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Radio shielding when close to an antenna?


Riktar
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I am considering moving my TK-8180H radio right next to the antenna in the attic since I have a spare KRK-10 kit which would allow me to put the head unit right on my desk. And it would eliminate any power loss from using 30 feet of coax cable I am currently using.

Would there be any need to shield the body of the radio from RF since it would be right next to/below the antenna?

The antenna I am using is a Commscope DB404-B.

 

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I would not install the radio that close. If your using 30' of cable you are not loosing that muck unless its twin lead wire. Any RG/LMR will be fine on that short of a distance. I dont see where you would gain much if not anything by moving it in the attic with the antenna. 

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I don’t currently see an issue operating the radio closer to the antenna, but that does not mean one could not occur. But like @kb2ztx I see nothing notable to be gained by doing so. In the real-world you will never be able to objectively quantity any performance gains unless of course you are using sub-standard inappropriate feed-line in the first place.


Michael
WRHS965
KE8PLM

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Your radio head should be fine right ext to the antenna.  They are made for this.  Some ferrites on the power lines wouldn't hurt but no big deal.  Of course you want a decent ground up there.

You may notice a greater improvement on RX rather than TX.  Your coax loss adds directly to your noise figure of your RX.  So you may see a noticeable improvement. 

While 30' of coax is acceptable in most cases I think eliminating it will help on weak signals.  Modern radios have very low noise figures so it's easy to double it with some coax loss.  I think it's good to keep it to a minimum.

Vince

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Thanks for the replies.

Since I didn't mention the cable type I have run the following:

Started with 50 feet of LMR400 and later found a 30 foot length of FSJ4-50B with N connectors already install that made a noticeable difference. 

So for the sake of seeing what would happen if I went "cableless" to the antenna I considered this.

I did not consider the ground. Is that to say I should ground the antenna itself aside from the grounded power supply to the radio body? 

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This comes up often in some use cases, such as the bridges of ships, where the radios are mounted overhead, and the antennas are only a few feet above them. The higher the power of the radio, the more separation you want between the radio and its antenna and any other radio/antenna combination that could interfere with it. More so with radios that have plastic cases and minimal shielding often only being the heat shield fins. You risk damaging the radio by using them too close to the antenna or another radio and its antenna. As for cable, thirty feet is not much, and as long as it is shielded with low reflected power, checked with a meter, that power is going out the antenna....you do not want your radio next to that.

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