Coax length on mag mount question

[Redbeard U812]

I don’t have “hash” to clear out, and I still think a couple contacts in the lower 48 doesn’t say much.

dledinger,

We have been trying to help you with your "why" question. It's quite clear.

 

[2NC995]

Redbeard - The question is and has always been about the relationship between coaxial cable length and magnetic mount antennas.

I haven’t seen you post anything on the subject, unless you snuck one in somewhere that I didn’t notice.

If you have something to contribute on the subject, please share. Otherwise I think it’s fair to conclude you’re pissing in the wind because you don’t really have anything relevant to say.

 

[Redbeard U812]

Good grief, if that mag don't make good bond only thing is the coax. If not enough coax, you get LIP BURN.

Only trying to give sound advice about proper grounding. I had the same shit out of mag mount years ago. I don't advise drilling hole in roof. I may some day. Hard mount on headache rack. Ran wilson silver loads for years, then found 102" to be king. I bond all body panels, ground all equipment.

Not saying that's your fix. But mag mounts just don't bond.

 

[2NC995]

Thanks for sharing your thoughts on the subject.

There isn’t a “fix”, really...I just leave the jumper in until I get tired of looking at the magnet, and then put a mount on.

That’s what I didn’t want to get hung up on - jumping to a solution - because that’s the easy part.

A lot of smart folks contributed to this thread and I greatly appreciate that, but it’s glaringly obvious that even among them the theories don’t align 100%.

 

[357magnum]

First I'm not like my Good Friend " Bobby " Ain't drilling no hole in the roof of my Lariat that's the same year as his ! Sorry that's not me ! I re-bond everything when I install my equipment , finishing up Lariat now before I key a Mic ! But if it " Ain't Broke , Don't Fix it " ! I can talk as far as anyone else ( believe it or not ) I have made many contacts across the pond & US is NP @ All . So like Ripley say's " Believe it or Not " I chat as far as I want . First contact 28am on the Magmount on Dx was Tn . hard for me on that channel another bowl on my end , so it impressed me . I have only Old Junk , Xtra channel Cobra 140GTL , Old Blue Turner +2 Mic and my King Bee 250 amp that's over 35 years old & never been touched . Works for me I'm Cheap ! Slo , I always raced a 69' BBC Chevy Chevelle SS ( 3 all total ) but towed it to the track w/ a Ford ! 73 & God Bless , Leo

 

[2NC995]

First I'm not like my Good Friend " Bobby " Ain't drilling no hole in the roof of my Lariat that's the same year as his ! Sorry that's not me ! I re-bond everything when I install my equipment , finishing up Lariat now before I key a Mic ! But if it " Ain't Broke , Don't Fix it " ! I can talk as far as anyone else ( believe it or not ) I have made many contacts across the pond & US is NP @ All . So like Ripley say's " Believe it or Not " I chat as far as I want . First contact 28am on the Magmount on Dx was Tn . hard for me on that channel another bowl on my end , so it impressed me . I have only Old Junk , Xtra channel Cobra 140GTL , Old Blue Turner +2 Mic and my King Bee 250 amp that's over 35 years old & never been touched . Works for me I'm Cheap ! Slo , I always raced a 69' BBC Chevy Chevelle SS ( 3 all total ) but towed it to the track w/ a Ford ! 73 & God Bless , Leo

I own two quad cab dodge ram pickups. One wearing a stud mount in a delrin insulator, and the one in this subject having a mag mount.

There’s zero apparent difference in the TX/RX abilities of the two trucks.

I imagine there’s probably millions of W1000s, 5000s and Strykers our there...the overwhelming majority of which are functioning without issue.

 

[2NC995]

If I’m totally fair and forthright I’d advise that I was warned by PM when making this thread - prior to a single response - that I’d be accused of all kinds of things, including violating “...the wisdom in the writings on the restroom walls of the restroom at your local Truck Stop”...

That’s the most sensible response I’ve received to date!

 

[S&W357]

CB Wars over Hallowed GROUND...and not even over the radio airways

Hang tough Dan & stick to your guns (magnet)

 

[357magnum]

" d " worry about nothing , if you have a Good Ol' Boy & a Swamp Yankee covering your back ,it's all good now we are a team & work together . Whoda Thought ? Just me & my friend I guess ? Waiting for a lock , No disrespect to the forum , I am what I am ! 73 & God Bless , Leo

 

[S&W357]

Good Ol’ Boy

 

[357magnum]

Yup & I " Ain't Got No Good Sippin's like Knob Creek ! I guess my old friend " Jack" will have to work ! BTW " Jim's on Deck " !

 

[357magnum]

BTW , Biggest Pure Bred Swamp Yankee here ! Some may know what this is all about ... That's why we have Google !

 

[M0GVZ]

1. The antenna is not “barely” working,

2. My radio isn’t next in line.

It'll continue down the line until there's enough of a source to allow the amount of current to flow in the groundplane that is needed.

Kirchoffs Law: Current flowing into a node (antenna feedpoint) must be equal to those flowing out of it.

So as current is flowing out of the antenna feedpoint into the antenna then current flowing into the feed point from the ground plane must be the same. As the coax braid is connected at the antenna feed point to the part of the antenna system that is to provide the current to flow into it then if the ground plane isn't sufficient to allow that current to flow then it'll use as much of the coax and whatever is down the chain on that to.

Get a RF ammeter. Clamp it round the coax. See what it reads. If it is anything above zero then your coax is being used as a RF ground. As you move the RF ammeter further away you should hopefully see it eventually reach zero but if you have a really poor RF ground you may find that you get as far as the radio, it still isn't zero and then you have to start measuring down any cables coming from the radio such as power and mic cable. You would find if you put in line a good RF choke at any point in the coax where the ammeter was showing above zero that your antenna tuning would alter and the nearer the antenna feed point that choke was the more pronounced the change.

 

[2NC995]

It'll continue down the line until there's enough of a source to allow the amount of current to flow in the groundplane that is needed.

Kirchoffs Law: Current flowing into a node (antenna feedpoint) must be equal to those flowing out of it.

So as current is flowing out of the antenna feedpoint into the antenna then current flowing into the feed point from the ground plane must be the same. As the coax braid is connected at the antenna feed point to the part of the antenna system that is to provide the current to flow into it then if the ground plane isn't sufficient to allow that current to flow then it'll use as much of the coax and whatever is down the chain on that to.

Get a RF ammeter. Clamp it round the coax. See what it reads. If it is anything above zero then your coax is being used as a RF ground. As you move the RF ammeter further away you should hopefully see it eventually reach zero but if you have a really poor RF ground you may find that you get as far as the radio, it still isn't zero and then you have to start measuring down any cables coming from the radio such as power and mic cable. You would find if you put in line a good RF choke at any point in the coax where the ammeter was showing above zero that your antenna tuning would alter and the nearer the antenna feed point that choke was the more pronounced the change.

Ok, post got off track with some distraction...

Thanks for taking your time to post. This has been educational for sure.

My comment which was previously quoted wasn’t accurate, but was also missing context. My point was not that the RF ground - or the capacitive coupling between to the vehicle - was 100% effective. I think that’s obviously untrue, although only showing it’s head with the shorter feedline. The whole point of the post was to understand how the symptoms are more or less masked with the longer coax.

What I intended to say was rather that the antenna system, with Wilson’s factory length coax, seemed to work rather well. In comparing this with my other pickup (hard mount) I can’t readily observe any difference in TX power. Granted that a CB radio S meter can only provide so much resolution, but for practical purposes, the magnet mount is no significant handicap in TX or RX...at least as far as I can witness.

 

[Road Squawker]

... edit...
Kirchoffs Law: Current flowing into a node (antenna feedpoint) must be equal to those flowing out of it.
if the ground plane isn't sufficient to allow that current to flow then it'll use as much of the coax and whatever is down the chain...

put in line a good RF choke at any point in the coax ....

DAYUM,.......... Perhaps there is a reason that an added RF choke on those A99's/IMAX's works better when located about 1/4 wl below the feedpoint