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Author Topic: TPL Communications PA3 HMS Conversion  (Read 1946 times)
KC2TX
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Posts: 5




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« on: January 30, 2012, 11:40:22 AM »

I purchased TPL Communications PA3-166-HMS amplifier a while back with the idea of using it for 144 mhz MS and possibly low power eme. I talked with TPL and they said the amp is about 12 years old and can be converted to 144. ( it will work 5mhz either side of 155.910 without modification. ) However it will cost me $90 and hour to do so. I've looked all over the web for conversion info and can't find any. Has anyone converted one of these amps ? And if you have, how was it done ?
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K6AER
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« Reply #1 on: February 01, 2012, 02:17:46 PM »

These amps were used for 500 watt FM paging. They are class C. It will take a lot of biasing to get the IMD and relibility to a decent level and you will be lucky to get 250 watts out in SSB mode. The devices were neve made for linear operation.

Frequency responce will be the least of your problems.
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WB2WIK
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« Reply #2 on: February 01, 2012, 08:06:05 PM »

I agree.  They're not linear.

However if you want to work MS on CW, that would be fine, and just do it.

For SSB or WSJT modes, nope.
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KC2TX
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« Reply #3 on: February 02, 2012, 05:01:13 PM »

Thanks for the info. I had planned to use wsjt, but as stated, the amp isn't designed for linear service. I guess I bought too quickly. Again, thanks for the info.

Spencer KC2TX
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WB3BEL
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« Reply #4 on: February 03, 2012, 07:39:19 AM »

WSJT is constant envelope modulation so class C should not be an issue.

If you have some pictures or schematic showing the amp internals that you could share, it probably is just a matter of adjusting a few variable capacitors while observing the output power, gain and input match while the amp is terminated into a dummy load.

Also keep an eye on the power supply current to avoid excessive current and maybe estimate the efficiency when you are all done.

It's worth a try...
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KC2TX
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« Reply #5 on: February 04, 2012, 05:19:57 PM »

Hi,
I can send pics to your email address or post them to a web site. The power supply shouldn't be a problem.,I have a switching 12v 100 amp power supply. I had planned on using the PA3 strictly for wsjt eme. THANK YOU for your help, it is greatly appreciated.
73
Spencer KC2TX
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