Modern radios

Discussion in 'Amplitude Modulation' started by N2DTS, Nov 21, 2019.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    I would say an SDR receiver is much better at most things then something like an R390a.
    The Flex 6300 is a poor example, its well down the list and well below the old Flex 5000!

    A good SDR will have the noise level of the actual receiver much lower then the R390a, and lots more ability to set filters where you want.

    The idea that you will not be able to repair a modern radio is somewhat true, while you CAN work on them and repair them, some parts may
    not be made in 10 years and out of stock in 20.
    But its much more likely anything that runs on a computer will be useless as computers will look much different in even 10 years.
    Another advantage of modern gear over old gear is its much more stable.
    Buy a new SDR and chances are you could use it for 10 or 20 years without having to do anything to it, as many have with the old Flex 1000.
    The old R390 and DX100 will break a gear clamp, blow its mod iron, melt a 1625, blow its ballast tube, have that cap protecting the filters short out, and mechanical filters and PTO's do wear out!
    So you are going to have to fix the old stuff, maybe a lot.

    I like both old tube gear and modern gear, one is not better then the other overall, just different.

    At the moment, the best performing receiver you can buy is an sdr.
  2. AI5DH

    AI5DH Ham Member QRZ Page

    There is no difference between working on an SDR radio and modern conventional radio. Other than minor repairs, you cannot work on either of them. Bench technician jobs were gone with the 80's and DOA. So no your argument is not valid. SDR radios can run circles around conventional radio. Commercial and Industry use only the best.
    KA0HCP likes this.
  3. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    In terms of technology the SDR-based radios seem to have these advantages for AM:

    1) user programmability in terms of transmit and receive bandwidths,
    2) wide receiver coverage
    3) firmware uploads allow new features and improvements as technology progresses because of its flexible architecture.


    1) Currently low power transmit for all but the more expensive units, so an extra Linear Amplifier is almost a given,
    2) Initial cost is high but as more companies get on board and technology improves, prices will come down,
    3) Cannot self repair due to SMT devices and proprietary software and firmware (FPGA's, etc).
    4) Because of 3), the operator cannot experiment with or know anything about the internal workings of the rig and therefore learns little about communications electronics. Of course, the same comments apply to modern non-SDR transceivers.

    Last edited: Dec 3, 2019
    K5UJ likes this.
  4. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    ...which is changing the whole nature of amateur radio, and not for the better. Historically, one of the attractions of AR has been the opportunity to tinker, reverse-engineer, build from scratch, modify and repair transmitters, receivers and their associated equipment. As amateur equipment moves further in the direction of the hermetically sealed box on which the owner is not supposed to break the seal, or which is potted in a block of epoxy to prevent access, AR is becoming just another branch of the consumer appliance industry. Even if the owner breaks the seal and opens the box, what he finds inside is all but impossible to work on, filled with undocumented proprietary chips, modules and surface-mount components. Working on a modern radio is about like trying to repair or modify the mother board in a modern computer without a schematic or technical documentation. I have very little interest in a piece of radio equipment that I can't repair or modify, and to me, appliance operating is boor-ing.

    Even simple appliances like small room space heaters are built to prevent access to the owner to repair them. First of all, the case is often put together like a puzzle, very difficult to figure out how to open it without breaking off some little plastic tab that holds the whole thing together, and using one my pet peeves, "tamper-proof" screws that require a special driver to turn. I have managed to accumulate a pretty good supply of those special drivers, but almost every time I try to service a new piece of consumer junk, I end up needing a new type of special driver that I don't have. Last year we had two small bathroom heaters crap out right about the same time. Instead of throwing them out and buying new ones like a good consumer (I hate that word) would, I found the requisite drivers on line and was able to non-destructively open the case. All I had to do to fix one was simply to clean out the lint that was clogging up the radiating fins on the heating element. The other one, I had to modify the plastic bracket that was holding the fan and heating element in place; the plastic had warped from the heat from normal usage and the blades wouldn't turn, causing the temperature to rise and trip the little over-heat protector module. After sawing and filing on the bracket to free up the fan and then cutting away unnecessary plastic in the hot air flow path that was causing it to warp in the first place, I put it back together and it has worked flawlessly ever since.

    I used to go after old TVs in the junk pile and dismantle them for parts, but lately TVs haven't produced anything worth salvaging. Last time, I had to bust open the case with a hammer because no matter what, I couldn't figure out how to open the case any other way. Once I got it open, there was a CRT (yes, one of the last TVs with a picture tube) and a small circuit board with nothing of enough value to make it worthwhile to salvage. I did salvage a good power cord, a spool of copper wire from the deflection coil, and a few pieces of plastic-covered hook-up wire, but that was all.

    OTOH, I recently studied and figured out how to dis-assemble the PTO in one of my 75A-4s. I took it apart, cleaned it, replaced a questionable ball bearing with another one salvaged from a junked PTO found at a hamfest, re-lubricated it, and re-assembled it. I took care to note exactly how all the little pieces are assembled and precautions to avoid losing any of them, but the greatest challenge was to fabricate a fixture to allow me to compress the spring in the shaft/bearing assembly far enough to expose the groove in the shaft and allow the e-clip over the front bearing to snap back in place. It now works OK mechanically and electrically, but I still need to do some electrical work on it to allow correction of a calibration error before re-installing it in the receiver. Although it's not rocket science, most owners of Collins receivers and other equipment won't dare attempt to repair a Collins PTO.

    My 75A4 receivers are now 60 years old, and I still use them. I wonder how many pieces of "modern equipment" will still be running and in use 60 years from now? All it takes is for one $2 unobtanium proprietary IC chip to crap out, and you have an expensive door stop. Most modern radios are full of proprietary components, which may be "discontinued" in less than 5 years.
    KW6LA, K0OKS, K5UJ and 1 other person like this.
  5. WW2PT

    WW2PT Ham Member QRZ Page

    One can say the same thing about cars! Wait until all these fancy dashboard touchscreen displays start failing in 20 years (or less) and there are no longer replacement parts being made.
    K4KYV likes this.
  6. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    The reconfigurability of SDR is found in the programmable Digital Signal Processors (DSP's) and in the programmable General Purpose Processors (GPP's).

    Most SDR radios employ IF sampling to do more signal processing in the digital domain.

    So what details do A/D IC manufacturers need to work out?


  7. N2DTS

    N2DTS Ham Member QRZ Page

    Well, its just different, look at what Chris did with the mcHF sdr radio he designed and built and offered as a kit!

    And he is still at it.
    Flex radio started as an experiment by a ham, and look at that stuff now.

    Most of the HPSDR stuff (Anan radios) is a group effort by hams, all cutting edge.
    And here we are fooling with old tubes, cutting edge stuff from 50 or 75 years ago....

    You can say ham radio is going to the dogs because many hams do not know how to build a push pull 100TH rig?
    When your car wears out and you can no longer get a piston for it, maybe go back to horse and buggy, you can always get parts for that.

    I suppose its nice and fun having a horse and buggy, but its going to be rough going to Florida in it for the winter...
    KA0HCP likes this.
  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    And suppose you do have the schematic for the modern transceiver, the expertise, and you have an extensive set of instrumentation to find the failed IC. Now attempt to remove that SMD component with pin spacing of 0.5mm to 1.4 mm without creating solder bridges. You will find that a special temp controlled soldering iron and tip is required along with a good microscope or magnifying lens is required.

    That's why they make

    and this

    in order to work on modern electronic equipment.

    In addition, the extensive set of instrumentation has to also include an expensive multi-channel Digital Oscilloscope and the list goes on.

    Most ARS operators don't have the expertise nor the budget to repair modern transceivers.

    K5UJ likes this.
  9. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    No, I think most people are saying is that as you move toward SMD-device based transceivers and SDR's, you move away from being able to experiment and the ability to learn about the inner workings of that rig.

    "mcHF Kit

    It took some two years to the moment i can offer the mcHF in kit form. It consists of two boards with populated SMD parts and extra components supplied in plastic bags. The kit does not include speaker, final MOSFETs and enclosure.

    It is worth pointing out that the kit requires some advanced soldering skills and knowledge in electronics as mods might be required. Also extensive tuning and calibration might be needed, or sometimes debugging of problems. It is not recommended as first kit or if you expect to be on the air after few M3 bolts tightening."


  10. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    While I generally agree with your premise there is one mitigating factor in today's "just replace it" economy. The 75A4 cost $695 in 1958. Adjusted for inflation that's over $6k today. You fixed the old ones not only because you COULD but because you had to. With the rise of transceivers there's not really something directly comparable today as the dongle based SDR receivers don't really compare. But you could buy two medium line full transceivers (IC-7610, FTDX-101D, TS-890S) for the price of one of those receivers only, or maybe ten low end transceivers that also have general coverage receive capability. So you can't fix them kind of don't need to as badly either.

    Note that my AM position is a DX-100 and Mohawk. :) I certainly see the charm in the old stuff.
    KA0HCP likes this.

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