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RE: Comrex Access Portable 2USB External Antenna
To: CRTech <crtech@crtech.org>
Subject: RE: Comrex Access Portable 2USB External Antenna
From: Jon Foreman <Jon@ksgn.com>
Date: Thu, 2 Nov 2017 18:11:01 +0000
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Thread-topic: [CRTech] Comrex Access Portable 2USB External Antenna

What a wonderful reply you sent! Thank you.

Most of that I was pretty much sure of. The tools for finding towers will help. I thought the LMR-240 cable looked the best. You verified that. 

Since we are in Southern California, we do almost exclusively outdoor events. I was thinking of mounting the antenna on a short mast to a corner of the Eazy-Up. Cable run should be pretty short, but I'll probably buy a longer run just in case an odd-ball event comes up. They always do. 

In the past for some TV parade coverage I have used some large (about 15' high) light stands for wireless mic antennas. I had great receive signal from those mics that were across the street. :-)

Thanks again.

Jon Foreman
Chief Engineer/IT Manager
Office: 909-583-2150
Fax: 909-583-2170

-----Original Message-----
From: Sherrod Munday [mailto:smunday@ieee.org] 
Sent: Thursday, November 02, 2017 9:58 AM
To: CRTech
Subject: Re: [CRTech] Comrex Access Portable 2USB External Antenna

On Wed, Nov 1, 2017 at 1:08 PM, Jon Foreman <Jon@ksgn.com> wrote:
> We are using the Comrex Connect Modem on Verizon. I’m considering 
> connecting an external yagi antenna 
> (https://www.cellularsolutions.com/product/SC-230W.html) . I called 
> Comrex to see what advice they may have. The tech I talked with had never had the topic  come up of using an external antenna.

> I know in theory it should help, but it will make setups a bit more 
> complicated as they will need to figure out what direction to point 
> the antenna. Where is that tower? How’s the signal strength meter?


I have used almost that exact antenna on a non-proprietary USB cellular data modem.  (It might be the same one, but I can't tell from the labeling whether it's the same mfr.)  I used the following:

Here are my observations and notes from several years of experience:

1.  The antenna you linked (and the one I used) is not a standard single-frequency Yagi-Uda antenna, though its behavior follows the same basic principles of how a Yagi-Uda antenna works.  The one you show is a Log-Periodic Dipole Array antenna, commonly known by its acronym of LPDA.  You can search online to learn more about it (e.g.
https://en.wikipedia.org/wiki/Log-periodic_antenna ), but in short it's a very broadband antenna with a reasonable amount of directivity and gain.  A single-frequency (or narrow-band) Yagi-Uda antenna for the specific frequency band of the cellular modem would produce higher gain and directivity along with better front-back signal rejection ratio.  You would need to verify whether you are using an 4G/LTE or 3G modem and what frequency band Verizon is using.

2.  Use a high-quality low-loss cable (that may be more rigid than your typical RG-8) because you're going to be sending UHF signals down that cable, and you'll lose several dB (or many dB, depending on the
frequency) in a typical RG-8 cable.  Don't even think about using
RG-58 or its kin.  Pay the extra money for the cable and you won't regret it.  I used the following:

3.  The antenna you link will need an appropriate adapter to get from the N connector to the mini connector likely found on your modem.  Get the low-loss cable (item #2 above) with an N connector on the antenna end, and an interim connector on the modem end.  Then use a short
(~6") adapter pigtail and flexible (and higher-loss) cable to get from the interim connector to the connector type on your modem.  While you'll need to verify the specific connector for your modem, I used the following:

4.  When you deploy the system in the field, count on taking a while to orient the antenna, strap it down, run the cable, and properly gaffe (tape) it all in place so that the strain doesn't make it to the cellular modem.  Someone else set up our system once and didn't take care to do that... and you can guess where this is going ... someone tripped over the cable, and broke the antenna connector off the cellular modem's circuit board.  End of story for *that* modem's external antenna connectivity.

5.  When you do your remotes, ensure that you have access to the outdoors where you can set up the antenna and run the cable back inside through a door (e.g. passing through the weatherstripping under the door), window, etc.  You will get better performance using the external antenna indoors, but it will be dramatically better outdoors if at all possible.  The antenna's waterproof when mounted properly, and ensure that you use weatherproofing (like https://www.amazon.com/Universal-Electronics-Original-104-Moldable/dp/B0002ZPINC
) on the antenna connectors that are outdoors.

6.  Look online for tools that identify the cell tower locations.  I had modems from Sprint, Verizon, and AT&T.  Some of those carriers provide Google-based maps with overlays that show the actual tower sites for various transmission types (e.g. 3G vs. LTE).  While you can find myriad tools online via Google, here are a couple of places to
https://community.verizonwireless.com/thread/766309 (not sure if this is still current... I haven't used the app so "caveat emptor"!)

Then pull up a current map from your location, and figure out the cardinal direction for aiming the antenna.

7.  Some tools that carriers provide to use the modem with a PC (e.g.
driver packages that contain software to manage the cellular
connection) will provide you a raw signal strength number (not "bars").  Lug your laptop to the remote (yeah, I know...) and set it up with the cellular modem, get into the raw signal meter, and slowly rotate the antenna around the horizon until you find a strong signal.
Leave the antenna alone, move the modem to your Comrex, and plug it in.  Done.  (You may need to talk to Comrex to determine if they provide a Windows/Mac/Linux driver/software package for their modem, but the specs make it look like any other garden-variety cellular data modem.  BTW, please don't tell them I said that -- they might get worked up about me calling it garden-variety when they claim it's "Pro-Grade" and uniquely suited to professional broadcast use. ;-) (And, don't get mislead by their claim of the "high-gain (2.1 dB) antenna that comes with the modem.  Pshaw.  But I digress.)

8.  I guess I should mention -- find a tripod that has a nice wide base and an extendable pole to get the antenna up in the air a few feet over your head.  The elevation won't make a real difference, but it looks cool.  ;-)  Mount the antenna on the pole with appropriate pipe clamps (that mine came with in the box).  When you're ready to aim the antenna, loosen the lock on the pole and simply rotate the entire pole and cable until you find where you want it.  Lock it down there, and gaffe up the cable.  If you're going to have any chance of wind (or people around the tripod) then make sure to secure the tripod with appropriate weights at the bottom and/or tethers (I used non-conductive standard string) from the top to appropriate anchor points, ensuring you don't end up with trip hazards or guillotine cords at neck level.  :-)

Hope this helps!

Sherrod Munday

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References: POV
(Tim Swanson <timswanson@kswp.org>, 31 Oct 2017 18:38:12 -0000)
Comrex Access Portable 2USB External Antenna
(Jon Foreman <Jon@ksgn.com>, 1 Nov 2017 17:09:10 -0000)
Re: Comrex Access Portable 2USB External Antenna
(Sherrod Munday <smunday@ieee.org>, 2 Nov 2017 16:58:05 -0000)
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