Source for LMR-400 Ultraflex

[DownEastNC]

I just placed an order for a Comet CA-712EFC base station antenna. It has an N type female connector. I need about a 100' run of cable with an N male on one end and a PL-259 on the other. Can someone recommend a source for this type of cable. I would like the LMR-400 Ultraflex. If I can't get the PL-259 then I'm assuming some sort of adapter would be required???

Edit: I have found this. Good deal? https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=342_343_347_998_1415&products_id=6882

Edited October 21, 2021 by DownEastNC
Addl Info

[tweiss3]

Antenna farm is a good place to purchase. You will be sure its actually Times Microwave cable. Don't forget, you will need to weather proof the connection at the antenna after you hook up the coax.

[DownEastNC]

2 minutes ago, tweiss3 said:

Antenna farm is a good place to purchase. You will be sure its actually Times Microwave cable. Don't forget, you will need to weather proof the connection at the antenna after you hook up the coax.

Thanks! As far as weather proofing, do they make any sort of boot that covers the connector or do I have to home brew a solution?

[Lscott]

A 100 foot run of LMR 400 at 450MHz has a loss of 2.7db. That means only 53.7 percent of your power makes it to the antenna. If you run 100 feet of 1/2 inch LDF at the same frequency the loss is only 1.5 db, or 70.7 percent of your power makes it to the antenna. Whatever loss you have in the cable has to be made up by gain in the antenna at least.

[DownEastNC]

3 minutes ago, Lscott said:

A 100 foot run of LMR 400 at 450MHz has a loss of 2.7db. That means only 53.7 percent of your power makes it to the antenna. If you run 100 feet of 1/2 inch LDF at the same frequency the loss is only 1.5 db, or 70.7 percent of your power makes it to the antenna. Whatever loss you have in the cable has to be made up by gain in the antenna at least.

The gain of the Comet CA-712EFC is 9dBi, or so they say.

This is really challenging. Everybody says to get the antenna as high as possible which means more cable and more signal loss. To go with a sturdier cable means a great deal more expense. I know this is a very subjective question, but is there a sweet spot for antenna height and cable length that is budget friendly? My long term goal was to get the antenna up around 60 feet but that may be just a dream.

[wayoverthere]

1 hour ago, DownEastNC said:

Thanks! As far as weather proofing, do they make any sort of boot that covers the connector or do I have to home brew a solution?

DX engineering has a good instruction sheet on the topic, and offers kits:

https://static.dxengineering.com/pdf/weatherproofingcoax-techtip.pdf

https://www.dxengineering.com/search/part-type/weatherproofing-kits/product-line/dx-engineering-weatherproofing-kits?GroupBy=SKU&SortBy=Default&SortOrder=Default

And I'll echo @Lscotton AntennaFarm being a good reputable source. I haven't ordered that specific cable package, but had a number of other orders with them, and zero issues. I also did a little searching and didn't find any other solid alternative options with what you were looking for.

 

[tweiss3]

1 hour ago, DownEastNC said:

Thanks! As far as weather proofing, do they make any sort of boot that covers the connector or do I have to home brew a solution?

There are a couple of ways to do it. The most expensive is cold shrink wrap, which is used in about 50% of the "professionals/commercial" installs at cell sites: https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=627_656_660. At $50/each connection, its pricy.

The LMR guys like to wrap the connection in multi-layers. First tape, then a waterproofing tape/butyl layer. This is less expensive, and many LMR guys like it because after 20 years, you can still take it off and the connectors look new.

https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=627_656_657&products_id=1956

 

Good Luck! This is just 1 of the many things that Nickle and dime your installs, but its important.

[DownEastNC]

26 minutes ago, wayoverthere said:

DX engineering has a good instruction sheet on the topic, and offers kits:

https://static.dxengineering.com/pdf/weatherproofingcoax-techtip.pdf

https://www.dxengineering.com/search/part-type/weatherproofing-kits/product-line/dx-engineering-weatherproofing-kits?GroupBy=SKU&SortBy=Default&SortOrder=Default

I'm very familiar with the 3M rubber splicing tape. I was a Journeyman Electrician for a number of years and we went through miles of that stuff. Thanks!

[WROA675]

3 hours ago, DownEastNC said:

Can someone recommend a source for this type of cable

If you were local I'd say go see Ed at Wifi Expert in Valencia. Still, I would recommend you call him at 661.200.0771 or email, sales@wifiexpert.us and check out the website coaxrf.com. I got my LMR 400 coax from him, plus a pigtail for my swr meter. He has a small shop and was able to make what I needed while I waited. Very affordable (lower than other advertised products I've seen). If you call him, tell him the guy on the Harley sent you 

[Lscott]

4 hours ago, DownEastNC said:

The gain of the Comet CA-712EFC is 9dBi, or so they say.

This is really challenging. Everybody says to get the antenna as high as possible which means more cable and more signal loss. To go with a sturdier cable means a great deal more expense. I know this is a very subjective question, but is there a sweet spot for antenna height and cable length that is budget friendly? My long term goal was to get the antenna up around 60 feet but that may be just a dream.

The very high gain antennas have a narrow “beam” in a radial direction perpendicular to the antenna. If you’re in a hilly or mountainous area likely this is not what you want. The better choice is a lower gain antenna with a much wider beam pattern in this case.

In flat county side, yes a high gain antenna is good and up as high as you can get it. The curious thing with this setup is close in coverage is not so good. That’s due to the very narrow beam shoots over the top of the close in receiver’s antenna. Some guys buy a special antenna that has several degrees of “down tilt” in repeater applications to help negate the problem.

https://www.pasternack.com/t-calculator-antenna-downtilt.aspx

[DownEastNC]

34 minutes ago, Lscott said:

In flat county side, yes a high gain antenna is good and up as high as you can get it.

I am most definitely in flat country here in the coastal plains of NC. I've already committed to the Comet antenna. I actually got the last one in stock at GigaParts and they have no idea when any more are coming in.

My plan was to set a 25 to 30 foot utility pole and then have a 25 to 30 foot mast come off the top of that. So the base of the antenna will be 50 to 60 feet from ground level. The antenna is 10 foot 5 inches.

[Radioguy7268]

9dBi is really 6.5 dBd of actual gain. 6 dB is nothing to sneeze at - but for the "what am I going to get by moving up the antenna?" question - the best thing to do is model your system. Radio Mobile is the go-to for an online tool that's actual useful and doesn't take more than 30 minutes to figure out the basics.

Radio Mobile online coverage map

Once you've mapped out your proposed initial system, you can toy around with it to see what you're going to be able to cover given certain heights and gain. If you make the areas where you need it to work at 25 or 30 foot, and there's no appreciable coverage gained by moving to 50 ft, then you know it's probably not worth the trouble. If you're still not covering where you want at 50 ft - then start moving upward until you see the coverage you desire. Hint - 5 or 10 ft. height difference usually doesn't do that much. 

I've found their coverage predictions to be fairly accurate if you push the desired reliability to 99% and use realistic figures for your wattage & losses.

The antenna height should usually be figured as half the total length for a vertical omni.

 

[DownEastNC]

4 minutes ago, Radioguy7268 said:

 Radio Mobile is the go-to for an online tool that's actual useful and doesn't take more than 30 minutes to figure out the basics.

Radio Mobile online coverage map

Once you've mapped out your proposed initial system, you can toy around with it to see what you're going to be able to cover given certain heights and gain. If you make the areas where you need it to work at 25 or 30 foot, and there's no appreciable coverage gained by moving to 50 ft, then you know it's probably not worth the trouble. If you're still not covering where you want at 50 ft - then start moving upward until you see the coverage you desire. Hint - 5 or 10 ft. height difference usually doesn't do that much. 

I've found their coverage predictions to be fairly accurate if you push the desired reliability to 99% and use realistic figures for your wattage & losses.

The antenna height should usually be figured as half the total length for a vertical omni.

 

Awesome!!! Thanks for this link. It will be very helpful.

[DONE]

9 hours ago, DownEastNC said:

 

This is really challenging. Everybody says to get the antenna as high as possible which means more cable and more signal loss. To go with a sturdier cable means a great deal more expense. I know this is a very subjective question, but is there a sweet spot for antenna height and cable length that is budget friendly? My long term goal was to get the antenna up around 60 feet but that may be just a dream.

OK, while not trying to make this overly complicated, I will only mention these concepts and not the math behind them.

First off is that 3 dB of loss is meaningless when you start looking at the overall effect it has on the range of a radio system.  Consider that a CB or ham radio with an S meter registered S-1 to S-9.  The change of one S unit required the signal to change 6db.  So if you were running 10 watts and were being heard with an S-8 you would need to increase your power to 40 watts to bring the meter up to S-9.  And what did that really do to the overall signal quality?  Not much.

Here's the thing NO ONE ever brings up and involves the most math.  Path loss.  Path loss is the signal level loss though free space between the transmitting and receiving antenna's.  And it's going to be over 100 dB.  And this it where people fall flat with the idea of cable loss and antenna height.  Path loss can indeed be calculated and the attenuation levels changes depending on the medium.  The other this that no one takes into account is horizon.  UHF signals do NOT bend in the atmosphere.  They radiate in a straight line away from the antenna and once they reach the horizon they keep going straight.  No amount of power increase will change this but a height increase in the antenna does.  The other thing that the height increase changes is the medium that the signal is required to pass through.  Meaning if your antenna is 5 feet off the ground, the signal coming from it has to radiate through trees, houses, buildings, and the minute it hits a hill it's done going that way.  All of these objects attenuate the signal of block it completely.  A typical building is going to be over 30dB of attenuation.  So if the building is 90 feet tall, and to get over it requires a 3 dB loss of signal to radiate past it, then you loose the 3 dB in the cable to make up for the 30 dB loss trying to pass the signal through the building. 

 

Yes, you can over so it and place an antenna too high in the air.  But unless you have a 1000 foot tower this is a topic NOT worth discussing. 

 

[DONE]

14 hours ago, Radioguy7268 said:

9dBi is really 6.5 dBd of actual gain. 6 dB is nothing to sneeze at - but for the "what am I going to get by moving up the antenna?" question - the best thing to do is model your system. Radio Mobile is the go-to for an online tool that's actual useful and doesn't take more than 30 minutes to figure out the basics.

Radio Mobile online coverage map

Once you've mapped out your proposed initial system, you can toy around with it to see what you're going to be able to cover given certain heights and gain. If you make the areas where you need it to work at 25 or 30 foot, and there's no appreciable coverage gained by moving to 50 ft, then you know it's probably not worth the trouble. If you're still not covering where you want at 50 ft - then start moving upward until you see the coverage you desire. Hint - 5 or 10 ft. height difference usually doesn't do that much. 

I've found their coverage predictions to be fairly accurate if you push the desired reliability to 99% and use realistic figures for your wattage & losses.

The antenna height should usually be figured as half the total length for a vertical omni.

 

I too use Radio Mobile a good bit for things from 2 Meter ham radio to 5Ghz microwave links and find it to be very close to actual tested results of a system built on the numbers provided by Radio Mobile.  The comments I made before pertaining to "the math" involved in calculating path loss and attenuation is what this software uses to create the coverage plots and the point to point link signal levels.    But you need to feed it correct information for it to give accurate results. 

 

Here is the other part of what this can do but folks seem to forget it's importance.  It will also show the mobile to base signal expected signal levels.  Now with simplex operations, this is not overly important as two mobiles that are 20 watts or 2 portables that are 2 watts are going to be reciprocal in performance, in other words, if A can talk to B then B will certainly talk to A.  With a repeater this is NOT the case.  Now you are talking about antenna height differences and power differences on the level of 10 dB.  For reference a 10dB increase is basically you add a zero.  If you have 2 watts and increase it 10dB you have 20 watts.

 

So then the whole I NEED 50 WATTS for my repeater starts to show it's uselessness.  Because no matter how far your repeater may talk out, if you can't talk back to it, it don't matter cuz it will not work for you beyond that point.  And to drive that point home I was range testing yesterday while on a service call.  I went from Johnstown Ohio to Indian Lake Ohio.  I finally fell out of the system (my repeaters) at Bellefontaine,Oh.  At that point I was hearing the repeater on and off and was not consistently able to bring the repeater up.  Here's MY setup.  I am running an MTR2000 (both repeaters) one is set 50 watts and the other is a 40 watt repeater.  These are both connected to a 4 channel transmit combiner that has 6dB of loss through the unit.  This runs to a stationmaster antenna with 8 dB of gain through 200 feet of 7/8 cable and a 1/2 inch jumper to the surge suppressor.  That works out to about 3 dB of loss.  So a total of 9 dB of loss and an 8 dB gain antenna.  The air distance for this is 60 or so miles.  and it worked on BOTH repeaters equally,  so the 10 watts of difference had no noticeable effect on the range I was able to attain.  And I was talking back from a van with a 35 watt mobile and a unity gain (the little wire motorola style) antenna.  Not some high gain antenna.  This speaks volumes to the importance of antenna height. 

[tweiss3]

@WRKC935 This is also the argument (both GMRS/HAM/LMR) when one claims they want to put up a "high power repeater" or "add more power" to their repeater. The question is why? Thinking logically, at the same antenna elevation, 99.99% of your users are going to be 50W or less. It doesn't help if the repeater can get out 1000 miles your users can't use it. Most repeaters utilize good antennas (9-12db gain), and after you figure your cable losses, fittings, jumpers, duplexer, etc. you end up at a break even point, or a small amount of gain. Anything between 100W and 50W to the feedline ends up with a nearly identical in/out range and decent coverage, provided the antenna placement is decent.

For GMRS, your primary concern is build something that the duty cycle won't burn up.

[DownEastNC]

Here's the results that I got from Radio Mobile as originally suggested by @Radioguy7268.

I started out with 20w power, 10 meters / 32 feet height and 6db gain. The coverage was, let's say decent as it reached out 10 to 15 miles.

Next I doubled the antenna height to 20 meters / 65 feet height and the coverage area more than doubled out to 30 plus miles.

For my next trick I doubled the wattage to 40 and didn't really gain any coverage but it did extend out the marginal area.

I do live in a very flat coastal area, much is over water, and tall pine trees are the biggest obstacle. So I guess by just dumb luck it appears that my original desire to get an antenna up around 60 feet is the sweet spot for me and my expectations. I will try to see if I can shorten the coax length from 100' to 75' to eliminate some loss.

Thanks to everyone for your suggestions and participation and especially the education I received here. Y'all are the best!

[Radioguy7268]

60 ft is difficult without a building/tower/structure to lean on - or some guy wires. I've done some 40 ft. utility poles with 10 ft. mast, and I can tell you they do sway and move in the breeze, even with just a simple fiberglass omni, but they work. Forget the fiberglass telescoping fishing poles. More than 10 ft. of unsupported pipe/mast is asking for trouble. You might get away with it for a week, a month, a year, but you won't last through the first decent storm.

If you plan to use mostly portables - you will probably need to 'de-tune' the receive side sensitivity by a few dB in Radio Mobile to reflect real world conditions of fade, foliage, and poor portable positioning. I haven't seen too many hobby type repeater systems at 50 or 60 ft. that would receive a portable reliably at 30 miles. I usually figure portable coverage will be about 50 - 60% of what a high powered mobile would be. You might be able to key the system, but you'll always know when someone is working a portable at the fringes.  I believe the standard receive side sensitivity for Radio Mobile is set @ .45 uV - which is right around -114 dBm.  That's a weak signal, but most decent receivers can operate below that level, you just won't have full quieting. I'd want a Portable coverage map that represents something closer to -110dB for modeling on-street coverage, which would be @ .70 uV    

 

[DownEastNC]

8 minutes ago, Radioguy7268 said:

60 ft is difficult without a building/tower/structure to lean on - or some guy wires. I've done some 40 ft. utility poles with 10 ft. mast, and I can tell you they do sway and move in the breeze, even with just a simple fiberglass omni, but they work. Forget the fiberglass telescoping fishing poles. More than 10 ft. of unsupported pipe/mast is asking for trouble. You might get away with it for a week, a month, a year, but you won't last through the first decent storm.

Everything is a stepping stone to get me to the final destination. Initially my antenna rig will be quite a bit lower in elevation. Long term I am hoping to set a utility pole (power pole) and on top, attach a flag pole of whatever length, then the antenna. The flag pole I'm looking at is free standing and can withstand over 100 mph wind, anchored to a concrete pad on ground. I'm going to come up with some sort of gin pole / boom to be able to lower / raise the flag pole on a hinged support bracket. This setup is common on sail boats with long masts. Anyway, everything is on paper at the moment.

Near term I will be using my mobile KG-XS20G (20 watts) or my HT KG-935G with the intention of eventually getting the 50 watt KG-1000G as the base station.

[n4gix]

16 hours ago, WRKC935 said:

The other this that no one takes into account is horizon.

I am very cautious using "absolutes" when it should be obvious that many folks do take "horizon" into account... 

...and not just "professionals" for that matter.