Sirio MAG 145 PL mag mount

[Smokinone]

I just bought one of these as the trunk mount Wilson 1000 I have doesn't fit my 5 door Suby. I took a little drive the other day, and although I do have a 2 meter in the car, I never put a CB in. This I hope will do the trick. It has a bigger magnet, width wise, than the Wilson mag mount so it should be stable.

On that note, I also noticed a vacancy of truckers on the road, and a lot of the trucks I do see don't seem to have CB antennas on them. Quite a lot different than pre-pandemic traffic wise.

Anyway, I took some pics of the thing, and it looks like it may be able to easily be modified for RG8X coax instead of the RG58. The removable rubber base protector is good and bad. Seems a little flimsy and thin, but time will tell. But there is a gasket between the SO239 and mag base, and easily comes apart with 4 screws. A little hot glue to keep the elements out. The SO239 appears to be crimped to the mount and ground where the copper connector is.

This mag mount is my solution to 2 cars without CB's, and an easy way to move antenna and radio around between the 2 cars. My truck has permanent radios and mounts. I just hope there's enough steel in the cars to support the antenna







I'm not advertising for or against these, just though there might be an interest if anyone was thinking of a mag mount. I have seen a few utubers changing out the coax in the Wilson mounts which appears to be more invoved than these would, and the replaceable base gasket may be a plus.

 

[L2]

I didn't want to drill holes in my new vehicle so a Mag 145 works great with a Sirio 5000 Performer antenna.

 

[Dr_DX]

IMHO,

I would use RG-400 that is a 1/2 wave length for the frequency you are using it on...

Even if you use RG8X, you should use a 1/2 wave length... Rather than the 4m that comes with these.

 

[Smokinone]

IMHO,

I would use RG-400 that is a 1/2 wave length for the frequency you are using it on...

Even if you use RG8X, you should use a 1/2 wave length... Rather than the 4m that comes with these.

Although the RG-400 is pricey, that's a good idea. It appears to be well suited for mobile installs, with the double shielding and almost indestructible core. I've just watched a video where the guy was using a small torch for PL259 assembly.

The reducers used for the RG-400 are for RG58, UG-175/U

I think the Wilson mounts have 17 ft of coax, I think the short coax on the Sirio is complained about from many. I'll get it on the car and see how the SWR turns out before I make decisions on coax changes for the moment.

 

[Dr_DX]

Obviously, if it doesn't reach, everything else is a moot point.

RG400 (69.5/70 VF) 1/2 wave length will be around 12.5' @ 27.205 Mhz give or take a couple of inches depending on what channel you want to talk on.

RG8X has a lot more fluctuation in VF depending on the manufacturer, everything from 72 to 82 VF. The most common is around 78, which would make a 1/2 wave length around 14' @ 27.205 Mhz.

Always use an analyzer if you have one, to make your 1/2 wave length coax. It will be more accurate than any software program that will be based on published specs.

Good Luck!

 

[Smokinone]

Obviously, if it doesn't reach, everything else is a moot point.

RG400 (69.5/70 VF) 1/2 wave length will be around 12.5' @ 27.205 Mhz give or take a couple of inches depending on what channel you want to talk on.

RG8X has a lot more fluctuation in VF depending on the manufacturer, everything from 72 to 82 VF. The most common is around 78, which would make a 1/2 wave length around 14' @ 27.205 Mhz.

Always use an analyzer if you have one, to make your 1/2 wave length coax. It will be more accurate than any software program that will be based on published specs.

Good Luck!

I was wondering about the length and wave length. I noticed the length of the RG-400 is shorter than the RG8X @ 1/2 wave and was wondering if my thinking was wrong on half wave lengths etc.

Thank you for info on that. I do have an MFJ analyzer. I will just need to drag it out and see how it looks. I did find an 8X cable that showed no issues with an VOM as far as shorts, but when I hooked it to the MFJ, it did show a short or something goofy with the cable. Depending on which end I plugged in I got the bad reading, one end was good, and one was bad. Changed the PL259 and all was well. I had made the cable up before I had the MFJ, and now just getting back into the hobby, I find myself using it more. Does a lot more than I know at the moment.

Thanks again.

 

[w9cll]

I was wondering about the length and wave length. I noticed the length of the RG-400 is shorter than the RG8X @ 1/2 wave and was wondering if my thinking was wrong on half wave lengths etc.

Thank you for info on that. I do have an MFJ analyzer. I will just need to drag it out and see how it looks. I did find an 8X cable that showed no issues with an VOM as far as shorts, but when I hooked it to the MFJ, it did show a short or something goofy with the cable. Depending on which end I plugged in I got the bad reading, one end was good, and one was bad. Changed the PL259 and all was well. I had made the cable up before I had the MFJ, and now just getting back into the hobby, I find myself using it more. Does a lot more than I know at the moment.

Thanks again.

Coax lenght makes little difference, 1/2 wave length is an old wife's tale. Just use the shortest run you need and don't coil it up.

 

[Easy rider]

Watch how far the solder joint is in relation to the hole in the brass tab. Have one presently that had been soldered too close to the screw hole and had squashed a little of the plastic that holds the brass threaded nut in basement tightened up
Whilst it did work on continuity test its not ideal.
Seen this before too.

On other bases I have I use beryllium washers to improve the connection hopefully as it adds a v thin thickness more of a shim to the connections hopefully improving the path.
Once fitted rg 8 to a 145 base but saw swr rise slightly although worked well.I
Good luck.

 

[Dr_DX]

Coax lenght makes little difference, 1/2 wave length is an old wife's tale.

LOL A lot of very well known Hams say otherwise... But to each his own.

True, length make little difference in regards to everything except - how your SWR meter reads at the opposite end from the antenna. And if that is what you will be looking at, then it makes a big difference...

 

[Smokinone]

Couldn't get a good SWR using the mount with the Wilson 1000. Just to play, I will try different coax at a 1/2 wave. The 5 meter (16.4ft) of the RG58 may be at issue since the Wilson magnet has 17 feet of RG58. Which tuned OK with the trunk mount, and with a roof mount on another vehicle. Just didn't have enough whip to lengthen.

It's been some time since I played with any of this. We'll see how it goes.

At any rate, RG-400 is on the way.

 

[w9cll]

LOL A lot of very well known Hams say otherwise... But to each his own.

True, length make little difference in regards to everything except - how your SWR meter reads at the opposite end from the antenna. And if that is what you will be looking at, then it makes a big difference...

many well known hams on here and many other place agree with me.

 

[The DB]

LOL A lot of very well known Hams say otherwise... But to each his own.

So, mind linking us to where some of this "well known ham's" said this? Or was this just a crutch to try and silence the person questioning your statement.


The DB

 

[w9cll]

Couldn't get a good SWR using the mount with the Wilson 1000. Just to play, I will try different coax at a 1/2 wave. The 5 meter (16.4ft) of the RG58 may be at issue since the Wilson magnet has 17 feet of RG58. Which tuned OK with the trunk mount, and with a roof mount on another vehicle. Just didn't have enough whip to lengthen.

Don't worry about the length and just run it as short or long as needed.

 

[Dr_DX]

Couldn't get a good SWR using the mount with the Wilson 1000. Just to play, I will try different coax at a 1/2 wave. The 5 meter (16.4ft) of the RG58 may be at issue since the Wilson magnet has 17 feet of RG58. Which tuned OK with the trunk mount, and with a roof mount on another vehicle. Just didn't have enough whip to lengthen.

It's been some time since I played with any of this. We'll see how it goes.

At any rate, RG-400 is on the way.

@Smokinone - The nice thing about RG-400 is that it is the same size as RG58, so you won't have to modify the antenna for it to fit.

All of our posts are opinions and not facts, whether it is stated that way or not. I can't speak for anyone else, but my opinion is based on having my own radio shop from 1985 to 2005 and having done 100's of mobile installations during that time period - not just a handful on my own vehicles. Also, for our amateur members that have a tendency to look down on others (which I despise), I have been an extra class ham for longer than some have been hams.

FYI, here are some web sources that agree with my 1/2 wave length feedline opinion:

https://www.angelfire.com/electronic/funwithtubes/T-Lines.html

"Now suppose the line is terminated with a resistor which is not equal to the characteristic impedance of the line. Suppose it is a 50 ohm line but the termination is 100 ohms. At DC the input impedance is 100 ohms. At 1/4 wavelength the input impedance is 25 ohms. This comes from the equation

Z1 Z2 = Zo2

where Z1 is the input impedance of the line, Z2 is the terminating impedance, and Zo is the characteristic impedance of the line. At 1/2 wave length the input impedance is 100 ohms. This repeats, 25 ohms at 3/4 wavelength, 100 ohms at 1 wavelength, and so on."

Lou Franklin - Understanding and Repairing CB Radios - pages 313 & 314 "Coax Length vs. SWR





I highly recommend the book. Lou uses layman's terms to explain a lot and it is easy to understand.


Walt Maxwell - Reflections - page 2-5

" If the feed line is 1/2 wave length at some frequency other than the resonant frequency of the antenna, the resonant frequency measured at the input of the feed line will be different from that of either the antenna or the feed line. " - this is correct.

That is why it is important that the feedline is a 1/2 wavelength of the resonant frequency of the antenna so you get an accurate measurement at the input.

I can go on citing other sources but I thing you get the idea. Basically, a 1/2 wave length of coax is an "impedance repeater".

Now forget everything I or any one else has told you and remember this:

Rear Admiral Grace Hopper - "One accurate measurement is worth a thousand expert opinions."


@w9cll - I apologize for attacking your opinion - I felt you were attacking mine and it was a knee jerk reaction. I am sorry.

 

[Smokinone]

I have the Lou Franklin book. I guess I should read it again, I haven't cracked it for 15+ years. It's just in my retirement and having inherited a few things, that have peaked my interest again, not to mention world events to a degree.

I've heard the antenna coax length argument for some years, and I really haven't played around with any of this for years as well. Everyone's opinion has some weight, one way or another, the thing is, it's a hobby and as such should be fun. A lot of it is experimentation and experiences we've encountered over the years. We all should be able to express ourselves and respect others for what they have to offer. I learn alot.

In the past years, I have just cut the coax to the length I needed, and used it as is. I have really never had a problem with SWR as most mobiles I have used I went with the 102" whip and I have a Wilson Silver on my truck. On my base pretty much the same. I usually bought the best coax I could afford, usually running RG8 in both applications. But now with the situation on the Wilson 1000 not tuning correctly, I'm willing to look at different ideas, and having been able to get an MFJ antenna analyzer and time, I will experiment a little and see where it goes.

I do know that I had never thought that there could be so much to consider, and the more you look the deeper it gets. Goes way beyond seat of the pants, throw it up and key up.

I've seen a utube video on checking for the correct measurements with an analyzer, I'll have to revisit some of this as I haven't used the MFJ except for checking SWR without having to key anything up. It does a lot more than I know about at this point.

Thanks everyone.