Motorola 900 300w Cell Amp

[thehead7]

I just bought a 900mhz 300W cell amp on ebay (actually, it's cell band, not 900, but whatever).

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %3AIT&rd=1

I'm wondering if anyone has played with one of these, and if so, what have you discovered?

The auction says that the circulators on the output are spec'd for up to 904, which is, I think, my first obstacle. Can anyone tell me: Will they go up to 927 without adverse effects? If not, can I bypass them without adverse effects? I will be running an isolator between the amp and the cans...

What all does the control board do in this thing, and what do I need to do to interface to it, or do I just need to pull the board and build my own control circuitry? If I can leave the control circuitry in place, does anyone know where I can get one of the weird little connectors?

My goal is to rig this thing to put out about 110-125w. It would seem to me that I could remove the VCC line from the two sections on the right side and be good to go on that, and I could then fine tune my power output with my drive level.

From disabling half of the amp, this thing should run pretty cool. If it is rated at 300w, it would be able to do that continuous duty, so running only half the amp, I don't expect heat issues... (Plus I'm going to add a rather heavy fan with thermistor...

If anyone has got some info on this thing, please let me know.

Also, if anyone knows where I could dig up a big enough 28v power supply, I'd appreciate it. (I would probably need about a 20A, I should think...)

THanks,
John

[ExKa|iBuR]

Hook it up to a 3 watt bag phone. hah

-Mike

[thehead7]

Well, there's a couple problems with that. I'm not sure 3 watts will drive the amp in a stable manner. Also, I would have to modify the bag phone to have seperate TX and RX connections, and I'd also need a rather heavy duty duplexer... While i'm at it, I might as well add an LNA to the RX side...

My mom still has an AMPS phone in her car. Perhaps she'd like a little better performance? (And brain cancer?)

-head

[Jonathan KC8RYW]

Also, if anyone knows where I could dig up a big enough 28v power supply, I'd appreciate it. (I would probably need about a 20A, I should think...)

Try the 24 volt power supplies from a PURC 5000. There is a surplus guy on eBay who sells them all the time.

[thehead7]

Thanks, I think I have found the guy...

-j

[Jonathan KC8RYW]

Also, I think Sun workstations used to use that sort of connector [or something similar] for video.

[thehead7]

Yeah, it's similar. The sun workstation is a little different, though. I think the RF connectors are different.

I'm almost 100% positive that it is an Amphenol product, but I couldn't find it on their site earlier. I'll have to look at a few different sources. I think I'm going to end up just replacing that connector with a DB25 or something, adding Type N for input and output, and using a connector of some sort for power...

[elnerdo]

Old Sun connectors are called "13W3"... I'm not sure if this is a 13W3, but it looks like it might be.

(Edit: Sorry, I was going from memory of the connector pic on the amp... that's definitely not a 13W3 connector.)

[Jonathan KC8RYW]

To bring this back from the dead...

I have a water-damaged cellular PA with that same type of connector. The only difference is that this connector is male, while yours is female. It also has those two "spikes" sticking out in the two corners of the connector like yours. Stamped on the connector: "DC-22070 Cinch M."

Hope this helps.