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Are you new to 1500 watts power?

Mike-VA3MWMike-VA3MW FlexRadio Employee, Community Manager admin
edited June 11 in New Ideas
I wanted to share a story especially if you are about to run some real 'full' power.

On my home station, my 6M beam is on the roof on a small roof tower.  It has been up there for 10 years.  This week, I have roofers coming in and therefore the beam and tower had to come down.

For a while, I've felt that in my gut, the 6M beam wasn't working as well as it should.  SWR looked fine.  Return loss looked great. 

The 2:1 SWR beamwidth looked AMAZING!  Almost flat across the band.

Errr... No --- that is always good news.  Antennas that are flat across the band are dummy loads.  I know this and preach it and didn't listen to my own head (and test equipment).

The 'ah ha' moment was when I undid 1 connector on the feedline to the 6M beam.  It was full of water (hence the flat bandwidth).   The water absorbed the RF energy and there was less to return for reflected SWR.

This connection was done correctly with waterproofing tape (the soft flexy stuff -- can't remember the name) and then taped up with 3M Scotch Light (forgot the number, but the right stuff).  Yes, a third layer would have helped.

I was just about to the point to hit this antenna with 1500 watts in the coming days until the new roof had to happen.  Amplifier integration to the 6600 on hold.

The moral of my story is that if you are waiting for your PGXL you may want to open every and all connectors in your feedlines and inspect them.  Especially if it has been years.   Most will be ok.  A few won't be.  If you call in with this problem, Tim and Neal are going to ask you to test it on a dummy load.  Be prepared and it will give you some piece of mind.

The PGXL can shut down in 250ns (that nano seconds).  Light travels only 250ft in 250ns (approximately).  That is super fast.  So, if your antennas throw up some brief bad SWR for a short moment, the PGXL will detect it.  No other amp is this fast and has this kind of protection. 

Very awesome stuff.  

For most of you, it is summer.  Time to do some coax maintenance.  

Mike va3mw



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Comments

  • AC9SAC9S Member ✭✭
    edited June 2018
    Yep - Another thing you can do is to physically grab each connector in the high power chain - once you have run an HP amp for a while.  Some connectors might be warm or even hot - good candidates to redo.

    Keith - AC9S
  • roger na4rrroger na4rr Member
    edited June 11
    That,s I have new 2K-FA Expert amp on the way.  To go with it,  New LMR-600, 2  New jk-65 antennas.Stack Match II .  Look for me on 6M
  • David Decoons, wo2xDavid Decoons, wo2x Member ✭✭✭
    edited June 2018
    Wow. Nice antenna setup you have planned.
  • KY6LA_HowardKY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited June 2018
    Canadian winters strike again. Hi Hi
  • Kari Gustafsson SM0HRPKari Gustafsson SM0HRP Member ✭✭
    edited January 2019
    So true Mike. We service HF amplifiers and a couple of service repairs every now and then for $150 find nothing wrong with the amplifier. It is often faulty coax connectors, baluns, cables etc. Even if the customer intially "guarantees" that his antenna is 100 % ok.
  • K1UO - LarryK1UO - Larry Member ✭✭
    edited June 2018
    Roger... I have a single JK65 going up this weekend...what spacing for a second would you recommend?  Just wondering if my 1/2 in thick aluminum 2 inch mast is log enough :)
  • Logan KE7AZLogan KE7AZ Member ✭✭
    edited June 2019
    I read an article awhile back about a ham who made up several test connections - coax pl259 barrel pl259 coax. He used the various sealing techniques and put all of the junctions underwater and let them soak. At the end of the test, he found that all techniques leaked, eventually. What kept things dry was the silicone grease that he put in one of the test samples during assembly.
  • Frank  WA3NHKFrank WA3NHK Member
    edited June 2018
    Logan.....Actual silicone grease or RTV?   Just curious. 
  • roger na4rrroger na4rr Member
    edited June 2018
    Array Solutions said 15 feet
  • Logan KE7AZLogan KE7AZ Member ✭✭
    edited June 2018
    It was a grease. HRO sells a product called Stuf. You put it in the connectors and mate them. The metal to metal contact points displace the grease and reminder fills all of the gaps. The last technician to work on my copper landline used something like it on the connections in my network interface box.
  • Frank  WA3NHKFrank WA3NHK Member
    edited June 2018
    tnx.
  • Neal - K3NCNeal - K3NC Inactive Employee
    edited June 2018
    The K3NC motto on equipment failure is that 'its always the cheapest part'. Always is a very strong word but I have sent 80lb amplifiers to be serviced for problems only to discover my ptt cable had a short in it. Did same thing with ring rotor motor 10 years ago, open control cable. I guess we always worry that the most expensive thing to repair is the cause so start debugging with that in mind. Sometimes it helps to take a break and go cheap!

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