Wideband vs standard VHF rubber ducky performance

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n9jth

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Which portable radio antenna would work better (transmit and receive) at a 155 MHz frequency?:

1. A "standard" rubber ducky antenna with a stated bandwidth of 151-159 MHz.

2. A "wideband" rubber ducky antenna with a stated bandwidth of 136-174 MHz.

Stated another way, I'm wondering what compromises, if any, are introduced by the use of a wideband antenna when the use frequency is near the center of the antenna's design range.

For this hypothetical, I'm not concerned about performance at other frequencies. I only care about 155 MHz.
 

teufler

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I would say the narrow band width will be the best for transmitting. The wide band compromises to achieve the band width. Probably the narrow band width will be a slightly taller antenna. Case in point, I have a couple of Larsen Kool Duck antennas. They are about 1" taller than the normal came with the radio antennas. One for for 146, ham band, the other was 155. Both receive well but the transmit function, the one for the band area that I am working has a better swr, and radiates more effective power. I have several ht's that are "wide band" units. There antennas work but when using a field strength meter, the narrow band antenna works better.
 

Dog

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Which ever one has the best SWR at the frequency you will be using. If you are only using the one frequency it won't matter they will perform the exact same if they have the same SWR.
 

jparks29

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Which ever one has the best SWR at the frequency you will be using. If you are only using the one frequency it won't matter they will perform the exact same if they have the same SWR.
False.

SWR ≠ radiation pattern

You can have good SWR with a tuned wet noodle, doesn't mean the RF is going where you need it to go.

A full 19" 1/4 wave whip on VHF and a 7" base load 1/4 wave on VHF tuned to the same frequency will have the same RF output/pattern? NOPE!
 

Dog

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False.

SWR ≠ radiation pattern

You can have good SWR with a tuned wet noodle, doesn't mean the RF is going where you need it to go.

A full 19" 1/4 wave whip on VHF and a 7" base load 1/4 wave on VHF tuned to the same frequency will have the same RF output/pattern? NOPE!
They asked about 2 rubber duckies with different advertised bandwidths. Not "A full 19" 1/4 wave whip on VHF and a 7" base load 1/4 wave on VHF tuned to the same frequency"
 

jparks29

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They asked about 2 rubber duckies with different advertised bandwidths. Not "A full 19" 1/4 wave whip on VHF and a 7" base load 1/4 wave on VHF tuned to the same frequency"
The 'rubber duckies' are different for a reason...... They WILL have different characteristics, even if tuned to the same frequency with the same SWR...

They even make *gasp* 5/8 wave rubber duckies.... So saying that 'they will perform the exact same if they have the same SWR' is false.

I will say it again.. Having the same SWR does not mean the same performance...
 

Dog

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I will say again. As far as I know from their description they are the same antenna with different advertised bandwidths.

There isn't enough information to make an accurate prediction from the description of said 2 antennas.

Really SWR doesn't equal performance or pattern? You must be joking...

Have a good day.
 

jparks29

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I will say again. As far as I know from their description they are the same antenna with different advertised bandwidths.

There isn't enough information to make an accurate prediction from the description of said 2 antennas.

Really SWR doesn't equal performance or pattern? You must be joking...

Have a good day.
If they have a different advertised bandwidth, then they are physically different. Electrical length isn't always physical length. If you understood how portable or HT antennas are made (or any antenna, for that matter), you'd know about matching networks, coils, etc. wideband antennas usually use a coil matching network to work across its stated frequency.....

Yeah, SWR doesn't solely dictate a radiation pattern or 'performance'.... Dummy loads are tunable to have low SWR, doesn't mean they actually put out a signal where you want it.. Likewise, different antennas WILL behave differently....

Please explain to me how the #%( SWR being the same means that both antennas will perform the same when they are OBVIOUSLY differently constructed electrically and physically....

You're saying that these two antennas, that have the same 'specs', same band, etc are going to be identical? Then why do they have SEPARATE MODELS? It's because they're designed to do different things and are not the same...






You're postulating that because they both have the same SWR they'll perform the same, that is patently FALSE....
 

prcguy

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Its common practice to introduce a lossy, usually restive component to widen the band width of an antenna and with everything else equal the lossy one will radiate less signal. I have some military vehicular whips that cover large frequency ranges and they have an atteunator at the input to provide a good match to the radio.

They only way to answer your question on which one is better would be to do a field strength test on each one but that also has its problems. If a particular antenna has more gain than another but its match is really bad, some hand helds will back down their transmitter power and that would corrupt a field strength test.

To get the bottom line on comparing antennas you have to use a test jig that simulates the size and shape of a small hand held radio and use a transmit source with an atteunator or isolator in the feedline path then a distant pick up antenna to a calibrated receiver, spectrum analyzer, power meter or similar.

I have all the parts and equipment to run accurate tests between rubber duckies if you want to drop by with your antennas....
prcguy
 

majoco

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prcguy said:
Its common practice to introduce a lossy, usually restive component to widen the band width of an antenna
I have one of those - flat VSWR from 500kHz to 30MHz - it's called a dummy load - poor reception though..... :)
 

mmckenna

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Which portable radio antenna would work better (transmit and receive) at a 155 MHz frequency?:

1. A "standard" rubber ducky antenna with a stated bandwidth of 151-159 MHz.

2. A "wideband" rubber ducky antenna with a stated bandwidth of 136-174 MHz.
I periodically check the radio antennas as they come through my office.
Recently I had a couple of PD radios with the "high gain" VHF antennas, a few with the "standard" antennas and a few with stubby antennas.
My own "shop" radio has the wide band antenna on it.
All antennas are the Kenwood offered models.

A while back I had someone drop off a bunch of old radios in my office that they were getting rid of. One of them was an old beat up TK-290 hand held. Since it already had the guts removed, I took it apart and soldered a length of coax onto the antenna jack and had it come out the bottom of the radio chassis. Works well for simulating real world use. I can hook it up to the analyzer and see how the antenna is doing.

The Kenwood wide band VHF antenna is truly wide band. It showed 2.0:1 SWR across the band from about 145 to about 165MHz. Lowest SWR was at about 158MHz at 1.8:1.

I know, SWR not the best estimate tool for antenna performance.

The high gain Kenwood VHF whips had lower SWR but a much narrower bandwidth. Good for 150-160MHz, outside that range the SWR went up quickly.

The standard VHF whip and the stubby VHF whips were nearly identical SWR wise.

Of course SWR doesn't tell you how well the antenna is working. As stated, a 50Ω dummy load shows a near perfect SWR across the band....

Trying out the different antennas on the same radio, it was hard to tell the difference between the wide band, standard and high gain antennas. The Kenwood's have a "maintenance" mode where it will show you receive signal strength in dB. Hardly any difference between those 3 antennas, but that has a lot to do with the system I was testing it with.
The stubby was worse, as expected, but the officers like them when working plain clothes as it's easier to hide the radio.

I'd agree, don't get too hung up on portable antennas. Skip the cute stubby antennas, but find one that's tuned properly for where you plan on transmitting. If you are using a reputable brand antenna, and your expectations are realistic, you'll probably be OK.
In your shoes, I'd say go with the narrow bandwidth antenna if it's where you need it.
 

lmrtek

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I've sold the wide band versions on rare occasions and they are generally longer and more expensive as well

The only steady customer I have for the wide bands is the forestry service.

Stick with stock ducks and you can't go wrong
 
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