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Author Topic: Making a full length 2m antenna for a handheld.  (Read 7053 times)
LB5KE
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Posts: 141




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« on: November 09, 2011, 03:22:13 PM »

I want to make a full length antenna and replace the short stubbie antenna on my handheld. Should the antenna be a 1/4 wave length or 1/2 wave? At first i thought 1/4 w is correct, but that wouldn't work properly without a counterpoise, so i am wondering if they are use 1/2 wave shuntloading like a boat antenna?
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K7KBN
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Posts: 2760




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« Reply #1 on: November 09, 2011, 03:55:26 PM »

Typically, the user's body capacitance is figured into the mixture as the counterpoise.  For 2M, an actual wire counterpoise is a worthwhile addition (light gauge copper wire wrapped around the ground side of the antenna connector).  I usually put an ounce or so of weight on the free end to keep it reasonably straight.  In many cases, this "tiger tail" with the original HT antenna is a bigger improvement than a longer antenna.
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73
Pat K7KBN
CWO4 USNR Ret.
LB5KE
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Posts: 141




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« Reply #2 on: November 09, 2011, 04:03:12 PM »

Ant the tiger tail have to be 1/4 wave?
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WB6BYU
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Posts: 13016




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« Reply #3 on: November 09, 2011, 04:05:23 PM »

Either will work, depending on how you build it.

1/4 wave is the most common.  True, it should have radials, but the same is true for a rubber duck.
Generally the frame of the radio is used for the ground system, though it may be smaller than optimum.
You can use a quarter wave radial made from light, flexible wire hanging down from the ground side of
the antenna jack for a better system.  I have a couple and they work well, even without the hanging
wire radial.  Just connect the whip to the center pin of the coax connector - you may find a commercial
telescoping whip that works, though they tend to be more fragile than something like a piece of brass
brazing rod or piano wire.

1/2 wave is more awkward to use on an HT, because it is nearly a metre long, and requires some sort
of matching device.  But they perform very well - probably about the best of any omnidirectional
HT antenna that is practical to carry.   The matching network is often a parallel-tuned circuit
between the antenna and ground, with the feedpoint tapped about 1/5 of the way up from the
bottom.  (Requires experimentation.)  An L network will also work.
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WB6BYU
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Posts: 13016




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« Reply #4 on: November 09, 2011, 04:07:10 PM »

Quote from: LB5KE
Ant the tiger tail have to be 1/4 wave?

Yes, the radial wire is 1/4 wave (plus whatever you need to attach it to the antenna connector.)

I generally strip one end and make a loop to fit over the BNC connector, then put the antenna on
over it to hold it in place.  Then cut it to length.
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AA4HA
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Posts: 1377




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« Reply #5 on: November 10, 2011, 05:22:51 AM »

Back in my public safety days there was a point in time where we were using commercial grade 6 channel VHF Kenwood portables. It was convenient that there was a BNC antenna connection. At the local cop-shop I picked up a rubber duckie antenna that had an extendable whip above the short coil. It worked just the same as a rubber duckie during normal ops, on out of county mutual aid calls I could still get into the county repeater from 30 miles away and came in loud and clear.

I had two HT's, one in the 45 MHz band with a normal antenna that looked downright silly. I could get into the state police/ state EMA base stations with some success on that radio. The EMA system was a series of voting receivers and simulcast/or individually select-able transmitter sites and I could always hit one of them from that portable. The high band VHF (150-157 MHz) Kenwood with the hybrid antenna did give me a tactical edge.

Really I should have gone with a Pack-RT system that was a Motorola trunk mounted UHF-VHF cross band repeater that is tied into the VHF vehicle radio. The UHF power was limited to somewhere around 100 mW so you could not wander more than a few blocks from your vehicle.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K1CJS
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Posts: 5855




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« Reply #6 on: November 10, 2011, 06:38:17 AM »

Jorn,  Take a look at some of the websites for amateur radio equipment.  I bought a 19 inch "rubber ducky" type antenna (all it is is a 19 inch piece of rubber covered wire that is somewhat stiff) for my handheld.  It too has a BNC connector.  I also got a 19 inch piece of stranded 22 gauge wire to use as a tiger tail.  With a little bit of tinkering, I can capture that tiget tail between the shells of the male and female BNC connector, insuring a solid contact.  That one dipole style antenna did more to improve the sensitivity of my handheld than even a magnetic mount vehicle antenna did.

You're on the right track to maximizing the usefulness of your handheld!
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KB1LKR
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Posts: 1899




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« Reply #7 on: November 11, 2011, 09:28:30 AM »

Look at Pryme RD-98 SMA or RD-98-BNC / Comet SMA-24 or BNC-24 HT antennas: these are ~17" of springy/whippy, thinly insulated wire on a connector for 2m/70cm, essentially 1/4 [2m]- 3/4 [70cm] wave. Add another limp thin wire (w/ a weight on the end maybe) clamped/soldered/etc. tothe ground side of the SMA (or BNC) and lett it droop and you have a center fed 1/2 wave (or 3/2 on 70cm) antenna. No reason you couldn't build your own on a connector vs. buying and adding the tail.

For a half wave *end fed* whip the matching is probably a nuisance/pain, and at 2m it's tall, though at 70cm it would be reasonable in length still. Might be fun to try anyway though.
 
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WB6BYU
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Posts: 13016




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« Reply #8 on: November 11, 2011, 10:48:51 AM »

The AES HotRod was the first commercial 1/2 wave whip that I remember.  I think there are still
some versions being sold.  Look for one about 38" long, NOT 48" (that's a 5/8 wave, which
doesn't work as well.)
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LB5KE
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Posts: 141




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« Reply #9 on: November 14, 2011, 01:31:03 PM »

Thanks for all the good answares Smiley

Perhaps a little off topic. I have done a test. I have attach a full 1/4 wave antenna to my handheld and a 1/4 to the ground so in effect i have a dipole. There is a nice improvement compared to the rubber duck antenna. However connecting the same handheld  to my magnet antenna on top of the roof of my car the improvement is substantial. Shouldn't the dipole like antenna of the handheld perform equally well as 1/4 wave magnet antenna?
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K2YO
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Posts: 436




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« Reply #10 on: November 14, 2011, 01:51:17 PM »

"Shouldn't the dipole like antenna of the handheld perform equally well as 1/4 wave magnet antenna?"

I can think of a couple of reasons why the car mounted worked better;
1. It's higher in the air.
2. It has a much larger ground plane.
3. It doesn't have shielding from your body.

I would have to see your specific test case to know for sure. I want to also appaud you for getting out there and experimenting. That's the ham spirit!

Bernie
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N6AJR
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Posts: 9888




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« Reply #11 on: November 16, 2011, 03:05:33 PM »

If you are using  this mobile,taka  look at the MFj - 310 , It is a gizmo that you roll up in your car window and put your rubber duck on tha outtside of the car. it has a 7 foot cord that hooks to the radio.  it gets your antenna above the roof.
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WB6BYU
Member

Posts: 13016




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« Reply #12 on: November 16, 2011, 03:25:31 PM »

Quote from: LB5KE
...I have done a test. I have attach a full 1/4 wave antenna to my handheld and a 1/4 to the ground so in effect i have a dipole. There is a nice improvement compared to the rubber duck antenna. However connecting the same handheld  to my magnet antenna on top of the roof of my car the improvement is substantial. Shouldn't the dipole like antenna of the handheld perform equally well as 1/4 wave magnet antenna?


It might, and it might not.  Besides the responses already given, did you prune the length of the
antenna elements for best SWR?  Probably not, as it is difficult to get an accurate SWR reading
on an HT.  (It depends on how you hold it, etc.)

While I would expect roughly similar results, the height above ground and presence of your
body in the radiating field are probably the main items that cause a difference.

One thing you can do is to cut a new radial wire that is too long, and progressively shorten it
to find the optimum length based on received signal strength.
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AB7KT
Member

Posts: 155




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« Reply #13 on: November 17, 2011, 05:23:25 AM »

A few years ago I played around with these "tiger tails". They used to be commercially made and I bought one probably in the 1980s: I came across it a couple years ago. I always considered stuff like this to be a gimmick. However, I did a test where I drove around and worked one of my friends on 2 meters simplex where he would take the tiger tail on and off. The tiger tail made a huge difference in his signal.
I realize that if you think about this, this isn't some incredible breakthrough, but, actually trying things like this on the air are the only real way of evaluating it. I did that and was quite surprised at just how much difference it made.

So, I decided to make a few of them. I used a solder lug that was big enough to go over the HT's antenna connector. I then used a piece of shrink tubing over the end of the solder lug to make it look nice. This is how the commercial one was made.

IMO, this is a far better upgrade to your HT than a longer antenna. Although both a longer antenna and a tiger tail might be better still. You can determine that by trying it on the air.
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I thought you said this was a weak signal mode ? I HAVE a weak signal and he still didn't hear me.

FWIW: My callsign is AB8KT
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