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Author Topic: 2 meter base antenna  (Read 3252 times)
KI4UGS
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Posts: 6




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« on: November 10, 2009, 06:01:41 PM »

I have a 2 meter mobile radio.I am ready to set up a 2 meter base radio inside the house .Would like to do it right the first time.What would you suggest
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KI4SDY
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Posts: 1452




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« Reply #1 on: November 10, 2009, 06:25:40 PM »

One of the best and most inexpensive 2 meter base antennas is the Arrow J pole 2 meter/70cm antenna. For $39.00 you get an indestructible antenna with almost 3db gain. It is light weight and portable. Small enough to install in the attic if necessary.

I have mine mounted on a lightweight aluminum pole stuck in a vent pipe on the roof with a U bolt assembly keeping it in place. I painted it flat black with $.99 spray paint to make it invisible. It is feed with 25' of RG8U. It works great! I never have to use more than 5 watts. It has been through three major hurricanes with no problem.

Check the eHam.net review on this antenna. You cannot beat it for the small price and durability!
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WB5JEO
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Posts: 805




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« Reply #2 on: November 10, 2009, 06:34:11 PM »

I assume the antenna will be outdoors. You can use a 1L/4 or 5L/8 mobile antenna just fine by using a 90-degree piece of bend metal, an angle, drilled for whatever mount the mobile uses and for however you want to support it, "U" bolts to a mast, etc. Give it a proper ground plane. It is simply four tuned wire radials. You can attach them to the horizontal surface of the mounting bracket with small U bolts. Make them 1L/4, even if the radiator is 5L/8. You can bend them down to come away from the base at a 45-degree angle as a nicety. It the antenna has been taken out of mobile service, recheck the trimmed length of the radiator. It may tune just a bit differently than it does on the car. If you have a long run to the antenna, you might want to change from the RG58 or RG8X that is often used with mobile antennas and go to something with less loss, which is more of an issue with VHF than with HF.
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KW6LA
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Posts: 91




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« Reply #3 on: November 10, 2009, 07:14:36 PM »

Hustler-G6-144B / Omni Directional Fixed Station
  Frequency Range: 143-149 MHz
Gain: 6 dB
Maximum Power: 1 KW FM
Bandwidth: 6 MHz
VSWR: <1.5:1 @ resonance
Impedance: 50 ohms  

See reviews 5 for 5 on E-Ham !
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WB6BYU
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Posts: 13242




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« Reply #4 on: November 10, 2009, 08:52:23 PM »

The antenna is NOT the first question.

First, what is your goal for operation?  What modes?  How
far do you want to be able to talk?

If you are using 2m SSB you want a horizontally polarized
antenna, but for 2m FM you want vertical polarization.

If your interest is talking on local repeaters, it doesn't
take much of an antenna to do that.  If you want to work
through a specific repeater 50 miles away, it may require
a beam antenna of some sort.  (If you are trying to bounce
signals off the moon it will take a LOT bigger antenna!)


Next, the most important factor in performance of a VHF
station is antenna height.  How high can you put up
your antenna?  Do you have a mast, tower, or tall tree
you can use?  If your house is already on a hill that
helps a lot, but if it is down in the bottom of a gully
height becomes even more important.  For normal, local
chatting on 2m using simplex or repeaters, a height of
12 to 20' is usually adequate, but if you want more
range than that you may want to put up a tower to 50'
or more.  For shorter heights a TV mast attached to
the side of the house may be adequate (though they
need be guyed if they extend too far above the attachment
point.)  Even a 12' 2x2 is a good start if it gets your
antenna up above the edge of the roofline where it
isn't blocked by the clutter and wiring of the house
itself.

Next consider your feedline.  You can use RG-58 for
short lengths in uncritical applications, but I'd
consider RG-213 as a minimum for anything over 40' or
so to keep the losses low.  Yes, there are lower loss
feedlines available, and for weak signal work (like
2m SSB or other modes) they may be worthwhile.  A good
rule of thumb might be to keep the coax loss to less
than 1dB for weak signal modes or 1.5 to 2dB for FM -
the losses for each coax type are specified in loss per
100' (or similar), so you can calculate the line loss
for different types if you know how long the coax will
be to your antenna.  VK1OD has a handy line loss
calculator here:

http://www.vk1od.net/calc/tl/tllc.php


Finally you get to the choice of antenna.  You'll hear
a lot of claims for gain, but many of them are bogus.
For vertically polarized omnidirectional antennas (as
would commonly be used for FM) you can make a pretty
good estimate of the gain of a 2m vertical antenna by
its length:  anything with a radiator close to 3' long
will be equivalent to a dipole - this includes a ground
plane, J-pole, Ringo, and a 5/8 wave whip over horizontal
radials.  (The 5/8 wave whip gets WORSE when the radials
slope downwards due to the higher angle of radiation.)
If it is about the size of a dipole, it will act about
like a dipole.  The gain will, in fact, be 0dB over a
dipole, though marketing folks hate to see that number
so invent lots of other expressions to make it look
better.  There's nothing wrong with a dipole, however,
or with an antenna that works about the same as one.
They are reasonably sized and work fine for most
purposes.

The next step up in 2m omnidirectional gain gives 3dB
of gain over a dipole, which is equivalent to doubling
your power.  This requires a radiator about 8' long.
The Ringo Ranger, IsoPole, and many other antennas fall
in this range.  The taller antenna may require a stronger
support.  With such an antenna you should see an
improvement in signal strength of roughly 1/4 of the
scale on your S-meter.  (It varies from one radio to
the next, but that's what I've typically measured on
an FM mobile rig.)  It will help you when your signal
is marginal, but not if you are already full scale, or
if you can't hear the repeater at all with a dipole.
There are lots of commercial antennas available in this
range of sizes to choose from.

The next step to a 6dBd gain antenna requires 20' of
vertical space on 2m.  This might be a commercial
antenna like a Station Master, or 4 dipoles stacked
vertically on a common mast.  This is equivalent to
four times the radiated power of a dipole.  The support
mast has to be a lot stronger, and it is critical to
get it plumb, as it only takes a 10 degree tilt to make
it worse than a dipole in some directions.  Antennas
that big are often used at repeater sites, but are not
as common at home stations.  You can get the same amount
of gain out of a simple yagi or quad:  though those
require a rotator (unless you are just interested in
a specific direction) it isn't hard to extend the beam
to even more gain that would be practical for an omni
antenna.  (If you want to work VHF DX you'll probably
end up with several beams on a tall tower, but that
isn't necessarily where you want to start.)

Based on our experience, a 3' to 8' antenna mounted at
least level with the edge of the roof (and above the
peak of the roof if possible) provides simplex coverage
out to 20 to 30 miles, depending on terrain, and should
hit most of the repeaters in the area (depending on their
height above ground, etc.) using 5 to 25 watts or so.
This is adequate for most hams on 2m.  If you have a
specific repeater that is 60 miles away, you may need
more height and/or a beam pointed at it.  Or you might
not - it is hard to know until you try it from your
location.

A good approach is to ask some of the local hams how
much power and how high of an antenna they need to hit
the local repeaters.  In some cases a small improvement
in antenna height can make the difference in a repeater
of interest, while in other cases there is no need for
anything bigger than a rubber duckie because the local
repeater is the only one anyone can hit anyway.
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K9KJM
Member

Posts: 2415




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« Reply #5 on: November 10, 2009, 11:22:18 PM »

Many very good points brought out by WB6BYU.

I would add that Times LMR 400 is the coax feedline of choice by the pros, AND it is less expensive than quality RG 213 (RG 213 is the coax of choice for the HF bands)

LMR 400 is good for up to 75 or so feet of length for most applications at VHF. Don't scrimp on the coax feedline! When you decide just where to  put the antenna, Try to route the coax so as little length is needed as possible. Keep it short for less loss.
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N1DVJ
Member

Posts: 474




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« Reply #6 on: November 11, 2009, 06:16:05 AM »

Well, first thing is to get the signal from inside to outside.  You want cheap?  

    http://www.radioshack.com/product/index.jsp?productId=2103641

It's easily tuned to 2M.

Better yet, make your own out of an SO-239 chassis mount connector and some brazing rods.  You'd be surprised at how well it works.

Or you could go with this:

    http://www.radioshack.com/product/index.jsp?productId=2103160

More expensive, but transmits on a lot of bands.  The Non-Radio Shack version even had an optional whip for 10M use.

But if you want to stay cheap, there are plans all over the net for various 2M antennas.  Coaxial coliners made from coax and put in a piece of plastic pipe.  Or J-Poles.  And you can make a J-Pole out of copper pipe (but that can be a bit of effort and expense) or you could make it out of TV Twinlead and just put it in a piece of PVC waterpipe strapped to a ventpipe.

Feed it with good coax, whatever you do.  

And don't be distracted by the people who say "This is best" or that something "won't be as good" kind of thing.  Just get out there and do it, even if it's crap.  You can always upgrade later, and that's even part of the fun of doing it.  If you listen to the people arguing about what is best, you'll quickly fall into the trap of not doing anything until you decide (maybe in a few years) of what really is the best...

Heck, just take a long piece of coax and trim 19" of it so it exposes the center conductor, and then clamp on a ferrite from RS 19" down on the cable and hang it from the edge of the roof to get on the air today!

Mike
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WB6BYU
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Posts: 13242




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« Reply #7 on: November 11, 2009, 07:29:10 AM »

Mike has a good point:

"Perfection is the enemy of good."

Start with a reasonable installation that fits your budget.
Don't worry about having "the best" or "the perfect" antenna,
just what works for you.

I've seen too many hams who go for the antenna with the
highest gain rating and the highest power mobile rig for
bragging rights, then end up just chatting on the local
repeater which only requires a watt or two and a bent
coathanger for an antenna.  Until you discover otherwise
(or if you are in an isolated rural area) there likely
is no need on FM for more than 25 watts and a simple
antenna at rooftop height.  You'll have to find out
what the local repeater and simplex activity is in your
area and plan accordingly, of course, but in most cases
a modest installation is quite adequate.
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N5LRZ
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Posts: 0




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« Reply #8 on: November 11, 2009, 08:52:23 AM »

Item 1> a good commmercial grade regulated power supply of at least 40 amps or higher.  I know its overkill BUT as your station builds you will have available current reserve to take care of additional radios and equipment.  Memo, avoid swithching power supplies completely no matter how attractive their price may appear and go directly to one of those big, heavy, pre switching, regulated power supplies.  The Commercial grade regulated non switching power supplies are well worth every dime you spend.

Item 2> get a 2nd radio for the house and leave one in the vehicle.  That way you dont have all that bother of connecting all those wires every time you go mobile and back to base.

Item 3> SWR Meter designed for VHF.  An ordinary HF SWR meter will work on VHF if you turn down the adjust to zero before you start and slowly work it up.  BUT the results will only be approx values as the meter was not designed for VHF.  I suggest you get a VHF and UHF meter designed for VHF and UHF use.  Specificly one of those cross needle models that allows you to see forward power, referse power and SWR all at the same time PLUS most do not require a set adjustment of any kind.  

Item 4> COAX...very important the kind of coax that is used.  Get a copy of the ARRL Antenna Book (see public library) and look up the loss tables under the transmission line section.  Note which coax types offer the LOWEST loss for the VHF/UHF band and try to get thist type of coax if at all possible.  

Item 5> Antenna--go to the various amateur radio supply sites on the net and check out their VHF antenna selection.  I strongly urge a beam antenna, yagi design, having at the minimum 13 to 15 elemements minimum.  Such and antenna in general runs less than 200 dollars and sometimes much less--I got my 13 elemement beam for just under 100 on sale.  Search around.

Item 6> rotor--fortunately VHF beams are not very big or heave and those inexpensive under 100 buck 3 or 4 wire TV antenna rotors will be OK. If possible try to get one with some kind of a locking function to hold the antenna in place and keep it from turning in the wind.

Item 7> accessory an antenna switch, standard VHF quality OK.

So lets get the total here....

Radio for base use dual VHF/UHF.....prices vary

Commercial power supply......  at least 250 possibly more

Meter---shop around but about 150 bucks

Coax---price depends on quality and lengh

Rotor---usually just under 100 bucks

Antennas (2/VHF and UHF) allow for about 175 each.

Antenna switch -- Under 100 most of the time.

ONE final thing.  I extremely and urgently state that you should NOT NOT NOT use a battery in the home as a main power supply.  Battery power is OK for an emergency but for NORMAL daily use spend the $$$$$ and invest in that GOOD non switching regulated commercial grade power supply (IF you take good care of it that power supply will last you an entire lifetime for a one time investment).


Did I hear someone mention a vertical omnidirectional antenna??  They are in fact OK if all you want is a utility gain antenna and do not mind not being able to have the versitility of a good beam.  When attempting to hit a marginal at best repeater the beam will give you that little extra edge that an omni vertical will not provide height of antennas being equal.  BUT in complete honesty the vertical omni does not have a blind side that the beam does either.  Best case install a half way decent vertical with utility gain for close repeaters and the beam to target repeaters.
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N5LRZ
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Posts: 0




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« Reply #9 on: November 11, 2009, 08:56:37 AM »

LOL see under rotors the word 'heave'... do not know why I put that word there.  A senior moment probably.  Ignore heave. Smiley  

Heaving is not a good thing Wink
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N1DVJ
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Posts: 474




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« Reply #10 on: November 11, 2009, 12:53:37 PM »

I have to say the previous posters long post is EXACTLY the kind of post I was saying not to listen to.  The 'must be perfect' kind of advice.  Where people who don't know the difference between the 'best too' and the 'best tool for the job'.

I'm sure the original posted wanted to hear that he'd have to spend $1000 just to get on the air!

Hey, USE A BATTERY!  No one will die.  Yeah, it's not optimum, but it gets you on the air.  You can pick up decent 3-state intelligent chargers for about $35 that will do a great job on a 7ah Sealed LeadAcid.  But do buy a regular car or motorcycle battery.  Get a battery DESIGNED to 'go low' like for wheelchairs or kids ridable toys.  A decent 4ah battery be about $35.  What's nice about the battery is you can buy more than one and rotate them.  In a winter storm you can even have a respectable amount of emergency power for your rig.  (And don't forget to make a small DC cable to any scanner you may have.  It's always nice to have a scanner to let you know what's going on during a winter blizard with a power outage.)

Hey, GET A SWITCHER!  But check it out carefully.  I picked up a 25A switcher that is silent on some bands.  But if you do, be sure to check it out.

Just get SOMETHING outside for your antenna.  Worry about upgrade and making it perfect to please the perfectionist later, and do that piece by piece.
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N5LRZ
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« Reply #11 on: November 11, 2009, 02:23:58 PM »

Re DVJ...

In reality I calculated very quickly the initial cost of the home base to be closer to approx $1,200.00 plus sales tax of course.  

Had the original poster asked about HF he would have gotten a reply that would have had an initial cost of close to 4 or 5 thousand dollars IF he recycled the power supply to run his HF Radio.  IF he got one too small because he was cheap then you can add another 250 to 300 dollars on top of that.

I have always stated and will always state that if you do Ameteur Radio 'Proper and Right' anyone living paycheck to paycheck should never ever consider Amateur Radio as their hobby.  IT like Golf is an entertainment activity for the those with fairly large quanties of disposable income.

And 1000 dollars for a 2 meter station is incredibly cheap compared to the right and proper HF Station that could conceivably cost you, depending on your primariy activity, in excess of 10 thousand for the radio alone, NOT to mention the 4 thousand tower and 3 thousand beam plus that big rotor costing in EXCESS of 1000 dollars alone.  Never mind that the max amp is going to run you in excess of 3500 dollars for a well made amp (not a piece of crap).

Ham radio is like the game of Golf in that it was never meant for poor people.  Pure GD FACT, Not fiction.
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K9KJM
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Posts: 2415




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« Reply #12 on: November 11, 2009, 11:34:56 PM »

Yes, The (WRONGHEADED) Advice to not use a battery power supply is just pure B.S.

More and more public safety radio systems are now using just that type of power supply: A deep cycle battery of some sort with a fully automatic charger to power radio equipment that MUST work under all conditions. AND is indoors, Usually in a small building that is not vented.

Using a battery to power your radio has many advantages, And few disadvantages.   A marine deep cycle type battery is just over 50 bucks brand new, A 10 amp fully automatic charger is around 40 dollars. So less than 100 bucks sets you up with a power supply that will still work in the event of a commercial power failure.
(Although an automotive type battery could work in a pinch, For only a few dollars more you can buy a brand new true deep cycle type that is MUCH better suited for radio operation.) Even better is the AGM sealed type battery, Sometimes available good used cheap, but they are kind of expensive brand new.

The only time the dreaded "outgas" could be a problem is If/when there is a commercial power failure and the battery is "fast" charging when commercial power is restored (Or you are charging the battery with a generator) Under those conditions, Do provide some kind of ventilation, and keep sparks away from the battery.
Also, The battery usually will last between 5 to 9 or so years, So plan to eventually replace it.
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K9KJM
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Posts: 2415




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« Reply #13 on: November 11, 2009, 11:46:19 PM »

I also saw a suggestion that you buy a VSWR meter.

Unless you find one super cheap at a swapfest, Or classified ad, Forget buying one and just have a local ham stop by with a decent one to check your system to make sure all is OK. You NEVER leave a VSWR meter inline all the time anyhow. (Check commercial repeaters, Police, Fire, Ambulance, Cellphone tower sites, etc etc. How many VSWR meters do you find inline all the time? NONE!  

At VHF and UHF, The less junk you have installed inline from the radio to the antenna, The better. The average ham really does not need to own an expensive meter. If there are questions about antenna performance, Have your ham buddy with a good quality meter stop by. Buy him a bag of donuts or something for his trouble.
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N1DVJ
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Posts: 474




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« Reply #14 on: November 12, 2009, 03:30:54 AM »

Hmm, perhaps I was a bit strong.  N5LRZ's advice isn't wrong, it's just so 'narrow focus' that it doesn't apply to any but a small portion of the community.  If his focus overlaps with your interest, then fine.

But, even if I had an unlimited budget, I personal wouldn't want the kind of station he describes.  In my mind, thats the 'rich boy toy' station.  The kind of setup the spoiled rich set up, try it, then decide it's not for them.  Like one of my frat brothers in college.  Decides he would like a motorcycle, so daddy buys him a top of the line touring bike.  I'll bet he didn't drive the thing 500 miles in 4 years.

Again, that's not to say that kind of advice is wrong, it's just not what I'm into and I don't think it's 'genarally applicable'.

Me?  I've built what I have up over the years,  sometimes stepping back, then forward in a different direction.  Because you don't really know what you want until you 'move' in that direction, then realize what the direction really is.  

So, take his advice if you want to, but take it with more than just a grain of salt.  File it away in your mind with a lot of the other advice, then decide what YOU want to do.
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