Is 10' enough between base antennas

[RenoHuskerDu]

I have a 20' metal carport with 6 metal legs buried 2' deep. I've added a ground rod. I believe it's a good platform for 3 antennas on the one side which is free of trees.

I already have a 60cm antenna up there on a 10' pole. and I plan a 2m antenna on the same setup next . Each will be 10' away from the other, even when I add a third.

Do you believe that 10' is sufficient spacing?

 

[mmckenna]

Depends on how much power you are running, antenna gain, feed line losses, tolerance of the radios, etc.

But for most hams, 50 watt radios, etc, 10 feet is probably just fine. A lot of guys run antennas much closer on mobile installs.

 

[KF0NYL]

General rule is 1 full wave length of separation between antennas.

 

[mmckenna]

General rule is 1 full wave length of separation between antennas.

That is not accurate, as it doesn't take into account any variables at all.

 

[KF0NYL]

That is not accurate, as it doesn't take into account any variables at all.

I try to keep answers simple and easy to understand. Not everyone wants or needs very detailed information.

Here is just one website I found that explains antenna spacing and is simple to understand.

How close can I mount two VHF/UHF antennas - KB9VBR Antennas

At least 1 full wave length is a general rule of thumb. A 1/4 wave length is the minimum horizontal spacing at the lowest frequency being used. I was trying to keep things simple for the OP and that is why I said the general rule of thumb is 1 full wave length to help prevent any issues.

The amount of spacing will depend on what bands the OP is wanting to use. For 2m that would be a minimum of 1.6 feet, for 70cm and GMRS that would be half a foot. Now if he is going to put up an HF antenna then the spacing increases. This is especially true if say one is putting up a dual band antenna for 2m/70cm AND a GMRS antenna since 70cm and GMRS are close teach other. The lower the frequency, the more space is needed.

 

[mmckenna]

The amount of RF between the two antennas doesn't drop to zero at one wavelength. It's simply attenuated by a known amount (measured in dB). The transmitter power plays in here, as does antenna gain (both antennas), feedline loss, etc. The ability of the receiver to handle that RF needs to be taken into account, also.

1 wavelength might work fine in some setups, it may not be sufficient in others. Since @RenoHuskerDu hasn't provided any details, a flat statement like "1 wavelength" may not be sufficient. I'd hate for him to damage a radio.

With some very simple test equipment, it would be fairly easy to test. An accurate wattmeter, and a dummy load at the radio end of the feedline would indicate how much power is making it back down to the radio when the other is transmitting. Most feel that less than 250mw is safe for ~most~ radios.

 

[KF0NYL]

Sorry I bothered to reply to this thread. Since I can't edit or delete my post, can. mod delete my replies to this thread.

 

[K6GBW]

I've had two dual band VHF/UHF antennas on small masts mounted about four feet apart. The antennas go to a set of P25 radios and a set of DMR radios. Been that way for years and never any issues.

 

[paulears]

Tye trouble is you cannot produce simple responses with rules or guidelines, because if you simplify too much, the people you simplify for, misunderstand. It was pointed out that the advice could be misunderstood, but you persisted. Its like dumbing down physics on almost any topic. You solve one issue and create two others. Two antennas a wavelength apart for 70cm is a sort of distance people can work with, but two CB antennas using that rule break it. McKennas first post is the correct way to respond. All the variables. As far as i am aware, there is no general ‘rule’. The only correct answer is ‘it depends’. The trickiest thing in my teacher training was to do with generalisations. How to explain a complex topic simply? It is very hard to explain in simple terms and people remember the wrong answer! Like Watts is amps x volts. Its often a surprise when people have always believed that, when the formula suddenly fails under some circumstances.