Re: [softrock40] 20M Lite II build, getting 6875 WWCR on 14057Mhz
----- Original Message -----
Subject: Re: [softrock40] 20M Lite II build, getting 6875 WWCR on 14057Mhz
>> The design of the 20m softrock is using 1/3 harmonic subsampling of
>> the LO and then attenuating the unwanted frequencies via the bandpass
>> filter. Strong lower frequency signals will sometimes bubble up. If
>> there aren't any other issues with the receiver, I'd assume that this
>> is what is happening. If it is bad or bothering you, I think you could
>> build a better (external) bandpass filter.
> I do not yet have my SoftRock kit built (not even started yet). Many of
> the messages I have seen on this and a couple of other lists regarding
> problems with SDR rigs have me pretty much discouraged. When I saw the
> original post here my immediate thought was he needs a low pass filter
> in front of the receiver but wait to see what the SDR users have to say
> about some *other* flimflammery/magic/esoteric software. Maybe I *can*
> make mine work when I get it built. By the way - I did touch the
> unopened bags today <evil grin>. I have somebody else's radio on my
> bench and getting it back to him comes first before that SoftRock thingy.
Most comments praise the Softrock's performance.
A Softrock is not a $1000++ rig so occasionally strong out of band signals do give problems.
But most times nothing is noticed and users are very satisfied.
Indeed often reception and audio quality equal that of a $1000++ rig.. but not always.
I do not think WWCR 6875 fits with the usual 1/4 of LO.problem, may be overload is the answer.
Keep the audio input to a minimum.
Check the simple BPF is correctly constructed, but if it really is a severe problem then extra filtering may be needed.
Is the 14.030 dead centre? If not then detective work might find it. But I guess it is not seen with the Ensemble.
73 Alan G4ZFQ
- On 09/04/2013 01:49 AM, kf5jmd@... wrote:
> Bill, no need to worry, the only one that has this problem is the 20M
> because of strong signals and the way it samples 1/3 harmonic instead
> of standard "divide by 4" like the 40M, 80M, 160M kits.
> I have built 2 of the Lite II Receivers, and one Ensemble RX II HF
> build. The 40M Lite II I built works absolutely perfect, never an
> issue, the image issue was on the 20M. I will build a bandpass filter
> for it BEFORE the receiver so that will solve that issue for me. The
> Ensemble RX II is a wonderful receiver, I absolutely love it, have 0
> regrets, 0 issues. I just can't get over how powerful it is vs the
> low price!
Mine is a SoftRock_40_R for 20 meters. I bought it from somebody else
(maybe on this list) unopened. Even if there are some birdies from
transmitters in other bands - well that's why we make filters. SDR rigs
in general and SoftRock in particular have no corner on the RFI market.
It's certainly nothing new. Problem or not depends on characteristics of
the radio design, tolerance stack of the parts in individual radios and
the really big one - the actual environment where the radio is used. In
the case of the original post - if there was no transmitter on 6875 he
would not have any problem at all. I am thinking about getting a
Softrock to hang on the IF of a couple of my older receivers here.
Depends somewhat on my experiences with the kit laying on the bench over
in the northeast corner.
Yes indeed. The price is glaringly obvious!! I started a while back
playing with some of the free DSP sound card software and noticed the
filtering. I found a couple of software packages that give me pretty
darn good filtering and spectral displays too and I don't actually use
them for anything else. That leads obviously to an interest in SDR rigs
- at least curiosity. With these prices there is just no reason not to
give it a try - except - I am not interested in learning more about
computers and layers of program menus. I already have learned more about
that than I ever wanted to know. One of the things I learned is that I
do NOT want to know very much more about computers <evil grin>.
I also have some digital hardware - specifically scaf audio filters.
Center frequency and bandwidth are controlled by the clocking frequency,
they live in a very small box (field portable) and NO computer or
software menu is required. I get dramatic improvements using those, too.
- Hi Chris, I have built the Lite and mine is on 40 M, its been awhile though. I would try a metal enclosure for the circuit board with connectors and the whole smear. I have notice before that all the SDR's are sensitive to hi levels of RF when they are not in their metal boxes. Of course assuming yours is not. Just an idea. Bill KN8DMK..