Electronics > RF, Microwave, Ham Radio

Broadband amplifier for White noise source?

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rwgast_lowlevellogicdesin:
I bought a ham it up 1.3 upconverter, I mostly bought it because it has a built on RF white noise source which I have read works much better than any of the ebay sources. I thought about building one but the Ham it Up seemed to be a bargain since it is two devices in one.

Anyways the noise source is pretty good although not linear, after UHF it starts dropping off slowly. So I have two reasons for amplification #1 I would like to get the thing working better up in the L and S bands, secondly I would like to be able to hook it up to an antenna and cause true interference for testing shielding etc. Before anyone gets up on there hi horse I am only talking about a few hundred milliwatts or even better 1 watt with attenuation to control the amount of crap it spews out. My house is also made of concrete so all my antennas really need to be outside (unless its a yagi pointed through window) to do anything, and I need wifi repeaters just to get decent signal 2 rooms away.

I have never built an amplifier for a transmitter, most are based on certain bands or frequency so I haven't had much luck finding any schematics for something broadband. On the small scale would something like an MMIC work, I have some mar6, psa4-5043 which are both broadband mini circuits mmic's used in most SDR LNA's. I also have some mav-11's which mini circuits calls a monolithic amplifier, im not sure what that means but its noise floor is about 3db instead under 1db. The mar6 and psa4 are easy enough to use as far as building LNA's for reception... I have always been under the impression these are only to be used for RX only, after reading there data sheets I see nothing about that, nor does it say the mav11 can't be used for transmission....

The reason I would like to get up to one watt is if I can is two fold, first like I said my house is an RF black hole and I want to test out some real world scenarios. Secondly at some point I would like to make a broadband amplifier that is more in the 25-50 watt range for a GNU radio controlled broadband transmitter, and im considering this a good first experimentation project.

rwgast_lowlevellogicdesin:
Well im not to sure why no one answered this question but I found a few chips that can boost in to the few hundred milliwatt range, Im still confused if something like a mar 6 or mav 11 will work since the datasheet does not mention TX.

I guess what confuses me is I have a Radio Shack HTA20 which is a 2m 30 watt power amp that has never been used. Is the ony thing that makes it a "2M' amp is the speed of the transistors and the filters? What would happen if one stripped the filters out and used it at 50mhz? Im not sure why it blow anything up as long as the impeadence matches and the transistors or fets switch fast enough.

I would like to strip the filter out and use it as a broadband amp from HF to 2M or 70cm if that will work but I dont want to fry it either so if anyone could explain the details of why this may be a bad idea please do.

Yansi:
I'm not an RF expert though, but the datasheets clearly specifiey maximum output level in dBm and also the P1dB compression point. So what else would you need to use a MMIC as an output power stage? 

Here's a small comparison list. ERA5 gives the most power, almost 100mW.
http://f5ad.free.fr/Docs_ATV/MMICs.pdf

If you need more power, just find more beefier gizmo, like CLY5: http://www.mouser.com/ds/2/412/CLY5-198574.pdf
That one kicks ass. 1W @1.8GHz.

rfeecs:

--- Quote from: rwgast_lowlevellogicdesin on June 21, 2016, 04:33:15 pm --- Is the ony thing that makes it a "2M' amp is the speed of the transistors and the filters?

--- End quote ---

No.  So that is a 144-148 MHz 30 Watt amplifier.  It will be designed specifically for that band.  The matching networks will be narrow band.  Removing the filters will not give you a broadband amplifier.  Not to say for sure that you won't get some gain and output power at 50MHz, but most likely it will not work well out of the intended band of operation.

MAR-6 and MAV-11 are darlington gain blocks.  They are amplifiers, so yes they can be used to amplify power.  But P1dB is very low, so you are not going to get much power.  There are similar HBT gain blocks that can put out a little more.  HMC475 can put out more than 100mW for example.  These types of parts are made by Hittite (Analog Devices), Qorvo, Skyworks, etc.  Available from major distributors.

If you want to go higher power for a very broadband amp, you need higher voltage.  So there are GaN parts, but you won't want to pay for them.  A popular military application similar to yours is for jamming cell phones to prevent triggering "Improvised Explosive Devices."

Note CLY5 from previous post is just a transistor, not a MMIC.  It is unmatched.  You have to design a matching network to get the performance quoted on the datasheet and you are back to a narrow band power amplifier.

CJay:

--- Quote from: rwgast_lowlevellogicdesin on June 21, 2016, 04:33:15 pm ---Well im not to sure why no one answered this question but I found a few chips that can boost in to the few hundred milliwatt range, Im still confused if something like a mar 6 or mav 11 will work since the datasheet does not mention TX.

I guess what confuses me is I have a Radio Shack HTA20 which is a 2m 30 watt power amp that has never been used. Is the ony thing that makes it a "2M' amp is the speed of the transistors and the filters? What would happen if one stripped the filters out and used it at 50mhz? Im not sure why it blow anything up as long as the impeadence matches and the transistors or fets switch fast enough.

I would like to strip the filter out and use it as a broadband amp from HF to 2M or 70cm if that will work but I dont want to fry it either so if anyone could explain the details of why this may be a bad idea please do.

--- End quote ---

No reason you can't use a MAV11 for TX, it should do a few tens of milliwatts. There are better solutions, some easily available MMIC modules are good to 1W and you can use them push-pull into a broadband transformer.

Stripping the filters out, not a great idea, they're usually designed to match the driver and load to the transistor, you're better redesigning them for 50MHz by the looks of it the HTA20 uses the PCB as an element of the filters so it'd take some effort.

You'll also need to be sure it doesn't oscillate.

Broadbanding it, not so easy, it may be better to build from scratch for the amount of effort it may take,

Depent

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