very reasonable ..local hacks are charging up to 150.00 around the circle city..the only reason i call them hacks is they love to stick it to the drivers who have no where else to go..and a tune up is just cutting the guts out of a radio..
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powerband rfx 75
- Thread starter my2995dx
- Start date
The You-Tube video is from CBR (custom cb radio). Doug there used to work at Sparkys and seems like a very sharp guy. He is also quite honest and runs a good shop. As far as the meter he uses, look them up, very expensive. I would say off hand they tend to read high but it's by no means a cheap meter.
well ive run the radio in my truck for 3 days and it really gets out.. like i said before not sure of the power that radio with the rfx 75 is putting out but the audio is crystal clear..ive run it with an astatic 636 and a road king 56..reports where good with both mics..i prefer a roadking but both mics worked great with this setup..here is a on air example..southside of indy exit 4 ..3 truckstops 2 cb shops all the clutter in that confined area and i or should i say the radio was heard 10 miles away by one of my friends who hit me on my nextel to tell me he could hear me on the eastside of indy (apx 10 miles) thru the clutter. i was impressed .. thanks to the forum for letting us have a place to talk or vent whichever it may be ..
The RFX 75 does a very nice job in the cobra 29 ltd..clear audio and plenty of power..i put one to the test the other day with alot of talking ..it never even got hot..once again
I ran my RFX-75 last night in my truck and ran across a problem that I didn't think would happen. At home on my astron vs-35 I had no problems of producing 13-15w dk and peak of 72-80w pep. But when I got to work it was not even coming close. It acted like it was starved for amps; but I run my General Lee through the same heavy duty power cord to the cigarette lighter with no problems. It only keyed around 1-2 on s/rf scale and keyed to about 5 pep on the scale. Where at home it keys at 9 and spanks the meter back and forth. Any suggestions as to why it seems to be starved for power at a real life test and not at the house. This was with the tractor off and it did this. I will try a different power cord tonight and also the swr are low on this tractor. I retested at home and it pumped out 80w pep. Any suggestion?
....The best solution would be to have the mechanic run a heavier wire direct from one of your batteries. The second best solution would be to disconnest the lighter terminals from the socket and run something like a TP-2 connection from them direct to your radio, that may or mat not help. While you might be thinking the lighter is fused @ 20 amps and the radio @10, why the problem? When you see the wire size for the lighter in your big truck and factor in the real world voltage drop to it, you'll know the answer. I have one coworker with a Connex using the single 2SC2290 final and another with a Uniden 2510 that both frequently have the same issue.
Is idle time an issue for your employer? Does your employer insist irreguardless of the # of hours worked or # of turns made during one shift; all employees in your work group, should try to make the same goal...just wondering?
i have my cobra 29 with the rfx 75 wired direct to the battery ..if you cant go direct to the battery try going to the main fuse block..as far as the general lee working with the same power cord..its only drawing about half as much power say 40 to 50 watts compared to 80 to 100 from the rfx 75.. watts divided by volts = amp draw
isnt radio a fun hobbie
i just want to add my .02 here because i like to experiment alot so any ways here goes ............i did 2 of these on 29s one philly and one china wx and had good luck with them both with a tuned up radio the philly dks 10 and swings 135pep and the wx china does 15 dk and swings 140pep on a dosy..........i didnt try it on the bird,.............oh and on the wx i replaced the cap 1000uf to a 3300uf .........but i didnt see any difference so i just put it back ........again this is just my .02
i just want to add my .02 here because i like to experiment alot so any ways here goes ............i did 2 of these on 29s one philly and one china wx and had good luck with them both with a tuned up radio the philly dks 10 and swings 135pep and the wx china does 15 dk and swings 140pep on a dosy..........i didnt try it on the bird,.............oh and on the wx i replaced the cap 1000uf to a 3300uf .........but i didnt see any difference so i just put it back ........again this is just my .02
Thanks theshortcircuit and johnescashflo for the info; but we can not go direct to the battery. I have had my cobra 200 in the same tractor with no problems and it show 125-140w on my dosy and pulls quite a few amps. The general lee pulls about 4 amps maybe 5 max on hard testing and the RFX-75 showed a pull max of say 7-9 amps max. I only keyed up the radio of the RFX-75 and it wouldn't key up correctly without even talking into it; it should only pull around 3-4 amps well within the rated wire that the tractor and the heavy duty wire I am using. So I will try a few other things tonight and see what happens, by the way the fuse at the block this is connecte to is 15 amps so it shouldn't be a problem and has never shut down my cobra 200gtl. Tony I used the higher value caps on the mod and works perfectly at home, so nothing missing there. It is a possibility the antenna or coax has a leak at high power; but I use my general lee and have an old school swr meter and it shows around 1.6-7 on the scale. I will connect it inline with the RFX and see what reading I get; which may be my problem right there.
Well part of the problem has been solved; the tractor when sitting still has about 11.8-12.4v available and when the tractor is started it jumps to around 13.1-13.6 and that was plenty to drive the radio. I would need to run direct to the battery if I wanted to run while sitting still, but our company wont let us. It performed pretty well until I got out on the road after 10 miles or so my buddy said it sounded garbled and words sounded slurred. The coax may have come loose a little and when I screwed it on tighter it seemed to get better for a little while then back to the garbled words. The cheap coax the furnish us with is the thing rg-58 with the ends that are tapered and pointy. If I keep this tractor I will install a new coax with the gray covering with the solid ends. I have not put an echo board in this cobra 29 special edition chrome so I had my buddy compare my general lee against the cobra when it was running well. First off both had mic gain set at 12 o'clock(otherwise both would overmodulate) and he said the cobra sounded louder that the general lee with the echo off. If I turned the echo on the general Lee would win. Also one other thing I ran the same skythumper mic on both and my buddy who has had cb's for over 30 yrs said the cobra was louder; but the general was stronger with the echo. That is all for now.
I put the cobra with the RFX-75 back in the tractor last night with a good piece of coax and that solved my problem of the garble to the cheap coax floating around during transmission. I also think the skythumper with its high impedence was causing most of the back ground noise in the cobra RFX. I used my Asatatic 636l and I was able to turn the mic gain all the way up; but on the skythumper I had to turn the gain back to 1/2 or my buddies said it picked up too much back ground noise like there was a fan blowing behind me. Overall I think this is a great add on to any of the applications possible; it definitely added some power to the radio but has it draw backs. The swr warning light on ones that have them will most likely have to be trimmed to the off posistion; because when modulate at any level above a regular tone it comes on with my dummy load and it dk=15 and swings to about 80w. It comes on easily with my SRA-158(ceramic mic element) and fairly easy with my Astatic 636l and with my RK-56 it still came on. If you have a set-up with a low swr(which is ideal) and you can get most of the power out rather than reflected you could run into the warning light. But if the swr is a little higher around 1.6-2.0 and your not able to realize the numbers close to 40-80w pep then the light might not come on. Another draw back is the heat; so keep a fan on it if you intend on inclosing it in a box or something similiar. It did pretty well and had a lot more power than a well tuned cobra 29, and even more so that my general lee without the echo on the cobra was more powerful. I am going to install an echo board next and then run it against my general Lee and I am almost certain it will beat the genreal. If anyone would like me to post pictures of my install let me know and I will try to post. I hot glued all parts down and hot glued the wires from the RFX through the 3/8 hole so it would not vibrate and cause the wires to chaffe and cause it to short out. Anyone have any questions let me know.
Moleculo Posted this on another thread last night. I thought it made a point clear to me - as far as the power output of Cobra 29's w/RFX 75.
"Here's why you can get that much power out of a 1969 on an AM radio. This was posted by NomadRadio a while back. He is one good tech...I hope he comes back one day:
Quote:
...an AM-only radio uses a voltage step-up transformer to modulate the final and driver. This roughly doubles the peak voltage FED INTO the final and driver. If you fed steady direct current into this radio's power stages, 28 Volts DC would get you a 45 to 50-Watt carrier. But not for long. A steady carrier that large would be very brief. Since every (28-Volt) voice peak is followed by a (zero-Volts) voice VALLEY, the stress on the final is averaged out, and it will deliver 40-plus peak Watts. Since this remains only 10 to 12 Watts AVERAGE power, the final will take it just fine. Modern SSB radios do NOT contain that step-up transformer, and will only give you about half as much PEP per transistor." -end quotes
This would explain why a Cobra 29 or other AM radio will see the high numbers for the Powerband RFX 75 - while "SSB" radios don'/can't see the same numbers!
"Here's why you can get that much power out of a 1969 on an AM radio. This was posted by NomadRadio a while back. He is one good tech...I hope he comes back one day:
Quote:
...an AM-only radio uses a voltage step-up transformer to modulate the final and driver. This roughly doubles the peak voltage FED INTO the final and driver. If you fed steady direct current into this radio's power stages, 28 Volts DC would get you a 45 to 50-Watt carrier. But not for long. A steady carrier that large would be very brief. Since every (28-Volt) voice peak is followed by a (zero-Volts) voice VALLEY, the stress on the final is averaged out, and it will deliver 40-plus peak Watts. Since this remains only 10 to 12 Watts AVERAGE power, the final will take it just fine. Modern SSB radios do NOT contain that step-up transformer, and will only give you about half as much PEP per transistor." -end quotes
This would explain why a Cobra 29 or other AM radio will see the high numbers for the Powerband RFX 75 - while "SSB" radios don'/can't see the same numbers!