51SL antenna question

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Spectre
Posts: 4
Joined: Fri Mar 28, 2008 12:36 am

51SL antenna question

Post by Spectre »

Hi Folks,

I was wondering if anyone knew a source for a stubby antenna for the 51SL? The way I have to carry it at work is awkward with the standard length. Thanks for any help.

Mike
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Intrinsically Safe
Posts: 347
Joined: Sat Oct 13, 2007 9:19 pm

Re: 51SL antenna question

Post by Intrinsically Safe »

Is this for 800?
Sean Penn: Last year I went to Iraq. Before Team America showed up, it was a happy place. They had flowery meadows and rainbow skies, and rivers made of chocolate, where the children danced and laughed and played with gumdrop smiles.
flat4turbo
Posts: 60
Joined: Wed Dec 26, 2007 3:06 am

Re: 51SL antenna question

Post by flat4turbo »

I'm not sure what band your radio is in, but the antenna is truly important for the radio to operate effectively. Take your time making your choice, as every manufacturer makes multiple operating ranges within each band.

The antenna on our EFJs are RP-SMA (Reverse-Polatiry SMA), so any OE Motorola antenna, stubby or otherwise, will work (Beware the knock-off eBay cheapos).

Also, I've heard really nice things about the Larsen duck antennas, you might want to look into those as an alternative.
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Intrinsically Safe
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Re: 51SL antenna question

Post by Intrinsically Safe »

Good Point Flat4. I was asking the band as I know a lot of people who use the Larssen ducky 800 antenna with much success.

I.S.
Sean Penn: Last year I went to Iraq. Before Team America showed up, it was a happy place. They had flowery meadows and rainbow skies, and rivers made of chocolate, where the children danced and laughed and played with gumdrop smiles.
Spectre
Posts: 4
Joined: Fri Mar 28, 2008 12:36 am

Re: 51SL antenna question

Post by Spectre »

Thanks for the replies guys. Yes it is for 800. The issue is that we use the portables when were on foot in the field. The problem is there aren't enough repeaters to cover all the areas we work. So the portables are ofter used on an almost line of sight style to talk to other teams working in the same area's. Otherwise we usually use our vehicle units for comm. Thanks very much for the quick info. It's truly appreciated.

Mike
flat4turbo
Posts: 60
Joined: Wed Dec 26, 2007 3:06 am

Re: 51SL antenna question

Post by flat4turbo »

Maybe I.S. can help shed some personal experience on this one, but in my own opinion, it is very difficult to get an esthetically pleasing "shorty" antenna and get the best performance. I understand the longer antennas can be cumbersome and get in your way, but the shorter ones are not always the best choice for two reasons:

A) Electrically they are typically a shorter wavelength, plus (helical vs whip)
B) Since the antenna's effective radiation and reception point is so close to the body on "stubby/shorty" antennas, if you find yourself in semi-remote locations, often this will be a hinderance. (Your body is 98% water, and water deflects/deforms radio frequency almost as good as a metal surface)

If you need max performance, you're probably going to want the "Stand-off" style antennas, which hold the active portion of the antenna away from the head and body and have a distinctive tall, fat base about 4-5 inches before it narrows to the conductive part at the tip. This keeps the antenna away from the body and radio chasis which will help with RF radiation.

But if you are more concerned about keeping a low profile with the antenna, you will likely be sacrificing some performance. This difference will be best noticed when you are very far from the repeater and the radio is on your waiste.

Make your decision based on where you and your teams spend most of their time,near or far from the towers, in or out of buildings, etc.. ALL that said, people think the stubbies are "cool", so they use those instead, not always the best choice.

Hope that helps a little. :-)
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Intrinsically Safe
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Re: 51SL antenna question

Post by Intrinsically Safe »

Flat4 is right. The farther you get away (especially in point to point (non repeater)) the less range you will get with the stubby antenna.
If you are still working LOS you should be ok though.
If you need more range but wanted to keep the stubby you *could* get the public safety shoulder mic so the antenna will be up on your shoulder thus avoiding the body sheilding effect. (my buddy's chide me that I have a -6db pad for an ass) therefore my reception at the hip is not as good as other people :D
Sean Penn: Last year I went to Iraq. Before Team America showed up, it was a happy place. They had flowery meadows and rainbow skies, and rivers made of chocolate, where the children danced and laughed and played with gumdrop smiles.
N5CWM
Posts: 7
Joined: Tue Mar 04, 2008 4:15 pm

Re: 51SL antenna question

Post by N5CWM »

Would the antenna from a Motorola "brick" phone (ie, DynaTac style) work? I happened upon my first
cellphone the other day at my Dad's while cleaning out some of my old stuff. Out of curiosity the
antenna from that cellphone had the same connector. I wasn't really surprised, but I was thinking the
same thing regarding the antenna working on an 800mhz XTS or 5100.

Maybe a search on EBAY, CraigsList or such for a cheap/inoperative early Moto cellphone?

This is very similar to the one I have (which I don't really want to part with at this time).

http://techepics.com/files/worldsfirstcellphone.jpg
Spectre
Posts: 4
Joined: Fri Mar 28, 2008 12:36 am

Re: 51SL antenna question

Post by Spectre »

I.S & Flat4, thanks very much for all the info (it helps a lot). Can you advise me based on the following "general" type of situation I'd be using the radio. Mixture of outdoor/indoor within a 1/2 mile radius at most (most always more like under 300 yards) mainly in SF home areas ie. no high rises. In that type of scenario do you forsee a stubby causing any appreciable problems. Finally are there any online shops you would recommend?
Sorry to ask so many questions. Shutting up now.

Mike
flat4turbo
Posts: 60
Joined: Wed Dec 26, 2007 3:06 am

Re: 51SL antenna question

Post by flat4turbo »

Well N5CWM, that's pretty funny. Although it would be interesting to see how well a Brickphone antenna would perform and it surely is in the realm of what I was referring to, I believe he needs a few for his crew.

Spectre, if the performance with the stock EFJ antenna is inadequate for your team, then I would suggest you try a "stand-off" (dipole) antenna like I mentioned earlier. If the EFJ antenna works well enough, but it gets in your way too often, then you can try the /\/\oto 800Mhz whip antenna which are almost identical in performance, but more flexible.

For EXAMPLE:
Motorola OE antennas offer three types:

1) ~4" tall: 1/4 Wave Whip "Stubby"
2) ~6" tall: 1/2 Wave Whip
3) ~8" tall: 1/2 Wave Dipole <"stand off" style>
---
4) Larsen have a number of different really nice "performance" antennas

Just pick any two or three antennas and you will just have to field test them to determine what works best for your unit.

I really do not have a preferred vendor in mind. Shop around, expect to pay between 18~40/ea depending on the style and place you go. Be wary of the $7-12 antennas unless you have reasonable assurance it is the real deal and not a knock-off.
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Intrinsically Safe
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Re: 51SL antenna question

Post by Intrinsically Safe »

The old adage I've always went by is 1 mile per watt. Of course that is theoretical maximum. Kinda like 100MBs LAN connection.
I think if you stay around 1/2 mile or so you should be fine with a good quality 1/4 wave antenna. Indoors may suffer a little but 800MHz has better penetration than VHF or UHF does.

I.S.
Sean Penn: Last year I went to Iraq. Before Team America showed up, it was a happy place. They had flowery meadows and rainbow skies, and rivers made of chocolate, where the children danced and laughed and played with gumdrop smiles.
Spectre
Posts: 4
Joined: Fri Mar 28, 2008 12:36 am

Re: 51SL antenna question

Post by Spectre »

Thanks Flat4, will check into your suggestions.
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