Radio cutting out siren, etc

[jfab]

Hello all,
My captain at the FD is having problems with his POV install and I'm wondering if you guys can help.

He had a VHF Kenwood installed in his truck. The company that did the install wired the radio to his ignition, and a glass mount antenna. He was running hot the other day and when he keyed his radio, the siren cut out.

He had the company come look at it again, and they installed an NMO antenna on the hood. After that, when the radio was keyed, several warning lights on the dash began flashing and it would lower the volume of his AM/FM stereo, as well as cut the siren out.

He also has several LED lights installed, but those appear unaffected.

Any advice (other than call the shop who installed it) you can give would be great. I'm baffeled by this and wanted to ask the experts!

Thanks!

 

[cdknapp]

I have seen a lot of strange and different things happen when wiring lights, sirens and radios (especially ALL together) through ignition switches, including burning the ignition switch itself out. This may or may not be an issue. You might want to try to power at least the radio directly off the battery (of course with in-line fuses). Depending on what lights and siren (power-wise) are being used, maybe consider the same with them, or wire them to the fuse panel. While it might be more convenient to have everything power down when turning the key, it puts a lot of addition power through the ignition switch. No guarantees on this, but that has been the fix for the times I have seen this happen. Good luck!

 

[mmckenna]

Wow, that must be a pretty crappy install, no offense intended. Sounds like you might need to get a shop to redo the install from the ground up. Trying to chase all these issues and get them fixed might take a while, and create a whole lot of work. Might be better to gut it and do a proper install.

 

[jfab]

Wow, that must be a pretty crappy install, no offense intended. Sounds like you might need to get a shop to redo the install from the ground up. Trying to chase all these issues and get them fixed might take a while, and create a whole lot of work. Might be better to gut it and do a proper install.

I'm inclined to agree with you. The shop that did the install is a very well known company and has done a great job on our department apparatus lighting, but apparently radios aren't their strong suit. I'm thinking he may want to just run it directly to the battery, but that doesn't rule out the antenna issue.

 

[cabletech]

As a equipment installer that 'built' emergency vehicles (over 1500) for several years, I have to say that I never ran into this problem.

If you wish to use the ignation switch to power your equipment, I would recommand that you install a 50 amp 'horn' relay in the system.

The main side of the relay goes to the switch and ground to a good clean ground.

Run a 6 or 10 ga. wire to the source side of the relay from the battery and then your equipment from the other side.

This takes the 'load' off the switch and reduces problems that way.

The best bet is to find some one that REALLY knows what they are doing and have them tear down the system and rebuild it.

Take it to a radio shop, as they deal with emergency vehicles all the time.

 

[jparks29]

I guarantee you it's an RFI issue.

When transmitting 100W literally feet from an ECM/PCM, it'll do exactly that. Strange things can happen, like idle changes, or even killing the engine, or in your case, your display going crazy.

This signals to me that the radio install is NOT done properly, as there is most likely RF radiation being reflected BACK to the radio. Either the antenna is mounted improperly, or it's the wrong antenna type (wrong band).

Tell them to drill a hole in the roof, and mount an NMO antenna for the proper band. I bet you a hose coupler that it fixes the problem.

 

[ofd8001]

I second the motion to make greater use of relays. We've done a boatload of radio and emergency equipment installations over the years on our department's command vehicles. You can use an igition sense circuit to actuate the relay. However if your guy wanted to have his radio on all the time, he'd need a second relay with that second relay being hot all the time for the radio with the light and siren relay being hot on key only.

Tying radios or emergency equipment directly into a fuse panel may create an issue of trying to draw more current than it was designed to handle. That in turn could lead to a slight voltage drop and microprocessor circuits act funny if they don't get enough juice.

So my thinking the issue is too much power is being taken from the fuse panel all at once, "robbing" some electrical components of the "juice" they need to work properly.

Forgive the analogy but imagine this. You are at home in the shower and someone flushes the toilet. For a brief moment or two the shower water gets hotter, because some of the cold water that was going to the shower went to the toilet. You might say "Yow!" Going back to the siren, it quiting is its way of saying "Yow!" because something it was depending upon was taken away.

Be sure that the appropriate over-current protection is provided in the form of fuses, circuit breakers or fusible link wire. Having a fire vehicle being the fire incident is a bad professional embarrassment.

Around our place we use circuit breakers as much as we can. If there is an over current situation and you use fuses, you're out of commission until they are replaced. With circuit breakers, they will re-set themselve after a few moments.

 

[WB4CS]

I second the idea about possible RFI. I once had an antenna installed that had a bad pin on the NMO connection. When I keyed up the radio all of the warning indicators on the dashboard (parking break, TPMS, check engine, etc) would come on and then go off when I unkeyed the radio. Replaced the antenna and everything returned to normal.

If the antenna checks out (correct band, good SWR, and correctly installed) then as the others have pointed out, sounds like a crappy install job.

Good luck chasing this one down!

 

[radioalbany]

Powering radios

I agree with Cabletech et. al.

I've built dozens of broadcast remote vehicles, which feature both regular two-way radios and wide-band UHF-FM high-power transmitters for on-air use. I've always used ignition-sense to control power relays wired directly to the battery (through fuses) to power all the gear.

The only thing I'd add is that the typical tab-contact "sugar cube" relays rated at 40A or less often don't last long under this duty, since they pull in every time a reporter turns on the ignition. (Among other things, the interface board I built has 100,000 uF of filter capacitors, so the turn-on surge is considerable.)

For me, the solution was a gutsier relay. I used the White-Rodgers 120-908 (available from Mouser.) It's SPST-NO with the contact rated at 100A. It also has a 15VDC coil. The manufacturer says that many 12VDC power relays overheat when running on the 14 VDC or so supply from a vehicle.

One installer told me that some newer car ignition switches might not handle the current for the contactor (about 600 mA). The latest version of my boards key the relay coil from the unswitched hot lead using a 2N7000 or equivalent mosfet.

These pull in with a mighty WHACK, but they last forever.

Here's a link to the Mouser product page if you're interested:

120 108752 White-Rodgers | Mouser


Good luck!

Andrew Ellis NO6E
Lafayette, CA

 

[kg4ley]

Install

I second the idea about possible RFI. I once had an antenna installed that had a bad pin on the NMO connection. When I keyed up the radio all of the warning indicators on the dashboard (parking break, TPMS, check engine, etc) would come on and then go off when I unkeyed the radio. Replaced the antenna and everything returned to normal.

If the antenna checks out (correct band, good SWR, and correctly installed) then as the others have pointed out, sounds like a crappy install job.

Good luck chasing this one down!

Hve installed many radios ham gear and public saftey and antenna problems are usually the culprit with funny problems.Always check with a vom ground to the point of the mount,center of mount to whip,pl259 or whatever connects the radio.All it takes is one stray wire short to cause heartaches.Never think that ever solder joint you do is perfect.Just me but through the glass for an antenna really is a bad idea when it comes to a high power radio.I know of installers how use to install antennas on the rear deck inside of the vehicle for stealth reasons,that was a really bad idea with 110 watts bounchig around where it should have not been.

 

[KB7MIB]

Wirelessly posted (Mozilla/5.0 (X11; Linux i686; U; en-US) Gecko/20081217 Vision-Browser/8.1 301x200 LG VN530)

Another suggestion, make sure that the battery and the alternator are in good shape, and are appropriately sized to handle the extra amperage draw when the radio, emergency lights and siren are all going at the same time. A 2nd battery may be a good idea.

 

[Drachen_Fire]

Through-the-glass is a terrible idea on modern vehicles. I would bet the problems you were having when the antenna was on the glass was due to the antenna design and also because a lot of modern glass has integrated defroster films and such.

Now that the antenna has moved, you are having a different set of problems.

What type if coax is used? Standard RG58, or did you get some RG8X? Something smaller? In some installs, running the coax parallel to the other aftermarket wiring is a bad, bad deal. I would bet it's RFI, and there is a leak somewhere, more than likely at the connector or the mount.

One thing is certain here, something is not taking the strain of a 100w transmitter. Make sure you have good coax and a proper antenna mount and antenna. If you have the 100w radio in there, a standard antenna won't do the trick. Use heavy-duty connectors, RG8X coax, and a bulkhead mount, and an antenna capable of having 100 watts shoved through it.

He could always go into the software and dial back the TX power to the 50 watt range.