Difference in build quality & performance for the "New" Connex 4600 Turbo vs Older

Assuming the same average skill in plant workers exists and the same quality is maintained in the wave solder bath one could assume on average one is no better than the other if one is considering the failure mode most likely, i.e., bad solder joints (given a good antenna system). Assuming they buy almost all parts from the same location again 'build quality' will not differ by much. Meaning you are asking the wrong question. A more important question is the power devices used. Old style used bipolar Toshiba devices in the main chassis to drive Toshiba 2SC2290 finals in the amplifier. They can take far more abuse without harm or developing leakage in the face of harsh conditions typical of average poor performing antenna systems many trucks have. Mosfets also draw more current for a given power output (meaning they run hotter) and fail rapidly when the antenna system has problems. The trouble does not need to be severe for Mosfets to fail, bipolars could run for a long time trouble free with your main effect seen as poor performance in conditions where Mosfets could fail rapidly. Given a high enough SWR even bipolars will fail especially if you often key and talk for long periods. However Mosfets will fail with SWR being not nearly so high as that which will damage a bipolar device. This problem is compounded by the higher current draw in the Mosfet devices. Another consideration is when devices are operated in parallel they should be very closely matched. This is nearly impossible with Mosfets and factories are not going to devote the time to match them.

The capacitance and threshold voltage being the two parameters of greatest importance when trying to get power to balance between several Mosfets in parallel (the design method used to replace those 2SC2290's). The threshold voltage Vt is merely the gate voltage at which the volume density of electrons in the inversion layer is the same as the volume density of holes in the body. The capacitance of the depletion layer is the second parameter one must match. I buy IRF520's (the device used for your 'new' 4600 from driver to final to all devices in the amplifier) hundreds at a time so grabbing a few will give a fair estimate of how well they match on average. Taking 5 new IRF520's at random out of several hundred I measured C and Vt. I measured them at random and listed the five in order of increasing depletion layer capacitance. I did not bother comparing Rds(on) (Drain-Source resistance), or Oxide layer capacitance. Frustrating, the board keeps aligning data to the left so I use - dashes to separate (not to be seen as negative signs).

------1------2-------3-------4------5
C = 838 pF, 842 pF, 922 pF, 940 pF, 1,100 pF
Vt = 3.0 V,--2.9 V,--3.9 V,---3.8 V,--3.9 V

I could have tested 500 of them and the results would be the same, parameters varying quite wildly and I buy only prime devices. I did this with a half dozen ERF2030's and found higher capacitance and deviations of both C, Vt, from similar to worse than the IRF520's. The simple fact is minute variations in doping, purity, deposition thickness to name a few create great deviations in parameters, and C, Vt, are not the only parameters to consider. What this means is no matter how many radios you choose to investigate you will never find one with matched devices. This can cause catastrophic failures in the amplifier (holes in Mosfet body, flame out, etc.) to occur quickly even with an antenna system with only moderate SWR, one where bipolar devices could tolerate without harm over long periods. All dependent upon your operating habits of course. This applies to all models and manufacturers on the market now, not just the Connex 4600 Turbo.

In my opinion nothing beats the Toshiba bipolar devices in these export class radios. I do not really care for the Mosfets at all but they are so cheap get used to them the manufacturers are not going to commission a factory to start building lead containing bipolar RF power devices. As many have discovered the lead free copies built in China are not worth a nickel. I would rather find a used older version 4600 but one also must consider what it has been through and whether or not they are ending up with a can of worms (bad controls, switches, leaky finals, etc.).

 

Seems like no one will 'chime in' anytime soon, the simple answer is the new version uses Mosfets for driver, final, and amplifier. Meaning if you buy one be aware of how critical it is the antenna system is never allowed to be bad even for a very short time. Mosfets cannot take intermittent abuse and survive unscathed in the way the older versions using bipolar devices could.