The AM Forum

I had a thunder run to upstate NY and installed the ARC-5 station for the trip. It rained the whole drive both ways. Had plenty of contacts and was in a long QSO with Tim WA1HLR when all the sudden my windshield wipers start seriously slowing... - this is not a good sign when you are in the middle of Vermont.

Anyway I killed both the mobile station and the lights at that point!

Turns out my Maxima alternator was getting long in the tooth and did not like charging the battery, running lights and wipers and an AM station! Diagnosed as a loss of one of the phase rectifiers by the shop. Printout said - Excessive Ripple.

Mike WU2D

I use a 92AH AGM battery mounted right next to the radio thinking to avoid this kind of thing. The PA on my setup has 8 transistors and draws about 40-70A at 100W carrier-400W peaks. Not sure how effective it is, but I figure more juice will come from the nearby battery than from the system which is 20FT away by 4 GA + and - wires. I also have several of those large ferrite suppressors clamped on the + and - cables, and they do sing with modulation. The stock GM 100A alternator has not died yet even with 135K on it. I do not have long QSOs though. Could it be a coincidence that the alternator died? Or coult it be pulsating (audio) current drawn from the alternator as a reason? What's the load of the set on TX, maybe 35A?  

Can we have pics of an ARC-5 installed in a Maxima?

Run a heavy gauge wire from the new alt to the battery.  Run a second Ground terminal from the battery to the Frame or inside fender. These cars have light gauge wires and thin Grounds.

I would love to see some pics also!

In the 90s, I had a 6 transistor amp installed in a VW Jetta 16V.  I was keyed down going down the highway on AM and heard a loud banging noise..  I pulled over and found the alternator Broke OFF its mount.. Both ears where still bolted to the motor and the alt was laying down under the car hanging by its wires LOL!!!


C

ARC 5 Mobile A-GO-GO

I have been running this station for almost 10 years with no issues. The power supply is a Heath that has been rewired from doubler to full wave bridge for a solid 450V instead of the 800V.

The modulator is an interesting homebrew design that runs directly on 12V of the vehicle. It is an LM380 driving a pair of IRF840 Mosfets via a small driver transformer. The mosfets are biased to conventional AB push-pull drive the secondary of a backward 6.3V 5A fillament XFMR into a 8 uF NPC and a 10 Hy choke for Modified Hiesing. Hint - never run DC on an AC transformer for modulation service or you risk core sturation. Overall feedback to the LM380 and Negative cycle loading assures a clean strong modulation of the 20 Watt carrier with 450V on the plates. The microphone is the Shure 527C amplified potato mic. I did this modulator about 10 years ago. It is dirt simple, cheap and tough.

Mike, that is a very cool mobile setup!  "Sorry babe, you have to sit in the back seat!"  8)

JT

I don't suppose you have the schematic for that modulator?

Very cool setup!

That is very cool. I guess I was imagining dynamotors but the inverter supply is a much better way.

You mention Dynamotors...somewhere in the last few years I saw some pictures of a guy's car stereo amp. Parallel/Pushpull 1625s and a Dynamotor HV supply. It was rack mounted in his van. Not very practical but very cool!

heh heh heh heh "not very practical"

Talking about mobile setups taking up the passenger seat, my first date in my first car had to sit in the back seat of my 62 Dodge Lancer.  The front seat was fully occupied with an Elmac AF-67 and an SX-140 rcvr.  Had a Master Mobile Slim Jim antenna.  I think on the second date, I borrowed my dads car!
Regards,
Joe, W3GMS     

Was her name "Rose" as in "second hand Rose?" ;D ;D

She accepted the radio thing pretty well in the beginning but then not so....the rest they say is history and sometimes it good NOT to look in the rear view mirror!! 
Regards,
Joe, W3GMS

Memory fade! It's push pull 6146s...

http://www.montagar.com/~patj/tubeart.htm

Of course if you really want tube sound in your car and have $2649 to spare...

http://milbert.com/bam235ab

Sorry about the thread drift  :)!

Joe, that reminds me of the story my dad told me about running his HRO on a vibrator power supply in his 41 chevy.  He placed the back of the HRO against the passenger side door.  This setup required the ladies to sit in the middle of the front seat!

Hi Rick,
Interesting comment from your Dad.  Well at least they were within arms reach!  I wonder if he did that on purpose??? 

Thats the first person that I have heard of that used an HRO mobile.  I have several of those early ones around here.  Maybe that would look good under the dash of my newly acquired 1974 Ford F-100.  It sure has a long dash and its all metal.
Regards,
Joe, W3GMS 

They replaced the alternator with a 110 AMP Bosch job. That should be enough juice!