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5 points

My 2X8 install

I'll start this off with my install of a Hopper Built 2X8 in my 1998 Chevy Lumina. Ist off this car has the 3800 2nd Series motor and i upgraded the original alt with a CS-144 Delco alt. with a 200 amp rebuild kit with brg's, brushes, diode trio, rectifier bridge, regulator and stator. Up until i acquired a 1000 amp carbon pile battery tester, i was unable to test the amp output on it. As some of you may already know, you need a high amp carbon pile alt. tester to get above 200 amp's and i didn't have anyone local to do this other than O'rleyes who could do a overall check but no full amp output test. So back to testing the alt. You need to over come the CCA on the battery in the chassis and hook a amp probe to the output of the alt. By loading the battery to around 800 amp's with the engine at 2000 rpm i was able to load down the alt and tell it was putting out 180 to 190 amp's. Which is within 10% so it's up to par. By checking the alt in the car i was also able to take note of any belt slippage on the surpentine belt. Now i did the Big 3 cable upgrade with 2/0 cables from the negative side of the battery to the body and case ground at the alt and a 2/0 cable from the positive battery cable to the output of the alt. just note that these cable are welding cable with very fine strand's in them. I then ran a 2/0 ground cable from the alt ground to my trunk area and a 2/0 cable from the alt output lug through a 250 amp mega fuse, through a high amp battery switch to disconnect both battery's in case i need to service them. Then this positive cable also run's to the trunk area. In the trunk a mounted 2, 750 CCA blue top optima battery's, the 2X8 amp on a large battery tray from a truck and ran the negative cable from the alt ground point to the negative post on the 1st battery and the positive battery cable from the alt output lug through another 250 amp mega fuse at the battery's then to the positive battery lug of the 2nd battery. Then i jumped the pos. and neg. terminal's with a jumper and wired in the 2/0 cables to the 2X8 amp. now in order to correctly utilize both battery's as one large battery, you must chris cross the battery connection's to the amp, another word's there still 12 volt's, but the input from the main battery's is is on one stud of the pos and neg, and the amp is hooked to the opposite stud's. The positive cable then run's from the 2nd battery positive stud through another 250 mega fuse, (to protect a dead short in the 2X8 amp) to the builder supplied 175 amp Anderson connector and the negative cable off the 1st battery negative stud to the same Anderson connector. I have sense removed the 175 amp Anderson connector and hard wired the negative cable directly to the ground lug on the amp and used one of those twist lock welding connectors on the positive side. keep in mind all cable length's are the same length.. Now to the radio, I'm using a Top Gun Technologies Quad 5 radio with RG8X cable from the radio to the amp, Then to a 3 mag mounted predator 10K antenna in the middle of my roof. Now i don't drive this car much and i ran the system for 4 month's with out much of a problem, I sent the amp back to the builder for a check up and the builder said there were some cap's bad, He replaced them and told me there was a problem with my antenna matching. I then bought some LMR240UF coax and ran it from the radio to the amp and from the amp to my mag mount. Now this mag mount is a Tram-Browning mount and the way the coax connect's to the mount is really fubar. So i removed the original mount and mounted a gunny puck to the 3 mag mount. I got the amp back from the builder and he told me to set the dead key from the radio to the amp to 400 watts dead key. When i got ready to set the amp back up, Mark 2WR-057 was in town and he was helping me set it up, Long story short, we got the dead key set up to 350 watt's and Mark was watching the bird meter and said there was smoke coming from the 2X8. That ended the testing, With no time to send the amp back before my trip to Branson MO. for a cb break, I contacted the builder and he ok'd me to pull the cover off and take pictures. Well it smoked 2 pill's in the 8 pill section. I took the amp back to Branson with me, After the Branson break was over i drove to Iowa for my family reunion. In the mean time i went to Lincoln, NE to meed a couple buddy's that in 2 week's will be driving to the Manchester TN break. I gave them the amp, They brought it to TN with them and i handed the amp to a friend of the builder to take to him, (This saved me 80$ in shipping). The builder replaced all 8 pill's and sent the amp back to me. Once i got the amp back i learned about antenna reflection. There's more to setting up a antenna beside setting it up with a analyzer. With 2WR-0351 Jeremy's help, we were checking the reflection off the antenna and found out the amp was putting out 800 watt'a and reflecting back 200 watt's. The builder told me to adjust the whip length according to the reflection and try and get the reflection down as low as we could. The lowest we got the reflection down to was 55 to 60 watt's, but recheckng the SWR with out the amp on with the analyzer was over 2. We figured out the mag mount had to go. I pulled the head liner out of the car and drilled a hole to mount the Gunny Puck directly to the roof. We then set out to fine tune the coax to it's resonate frequency and with my MFJ-269C analyzer and even borrowed 2WR-303 Terry's analyzer too and found some differences between the two analyzer's. My analyzer would read with a dummy load in in place of the antenna a ohm reading of 59 ohm's where Terry's analyzer read 50 ohm's, Mine would read a X factor of 0 and Terry's would read 7. So Jeremy and i set out to fine tune the coax with my analyzer sense it would read the X factor of 0. Sense i bought 100 feet of LMR240 and the 1st attempt of replacing the coax was in length's that ran form point A to B used up quite a chunk of it, we decided to experiment the fine tuning of coax on RG8X, witch i had plenty to cut up and the 1st attempt to fine tune the coax measured out to be aprox. 22 feet, 2 1/2 inches at a resonate frequency of 27.200, I then decided to use the piece of RG8X from the radio to the amp to save the LMR240 to go from the amp to the puck. Talking to other's about fine tuning coax to it's resonate frequency i came up with the fact that Jeremy and i were doing it wrong with leaving the end of the coax open, we needed to short the cut end. In the mean time, Jeremy had bought a Rig Expert AA-35 Zoom analyzer and Jeremy let me borrow it for 2 week's or so. Now i have my MFJ, Terry's MFJ and Jeremy's Rig Expert. I found that the Rig Expert will do a test and come rite out and tell you the resonate frequency that your coax is tuned to. I decided to use Jeremy's Rig Expert to fine tune the coax. I took the 22 foot long piece of LMR240 that i previously fine tuned with the end open using my MFJ, Cut off 3 feet for a jumper, which left me 19 feet. I cut the coax down using the Rig Expert and shorting the end down to 14.4 feet. Using the math to figure the velocity factor of the LMR240 said a length of 15.2 feet and i was sweating it when i got to 15 feet and the coax wasn't resonate yet. The worst part about cutting and fine tuning the coax is starting off too short in the 1st place. I mounted the coax to the puck and started tuning the antenna. I found that the Predator 10K using the 27 inch shaft would tune better than the 12 inch shaft, so i went with the 27 inch shaft. The end result with the 27 inch shaft is at 27.200 Mhz is, With the Rig Expert i got a SWR of 1.04, 51.9 OHM's and a X factor of 0.14. Using my MFJ i got a SWR of 1.1, Ohm's were 57 and a X factor of 0, Terry's MFJ had a SWR of 1.4, at 48 ohm's and a X factor of 17. Once all was good with the coax to the puch i reinstalled the head liner in the car and did more testing on the amp. While i had the amp out installing the updated welding lead twist connection, i decided i wanted to know exactly how much battery voltage was getting to the amp directly inside it. So i took a Motorola power cord left over from my work 20, Cut it to aprox. 2 feet long, put loom over the wires and fed it through the hole where the power wires run into the amp and soldered them directly to the power and ground connection's inside the amp. This Motorola power cord has 12 gauge wires on it and a dual bullet male, female connector on the end. I then made another cable to mate to it and connect directly to my VOM meter. I can check the voltage to the amp inside, The voltage to the batt's in the trunk and i even made a longer lead to hook directly to the alt output and ground. this way i can check for any voltage drop's in the system. I have 3 of the same VOM so there's no difference in the meter's read out while checking the system out. Now the end result in all is the amp output is 375 watt's dead Key with 750 watt's PEP with 0 reflection, Yes ZERO. Remember i started with 200 Watt's reflection on the mag mount, 55 to 60 watts with the Gunny Puck mounted to the roof and now 0 watt's. This is using a Swan CN-901 HP3 SWR meter. Testing with a MFJ-267 SWR meter the result's were Lower at 700 PEP and 5 watt's reflection. I like the Swan meter because the needle movement is quicker. I haven't checked the reflection using the bird meter yet. The thing's that still need's resolved is the voltage drop at the amp. The voltage drop's to 12.2 at 2,000 engine rpm while keying up, I've load tested each of the blue top batt's and they load test at 800 CCA. But when you load test the battery bank in the trunk and load the batt's down to 200 amp's, the voltage is already down to 12 volt's. I eather need a higher output alt or install a super cap. I can get a 370 Amp alt from Mech Man and they claime it will fit my application. or the super cap. I believe this is the reason the 2X8 output is low. Even though the CCA on the Blue top's is 800 CCA each, you have to remember the CCA test is loading the batt's to 9.6 volt's not 12 volt's. The other thing is the motor cut's out and misses when i key up, and the Tachometer bounces around. I ran a test through my MFJ-250 Dummy load and there's no miss, stumble or tach mess up when keying up. So the problem is RF related. I pulled the engine ECM out and found it mounted in a plastic holder. I took the same 1 inch flat grounding strap i used to bond all the door's, trunk, hood and bonded the ECM through a cover screw to ground. Now there's no miss or stumble in the motor, But the Tach still bounces around when i key up. The next step with the bouncing tach is to put ferrite bead's around the cam and crankshaft sensor wires. I'll try the ones you can snap around the wires 1st. Hope i didn't bore everyone too much. I think the main thing is antenna reflection and knowing the end result. Once you know and correct it, your closer to getting your system all in tune. I may not be doing much about the low voltage sense Winter is here now, But i'll be researching the solution. 73 from 2WR-267_Scott