Interior Antenna Recommendations?

[Eltee]

I am thinking about taking an extra mobile GMRS radio, adding a power supply and using it at home as a base unit. Is there an antenna that will work INSIDE the house? I know it won't be optimum but for now no drilling through the wall. 

Also, any danger of brain fry using a mobile radio in the 25-40 watt range indoors?

THANK YOU.

[IanM]

I'm doing well with a couple of DIYed Slim Jims tuned for a few different bands. The advantage over just using a mobile antenna is they obviate the need for a ground plane (the ubiquitous cookie sheet), and can be hung up in a window or something like that. 

You should be fine provided it's not, you know, right next to your head. I plugged it into the ARRL safe exposure calculator, assuming a generous 3dBi antenna, and it gives you about 3 feet safe distance for a worst-case, 5-minute transmission. 

The bigger issue is that most linear antennas are omnidirectional, and you're wasting power radiating into your house when you want to be pointing more of it outside. A Yagi-Uda or corner reflector would be far more directionally efficient. But it's a lot harder to find a convenient place to put inside, and isn't so easy on the eyes.

What sort of install are you looking at building? If you're in a multifamily building you might be out of luck (as I am), but if you're setting up in an attic or the like, you might have better luck with a bigger (or uglier) antenna, and might have decent enough penetration coupled with a height advantage to forgo mounting externally.

[wayoverthere]

13 hours ago, Eltee said:

I am thinking about taking an extra mobile GMRS radio, adding a power supply and using it at home as a base unit. Is there an antenna that will work INSIDE the house? I know it won't be optimum but for now no drilling through the wall. 

Also, any danger of brain fry using a mobile radio in the 25-40 watt range indoors?

THANK YOU.

As you said, not optimum. The biggest issue would be steel frame or radiant barrier insulation that would stand in the way. From home in the valley to repeaters on the ridge, I get solid range (30ish miles on mid, 60ish on high) with a mag mounted 5/8 wave on top of a bookcase. Outside the barriers, the higher you can get the antenna the better to avoid other obstructions around you.

On RF safety, Lake Washington amateur radio club has a good rf calculator. Assuming 6dbi antenna and 50 watts, 50% talk/receive time, it spits out a minimum safe distance of 5.3 ft in an uncontrolled environment; if I understand the controlled/uncontrolled, it boils down to knowledgeable user vs uninformed public access.

Lower power, lower gain antenna, and/or less talk time equate to less distance needed

Edit: in my sleep deprived state, I forgot to add the link.  http://www.lakewashingtonhamclub.org/resources/rf-exposure-calculator/

Edited October 30, 2021 by wayoverthere
add link

[mbrun]

I am thinking about taking an extra mobile GMRS radio, adding a power supply and using it at home as a base unit. Is there an antenna that will work INSIDE the house? I know it won't be optimum but for now no drilling through the wall. 

Also, any danger of brain fry using a mobile radio in the 25-40 watt range indoors?

THANK YOU.

For about nine months I used two different Ed-Fong roll-up J-Pole antennas for GMRS and amateur radio services in my home. I operated them at 5W using an HT. They can be used at higher power if you wish, but you should operate further away from them if doing so as @IanM pointed out. In my case, I hung them from existing ceiling plant hangers and curtain rods near the windows in a couple of rooms. Although I have external antennas feeding radios in my shack, those Ed-Fong antennas remain hanging in those rooms for ready and easy connection to my HTs when I want to use them. They are easy to take down, roll-up, pack and take camping as well.

Good luck on your endeavor.


Michael
WRHS965
KE8PLM

[pcradio]

I use this antenna up in my attic. Much better than trying to use radios inside in the house. I'm going to get a 2m (amateur) version. I want to sell it, if you're interested.

[PACNWComms]

Bought a couple of these from Tessco a long while ago. Use them in the attic mounted to New Motorola (NMO) magnet mounts on baking tins attached in the attic. I do not get up there often,but have had magnet mount antennas in the roof/attic space for 13 years now. Work freat for UHF in general and GMRS RX/TX is about 18-26 miles. Being rated at 200 Watts, they do not get warm at 50 Watts.

PCTEL's BMWU4002S Maxrad 380 – 520 MHz wideband 2 dB with ground plane/unity gain without black antenna with stainless steel spring 200 W. Order Motorola style mount separately.

[dhardin53]

With such a nice set up you will have it is kind of sad you cant get that outside and up in the air more. But I understand many are not a fan of antennas sticking everywhere. Many Home owners organizations and city regulation (or wife's) will not allow outside antenna.  But most of all 20 to 40 W output need to be a fair amount of distance from family members. More so if you transmitting a lot. One might research  460 MHz at 40 watts safe distance for humans. 

Good luck. most of all be safe.

[BoxCar]

12 hours ago, dhardin53 said:

But most of all 20 to 40 W output need to be a fair amount of distance from family members. More so if you transmitting a lot. One might research  460 MHz at 40 watts safe distance for humans. 

The FCC has published guidelines regarding the amount of RF exposure and safe distances from antennas for both operators and others such as family members that need to be maintaned. There are several calculators available on the Internet. The ARRL has one that is easy to use along with a brief description of the requirements from the FCC applicable to all radio stations, not just amateurs. For a 50W station, the minimum distance for an operator using GMRS frequencies is 6 feetfrom the antenna while family members should be 10 to 12 feet away when transmitting.

[maddogrecurve]

On 10/29/2021 at 10:53 PM, IanM said:

I'm doing well with a couple of DIYed Slim Jims tuned for a few different bands. The advantage over just using a mobile antenna is they obviate the need for a ground plane (the ubiquitous cookie sheet), and can be hung up in a window or something like that. 

You should be fine provided it's not, you know, right next to your head. I plugged it into the ARRL safe exposure calculator, assuming a generous 3dBi antenna, and it gives you about 3 feet safe distance for a worst-case, 5-minute transmission. 

The bigger issue is that most linear antennas are omnidirectional, and you're wasting power radiating into your house when you want to be pointing more of it outside. A Yagi-Uda or corner reflector would be far more directionally efficient. But it's a lot harder to find a convenient place to put inside, and isn't so easy on the eyes.

What sort of install are you looking at building? If you're in a multifamily building you might be out of luck (as I am), but if you're setting up in an attic or the like, you might have better luck with a bigger (or uglier) antenna, and might have decent enough penetration coupled with a height advantage to forgo mounting externally.

Ian,

 

What kind of slim jim's are you making?  I have been trying to make them out of ladder line for GMRS and have been unsuccessful!  There are no plans online for them, and the calculators are not working for me.  I have made a few for 2m/70cm and a single band 2m one, but I cannot get GMRS or Murs to work by themselves.