Bill, I assume that the 1296 transverter is double conversion to get to 28 MHzI IF, whereas the 222 box is single conversion.
The extra conversion needs some take-over gain to minimize the losses of the extra mixer in the chain. It wouldn’t surprise me to find out the 1296 machine has an extra 20 dB of gain in the system — thereby the 20 dB greater OUTPUT noise floor. Vy 73, Mike - W8MM > On Nov 20, 2014, at 2:04 PM, Bill Tynan <billandmat...@windstream.net> wrote: > > I am baffled. > > > > Here's what I have: > > > > Flex 5K > > DEMI transverters for 222 and 1296 > > > > I have set the offsets for both on the transverter screen - 194 MHz for 222 > and 1268 for 1296. All other parameters are the same. For both 222 and 1296. > > > > I have been using the 222 transverter with good results. > > > > In trying to get the 1296 set up, here is what I find: > > > > Without either transverter powered and a 50 Ohm dummy load plugged into the > transverter port on the 5K: > > > > Selecting 222, noise level is -131 dBm > > Selecting 1296 noise level is -111 dBm > > A 20 dB difference!!!! > > Why should they not be the same? Both are a 28 MHz. input. > > > > After first making sure that 10 meters was open and I was hearing signals, I > plugged the antenna into the transverter port but could hear nothing. Ok, > maybe the transverter port has a pretty low sensitivity and needs more RF, > as it would get from any transverter. So, then with the dummy load plugged > into the transverter port, I tried transmitting while listening on a > separate receiver. I heard nothing. Yes, it's only a few milliwatts, but I > would think I would be able to rear it. > > > > Why should the noise level for the 222 and 1296 selections be different when > they are both the same 28 MHz transverter port? Aa I said, all parameters on > the transverter screen are set the same, except, of course for the frequency > off-sets. > > > > Anyone have any ideas? > > > > Any help would be greatly appreciated. > > > > 73, > > > > Bill Tynan, W3XO > > _______________________________________________ > FlexRadio Systems Mailing List > FlexRadio@flex-radio.biz > To opt out of the Reflector: > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz To opt out of the Reflector: http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
