160 meters?

[wa3yre]

Greeting-

One of my favorite bands is 160 meters. Is there anything keeping me from building for 160 meters?


73

-Brett
wa3yre

[kf7yrs]

I would think you could if you substituted a 160m LPF for one off the standard bands. Try listening on 160m to checkout the sensitivity. Then TX through a wattmeter into a dummy load to get an idea of power output. Neither RX nor TX should be bothered by the inappropriate but higher frequency LPF on the output.

I have successfully used mine, RX-only, on 630 meters to receive WSPR stations. It will TX there too, pretty cleanly, but a 630m TX antenna and matching network is on next winter's to-do list. I was surprised that the second harmonic was not too bad. I understand a square wave has minimal second harmonics, so I guess this is why. If you have a spectrum analyzer, you could set the radio to the 80m LPF, change the frequency dial to 160m, TX and look at the harmonics. The 80m LPF may catch the 3rd harmonic, if you are lucky. This is just a guess on my part. I think I'll check it out. 73!

[dl6sez]

Hello Guys,

we have a tuned class-E low pass filter which is not a normal lpf as you both think about it!!!
Your Fets do not see the appropriate output impedance on the 80m or other output filter when you use 160m. It can work if you are lucky but is at least much more sensitive to mismatches at the antenna.
Class-E low pass filter is not comparable to a standard 50 Ohm to 50 Ohm lpf!
If you are unlucky you will kill the PA Fets in an instant.....

73 de Chris

[kf7yrs]

I tried the TX part setting the (tr)SDX for 80m and turning the tuning knob down to 1.960 MHz. The SDX display showed 1.4W output during a cw key-down while my Diamond SX-200 SWR/power meter showed 5W output. The Spectrum analyzer results may explain the differences. There were lots of strong harmonics contributing to what the SX-200 measured. Looking at just the 1.960 MHz signal on the analyzer, and considering the 30dB input attenuation, the 1.960 signal was +30 dBm, or about 1W. You will definitely need a 160m LPF, and perhaps an amplifier. I'm new to this radio, so maybe the real experts know better.

[kf7yrs]

Thanks Chris, looks like I have lots more to learn...
Lee

[dl6sez]

Hello OM Lee,

nice SA plot
You can see our (tr)uSDX does a square wave at the output! The square wave signal from the PA FETs is normally transformed into a sinus in the class-E resonant lpf. You see a lpf is a "must have", for every band an extra one

73 de Chris