Bas-kit NMO high frequency antenna

Canelo56

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Working now with the Larson Bas-kit antenna, to all you antenna wizards, please tell me what and how I need to bend or cut these antenna wires, very confusing to me how long do they have to be and the proper angle. I will have the COMPACtenna Scan- Can -III mounted on top of the Bas-Kit. My aim is high frequency signals , PD,FD,EMT, emergency services, public safety mainly , I am using LMR-400 coax , my radio is a Uniden 436.
 

mmckenna

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Working now with the Larson Bas-kit antenna, to all you antenna wizards, please tell me what and how I need to bend or cut these antenna wires, very confusing to me how long do they have to be and the proper angle. I will have the COMPACtenna Scan- Can -III mounted on top of the Bas-Kit. My aim is high frequency signals , PD,FD,EMT, emergency services, public safety mainly , I am using LMR-400 coax , my radio is a Uniden 436.
The ground radial elements (horizontal elements sticking out from the base) do NOT need to be cut. It does not hurt to have them too long, it will impact performance if they are too short.
They don't need to be angled down, either. If that antenna was mounted on the roof of a car, the ground plane would be flat. Angling the radials down can change the impedance that the antenna presents to the radio. That's not required for scanner use as the impedance of the antenna will be all over the place depending on the frequency.
 

Canelo56

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The ground radial elements (horizontal elements sticking out from the base) do NOT need to be cut. It does not hurt to have them too long, it will impact performance if they are too short.
They don't need to be angled down, either. If that antenna was mounted on the roof of a car, the ground plane would be flat. Angling the radials down can change the impedance that the antenna presents to the radio. That's not required for scanner use as the impedance of the antenna will be all over the place depending on the frequency.
Great , this will be on my roof.
 

mmckenna

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OK, yeah, just install the radials and tighten down the set screws. Make sure you waterproof the coax connection well.
 

prcguy

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On the COMPACtenna Scan series you need to bend the radials down at a 70 degree angle and they should be about 16" long for commercial/public service freqs or 19" for 2m/70cm amateur. That antenna has too much capacitance to the ground plane and the match on VHF will be high if the radials are horizontal or 90 degrees to the antenna.

See post 16 in this thread for what my base adapter looks like with radials at a steep angle down for this antenna.
 
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Canelo56

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On the COMPACtenna Scan series you need to bend the radials down at a 70 degree angle and they should be about 16" long for commercial/public service freqs or 19" for 2m/70cm amateur. That antenna has too much capacitance to the ground plane and the match on VHF will be high if the radials are horizontal or 90 degrees to the antenna.

See post 16 in this thread for what my base adapter looks like with radials at a steep angle down for this antenna.
Now I am really confused, one guy tell me one thing the other something else
 

prcguy

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I can't speak for others but I am telling you the correct way to install the ground radials for the COMPACtenna Scan series. I also have a little experience owning three of them. The person that designed that antenna will tell you the exact same thing and its on their website.


Now I am really confused, one guy tell me one thing the other something else
 

Canelo56

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I can't speak for others but I am telling you the correct way to install the ground radials for the COMPACtenna Scan series. I also have a little experience owning three of them. The person that designed that antenna will tell you the exact same thing and its on their website.

I have seen that
 

mmckenna

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Now I am really confused, one guy tell me one thing the other something else
I'd bow to prcguy on this one. He's done extensive testing with them and if he says bend your radials down, then that's what I'd do.

On most mobile antennas, they are designed to be mounted on a flat vehicle roof with no sloping required. My (erroneous) assumption was that the ScanTenna worked the same way. I stand corrected.
 

Canelo56

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I'd bow to prcguy on this one. He's done extensive testing with them and if he says bend your radials down, then that's what I'd do.

On most mobile antennas, they are designed to be mounted on a flat vehicle roof with no sloping required. My (erroneous) assumption was that the ScanTenna worked the same way. I stand corrected.
I would have to say both gentlemen are correct bending the antenna to a 70° angle will give you lower band frequencies not bending it gives you high frequencies only that’s from the maker of the antenna themselves
 

prcguy

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I had a face to face conversation with the inventor "Dr. Jack" and he told me radials need to be bent down for overall matching. Its most pronounced on VHF and it doesn't affect UHF much, so bend them down if that's the only antenna you will put on the Bas-Kit.

I would have to say both gentlemen are correct bending the antenna to a 70° angle will give you lower band frequencies not bending it gives you high frequencies only that’s from the maker of the antenna themselves
 

Canelo56

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I had a face to face conversation with the inventor "Dr. Jack" and he told me radials need to be bent down for overall matching. Its most pronounced on VHF and it doesn't affect UHF much, so bend them down if that's the only antenna you will put on the Bas-Kit.
Ok will do , if you talked to the inventor of the SCan-Cann -III / What I have is the Bas- kit high frequency antenna NMO , and you say bend the radials correct?
 

Canelo56

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Ok will do , if you talked to the inventor of the SCan-Cann -III / What I have is the Bas- kit high frequency antenna NMO , and you say bend the radials correct?
These two antennas attach to each other
 

Canelo56

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These two antennas attach to each other
I bent them hopefully they are at 70 degrees they are at least 60 , everything sounds good , much better , thanks for all your knowledge on this subject, I will be eager to learn more from all you wizards!
 
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