Thursday, November 12, 2009

40m Novice QRSS QRG

I have not looked into any possible scheme of privileges, this is what I found:
  • U.S. 7.025-7.125
  • The Netherlands 7.050-7.100
  • Germany none
In my view, it would be nice to motivate the novice radio amateur to experiment with low level power as well. This would teach that in fact, one does not necessarily need 100W and more to have fun on shortwave.

There are a couple of obvious candidates for which crystals are available:
  1. 7.100 => which can be generated by a 14.200 crystal (ESS) divided by two
  2. 7.059 => 11.0592 - 4.000
  3. 7.085 => 12.000 - 4.9152
  4. 7.096 => 3.000 + 4.096
My guess is that the band will be less noisy at 7.100, this however is a guess only.

There are a couple of other reasons why I would suggest a frequency between 7.093 and 7.097. First of all, it is very simple to build an oscillator for 14.200 with a single crystal, pull it down a bit and divide the signal using a FlipFlop. The second reason I would see in the possibility to create a very simple superhet-receiver (or transceiver) with the combination found under point 4. This combination could also be used as a simple MEPT, however, drift is more an issue in a design using the sum of two frequencies.
This leads to the obvious advantages of the two combinations using differences. Once again, a superhet is possible and in a difference of two frequencies, drift is less of an issue.

I would go so far to state that there even is a kit for a transceiver, when 7.059 is considered. Well near enough at least. This rig would allow for transmission as well as reception.
The Ten-Tec 1340 is having an intermediate frequency of 11.000MHz. A VFO generates a signal around 3.97MHz.
And here comes the mod to the kit:
  • replacing all 11MHz crystals by 11.0592MHz xtals
  • not building the VFO but an oscillator with a 4MHz xtal including a varactor for FSK
For QRSS I believe one would like to reduce the drive to the PA, since the final produces about 5W rf and would probably become hot in time. Maybe the final (2SC2166) could be left out all together. The driver is indicated to deliver 15dBm.
Further, the audio amplifier (LM386) could be left out in its entirety.

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