The bandwidth is really not well defined (or written in stone), in that it is dependent on the characteristics of the LC filter that you use with the unit. The 80 KHz they mention in the add is just a ballpark number. I run them with Linrad and the Delta44 and get the full 90 KHz or so bandwidth available with the Delta44. I am sure I could get more if I had one of the super soundcards.It is an I Q receiver with 80khz bandwidth.
It is really a wideband device. You select bands by (1) changing the LO and (2) sticking an LC filter on the front. The main limit on the frequency range currently is the difficulty of finding a chip that will do 4*f for the LO as is needed for the I/Q mixer. They are working on this and higher frequencies than 28 MHz should be do-able. I don't use the crystals at all, just an external (GPS locked) synthesizer for the LO.It is crystal controlled and can tune the popular HF bands
, so it seems the 10 Mhz version might be the logical choice to fit Leifs mixing plan for down conversion. As well, the 28 mhz version could be built and used with a standard 2m/10m converter.Yes! It works fine with both the LT2S here and also homebrew front end to go from 144 to 28.
The target use is for HF reception which aparently is less demanding then EME, as Leif has defined it. It uses TUF-1 mixers and ordinary crystal oscillators. There is no mention of any attempt at reducing phase noise or any mention of using an advanced sound card such as the Delta 44. I Q detection is balanced on board. Since a 6db NF at HF is perfectlyDon't forget that your NF is mostly determined by the NF of the first stage and the NF contribution of following stages is divided by the gain of the intial stages. So if you have a 0.2 dB NF preamp on the tower with a gain of 20-25 dB, you will still do quite well if the next stage has TUF-1's or whatever. I use that here, actually with two stages before the TUF-1H's in the shack. If you have 20 dB of net gain before TTM, its 6 dB NF becomes
ok and most signals tend to be similar in signal level, the TUF-1 mixers probably have sufficient dynamic range most of the time on HF. A 20db attenuator (26db noise figure) on the PCB is made available for setting the noise floor on HF.
I suspect that when a strong local signal is present and a very weak EME signal is desired in the same passband, the Time Machine would not hold a candle to the 2.5 mhz I Q detector designed by Leif. The assembled price is $170 and kit form is $135, making it a tempting project for a rural EMEer or perhaps an Urban EMEer such as myself that does not normally experience local signals at the low end any closer then 30 km away (10db over S9) and is somewhat pocket book challenged. The big question then becomes, what is the dynamic range of the Time Machine? 80 db perhaps?I think that the dynamic range of your sound card and Linrad will likely be the determining factor rather than TTM hardware. The TUF-1 is not the limiting factor. And if you are concerned about that, and have enough LO power, you can substitute a TUF-1H.