Minimum distance between antennas

[WRPQ991]

Some fantastic info on coax, very informative. But why when you buy a GMRS radio that comes with and antenna is the coax so tiny?

OK, On to my question, how far apart should the base antennas be for CB 27Mhz 11 M and Gmrs 462--467 MHz both are vertical with ground plane. Both will be around 60 ft. I will probably never transmit on both at the same time but I don't want bleed over. I know the coax used will have alot to do with that too.

 

Edited December 14, 2022 by WRPQ991
I had BW instead of Freq..

[SteveShannon]

1 hour ago, WRPQ991 said:

Some fantastic info on coax, very informative. But why when you buy a GMRS radio that comes with and antenna is the coax so tiny?

OK, On to my question, how far apart should the base antennas be for CB 27Mhz 11 M and Gmrs 12.5 kHz -25 kHz both are vertical with ground plane. Both will be around 60 ft. I will probably never transmit on both at the same time but I don't want bleed over. I know the coax used will have alot to do with that too.

Re the first question on small coax: Because it’s cheap and they’re relatively short cables. 

[KAF6045]

7 hours ago, WRPQ991 said:

Some fantastic info on coax, very informative. But why when you buy a GMRS radio that comes with and antenna is the coax so tiny?

OK, On to my question, how far apart should the base antennas be for CB 27Mhz 11 M and Gmrs 12.5 kHz -25 kHz both are vertical with ground plane. Both will be around 60 ft. I will probably never transmit on both at the same time but I don't want bleed over. I know the coax used will have alot to do with that too.

You have confused frequency band (CB) with channel bandwidth (GMRS). GMRS operates on 462/467MHz (approximately 60cm). CB is ~17 times longer in wavelength, and with only 4W output, probably won't be seen by a GMRS antenna. Conversely, even with a 50W transmitter, the CB antenna is unlikely to capture too much of a signal. (The mag-mounts on my rust bucket are only about 18" apart).

Of course, if you're really concerned, the solution is to STACK the antennas -- one a few feet above the other -- since the beam pattern is minimal off the end of the antenna, and maximum off the sides.

 

6 hours ago, Sshannon said:

Re the first question on small coax: Because it’s cheap and they’re relatively short cables. 

And likely intended for mobile installations where flexibility is more important -- who has room for 9913 with roughly a 1ftx1ft area needed to make a 90deg bend.

[WRPQ991]

On 12/9/2022 at 10:22 PM, KAF6045 said:

You have confused frequency band (CB) with channel bandwidth (GMRS). GMRS operates on 462/467MHz (approximately 60cm). CB is ~17 times longer in wavelength, and with only 4W output, probably won't be seen by a GMRS antenna. Conversely, even with a 50W transmitter, the CB antenna is unlikely to capture too much of a signal. (The mag-mounts on my rust bucket are only about 18" apart)

thank you I've edited the question.  I was reading it wrong.