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When tuning the VFO signal generator does it limit the display to 200 MHz and 3.5 KHz?
If not what does it do when you goes past the chip limits?

Thanks
richard

Richard

The display will read out the frequency well beyond the limits of the chip to produce a signal at that reading. I checked mine and at about 100 MHz and the voltage of the signal starts to go down. At about 200 MHz it is very weak and somewhere above that no signal. I would say from those rudimentary facts the VFO is practical to use from about 3MHz to about 100MHz with out additional circuitry to boost the signal. Most of us are interested in the HF spectrum anyway and if you were interested in VHF or UHF frequencies there are other methods to get to those bands.

Bill N7EU

Hi,

my experience with the QRP Labs VFO/SigGen is different. The chip is M5351A.
It works well from 3.3 kHz to 310 MHz.

Since it gives out a square wave signal we can not easily see the power level.
The level at 50 MHz was around +15 dBm, at 310 MHz the level was still over +10 dBm.
The power was measured without output LPFs, so inherent all harmonics. At 50 Ohm load.
Since the output is RF with a DC bias I used a decoupling C followed by a 20 dB 50 Ohm attenuator. All SMA.
At lower frequencies the frequency was measured directly at the TTL (DC) counter input.?

73 Bojan S53DZ

And Richard, to your question:
If you dial a frequency bellow 3.3 kHz or over 570 MHz you get an "E" symbol on the LCD.

73 Bojan S53DZ