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VCO Tuning Range and Power OP

by soram on Thu Nov 01, 2012 12:24 pm

I thought my Wavebubble had ceased to function recently and found I couldn't block an iPhone. Everything I could measure was fine so I borrowed an SA.

On first look I thought it was because the high VCO power was substantially less than the low range VCO. I put the iPhone into field test mode and couldn't shift it off 3G (Vodafone UMTS). After being more critical (accurate) with the programming frequency choice I could bounce it repeatedly off UMTS. It would then shift to the 8/900 MHz range and I could easily knock it off that. It then however went up to the 1800MHz band and I have problems with that. The high level VCO output seems very non linear and I cannot seem to block 1800 and 2100 at the same time.

Anybody ideas here? I thought of reducing the tuning voltage frequency. Might that help? Any recommendations for something to try while I have the SA?
The VCO power specification is only 0.5dB less that the low range one but I have always had substantially less.....

I was half thinking of adding a second main board with another VCO in the 2GHz range and maybe one for 5GHz for the N Wifi band!

The 5GHz VCO spec is very low power <1dB and 300mA! Any ideas if it would be even possible to amplify to useful levels?

Posts: 22
Joined: Sat Jan 15, 2011 5:32 am

Re: VCO Tuning Range and Power OP

by soram on Thu Nov 01, 2012 3:06 pm

OK a quick update. I can still hammer the UMTS signal if I keep the VCO operating range span at about 100MHz. If I try to go larger e.g to also take out WiFi at 2.4GHz (Range now about 500 MHz) it won't knock out the phone. Similarly if I go lower and try to include the 1800 GSM range.

Could it be the amount of power over time the VCO is actually transmitting in the operating range of the phone? The oscillator is operating at 25KHz. I'm guessing making this faster may help as it may hit the phone more often but is the trade off then for shorter duration?

Anybody got a clue here? Would it be beneficial to increase the sawtooth frequency?
Posts: 22
Joined: Sat Jan 15, 2011 5:32 am