33cm band amp

[KC9TNQ]

Hello all, I'm going to attempt to design an amplifier for the 33cm band. The radio it will work with transmits a FHSS signal across the entire 902-928Mhz band at 1 watt. I am trying to cross the town ( about a mile ) so I believe just 10 watts will do. 33cm Amps seem rare and expensive so building is my only option, could anyone point me in the right direction and recommended a chip that can go from 1 watt to 10 watts in the 900Mhz band?

Thank you all.

[W4OP]

There were at least piles of abandoned cell phone amps for free or near free- most of the 33cM guys are using these.
Other companies like Down East Microwave also make 33cM amplifiers.
I just looked on eBay and they are still available for near free.
Building at 33cM is not for beginners or those without the proper test equipment and design experience.
I built a solid state 500W 23cM amp for EME and although it turned out fine, the design process was slow.

Dale W4OP

[KM1H]

I was given a pair of 150W modules and all it needed was a couple of combiners and power.
OTOH I will need two more to catch up to the pair of older cell site Motorola surplus Eimac cavities using a 3CX400U7. A DEM transverter and small brick completes the process.

Carl

[KC9TNQ]

Are you talking about http://www.ebay.com/itm/sunhans-GSM-...ht_2263wt_1163? These don't seem to cover my band, ( at least they claim not to ) and I don't need a pre-amp on the receive side. I also will need two and at $60 a piece these are not "near free". Do you know what kinda chip these have in them?

~kc9tnq

[W4OP]

No, those are end user low power amps.
Carl and I are referring to surplus bricks from decommissioned 900MHz cell phone sites. I helped disassemble a site and picked up 6 of the 150W bricks for free.
See:
http://www.qsl.net/k/kb9mwr/projects...ifications.pdf
But if you think $60 is not near free- get ready for sticker shock when you start purchasing parts to design your own amplifier.
I spent $1700 just on active devices alone for my EME amplifier.

Dale W4OP

[KC9TNQ]

Well I don't know how you have access to decommissioned cell sites, but I don't and I cant find a single listing on ebay ( not sure what to even search for ). Besides, i'm looking for just 10 watts, I'm thinking a $5 Mitsubishi amp chip, but was just checking for suggestions first.

~kc9tnq

[K7JEM]

Going back to the OP, it looks like you have a 1 watt FHSS radio already, and you want to communicate 1 mile. That should be no problem with any sort of directional antenna on each end, and a decent line of sight path. I certainly don't think you need 10 watts.

For that distance, a pair of 50mW WIFI type links will work, attached to decent antennas. I have actually done WIFI at 30mW at a distance of 70 miles, but we were using 5 foot dishes on each end.

Joe

[KC9TNQ]

It is for a handheld mobile radio so I would like to keep the omni antenna, also I am in the middle of a city, so no line of sight. I'm not even sure 10watt will do but that's my target for this project.

~kc9tnq

[W4OP]

Here's another thought. Mitsubishi makes a number of modules for that band. The RA13H8891MB for example is a 13W device for around $32. The nice part is that the input/output matching is all internal to the device, you only need to provide a bias regulator, bypass caps and Vdd.
Look at RF Parts:
http://www.rfparts.com/module_sau-sav.html#sav6

Here's the application note:
http://www.rfparts.com/pdf_docs/RA/ra13h8891mb.pdf

Hope this helps. It sounds as though the surplus cell amps are too high power for what you want to do.

Dale W4OP

[KC9TNQ]

This is about it, but these all input at 100mW, but my radio outputs 1W, so would it be reasonable to add some kind of attenuator followed by the amp? Will this affect the noise to much?

~kc9tnq