NE612 Transverter

Something I found on the internet and would like to share:
http://www.geocities.jp/ja6hic/rig/6/trans.gif
I have seen NE612 transverters before, those were using two NE612s. JA6HIC uses one chip for both RX and TX conversion. The rest of the design involves an external LO.

The circuit is fed by RX and TX control voltages, this may be handy in places, although I believe that this is merely a remainder of JA6HIC's earlier designs involving diode mixers.
However, I believe a running the transverter from the general supply could be advantageous in particular since there could be a delay between powering down the RX and powering up the TX trains, which could cause the circuit not being supplied and therefore shut down. Using an external LO, it would not matter to shut down the transverter for a moment. However, the NE612 has got an internal oscillator, when using this, we certainly would not like to power down the chip just to power it up again... this would result in terrible chirp.

So, this is my plan: make use of this very simple but elegant design for transverters for 136kHz, 501kHz and 70MHz.  I will be using the internal oscillator of the NE612 as a crystal oscillator. The following obvious options will be available cheaply (the mark (-) indicated subtractive mixing which inverts the band, (*) indicates my preference):

• 136kHz: 2.000MHz - 160m band (-)
• 136kHz: 2.048MHz - 160m band (-)
• 136kHz: 3.500MHz - 80m band
• 136kHz: 3.579MHz - 80m band
• 136kHz: 3.686MHz - 80m band (-)
• 136kHz: 7.000MHz - 40m band
• 136kHz: 7.159MHz - 40m band (-)
• 136kHz: 10.000MHz - 30m band (*)
• 136kHz: 14.000MHz - 20m band
• 136kHz: 14.318MHz - 20m band (-)
• 136kHz: 27.000MHz - 11m band 

• 501kHz: 2.458MHz - 160m band (-)
• 501kHz: 3.000MHz - 80m band (*)
• 501kHz: 3.072MHz - 80m band
• 501kHz: 3.276MHz - 80m band
• 501kHz: 4.096MHz - 80m band (-)
• 501kHz: 4.194MHz - 80m band (-)
• 501kHz: 6.5536MHz - 40m band 
• 501kHz: 13.560MHz - 20m band 
• 501kHz: 14.745MHz - 20m band (-)

• 70.0MHz: 20.000MHz - 6m band (*)

All there is to do is to build an RF-vox circuit and an attenuator (for the TX).

4m & 6m Trapped Dipole

The VRC8000 covers both, the 6m and 4m bands. It would therefore be desirable to use one aerial only for the rig. Quick and dirty idea, a trapped dipole.

Assuming a trap frequency of 70.2MHz, the calculated values would be L=0.5µH and C=10.3pF.
Playing with MMANA, I found a span for the 4m dipole of 205cm. The additional radiator wires for 6m would amount to 26.8cm each. In the 6m band, 51.0MHz was taken as design frequency, due to the FM-nature of rig mentioned above.

The design has not been put to reality yet. However, if one wants to play with a simulation, here is the mmana-file:

4m / 6m trapped dipole
*
50.5
***Wires***
3
1.041e-17,    -1.025,    1.041e-17,    1.360e-16,    1.025,    1.360e-16,    8.000e-04,    -1
0.0,    -1.025,    0.0,    1.642e-17,    -1.293,    1.642e-17,    8.000e-04,    -1
0.0,    1.025,    0.0,    1.642e-17,    1.293,    1.642e-17,    8.000e-04,    -1
***Source***
1,    1
w1c,    0.0,    1.0
***Load***
2,    1
w1b,    0,    0.5,    10.280069,    0.0
w1e,    0,    0.5,    10.280069,    0.0
***Segmentation***
800,    80,    2.0,    1
***G/H/M/R/AzEl/X***
2,    7.0,    1,    50.0,    120,    60,    0.0
###Comment###
Mod by Joachim, PA1GSJ 07/01/2011 20:33:45
Created by Joachim, PA1GSJ 07/01/2011 20:21:12 

Getting ready for the 4m band

If all goes according to plans/wishes, Dutch radio amateur will soon be allowed to use the 4m band between 70.0Mhz and 70.5Mhz. Trying to avoid the mistake of being surprised and hence not properly prepared for 600m, I started considering options for 4m.

First thing was looking for available surplus/commercial equipment. Unfortunately, in this range, all available surplus rigs are providing FM only. Best candidate so far, the VRC8000; actually, I plan to pick up one, before they are all gone. Advantage of this rig, it will also cover 6m.

I guess, a lot of operation will make use of CW and USB. Since no commercial rig seems available, a transverter could be the best shot here.
There are two CMOS oscillators available which would be suitable for the job converting/transverting to the 30m band: 60MHz (regular mixing) and 30MHz (subharmonic mixing).
Another two CMOS oscillators would enable us to convert the 4m band to the 6m band: 20MHz (regular mixing) and 10MHz (subharmonic mixing).

For being prepared, I will to pick a VRC8000 asap, and also consider to build a subharmonic transverter for the 6m band.