PSK on TRX1

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PSK on TRX1

Postby WB4HLX » 22 Feb 2013 22:25

I have a TRX-1 on the way and would like to know if it is ok to run psk and other digital modes. The person I got the trx-1 from said that would be hard on the finals.

Thanks & 73
Larry
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Re: PSK on TRX1

Postby 5B4AIY » 26 Feb 2013 16:44

Hi, Larry,
The TRX-1 PA uses the IRFR110 power MOSFETS, and these are fairly rugged devices. When mounted on a PCB, as they are in this case, the maximum disspation is limited to 2.5W. Assuming an overall DC to RF efficiency of 50%, fairly typical for small solid-state amplifiers, then with 10W DC in and 5W RF out each device will be at its maximum dissipation.

Under SSB service the typical peak to average ratio is of the order of about 5:1 so the amplifier will operate fairly cool in this mode at 5W PEP O/P. When operating CW the duty cycle is significantly higher, and in this mode it would be around 50%, so, although the output stage will operate hotter than with SSB, it is still within the maximum ratings of the MOSFETS.

Not so with RTTY/PSK31. These modes use a 100% duty cycle, and in this case in order to keep the dissipation and temperature down you would have to run the amplifier at no more than about 2W output. Providing you observe this derating, then you should not have any problem.

73, Adrian, 5B4AIY
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Re: PSK on TRX1

Postby WB4HLX » 20 Apr 2013 08:27

Thank you.

73
Larry
WB4HLX
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Re: PSK on TRX1

Postby VE3GSO » 25 Apr 2013 00:59

The FET outputs are very efficient, and so is PSK31. If you are running more than QRP levels on PSK31 you are QRO! And that is frowned upon as you close down everyone's receive AGC and make it difficult to work other weak stations. So go ahead and use your rig at low power, put out a clean low distortion signal and get rave reviews on how clean and easy to copy your tracks are!

Dave
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Re: PSK on TRX1

Postby KH2BR » 26 Apr 2013 02:27

The trx1 is a double side band rig. Please correct me if I am wrong, but I believe that you will be transmitting two PSK signals. One on the lower sideband and one on the upper side band.
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Re: PSK on TRX1

Postby 5B4AIY » 26 Apr 2013 12:29

Yes, you are correct, the TRX-1 is Double-Sideband Transceiver, and therefore you will indeed be transmitting both an upper and a lower sideband in PSK31, and indeed in any other mode except CW. Now, whether this 'upsets' anyone or not I'm not sure - I'm sure that the purists would object to this 'waste' of available spectrum space, but as DSB is an allowed mode it is certainly not illegal. Obviously, a single-sideband rig such as the TRX-2 is prefereable, but, hey, this is ham radio after all, and the spirit of experimentation I hope is still alive and well.
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