Benefit 200W amp for mobile 2M Simplex?

[amoking]

Hello All.

I was chatting with mmckenna about this a couple days ago and thought I would take it to the masses:

I have a Kenwood TM-V71A in my truck. NMO mounted Laird 5/8 antenna with an SWR of 1.1 on 146mhz. Install is as tight as a drum.

As it pertains to 2M SIMPLEX will I get any noticeable benefit out of a 200W linear amp (RM Italy LA-250V perhaps) as opposed to the 50W from my Kenwood? I know that ones signal is only as good as what you can recieve. For context, we use this truck in environments where cell signals and repeaters are relatively non-existent.

I'm not worried about the cost as much as I am the efficacy. Yes, we do have sat phones as well but what's the fun of that.

 

[WPXS472]

As someone who operated a 150 watt 2 meter linear in my car some years ago, I feel somewhat qualified to comment. I would replace the RG58 coax with something larger. You are getting close to the maximum amount of power it can handle. You probably won't burn it out, but the lower loss of the larger cable, even if only a few feet, will make a difference in the power delivered to your antenna. If you operate it in FM mode, it will get HOT! I remember burning my fingers touching my amp after only a couple of minutes of operation. You will get more range, but how much good will it do you if those on the other end don't run the same amount of power? Increasing transmit power isn't as effective as you might think. Doubling your power won't double your range. A more effective solution would be to operate sideband. It might not be practical in your situation, however. An amp this big will draw considerable amounts of power from your truck's battery. Just be aware. My final word is that it probably isn't worth the cost and hassle.

 

[prcguy]

50w to 200w is a 6dB increase in power which is a very noticeable improvement. Its also one "S" unit improvement. Everyone will hear you better, especially at a distance. You probably will get into situations where the contacts are not reciprocal and people will hear you but you will not hear them. You might even interfere with conversations you can't hear but they will hear you.

 

[amoking]

That's my gut as well. Power supply is no issue as I have a Ford diesel with 2 upgraded alternators. Are you saying RG58 is maxing out at 50 or 200W? Me initiating a broader simplex call is the main goal...emergency or downed vehicle in baja....not just an idle CQ.

 

[kb5udf]

Have you considered a 100 watt mobile? They can sometimes be had for a low cost (e.g. I've bought a motorola MCS2000 100watt VHF for about $120). Very effective, and a bit simpler of a setup then having a separate linear amplifier, albeit with the added complexity of a remote head/body, but in a big pickup, you should have the room.

 

[amoking]

Have you considered a 100 watt mobile? They can sometimes be had for a low cost (e.g. I've bought a motorola MCS2000 100watt VHF for about $120). Very effective, and a bit simpler of a setup then having a separate linear amplifier, albeit with the added complexity of a remote head/body, but in a big pickup, you should have the room.

I have but I really love my Kenwood.

 

[mmckenna]

I have but I really love my Kenwood.

TK-790H
TK-5710H
NX-5700H

 

[amoking]

TK-790H
TK-5710H
NX-5700H

Which of the 3??

 

[62Truck]

Which of the 3??

Any of those 3 area available in 110 watts.

790H is analog only
5710H analog and P25
5700H can either do analog and DMR or analog and P25

You can also pair a 790H with an 890H and run both radios off of 1 head, same with the 5700H and 5800H.

 

[amoking]

Any of those 3 area available in 110 watts.

790H is analog only
5710H analog and P25
5700H can either do analog and DMR or analog and P25

You can also pair a 790H with an 890H and run both radios off of 1 head, same with the 5700H and 5800H.

I have some homework to do. Are these new or only used now?

 

[mmckenna]

I have some homework to do. Are these new or only used now?

TK-790 has been around since the late 1990's. Been discontinued for 6-7 years now. Analog only. Durable radios. CHP used the TK-690 low band version for a very long time. There's a few on E-bay, easy to find fairly cheap. Won't do MDC1200 without adding an aftermarket board.

TK-5710 has been around since the mid-2000's. Discontinued in the last year or two. P25 and Analog. I've got about 10 of them in police cars and they've been rock solid, no issues in 10+ years. Going to cost more because they are newer and have P25. I'm trying to get my hands on one when we replace them at work. Will do MDC1200 if you are into that sort of kinky stuff.

NX-5700 has been out for 5 years or so, can be bought brand new ( @kd4efm can probably hook you up ). Analog, P25, NXDN, DMR. Expensive, but you can do a hell of a lot with them. Stack them up to 3 deep with one or two control heads. You can get a low band version, VHF, UHF and 7-800MHz. Second mortgage on your home required for entry. Programming software sucks butt and will cause you to learn new cuss words. Go for the EFJ Version with Armada software. It doesn't suck.

 

[k7ng]

Didn't cause me to learn new cuss words. Just new ways to put the ones I know together, and the frequency of use.

 

[DeoVindice]

Go for the EFJ Version with Armada software. It doesn't suck.

This bears repeating. Armada is the best in the business. Much of the multiband/multideck EFWood stuff also supports crossband repeat, in case you want to carry a UHF portable when dismounted.

 

[Lauri-CoyoteFrostbite]

.

This may be trivial, but have you considered the radiation effects of 200 watts in close proximity to your head etc. ?
How well are you being shielded from the antenna by the truck cab, what is the duty cycle (ie: lengths of transmission time and such) you will be exposing yourself to ?

Personally I have done some rather alarming measurements of field densities in vehicles --and today I keep the V/UHF power in mine to levels below 35 watts. This maybe a little old maid-ish but when you've worked around high pwer'd stuff for a whole career you get that way.

If I can't do it with ~35 watts its not worth it.

(.....but on the plus side, at 200 watts you should be able to warm a cup of coffee on your dash-------------just kidding, just kidding ! )

Lauri


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[k7ng]

What she said!
Read with heed!

 

[Lauri-CoyoteFrostbite]

.

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WPXS --- "......I would replace the RG58 coax with something larger. You are getting close to the maximum amount of power it can handle. You probably won't burn it out, but the lower loss of the larger cable, even if only a few feet, will make a difference in the power delivered to your antenna...."


Well........... there is no gainsaying that switching to a lower loss coax cable from RG58 will deliver more power to your antenna-- but at what cost?
By cost, for one, I mean the awkward coax's physical size -- that of a large cable diameter v.s the smaller '58.
Is it worth it to snake a new thicker cable up the vehicle side walls and under it's headliner ?

Assuming- maybe at most- a 10 foot feed line - RG58 is only going to be a 0.5- 0.6 db loss. RG8 coax is about half that. No one is ever going to hear the difference signal-strength wise. But they will probably hear the cussing as you wrestle that thick black snake up under your headliner and try to attach it to the base of an NMO connector . *

You can reduce the loses more by going the ultimate with a section of 2 inch Andrews Heliax. Now it will reduce that loss down to 0.02 db's -- ...... still no one will hear an improvement over that poor anemic RG58....

.... Oh, but Wow ! now you will have one awesome mobile installation that will elicited all sorts of comments -- those you will hear !



Lauri


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* at 2 metres a short run of RG58 with a SWR of <1.5-to-1 can handle 200 no sweat, btw

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[mmckenna]

I somehow ended up with an NMO mount that had LMR-200 on it. LMR-200 is slightly larger than RG-58, but w-a-y more stiff. I installed it at the time because it's what I had and I needed to wrap up the install.

As Lauri said, it was a real pain getting that stiff cable routed correctly. There's normally a small amount of my blood spilled during any good install, but that time I think I outdid myself.

 

[k7ng]

The difference between LMR-200 and LMR-240 is surprising. I use LMR-200 on occasion for mobile installs, when I don't have to deal with twisty cable runs, but the LMR-240 is another story. I used LMR cables for additional shielding but now I've found the NMOKHFUD connector w/ foil shield RG58 so now I use that. I like the extra shielding.

Yeah, let's have some fun, try to do a mobile install using LMR-400. The blood shed would probably after I shoot myself for trying such a thing in the first place.

 

[prcguy]

In the mid 70s I had a couple of guys request I install their car ball mounts with RG-8 coax, which is the same size as LMR400. I did and it was not fun but their are ways to get it done. Why did they want RG-8 in a mobile? I suspect it was for the eventual amplifier that was going in. These were in a couple of new Cadillac's. Nuff said.

The difference between LMR-200 and LMR-240 is surprising. I use LMR-200 on occasion for mobile installs, when I don't have to deal with twisty cable runs, but the LMR-240 is another story. I used LMR cables for additional shielding but now I've found the NMOKHFUD connector w/ foil shield RG58 so now I use that. I like the extra shielding.

Yeah, let's have some fun, try to do a mobile install using LMR-400. The blood shed would probably after I shoot myself for trying such a thing in the first place.

 

[R8000]

This may be trivial, but have you considered the radiation effects of 200 watts in close proximity to your head etc. ?

Personally I have done some rather alarming measurements of field densities in vehicles --and today I keep the V/UHF power in mine to levels below 35 watts. T

Yup. I was going to comment the same thing but didn't because it seems in today's world nobody cares. It usually falls on deaf ears.
Sometimes you just have to let folks find these lessons in life the hard way

I don't even use fender mounts unless there's no roof option. I just don't like 50 watts staring into my eyes at three feet away with a 2db gain antenna.