Re: DSB transceiver for Digital mode

Adam Rong
 

Ron,

SNR is 5-10 dB worse. However, I found that I only can make QSO with radios of -15dB SNR or better, so I think this is not a problem. Same as QRP communication, you have bigger chance to QSO with bigger signal. You may have interest to hear more signals even you don’t have chance to make QSO, but if I improve the SNR, I have to sacrifice RF output power to avoid self-oscillating. This is the limitation of using only one NE602 for TX and RX, and I chose to sacrifice RX performance to make the transceiver more balanced.

Heating is a complex question. It is documented that if the ambient temperature is around 50 C, the thermal drift of an AT cut crystal is minimal. Adding heating resistor is just to complete the heating progress in short time. There is just another way to help you if you really need help, especially on 20m band in which specific percentage of drift will cause bigger amount of drift in Hz. Also the heating power is only available during RX, so it is kind of compensation during RX.

Thanks,
Adam

在 2019年5月7日,上午2:10,Ron Stone <rsstone2@...> 写道:

Adam,

Thanks much for your responses.

When making comparisons with a big rig, how much worse was the received SNR report?  With the little rig, would you say it was 5 dB, 10 dB, or 15 dB worse?  Also, how many fewer decodes can we expect - 25% less, 50% less?   

Since I'm planning to put the rig in an enclosure with a Raspberry Pi, there is going to be plenty of heat around.  So once things warm up, do you think this would help with longer-term frequency stability and make it unnecessary to use the heating resistor?   Of course, I'll be more than happy to experiment and share my results.  

73,

Ron (KA3J)

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