They’re not. The problem is a receiver design issue. That is what the linked article discusses. There’s a link to a table of handhelds ranking them in order of performance for this kind of problem.
Always look at the specs… the best hand-helds have double conversion superhet receivers. Any single conversion (inexpensive) model will be terrible on receive… Yes, cheap HT’s work, and I hate to offend the Baofeng crowd (I still have 2 Baofengs myself,) but double conversion wins hands down. Beware that all the big three have single conversion in their less expensive models also, but remember you’re paying the higher price for the better receiver when you get the double conversion model.
Oh dear. All that development work on SDRs has been wasted.
SDR 2 meter HT? Maybe I have missed a product that offers this. Original poster is looking for a “hand-held” that is less susceptible to intermod/overload."
I think amateurs need to remind themselves of what the dial frequency on a radio actually means, and what it does not mean.
It only means the local oscillator is on a frequency that when mixed with the desired signal will produce a signal on the intermediate frequency of the receiver. That’s all it means. (For heterodyne receivers).
For SDRs sampling at 144 mhz, it still only means that the signals on the dial frequency are the ones that will be demodulated correctly.
It does not mean there is any tuned circuit on the desired frequency capable of rejecting all other signals. Often there is only a simple bandpass filter to pass the entire VHF spectrum, or more. It prevents interference by GPS satellites, UHF TV and MF broadcast stations, but not much more.
This is why a high quality bandpass filter between the antenna and radio is so beneficial. It was left out of the cheap HT, so to make that work correctly, you need to add the filter.
The really cheap HTs like Baofeng use the SDR chip as a receiver. Put a strong transmitter nearby, and an SDR becomes deaf.
I mentioned that I use the Icom IC-2A and IC-2AT HTs for SOTA because of their superior rejection of signals away from the frequency on the dial. I work in broadcasting and spend a lot of time at transmitter sites. The Icom IC-2AT (and the Radio Shack HTX-202) are the only HTs that still work perfectly at my most densely populated sites. I’m sure there are other HTs that would work also, but even my VX-2, VX-6, and others don’t. Adding a bandpass filter certainly helps, but it becomes cumbersome compared to just using an HT that doesn’t get overloaded by high power VHF transmitters nearby.
Richard’s point, I’m sure, is that well designed SDRs, single conversion and double conversion radios will all work well, and dismissing any of them on the basis of known poor implementations could potentially eliminate a good (or better) design from your consideration simply due to absolutes.
What Richard failed to realise is this is a ham radio forum. There is no place for shades of grey, even where shades exist.
There is not an SDR chip made yet that has the kind of adjacent channel rejection that a double or triple conversion monoband 2m HT does. So, he was correct.
The SDR chip receivers are horrible at rejecting strong out of band signals simply due to physics. People seem to assume that newer equals better, but it does not. Especially in this case.