powerband rfx 75

[johnecashflo]

rfx 75 in cobra 29 capacitor voltage

can anyony tell me how important the c42 voltage is on the cobra rfx 75 mod..i intsalled all the parts as stated on cb tricks (a wonderful site..thanks for all the help)..the rfx 75 seems to be working fine..deadkey 10 swings over 130 on my cheap meter..the install call for a 3300 uf 16 volt capacitor in the place of a 1000 uf 16 volt..the problem is radio shack only has 3300 6.3 volts ..should i leave the original cap or replace it with the 3300 6.3 volt cap..what can happen if i dont get the right cap values..thanks for any help

 

[Cityboy]

I did this mod and am somewhat impressed. I installed just a few minutes ago and got a dk= 5 1/2 and swings to 55-58w. With modulation set at 18-20% and swings 100%. I have not installed the 1000uf at j36 and 33ohm resistor on the other side. I am running at 13.8v and it pulling around 5-7 amps and it is getting very hot if you stand on it at all. I will install cap at j36 and resistor and get back to you. I think the 130w is way too much for a mosfet rated at 75w.

 

[johnecashflo]

did you change the cap at c 42? that is one of the things i am wondering about..i did ad the cap and resistor at j 36 ..im wondering about the voltage at c 42.. the only cap i could find at radioshack was a3300 uf 6.3 volts..calls for 3300 uf 16 volts ..the ? was will it blow the lower voltage cap...as far as the 130 watts i have a cheap meter its probably more like 100 watts im guessing

 

[bob smith]

Just get a RM KL203 amp and velcro the thing to your radio. 100-130 watts and much more reliable plus you can use it with other radios. Plus, you get a REAL deadkey of 20-30, not this 5-8 bullsnot.

 

[74IN]

Whatta cheap meter.....


YouTube - RFX-75 Install in a Cobra 29 Black Chrome

 

[johnecashflo]

the question is not about my cheap meter it is about the values at c42 you got na answer for that thanks

 

[Cityboy]

I replaced the capacitor at c42 with the suggested one by cbtricks,but did not do the j36 removal and the results are as follows. dk = 12-14w, pep = 75-80w, and just for kicks I took a RMS reading even though it doesn't mean much it was doing around 38-42 RMS. Now that is quite a bit of RMS and leads me to believe my meters being passive are not getting the full peak number and maybe much higher than my 75-80w reading. It does get pretty warm and the dk goes down when you stand on it.

 

[bob smith]

Whatta cheap meter.....

Cheap meter and/or excessive modulation.

My vote goes to excessive modulation. 7 watts swinging 130.... Yeah, ok.... riiiiiiiiiiiiiiight. I bet that sounds super-truckerish.

(Let the leg humpers emerge and tar and feather me...)

 

[theshortcircuit]

can anyony tell me how important the c42 voltage is on the cobra rfx 75 mod..i intsalled all the parts as stated on cb tricks (a wonderful site..thanks for all the help)..the rfx 75 seems to be working fine..deadkey 10 swings over 130 on my cheap meter..the install call for a 3300 uf 16 volt capacitor in the place of a 1000 uf 16 volt..the problem is radio shack only has 3300 6.3 volts ..should i leave the original cap or replace it with the 3300 6.3 volt cap..what can happen if i dont get the right cap values..thanks for any help

My understanding from talking to Sparky is you will not gain full potential from this radio without replacing C42. In this converstation, he stressed using a 3300uF with proper voltage rating. While this isn't first hand experience, I would take that to mean a 6.3v will not work satisifactory.

I have an xtra 3300uF 25v (only because I couldn't find 16V, when I ordered them) If you are close to zip 46526, PM with contact number and we'll see if you are close enough to come and get it. It's too big to just put in an envelope and mail.

With regard to another's post questioning 7W DK and 130W swing. You're right, you can believe that radio was overmodulating and ready to be sold to someone ready to talk; with nothing to say.

 

[Switch Kit]

Believe I heard they were selling for 40 dollars a piece with NO warrenty. OK . Local tech is getting 100.00 total for install and unit.

Sounds fair enough for a 100 watts out cb radio . Pump up them power wires ! What will they think of next ? IM impressed.

(edit by Moleculo for Content)

 

[Cityboy]

I think some of the posting of the wattage is far out line in the fact either the voltage has been ramped up or the like bob_smith said overmodulation. I did nothing to turn up the modulation on this brand new cobra chrome special edition to achieve the numbers I gave out. I ran it honestly at 13.8 volts and the VR4 was factory set. It sounds pretty good on my headphones and may be a little too strong. It may well be a trucker special but I figured I would try it out for myself and in the next week or so I will give you real world reports on how it did on the road; trucker special or not. If it doesn't perform audio wise I will post it and I have several friends who have good ears and will give me their honest and truthful opinions on how the audio sounds at a distance and up close. Important: I used a 3300uf 16v as recommende at c42 and pretty much followed the instruction to the letter and did not remove j36 as I thought it would cause it to overmodulate using what I saw was a "super modulation" kit to lower the dk and raise the modulation up even further.

 

[74IN]

I'll listen to those that have tried one.

The rest are just guessing.

When I install mine (when I get the time), I'll give an opinion.

 

[Moleculo]

I have a couple of brand new 29's sitting in the box over here. I'd like to try one of these RFX-75's on one to see what happens. My distributor doesn't get anymore in until the end of this month, though. $100 for the unit + installation labor seems pretty reasonable. However, that does put a Cobra 29 at a $200 radio. I guess that's about right if you're were going to just buy a $100 linear to go with it.

Any takers for the new radio with the RFX installed after I do this? I don't really have much use for another CB, except maybe just to try this out.

 

[johnecashflo]

if you talking about the rfx costing 100.00 thats way to high..i might see a 100.00 total for the part and the install.. rfx 75 costs 44.00 on ebay shipped

 

[Moleculo]

No, SwitchKit was saying that his local shop charged $100 for the device including installation. That sounds reasonable to me.