art", etc (see "stealth antennas" on the inet).

4)       Now, you have enough info to make a really good antenna selection.
Armed with that info, you can either evaluate the antenna specs yourself and
make a selection that will perform satisfactorily, or used by an "expert" to
recommend something for you.

 

I hope that doesn't seem over-whelming.  I think once you get into it, you
should find that the exercise will add immensely to the enjoyment of your
radio, as it will (1) expose you to the various types of communications that
are available for you to enjoy, (2) feel some pride in doing some of this
"mysterious stuff" yourself to get started, (3) learn to better recognize
antenna system limitations that explain why you're not getting specific
stations you may be interested in later.  Even only 1 hour invested into the
exercise will make a big difference in the end for you.

 

Cheers, Stephen W9SK

 

  _____  

From: [email protected] [mailto:[email protected]] On
Behalf Of Susan
Sent: Monday, July 12, 2010 8:50 AM
To: [email protected]
Subject: [YaesuVR-5000] re: yaesu antenna

 

  

Many thanks Paul I will give this one a try. As a matter of interest what do
you use between 0-500mhz? I am a newbie to all this as you can probably tell
and I had to choose the hardest rig to learn on.Suggestion most appreciated
though.





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