New Amp Install (picture heavy)

[M0GVZ]

While I agree with you, have you had a good look at some of the modern vehicles grounding straps??
On my old GMC I had to replace at the factory straps going from engine to frame as they were shit from the factory and didn't like my TS 500.

Yes, I did a full HF install in my 2010 car when it was 18 months old the first weekend I bought it You wouldn't believe how many times I did the measuring before putting a hole in the roof for an antenna.

The ground straps for the engine are designed for electrical rather than RF ground and a bit of wide braid from a bolt on the head to the firewall will help mitigate any RFI from the engine.

As you're finding out, fogdog, more power brings with it a lot more headaches and the trade-off isn't always worth it. After reading the specs for the amp and the coax I'm afraid you've found the limitations of the coax which is probably what is causing your problem If you're using RG8X to the antenna it quite simply isn't rated that high even at 1:1 SWR. The higher the SWR, the lower the max power the coax can handle. RG8X is only rated to 350W at 40C. 1200W PEP aside, even at 600W RMS you're at almost double the coax rating. So what'll happen is the insulation from the core to the inner braid simply won't be able to handle the voltages and it'll be arcing. At best you see SWR spikes. At worst it melts, becomes a dead short and the first you're aware of that is when smoke starts coming out of the amp. My advice is the same as given on page 1...upgrade to LMR240 at the very least.

As to manufacturers instructions, they can't agree even amongst themselves.
If you read the article I linked to it tells you why putting the ground on the battery is bad and why fusing the ground is bad. Kenwood make both amateur and commercial radios. On their amateur ones the ground lead is as long as the positive, is fused and the manual tells you to connect it directly to the battery probably like your amp and CB did. On their commercial gear the ground wire is a short tail, is unfused and it tells you to connect it to the body at the nearest point. All commercial transceivers do the same - short tail, unfused, connect to the body. Why? Eliminates a ground loop and the problems in the article I linked to. Given their commercial transceivers are built to a far higher standard I am inclined to believe the short unfused ground wire to the nearest point on the vehicle is the correct solution and have installed a Kenwood TS480SAT, a 200W Kenwood TS480HX, and Icom 7000 and a Kenwood TM-D710 dual bander that way all without any issues. I can drive out in the countryside with the preamp on and get absolutely no interference at all from the vehicle. I can and have had conversations on 10m both on FM and SSB with the meter reading S0 with the other end being quite clear to listen to.

 

[222DBFL]

Yep, I changed my coax from antenna to lmr240 recently and did notice a difference as far as noise levels were concerned. In also use lmr400 for all my jumpers. Lmr240 will work just the same. I just happen to have some extra lmr240 and 400 so I used it. I just did a coax upgrade for a friend of mine that runs a yaseu ft101 with an amp (800 watts pep), he too was seeing a spike in swr readings and he was using rg8x (100ft), changed the coax to 100ft of lmr240 and he is a very happy camper now. M0GVZ is correct IMO, when you start adding a lot of power, everything has to be in tip top shape , if not it shows. Get some good times microwave lmr240uf (uf= ultra flex) and you should be good to go. I didn't think it would make much difference until I tried it. In my own experience, the lmr240 does a better job hands down. JMO. I know a lot of people will say the difference is so small, but believe me it makes a difference. Good luck and hope you get it sorted. God bless

 

[AL567]

Off topic just a bit but, when I had an issue with my radio I called Galaxy and the tech there told me that "Galaxy" radios needed to be wired straight to the battery both positive and negative. Something about How they are made. I had mine grounded to the chassis at the time. he went on to say something to the effect that cobra, uniden etc was made different so they can be grounded to the chassis but galaxy's needed to be straight to the battery. He Also added to run a ground strap directly from the radio to a bolt under the seat as well. just telling you what the tech told me. So what's the difference?

 

[M0GVZ]

Off topic just a bit but, when I had an issue with my radio I called Galaxy and the tech there told me that "Galaxy" radios needed to be wired straight to the battery both positive and negative. Something about How they are made. I had mine grounded to the chassis at the time. he went on to say something to the effect that cobra, uniden etc was made different so they can be grounded to the chassis but galaxy's needed to be straight to the battery. He Also added to run a ground strap directly from the radio to a bolt under the seat as well. just telling you what the tech told me. So what's the difference?

There is no difference. He doesn't know his arse from his elbow. I've just tested every single radio in my shack, all 8 of them from 40 channel UK 4W CBs from four different manufacturers to a Pres Lincoln to a cheap Wouxun to a Kenwood TK-7180 trunk radio to a Kenwood TS590S HF radio and every single one of them has DC continuity from the ground wire to the case and the outer of the antenna socket.

So his advice contradicts itself because connecting a wire from the radio to a bolt under the seat is exactly the same as connecting the ground wire to a bolt under the seat as far as powering the radio is concerned. But one thing my test proves is that your radio's circuit will be the path to the battery negative terminal if there's a fault on the main ground wire from the battery to the body/frame if you connect the ground wire of the radio to it.

 

[AL567]

I figured as much. You can learn more reading threads here. Total agreement on that. You just have to filter out the ones with knowledge from the rest which isn't hard to do. since the phone call to Galaxy I've not been all that impressed with Galaxy as a whole anyway.

 

[M0GVZ]

They tend to employ the lowest denominator when it comes to "technicians" who answer the phone. Anyone with any decent knowledge at a company like that doesn't talk to non-commercial customers.

 

[GnG8d]

There is no difference. He doesn't know his arse from his elbow. I've just tested every single radio in my shack, all 8 of them from 40 channel UK 4W CBs from four different manufacturers to a Pres Lincoln to a cheap Wouxun to a Kenwood TK-7180 trunk radio to a Kenwood TS590S HF radio and every single one of them has DC continuity from the ground wire to the case and the outer of the antenna socket.

So his advice contradicts itself because connecting a wire from the radio to a bolt under the seat is exactly the same as connecting the ground wire to a bolt under the seat as far as powering the radio is concerned. But one thing my test proves is that your radio's circuit will be the path to the battery negative terminal if there's a fault on the main ground wire from the battery to the body/frame if you connect the ground wire of the radio to it.

Cobra/Uniden isolate the board and chassis at DC. Where is your elbow?

 

[binrat]

To the OP,
In regards to the "-" side coming from the battery not frame. A quick short term fix is to possibly fuse it as well as the "+" side. I have had more than a few HF rigs fused that way. If something does go wrong with your vehicles grounding, it will only feed back through to the fuse limit.

 

[fogdog]

Yes, I did a full HF install in my 2010 car when it was 18 months old the first weekend I bought it You wouldn't believe how many times I did the measuring before putting a hole in the roof for an antenna.

The ground straps for the engine are designed for electrical rather than RF ground and a bit of wide braid from a bolt on the head to the firewall will help mitigate any RFI from the engine.

As you're finding out, fogdog, more power brings with it a lot more headaches and the trade-off isn't always worth it. After reading the specs for the amp and the coax I'm afraid you've found the limitations of the coax which is probably what is causing your problem If you're using RG8X to the antenna it quite simply isn't rated that high even at 1:1 SWR. The higher the SWR, the lower the max power the coax can handle. RG8X is only rated to 350W at 40C. 1200W PEP aside, even at 600W RMS you're at almost double the coax rating. So what'll happen is the insulation from the core to the inner braid simply won't be able to handle the voltages and it'll be arcing. At best you see SWR spikes. At worst it melts, becomes a dead short and the first you're aware of that is when smoke starts coming out of the amp. My advice is the same as given on page 1...upgrade to LMR240 at the very least.

As to manufacturers instructions, they can't agree even amongst themselves.
If you read the article I linked to it tells you why putting the ground on the battery is bad and why fusing the ground is bad. Kenwood make both amateur and commercial radios. On their amateur ones the ground lead is as long as the positive, is fused and the manual tells you to connect it directly to the battery probably like your amp and CB did. On their commercial gear the ground wire is a short tail, is unfused and it tells you to connect it to the body at the nearest point. All commercial transceivers do the same - short tail, unfused, connect to the body. Why? Eliminates a ground loop and the problems in the article I linked to. Given their commercial transceivers are built to a far higher standard I am inclined to believe the short unfused ground wire to the nearest point on the vehicle is the correct solution and have installed a Kenwood TS480SAT, a 200W Kenwood TS480HX, and Icom 7000 and a Kenwood TM-D710 dual bander that way all without any issues. I can drive out in the countryside with the preamp on and get absolutely no interference at all from the vehicle. I can and have had conversations on 10m both on FM and SSB with the meter reading S0 with the other end being quite clear to listen to.

Thank you soooo much for this most informative information. I will head your advise. I asked the guy (the only guy) at the electronics shop where I have to buy my supplies about the power rating of the RG-8X. He said It would be fine. Oh well, I'm out $35.00. He had some lmr-400 with N fitings and said he had adapters to convert them to PL-259, but that stuff is so big and stiff I doubt I could make the bends needed in the cab of my truck. I guess I will look on-line. Thanks again.

 

[Mudfoot]

It's nice to hear from dudes that have been there and done that.

I'd stay away from adapters. LMR-400 comes in a flexible option. Belden 9913F7 is a good choice as well.

LMR-240, as suggested, is what I'd use.

 

[fogdog]

Thanks, Yeah that's what I told him. I'm looking at some LMR-240, and 400 with the pl-259 already on them. Just need to figure out how long each one needs to be. I should have followed my instinct, and got it in the first place. Live and learn I guess.

 

[psycho]

Well I put it in cuz the wifes likes to listen to her radio while she cooks, or puzzles, and I like to eat, and the radio being so close to the kitchen was causing serious bleed over. Happy Wife happy life! In an attempt to cure this I installed this filter. Which didn't do anything, but for some reason it lowers my swr a bit, so why not.? my pickup is my Shack lol! I just drive the truck down our road a bit, and it's all good.

73

Gotcha!

 

[psycho]

Yep, I changed my coax from antenna to lmr240 recently and did notice a difference as far as noise levels were concerned. In also use lmr400 for all my jumpers. Lmr240 will work just the same. I just happen to have some extra lmr240 and 400 so I used it. I just did a coax upgrade for a friend of mine that runs a yaseu ft101 with an amp (800 watts pep), he too was seeing a spike in swr readings and he was using rg8x (100ft), changed the coax to 100ft of lmr240 and he is a very happy camper now. M0GVZ is correct IMO, when you start adding a lot of power, everything has to be in tip top shape , if not it shows. Get some good times microwave lmr240uf (uf= ultra flex) and you should be good to go. I didn't think it would make much difference until I tried it. In my own experience, the lmr240 does a better job hands down. JMO. I know a lot of people will say the difference is so small, but believe me it makes a difference. Good luck and hope you get it sorted. God bless

What kind of vehicle do you have your Sirio mounted on?

 

[M0GVZ]

Cobra/Uniden isolate the board and chassis at DC. Where is your elbow?

No they don't. The President Lincoln also callled the Uniden 2830 I'm currently in the middle of realigning doesn't unless the Fluke 87V meter I'm using is lying to me. In fact they even put solder pads around the screw holes to make sure the board is well grounded to the chassis.

Doesn't look like DC isolation of the chassis and the board to me. As you can clearly see from the picture the negative wire from the power socket is soldered to the same thick trace that the PCB securing screw goes through, the one that screws into a metal tab protruding from the chassis.

And here's a Cobra 148 as well so that's at least one Uniden and one Cobra radio which grounds the board to the chassis.

Where is your arse?

 

[GnG8d]

No they don't.

Yes they do, you can't tune/align a Cobra radio using chassis ground, you have to use board ground. Since the Cobra 29/25 and Uniden 68/78 are largely the same radio, I added Uniden too even though I've never owned a Uniden. This is exactly what was being said by the Galaxy guy that AL567 talked to.

edit____
I just pulled out a Galaxy929 and the board is isolated from the chassis on that radio too, so I'm not sure where that Galaxy tech was going with his comment.