source = http://www.zerobeat.net/g3ycc/ledswr.htm

This simple SWR bridge uses a superbright LED instead of a meter and was described by G0WQR in Sprat 93. He found the LED is fully illuminated with less than 1 watt output and extinguishes when minimum VSWR is achieved. It can be made very small and lends itself to portable use.

source = http://www.zerobeat.net/g3ycc/res_swr.htm

The bridge shown is popular with QRPers. There is no setting up to do and the circuit need not be laid out symetrically as with other designs. I used a tiny meter bought from Kanga (UK), only about 0.75“ x 1”, but any meter less than 1 mA should do OK. Although a 3-way switch is shown, a DPDT toggle can be used, as once the bridge is calibrated, only an 'in/out' switch is required. Note - This type of bridge must be switched out of circuit when transmitting. Tune the ATU for minimum SWR then switch out of circuit and transmit as normal. The resistors shown need only be 1/4 watt types. The unit can be made very compact and can be useful in a portable set-up. I incorporated a bridge of this sort with a small L-match ATU for 20m, in a box 2.75“ x 1.75”. I used a plastic box, lined with PCB material for shielding, resulting in a light and small unit. Frank, G3YCC

• https://github.com/mfhepp/tinyswr

Includes a 2 LEDs SWR indicator

Small QRP tuner by DF3OS (Marcin Swietlinski, SP5JNW, February 2007)

• http://vu2spf.blogspot.com/2016/11/swr-meter-for-ham-fest-india-2016_57.html
• https://www.qsl.net/n9zia/wireless/appendixF.html
• Homebrew HF SWR/Power Meter (Bill LEONARD, N0CU)
• Homebrew - Boxing up the power and SWR meter (Eamon SKELTON, EI9GQ, RadCom 12/2014)
• ALTAI CB SWR Meter Conversion for HF Bands (RSARS, G8ODE, 02/2011)