01/23/19 13:47:28 UTC
225.875 MHz
BYRON, GA
Couple of pilots talking
 
01/19/19 18:49:59 UTC
385.55 MHz
WEST PALM BEACH, FL
Lucky 21 heading to W-168 on ZMA Discrete
 
01/18/19 02:32:40 UTC
343.500 MHz
MOLINE, IL
Refueler on AR16 Primary. “I’ll take your tail number”
 
01/17/19 15:12:39 UTC
343.000 MHz
BYRON, GA
Couple of pilots talking
 
01/15/19 13:32:19 UTC
339.500 MHz
BYRON, GA
Go for Defense 986 and another pilot in communications.
 

01/20/19 20:17:16 UTC
337.3000 MHz
E-4 Data Link
 
01/13/19 15:29:30 UTC
60.1000 MHz
Calling in strikes against ground targets at Avon Park
 
01/07/19 20:39:46 UTC
254.400 MHz
?
 
01/07/19 20:21:34 UTC
317.525 MHz
?
 
01/07/19 18:46:13 UTC
350.200 MHz
?
 
01/07/19 17:37:23 UTC
262.760 MHz
sells range
 
01/07/19 14:13:41 UTC
143.425 MHz
Night Watch Reporting System
 



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Coax and What It Means For Your Scanner Shack.

Recently I had drove past the homes of a couple Military Air Monitors. To my shock I noticed the coax they were using to connect their antennas to the scanners was very thin, probably RG-58. After thinking about this all day I stated to wonder, is this normal? Are most of our MilAir Monitor hobbyist using thin RG-58 coax? If this is so, please read this article and I'm going to give some advise that will increase your received signal strength by a factor of 3 times more than you're current experiencing.

Some people think the only time you need to use heavy, thick coax is if you're transmitting at very high power levels. True, if you're running a ham station and running 1000 watts you will need the heavier coax such as LMR-400. I personally use LMR-400 on all my antennas, HF, VHF, UHF, monitoring, and ham radio. On HF (160 meters - 10 meters) I'm running 1,200 watts (1.2KW) and on 2 meters 350 watts (1KW coming soon!). On 70cm (432 MHz) I also use LMR-400, but have no amp so I'm only running 50 watts. On 23cm (1296 MHz) I run 5/8" HardLine, again to cut down on signal losses, with this setup, 10 watts, and hardline to a 25 element 1296 MHz yagi I can work stations as far as Texas. If I used LMR-400 on 1296 MHz I would lose over 1/2 of my power in the coax that would never reach the antenna!

Not only will the heavier coax help you avoid problems of running high power it will greatly improve your received signal as well. The few MilAir monitor stations I seen were running very long lengths of coax, probably 50 to 100 feet and they were using what appeared to be RG-58. At the high end of the MilAir UHF band (400 MHz) 100' of RG-58 has 11.2 dB of signal loss (OUCH!). At the low end (200 MHz) 100' of RG-58 has 7.3 dB of loss (STILL A BIG OUCH!)

If you switch to a better quality, heavier coax you will see improvements of nearly 3 times. Example, most of my antennas are being fed with between 60 and 100' of LMR-400 (same as RF-9913) coax. At 400 MHz my received signal loss at 100' of coax is 2.6 dB. That is an improvement of 8.6 dB gain over those using 100' of RG-58. That means nearly 3 times more RF signal is reaching my scanners over using RG-58. That is a MAJOR improvement.

The LMR-400 coax is the same diameter as RG-8. LMR-400 has a solid center conductor, solid conductor is more efficient than stranded at RF frequencies. It is much stiffer than RG-58 and slightly stiffer than RG-8 (RG-8 has a stranded center conductor making it more flexable). It does take a little getting use to while working with the very stiff LMR-400 however the rewards are more than worth it. LMR-400 will use the same PL connectors as you would use on RG-8.

One more advantage to using a higher quality coax such as LMR-400 over RG-58 is the shielding. You have more shielding and better quality shielding. Better coax shielding will reduce the amount of interference that gets into your scanners from household consumer electronics such as computers, WIFI routers, etc.

RG-58 is fine if you are only running a very short distance or for jumpers. I do use RG-58 for jumpers between my receive multicouplers and scanners. Use the chart below to determine if you're going to have much to gain by using LMR-400 verses RG-58, remember, every 3 dB you save is a doubling of your received signal strength.

When I buy LMR-400 I've found that Jefa Tech has good prices on 500' spools and is very reliable. They also sell it by the foot with or without connectors.

Below is a chart that will help you determine the losses of various types of coax.



Attenuation (dB per 100 feet)

Coax Cable Signal Loss (Attenuation) in dB per 100ft*
Loss* RG-174 RG-58 RG-8X RG-213 RG-6 RG-11 RF-9914 RF-9913
(LMR-400)
1MHz 1.9dB 0.4dB 0.5dB 0.2dB 0.2dB 0.2dB 0.3dB 0.2dB
10MHz 3.3dB 1.4dB 1.0dB 0.6dB 0.6dB 0.4dB 0.5dB 0.4dB
50MHz 6.6dB 3.3dB 2.5dB 1.6dB 1.4dB 1.0dB 1.1dB 0.9dB
100MHz 8.9dB 4.9dB 3.6dB 2.2dB 2.0dB 1.6dB 1.5dB 1.4dB
200MHz 11.9dB 7.3dB 5.4dB 3.3dB 2.8dB 2.3dB 2.0dB 1.8dB
400MHz 17.3 B 11.2dB 7.9dB 4.8dB 4.3dB 3.5dB 2.9dB 2.6dB
700MHz 26.0dB 16.9dB 11.0dB 6.6dB 5.6dB 4.7dB 3.8dB 3.6dB
900MHz 27.9 B 20.1dB 12.6dB 7.7dB 6.0dB 5.4dB 4.9dB 4.2dB
1GHz 32.0dB 21.5dB 13.5dB 8.3dB 6.1dB 5.6dB 5.3dB 4.5dB
Imped 50ohm 50ohm 50ohm 50ohm 75ohm 75ohm 50ohm 50ohm
* Note: Coax losses shown above are for 100 feet lengths. Loss is a length multiplier, so a 200 ft length would have twice the loss shown above and a 50 ft length would have half the loss. This multiplier factor is why you should keep cable installation lengths between radios and antennas as short as practical!
Chart Courtesy of Radio Ware