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Author Topic: Laird Technologies Antenna  (Read 8409 times)
AB0RE
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Posts: 293




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« Reply #15 on: May 10, 2011, 09:23:11 AM »

Hey thanks for the reply K3GM. I guess I should have elaborated in that the reason I changed my mind is that my budget really only allows me to spend about two hundred dollars so the 2M option and the 1/4 wave really cut down on costs, as it stands I will only be spending approximately one hundred and seventy three dollars altogether. Once I get everything I'm going to start a thread on installation suggestions. I'm ordering both items from Universal Radio. If anyone can find them any cheaper let me know.

I think you'll be very happy with that set-up.  I'd take a roof-mounted quarter wave (on an NMO through-hole mount) over an antenna mounted on the trunklip anyday.   The quarter wave is very broadbanded so you shouldn't have any SWR issues.  And going with the NMO Mount you wont have to worry about crushed coaxial cable or water following the coax inside the vehicle as is common with mag mounts.  A final benefit is that this particular set-up will look sharp - many people won't even notice the antenna on your roof or they'll simply think it's a cell phone antenna.  If your vehicle is dark colored you can even get a black 1/4 wave whip to minimize the appearance of the antenna.

Even if you use a chassis punch you'll have to drill a hole for the bolt of the punch to pass through.  When you do that put some masking tape on the roof of your vehicle so the metal shavings don't scratch the area around the NMO mount.  Don't press too hard with the drill or you will dent the area around the hole.  And, when you tighten the NMO mount, really "choke up" on the wrench and don't torque down on the mount too much.  If you tighten the mount too much you'll dimple the area around your mount (keeping in mind your roof is slightly bowed and the mount is flat - when you tighten the mount too much it will flatten the roof around the mount a little bit.  If If this happens it's not the end of the world and probably only you will notice). 

It's easiest to loosen one corner of the trim in your vehicle, drill the hole above/near an overhead dome lamp opening, then snake the cable to the corner you loosened.  Take your time with the headliner and trim - too much force and you could break the plastic trim or cause permanent creases in your headliner.  If you didn't feel comfortable with this step, a dealership, bodyshop, or two-way radio dealer could probably help you out for minimal cost.  But if you'd rather do it yourself just relax and take your time and you'll be fine.

The Laird Technologies part # QW144 is a very good quarter-wave antenna and they're inexpensive... < $10 on eBay and elsewhere.   They are non-adjustable so there is nothing to go wrong. 

The mounts will come in different flavors, too.   RG58 vs RG8X... stranded vs center conductor... etc.  Your final choice won't matter a whole lot - just make sure to route the coaxial cable away from factory wiring, if possible, and don't pinch or kink the coax when you install it and you'll be in good shape.

73,
Dan / ab0re
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KJ4QYM
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Posts: 45




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« Reply #16 on: May 10, 2011, 05:24:03 PM »

Hey thanks for the reply K3GM. I guess I should have elaborated in that the reason I changed my mind is that my budget really only allows me to spend about two hundred dollars so the 2M option and the 1/4 wave really cut down on costs, as it stands I will only be spending approximately one hundred and seventy three dollars altogether. Once I get everything I'm going to start a thread on installation suggestions. I'm ordering both items from Universal Radio. If anyone can find them any cheaper let me know.

I think you'll be very happy with that set-up.  I'd take a roof-mounted quarter wave (on an NMO through-hole mount) over an antenna mounted on the trunklip anyday.   The quarter wave is very broadbanded so you shouldn't have any SWR issues.  And going with the NMO Mount you wont have to worry about crushed coaxial cable or water following the coax inside the vehicle as is common with mag mounts.  A final benefit is that this particular set-up will look sharp - many people won't even notice the antenna on your roof or they'll simply think it's a cell phone antenna.  If your vehicle is dark colored you can even get a black 1/4 wave whip to minimize the appearance of the antenna.

Even if you use a chassis punch you'll have to drill a hole for the bolt of the punch to pass through.  When you do that put some masking tape on the roof of your vehicle so the metal shavings don't scratch the area around the NMO mount.  Don't press too hard with the drill or you will dent the area around the hole.  And, when you tighten the NMO mount, really "choke up" on the wrench and don't torque down on the mount too much.  If you tighten the mount too much you'll dimple the area around your mount (keeping in mind your roof is slightly bowed and the mount is flat - when you tighten the mount too much it will flatten the roof around the mount a little bit.  If If this happens it's not the end of the world and probably only you will notice). 

It's easiest to loosen one corner of the trim in your vehicle, drill the hole above/near an overhead dome lamp opening, then snake the cable to the corner you loosened.  Take your time with the headliner and trim - too much force and you could break the plastic trim or cause permanent creases in your headliner.  If you didn't feel comfortable with this step, a dealership, bodyshop, or two-way radio dealer could probably help you out for minimal cost.  But if you'd rather do it yourself just relax and take your time and you'll be fine.

The Laird Technologies part # QW144 is a very good quarter-wave antenna and they're inexpensive... < $10 on eBay and elsewhere.   They are non-adjustable so there is nothing to go wrong. 

The mounts will come in different flavors, too.   RG58 vs RG8X... stranded vs center conductor... etc.  Your final choice won't matter a whole lot - just make sure to route the coaxial cable away from factory wiring, if possible, and don't pinch or kink the coax when you install it and you'll be in good shape.

73,
Dan / ab0re

Thanks for the suggestion, however, upon further review the antenna you suggested only goes up to 152Mhz, does that mean it won't receive anything above that? I need to be able to receive public safety frequencies between 150mhz-160mhz. Also, will the distance on this antenna be the same as something that's lets say 22" long etc. I like the extremely low profile but I want to make sure I'll be able to hit the right repeaters, even with 75 watts of power. Also, could you suggest a CB antenna that's the same profile as the quarter wave? All I can find are ones that are 48" or longer. Thanks again for the help!
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AB0RE
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« Reply #17 on: May 10, 2011, 07:43:03 PM »

Thanks for the suggestion, however, upon further review the antenna you suggested only goes up to 152Mhz, does that mean it won't receive anything above that? I need to be able to receive public safety frequencies between 150mhz-160mhz. Also, will the distance on this antenna be the same as something that's lets say 22" long etc. I like the extremely low profile but I want to make sure I'll be able to hit the right repeaters, even with 75 watts of power. Also, could you suggest a CB antenna that's the same profile as the quarter wave? All I can find are ones that are 48" or longer. Thanks again for the help!

The acceptable TX range goes to 152MHz under a 1.5:1 SWR.  It will receive good for a wide distance beyond the TX range stated in the specs of the antenna, including public service, NOAA, etc.

I believe the antenna should be around 19" or less in height.  If the specs say 22" somewhere they were incorrect.  The antenna has the lowest SWR around 147MHz, right smack dab in the middle of the voice portion of two meters.  It's a quarter wave, so the 234 / frequency equation applies here.  234 / 147 = 1.59' x 12 = 19".

In regards to the performance of a quarter wave, there is a lot of debate about that on the internet.  The "Gold Standard" two meter antenna is the Larsen (Laird) NMO-150 5/8 wave.  The 5/8 wave "in theory" has 3dB gain over the quarter wave which is about a half an S-unit difference.  In actual practice, I've pulled over to the side of the road before and switched between a quarter wave and a 5/8 wave and have not been able to tell the difference.  Additionally, when you are traveling at highway speeds the 5/8 wave, which is longer, will have considerable back-tilt which affects the performance as well.  Furthermoer, most people seem to mount 5/8 wave antennas on their trunk lids due to the additional height (so they can fit in their garage and what not)... but that's not the optimal place for the antenna.  The best place for teh antenna is right in the center of the roof so the ground plane is roughly equal in all directions and there are no metal obstructions that will block the signal path.  It's also wisest to put the antenna on the roof for an RF-safety standpoint as the antenna will be radiating above your head and you have a piece of metal to shield you from the radiation coming from the antenna.  Long story short, it's hard to not like a quarter wave antenna correctly mounted in the middle in the roof.  As you progress in your ham hobby you can certainly give the 5/8 wave a try, too, to see if you can tell the difference.  That's the other nice thing about NMO mounts - they are universal so it's easy to swap antennas out.

As far as a CB antenna with the same profile as the19" VHF..... you can't get something for nothing.  A quarter wave on CB would calculate out to 234 / 27MHz = 8.67' long.  Shrinking that down to under 19" is going to give you a severely compromised transmit and receive signal.    I have seen a CB antenna under 19" at copper.com, but just don't expect much from it (maybe line of sight to 2 miles maximum, I'd bet). 

Many have suggested the Larsen NMO27 for CB Frequencies.  I've had that antenna and also a Wilson 1000.  In switching back and forth between the two antennas the Wilson was consistenly about 1.5 S-units stronger, a whopping 9dB!  Of course the Wilson is 64" tall and I believe the NMO 27 is around 48".

I'll probably get shot for saying this here, but an okay compromise antenna for CB is the one with the spring at the base, a thicker lower shaft that goes to the center coil (black piece), then to a thin "stinger" at top.  This antenna is probably 20-24" tall and, sadly, only available as a mag mount.  It won't hold a candle to the Wilson1000, but it'll do okay in a pinch.  The center loaded antennas like this one are a bit more effecient than a base loaded antenna of the same length.  Just keep in mind there are many different manufacturers of this antenna.  Radio Shack carries one for $35.  You can get a Pyramid brand one at Wal-Mart for about $10.  I believe Uniden also offereed this antenna a while back.  You typically get what you pay for and the real cheap ones will rust out quickly, particularly around the spring area.

Good luck on "the hunt" for your new antennas.

73,
Dan / ab0re
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K3GM
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« Reply #18 on: May 11, 2011, 04:13:57 AM »

.................Many have suggested the Larsen NMO27 for CB Frequencies........... 

....and as a bonus, with a second whip ($15), you can run that coil on 10 meters.  I use one for 10m fm ops from the car.  You can also stay with your NMO mounting standard as well.
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KJ4QYM
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« Reply #19 on: May 11, 2011, 07:17:47 AM »

Ok so, hopefully this will be my last question in this thread but, I'm assuming that neither the radio or antenna I will be purchasing come with any sort of coaxial cabling for the antenna to hook up to the transceiver. What's the best coaxial I should get for my setup, preferably cheap Smiley
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AB0RE
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« Reply #20 on: May 11, 2011, 08:22:48 AM »

Ok so, hopefully this will be my last question in this thread but, I'm assuming that neither the radio or antenna I will be purchasing come with any sort of coaxial cabling for the antenna to hook up to the transceiver. What's the best coaxial I should get for my setup, preferably cheap Smiley

Most ham vendors carry the Larsen NMO mount, part # "NMOK", which ain't bad.  It'd be under 15 bucks.

The mounts from Antenex (now Laird), MaxRad (now PCTel) are also good.  There are a variety of options available - the big difference is that some only require a 3/8" hole and others the 3/4" hole - I prefer the 3/4" hole as they can be tightened / removed from outside the vehicle, and provide a good mechanical connection.  The outer nut of the NMO mount can also vary in its material composition - brass, nickel, stainless steel, etc.  None of these options will rust, so you should do okay whatever you choose. 

73,
Dan / ab0re
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K3GM
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« Reply #21 on: May 11, 2011, 10:28:41 AM »

Ok so, hopefully this will be my last question in this thread but, I'm assuming that neither the radio or antenna I will be purchasing come with any sort of coaxial cabling for the antenna to hook up to the transceiver. What's the best coaxial I should get for my setup, preferably cheap Smiley

Order the mount with the coax already attached to the mount.  As Dan pointed out, the NMOK will have provide that for you. and even has the PL-259 attached.  $15-$18 plus shipping.  I like Ham Radio Outlet, but there are many vendors to choose from out there. Don't forget the punch or hole saw.  Antennex make a 3/4 hole saw, but I prefer the Greenlee punch.  The resulting hole looks like it was machine punched; perfect; sharp, no burrs.
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KJ4QYM
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« Reply #22 on: May 11, 2011, 11:05:36 AM »

Ok so, hopefully this will be my last question in this thread but, I'm assuming that neither the radio or antenna I will be purchasing come with any sort of coaxial cabling for the antenna to hook up to the transceiver. What's the best coaxial I should get for my setup, preferably cheap Smiley

Order the mount with the coax already attached to the mount.  As Dan pointed out, the NMOK will have provide that for you. and even has the PL-259 attached.  $15-$18 plus shipping.  I like Ham Radio Outlet, but there are many vendors to choose from out there. Don't forget the punch or hole saw.  Antennex make a 3/4 hole saw, but I prefer the Greenlee punch.  The resulting hole looks like it was machine punched; perfect; sharp, no burrs.

Thanks for clarifying, also I tried searching for the Greenlee punch and there were so many vague results I got back that I couldn't really tell what was what, I found the Antennex though for like 30-40 dollars. Maybe you can directly link me to a place where I can buy the Greenlee punch as well so I can see which one is more cost effective. Thanks!
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AJ3O
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« Reply #23 on: May 11, 2011, 02:56:26 PM »

Most Lowes and I think Home Depot stores carry those Green Lee tools in the electricians isle.
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K3GM
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« Reply #24 on: May 11, 2011, 05:24:36 PM »

www.all-spec.com, you want their 730BB34 (Greenlee #730BB-3/4) $34.63
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W3LK
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« Reply #25 on: May 12, 2011, 05:40:27 AM »

www.all-spec.com, you want their 730BB34 (Greenlee #730BB-3/4) $34.63

I can tell it's been a LONG time since I priced one. I bought mine back in the late 60s and paid something like $6 for it. I have no idea how many holes it has made over the last 40+ years, but it must be a couple of hundred.
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KJ4QYM
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Posts: 45




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« Reply #26 on: May 12, 2011, 07:19:42 AM »

www.all-spec.com, you want their 730BB34 (Greenlee #730BB-3/4) $34.63

I can tell it's been a LONG time since I priced one. I bought mine back in the late 60s and paid something like $6 for it. I have no idea how many holes it has made over the last 40+ years, but it must be a couple of hundred.
www.all-spec.com, you want their 730BB34 (Greenlee #730BB-3/4) $34.63

I ended up going to Home Depot, they didn't carry Greenlee anymore they carry Cline or Kline or something like that, basically the sales person said it was the same thing just with another name on it, cost me $42.50 with tax so I'm happy I didn't have to wait for that in the mail.   Thanks for all the help guys

P.S.

When I get around to making the 3/4" hole in my roof, the electrician at Home Depot said I would need a drill to make a pilot hole, how big will this hole need to be and what drill bit should I use?
« Last Edit: May 12, 2011, 07:24:38 AM by KJ4QYM » Logged
K0BG
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« Reply #27 on: May 12, 2011, 08:47:57 AM »

That depends on the bolt size in the punch.

There are two things I don't like about punches, albeit I still use them.

One is the fact that most punches are in pipe sizes, not the hole they punch. If you use a 3/4 inch pipe punch, the hole will be too big for an NMO. Forewarned, forearmed! Just make sure you get a 3/4 inch CHASSIS punch, not a 3/4 inch pipe punch.

The other is, you need to get to the under side of the sheet metal. That's okay if you're doing a trunk lid, but not handy if you're doing a roof install. Several folks sell a special shouldered drill just for the purpose. You only need about 1/2 inch of underneath clearance. If you're handy, snaking the coax down a pillar isn't difficult as it would appear to be.
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KJ4QYM
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« Reply #28 on: May 12, 2011, 09:12:37 AM »

That depends on the bolt size in the punch.

There are two things I don't like about punches, albeit I still use them.

One is the fact that most punches are in pipe sizes, not the hole they punch. If you use a 3/4 inch pipe punch, the hole will be too big for an NMO. Forewarned, forearmed! Just make sure you get a 3/4 inch CHASSIS punch, not a 3/4 inch pipe punch.

The other is, you need to get to the under side of the sheet metal. That's okay if you're doing a trunk lid, but not handy if you're doing a roof install. Several folks sell a special shouldered drill just for the purpose. You only need about 1/2 inch of underneath clearance. If you're handy, snaking the coax down a pillar isn't difficult as it would appear to be.
Ok I am pretty sure it didn't say pipe anywhere on the packaging. Second, I thought I could just remove the dome light to gain access to the other side of the roof. Third, I don't have the money to buy any other special tools, as it is I'm going to have to borrow a drill. I'm not Mr. Handy Man Lol. I planned to snake the coax through the headliner to a pillar and down into the transceiver. Also, I still need to know what size pilot hole I need to drill and the drill bit I'll need, 1/2", 5/8", what? Lol

P.S.

The bolt size I guess is 3/4", thats the sizing on the packaging.
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K3GM
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« Reply #29 on: May 12, 2011, 10:50:59 AM »

The best thing to do is to mic the O.D. of the punch before you use it.  As Alan said, a 3/4 pipe punch will give you a hole too large to use.  I've come up with all sorts of ways to thread the punch onto the bolt when it's out of reach.  Taping the punch half to a coat hanger and fishing it up into the headliner works good with someone outside to spin the bolt and catch catch a thread.  Definitely a two man operation!  Patience, and have fun.
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