Re: SSNA Heat

William Kimber

HI Folks,

It was noted on some other forum that some of the "other" type of DDS were fitted with 3.3 volt oscillators and they ran (O.K.) but hot on 5 volts.

I had several of the other DDS and one was marked 3.3v on osc.

Just a query on the DDS, I note that there are fewer top rated outlets selling the type the PHSNA uses than the number selling the other layout DDS.  


----- Original Message -----
From: n5ib@...
Sent: 11/23/13 07:37 AM
To: PHSNA@...
Subject: [PHSNA] RE: Re: SSNA Heat

There are a few things that will reduce the heat load.


 One is to power the UNO from the USB port. Then its on-board 5V regulator won't be used. That's about 350 mW that won't have to be dissipated.


 For those of you using the ERA-3+ version of the SSNA you could lower the Vcc supply voltage to about 8.5 V and reduce the resistor R7 to 150 ohms (still 1/2 watt). The ERA-3+ will still give its rated gain, and the 5 V regulators on the SSNA and UNO (if not powering from USB) will run cooler. Should save another 450 mW or so.


 If you have the 2N5109 version of the SSNA reducing the Vcc voltage will reduce the gain of the amplifier. I'll have to defer to Jerry for an opinion on that score. But it looks like the SSNA is running a few dB above the -10 dBm target (at least when the LPF has been stripped from the DDS module) so perhaps a modest gain reduction can be tolerated.


 Jim, N5IB

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