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Author Topic: dBm vs. dB Loss  (Read 13260 times)
W9IQ
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« Reply #15 on: April 04, 2016, 06:16:57 PM »

Hi Bob,

It sounds like you have your challenges! I never considered you an idiot or any thing close. We all are learning about one thing or another and I simply appreciate it when everyone keeps it civil (as you did) and stays with the topic to help bring it to a successful close. I credit the other posters on this thread for their good guidance as well.

- Glenn W9IQ
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KA5IPF
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« Reply #16 on: April 05, 2016, 07:46:57 AM »

I realize this discussion is about the new fangled Sinclair cans but I know the old DB cans had adjustable loss marked on the cans where the loop was inserted into the can. 0 to 3-4 dB as I remember. The Sinclairs I messed with were the old hybrid ring. Worked great but a PITA
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N8EKT
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Posts: 419




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« Reply #17 on: April 06, 2016, 07:21:13 PM »

Sorry to hear about all the aggrevation you have been put through

The MSF5000 is one of the best repeaters ever made and can operate in RF environments that would totally disable the latest repeaters on the market so you have the right one for your area

And Sinclair makes a good duplexer

We use their UHF versions with great results

It will all be worth it when all your hard work finally pays off and you are already way ahead of most hams and alot of radio shops by having that HP and knowing how to use it








« Last Edit: April 07, 2016, 05:18:02 PM by N8EKT » Logged
AF6D
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« Reply #18 on: April 06, 2016, 11:53:43 PM »

Thank you Mr. Rich! Yes, the MSF IS a great repeater!!! Finding instructions on connecting an external controller has been confusing and not done. We use the internal controller rather than one of several RC-210's that we own. We also have a Angle Linear dual cavity band pass filter that helps numb the 2MHz receive window down to 500KHz on each side. Adding a preamp brings up the already good .25uV sensitivity. I own a couple of Kenwood TK-0750's and they simply don't compare.
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AF6D
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« Reply #19 on: April 25, 2016, 11:28:33 PM »

I would like to thank those that stayed with this rookie long enough to teach me something! Sometimes things don't get through. Once the Sinclair video was shown it made perfect sense. But I don't own a network analyzer so then how do I setup a HP 8924C to tune the same duplexer. I have set it up to tune the input and output. But I don't get to see the insertion loss. When I was told that the 2330e had a tune able insertion loss I now believe that is what was being told to me.
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W1VT
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« Reply #20 on: April 27, 2016, 06:35:21 AM »

You may be able to use an inexpensive cell phone relay to look at two different transfer functions at the same time.

Zack W1VT
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AF6D
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« Reply #21 on: April 27, 2016, 11:30:42 AM »

You may be able to use an inexpensive cell phone relay to look at two different transfer functions at the same time.

Zack W1VT

Thank you, Zack. Can you explain a little more?
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KA5IPF
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« Reply #22 on: May 04, 2016, 11:13:32 AM »

I use the HP8920A to tune cavities. When set up for sweeping a range the scale displayed can either be 1dB or 10dB per vertical division. If I want to measure the insertion loss I set it up to sweep 100kHz at 1dB/div. I then use a barrel connector between the ends of the coax and normalize the 8920. That takes out cable loss. I then hook up the the cavity or cavitys and read the loss directly in dB.

If I want to measure the SWR I use a Return Loss Bridge. It's two different measurement and 2 different setups but not hard to switch back and forth if you save each one and then recall it. Shuffle a few coax jumpers is all.
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AF6D
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« Reply #23 on: Yesterday at 03:46:50 AM »

Wow! Clif, thanks. I am going to have to actually set this up so I can see what you are trying to explain. But you answered the question that I didn't think you were going to. I was going to ask how you were measuring insertion loss. The cavities are tuned properly for input and output but where we're losing it I think and also where my misunderstanding came from is the tunable insertion loss. I believe and I think I've said this here that when I was told that it had tunable insertion loss they meant I could turn the actual cavity elements to get the notch as well as the insertion loss. I have the Sinclair Res-Loc and I'm anxious to actually do this! I have the HP 8924c and the display is a bit different than the little brother that you've got. Right now I wish I had the little brother. This damn big brother weighs 60 pounds!UT
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KA5IPF
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« Reply #24 on: Yesterday at 09:41:06 AM »

I wouldn't call mine the little brother except for size. I've had mine since Nov, 1997 so am kinda familiar with it. It's on 8-10 hrs a day 5 days a week if that says anything about the reliability. I even have the original HP video on operation. Don't have a VHS player any more but have the tape, never watched it. Any questions you can ask or e-mail.
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