Handheld HAM radio, roof antenna, & length of COAX

[mmckenna]

Would it make sense for me to just order a 50’ LMA-400 run with Type-N connectors on each end, then I can get two different jumpers one for my current radio, and one for the radio I plan to purchase in the future (Yaesu FT-400)?

It would if you can return the 150' of RG213.
If you can't, you could cut it to length and reterminate the cable with a new connector.

LMR-400 is pretty good stuff for hobby use. But be careful about asking for the "best". You can't afford the best, and it wouldn't be realistic anyway.

Finally, where is the best outlet to purchase Times Microwave cables?

There are a number of places to purchase it from if you can't pick it up for free from PRCGuy. Just make sure if you buy it, you get real Times-Microwave LMR-400, not the "equivalent" stuff that can often be cheap knock off from China.

I have had good results from The Antenna Farm on other small purchases. You can order custom lengths and connectors if you want.

 

[W5lz]

To re-cap a bit. ALL coax cable has losses. The differences is in how much loss over the length of the feed line. Loss is rated by the 100 foot lengths. So just quoting the loss figure isn't telling you much all by it's self. How long is your feed line? Next. Watch figuring with dBs! It may add up to a fairly big 'dB' level but exactly what does that mean. Or more important, how strong was that 'itty-bitty' signal to start with? Recievers 'hear' a lot better than they used to and that means that a little attenuation in the signal strength isn't gonna hurt a thing It might even keep your receiver from over-loading.

 

[rapidcharger]

There are so many things in this post that I want to comment on.
First of all, the obvious elephant in the room. You're using a portable with a base station antenna. Unless you're amplifying that (which wouldn't make sense to do) You're going to lose most of your power in that long of a run. You may make up for some of it with a high gain antenna but using a portable with a base station antenna is a not a great idea to begin with. I generally advise new hams not to skimp on things like antennas and feedline and to do that right instead of the radio but in the case if you don't have it in your budget for a mobile or base radio, you should keep use to a minimum and try to put as little stress as possible on the antenna connector until you do.

Second of all, whoever suggested that that much RG-213 equivalent wouldn't be lossy should lose their job if they knew how you were going to use it.

Third of all, LMR-400® is certainly not the best you can buy however the price point for the next up form there (LMR-600 equivalent) is hard to justify the added cost. Then from there you have Heliax® hardline ranging in size from 1/2" on up to 1 5/8" which costs around $10 per linear foot.
So yeah, you can do better than LMR-400® but the benefit from 400 to 600 isn't that substantial considering the cost goes from around 35 cents a foot to nearly $4 a foot and then you got shipping on it because ham stores typically don't stock anything larger than an "LMR-400®" equivalent.
So in summary, I personally believe that for that length, an LMR-400® equivalent is the best value considering it's not that much more than LMR-240 or RG-8X or many of those much lossier cables you don't want. There's a local ham here who pleads with me to switch out to something better because I run 150-200' of it myself but the performance suits my needs and the next step up from there is much more expensive.

I keep using the registration mark and saying "equivalent" because LMR-400 is a registered trademark of Times-Microwave Systems and is by no means the only brand of low loss .405" coax you can get. For example, you can a number of other brands like Davis DRF-400 which has the same attenuation and power handling capacity as the Times Microwave brand and Belkin 9913 which is allllmost the same. There are also other no name brands some of it, I suspect comes from China.

N-connectors a nice but you're going to have insertion loss going from your portable to an adaptor to an so-239 connector on an antenna. In the ham world, UHF connectors are far more common and you will be questioning why you did that eventually.

Things I would prioritize if I were you. Exchange the lossy coax and get yourself a mobile or base rig and power supply, preferably linear regulated and not switching but that's not critical at this point.

 

[cmdrwill]

They had a ton of genuine LMR400 and 600 cable at the Claremont Ham swap meet yesterday.

 

[Golay]

Very good advice in this thread. I just want to add one more thing.
In your original post, you said you are going to do a chimney mount.
Try to not have the straps from the mount dig directly into the brick and mortar.
If possible, put some angle under the straps like in this picture.
The picture says angle iron, but there's really no reason I can think of why it couldn't be aluminum angle.

 

[Ubbe]

Also remember that the closer the upper and lower mount on the chimney are the more force it will put on the chimney. So try and go as high and low as possible on the chimney, but not on the top or bottom brick layer as that probably have concrete on only one side. But those angled irons will distribute the load over a larger area, if they are thick enough, and are a good addon for all chimney mast pole work.

/Ubbe

 

[jim202]

One other point that has not been mentioned on here about chimney mounts is that the antennas can cause vibrations to crack the mortar over over time. The larger the antenna and the closer the straps are, the more this problem will show itself.

So the idea of using some angle to spread out the load bearing surface, the better you are.

One other suggestion I would add is to take a file and round the sharp edge of the back side of the angle pieces being used. This will help in the long life of the straps not going over a sharp right angle bend. You don't have to do the whole length, only where the straps will be.

My last comment about any chimney install is, the more complicated it becomes, the more you will require help in doing it. Using 4 sections of angle on the side of the chimney is not something just one person will be able to pull off. Then you need to get all 4 sections at the same height on the chimney for your straps to match up with the rounded places. You might consider using a rope and being able to put enough tension on the angles to hold them in place while you work with the straps.

Another item you probably have no idea about is how long of straps will be required to go all the way around the chimney and into the bracket to tighten them up? You might want to try going up to the chimney and using a tape measure to get the length you need. You can try to use a small rope with a weight on the end that you try throwing around the chimney. The other way is to get to the top of the chimney and then you should have full control of your tape measure. Just try not to put too much pressure sideways on the chimney if your leaning a ladder against it. You can crack the mortar joints and then be in real trouble.

Not trying to scare you on this project, but these are the facts your going to have to deal with in your efforts to install your antenna on the chimney.

 

[prcguy]

The angle iron is an excellent idea and I did that on a home made chimney mount in the late 70s that used 3/8" steel cable and huge turnbuckels to hold up 21ft of fence post with a 22ft antenna on top. I did drop the angle iron a few times until I used a rope to secure it while assembling the mount.

I would otherwise not be too concerned using a typical chimney mount with wide straps. A stock unit would never be able to tighten enough to damage a chimney and if anything it will help hold the bricks and mortar together. The setup I had was a bit extreme but the chimney was huge and strong at about 6ft X 4ft and many layers of brick and mortar.

Very good advice in this thread. I just want to add one more thing.
In your original post, you said you are going to do a chimney mount.
Try to not have the straps from the mount dig directly into the brick and mortar.
If possible, put some angle under the straps like in this picture.
The picture says angle iron, but there's really no reason I can think of why it couldn't be aluminum angle.

View attachment 80543

 

[SoCalSearch]

Thanks everyone for your input, this has been really helpful. I plan on getting up on the roof soon to determine what length of cable run I will need and then review the chimney mounting system I have.

 

[schling66]

Out of curiosity, why were the dB loss numbers different in prcguy's and mmckenna's initial posts? I see that mmckenna was using KV5R's loss calculator, and it seems that prcguy was using one of the many other calculators or charts that I found out there that put the loss for RG-213 at 100' and 400-450 MHz at around 5.2 dB. Is the much higher loss given by KV5R's calculator attributable to the difference in manufacturer (i.e., KV5R is giving numbers for Belden's version of RG-213, as opposed to Times-Microwave RG-2130)?

 

[mmckenna]

Out of curiosity, why were the dB loss numbers different in prcguy's and mmckenna's initial posts? I see that mmckenna was using KV5R's loss calculator, and it seems that prcguy was using one of the many other calculators or charts that I found out there that put the loss for RG-213 at 100' and 400-450 MHz at around 5.2 dB. Is the much higher loss given by KV5R's calculator attributable to the difference in manufacturer (i.e., KV5R is giving numbers for Belden's version of RG-213, as opposed to Times-Microwave RG-2130)?

Good question, was wondering if someone would ask that.

The "RG" standards are just that, standards. There's going to be variations from manufacturer to manufacturer. One brand can simply meet the standard, another might exceed it.
The issue with the coaxial cable calculators on line (at least most of them) is that they are limited to only a few specific brands.

As someone once told me, "The nice thing about standards is that there are so many to choose from.".

 

[W5lz]

Somebody already said it, the -best- length of feed line is whatever it takes to get from here to there. Add a few feet for all the bends/bumps etc. between here-n-there, then another couple of feet just to be safe and that's how much you need. What do you do with some of that 'extra' feed line? Depending on what like it is, just hide it somewhere. For coax it doesn't hurt to coil it up. That doesn't work so well for ladder line, so zig-zag it a little. It ain't never going to be exactly right, so live with it...

 

[iloveantenna]

150feet is a long area, and there are chances to loss your signals. In this situation, you need an LMR400 cable for minimum loss as compared to regular cable. I suggest you to an MPD Digital coax jumper for HAM or CB radio. It has silver-plated connectors and Teflon dielectrics with minimal signal loss. This is the perfect option for you.

 

[WB9YBM]

I purchased the 150' coax because I did a very rough estimate of the run I need at home and I asked the gentlemen at the store if I will hjave any issues with loss of signal. They said I would not, but I wanted to come on here and ask. If I do run the risk of losing signal, I'll do a much more accurate measurement of exactly the length I need. If it's no big deal, I'll just use the 150'.

I've noticed that the actual power loss versus what's shown in the spec's can vary quite a bit. A good example is 50' of Radio Shack RG-8 I used on 220MHz: I measured 25W coming out of the radio and 24W coming out of the other end of the 50' run, a lot better than the spec's I've seen!

 

[jwt873]

I think one thing that's overlooked when discussing coax is the intended use. Do you really need 'the best' in every instance?

I'm active on the 2m and 440 AMATEUR bands. I chat on local FM repeaters and I also do weak signal SSB/CW.

For FM, I have a cheap Jetstream dual band vertical on top of a tower fed with 60 feet of RG-8. I've never measured the loss because I don't care. I can reach all the local repeaters with it. I also use this dual band AMATEUR antenna for general scanning. With the RG-8 coax it works great for listening to other services such as Air, GMRS, FRS and LMR.

For VHF/UHF SSB/CW, it's a different story. I have long boom Yagis. (13 elements on 144 mHz and 19 elements on 432 mHz). I feed them with Andrew 7/8 Heliax.

 

[mmckenna]

I think one thing that's overlooked when discussing coax is the intended use. Do you really need 'the best' in every instance?

Yep, good point. It's nice to squeeze all the performance you can out of your system, but reality/budgets get in the way. 60 feet of RG-8 would work just fine in a lot of instances.

I just had to toss up a very temporary install and used 100 feet of LMR400, and that wouldn't have been my first choice. But it worked just fine.
I ran my first GMRS base on 50' of Radio Shack RG-8, because that was what I had at the time, eventually replaced it with 1/2" Heliax.
When I was a kid, I ran my scanner off about 40 feet of RG-58. Didn't work great, but I could hear local stuff.

It's easy to recommend high spec stuff when it's not our money.

 

[ladn]

It's easy to recommend high spec stuff when it's not our money.

That's the gov'ment way !

 

[W5lz]

To re-cap a bit. ALL coax cable has losses. The differences is in how much loss over the length of the feed line. Loss is rated by the 100 foot lengths. So just quoting the loss figure isn't telling you much all by it's self. How long is your feed line? Next. Watch figuring with dBs! It may add up to a fairly big 'dB' level but exactly what does that mean. Or more important, how strong was that 'itty-bitty' signal to start with? Recievers 'hear' a lot better than they used to and that means that a little attenuation in the signal strength isn't gonna hurt a thing It might even keep your receiver from over-loading.

So, the simple answer to length of feed line is as short as is practical. Get what you can afford (simple isn't always affordable), cheaper is better till it ain't no more. You have to decide when it isn't.

 

[K9DWB]

That's the gov'ment way !

I'd love to be able to spend other people's money.