Thread: Antennas near one another?

Can't see why not - the frequencies used are quite different.
I used to have a 27mHz cb antenna & HF tapped whip 10cm apart on my bullbar with no issues.

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More importantly the GSM phone isn't putting out a lot of power.

I would think twice about putting a 100W HF very close to another antenna, just because of the potential RF energy being emitted.

If you can locate the antennas further apart it will be better. You will get a hole in your radiation pattern, the phone will have a weaker signal coming from/going to a direction, most likely that of the other antenna.

I have very limited roof space available,,(behind the rear hatch, in between the two solar panels) if I can stretch it to 450 will that be better?

also, will a cable run of over 5metres be bad for the am aerial?

If I understood correctly, the other one was a receiver only antenna, so shouldn't interfere greatly with the GSM antenna, in fact it would have minimal impact on the propagation of the phone signal.

Should not be a problem, and 450 is better than 300. Just look at the array of high powered antennae on some Towers

5m cable run should be no problem at all assuming you will use a quality coaxial cable such as rg6. Installing terrestrial tv antennas & foxtel satellite installations I regularly run 20m+ of rg6 & the signal drop over that distance is mimimal (foxtel at dish signal strength 85, MER 14, at wall plate over 20m of cable signal strength 81, MER 13).
Sorry it I've got too technical.

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300mm is an acceptable distance, general rule of thumb is to keep them at least 1/4 of a wavelength apart, which for the GSM (lowest band) is 35cm, so you're almost a full wavelength apart. If anything it may slightly reduce the performance of your FM/AM antenna but this will be negligible.

Originally Posted by Alex 110

use a quality coaxial cable such as rg6.

Just to clarify, you don't want to use RG6 or RG59 or similar for the GSM antenna as the impedence is 75Ω for TV, you want to use low loss RG58 (foam coax) or LMR195 which has a 50Ω impedance and keep the run as short as possible. The RG6 is OK for the AM as stated.