Messy Marti SHots

A case of PEBKAC (Problem Exists Between Keyboard and Chair)? Tell us about your war stories!
Post Reply
PaulBWalkerJr
Posts: 192
Joined: Fri Dec 14, 2007 5:46 am

Messy Marti SHots

Post by PaulBWalkerJr » Thu Dec 03, 2009 11:02 am

So, 2 months ago we tested our Marti with a directional rec'v antenna on a 20 ft pole and a non directional transmit mounted in the middle of a roof on a moving Mercedes SUV.

We got about 8 miles rock solid and depending on terrain, elevation, 10 to 11 miles..

Fast forward to last weekend. I am doing a remote from a local IGA store. We're probably barely 3 miles as the crow flies from the radio station... and I got ZERO signal from inside the building.

I was standing at the end of a cash register, facing the front door.... my mic cord leads into the foyer/lobby, with the Marti on it's side laying below the payphone next to the Electric Scooter with the antenna about 5 to 6 feet into the parking lot... but it worked.

Here's a picture:

http://www.onairdj.com/marti.jpg

User avatar
BroadcastDoc
Site Admin
Posts: 2729
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: Messy Marti SHots

Post by BroadcastDoc » Thu Dec 03, 2009 11:39 am

I'm assuming that you're using a 450MHz system?

Anyway, you shouldn't ever run a Marti antenna inside of a building unless you can help it - always go on a tall pole outside of the building. Not only can someone grab it and get a nasty RF burn, but your signal won't be very good either.
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

PaulBWalkerJr
Posts: 192
Joined: Fri Dec 14, 2007 5:46 am

Re: Messy Marti SHots

Post by PaulBWalkerJr » Thu Dec 03, 2009 11:46 am

BroadcastDoc wrote:I'm assuming that you're using a 450MHz system?

Anyway, you shouldn't ever run a Marti antenna inside of a building unless you can help it - always go on a tall pole outside of the building. Not only can someone grab it and get a nasty RF burn, but your signal won't be very good either.
If I had to, I was ready to monut the antenna on top of a soda machine outside the front door

Scott.Cason
Posts: 134
Joined: Mon Aug 31, 2009 6:54 pm
Location: LaGrange Kentucky
Contact:

Re: Messy Marti SHots

Post by Scott.Cason » Thu Dec 03, 2009 1:43 pm

BroadcastDoc wrote:I'm assuming that you're using a 450MHz system?

Anyway, you shouldn't ever run a Marti antenna inside of a building unless you can help it - always go on a tall pole outside of the building. Not only can someone grab it and get a nasty RF burn, but your signal won't be very good either.
Not only that, but if the RF fries the point of sale system in the store, guess who's liable?
LaGrange Communications - http://www.lagrange-com.com
Froggy 95.9 - http://froggy959.net/

User avatar
countrykev
Posts: 328
Joined: Thu Jan 10, 2008 3:18 pm
Location: Not Wisconsin, eh?
Contact:

Re: Messy Marti SHots

Post by countrykev » Thu Dec 03, 2009 5:54 pm

What was the power output of the Marti?

I have only ever used omni directional antennas when within a mile or so of the station. Anything beyond that use a yagi.

And I'm with the peanut gallery. Inside a store is always a crapshoot, and yes, you can interfere with the cash registers and that's definitely a bad thing. Like Doc said, outside or near a window facing the station is best bet.
What the heck am I supposed to write here?

User avatar
MHVoris
Posts: 53
Joined: Sun Oct 26, 2008 6:57 pm
Location: Omaha, Nebraska
Contact:

Re: Messy Marti SHots

Post by MHVoris » Thu Dec 03, 2009 9:14 pm

We always used a yagi regardless.. Inside a building you will have issues with building construction not to mention all the metal on the refrigeration units to mess up one's signal.
Mark H Voris CBRE
Chief Engineer
Spirit Catholic Radio - KVSS
Omaha, Nebraska

boiseengineer(old)

Re: Messy Marti SHots

Post by boiseengineer(old) » Thu Dec 03, 2009 10:09 pm

I’ve seen remotes where the antenna is on a short stand head high pointing at the station tent. People were running into it. “You’ll put your eye out!” Causes all sorts of RFI problems.

There's a lot of RF coming out the front of a 5-element Yagi when it's fed by a Marti RPT-40's (will do almost 40 watts on a good day).

The omni 5/8 mag mount on top of the station van in the parade works pretty good. Put up with a little picket fencing. Just remember to take it off before going into a garage with only 4" of clearance.

abideejay
Posts: 1
Joined: Sun Nov 25, 2012 3:18 pm

Re: Messy Marti SHots

Post by abideejay » Sun Nov 25, 2012 3:42 pm

We've used omni antennas mounted to our vehicles with wireless mics for at least the past 15 years...way before I started. Granted, our city isn't huge, but there are but a few select places where we have issues, and even those issues remain with yagi antennas. Too many years of DJs leaving the yagi (and marti!!) behind...leaving the yagi in the bed of the station pickup...and let's not forget the time that our wonderful mall security officer confiscated all of our equipment because the yagi was "too dangerous".

K9VC
Posts: 13
Joined: Thu Nov 10, 2011 10:58 pm

Re: Messy Marti SHots

Post by K9VC » Tue Dec 04, 2012 12:48 pm

Here are a few thoughts:
Never assume. Always test your cables for being good. Put a dummy load at one end and the transmitter at the other. Are you reading zero reflected power? If not start with the connectors and then look for damage to the coax. This stuff gets stepped on, dunked into trunks and boxes, and silently absorbs all sorts of abuse.
You're using a directional receive antenna? Dare I ask: why?? Consider this: use a non-directional receive antenna, and then feed it into a preamp. If they're still around, Advanced Receiver Research made the bestest ones IMHO.. The only reason you would use a yagi on the receive end is if you are hassled with interference from a same channel transmitter, or a near channel one. If the latter, consider a cavity ahead of the receiver.
NEVER put TX antennas inside. Not only can this piss off the POS (No Guys, that's "Point of Sale") system, it gets into the customer PA and can burn some little snot-nosed rugger who is fascinated with your clever use of a coat hanger. (uh-huh, how many of us have had to kludge together a dipole because the "sports guy" left the antenna a) in his trunk b) at the stadium, c)at his girl-friends'??? If you're running either 15 or 40 watts @ 3-miles, there is almost no reason that should result in zero signal. Look for a flaw.

Happy DX!
Vic

grich
Posts: 314
Joined: Fri Sep 02, 2011 11:19 am
Location: MP89.5, Mason City Subdivision

Re: Messy Marti SHots

Post by grich » Wed Dec 05, 2012 12:59 pm

One of my clients has been whole-hog on Martis for over 30 years. Still have to be...cell service is nearly non-existent in several of the areas they do ball game remotes. VHF system. Dual Yagis on a HAM-IV rotor, 350' AGL, cavity installed ahead of the rcvr.Transmit Yagi mounted to a push-up flagpole with a park-on mount. They haven't broken the flagpole yet...in service 15 years now. Several schools allowed permanent antenna mounting, so all the sports guy has to do is plug in. Shots of 30 miles are routine...one install is 37 miles from the tower.

Some of those pesky in-store remotes are being done with Skype now, to avoid the hassle of getting line-of-sight with the antenna or getting cords out of the building.

ChuckG
Posts: 927
Joined: Tue Mar 11, 2008 11:12 pm
Location: Moo
Contact:

Re: Messy Marti SHots

Post by ChuckG » Thu Dec 06, 2012 1:03 am

countrykev wrote: And I'm with the peanut gallery. Inside a store is always a crapshoot, and yes, you can interfere with the cash registers and that's definitely a bad thing.
I set one up inside a casino up in Red Cliff some years back. That didn't go over well at all. Tried to move the antenna outdoors and found the back door had an alarm on it. Steeeeerike-two. Ended up with the marti outside, a wireless mic receiver on the window ledge and the wireless mic inside.
<><><><><><><><><>
Chuck Gennaro
Central Wisconsin

Post Reply