Cheap Amateur Handhelds

Discussion in 'Electronics & Electrics' started by @rt, Feb 14, 2014.

  1. ipex

    ipex Member

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    that was one of my dads first rigs when he got licenced back in the 80's , sold it off , then got given another frg from a ham friend , it now sits in my shack along with the ft7 , and and ft 747
     
  2. OP
    OP
    @rt

    @rt Member

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    Yeah I am looking for one of it's matching transceiver Brothers with valve RF section.

    I'm going for scabby F call so I think VK4FART is out of the question even though it's available.
     
  3. stewpot

    stewpot Member

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    Here it is: http://www.qsl.net/vk4ba/barcfest/
     
  4. OP
    OP
    @rt

    @rt Member

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    Yeah I've sussed it out.. Shhh! no need to tell everyone :D

    The three of us passed, looks like I'll be VK4FAST, next it's VK4FPIC.

    Just one question, what's the difference between these two:
    RF power amp output on a transmission line
    [​IMG]
    AC current travelling on a wire
    [​IMG]
     
  5. Symon

    Symon Castigat ridendo mores

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    Hmm... almost makes me want to get my licence renewed, I haven't used it in years. Looks like it is still available too - VK4YSB.
     
  6. RobRoySyd

    RobRoySyd Member

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    Nothing. A wire can be seen as a transmission line.
     
  7. LINUX

    LINUX Member

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    The difference is scale. It's true that a wire is a transmission line, however transmission line effects (transport delay, reflections, SWR etc) are only significant* when the transmission line is appreciably long compared to the physical wavelength of the AC energy. So ~1km of 240V cable can be compared to ~6mm of cable carrying a 7MHz signal in that the length of the wire is an equal proportion of the wavelength.

    Rules of thumb vary, but it is often said that if a wire/PCB trace/coax cable is less than 1/10th of a wavelength long then transmission line effects can be ignored (but they still exist!)

    *What is "significant" is application dependent.
     
    Last edited: Apr 27, 2014
  8. OP
    OP
    @rt

    @rt Member

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    Sorry forgot about this... I really mean what is the difference between RF energy, and AC current?
    and if there's no difference, why are they referred to differently?

    I went to hamfest on the weekend and got the star of the Foundation manual.. Icom IC-718 :)
    as well as some other parts, and a Yaesu FT-620 (6 meter) that I can't Tx with yet,
    but cheap, already fixed it's problem, and collectable :)
    Bad caps in the AC supply were making it squeal and hum,
    but powering it directly with 13.8 V DC cures the problem without even changing them.

    Among other goodies... a small CRT, and a magic eye tube with it's socket.
     
  9. RobRoySyd

    RobRoySyd Member

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    "RF energy" refers to electromagnetic energy.
    "AC current" refers to the flow of alternating current in a conductor.
     
  10. D_Web

    D_Web Member

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    Ah, so you were the one I saw walking out with the IC-718 box :)

    Wonder if any other OCAU'ers were at BARCFest.
     
  11. OP
    OP
    @rt

    @rt Member

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    That does sound right, it was in it's box (from VK4ICE) :)

    On my way out with that box I thought I'd better grab the brass morse key when I get back in,
    and then when I got back it was gone :mad:
     
  12. OP
    OP
    @rt

    @rt Member

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    Thanks :)
    At what point does that conversion from current, either AC or DC, to RF happen?
    In a final transistor or valve, is it just because a large current is being switched?
     
  13. RobRoySyd

    RobRoySyd Member

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    When it reaches an aerial.


    Consider this.
    You connect a length of 50ohm coax to an electrical generator at one end and to a 50ohm resistor at the other end. You set the generator to generate DC. The electrical energy is converted to thermal energy (heat) by the resistor.

    You change the electrical generator to 50Hz AC. The same thing happens.

    You increase the frequency of the generator to 1MHz, the same thing happens.

    Here we're just considering electrical energy (motion of electrons) and its conversion to thermal energy.

    Replace the resistor with an aerial. Depending on the physical design of the aerial electromagnetic waves will radiate from the aerial into space, in fact possibly to the very end of space, through a vacuum. The AC energy is converted into RF energy (motion of photons).

    That's a very crude example but it's good enough to give a vast set of equations that describe what happens.
     
  14. LINUX

    LINUX Member

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    I'd argue that it depends on who you ask, because the idea of "RF energy" vs "AC energy" isn't well defined. At one level they're the same thing (they're both oscillating electric fields in a wire, causing electrons to move and energy to flow) but are used by different people in different contexts.

    If you ask an engineer who works in the power industry they will only talk about AC power/energy/etc while an engineer who works on radios will only talk about RF power/energy/etc.

    Once AC/RF energy is converted to photons via an antenna it becomes electromagnetic radiation, however the frequency/wavelength of the radiation will dictate how it is described. Typically "RF" only refers to EMR which can be modulated/transmitted/received/demodulated (ie: which can be controlled to transmit information). For example nobody calls X-Rays or 50Hz noise "RF energy" despite them being forms of EMR.
     
  15. OP
    OP
    @rt

    @rt Member

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    Thanks for the explanation.
    What might have confused me is the fact that components inside transmitters
    being referred to as "RF amplifiers", etc.
     
  16. 2xCPU

    2xCPU Member

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    AC doesn't 'convert' to RF. It's all the same thing.
    Eg. 15kHz may be AC inside an inverter, it may be AF in your amp or it may be RF (VLF) for long distance communication.
    15kHz can be transmitted via a wire, a loudspeaker or an antenna.

    Similarly, HF is 3~30 MHz
    VHF is 30~300MHz
    UHF is 300~3000MHz
    etc.
    It doesn't mean one is different, just names of convenience.

    2.
     
  17. vk2fro

    vk2fro Member

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    It'd have to be a pretty darn long wire to tx 15 khz :)

    I have one of these baofengs as well. good little hand helds - I set mine up to tx only on amateur bands using chirp, as I have no use for uhf CB or transmitting where I shouldn't. Mine came with two batteries, one the same size as the radio, and another twice its size, which allows it to run in RX for ages before it shuts off. it also came with a horrid prolific based programming cable which I cant find in my junk box. they're a pain to install. Drivers can be tricky to find.

    I mainly use mine for camping trips, or at home, where I'll put my yaesu FTM-350A/R into xband repeat, and talk with my friends on simplex (we have decided on a simplex frequency which we share with another group), and set the hand held to 440ish mhz. That way I can talk and listen around the house without being tied to the radio desk.

    basically it turns a 5w uhf hand held (which also does vhf) into a 50 W vhf handheld. All I have to remember to do is identify "VK2FRO with <other callsigns> via 439mhz crossband repeater" :)

    For HF I picked up a "broken" icom 746pro, which simply needed a couple of parts replaced to fix the issue of no output power. An smd hot air gun is invaluable here, along with a good magnifier! I now have a second one on my bench (a friends) which blew up its vhf section. I'm now pretty familiar with its PA board so he gave it to me to fix, and loaned me a VHF power/swr meter to test it with, which in itself was loaded with dry solder joints! fix that one pretty quick :)
     
  18. OP
    OP
    @rt

    @rt Member

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    I just ordered an LDG IC-100 auto tuner.. One of the clones of an original Icom tuner
    that is still controlled by the tuner button on the radio, so I hope that's good!

    Now I really think it's only down to an antenna before I can transmit on HF ! :)
     
  19. vk2fro

    vk2fro Member

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    Yes those LDG tuners are wicked little boxes - I used to have one a while back when I had the icom 7000 - you'd hit the tune button on the radio, and the tuner would do it thing, then light up an LED or series of LED's in sequence (depending on the model - I had the AT100pro), to indicate it had or had not made a match. Then you could go ahead and TX (or set the antenna switch to the correct antenna LOL) :)

    Just be ready for that first tune cycle - they make a racket like an old fashioned pinball machine or mechanical adding machine without the bells, but once they've stored your most used frequencies, they're very quiet and quick.

    Another thing is, you don't even need to push the rigs tune button (but I did it out of habit for respect to the finals of my radio). You just key up on the working frequency and the tuner would go "click" and lock on as soon as you talk or as soon as you key up in fm, CW or other constant carrier modes)

    Anyway back on topic - spot the baofeng :) (no need to guess, its dead obvious LOL!)
    [​IMG]
     
    Last edited: May 15, 2014
  20. OP
    OP
    @rt

    @rt Member

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    The Baofeng I can't really fault them, they are handy,
    and for plastic junk they are made so well, but I hate them so much!

    I still haven't gotten round to the better eBay antenna and extra battery,
    but I would like one of those that take a number of AA cells to standardise things.

    Is that an antenna straight to the right of the Baofeng?
     

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