Help with amp

[Triple R]

I have a Cobra 29 LX tune and aligned by Sparky CB Shop, a Wilson 5000 magnetic antenna with a 39" short load stinger mounted in the middle of my roof on a Ford Ranger. I am trying to connect a RM KL 203P amp with a 3' jumper between the amp and the radio. My problem is with the radio alone my SWR is about 1.2 but when I hook up the amp the SWR goes off the chart on the high end before I even turn the unit on. Power to the Amp is run with 14AWG wire from the battery and 10 AWG ground to the seat bracket. I need help from those who know as to what I'm possibly what I'm doing wrong.

 

[ExitThirteen]

It sounds like your jumper might be bad. You can check the jumper to see if it is shorted or opened. If it checks ok then there might be something funny going on with the amp. Try another jumper if you have one first tho. Hope this helps!


~Cheers~

 

[Triple R]

Thanks I'll try that. I will check it and get me a new cable as soo as I get back to town. Will let you kow how it works out.

 

[ExitThirteen]

Sounds good, let us know how you get on.



~Cheers~

 

[Triple R]

I tried a new cable with the same results. I'm going to just use my CB barefoot for now and will work on the linear hook up later. Got too much going on right now to spend my few days off messing with the set up right now. Thanks for your help though I really appreciate you taking the time to answer my post and try and help me. Thanks

 

[psycho]

I have a Cobra 29 LX tune and aligned by Sparky CB Shop, a Wilson 5000 magnetic antenna with a 39" short load stinger mounted in the middle of my roof on a Ford Ranger. I am trying to connect a RM KL 203P amp with a 3' jumper between the amp and the radio. My problem is with the radio alone my SWR is about 1.2 but when I hook up the amp the SWR goes off the chart on the high end before I even turn the unit on. Power to the Amp is run with 14AWG wire from the battery and 10 AWG ground to the seat bracket. I need help from those who know as to what I'm possibly what I'm doing wrong.

Sounds like you have a problem with your amp. Your amp should never change the antenna match just by being put in line and not turned on.
Why do you need the 39" short load because you lose quite a bit of performance over the 62" non loaded whip.
You made no mention of where you are checking the swrs.....that might be useful info.

 

[Triple R]

I'm using a short load because of clearence with trees that suround my housing area that I keep hitting when I leave and enter the area. I think I my be checking the SWR wrong. I have been checking with everything line (after the radio), but after doing some reading I think that I should be checking it after the amp and when that is tuned then hook up the radio. Is this right?

 

[Triple R]

I'm using the SWR on the radio but I think that I need to use my meter between the amp and the radio?

 

[fodendaf]

Try it with the meter between the radio and amp and the meter between the amp and the antenna if u have a second external meter even better. Radio swr meters are invariably miscalibrated and should never be trusted. If there is a high swr between radio and amp then that could blow the finals in the radio. If there is a high swr between amp and antenna then that could blow the finals in the amp. They are different issues and that is why swr must be tested both ways

 

[Triple R]

Thanks I will check that out

 

[jazzsinger]

sounds like a duff jumper,


but other possible causes:

i notice you say the radio is aligned and tuned (not too sure what that involves), it is very possible that its overdriving the amp. in my experience of rm and all other italian amps the input figures are highly overrated, if the amp being overdriven is causing harmonics from the amp it could be seen as a high vswr.

another thing i've noticed with small italian amps when used with magmounts is they are highly susceptible to rf, could be some common mode current on the shield, due to a poor ground connection. magmounts ain't the best (some better than others) when it comes to having a good ground connection.

 

[9C1Driver]

To start you need to get an external SWR meter, once you add an amplifier the meter in the radio is no longer a concern. The SWR reading is taken AFTER the last transmitter in-line, in this case that would be the amplifier. So get your SWR meter after the amplifier.

Remember the antenna is tuned to the vehicle and not a radio or amplifier. Once set your done. Any problems after this are a rslust of a mismatch of the amplifier or radio. You should be ok.

Last, what kind of numbers are you seeing from the radio? Remember the smaller RM amplifiers are very much low drive amps. A dead key of say 1.5 watts and peak swing of 12-18 watts are all thats needed. Any more then that and you will OVERDRIVE the amplifier.

I know Sparky rocks with his tune. You might want to consider a KL300p as the smallest amplifier you can run with your radio. The smaller RM amplifier work best with the low powered micro radio's.

 

[Retro radio 13]

That was a good read as i am suffering kind of the same problem with SWR on a home base set up with a kl300p swr fine no amp turn am on and pffttt the swr goes up tried different patch cables checked for shorts un soldered and re soldered all coax connections no difference even retuning the antenna from start mad a small difference .

home set up is a Tedelex 40 ch ssb A station master mk11 antenna kl300p amp rg213 coax as main feed and jumper.
just about ready to blow a fuse myself, but must try the set up on a diferent radio and see what happens.

but great info on here . cheers