Sirio 5000...two questions

[milkman21218]

222 DBFL, It really looks good. The fatter whip should increase the bandwith. And thanks for giving the drill bit size.

 

[222DBFL]

No worries just passing along something that someone may want to do in the future if the stock whip isn't working out. It was something I wanted to do and it worked well. I don't think I will have any issues with it flying off either, and I will do some more testing and post my results back after I get some use out of it , but thus far it's working great and was easy to mod. The drill bit size of 13/64 is the perfect size and doesn't leave any wiggle room. It's a nice tight fit. Thanks for all the replies and i will keep everyone updated. God bless.

 

[M0GVZ]

Here's W5LZ's post.
Also,I wonder why Mr. mercurio made the statement about if the vehicle has a sizable roof area that it can be used as a ground plane and not the coax. Anybody want to chime in here?

"In fact if the magnetic mount has a correct surface, is the roof to work as ground plane and not the cable"


Correct surface,meaning the vehicle roof and not some other part of the vehicle.

I'll throw in my 2 penneth...

Basically if the RF doesn't have a good enough ground/return path it'll take the path of whatever it can prioritising the path of least resistance first and that is outside of the coax braid.

On a mobile installation with a correctly installed antenna the RF flows over the surface of the vehicle, in this case the roof, and not down the coax.

It would seem that Mr.Mercurio is a realist and understands that a number of installations will be the most half-assed you are going to find (magmount on a biscuit tin or the refrigerator type or just thrown on the roof of an outside shed) and that the coax is likely to be the path taken for the ground and therefore that is possibly why the lengths were chosen.

 

[Lil'Yeshua]

Well,I'm actually learning about this stuff. I've heard one guy using his tool box as a ground plane and it was working for him.

 

[M0GVZ]

222 DBFL, It really looks good. The fatter whip should increase the bandwith. And thanks for giving the drill bit size.

It won't increase it that much and its already going on for a couple of MHz wide which is quite good considering the efficiency.

Taking a bog standard vertical, using 2mm diameter element you're going to have a bandwidth of 900kHz < 1.5:1

Increasing that to 10mm you're looking at around 1.1MHz <1.5:1, just a 200kHz difference.

Now that itself is maybe worthwhile if you're building a base station antenna but for a mobile antenna given the problems it causes then the gain in the bandwidth isn't worth it. It would be far heavier, pretty much inflexible and the mounting solution would be a lot more complicated.

The 145 Mag mount is a very strong mount. Not like the Wilson 5000 mount. It should still work very well.

Unfortunately part of how strong a magnet sticks to something is how thick the metal is that it is sticking to. When you see them being demonstrated in stores and at hamfests they're typically attached to a thick steel plate which is a lot thicker than the roof of a car and certainly a hell of a lot thicker than the roof of a modern car.

I know for certain that a Sirio 145 mount with a Yaesu ATAS120 on falls off the roof of a 2004 Chrysler Grand Voyager at 70MPH. Been there, done that.

Well,I'm actually learning about this stuff. I've heard one guy using his tool box as a ground plane and it was working for him.

There's various definitions of "work", many of which are no more than "do I have low SWR and can I make contacts" which doesn't tell the whole story. You might be making contacts but are you making as many as you could be and do you get a lot of noise you needn't do because of common mode and ground issues?

Using one of those toolboxes you typically find in the bed of an American truck is probably going to turn out OK other than the body of the cab masking the antenna possibly causing some matching issues.

 

[The DB]

When it comes to antennas mounted on toolboxes there are a lot of factors in play. Some toolboxes have better electrical connections to the rest of the vehicle than others, and some don't even have good DC connections. Whats worse, these connections look very different to a high frequency AC RF signal where a DC short can look like an open circuit and a DC open circuit can look like a dead short.

I think a lot of people also simply hook them up and see them work somewhat well and assume that all is well, not realizing that they could significantly improve their setup with a few machine screws, some star washers, and some copper flashing/braid.


The DB

 

[222DBFL]

I am in no way trying to win any contests or anything, I was just passing something along that worked for me. It may not work for the next person, but did for me. I took into account the added weight and compensated by adding 5 5" magnets to the underside of the roof below where the 145 mag mount sits. I promise you that it isn't moving. Inhale been to highway speeds of 70 now and no issues. Like I said I bent the whip back until it was about parallel with the roof as well to test the magnets strength. It holds. It was never about increasing bandwidth, only to try and improve over the stock whip, which it seems to be doing this fine. Swr readings are actually a little better with the larger whip. 1.1-1.2 across the whole 11m band. I could probably tweak the whip a little and get the swr readings down but nobody on the other end is going to notice the difference. I have made and also inquired from the same people I talk with daily and have not had any reports of signal loss and I have been talking dx today as well. Like I said I was just simply trying to pass some info along that may or may not help some one else. God bless and happy holidays to all. 73's.

 

[Robb]

I've been using the Wilson mag mount with a Sirio antenna, drove more than 12,000 miles across country and never had a problem.
Except for low-hanging branches, that is . . .

 

[Lil'Yeshua]

When it comes to antennas mounted on toolboxes there are a lot of factors in play. Some toolboxes have better electrical connections to the rest of the vehicle than others, and some don't even have good DC connections. Whats worse, these connections look very different to a high frequency AC RF signal where a DC short can look like an open circuit and a DC open circuit can look like a dead short.

I think a lot of people also simply hook them up and see them work somewhat well and assume that all is well, not realizing that they could significantly improve their setup with a few machine screws, some star washers, and some copper flashing/braid.


The DB

If I remember correctly,the guy had a predator w/magmount stuck to his roll around toolbox sitting in his garage. It was just temporary but he was getting out. Plus he had a linear somewhere in the rf chain.

 

[M0GVZ]

If I remember correctly,the guy had a predator w/magmount stuck to his roll around toolbox sitting in his garage. It was just temporary but he was getting out. Plus he had a linear somewhere in the rf chain.

He probably was. You'd get out just throwing it on the roof of the shed. I have a 2/70cm dualband antenna on a magmount stuck to the radiator in my living room so I can use my HT to access a local repeater and it does but I'm under no illusion its working well. It'll make the local repeater but compared to using 5W into the hard mounted 1/4 wave on my car which can hit a repeater 55 miles away, its performance is dire.

If he was using a linear I hate to think how much RF was on his audio. 5W into a properly installed Sirio 3/4/5000 will get you a good 30 miles without hills in the way.

Compromises should be used when there's no other option available because any antenna is better than no antenna but they shouldn't be used just because they're an easy way out. Sadly too many antenna installations I see on vehicles, whether it be amateur, CB or business VHF such as taxis, are done taking the easy way out.

It takes half a day tops to do a good antenna installation and it'll outlive and outperform any botch job and you'll not waste far more time trying to stop stuff like electrical noise or the car electrics going whacko every time you key the mike.

 

[milkman21218]

145 Mag Mount

I run a Sirio 5000 pl with the 145 mag mount on each of my vehicles. A 2004 Chrysler Town & Country Touring and a 2008 Chrysler Town & Country Touring. And I often drive over 75 mph (up to 95-100). And I have never had either mag come off or move. I do run a tri - mag mount on my High Sierra Sidekick 2. I would never put a tall thick screwdriver antenna on a single mag mount. But each to his own!

 

[222DBFL]

Milkman21218, it works and I only did it because of the added magnets on the underside, my 145 mag mount is solid man, even with the larger diameter whip it's solid. I would not have done it if I thought it would not have worked as far as weight was concerned anyway. Like you said to each his own. I did make contact with another station 70+ miles away this morning, from port orange, fl to west side of Ocala, fl. Seems like the larger whip is working well for me anyway as I have never talked that far locally in my mobile. It's flat down here and to talk that far and hold a good conversation was pretty neat I think , for a mobile with a magnum 257hp and a sirio pl5000 with a 102" ss cut whip. Anyway, thanks for all the replies and concern. It is very much appreciate from all as I am learning something new everyday. God bless and happy holidays.

 

[M0GVZ]

Yeah that's working great for you if you got that range.

We were just concerned about using it and it falling off whilst you're driving down the road. Quite a lot of people don't pay attention to stuff like this and as far as they're concerned as long as it sticks when they plant it on the roof then its OK in their minds but those magnets on the underside will definitely solve the problem.

Hopefully with the higher HF bands in the shape they're in it won't be too long before you get your first 3000 mile contact. Its certainly possible with what you've got.

 

[222DBFL]

Yes sir. I have made sure the antenna isn't going to come off, even went through some trees at faster than I normally do and all is well. The magnets on the underside are key to it working like it does. I am not much of a gambling man so I tend to err on the side of caution. I really do appreciate the replies and that others here had concern. It's nice to be able to get some good advice and polite advice as well.

 

[milkman21218]

Like M0GVZ said you should be able to do much more with your setup. I know that you will really enjoy it. I know the Sirio 5000 is the best mobile antenna that I've ever used. And I like the fact that I can use it on both 10 & 11 meters with really great results.