Re: QCX for 2m VHF? #chat #qcx #vhf #mods


Jim Allyn - N7JA
 

On Mon, Feb 8, 2021 at 09:51 AM, Jim Mcilroy wrote:
I must confess that I assumed that most hams would know the distinct differences between HF and VHF design and construction.
I don't know why you would assume that.  Clearly the original poster didn't know the differences between HF and VHF design and construction, else he wouldn't have asked, "Would the QCX design not be able to make an VHF version?"  Maybe things are different where you live, but here in the United States, it seems to me that a significant number of hams, perhaps a majority, don't know the difference between HF and VHF.  I have heard lots of US hams admit that they know basically nothing: in their own words, they just memorized enough questions and answers to pass the test, then promptly forgot everything.  An example of how much some hams here (don't) know:  within the last year or so, I heard a discussion on one of the local repeaters about baluns.  One of the guys wanted to know what kind of balun he needed: "I see there are one to one baluns, and four to one baluns, and nine to one baluns.  How do I know which one I need?"  The answer he received was, "If you want to operate on one band, you need a one to one balun.  If you want to operate on four bands, you need a four to one balun.  If you want to operate on nine bands, you need a nine to one balun."  I looked up the gentleman who gave that answer on QRZ.com, and he holds an Extra Class license.  I'll leave it to you to consider whether that gentleman is likely to know much about the differences between HF and VHF design and construction.

On the other hand, one could argue that there is no difference between HF and VHF design and construction.  The principles are the same: keep all component leads and signal paths as short as possible, minimize the loop area circumscribed by the signal paths and their return paths, keep different types of signals (analog and digital, for example) away from each other, ensure that bypass capacitors have a low impedance at the design frequency, and so on.  The differences are in the details.  Practically speaking, an inch of wire doesn't exist in a circuit designed for 80 meters, at 70 centimeters that same piece of wire is a fairly large inductor.

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