Oscilloscope for ham radio work

Discussion in 'General Technical Questions and Answers' started by KB3PXR, Jan 2, 2008.

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  1. KB3PXR

    KB3PXR Ham Member QRZ Page

    If I were to purchase an oscilloscope for ham radio work, what would the minimum bandwidth recommended for the job? I'm looking around on eBay and I need an idea of how much bandwidth I need.
     
  2. KC6TOA

    KC6TOA Ham Member QRZ Page

    depends on what "ham radio work" means.

    If you only want to view audio signals, they any old scope will do.
    But if you want to view RF signals directly, then you want a scope with a bandwidth rating which is at least double the maximum radio frequency you want to view.
    Digital scopes need to sample at a rate at least 5x the max frequency you want to view.  Analog scopes only have a bandwidth rating, but with digital units the "MSPS" rating is most important.  The faster you go, the more expensive.
     
  3. KB3PXR

    KB3PXR Ham Member QRZ Page

    Ok, a second question is in order. How often do you have to look at the RF signal directly? I'm looking at a 10 MHz model right now.
     
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

    Hi.

    I have a Heathkit monitor scope (positively ancient) that I always have in line. Monitor scopes are a bit of an odd breed in o'scope land because they achieve their relatively high bandwidth by bypassing the vertical amplifiers altogether...you apply the R.F. sample right to the vertical deflection plates.

    Another way of using a cheap scope for monitoring R.F. is with an R.F. downconverter...these projects used to be quite popular.

    Eric
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    When 150 MHz scopes are so common and inexpensive, why bother with a 10 MHz scope?

    A "lab quality" 10 MHz scope like Tektronix or HP would have to be at least 50 years old, because they haven't made such narrow bandwidth scopes in about that long...

    I'd shoot for a Tek 465 or similar. They're all over the place and not expensive.

    I'd also shoot for a "local deal" and not something somebody has to ship to me, since again, these are not the slightest bit rare and it would make sense to see it, try it out, become familiar with it and then buy it after doing those things.

    Scopes are easily damaged in shipment, especially the CRT models which will represent most of the lower-cost market.

    WB2WIK/6
     
  6. Guest

    Guest Guest

    For an accurate view of the RF waveform I always want a scope that can display up to the third harmonic, but this is being pretty picky. There are a number of 100 MHz scopes on the used market such as the Techtronics 465 which work great for frequencies of 30 MHz and below.

    73,

    Frank [​IMG]
     
  7. KB3PXR

    KB3PXR Ham Member QRZ Page

    I have a limited budget here. The <a href="http://cgi.ebay.com/NEW-10-MHZ-MINI-ANALOG-OSCILLOSCOPE_W0QQitemZ280187781937QQihZ018QQcategoryZ104247QQssPage
    NameZWDVWQQrdZ1QQcmdZViewItem" target="_blank">10 MHz Model</a> I'm looking at is $150 buy it now on eBay.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That's a portable scope intended for diagnosing automotive issues. It's not a high quality scope at all, but the good news is you can buy it brand new for that price -- and I think the one being sold on eBay is &quot;new.&quot;

    A used Tek 465, which is a 150 MHz, dual trace, triggered sweep scope of very high quality, can be found for the same $150, although it will be 20 years old.

    I paid $125 for my last one, at a garage sale two blocks from my home. It was in &quot;perfect&quot; condition, with the carry case and manual, and two probes.

    WB2WIK/6
     
  9. K8ERV

    K8ERV Ham Member QRZ Page

    Several years ago I got a like-new Tenma 40meg scope for $85 delivered, deal of the year. One thing that is not often mentioned is that the accelerating voltage (the very high voltage that pushes the electron in the general direction of the screen) usually goes up in the higher-freq scopes. This gives a sharper and brighter trace even at the lower freqs.

    Had the opportunity to compare a 20 MHz sine wave on very similar Tenma 20 and 40 MHz scopes. The trace was dim and fuzzy on the 20, great on the 40. So the higher-freq scopes may be better than just displaying faster signals.

    As has been indicated, there is a big division depending if you want to directly display audio+ signals, and RF signals. And don't forget that you can use a detector probe to see the modulation on an RF signal.

    Be patient, there are some good deals out there.

    TOM K8ERV Montrose Colo
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    And they're usually not on eBay.

    Remember eBay is a worldwide auction, so prices there are usually higher than anywhere else.

    I have often found test equipment brand new at local retail stores for less than the same gear &quot;used&quot; on eBay.

    Really makes me wonder why anyone would pay that kind of price; guess they just don't know!

    WB2WIK/6
     
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