Thanks so much for your input Nick. It is a pleasure counting with the expertise of one of the creators of this nice rig!
I did some more tests and I think I have a better view now
Just to make sure about them I did one more test.
This time I switched on the rig battery powered, without any antenna, and plugged my studio headphones. I decreased the volume completely and, there you were!, I could clearly hear a low buzz electric noise. I think this is the real reason for these spikes.
No matter the band, neither the mode (I cycled between LSB / CW / Digi…) nor the Filter level (1 to 4), that buzz noise was there the same way all the time. Could it be it is not a Filter issue but maybe something defective in my specimen (Serial number 0202) in the audio stage perhaps?
I measured again the spectrum to check the floor noise (radio off) then the spikes with zero volume , and again the spikes when receiving at medium volume level:
(Spectrum from 0 - 1000 Hz shown)
Maybe the rig you have doesn’t have this issue and it is only present in my part? Just check yours with headphones and zero volume and see if you can hear the buzz noise…
I am sure that if I hadn’t plot the audio spectrum I would never have noticed about the spikes because it level is low. For sure, when you use the rig, the breeze on the countryside or even operating at home you will never tell about them, so the receiver works fine for me.
I do find there is room for improvement there. I don’t have any issue when working with a proper 50 ohm antenna but if I use a simple antenna in the countryside and switch between CW section and SSB section in a band, I can expect a SWR variation. Moreover, when working with a simple piece of wire even if it is a resonant antenna as it is the case for me.
The problem here is the excessive reduction you will get from the rig because it reads a too high value when it is not the real value present in the antenna (i.e., the rig reads 7:1 SWR and reduces power to 1,5 watt output while it is 4:1 SWR present in reality).
I agree that if you have a proper antenna with a decent bandwidth you won’t have any problem with this rig and the LD-5 probed to be effective in the default 50 ohm range.
The point is that if I have a value indicated on the Display, I would rather prefer to have a proper measurement. Is it something you could improve on a firmware update, maybe?
I am not fan of them and have not testesd on my specimen. Probably they will work fine with a proper setup.
Again, thanks Nick for your words, and I keep saying it is a very valuable little rig which works fine for me, even having these minor bugs. I just opened the door for some improvements that would increase even more its value in the market.
73 de Ignacio
P.s: I didn’t mention in my review it is possible to get the 11 band version of this rig here in Europe, called Sky-Sdr.