Lab Tests are interesting but there is no better test of a receiver's front-end than to use it on a good antenna at a BIG Multi-Multi Contest Station during  a major contest.

The ALT-512 was designed and built in Bulgaria, so the logical thing to do was test it on-site at LZ9W during the 2018 CQWW DX CW Contest.

As seen in the photo above, LZ9W is a very BIG Multi-Multi Contest site.

It has won several big contest in the past.  During a contest, at any one time there is a lot of RF in the air surrounding their site!

During the CW contest, a couple of OM took an ALT-512 on-site on Sunday afternoon, about 11:00 GMT.  They connected the ALT-512 to a 40m monoband Yagi antenna, about 30m high.  The ALT-512 was used to make a few contacts, and then it was compared to a second radio, an ICOM IC-7600.

At this time, LZ9W had 6 stations simultaneously on the air,

operating full legal power

in the CW portion of all 6 hf contest bands.

Theyoperated the ALT-512 in the SSB portion of the 40m band using just the antenna, and no external bandpass filters.

RESULTS:  ALT-512 (+ External 300 Watt Amplifier)

• They worked a JA station, no problem.  
• They worked a W station, no problem.

During the QSO, the radio performed as it should.

Results:  ICOM IC-7600 (100 Watts SSB)

• No QSO possible, due to receiver front-end overload

CONCLUSION

The front-end of the ALT-512 is very Crunch-Proof.

There are very few other radios, regardless of price,

than can be used in this sort of environment without

crunching.