running CB and UHF radios in truck. protection?

[WRFV510]

I was told that my  CB would burn up my Motorola 5550e's front end if i didnt protect it. What would I need to protect it?  disconnecting the coax is not a option. 

[Lscott]

I was told that my 150w CB would burn up my Motorola 5550e's front end if i didnt protect it. What would I need to protect it?  disconnecting the coax is not a option. 

Run 4 watts.

[tweiss3]

If you space the antennas 18-24 inches apart, and run legal power, you shouldn't have an issue. I have both CB and UHF/GMRS in my car.

[marcspaz]

I was told that my 150w CB would burn up my Motorola 5550e's front end if i didnt protect it. What would I need to protect it?  disconnecting the coax is not a option. 

 

 

Whoever told you that has no idea what they are talking about.  I have had 3 different radios running in my Jeep at the same time, with varying power from 4 to 500 watts, and with zero issues.  If you have moderate quality equipment or better, unless the antennas are a foot apart (for example) you should have no problems.  And if you do, just leave one off while you use the other.  No need for anything else.

 

I know the FCC really isn't enforcing power limits on CB radio anymore, but I wouldn't get on the internet and admitting in writing that you are violating rules.

 

 

Run 4 watts.

I literally LOL'ed. 

[WRFV510]

they will be 25" apart. and ya might as well run 4 watts.  never got anyone to come back to me over 6 miles away anyway. 

[marcspaz]

they will be 25" apart. and ya might as well run 4 watts. never got anyone to come back to me over 6 miles away anyway.

I am bidding on a job right now. The customer is asking for a radio network to cover a huge campus with a 10 mile radius from the main site. They specifically asked for CB radio for several base stations and more than a dozen mobile units.

 

We did a radio path evaluation and a live site survey to show them why CB was a bad choice for their area. We covered the entire campus with 2 watts on commercial UHF mobile radios, with no less than 5/5 signal reports. We also covered the main facility of 1,000+ acres with 1 watt on UHF handheld radios, with no less than a 59 signal report.

 

All the same tests with CB radio, we had signals as low as 3/2 across the main facility and 100% signal loss after 1.5 miles from that location.

 

CB can be fantastic in some cases, where UHF failed. This is mostly noticed in areas with low parasitic noise levels, such as out in the country and rural areas. On more than a few occasions, I lost my UHF connection to someone after 2.5 miles, but could reach them for 25+ miles on the CB.

 

Because there is no such thing as a perfect, Jack of all radios, I end up with 3 radios in my truck... Ham, GMRS and CB.

[WRFV510]

i need the CB for communicating on the highway. GMRS will be for family. out on the atvs or any place.  i can see my local repeater from my house. elevation almost 1700ft with the repeater being on a 150' tower. my dad is 20 miles away as the crow flies and is at 1700' too. he can hit the same repeater with a 5w BF-888 5X5.  its sweet . One bad thing is were we live is very hilly. so the signal goes in and out. so im getting a Motorola XPR 5550e option board enabled with the CPS and wide band EID. Im going to check out a Laird BB4503S 3db gain and a Laird BB4505CR 5db gain and see what one works best. both roof mounts with RG8X. Im doing the mobile in the truck

[berkinet]

...I end up with 3 radios in my truck... Ham, GMRS and CB.

You didn’t think someone would call you on that? ;-) That is like comparing a seven course meal in a three star restaurant to a packaged burrito and a tuna sandwich. There is nothing wrong with the burrito or the tuna sandwich but they are not full course meals with lots of options. BTW, don’t get me wrong, I like all 3... for everything there is a time and a season.

[marcspaz]

You didn’t think someone would call you on that? ;-) That is like comparing a seven course meal in a three star restaurant to a packaged burrito and a tuna sandwich. There is nothing wrong with the burrito or the tuna sandwich but they are not full course meals with lots of options. BTW, don’t get me wrong, I like all 3... for everything there is a time and a season.

 

 

I don't mind being called out.  I grew up on tuna.  Couldn't afford that and the burrito.  LOL 

 

That said, people don't have to have $5k in electronics in their vehicle.  Affordable tech, installed correctly, can perform just as well.  If someone can only afford or fit one, they should get what they like the most and will use the most, and just accept the short-comings and the fact that nothing is perfect.

 

 

EDIT:  I forgot to mention earlier.  If you are going to run a CB... use Single Side Band.  AM and FM are restricted to 4 watts.  SSB is limited to 12.5 watts, is way more efficient and the signal travels way further.  Much better mode.

[berkinet]

You are right about the cost/expense. My point is you can’t really compare amateur radio to gmrs or cb. The latter two services are restricted to a single band with limited modes of operation. On the other hand, US amateur radio has 22 bands and numerous operating modes (really unlimited for those who want to experiment).

 

However, that does not make amateur radio better, just a very different type of radio service.

[WRFV510]

i run the cb to see whats up the road so AM 19.  it is a 980 so i do have SSB and the clarifies open.  

[WRFV510]

Whoever told you that has no idea what they are talking about.  I have had 3 different radios running in my Jeep at the same time, with varying power from 4 to 500 watts, and with zero issues.  If you have moderate quality equipment or better, unless the antennas are a foot apart (for example) you should have no problems.  And if you do, just leave one off while you use the other.  No need for anything else.

 

I know the FCC really isn't enforcing power limits on CB radio anymore, but I wouldn't get on the internet and admitting in writing that you are violating rules.

 

 

I literally LOL'ed. 

would i loose anything by running a MJF-1702C switch off my Motorola XPR5550e? I can run one side of the switch to the antenna and the other to home made dummy load.   i can just switch to the dummy load when i want to use the cb. or should i even bother?  id have to put a mini UHF to SO259 adapter o the motorola with a RG8x 1' jumper to the switch then a pl259 to a female mini uhf adapter to antenna. i already had a mini uhf male connector put on my Laird RG8x NMO roof mount.  Sound like its not worth it if i will loose strength.  Antenna will be 25" away from each other.  Id say a Motorola XPR5550e was quality equipment. 

[marcspaz]

The MFJ-1702C could be more of a problem than anything. It has a center-off position that sends the connections to ground, for lightning protection. Forget to turn that switch all the way to one side or another just once and your radio is toast.

[berkinet]

Honestly, I think the answer to the original question has been given in the posts above.  Keep the CB to 4W, and keep the antennas as far apart as possible, but not some multiple of a 1/4 wave length on the GMRS band*.  Trying to optimize the situation by antenna switching, adding dummy loads, or anything else is only going to add complexity and increase the chances of failure, without adding any benefit.

 

* 1/4 wave is roughly 6.30 (467.725 mHz) to 6.37" (462.725 mHz) for the GMRS band. So, use some number midway, like 6.335" and give your self 1/2" distance around that: 5.85 " to  6.85" So, avoid distances  like 23.4 - 24.4, 29.25 - 30.25, etc

[WRFV510]

ok thanks. i had no idea the middle would damage the radio.  this sucks though.  i paid alot of money to have that cb radio built. i can switch off the amp but the radio was turned down to 2.5w to work with it.  What about the 12w SSB.  i would have to get the cb turned up. can i go any farther. these radios will safely go to 22w

[marcspaz]

ok thanks. i had no idea the middle would damage the radio. this sucks though. i paid alot of money to have that cb radio built. i can switch off the amp but the radio was turned down to 2.5w to work with it. What about the 12w SSB. i would have to get the cb turned up. can i go any farther. these radios will safely go to 22w

Are you running a modded galaxy? Those are fantastic and have a lot of potential. If so, the AM and SSB power are adjusted separately, so the SSB side should still be at 12.5w.

 

The DX 44 HP goes to 40w bone stock and some models go to 100w. The export guys have it made with their CBs. The FCC should just let US operators use amps, since there are no emergency services down there anymore.

[WRFV510]

Uniden 980 by Snake Radio Customs. 

[marcspaz]

Hmm nice performing radio, but I'm not sure if the AM and SSB power are separate. I would gi e the shop a call and ask if SSB is still at the factory settings... assuming you don't feel like spending money on a meter for a one-time use.

[WRFV510]

i have a MJF-874 https://mfjenterprises.com/products/mfj-874. i dont know were the pots are on the new 980 (2019)  radios. i beleave they are not separate by watching videos. 

[WRFV510]

i drilled another hole today 

[Jones]

Hmm nice performing radio, but I'm not sure if the AM and SSB power are separate. I would gi e the shop a call and ask if SSB is still at the factory settings... assuming you don't feel like spending money on a meter for a one-time use.

It's a "Snake Radio Custom". In my opinion, a clueless "screwdriver expert".  Keep in mind Marc, the SSB power control in these radios is useless and no longer functional when the ALC transistor has been clipped out for "Maximum Swing" or whatever.  ..and Jesse, If it were a clean 100, or even 500 Watts at 27 MHz, it would in no way harm the Motorola UHF front-end, however this thing with its un-filtered chinese-made amp slab is very likely going to be grossly dirty on the spectrum, so no promises.  The only thing I can promise you is that no oscilloscopes, or spectrum analyzers, or professional technicians were used in the tuning of this "Super" radio.

 

Quote from "the snake" himself from forums.radioreference.com:

 

"I am old school and I tune and align the radios buy ear and my pep meter and my bird wattmeter and my signal generator and DB meter for receiver peak settings . I have had people take radio`s that I have done to other shops with all the spectrum analyzers and scopes netc etc put my radio on there equiptment and it was right on the money."

 

Sure, I'll bet.  I ran a CB shop in Salina Kansas back in the 80s and early 90s, and I have seen and repaired thousands of these butcher-shop customs.  These days it is even worse with the influx of cheap Chinese and Italian MOSFET amp modules.

 

If you are really worried about your UHF being overloaded, use one of these filters between the output of your CB amp, and your CB antenna:

https://www.dxengineering.com/parts/mfj-704

That will filter out anything above 40 MHz to protect your other VHF and UHF radios, and prevent interfering with other services.  It's a pricey accessory, but it might be worth if for you, and it will certainly handle all of the power you will be able to throw at it.  Be sure to use a high-grade RG-214 coax jumper between the amp output and this filter.

 

OK, now that I have upset everyone, I'll sign off for the day.

[marcspaz]

There is a guy I know that puts "swing kits" in radios and you are right.. the SSB never works when he is done. But... I thought OP said it was turned down to 2.5 wattsto drive the amp. I have to re-read it.

 

I'll tell you this, anyone running a de-tuned radio to accommodate their amp, likely has a home made amp done by guys who think/claim they are experts, but have no idea how to build a filter or ALC circuit. You open the box and there are heat syncs, a few Toshiba PAs and the few parts needed to make the PAs work... and that's it.

 

 

OK, now that I have upset everyone, I'll sign off for the day.

 

 

Best part of the post. I LoL.

[WRFV510]

ya now that im learning im thinking your right.  

[n4gix]

Well, he did have an oscilloscope showing his audio while he screamed "AAAAAAAUDIOOOOOOOOOO" into the microphone!

[WRFV510]

its got the guts of a RM Italy KL203 installed inside the radio. 

[WRFV510]

i will say everyone who came back to me said the thing sounds great. never got anyone more then 6 miles though.  but unless they have a base or power you're not getting out in these hills.