Re: QRP SWR meter recommendation? #ubitx

Gordon Gibby <ggibby@...>

If you look at the schematic of your tuner, there is probably one or two resistors in a voltage divider chain that you could parallel  something with to increase the voltage that gets to the meter.  Either before or after the rectifier diode or diodes.  Just make sure that whatever gets done to the forward circuit is the same as what gets done to the reverse circuit

Secondly, you don’t have to have a full-scale indication to figure out your swr.  It’s a relative measurement.   If the reverse is 50% of the forward on the meter range, most of the time youre at 3 to 1.  You could look at how yours is calibrated to verify that.   

You can first do a rough tune just using the receiver, adjusting for loudest receive noise. Then get the transmitter going & null out the return as low as you can.

Some of the other people may already have pointed it out, but there are several excellent little qrp swr kits out there that implement a simple resistive bridge circuit going to an LED diode, and you adjust tuner for the dimmest diode or so.   They are basically comparing against a 50 Ohm load and when your Antenna has been transformed into 50 ohms there is no longer relative voltage between the Antenna and the reference 50 ohms, so the light emitting diode goes dark.


On Aug 20, 2018, at 12:39, V Zecchinelli <n1vin@...> wrote:

I use this one.

ince, N1VIN

On 8/20/2018 11:31 AM, Mike KK7ER wrote:
So far I have been setting the antenna tuner using my Kenwood and then swapping in the uBITX.  But now we want to take the uBITX on the road.  Problem is that the uBITX does not put out enough power for full deflection on our MFJ versa tuner II so we cannot get an accurate SWR reading to tune the antenna.  Does anyone have recommendations for a QRP SWR meter?  Thanks!

73, Mike KK7ER
(and son KI7ZZS)

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