[NLRS] 222 ???

[John P. Toscano]

Gerald wrote:

>
>On Wed, 2005-09-14 at 09:44 -0500, John P. Toscano wrote:
>
>>Gerald wrote:
>>
>>
><SNIP>
>
>>P.S., if I was doing it all over again, I'd think twice about using
>>the TIB interface, because the ALC level adjustment is very fussy
>>and doesn't seem to hold steady from one month to another.
>>
>
>The ALC input is part of a control feedback look which doesn't need loop
>gain stability. That can let it be variable. One could use an ALC
>detector at the input of the transverter to probably control the last
>20% of the voltage going to the exciter. One could detect the input
>signal and use a variable attenuator on the input of the transverter, as
>in some of the transverters in G3SEK's book.
>

Yes, that sounds like an excellent improvement on the current situation,
but there are other reasons to go the SDR route for the IF rig also.

>>I am seriously considering following KM0T's lead and setting up a
>>SDR-1000 Software-Defined Radio as the IF for 222, 902, 1296, and 2304
>>in the future, and with only about 1 watt of maximum output plus
>>easy setting of lower transmit levels, the problem should go away.
>>In your case, as Jerry points out, using one of the DEMI 10-watt
>>attenuator interface units is a good plan.  The transverter has
>>plenty of dynamic range on the Rx gain level, so even if you lose
>>some of the 10M signal back into the radio from the transverter due
>>to the attenuator, you can turn up the Rx gain (at the IF level) to
>>overcome it.  Note that since this is on the 10M side, not the 222
>>side, it will not harm your receive NF or receive sensitivity.
>>
>With lots of strong and weak signals about, receiver gain in front of
>the IF rig is very important.
>
Oh, absolutely.  I just meant to say that the DEMI transverter has more
than sufficient Rx gain available so that even with some attenuation
between the IF rig and the transverter, it is still possible to adjust
the Rx gain so that signals are where they belong.  IIRC, At maximum
Rx gain, the noise floor on my IF rig from the 222 transverter is
around S6 - S8 or thereabouts, so I have turned the Rx gain down quite
a bit to bring the noise floor down to where it belongs.  I believe
that the adjustment range is approximately 25 dB, and there is even an
option to add one more stage of gain if the path from the transverter
Rx to the IF radio Rx has too much loss, but the DEMI folks are quick
to point out that it is very rare to need (or want) it.

John (W0JT)