Multiple Antenna Question for 2M/70CM

ccg_ga

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I am looking at installing an ICOM IC-2730A mobile radio for 2M/70cm in my Jeep for off-road communications. I currently have both a Midland GRMS radio (MXT400) and an older Cobra CB. The MXT400 is connected to a Midland MXTA11 6db gain antenna which is mounted to my rear tire carrier and near the Firestik antenna for the CB.

My question is about the 2M/70cm antenna for the IC-2730A - if I mount it also on the tire carrier next to the GMRS and CB antenna's is it possible to cause decreased performance either in radiance, interference, etc? I wasn't sure since the GMRS frequencies (462-467 MHz) were somewhat near the upper end of the 70cm band.

Any suggestions for the 2M/70cm antenna and coax would be much appreciated as well!

This photo is of my current antenna setup:

87936
 

ccg_ga

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Based on a couple of hours reading after I posted this I now understand that mounting any antenna in this location is a horrible idea.

It looks like my only option is to mount it on one of the front fenders - so still interested in any fender/lip mount or antenna suggestions.
 

ladn

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My question is about the 2M/70cm antenna for the IC-2730A - if I mount it also on the tire carrier next to the GMRS and CB antenna's is it possible to cause decreased performance either in radiance, interference, etc? I wasn't sure since the GMRS frequencies (462-467 MHz) were somewhat near the upper end of the 70cm band.

Any suggestions for the 2M/70cm antenna and coax would be much appreciated as well!
Your existing antennas are already compromised because of their location and lack of an adequate ground plane (especially the CB antenna).

I know a Jeep install doesn't give you a lot of options. I seen other CB antennas installed on Jeep's rear cargo door hinge. This would open up a space for the addition of an amateur VHF/UHF antenna.

As for antenna and mount suggestions:

ANTENNA: Larsen NMO 2/70​
MOUNT: Larsen (or PC Tell) NMO 3/4 mount on an "L" bracket. These are top quality, professional grade, mounts and come with about 17' of cable. Stay away from Browning and other off shore mounts. There's not much price difference, and the Larsen or PC Tell mounts are far superior.​
(I'll PM you with a few more suggestions)
 

ccg_ga

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Ladn - Thank you, I greatly appreciate the info and recommendations. I did some more reading after I posted this and did understand quite quickly that that tire carrier mount was a horrible location.

I'm guessing that I need to move the GRMS antenna as well. I'll check out your other suggestions via the PM.
 

mmckenna

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Yeah, you have a number of issues there that would be concerning.

As ladn said, there's not a lot of good options on a Jeep, but there are things you can do to improve performance.

Big issue I see is that you have two transmitting antennas already in that space, and as it is, they are too close together. The transmitted power from one antenna is going to get into the other radio. If the coupling is good enough, you can potentially damage the other receiver. While you may not be suffering from that already, you do run the risk of it happening. I'd really, strongly, suggest moving the GMRS antenna, and preferably replacing it with a more appropriate design.

Adding a 2 meter/70 centimeter band antenna to that same location is just going to increase the likelihood of damage happening to one of the radios.

Here's what I'd recommend you do:

CB:
Keep the antenna where it is if it's working for you. Again, not a lot of good options on a Jeep.

GMRS:
Move that antenna away from the CB antenna. Ideally you need to switch to a ground independent design antenna. A 6dB gain antenna is not ground independent, it wants to see a ground plane under the antenna to work properly and give you low SWR. I'd recommend a Larsen ground independentUHF antenna. https://www.theantennafarm.com/catalog/larsen-nmo450chw-833 or a Laird half wave: https://www.theantennafarm.com/catalog/laird-technologies-b4502ns-3235
Unless you can mount the antenna with a proper ground plane, as in dead center on the hood or fabricating a ground plane on the roof, that's going to work better.
Now you also need to move it away from the CB antenna. A popular choice is to mount them off the edge of the front fender and far enough forward to keep them away from the windshield frame. I've seen other Jeepers use these before with success: https://www.theantennafarm.com/catalog/jeep-wrangler-2007-2020-8813 or one of these with a suitable NMO mount: https://www.theantennafarm.com/catalog/laird-technologies-sbt3400-3857
Important part is to make sure the underside of the NMO mount is properly sealed. The standard NMO mounts are designed to go through a vehicle roof and not have their underside exposed to the elements. Unless they are sealed properly, the copper in the coaxial cable will get wet and quickly corrode.

Amateur radio:
Same thing, keep it away from the other antennas. Mounting the GMRS antenna on one side of the hood and the 2/70 antenna on the other is a good approach. The same mount can be use, but you'll obviously want a suitable antenna. Again, Larsen has an excellent track record and are much better built than the low buck Tram/Browning or other Cheap Chinese Antennas:
or

Your antennas are the most important part of your system. You do need to keep an appropriate level of distancing between the antennas, and that will depend on a number of factors. Receiver damage is a real issue when you have antennas that closely spaced without some appropriate filtering.
Also, having antennas closely spaced and in near proximity to other vehicle steel will impact performance. You want the antennas, especially the VHF and UHF antennas, out in the clear away from other antennas and the body.
 

mmckenna

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Check out this thread here. Most of the stuff is going to apply to your situation. Photos of the install towards the bottom of the thread:
 

ccg_ga

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Check out this thread here. Most of the stuff is going to apply to your situation. Photos of the install towards the bottom of the thread:
Thank you as well - the links are very helpful as there are so many options pout there for antennas and mounts. Based on your post and ladn's it sounds like the Larsen NMO 2/70B is the antenna to go with for the ICOM radio. I am going to go with that one and use the fender mounts on both sides.

I have 2 other questions so far:

1) Is placing either the GRMS or ham antenna on the passenger side fender a problem depending on how far away from the factory FM radio antenna? I saw in one of the other posts I was reading that someone suggested that it needs to be at least 18" away from the FM radio antenna/

2) What is the best way to seal the NMO connections on the mounts?

I'll check out the other post as well. This info is very helpful and I appreciate it!
 

bharvey2

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+ 1 on the recommendation on a half wave antenna. I've had a few installations such as my wife' Ford Edge (glass roof) where mounting over a suitable ground plane can't be done. A 1/2 wave antenna is more forgiving in those situations.
 

mmckenna

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I have 2 other questions so far:

1) Is placing either the GRMS or ham antenna on the passenger side fender a problem depending on how far away from the factory FM radio antenna? I saw in one of the other posts I was reading that someone suggested that it needs to be at least 18" away from the FM radio antenna/
If it was me, I'd put the GMRS antenna on the same side as the AM/FM radio antenna. UHF will have a bit less of an impact on the FM radio receiver and the desensitization it'll cause. But yeah, you still need spacing between the antennas. The VHF side of the ham radio is closer to the FM broadcast band, so having it on the opposite side would make some sort of valid sense. But, even with that, it's entirely possible that when you key up either GMRS or Amateur radio the FM receiver will lose signal and the FM broadcast station you are listening to will go blank.

2) What is the best way to seal the NMO connections on the mounts?
The antenna to NMO mount interface part is easy. The antennas will come with an O-ring or gasket that will seal it.
If you are referring to the point where the coaxial cable enters the mount, the best way to do that is to use the Larsen NMO-HF style mounts and then slide a piece of marine grade heat shrink over the coax. Slide it up and over the mount where the cable enters and shrink it. The hot melt adhesive inside the tubing will flow and seal it up nicely.
 

ccg_ga

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@mmckenna @ladn

Ok, thanks to the help from both of you I think I am getting close on the Icom Ham rig.

Here is what I am thinking so far:

Antenna - Larsen NMO2/70B - https://www.theantennafarm.com/catalog/larsen-nmo2-70b-1712
Antenna Bracket/Mount - Laird SBTB3400 Straight NMO Bracket w/ 3/4" Hole - https://www.theantennafarm.com/catalog/laird-technologies-sbtb3400-3858
Larsen NMO-K 3/4" Mount - Amazon.com: Larsen Original NMO-K 3/4'' Permanent Hole Mount with 17' RG58A/U Cable and UHF Male PL259 Connector: Electronics or https://www.theantennafarm.com/catalog/larsen-nmokhfud-1125

My Jeep is the older TJ (2004) model, so the flat bracket should work fine with my hood/fenders.

On the NMO mount and coax - Is the NMO-K mount the correct one (I think it is)? Also, for optimal performance should I order the coax without the PL-259 connector attached, then cut it to the right length and attach the PL-259 plug?

Is this a good combo to go with?

Going back to the GMRS Antenna:

The specific antenna I currently have is the Midland MXTA26 actually, not the MXTA11. Several people asked about the need for a ground plane on the MXTA26 and the responses say just attaching it to metal is a sufficient ground plane. I realize that may be incorrect information, but I wanted to ask if it is correct as that will save me a few dollars if I don't need to purchase another antenna.

If it is incorrect, then I'll probably go with the Larsen NMO450CHW. I looked at a couple of spec sheets and I couldn't verify if it also uses the name 3/4" NMO mount that the NMO2/70B does. Basically I'm trying to figure out if I can use the Laird SBTB3400 3/4" bracket with the NMO450CHW as well?
 
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ccg_ga

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Disregard the GRMS antenna question - your other posts in the Jeep JK thread answered that. Larsen it is for the GMRS antenna as well.
 

mmckenna

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Correct part number, but when you go to the Amazon page, it shows an LM mount, not an NMO mount.
Could be the seller used the wrong photo and the correct part number, or could be the right photo and the wrong part number.
That alone would stop me from buying from that seller. If they don't know the difference between an NMO mount and an LM mount, they probably won't know much else about what they are selling.
 

mmckenna

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My Jeep is the older TJ (2004) model, so the flat bracket should work fine with my hood/fenders.
OK, just make sure you pay attention to grounding the bracket when you install it.
Yes, the antennas I suggested are "ground independent" antennas, but they work better with ground. The easy thing to do is put a star washer under the mount when you screw it down, or scrape off a bit of paint to make sure you have good contact between the bracket and the body.

On the NMO mount and coax - Is the NMO-K mount the correct one (I think it is)?
See my post above. Getting the wrong photo/part number is a big red flag to me when I'm purchasing something on line.

The concern I have is that the NMO-K mounts like that are intended for going through the body of a vehicle where the connection point for the coaxial cable is protected inside the vehicle. Using those mounts on a bracket where the underside will be exposed to water, road salts, etc, is not a good idea. That'll corrode the coaxial cable in short order and you'll end up replacing them soon. While the NMOHF style mounts are overkill for GMRS/ham stuff, they do have the benefit of the coaxial connection being made inside the mount where it's better protected. I'd recommend one of those. Also, make a run by Harbor Freight or a marine supply store and get some 1/4 or 5/16" diameter marine grade heat shrink tubing. You'll need about 6 inches. The marine grade heat shrink tubing has a hot melt adhesive inside that will liquify when you shrink the tubing. That will seal the point where the coaxial cable enters the mount. Just cut 2 or 3 inches of the stuff and slide it over the coaxial cable so it's covering the point where the coax enters the underside of the NMO mount. Heat it up with a heat gun (or carefully with a lighter) and shrink it in place.


Also, for optimal performance should I order the coax without the PL-259 connector attached, then cut it to the right length and attach the PL-259 plug?
Yes, absolutely. The ideal length of coaxial cable is the amount you need to run from the antenna to the radio with a bit of slack in case you ever need to re-terminate the cable. Also, it's much easier to route the cable without the connectors in place.
Is this a good combo to go with?

Going back to the GMRS Antenna:

The specific antenna I currently have is the Midland MXTA26 actually, not the MXTA11. Several people asked about the need for a ground plane on the MXTA26 and the responses say just attaching it to metal is a sufficient ground plane. I realize that may be incorrect information, but I wanted to ask if it is correct as that will save me a few dollars if I don't need to purchase another antenna.
No, it's a 5/8 wave colinear antenna. MicroMobile® MXTA26 6db Gain Whip Antenna | Midland Radio
It does require a ground plane. Without the ground plane, the antenna will probably not tune up properly, and the coaxial cable will start radiating RF and can cause all kinds of headaches.
It was good to suspect that as incorrect information, because it is.

If it is incorrect, then I'll probably go with the Larsen NMO450CHW. I looked at a couple of spec sheets and I couldn't verify if it also uses the name 3/4" NMO mount that the NMO2/70B does. Basically I'm trying to figure out if I can use the Laird SBTB3400 3/4" bracket with the NMO450CHW as well?
The Larsen brand antennas with the prefix "NMO" all use the NMO mount. The nice thing about NMO mounts is that they are standard, and an NMO antenna from one manufacturer will fit on a mount from a different manufacturer.
But the NMO450CHW is a good antenna. It's half wave, so it will work without a ground plane under it.
 

mmckenna

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My Jeep is the older TJ (2004) model, so the flat bracket should work fine with my hood/fenders.
Not a bad idea to put a bit of sealant under the mount before you screw it down. Water can get trapped under there and lead to rust/corrosion. Using the star washer under the mount before you screw it down will help it get a good electrical connection to the body, or better yet, if you can access the underside, use a stainless steel screw and locknut.

And like I mentioned to the guy in the other thread,
I'm sure you've put a lot of effort into building out your Jeep. Setting up your radios/antennas should be part of it. Unfortunately companies like Midland and the CB manufacturers want consumers to think that installing a radio is a simple task. They'll supply "one size fits all" components, and that usually doesn't work out so well. Putting the extra effort into proper antennas and mountings will pay off in the long run. You'll get better performance and longer service life out of everything if you do it right the first time.

I've seen some pretty scary installs on not only this site, but on others. People are too quick to cut corners to get the install done. Using high quality antennas, mounts and components will really pay off in the long run.
 

ccg_ga

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@mmckenna

Excellent suggestions about the install - I will definitely do those steps to ground and seal the mounts properly.

I saw the link to the Larsen NMOKHFUD (https://www.theantennafarm.com/catalog/larsen-nmokhfud-1123) mount and coax so I am going to go with that one for both antennas.

I'm getting everything together to order the antennas and mounts, but not sure which of these PL-259 connectors I should use?


In regards to doing things right - I 100% agree with you. I have put a lot of time and money into building my Jeep and I'm not one to cut corners. I almost deleted this thread after I was reading about not mounting the antennas between the tailgate and spare tire. I'm glad I didn't because I would have never learned this much on my own. Here is a recent shot of the Jeep.

88009

I would like to do a write-up on the install after it's done to share this knowledge with other folks. I have done a couple on the site I maintain on other topics and I look forward to adding this install as well.

and https://southeast4x4trails.com/journal
 
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mmckenna

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RFI has been a good brand.
and Larsen has pretty good UHF connectors: https://www.theantennafarm.com/catalog/larsen-pl259-2887
Both will have the adapter you need to hold the RG-58 cable. If you shop around, you can find the NMOHF mounts and they'll include a "loose" UHF connector.

Only challenge is you need a good hot soldering iron. Soldering the center pin isn't too difficult, but doing the braid is hard. You want something like a 200 watt iron to get it hot quick enough to not destroy the cable. If you try to use too small and iron, you'll end up melting the cable. It usually takes some practice, so getting a few extra connectors and some of the excess cable to practice with is a good idea.

I won't go over the whole process, there's likely some good tutorials on line.
Other option is to bite the bullet and go to a local radio shop and have them install some crimp on connectors. Might cost a bit more, but if you don't have your own crimp tools or your own soldering iron, it might be a cheaper/easier way to do it. Take the guys a cold six-pack and they'll probably put the antennas on their antenna analyzer for you and make sure they are tuned properly.
 

ccg_ga

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RFI has been a good brand.
and Larsen has pretty good UHF connectors: https://www.theantennafarm.com/catalog/larsen-pl259-2887
Both will have the adapter you need to hold the RG-58 cable. If you shop around, you can find the NMOHF mounts and they'll include a "loose" UHF connector.

Only challenge is you need a good hot soldering iron. Soldering the center pin isn't too difficult, but doing the braid is hard. You want something like a 200 watt iron to get it hot quick enough to not destroy the cable. If you try to use too small and iron, you'll end up melting the cable. It usually takes some practice, so getting a few extra connectors and some of the excess cable to practice with is a good idea.

I won't go over the whole process, there's likely some good tutorials on line.
Other option is to bite the bullet and go to a local radio shop and have them install some crimp on connectors. Might cost a bit more, but if you don't have your own crimp tools or your own soldering iron, it might be a cheaper/easier way to do it. Take the guys a cold six-pack and they'll probably put the antennas on their antenna analyzer for you and make sure they are tuned properly.
I ordered those solder style Larsen connectors along with the antenna's, but after looking around last night for a 200 watt+ soldering gun and watching a couple of videos I figured it would probably less frustrating if I just use the crimp style PL-259 connectors. It looks like my local HRO has these RFI crimp connectors so I am going to see if I can pick a couple up along with a crimping tool and wire stripper.


I am guessing that the crimp style connectors will be sufficient for my setup?

Also, what type of sealant is best to use under the antenna mount?
 

mmckenna

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I ordered those solder style Larsen connectors along with the antenna's, but after looking around last night for a 200 watt+ soldering gun and watching a couple of videos I figured it would probably less frustrating if I just use the crimp style PL-259 connectors. It looks like my local HRO has these RFI crimp connectors so I am going to see if I can pick a couple up along with a crimping tool and wire stripper.
Pick up several extra connectors so you can practice. It takes a few tries to get comfortable with the proper strip length and which crimp die to use.


I am guessing that the crimp style connectors will be sufficient for my setup?
I've been doing commercial 2 way radio stuff for almost 30 years now, we use all crimp connectors. Never had a properly installed connector fail. I won't even take a guess at how many I've installed over the years.

Also, what type of sealant is best to use under the antenna mount?
RTV/Silicone under the hood bracket will work. Just make sure you find one that won't damage any paint. Household clear silicone has always worked for me, but I don't install those sorts of hood bracket mounts.
 

ccg_ga

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@mmckenna @ladn

Got it on the sealant. Easy enough.

I ordered all of the antennas, coax and mounts over the weekend and most of it should be here by Thursday. I am planning on doing all of the install work this weekend.

So that the antennas are sorted out, I have been looking into power distribution and reading some of the threads on the topic. The main thread that I have read so far is this one - wiring for car-battery, fuse block, etc.

Here is what I am thinking so far, but need some help with a couple more questions. Most of this is based on the thread above.

I would like to use a fuse block and will probably mount it under the front passenger seat. The radios that I will need to connect are the Midland MXT400, the Icom IC-2730A and possibly a hardwire power cable for my Uniden SDS100 (I haven't found one yet but maybe down the road).

1. 8 gauge positive wire from the positive battery terminal to the fuse block
a. I am going to look for marine-grade wire on genuinedealz.com

2. 40 amp fuse in-line on the positive battery wire
a. Mounted near the battery
b. https://www.amazon.com/Blue-Sea-Systems-MAXI-Block/dp/B000THTBZO/ref=sr_1_2?ie=UTF8&qid=1479713055&sr=8
2&keywords=Maxi+fuse+holder


3. 30 Amp Auto Relay
a. I would prefer to have one that is sealed/waterproof since it will be under the hood. Do I need to use one that specifically says it is sealed or are the typical name brand relays usually sealed (EX: Bosch or Dorman)?
b. believe the relay should be mounted after the 40 amp fuse but before the fuse block - also in the engine compartment?
c. https://www.amazon.com/Dorman-88069-Universal-Pin-Relay/dp/B00NF0ICSO/ref=sr_1_5
crid=24495P6MVC0QC&dchild=1&keywords=30+amp+automotive+relay&qid=1594730416&sprefix=30+amp+auto%2Caps%2C156&sr=8-5


4. Fuse Block
a. I liked this one from Blue Sea Systems because it has a cover and places to label the wiring
b. I looks like this one can handle up to 6 devices/circuits?
c. https://www.amazon.com/Blue-Sea-Systems-5025-Blade/dp/B000THQ0CQ/ref=sr_1_1 dchild=1&keywords=Blue+Sea+Systems&qid=1594729133&sr=8-1

5. DPDT Toggle Switch
a. I have been chatting with ladn about his setup that uses a DPDT switch. I like the idea of having 3 power modes - all radios OFF, radios on with ignition ON and all radios always ON
b. I am trying to find a DPDT switch that will fit in the OEM center bezel slot. The main one I have found so far is on Amazon, but it looks like it is probably from a Chinse company.
c. Is this switch sufficient for my needs?
d. Amazon.com: Bandc Marine Boat Car 7 Pins 2 Light Blue Led On-off-on Rocker Switch Dpdt Waterproof 12v 24v: Sports & Outdoors

These are the other questions I noted down while reading through the threads:

1. For the fuse block ground - should I run a local ground near the block to the Jeep body? Scrape off some paint and screw the ground in?
2. Also for the fuse block ground - do I need to also run a negative ground back to the battery negative terminal?
3. For the radios - the positive wire runs to the fuse block, but how should I wire the grounds for each radio? Ground them by running a wire from the radio chassis to unpainted metal or do they also need a negative battery ground. Both power cables for the MXT400 and the IC-2730A have fuses on both the positive and negative power leads.
4. Also on the radio grounds - I have both of them mounted to an overhead console that is metal in the Jeep. I'm thinking I could remove some of the finish on the console and attached the grounds to it - does that work properly?
5. Which fuse block fuses are correct for the radios? The MXT400 can push up to 40W and the IC-2730A can push up to 50W. 20 or 30 amp fuse for both?
6. I currently have 14 gauge Autocraft auto primary wire from Advance Auto running to the radios in the Jeep cab. Is this wire sufficient to use as well?
7. I'm not quite clear on how to wire up the DPDT switch - if you could point me towards any info on that it would be much appreciated.

I apologize in advance for all the questions, but I think this should round up the rest of the install details. All of this information has been incredibly helpful.
 

mmckenna

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1. 8 gauge positive wire from the positive battery terminal to the fuse block
a. I am going to look for marine-grade wire on genuinedealz.com
SAE J1127 or SAE J1128 is my preferred choice. That's easy to find on Amazon. You want high count of fine strand conductors. That makes for a flexible cable that is not only easier to route, but will stand up to flex and vibration.

Good choice, I used on of those on my 2011 F150. Word of advice: The terminal screws will clamp the fuse in place when you tighten them down. When you install all this, leave the fuse out and the screws loose, or you'll have a hard time getting it in.

3. 30 Amp Auto Relay
a. I would prefer to have one that is sealed/waterproof since it will be under the hood. Do I need to use one that specifically says it is sealed or are the typical name brand relays usually sealed (EX: Bosch or Dorman)?
b. believe the relay should be mounted after the 40 amp fuse but before the fuse block - also in the engine compartment?
c. https://www.amazon.com/Dorman-88069-Universal-Pin-Relay/dp/B00NF0ICSO/ref=sr_1_5
crid=24495P6MVC0QC&dchild=1&keywords=30+amp+automotive+relay&qid=1594730416&sprefix=30+amp+auto%2Caps%2C156&sr=8-5
If you are going to fuse your system for 40 amps, then you'll need a 40 amp rated relay.
You want it after the fuse, the fuse is there to protect the wiring and everything attached to it, so a short jumper from the battery to the fuse, then everything goes after the fuse.
30 amps would probably be just fine for what you are doing, but you'd need to replace the 40 amp Maxi-Fuse with a 30 amp fuse. If you changed your system to 30 amps, using something like a Lind shutdown timer instead of the fuse would give you more options. It wires into the ignition and will automatically turn on when you start the engine. When you shut the engine off, you can set a timer for how long the radios will remain on. It's easy to wire a manual trigger switch to it to allow you to turn on the radios without starting the vehicle.

4. Fuse Block
a. I liked this one from Blue Sea Systems because it has a cover and places to label the wiring
b. I looks like this one can handle up to 6 devices/circuits?
c. https://www.amazon.com/Blue-Sea-Systems-5025-Blade/dp/B000THQ0CQ/ref=sr_1_1 dchild=1&keywords=Blue+Sea+Systems&qid=1594729133&sr=8-1
Yes, that will work, the one you linked to has several options depending on how many circuits you want to add. BlueSea makes good stuff.

5. DPDT Toggle Switch
a. I have been chatting with ladn about his setup that uses a DPDT switch. I like the idea of having 3 power modes - all radios OFF, radios on with ignition ON and all radios always ON
b. I am trying to find a DPDT switch that will fit in the OEM center bezel slot. The main one I have found so far is on Amazon, but it looks like it is probably from a Chinse company.
c. Is this switch sufficient for my needs?
d. Amazon.com: Bandc Marine Boat Car 7 Pins 2 Light Blue Led On-off-on Rocker Switch Dpdt Waterproof 12v 24v: Sports & Outdoors
Yes. All that sort of stuff is going to be made in China, some of it is good, some is crap.
Only issue I'd see is there is a risk of leaving it on. Installing a lamp might be a good reminder, or just using the Lind timer I mentioned above. The Lind timers cost more, but make the system pretty much fool proof. I use them in my own personal vehicles, and I never have to touch the radio. It turns on with ignition and will shut itself off after about 30 minutes after shutting the truck down. If I want to turn the radios on without starting the engine, I just turn the key on for a second and it turns it on.


These are the other questions I noted down while reading through the threads:

1. For the fuse block ground - should I run a local ground near the block to the Jeep body? Scrape off some paint and screw the ground in?
2. Also for the fuse block ground - do I need to also run a negative ground back to the battery negative terminal?
3. For the radios - the positive wire runs to the fuse block, but how should I wire the grounds for each radio? Ground them by running a wire from the radio chassis to unpainted metal or do they also need a negative battery ground. Both power cables for the MXT400 and the IC-2730A have fuses on both the positive and negative power leads.
There are two trains of thought to this. Both are valid.
1. Run the negative to a local grounding point. That uses the vehicle body as the return. If the battery strap for the negative terminal is in good shape and properly sized, there's no issue with this. The added benefit is that you are grounding your radios close by and that can solve some RF noise issues. It also saves you some money on wire. The existing vehicle electrical system does this.
2. Run an 8 gauge wire from the fuse block ground all the way back to the battery and ground to the body where the battery negative lead is attached. This gives you a return path that doesn't rely on the body. What it doesn't solve is issues with an undersized negative strap connection from the battery. On newer vehicles (probably not your Jeep) they have a hall effect sensor on the cable running from the negative terminal of the battery to ground. This is used to monitor current consumption of the vehicle and control things like alternator, auto shut off, etc. Bypassing that by running your ground all the way back to the negative terminal can create some issues. Usually the manufacturer will call this out in the manual.

I've never had an issue with grounding to the body. Those that claim it can create problems with corroded negative straps from the battery to ground are often people that do not maintain their vehicles and wait for things to completely fail before addressing them. I've never had that issue.

You —do— want a short ground for the radios to the body. This can prevent some RF interference issues. Relying on l-o-n-g paths to ground for radios, either through the antenna mount or the power feed is not a good idea. Long wires become good antennas and can either pick up noise or radiate noise. No matter which of the two options you choose above, run a short as possible ground strap from the radios metal chassis to a body ground point. I've solved some nagging issues with this. DC power ground and RF grounds are two different things.

Your fuse block has a negative buss, so you can use that for your power ground. Running the negative power lead for the radios to that is a good option. Just make sure you don't ignore properly grounding the radio chassis with a short ground strap.

Grounding the fuse block ground buss can use one of the two options above, either using an 8 gauge wire to the body, or run it back to the point where the battery grounds to the chassis/body.


4. Also on the radio grounds - I have both of them mounted to an overhead console that is metal in the Jeep. I'm thinking I could remove some of the finish on the console and attached the grounds to it - does that work properly?
See above. You need to consider your DC power ground and your RF ground. They can be the same thing if you do them right, or you can make them separate. Here's what I'd probably do:
1. Ground each radio to the metal box using a short strap from the radio mounting screw to the box. That'll work as a good RF ground.
2. Ground the radio box with a short strap to the vehicle. Sounds like that's going to be the windshield frame or roll bar. Make sure that the windshield frame or roll bar has a good connection to the vehicle body. Paint can get in the way….
3. Run the positive and negative power leads for each radio back to the fuse block.

Might be easier to just install your fuse block in the radio box, if it'll fit.

5. Which fuse block fuses are correct for the radios? The MXT400 can push up to 40W and the IC-2730A can push up to 50W. 20 or 30 amp fuse for both?
Check to see what the manufacturer recommends. Likely they have a fuse installed on the power leads. You don't need both fuses, you can use the one in the fuse block and run the power straight to the radio. I think you'll find that the radios will either have 15 amp or 20 amp fuses. 15 amps should be sufficient for a 50 watt radio.

6. I currently have 14 gauge Autocraft auto primary wire from Advance Auto running to the radios in the Jeep cab. Is this wire sufficient to use as well?
Looks sufficient. The 'right size' depends on how long the cable run is. As the wire gets longer, the resistance increases and that will cause voltage drop. Keeping your power leads short is a good idea. Running the fuse block in the radio box is a good idea to reduce the length of smaller power cable runs. Rely on the 8 gauge wire from the battery to do the hard work. Keep the power leads that run from the fuse block to the radio short.

7. I'm not quite clear on how to wire up the DPDT switch - if you could point me towards any info on that it would be much appreciated.
You'll need a single pole double throw switch with a center off position. Double pole will be fine, but you won't use half of it. Might be easier to find the DPDT switch, though.

The center connection (Common) will be the connection to the relay coil. The other two connections will be used for:
1. full time power, that'll need to come off the battery or full time power source. Fuse it for 5 amps or so, just enough to run the relay coil.
2. ignition controlled power. That'll need to come from an ignition switched source, and also needs to be fused.

Or, just use the Lind Timer like I mentioned above. You'll still need a fused ignition controlled power feed, but it'll take care of the on/off for you. Cost more, but it's pretty much fool proof.


I apologize in advance for all the questions, but I think this should round up the rest of the install details. All of this information has been incredibly helpful.
No apology necessary, those were good questions.
 
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