Anyone measured power output of their bubble?

[MightyGuru]

UPDATE

I have replaced the ROS-2500+ with a ROS-2230-119+. With the added 4.5db output of this new VCO my 1900 band output has increased to ~220mW. I am also running SXB-4089Z's on both stages. My 800 band output is at ~400mW now.

Obviously the biggest drawback now is heat and current. The unit is drawing about 1.2A from the battery.

[inh]

Hi mightyG - I've been testing those vcos too. would you be able to take a photo of what you have? with an indication of what the component values are?

your results are good...

[MightyGuru]

Hi mightyG - I've been testing those vcos too. would you be able to take a photo of what you have? with an indication of what the component values are? your results are good...

The passives are shown in the datasheet for the SXB-4089Z.

[inh]

Hi MightyG - very interesting. I note:

1- on the IF side you have the 1ohm (is that the value as per datasheet?) resistor before rather than after the c6/c5 input caps. I assume the WB post vco preamp signal also suffers some attenuation from the siphoning off to the PLL...
I get repeated transistor blows here when using values under 18 ohms ... (but not always!)

2- I tried replacing c5 (1.2pF) called c40 in the WB with 2.7pF on the RF side, between the vco and the transistor, and got a big power increase...
of course it may be a power increase too far with the 2230-119, but the SXB does claim to be capable of 500mA!

[MightyGuru]

Hi MightyG - very interesting. I note:

1- on the IF side you have the 1ohm (is that the value as per datasheet?) resistor before rather than after the c6/c5 input caps. I assume the WB post vco preamp signal also suffers some attenuation from the siphoning off to the PLL...
I get repeated transistor blows here when using values under 18 ohms ... (but not always!)

2- I tried replacing c5 (1.2pF) called c40 in the WB with 2.7pF on the RF side, between the vco and the transistor, and got a big power increase...
of course it may be a power increase too far with the 2230-119, but the SXB does claim to be capable of 500mA!

1. I am not using the 1 Ohnm resistor specified in the datasheet. The resistor following the VCO is 18 Ohm. This is for attenuation. I would get frequent tuning errors otherwise.
2. I might have to try the 2.7pF mod. I am still well under the 1/2W output on the 1900 side.

Would you mind posting a picture of your output/gain stage? I'm always interested in how others are placing the passives.

[inh]

Hi MightyG - I actually have about 12 different variations running successfully and unsuccessfully at the moment, so I need a bit of time to organise what to show you, but yes I will post pics. I'm flying to San Francisco shortly until 15th, so there may be a delay.

I will post though. I've been speaking to Sirenza at great length about these transistors, so have a few perspectives, including 2 different versions of my homemade boards - built to Sirenza specs...

[inh]

sorry to be so dumb MightyG - I just took some jpegs of my passives and boards, but I can't work out how to upload them - how do you do it?

[MightyGuru]

sorry to be so dumb MightyG - I just took some jpegs of my passives and boards, but I can't work out how to upload them - how do you do it?

I upload/host them at http://www.imageshack.us/ . It is a free image hosting service. I then take the link provided by imageshack and put it in the post with the Img tag.

[powerpants]

I measured my output today. Here's what I got. I've got a standard by-the-schematic build. I'd appreciate it if somebody would tell me if these numbers are about right for a stock build!

For the ROS-1700
~17.5dBm/50mW

For the ROS-2500
~11.5dBm/12mW

(This one seems a bit low, but there's no shorts across my SXA.....)

[powerpants]

anybody?

[inh]

low end of range, particularly for the rf side...

[powerpants]

That's with full attenuation from the schematic....I wanted to get a reference design working before I start playing with the values - if my results are low, even for full attenuation, what could be causing this low power?

[inh]

microwave design is a black art

http://www.microwaves101.com/encycloped ... fthumb.cfm

this link will start you understanding where your losses are, microwaves and the rf sections of the wb can be thought of as almost optical cavities, with reflections and transmissions similar to those of light. I have a theory that impedance matching is comparable to matching the refractive indices of different light transmitting materials.

a lot of trial and error, with some ideas about wavelengths, solder joints, stripline transission line theory will help.

have fun - it is very weird stuff...

[andyman]

MightyGuru

I've got very good results on my 800-900mhz side of things using the passives as specified in the 4089 data sheet but on the 1.9ghz side its just horrible. Can you post pix and some details on what you did on this side? I'm still using the stock VCO's.