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Antenna Question

Posted: Sun May 14, 2006 6:38 am
by Gocart878
Ok, i realize you guys are not fans of the veetronix reciever but i have a few questions for you that i hope you can answer. We have a New fire siren in a remote location in our district. the veetronix alert reciever sits inside a nema 4 weathertight box. and the antenna for it a small 6 inch antenna in our split 403-430mhz "yes we border canada" sits outside the box electrical taped to a small peice of metal. "i know its not right" it works perfectly crystal clear on a clear day, but as soon as the skies become overcast or rainy, the radio signal starts to split up. a small ht1250 works great in this same area at all times. what can i do. also, this antenna is missing the ball at the top. is that my problem?

thanks for your help/

Posted: Sun May 14, 2006 7:12 am
by thebigphish
probably. Get a proper antenna mount, (maybe a piece ofappropriately sized sheet metal cut to size), a real mount, some grounding strap, and a good grounding spike (or a good ground connection) and set the antenna up the right way ... or you may choose a groundplaneless antenna to make it easier...and get the radio a decent signal at all times.

A better antenna...

Posted: Sun May 14, 2006 7:55 am
by Tom in D.C.
If you mount the antenna firmly to the side of the box see if you
can have the antenna above the top of the box. Use a piece of
aluminum about 8 by 10 inches, with a two-inch section bent
at a right angle to bolt to the upper side of the equipment box.
Put the correct antenna connector (NMO, BNC, whatever) in the
center of the aluminum. You will probably get a proper ground
via the plate's connection to the equipment box. I've used this
exact type of setup on UHF for monitoring and it seems to work
very well. The overriding consideration is to give the antenna,
however it's mounted, a clear view in all directions, as well as a
proper reflective ground plane, and if you just
"clean up" the present situation you should be fine and the
system will hear as well as the HT does, assuming the control
box receiver has a decent front end installed.

Re: Antenna Question

Posted: Sun May 14, 2006 10:58 am
by Rayjk110
Gocart878 wrote: also, this antenna is missing the ball at the top. is that my problem?

Nope, that won't effect it.

Re: Antenna Question

Posted: Sun May 14, 2006 4:13 pm
by Will
Rayjk110 wrote:
Gocart878 wrote: also, this antenna is missing the ball at the top. is that my problem?

This is a Citizens Banders mith....

A 403-430 antenna would be closer to 7" long.

Is the NEMA box metal, as I suspect? If so you need a insulated mount or a barrel connector with the correct mate for the antenna connector (not knowing what the correct antenna connector for the Veetronics radio).
You can mount the antenna directly on the metal box, altho not enough ground plane, it should work well for RX.

If the NEMA box is plastic or if you are mounted in a building a remote mobile mount 7" antenna above the box would "suck in" a better signal.

A "poor mans" UHF dipole antenna.
A simple UHF antenna that could be used for this type of application:
A lenth of RG58/CU cable, at the antenna end, remove 7 1/2" of the outer jacket..DO NOT cut the sheild. Fold the shield back down the cable,over the jacket should be about 6 1/2 " of shield. The exposed center conductor with the insulation still on it would be about 6 7/8" in length. The radio end needs the proper connector to mate with the radio receiver.

Mount this in the clear away from metalic surfaces. A peice of small plastic pipe can hold the "antenna" inside and allow a mounting point 18" below the top. Hang it by a string in the attic!!!

Posted: Sun May 14, 2006 7:34 pm
by jim
"A "poor mans" UHF dipole antenna.
A simple UHF antenna that could be used for this type of application:
A lenth of RG58/CU cable, at the antenna end, remove 7 1/2" of the outer jacket..DO NOT cut the sheild. Fold the shield back down the cable,over the jacket should be about 6 1/2 " of shield. The exposed center conductor with the insulation still on it would be about 6 7/8" in length. The radio end needs the proper connector to mate with the radio receiver. "


...Also known as a Shakespear Big Stick!

Posted: Sun May 14, 2006 10:25 pm
by Will
Thanks, Jim!

Posted: Sun May 14, 2006 11:58 pm
by kc0qgl
Gocart878 wrote:
also, this antenna is missing the ball at the top. is that my problem?

Nope, it's just to keep eye balls intact. :)

kc0qgl