Multiple Antenna Question for 2M/70CM

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ccg_ga

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The timer has the relay built in. Bypass the relay completely, remove it.
Got it, that makes sense now that I think about it. I ordered the SDT1230-014 model directly from Lind.

In removing the relay I'll need to join the 8 ga positive battery wire that ran to pins 30 and 87 on the relay. While I know it's not optimal, I am thinking that I will use copper butt terminals to connect the two runs and top them off with marine heat shrink and adjust the flex tubing accordingly. Otherwise I would need to pull the wire out and re-run it, redo the spiral wrap/flex tubing, firewall entry, etc. Is this a horrible idea or should I just re-run it instead?

Those antennas are beasts. And not in a good way. The base is very wide and sticks up quite a bit. If it hits a branch, something is going to break. Might be the branch, might be the antenna, might be the mount. If you go with that antenna, keep it down low so the spring will protect the whip. Keep the base down out of the way.
Or, better yet, go with the Larsen with the spring base lower down.
You want to keep it as far away from your transmit antennas as possible. As @mmckenna said, you're running out of room.
Will it will be far less than optimal, will your SDS 100 receive what you want using the stock rubber duckie antenna on the radio inside the vehicle? If that will give you acceptable performance, you'd have one less mounting problem and that would mitigate RF overload.
I think I got a little excited about adding the scanner antenna. I didn't realize that the Larsen NMO 150/450/758 had a spring base from the pictures I was looking at on Antenna Farm. I looked at the ArcAtenna site earlier and realized that it indeed does.

So in comparing the bands the 150/450/758 to the bands I want to monitor it likes up really well with the exception of a gap between 406 and 430 (where the antenna is tuned for 430-520). Most of what I was interested in monitoring between 406-430 are national interop, federal disaster management and SAR and some of the national parks in the southeast are on those frequencies. That being said, does it in reality not really matter that the antenna is "tuned" for 406-430 and what I will actually receive provided there are strong signals? That whole thing may be a wash and the 150/450/758 is the antenna to go with.

I see the 150/450/758 is 16.5", so even if I mount it on the top of the tire carrier like I was thinking about it will still be almost totally covered by the spare tire and won't rise above the roof line. Will this impact RX significantly, or given the options (or lack thereof) will the antenna perform decently well for RX? I could still rig up the mount I was thinking about to extend slightly above the roof line since the antenna does have the spring base.

And last one on this - does ground plane matter for RX only? I have read several threads on this and some say yes, some say no. I wasn't sure which one was more accurate.

Thanks for the continue help gents, it is much appreciated.
 

mmckenna

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Got it, that makes sense now that I think about it. I ordered the SDT1230-014 model directly from Lind.

In removing the relay I'll need to join the 8 ga positive battery wire that ran to pins 30 and 87 on the relay. While I know it's not optimal, I am thinking that I will use copper butt terminals to connect the two runs and top them off with marine heat shrink and adjust the flex tubing accordingly. Otherwise I would need to pull the wire out and re-run it, redo the spiral wrap/flex tubing, firewall entry, etc. Is this a horrible idea or should I just re-run it instead?
If it was mine, I'd rerun that section of wire. Butt terminals can be flakey, especially on something like 8 gauge. Yeah, it would work if that is your only option. For a field expedient fix, it would be fine, but for long term reliability, I'd make it a continuous run.

I think I got a little excited about adding the scanner antenna. I didn't realize that the Larsen NMO 150/450/758 had a spring base from the pictures I was looking at on Antenna Farm. I looked at the ArcAtenna site earlier and realized that it indeed does.

So in comparing the bands the 150/450/758 to the bands I want to monitor it likes up really well with the exception of a gap between 406 and 430 (where the antenna is tuned for 430-520). Most of what I was interested in monitoring between 406-430 are national interop, federal disaster management and SAR and some of the national parks in the southeast are on those frequencies. That being said, does it in reality not really matter that the antenna is "tuned" for 406-430 and what I will actually receive provided there are strong signals? That whole thing may be a wash and the 150/450/758 is the antenna to go with.

I think it's going to work fine. Usually the antenna frequency coverage is based off a know SWR range, as in the antenna will perform with 2.0:1 or less across a set spectrum. It'll work outside that. Federal UHF band, and the few non federal users down that way, are not very common. I've never heard any use of the federal interop channels down that low, but maybe I've never been in the right location at the right time.

I see the 150/450/758 is 16.5", so even if I mount it on the top of the tire carrier like I was thinking about it will still be almost totally covered by the spare tire and won't rise above the roof line. Will this impact RX significantly, or given the options (or lack thereof) will the antenna perform decently well for RX? I could still rig up the mount I was thinking about to extend slightly above the roof line since the antenna does have the spring base.

And last one on this - does ground plane matter for RX only? I have read several threads on this and some say yes, some say no. I wasn't sure which one was more accurate.

Thanks for the continue help gents, it is much appreciated.
It'll work. Ideal situation would be to have a 1/4 wave ground plane under the antenna at your lowest frequency. That's not going to happen in your install, so just do the best you can.
 

prcguy

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The Laird you are looking at needs a lot of ground plane, otherwise toss out the advertised frequency ranges. I have a couple and I like them in the middle of my truck roof but they will not work on a top bed rail mount and the VSWR goes way up. On the other hand my COMPACTenna Scan III works well on the top bed rail because it wants less ground plane.

If you search RR you will find a recent test I did between the Laird tri-band, Larsen Tri-band and the COMPACTenna Scan III, but in the middle of my truck roof. The COMPACTenna pulls further ahead of the others when the ground plane is lacking.


Oh isn’t that the truth. The rear locker won’t engage right now so I’m sure that is going to eat up some
more $.

Do you think I can get away with mounting the scanner antenna on the front fender or would it be best to put it up high on the rear tire carrier?

Good to hear on the RG58. I can use the stripper and crimp tools for this project too!
 

ccg_ga

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If it was mine, I'd rerun that section of wire. Butt terminals can be flakey, especially on something like 8 gauge. Yeah, it would work if that is your only option. For a field expedient fix, it would be fine, but for long term reliability, I'd make it a continuous run.
Got it. I figured I should just re-run it after I added that post. This is a good opportunity to add the high-temp shielding, so I'm looking at the Wire Care page now. I measured the diameter of all of the cables + flex split tube at it is right at 1.5". I need about 3' feet of it to cover from the firewall boot to above the intake manifold on the firewall.

Should I go with the extreme temp braided shielding (rated to 1,200 degrees) such as one of these:

Insultherm Resin Coated Fiberglass Sleeving - WireCare.com
https://www.wirecare.com/category/shielding/heat-shielding/insultherm-ultraflexx-pro

Or the general purpose which is rated to ~ 257 degrees. The engine itself runs about 210 normally.

Flexo Clean Cut - 1 1/2" - WireCare.com

I see that some of these shieldings say they can be cut with scissors - is just a sharp pair of regular scissors sufficient?
 

ccg_ga

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The Laird you are looking at needs a lot of ground plane, otherwise toss out the advertised frequency ranges. I have a couple and I like them in the middle of my truck roof but they will not work on a top bed rail mount and the VSWR goes way up. On the other hand my COMPACTenna Scan III works well on the top bed rail because it wants less ground plane.

If you search RR you will find a recent test I did between the Laird tri-band, Larsen Tri-band and the COMPACTenna Scan III, but in the middle of my truck roof. The COMPACTenna pulls further ahead of the others when the ground plane is lacking.
Thanks for the suggestion. I did not come across this antenna when reading through other posts, so I will check it out and with the test you mentioned. I appreciate it!
 

mmckenna

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Got it. I figured I should just re-run it after I added that post. This is a good opportunity to add the high-temp shielding, so I'm looking at the Wire Care page now. I measured the diameter of all of the cables + flex split tube at it is right at 1.5". I need about 3' feet of it to cover from the firewall boot to above the intake manifold on the firewall.

Should I go with the extreme temp braided shielding (rated to 1,200 degrees) such as one of these:

Insultherm Resin Coated Fiberglass Sleeving - WireCare.com
https://www.wirecare.com/category/shielding/heat-shielding/insultherm-ultraflexx-pro

Or the general purpose which is rated to ~ 257 degrees. The engine itself runs about 210 normally.

Flexo Clean Cut - 1 1/2" - WireCare.com

I see that some of these shieldings say they can be cut with scissors - is just a sharp pair of regular scissors sufficient?

SAE rated wire used for engine sensors usually has an insulation rating 125ºc to 200ºc. That's for things that are actually connected to the engine, like sensors. Even things like oxygen sensors attached to high temperature devices like exhaust systems.

You really only need to protect the wire from abrasion, that's the role of the split loom covering. Looks are secondary. I think either of those would work just fine for what you are doing. However, the cost difference is minimal.

Regular scissors should work just fine.
 

mmckenna

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Thanks for the suggestion. I did not come across this antenna when reading through other posts, so I will check it out and with the test you mentioned. I appreciate it!
I'd trust PRCGUY on that, as he's done some pretty extensive testing with those antennas.

My only concern would be that it is not flexible in any way, and any contact with a branch is going to break something. If the antenna is mounted below your roof line, it's probably going to be safe.
 

ccg_ga

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I'd trust PRCGUY on that, as he's done some pretty extensive testing with those antennas.

My only concern would be that it is not flexible in any way, and any contact with a branch is going to break something. If the antenna is mounted below your roof line, it's probably going to be safe.
I read through @prcguy's test thread this morning, and while some of the aspects of the testing are above my current knowledge level the chart/data, needing less ground plane and performing better in an off-center/corner mounting location along with the overall band coverage in relation to what I am looking to monitor makes sense to me and it sounds like a good option.

I did indeed think about the fact that the COMPACTenna is rigid and it's going to fly off or break if it directly hits anything somewhat rigid. However, the distance from the black NMO mount to the top tread on the spare tire is right around 13". I think I can fit it back there and it would still have protection from a direct impact. As I have learned I'm not going to get max performance out of any antenna given the mounting location, but I think I am going to give it a shot - and remove the CB antenna first.

89399

I picked out some crimp style SMA male and BNC male connectors as well. The SDS100 has a SMA female connector, so as long as the threaded collar on the SMA connector will fit within this little raised ridge on the SDS100 I'm going to try and go that route so I don't have to use the BNC adapter. If it doesn't, then I'll go with the BNC connection.

Thanks for the feedback on the tube shielding as well.
 

mmckenna

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I think that'll work fine.

Someone may bring up the point that your tire has steel in the belts. Yeah, that may impact performance, but sometimes you do the best you can and live with it. You could spend the next 20 years engineering out a "perfect" solution to mount multiple antennas on a jeep, and a way to protect them from trail damage. At an early point, the cost of all that design work is going to far exceed the cost of a replacement antenna.

It's a hobby, enjoy it. Don't forget to have some fun along the way.
 

prcguy

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Hmm, you could punch a 3/4" hole in the top of the tire and install an NMO mount so the claws grip the steel belts in the tire. That would be an adequate ground plane for the COMPACTenna. Then if something hits the COMPACTenna the tire would flex and protect the antenna. Problem solved. Radio performance first, everything else comes second, including the need for a spare tire.


I think that'll work fine.

Someone may bring up the point that your tire has steel in the belts. Yeah, that may impact performance, but sometimes you do the best you can and live with it. You could spend the next 20 years engineering out a "perfect" solution to mount multiple antennas on a jeep, and a way to protect them from trail damage. At an early point, the cost of all that design work is going to far exceed the cost of a replacement antenna.

It's a hobby, enjoy it. Don't forget to have some fun along the way.
 

mmckenna

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Hmm, you could punch a 3/4" hole in the top of the tire and install an NMO mount so the claws grip the steel belts in the tire. That would be an adequate ground plane for the COMPACTenna. Then if something hits the COMPACTenna the tire would flex and protect the antenna. Problem solved. Radio performance first, everything else comes second, including the need for a spare tire.
Exactly.

I had a coworker with an old M38 jeep with a Buick V6. He ran the Rubicon trail a few times. He was an active ham, carried HF, 2 meters and CB onboard.

His 2 meter antenna was smack dab in the center of the hood. Function over form. The jeep looked like crap, one of the fenders was welded back on along the trail with 2 batteries some coat hanger for rod and some jumper cables. He didn't care what anyone though about his antenna install.

It is by far the coolest Jeep I've ever seen in my life. I hope to have a jeep that looks that bad at some point in my life.
 

ccg_ga

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Hmm, you could punch a 3/4" hole in the top of the tire and install an NMO mount so the claws grip the steel belts in the tire. That would be an adequate ground plane for the COMPACTenna. Then if something hits the COMPACTenna the tire would flex and protect the antenna. Problem solved. Radio performance first, everything else comes second, including the need for a spare tire.
Haha, that got a real LOL when I read it. Those tires are bias-ply so the belting is pretty much all nylon or polyester, but I think we should give the tire mount a shot :)! I think I need a thick NMO mount though to pass through the tire lug.. At least I have some good radio gear to get help when I break down on the trail or blow out a tire!

When I decided to go with these tires multiple people told me don't go with a bias-ply tire, they ride like hell.. As long as you keep them aired up to about 30 PSI and give them a little time to warm up on the road they ride just fine for a real off-road tire. They crush it on the trail as well. Just like any hobby, it's about what works for you as @mmckenna said.

Aside from all that, my radio and scanner setup is light years beyond what I would have come up with on my own thanks to you guys!
 

ccg_ga

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@mmckenna @prcguy

I have spent the past 45 mins trying to figure this out on my own, but still haven't.

I want to use this Laird mounting NMO mounting bracket for the scanner antenna - https://www.theantennafarm.com/catalog/laird-technologies-lbmb9034-3854

From looking at the Larsen NMOKHFUD mounts I used on the fender antennas I'm guessing I need a thicker through-the-hole NMO mount. So I checked out the two "thick" versions and they look a little too long for the thickness of that mounting bracket which is 0.225" (5.715 mm)?. As I see on the Larsen data sheet for these mounts they had different types of RG-58 coax, but it doesn't list the NMOKHFUDTHK.

Larsen NMOKHFUDTHK
Larsen NMOKHFCXTHK (CX RG-58A/U)

If one of these will work, which coax is best to go with? I also see that they make a NMOHFMID "mid" thickness mount with the connector only, but it appears to be out of stock or has a minimum order quantity of 18 at ArcAntenna.
 

mmckenna

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The mirror mount bracket from Laird is 0.138" thick.

The NMO mounts will handle "up to" 1/2" thick mounts. So, you'll be good.

The difference in the cable is the outer shield.
The CX is a single shield RG-58A/U with a stranded center conductor. It'll be more flexible and easier to route in your vehicle.
The UD is a dual shield RG-58U with a solid center conductor and dual shield. It'll perform slightly better, especially on higher frequencies, but the solid center conductor can -sometimes- be problematic in high vibration/high flex environments. The solid center conductor won't like making sharp turns.

The amount of performance difference is very slight, and unlikely you'd ever notice it. The more flexible RG-58A/U might be a better choice if the antenna is mounted on the tailgate/spare tire mount that will get occasionally opened/closed.
 

ccg_ga

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The mirror mount bracket from Laird is 0.138" thick.

The NMO mounts will handle "up to" 1/2" thick mounts. So, you'll be good.

The difference in the cable is the outer shield.
The CX is a single shield RG-58A/U with a stranded center conductor. It'll be more flexible and easier to route in your vehicle.
The UD is a dual shield RG-58U with a solid center conductor and dual shield. It'll perform slightly better, especially on higher frequencies, but the solid center conductor can -sometimes- be problematic in high vibration/high flex environments. The solid center conductor won't like making sharp turns.

The amount of performance difference is very slight, and unlikely you'd ever notice it. The more flexible RG-58A/U might be a better choice if the antenna is mounted on the tailgate/spare tire mount that will get occasionally opened/closed.
I read the wrong side of the dimension on the drawing... NMOKHFCXTHK it is. Thank you sir.
 

ccg_ga

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All the parts finally showed up today. There was a delay on the Lind timer by about a week because they didn’t have a part to finish assembly.

More details on the install next week..
 

mmckenna

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I think you'll be happy with the Lind timer. Very common to use those on the public safety side. I use them on my own personal vehicles, and I'd not do an install without one. Since I'm usually sitting on one channel, I never have to touch my radios. It turns on when I start the vehicle, and will turn the radios off about 30 minutes after I shut the engine off.
 

mmckenna

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@mmckenna

I think it will be a good setup. I now see why the switch is ‘momentary’ as well.

Can I remove the green connector on the timer? I was thinking the 8 ga copper terminals for the positive wire may not fit?
I don't know if #8 will fit in there. The models I use have screw terminals that make connection a bit easier. Most of the time I just use it for feeding multiple ignition sense circuits on radios, and/or feeding a radio that doesn't have ignition sense.

What you can do is use this to drive your existing relay, and leave the rest of your stuff in place. If you wanted to get fancy, you could ~probably~ desolder that screw terminal connector and use the screw terminals underneath. Or, get some wire furrels Robot Check
and see if that will work. While it doesn't magically shrink the wire, it does make the connection a bit easier.
 
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