Centron cm-u tuned input - Page 2

**K9STH** · #11 11-04-2009, 01:01 AM

Make a simple "L" or "Pi" network with a tapped coil so that you can actually tune the input to the amplifier. Record the settings so that you don't have to go through a lengthy process of tuning the network every time that you change bands.

You can make a suitable network for well under $20 and using the network should do away with your problems.

Glen, K9STH

K5FH · #12 11-04-2009, 03:03 AM

Quote:

Originally Posted by KL7AJ

You have to remember that the INIPUT impedance of a grounded grid amp is highly dependent on the load impedance and tuning...as well as DRIVE level, to a certain degree.

That's why I advised using full exciter output power into the amp (full power being that power level recommended by the amp manufacturer) and terminating the amp into a dummy load when adjusting the input tuning. Once you have the amp's tank circuit matched to a noninductive 50-ohm load, the amp's output impedance is no longer a major factor in input tuning. You then do whatever you need to to get a 50-ohm match at the amp's input and you're good to go. It might take a few iterations to find the proper combination of settings but it's worth the effort.

Keeping the antenna matched to 50 ohms helps, too.

The input matching circuit also isolates the exciter from the amp somewhat, so that changes in amp loading should not affect the exciter's output nearly as much as they would with an untuned input on the amp.

W6BDM · #13 11-04-2009, 04:12 PM

As I stated before there are no adjustments in the input box. And I have been tuning up with full power.
BY THE WAY THE HEADER SHOULD STATE: "DENTRON" CM-U, it was a typo. This is a seperate Dentron made matching box for amps without a tuned input. Maybe I should have stated this earlier. I was wondering if anyone knew anything about these boxes. I bought the matching box so I dont have to run an antenna tuner between the clipperton L and the exciter. Anyways, the box is malfunctioning or I am doing something wrong.

W8VVG · #14 11-13-2009, 04:31 PM

I tried a cmu tuned input for my TS930s into the Clipperton L, the TS 930s didn't like it much. I purchased a LGD Z100plus auto tuner cheaper than the cmu. A simple touch of the button and its tuned. Sold the cmu on Ebay and more than paid for the Z100 plus..

W6BDM · #15 11-13-2009, 09:31 PM

Thank you,
I did sell mine also. I did have luck with my ft-101ee. Did not work well with my ts-570. It sold for alot less than what I paid. Thats life I guess. I have recently sold the clipperton anyway, Bought an Amp Supply LK-500zc. That should put out more significant power. And it has tuned inputs!