Distance between antennas

[Kiwibru]

I originally posted this in the GMRS section but thought I might get some feedback by also posting it here as the issue is two antennas, one GMRS and the newer one for Ham.
My established GMRS antenna is on the end of the house , roof peak, with a side mounted support pipe attached to the side of the house. I want it stay as is and the GMRS Comet antenna at about 40 ft.
The new antenna for HF, etc. will be a KC4 on a DX Engineering OMNI-Tilt folding base with a support post cemented into a 3 foot hole, 2.5 ft. above ground. The new antenna will be at least 25 ft. to the SE of the house and is going to be approximately 26 ft up so much lower than the GMRS antenna. Will this separation distance be enough?

(My intention is to not run both systems powered up at the same time. Both antennas grounded to house ground and extra grounding rods. Each antenna uses a separate run of coax into the upstairs office.)
Thanks...






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[mmckenna]

I originally posted this in the GMRS section but thought I might get some feedback by also posting it here as the issue is two antennas, one GMRS and the newer one for Ham.
My established GMRS antenna is on the end of the house , roof peak, with a side mounted support pipe attached to the side of the house. I want it stay as is and the GMRS Comet antenna at about 40 ft.
The new antenna for HF, etc. will be a KC4 on a DX Engineering OMNI-Tilt folding base with a support post cemented into a 3 foot hole, 2.5 ft. above ground. The new antenna will be at least 25 ft. to the SE of the house and is going to be approximately 26 ft up so much lower than the GMRS antenna. Will this separation distance be enough?

I may have misunderstood your previous post, but I thought you were running GMRS on one antenna and 2 meter/440 on the other. Since it sounds like you are now doing GMRS on one and HF on the other, you should not have an issue. Good radios will have some amount of bandpass filtering in the front ends that will keep the majority of the out of band energy out. Even without that, it really sounds like you have both enough horizontal separation and vertical separation to provide a good amount of isolation between antenna.

I think even if you were running GMRS on one and 2 meter/70 centimeter on the other you'd be fine. There is some maths you can do to confirm it, but we'd need a lot of info to be accurate.

(My intention is to not run both systems powered up at the same time. Both antennas grounded to house ground and extra grounding rods. Each antenna uses a separate run of coax into the upstairs office.)
Thanks...

Shutting the radios off doesn't disconnect the antennas from the receiver section. It won't hurt to shut them off, but it's not going to necessarily prevent any possible issues (although you should be just fine).

 

[paulears]

The sort of distances you have make inverse square law reduce the signal strength quite rapidly, and with one being UHF and the other HF, that’s no grief at all. I have two antennas on one mast, feet apart on a stand off tube. I use an HF radio on a quad band vertical for 10m, and the ATU lets me have usable signals on 20m, while the other antenna is 24/7 on marine band. Neither radio has an issues with this arrangement.

 

[Kiwibru]

Thanks and sorry for the confusion. I had just decided I did not like climbing up on the roof of a two story farm house anymore. Setting up something for the HF bands on the ground that can fold down made a lot of sense but being new to this the question of distance was in my mind.

 

[Kiwibru]

Getting closer to bringing the new antenna up but wondered about the short run of coax from the new antenna to the wall of the house, then up to the window sash and into the house. There is about ten feet of ground between the wall and antenna that I have to cover with the coax. Would burial be necessary with a burial certified coax or can I just run it sitting on the ground or slightly elevated using a support? The space is a perennial garden with low plants.

 

[mmckenna]

Getting closer to bringing the new antenna up but wondered about the short run of coax from the new antenna to the wall of the house, then up to the window sash and into the house. There is about ten feet of ground between the wall and antenna that I have to cover with the coax. Would burial be necessary with a burial certified coax or can I just run it sitting on the ground or slightly elevated using a support? The space is a perennial garden with low plants.

If it is going to be underground in any way, that includes direct buried or in conduit that is underground, you need to use direct bury rated cable.

If it is sitting on the ground, it's essentially underground and water/snow/mud/debris will accumulate and cover it.

I'd find a way to install it so it's well off the ground and save yourself the headache of DB rated cable.

 

[Kiwibru]

A simple 1/2" or 3/4" fiberglass wand placed midway would hold the cable and prevent any swinging motion. We get a lot of Gale force winds in the winter here. So as long as the cable portion that is running from the antenna to the wall is above ground and prevented from swinging back and forth in the wind I am good?

 

[mmckenna]

A simple 1/2" or 3/4" fiberglass wand placed midway would hold the cable and prevent any swinging motion. We get a lot of Gale force winds in the winter here. So as long as the cable portion that is running from the antenna to the wall is above ground and prevented from swinging back and forth in the wind I am good?

Usually the way this is done in the commercial world is to have a bridge that supports the cable from the tower to the hut. That's overkill for what you are doing.

You could run a messenger wire from the mast to the eves of your home as a support and then ty wrap the coax to that, similar to how larger telephone cables are run.

A few supports to hold it steady is what I think you are suggesting, that would probably work fine.