Needed: People knowledgeable of radio antennas

[phiz]

Why? Making antennas is not easy. They are often matched to the driver circuit and can't be replaced without knowing the driver specification. Most likely you will make the performance worse.

My suggestion is to buy one comercially if your radio is designed to accept new antennas, see: http://www.theantennafarm.com/catalog/index.php?main_page=product_info&products_id=3229. If your radio was not designed to accept new antennas, hacking one on is problematic. 50 ohms is most common but you never know for certain.

Here is a GMRS 50 ohm dipole that I ran in Ansoft's HFSS, the easiest to make and great performance. Even gain in all directions:




Here is a planar bowtie, much smaller, on a FR4 dielectric (n=4). The radiation pattern is not as uniform, higher gain perpendicular to the axis:

[danneskjold]

phiz clearly knows more than I do about this, but I will share what I do know:

The antenna USMCcorps did on Arnies is questionable. He says it performs better than the stock one, which may be true, but I cant imagine it performs very well overall. Antenna length is determined by the frequency you plan on using it on..I believe the equation is 234/mhz = antenna length in feet. 234/462 (GMRS) = .5....so basically ideal GMRS antenna is 6 inches...his was around 1 meter long...

The antenna USMCcorps did on Arnies was designed after the MBITR 1 meter blade antenna...designed for 30-80mhz frequencies...not 462.

The absolute best thing you can do is to get the antenna as high as possible. I have one of these kits, and they are commonly used throughout the military: http://www.tacticalcommandstore.com/tci ... onkit.aspx
It is basically an extension cable for your antenna, and allows you to move the antenna onto your upper back while keeping the radio on your front. The farther from your body, and the higher you can get it the better.

The TCI MAST is really just a length of RG58 cable and coax connectors...you can make yourself the same thing for under $10 but I recommend the TCI one as it VERY durable and well made. Get the QD version as well.
Get a MX-BNC connector off eBay, and a TNC antenna and you will set.

It looks like TCI makes multiple versions now...I use the MBITR/QD one. I would recommend that one as they dont make any specifically designed for an Icom, so you would need to convert it anyways.

[mr_kong]

I know nothing about radios... so the length of the RG58 cable doesn't really matter?

I'm thinking about making one for my Saber II.

[danneskjold]

Shorter is better...I believe you will experience dB loss as the cable gets longer but I think it is very minimal at the frequencies we are talking about.

The one thing to keep in mind is that I have been told that the MX-BNC adaptor used for Icoms and Motorola Saber is not grounded, which in theory will make the whole thing act as an antenna and can damage your radio.
I have not personally noticed this, but it is what I have been told by those who know more about this than I do (Kong, you might know who I am talking about - Simpen on Wannabe/Gearsoc).

Many of the Sabers used today are older than we are...and Icom F4S are a good 13+ years old at this point - the newer Motos and Icoms use the SMA connector which I believe is better (some newer Icoms still do use the MX like the F30/40Gx). SMA is not perfect either, and has its share of problems...

[danneskjold]

Yes, but you would need to buy a new antenna.

[danneskjold]

2 pins = the handset connector, not the antenna.

You can buy MBITR antennas and run them off the MAST, it's what I do. I can get you a pic tomorrow if you are interested.

[Wombat Six]

Icom part AD-98FSC should allow you to connect the Icom's "J" connector to a "BNC" connector, which the MAST offers. It's about $20 from most radio parts places.

[danneskjold]

I am lazy so it took longer.





Radio is a Yaesu VX7R with a BNC adaptor on it.
Antenna is a Thales MBITR Broadband.

[Wombat Six]

How's that MBITR antenna do with the Yaesu rig you've got? Any problems on 50/144/220/440 (fuzzily recall the US VX-7Rs have 220MHz)?

[danneskjold]

It works fine, I have not noticed any problems with it. I have not done any extensive antenna testing either however, which I would like to do soon.

The MBITR has a whole sweet of antennas...off the top of my head there are 4 all together. The one optimized for the UHF range would probably be better for me in the long run (it is also a lot smaller).