Is a external antenna really necessary?

[mmckenna]

Okay tell me this… compare the performance of a Motorola haf4013 near the sharkfin in the Toyota 4Runner compared to that 1/4 wave in the dead center, and then compare that to the stock antenna.

Stock antenna inside the vehicle is going to perform worse that either of the two external antennas.

Likely you won't notice much of a difference between the other two mounted outside.

For full effect, you want 1/4 wavelength of uninterrupted ground plane under the external antenna, so 3" all the way around the base. I'd keep it spaced a foot or so away from the shark fin just to keep that from making it directional, and to keep it away from whatever RF noise might come from the GPS/Satellite/Cellular part of the antenna.

I see police vehicles with these Pctel and Motorola can antennas in my city

Yup, likely it will work fine for you. But the police vehicles having transmitters are going to be designed around some different things that you. They have requirements that the ERP (effective radiated power) of their radio (transmitter power output, minus feed line losses, multiplied by antenna gain) stays within the limitation of their license. Also, they are geared towards performance inside their area of jurisdiction with some extra added in. As a scanner/receiver user, you don't have the ERP limitation and the extra gain won't hurt.

But just looking at cost (like I said, if you haven't purchased the Motorola antenna) you will get similar performance out of the 1/4 wave antenna, or if you want the additional gain, try one of the 2 gain antennas I linked to.

 

[lcat06]

Stock antenna inside the vehicle is going to perform worse that either of the two external antennas.

Likely you won't notice much of a difference between the other two mounted outside.

For full effect, you want 1/4 wavelength of uninterrupted ground plane under the external antenna, so 3" all the way around the base. I'd keep it spaced a foot or so away from the shark fin just to keep that from making it directional, and to keep it away from whatever RF noise might come from the GPS/Satellite/Cellular part of the antenna.



Yup, likely it will work fine for you. But the police vehicles having transmitters are going to be designed around some different things that you. They have requirements that the ERP (effective radiated power) of their radio (transmitter power output, minus feed line losses, multiplied by antenna gain) stays within the limitation of their license. Also, they are geared towards performance inside their area of jurisdiction with some extra added in. As a scanner/receiver user, you don't have the ERP limitation and the extra gain won't hurt.

But just looking at cost (like I said, if you haven't purchased the Motorola antenna) you will get similar performance out of the 1/4 wave antenna, or if you want the additional gain, try one of the 2 gain antennas I linked to.

Okay so you say 3 inches from the base of the antenna in all directions so as long as it fit this requirement it doesn’t matter where on the roof it goes correct? Is the haf4013 1/4 wave? Could in the future could I combine multiple 1/4 wave scanner antennas into one feed for the sds100?

 

[lcat06]

How well would a pctel maxrad bmlpv700 work as compared to the others?

 

[lcat06]

Or the mlpv800

 

[mmckenna]

Okay so you say 3 inches from the base of the antenna in all directions so as long as it fit this requirement it doesn’t matter where on the roof it goes correct?

Pretty much. Usually the flat part of the roof, and not where someone getting in/out of the vehicle is likely to grab it.

But before you break out your drill, think carefully about the future….
While you may only want 800MHz now, your needs might change down the road.
You may get into GMRS or amateur radio. You may decide that you want to use this antenna mount for listening to VHF or UHF traffic on your scanner. If that happens, you'll want a bigger ground plane under the antenna. Easier to think of that now and drill once.

On VHF, you want 18" in all directions under the antenna. Getting it 18" in from the edge of the roof is pretty easy.

Is the haf4013 1/4 wave?

No, they are usually a 5/8 or 1/2 wave, but the radiating element is usually cut into a circuit board in a spiral pattern, so they take a performance hit. They usually work similar to a 1/4 wave.

Here's the innards of one. This one is UHF, but the 800MHz model is similar:

Could in the future could I combine multiple 1/4 wave scanner antennas into one feed for the sds100?

You could combine different band antennas into one feed to your scanner, but that requires a diplexer. A halfway decent hobby grade diplexer is going to run you around $90 or so. Much easier and cheaper to use the multiband antenna.

 

[mmckenna]

How well would a pctel maxrad bmlpv700 work as compared to the others?

mlpv800

They are all going to be pretty similar. You won't notice a 1dB difference usually.

Seems like you really want one of these low profile antennas. That's fine. You likely won't notice much of a difference between any of these. Go with whatever looks good to you.

 

[merlin]

What if I wa only scanning 800mhz trunked. Would a Motorola can style antenna have better performance than a larsen triband

What I do is use an NMO mount, like mirror mount with a maxrad or cellwave mobile. the mast works as a counterpoise.
You can use the pepper shaker sort, but the loaded mobile antennas work better.

 

[lcat06]

Pretty much. Usually the flat part of the roof, and not where someone getting in/out of the vehicle is likely to grab it.

But before you break out your drill, think carefully about the future….
While you may only want 800MHz now, your needs might change down the road.
You may get into GMRS or amateur radio. You may decide that you want to use this antenna mount for listening to VHF or UHF traffic on your scanner. If that happens, you'll want a bigger ground plane under the antenna. Easier to think of that now and drill once.

On VHF, you want 18" in all directions under the antenna. Getting it 18" in from the edge of the roof is pretty easy.



No, they are usually a 5/8 or 1/2 wave, but the radiating element is usually cut into a circuit board in a spiral pattern, so they take a performance hit. They usually work similar to a 1/4 wave.

Here's the innards of one. This one is UHF, but the 800MHz model is similar:

You could combine different band antennas into one feed to your scanner, but that requires a diplexer. A halfway decent hobby grade diplexer is going to run you around $90 or so. Much easier and cheaper to use the multiband antenna.

Yeah I putting a ham antenna in the dead middle of the roof so that’s for that. So if I decide those haf4013 antennas is what I want even though it’s 5/8 wave it still just needs three inches correct? Any recommendations for ham antennas that arnt overly large

 

[mmckenna]

Yeah I putting a ham antenna in the dead middle of the roof so that’s for that. So if I decide those haf4013 antennas is what I want even though it’s 5/8 wave it still just needs three inches correct?

Yes, doesn't matter the antenna design, it still wants at least 1/4 wave of ground plane. Even if it's a 5/8 wave.

Any recommendations for ham antennas that arnt overly large

Which bands are you interested in?

 

[lcat06]

Yes, doesn't matter the antenna design, it still wants at least 1/4 wave of ground plane. Even if it's a 5/8 wave.



Which bands are you interested in?

2m/70cm… I could put that in the dead middle of the roof for the ham then put the can antenna parallel to the sharkfin if it’s at least 3 in. Does that sound good? Thanks for the help much appreciated

 

[mmckenna]

2m/70cm… I could put that in the dead middle of the roof for the ham then put the can antenna parallel to the sharkfin if it’s at least 3 in. Does that sound good? Thanks for the help much appreciated

OK. You want some space between the transmitting antenna and the others. 2 feet would be good.

Larsen NMO 2/70 is the gold standard for dual band mobile antennas for ham use.

 

[lcat06]

OK. You want some space between the transmitting antenna and the others. 2 feet would be good.

Larsen NMO 2/70 is the gold standard for dual band mobile antennas for ham use.

Well I’m not sure my sharkfin is transmitting I don’t use siriusxm only Bluetooth so would that matter/ would I still need to be 2 feet away from the sharkfin? The ham antenna needs to be 18” in all directions and 2 ft from any other antenna I can do that but do I need to be 2ft from the sharkfin for the scanner antenna

 

[lcat06]

Any cheaper options for the ham antenna? That still has good performance if I’m taking a huge sacrifice in performance by going down in price I’ll just get the Larsen ham antenna but just wondering

 

[mmckenna]

Well I’m not sure my sharkfin is transmitting I don’t use siriusxm only Bluetooth so would that matter/ would I still need to be 2 feet away from the sharkfin? The ham antenna needs to be 18” in all directions and 2 ft from any other antenna I can do that but do I need to be 2ft from the sharkfin for the scanner antenna

No, the sharkfin isn't transitting, but it's receiving, probably AM, FM, GPS, Satellite radio, maybe telematics also. Putting a transmitting antenna too close to that can cause issues:
1. It can desense the AM/FM/GPS/Satellite/Telematics stuff so it can't hear when you are transmitting with the amateur radio.
2. Too close and/or too much power, and it can permanently damage those receivers.

Same with the scanner. Too close and you can permanently damage the scanner.

 

[lcat06]

No, the sharkfin isn't transitting, but it's receiving, probably AM, FM, GPS, Satellite radio, maybe telematics also. Putting a transmitting antenna too close to that can cause issues:
1. It can desense the AM/FM/GPS/Satellite/Telematics stuff so it can't hear when you are transmitting with the amateur radio.
2. Too close and/or too much power, and it can permanently damage those receivers.

Same with the scanner. Too close and you can permanently damage the scanner.

Alright would you recommend the Motorola haf4013 or pctel mlpv700 for the scanner if you had to choose between those

 

[mmckenna]

Any cheaper options for the ham antenna? That still has good performance if I’m taking a huge sacrifice in performance by going down in price I’ll just get the Larsen ham antenna but just wondering

There are lots of options. Larsen is the gold standard and well respected. Unfortunately their prices seem to have shot up recently.

I'm not a fan of the hobby/consumer grade antennas. I've used them in the past and was not impressed with their quality. If I'm going to drill a hole in a perfectly good vehicle, I'm not going to plug it with the cheapest thing I can find. Good antennas are expensive, but they'll last a lifetime. I think my brother in law is running a Larsen dual band antenna I bought around 30 years ago….

Here are some other options:

I loved this antenna and ran it for years. It's a shortened version of the NMO 2/70:

Larsen NMO2/70SH Premium Larsen 2m/70cm Amateur Ham Radio Antenna Short Dual Band

Larsen NMO2/70SH Premium Larsen 2m/70cm Amateur Ham Radio Antenna Short Dual Band

theantennafarm.com

You can also run a basic 1/4 wave VHF whip on a dual band ham rig. It'll work well on VHF, and the same antenna will act like a 3/4 wave on UHF. Not ~perfect~ on UHF as the radiation pattern shoots a bit high, but it does work well, and a basic 1/4 wave VHF whip is inexpensive and quite low profile.

 

[mmckenna]

Alright would you recommend the Motorola haf4013 or pctel mlpv700 for the scanner if you had to choose between those

Probably the PC Tel. It's designed for 700 and 800MHz which is where you'll find a lot of trunked systems. Remember that the Motorola is usually just a rebadged version of someone else's antenna with the price jacked up because it has the batwings logo on it.

 

[lcat06]

Probably the PC Tel. It's designed for 700 and 800MHz which is where you'll find a lot of trunked systems. Remember that the Motorola is usually just a rebadged version of someone else's antenna with the price jacked up because it has the batwings logo on it.

Roger. Probably going to go with the pctel. What antenna would be the basic 1/4 wave that you were suggesting? Could you give a link?

 

[mmckenna]

What antenna would be the basic 1/4 wave that you were suggesting? Could you give a link?

I'm running this antenna on my wife's truck:

EM Wave EM-MX0108-FT 108-960 MHz Tunable, VHF UHF Broad Band Quarter-Wave Mobile Antenna

EM Wave EM-MX0108-FT 108-960 MHz Tunable, VHF UHF Broad Band Quarter-Wave Mobile Antenna

theantennafarm.com

I'm not endorsing www.theantennafarm.com however, they have an easy to use website. Shop around using the brand/model number and you may find lower prices elsewhere.

 

[lcat06]

Let me know what you think about this, for the scanner antenna either the haf4013 or the emwave mx0746. For the ham antenna either the nice larsen or the shorter Larsen. Will I notice a difference between those two scanner antennas?