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Thread: Source for RF cables for Synrad 60-1?

  1. #1
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    Default Source for RF cables for Synrad 60-1?

    I recently picked up a huge lot of surplus lasers from the Savannah River Site including a SpectraPhysics GCR-200, a couple of Synrad 60-1’s and some Spectra Diode Labs diodes & drivers. I would like to get the Synrads sorted out first but the cables were not included with the lot. I talked to PhotoVac Laser, and while they have offered me some interesting options, I would really like to see if they work at all before I start throwing tons of money at them. The one part I really need advice on is the RF coax cables. The service manual specifies “5 meter (1/2 wave) RG-8 Foam 50 ohm”. PhotoVac’s price for the cables is just under $900.00, so I was wondering; could I order a set from a Ham radio supplier just to see if these things fire or not? Something along these lines?

    https://www.pasternack.com/n-male-n-...-pe3570-p.aspx

    Any advice/input is greatly appreciated!

    -Brian

  2. #2
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    We have found out the hard way that the protective VSWR monitor circuit on many of these RF driven lasers wants to see an exact multiple of half waves and a precise impedance in the cable. You can either 1. Pay for the commercial cable trimmed as needed, 2. Obtain a cable with a known velocity Factor coefficient, calculate the needed corrections for the frequency in use, cut the cable slightly long (1/8TH wave long) and install, reinstall the connectors till your trimmed correctly. 3. You can obtain or borrow a vector network analyzer and do it the right way.

    Pasternak is generally viewed as expensive, but they might have the VNA to do the job.

    First thing I would to is try a short cable, say less that two meters in length and 50 Ohms impedance and see if the system does not fault and does lase. If that is the case leave it be.

    DX Engineering sells RG-8 and completed cables.

    Steve
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  3. #3
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    Thanks so much for the reply. I just finished reading through the thread about cable lengths for the Coherent GEM which led me to pretty much the same conclusion. So, I just ordered cable, connectors & a NanoVNA. <$200.00 and I get to learn something new. Win/win.

  4. #4
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
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    I have an original model Nano. Ok for 150 Mhz and below. I'm not impressed, but at the lower frequency ranges it does the job. Have fun.

    Steve
    Qui habet Christos, habet Vitam!
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