Topics

Ubitx and Sherwood rx tests

iz oos
 

Why not asking Sherwood to publish the rx performance of the Ubitx? Ok, maybe it will not stay in the top ten :)

Dennis Zabawa
 

Which variation?  Everyone builds theirs differently.

iz oos
 

One without mods, the latest version. Btw most of the mods regard the TX, I have not seen so many mods at the RX.


Il 16/giu/2018 13:32, "Dennis Zabawa" <kg4rul@...> ha scritto:
Which variation?  Everyone builds theirs differently.

ajparent1/kb1gmx
 

Sherwood only tests receivers so the only must have mod is the RX AGC ND6T flavor.

All the hot receivers are SDR and direct digital sample (flex, and Anan) thought the
7300 (also a SDR) is up there.

Of the radios using more conventional analog techniques two of mine the Atlas 
and the TT 340 are fair comparisons for single conversion.  The Tentec is the
only low IF with selectable filters at 9mhz to digital IF unlike those with VHF
first IFs.  Of those three the  listed radios Tentec Eagle, Atlas 215X,
Tentec 340/Triton  on the list in that order from best to worst.  This radio
without AGC is not likely to be above any of them.  Also the Atlas 215X a
1976ish design is a diode mixer front end like the uBitx with and AGC in
the IF and a diode mixer for product detector so it would compare
closest to the uBitx.  

Note: In dollars none of those radios even as used/broken approach 100$
and new were much more expensive by many times.

Comparable transceivers in the power class is FT817, IC703 and
Tentec Argonaut QRP series such as the used Argonaut model 505
that I use very regular for the 5W QRP level.

Reasons that is likely:
RX overload point, the limit here being the diode mixer. 
Filters First (45mhz) is wide and the second is fixed at SSB bandwidth.
close in and wide overload
Phase noise from the LO systems (LO1, LO2, BFO).

Sensitivity is never an issue.  

Allison

Ashhar Farhan
 

the contemporary method of rating the goodness of a receiver is now down to a single test : reciprocal mixing dynamic range. simply stated, you have  very low distortion crystal oscillator amplified to +10 dbm and fed through a very stiff low pass filter. Then you use this as the input to a receiver and tune away by 20 KHz and measure the increase in noise, with the +10dbm signal switch on and off.  this will measure the phase noise as well as blocking dynamic range, as well as (indirectly, though) the IIP3. 
The other parameter is the in-channel dynamic range. That is, what is the range of signals that the radio can handle simultaneously within the audio pass-band. currently, 90 db is the winner.
Finally, there is the most important though completely unquantifiable quality of how operator fatigue. How much tired will you be after listening to the radio for 10 hours continuously? 
A great vintage radio that satisfies these is the Drake TR4. Sherwood is all praise for them. Even to this day, an analog VFO based radio with  decent audio chain will run circles around the Flex6700. Try a microR2 if you can get hold of one.
- f

On Sun, Jun 17, 2018 at 2:31 AM, ajparent1/KB1GMX <kb1gmx@...> wrote:
Sherwood only tests receivers so the only must have mod is the RX AGC ND6T flavor.

All the hot receivers are SDR and direct digital sample (flex, and Anan) thought the
7300 (also a SDR) is up there.

Of the radios using more conventional analog techniques two of mine the Atlas 
and the TT 340 are fair comparisons for single conversion.  The Tentec is the
only low IF with selectable filters at 9mhz to digital IF unlike those with VHF
first IFs.  Of those three the  listed radios Tentec Eagle, Atlas 215X,
Tentec 340/Triton  on the list in that order from best to worst.  This radio
without AGC is not likely to be above any of them.  Also the Atlas 215X a
1976ish design is a diode mixer front end like the uBitx with and AGC in
the IF and a diode mixer for product detector so it would compare
closest to the uBitx.  

Note: In dollars none of those radios even as used/broken approach 100$
and new were much more expensive by many times.

Comparable transceivers in the power class is FT817, IC703 and
Tentec Argonaut QRP series such as the used Argonaut model 505
that I use very regular for the 5W QRP level.

Reasons that is likely:
RX overload point, the limit here being the diode mixer. 
Filters First (45mhz) is wide and the second is fixed at SSB bandwidth.
close in and wide overload
Phase noise from the LO systems (LO1, LO2, BFO).

Sensitivity is never an issue.  

Allison


ajparent1/kb1gmx
 

Between the microR2 and the miniR2, yes, they listen easy.
The most noticeable property is listening to a pile up, rather than a mis of heterodynes
and noise you hear what sounds like a busy restaurant with everyone talking.  Its then
up to the ear to pick it apart.

The closest I have to the Drake is the Atlas 210X, it was a single conversion HF IF 
solid state radio when that was becoming common.  Its twist is no RF amp.  If we
get past the VFO drift some suffered it was a very clean radio to listen to on a busy
band.  I was lucky to find two of them in functional condition missing things like Mic
and power connector and needing some minor fixes.  One is fully restored and
includes a few engineering fixes from back when and its a very nice, compact for
a 100W radio, and yet a very simple radio.

I've worked on Drake R4Cs and TR4s and they are very good but there are a set
of mods for them that make it an amazing radio.  The one feature was the PTO being
good and stable.    Yes, people mod radios even then!  Adding new technology
and knowledge to make a good radio better.

How a radio sounds and feel is why some radios I have get used more.  IT's that 
intangible better.

Allison