Using magmount antenna indoors

[n1moa]

Thought I would share my recent experience setting up my magmount inside my shack. My scanner is a SDS100, which I mostly use here at home. I had been using a Tram 1410 discone antenna outside mounted on a 15' mast. It worked fine. But it was prone to accumulating ice in the winter and then all I could get would be local activity. I would have to go out and smack the mast a few times.

So I wondered about using my Hustler magmount scanner antenna inside on a 6' camera tripod. I mounted an old magnet upside down on the tripod, laid an old 16" round pizza pan on the magnet, and then put the Hustler on top of the pizza pan. That was necessary because the pan is aluminum. Antennas don't care what kind of metal you use for a ground plane, but the magnet does. The tip of the antenna is almost touching the ceiling, so abt 9' in the air.

Using the county sheriff's dispatch center (20 miles away) as a reference, I was surprised to see a slight gain over the outside discone, especially since it's so hilly here. I'm now getting -50db consistently, whereas the discone gets -50 to -60db.

Both of these antennas are wide band antennas intended for scanners, and both cost around $50.

73 Marvin, N1MOA

 

[donc13]

Thought I would share my recent experience setting up my magmount inside my shack. My scanner is a SDS100, which I mostly use here at home. I had been using a Tram 1410 discone antenna outside mounted on a 15' mast. It worked fine. But it was prone to accumulating ice in the winter and then all I could get would be local activity. I would have to go out and smack the mast a few times.

So I wondered about using my Hustler magmount scanner antenna inside on a 6' camera tripod. I mounted an old magnet upside down on the tripod, laid an old 16" round pizza pan on the magnet, and then put the Hustler on top of the pizza pan. That was necessary because the pan is aluminum. Antennas don't care what kind of metal you use for a ground plane, but the magnet does. The tip of the antenna is almost touching the ceiling, so abt 9' in the air.

Using the county sheriff's dispatch center (20 miles away) as a reference, I was surprised to see a slight gain over the outside discone, especially since it's so hilly here. I'm now getting -50db consistently, whereas the discone gets -50 to -60db.

Both of these antennas are wide band antennas intended for scanners, and both cost around $50.

73 Marvin, N1MOA

You would get even better reception if you used a steel pizza pan. The aluminum won't act as a ground plane because it does not interact with magnetic waves to electrically connect as a ground plane.

A simple test is simply remove the aluminum pizza pan and see if the reception changes.

 

[dlwtrunked]

You would get even better reception if you used a steel pizza pan. The aluminum won't act as a ground plane because it does not interact with magnetic waves to electrically connect as a ground plane.

...

Uh, no.

 

[donc13]

Uh, no.

Ah.. Yes... For an antenna to have a ground plane, they must be electromagnetically connected to to the radiating/receiving element of the "antemma system". Every magnet mount antenna I have ever used or seen has a rubber (a non conductor) underside to avoid scratching what it is mounted on. Aluminum must have a physical electrical connection to act as a ground plane since it has zero magnetic connection.

Anyway.. I have had my say..

 

[mmckenna]

Ah.. Yes... For an antenna to have a ground plane, they must be electromagnetically connected to to the radiating/receiving element of the "antemma system". Every magnet mount antenna I have ever used or seen has a rubber (a non conductor) underside to avoid scratching what it is mounted on. Aluminum must have a physical electrical connection to act as a ground plane since it has zero magnetic connection.

Anyway.. I have had my say..

I've installed a lot of antennas on aluminum body vehicles. It works fine as a ground plane.
Aluminum has lower resistance than steel….

The coupling between a mag mount and the ground plane is capacitive, has nothing to do with magnets. The magnet is just the mechanical connection that holds it on the top of the car. What impacts the capacitive coupling is the gap between the two plates.

 

[mmckenna]

Using the county sheriff's dispatch center (20 miles away) as a reference, I was surprised to see a slight gain over the outside discone, especially since it's so hilly here. I'm now getting -50db consistently, whereas the discone gets -50 to -60db.

That's a good comparison.

Discone antennas kind of suck, especially at lower frequencies. Their benefit is their wide bandwidth.
Longer coax run probably isn't helping, either.
I'd bet the indoor antenna has a bit of an edge on the gain, also.

Always good to experiment with things like this. You can sit and do the maths all day long, but when it comes down to it, hook it up and try.

 

[prcguy]

Ah.. Yes... For an antenna to have a ground plane, they must be electromagnetically connected to to the radiating/receiving element of the "antemma system". Every magnet mount antenna I have ever used or seen has a rubber (a non conductor) underside to avoid scratching what it is mounted on. Aluminum must have a physical electrical connection to act as a ground plane since it has zero magnetic connection.

Anyway.. I have had my say..

The magnet has nothing to do with coupling, it’s only there to stick to cars. The diameter of the magnet housing common to the antenna/feedpoint ground and thickness of the protective coating and the thickness of the car paint determine the capacitive coupling between the mag mount and whatever it’s sitting on. If the magnet diameter is large enough and the coatings are thin enough you can come close in performance to a hard grounded antenna mount to the ground plane.

The cheap ham antennas with a mag mount the size of a Hershey’s Kiss chocolate are completely inadequate. I find a 5” dia mag mount with thin protective coating to be ok at VHF through 800MHz. A 5” mag mount for CB or especially HF is pretty bad but I’ve supplemented those with an 8” X 11” chunk of refrigerator magnet material coated with copper foil and bonded to the magnet. BTW, the performance of a mag mount will be identical stuck to a steel sheet or sitting on an aluminum sheet.

 

[tvengr]

If you have a metal file cabinet, stick the antenna in the center of that. Better yet, put an NMO mount through the top of the cabinet in the center and install a tri-band mobile antenna. That will give you a good ground plane. That would also put the antenna at window height where there will be less signal obstruction. If possible, put the cabinet in front of a window facing the direction you want to receive. You could also use a base station adapter with a NMO connector. The radials on the adapter will also give you a good ground plane. I have a tri-band mobile antenna on a base station adapter in my attic. It works very well.

 

[dlwtrunked]

Ah.. Yes... For an antenna to have a ground plane, they must be electromagnetically connected to to the radiating/receiving element of the "antemma system". Every magnet mount antenna I have ever used or seen has a rubber (a non conductor) underside to avoid scratching what it is mounted on. Aluminum must have a physical electrical connection to act as a ground plane since it has zero magnetic connection.

Anyway.. I have had my say..

But is is wrong. In essence, the capacitance is the connection between the antenna and ground plane (whether aluminum, steel, or some other conductor). Not further physical connection is required for for the electromagnetic operation of the antenna. The magnet being attracted to steel is only to physically hold the antenna in place.

 

[10-43]

But is is wrong. In essence, the capacitance is the connection between the antenna and ground plane (whether aluminum, steel, or some other conductor). Not further physical connection is required for for the electromagnetic operation of the antenna. The magnet being attracted to steel is only to physically hold the antenna in place.

What you said. I was about to say the same.

There are numerous ground plane kits available with NMO mounts on Amazon and eBay. Some are rather inexpensive.

 

[N9JIG]

When we moved into our new home it was too hot to go into the attic to install my antennas so I took 3 of those cheap $15 "Hershey's Kiss" style magmounts and put them on cookie sheets on top of a 7-foot tall bookshelf in my office. Two were on scanners and the other on a dual-band rig. They worked so well that I almost didn't bother with the attic installation that winter. The wife wasn't happy when she couldn't find the cookie sheets.

I also tried using NMO Magmounts and different antennas but the "Kiss" antennas seemed to work as good if not better than the more substantial ones.

I keep a few of these around for special purposes like this and for temporary use when I get a new car. They work pretty darned good but don't have the speed rating of the larger mounts. Inside that really isn't an issue unless you really crank up the AC.

 

[prcguy]

When we moved into our new home it was too hot to go into the attic to install my antennas so I took 3 of those cheap $15 "Hershey's Kiss" style magmounts and put them on cookie sheets on top of a 7-foot tall bookshelf in my office. Two were on scanners and the other on a dual-band rig. They worked so well that I almost didn't bother with the attic installation that winter. The wife wasn't happy when she couldn't find the cookie sheets.

I also tried using NMO Magmounts and different antennas but the "Kiss" antennas seemed to work as good if not better than the more substantial ones.

I keep a few of these around for special purposes like this and for temporary use when I get a new car. They work pretty darned good but don't have the speed rating of the larger mounts. Inside that really isn't an issue unless you really crank up the AC.

The whips on most Hershey kiss mag mounts are painted spring steel and lossy on top of the poor coupling. If you transmit at 25w on one for about 30 seconds the whip will be so hot it will burn your fingers.

 

[n1moa]

Well, a steel pizza pan would be more convenient, since I wouldn't need to use a second magnet on the bottom of the aluminum pan. So, I ran down to Dollar General and found a large steel pizza pan for $8. After some quick testing, I can say it made no difference as far as signal strength. No surprise there, but it does give me more flexibility as far as where I can put it.

For what it's worth, I did know someone who added several layers of thick tape to his ham radio mag mount. He was trying to protect the paint on his car roof. That did affect performance and not in a good way. I've also seen thicker rubber boots for mag mounts. That can't be good either, since this type of antenna relies on a strong capacitive connection.

I think there is some confusion, because a NMO or similar type mount does rely on a good electrical connection to its ground plane.

 

[dlwtrunked]

Well, a steel pizza pan would be more convenient, since I wouldn't need to use a second magnet on the bottom of the aluminum pan. So, I ran down to Dollar General and found a large steel pizza pan for $8. After some quick testing, I can say it made no difference as far as signal strength. No surprise there, but it does give me more flexibility as far as where I can put it.

For what it's worth, I did know someone who added several layers of thick tape to his ham radio mag mount. He was trying to protect the paint on his car roof. That did affect performance and not in a good way. I've also seen thicker rubber boots for mag mounts. That can't be good either, since this type of antenna relies on a strong capacitive connection.

I think there is some confusion, because a NMO or similar type mount does rely on a good electrical connection to its ground plane.

No confusion that I have seen. I know you know from what you wrote, but for others who may not have gotten it: A non-magnetic NMO (after mounting in the drilled hole), has (if the roof is metal) and needs a good RF type ground (not just a simple ground) to the ground-plane of the vehicle to function properly. A magnetic-mount NMO obtains that via a capacitance. (And being a person who gets picky about words as I have found someone will often misunderstand, it really this is coupling to the ground-plane rather than a "ground connection"). They do sell pads to protect the roof. I see those all the time at hamfests; I guess your friend did not. I have never used one, had a magnetic-mount on my Corolla roof, always clean under it when I wash the car, NO scratches, and it is a 2006 with over 500,000 miles. Other parts of the car have ppint issue, but not that part.

 

[prcguy]

No confusion that I have seen. I know you know from what you wrote, but for others who may not have gotten it: A non-magnetic NMO (after mounting in the drilled hole), has (if the roof is metal) and needs a good RF type ground (not just a simple ground) to the ground-plane of the vehicle to function properly. A magnetic-mount NMO obtains that via a capacitance. (And being a person who gets picky about words as I have found someone will often misunderstand, it really this is coupling to the ground-plane rather than a "ground connection"). They do sell pads to protect the roof. I see those all the time at hamfests; I guess your friend did not. I have never used one, had a magnetic-mount on my Corolla roof, always clean under it when I wash the car, NO scratches, and it is a 2006 with over 500,000 miles. Other parts of the car have ppint issue, but not that part.

500k mi? Do you drive to So Cal for lunch on a regular basis? Mag mounts do have a reputation for scratching paint and falling off occasionally but thats more on the CB side where antennas are much larger than VHF/UHF/800 versions which are a fraction of the size and their magnets usually stick better.

 

[dlwtrunked]

500k mi? Do you drive to So Cal for lunch on a regular basis? Mag mounts do have a reputation for scratching paint and falling off occasionally but thats more on the CB side where antennas are much larger than VHF/UHF/800 versions which are a fraction of the size and their magnets usually stick better.

I had to drive 80 miles a day to/from work and regularly took long vacation drives (like VA to CO, WY, or FL) and this weekend will make my 5th drive from VA to IA within the last year. Actually it is over 550k. Odometer stopped at 299,999 10 years ago (all it was designed for in that model/year and a $4k dash replacement to fix). So I keep track with the trip odometer for oil changes but sometime forget to record those before the oil change people re-set it. Antenna is usually 2m/440 but occasionally something larger for some personal project.

 

[garys]

I've been doing this with both a NMO mag mount and a "Hersey kiss" mag mount antenna. I was using a Hustler scanner antenna with an added NMO base for a while, but bought an EM Wave antenna recently.

The mag mounts are on top of a four drawer steel filing cabinet and I've had surprisingly good coverage of 800 P25 trunk systems, VHF public safety, aviation, and a small number of 2M an 440Mhz ham repeaters. I'd likely get slightly better coverage with a good scanner antenna mounted on my house, but with the P25 LSM trunk systems prevalent in central Texas, not worth the cost.

 

[bobmich52]

My 2 bits

For my SDS 200 in my office, I have a old ratshack mobile mag antenna on top of a dinty moore stew can, drilled a small hole in my desk console to insert antenna & the can is hidden by a small wireless weather station

Works well on all systems, But the goal of a outside antenna, hence to find a licensed & insured installer in CT in my area ( I live in a cape) is difficult to say the least

 

[ratboy]

If I could raise the ceiling at work about 15 inches, I would be very happy. The antennas that work really well here all tend to be on the larger side, and sticking them onto my cabinets in my cubicle is impossible. The smaller antennas don't really outperform the stock whip. I put my best mag mount antenna, the one sold under the Skyscan name on ebay, among other names, onto a coworker's lower cabinets and it worked really well. A lot of Michigan traffic that only my GRE scanners pick up was coming in very clearly on the SDS200. I still heard almost nothing on Railband on the SDS200, which seems deaf as a rock on VHF and Air.

 

[rf_patriot200]

When we moved into our new home it was too hot to go into the attic to install my antennas so I took 3 of those cheap $15 "Hershey's Kiss" style magmounts and put them on cookie sheets on top of a 7-foot tall bookshelf in my office. Two were on scanners and the other on a dual-band rig. They worked so well that I almost didn't bother with the attic installation that winter. The wife wasn't happy when she couldn't find the cookie sheets.

I also tried using NMO Magmounts and different antennas but the "Kiss" antennas seemed to work as good if not better than the more substantial ones.

I keep a few of these around for special purposes like this and for temporary use when I get a new car. They work pretty darned good but don't have the speed rating of the larger mounts. Inside that really isn't an issue unless you really crank up the AC.

And still no more cookies at your house...