VHF high antenna

[BryanTheRed]

I am looking for an antenna for my base station.....would a mobile 1/4 wave work mounted on the roof or chimney? or do I need something else? This system in mostly in the 150 to 160 range. Its my base so I can check enroute to calls from home!!!!!

 

[K5MAR]

A mobile antenna requires a ground plane to work effectively. Radio Shack sells a VHF-high/UHF groundplane antenna that would do the trick for you. The P/N is 20-176, see here.

Mark S.

 

[BryanTheRed]

And that would be ok to transmit on? Would I need to put it on a pole how would I attach it to the roof?

 

[mgosdin]

I've got two of the 20-176 Radio Shack antennas, they do an outstanding job on RR's at 160-162mhz. From what I can tell there is a "Sweet Spot" in this antenna that runs from 150mhz ~ 165mhz. The local SO & Public Service in the 150's all come in crisp and clear on either of the antennas, but the one mounted up at 25' on a run of Heliax cable can do really astounding things with the RailRoad transmissions.

Mark Gosdin

 

[mgosdin]

And that would be ok to transmit on? Would I need to put it on a pole how would I attach it to the roof?

Transmit? On HAM Vhf HI? I suppose it would work, but the antenna wasn't designed with that in mind so you probably won't get a real low SWR. The only way to know for certain is to try.

I put mine up on standard antenna masts from Radio Shack & Lowes. They come in 5' & 10' segments. Mine are anchored at the bottom with PVC pipe driven into the ground about 3' deep, the mast slides over the PVC. They are also anchored to the eve of the roof using electrical conduit holders. So far they've held up fine to the famous Oklahoma winds ( Knock on wood! ).

I've got one at 15' and one at 25'. To tell the truth the 15' is plenty adequate, but like most scanner buffs I like to push things to see what can be done.

Mark Gosdin

 

[BryanTheRed]

I am looking for an antenna to transmit on

 

[K5MAR]

Yes, you can, providing the frequency you want to transmit on is within the tuned range of the antenna. Put it a pole on your roof, or clamp the pole to the chimney. I'd use a good VHF swr meter to check the setup.

Mark S.

 

[W4KRR]

I am looking for an antenna for my base station.....would a mobile 1/4 wave work mounted on the roof or chimney? or do I need something else? This system in mostly in the 150 to 160 range. Its my base so I can check enroute to calls from home!!!!!

You might want to try a Cushcraft Ringo Ranger. They can be tuned anywhere from about 135 to 160 MHz. Available at most ham radio dealers.

 

[rescue161]

Just make a J-Pole out of copper tubing. Easy as pye.

 

[Al42]

A ground plane made from an SO-239 is even easier to make - and to mount.

 

[scansomd]

I'm interested in doing something like you describe on my antenna mast.
What size are the PVC pipes your using?

Transmit? On HAM Vhf HI? I suppose it would work, but the antenna wasn't designed with that in mind so you probably won't get a real low SWR. The only way to know for certain is to try.

I put mine up on standard antenna masts from Radio Shack & Lowes. They come in 5' & 10' segments. Mine are anchored at the bottom with PVC pipe driven into the ground about 3' deep, the mast slides over the PVC. They are also anchored to the eve of the roof using electrical conduit holders. So far they've held up fine to the famous Oklahoma winds ( Knock on wood! ).

I've got one at 15' and one at 25'. To tell the truth the 15' is plenty adequate, but like most scanner buffs I like to push things to see what can be done.

Mark Gosdin

 

[jas0nr7272]

I use a amatuer duel band Larson NMO 2/70 with a maxrad groundplane http://www.maxrad.com/cgi/maxrad_products_ind.cgi?product=10167&catalog=10003

for all my scanning / transmitting needs works wonderful

 

[mgosdin]

I'm interested in doing something like you describe on my antenna mast.
What size are the PVC pipes your using?

I've used several different sizes. Currently the ground stake is 3/4" schedule 40 PVC. It's fairly stiff, but you may want to put a wooden dowl into the pipe to stiffen it. The ground needs to be a soft as possible, I put mine in this spring when the ground was very moist. (You could try soaking with a garden hose, but that can run you water bill up!)

The Antenna poles from Radio Shack & Lowes claim to be 1" in diameter, they are actually a little over size so they will fit loosely over the PVC. You may want to experiment some with fitting the PVC inside the masts, I've found that the published sizes for PVC & Antenna poles are not all that accurate.

One last thing I've done is drill a couple of holes into the Pole & PVC then screw in some self tapping sheet metal screws. This seems to add stability and keeps the Pole from twisting around the PVC.

As always, do not put up an antenna anywhere near power lines. One slip can seriously ruin your day!

Mark Gosdin

 

[BryanTheRed]

So I'm getting the inmpression I cannot use the 1/4 wave mobile antenna and then ground it? I also have a 5/8 wave it that would be better?

 

[Al42]

So I'm getting the inmpression I cannot use the 1/4 wave mobile antenna and then ground it? I also have a 5/8 wave it that would be better?

Same thing - use a ground under either one and it should work. I have a 2/70 mobile mag mount sitting on a coffee can and it works ok on 440 MHz. (A coffee can is a little small on 150 MHz. You'd need something about 3 feet in diameter.)

 

[TeRayCodA]

Yes you can use a R/S 20-176 Ground Plane Antenna for transmitting.

I used one for MURS,for about a year,BUT,it WILL need to be tuned for your band.On 151.820,for example,I had to actually do some cutting to get the SWR to an acceptable reading(1.5:1).I also removed the UHF elements.

I assume you have a VHF Hi SWR meter?

I have since changed to a homebuilt dipole stack,with 1/2" Andrews Heliax(what a difference!)

 

[BryanTheRed]

I am really confused I understand groundplane but just for S&G I took my 5/8 wave mobile antenna and mounted it to a L bracket. Set it on the floor and leaned it up against the wall, well I transmitted and to my suprise Dispatch heard me. The dispatcher said there was little static and she could hear me. So I am guessing I can mount this outside or just leave it where it is.....whats your ideas on this?

 

[TeRayCodA]

Without a properly tuned antenna system,you will eventually ruin the finals in that radio.How many watts are we talking here?

I would either build a J-pole,or buy one of the commercially available antennas.

Even at 5-10 watts,just transmitting on a mobile antenna without the proper ground plane, can damage the finals.

 

[N_Jay]

I am really confused I understand groundplane but just for S&G I took my 5/8 wave mobile antenna and mounted it to a L bracket. Set it on the floor and leaned it up against the wall, well I transmitted and to my suprise Dispatch heard me. The dispatcher said there was little static and she could hear me. So I am guessing I can mount this outside or just leave it where it is.....whats your ideas on this?

Why are you surprised? :roll:

Bad antennas still radiate. :twisted:

 

[BryanTheRed]

I stepped the watts down to five when it was in my truck I was transmitting at 60. SO theoretically I can mount outside and ground the antenna?? If not I am not understanding.....how can it be grounded on a vehicle and on a house and still mess things up?