IF Shift for SmartSDR

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When I had a Flex 1500, I seem to remember having the ability to move the receive slice similar to using IF Shift on a knobbed radio, in PowerSDR. Not talking about changing the filter width, but, moving the filter, without changing frequency. Sometimes that worked really well in getting rid of bleedover from someone who was close in, but, on the opposite side of where I could adjust the filter width. Hope I'm making some sense here. (I know what I mean, but, sometimes the words just don't pop out right!!)
It would be nice if SmartSDR had that feature. And it may well do so. I just cannot find anything telling that it does or how to use it.
james
WD5GWY
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James Whiteway

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Posted 4 years ago

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James Whiteway

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I'm either not explaining clearly or no one knows the answer! :-)

I thought, and still do, that PSDR had a feature similiar to Passband tuning or IF Shift. Where you could move the passband, without changing the receive frequency.

My Yaesu FT-1000 MP MKV has it.
So I figured SSDR has the same function and I just cannot find it. Or, a reference to it.
(Edited)
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Stan - VA7NF

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Depending on why you want to move the IF:

On the panadapter, hover the mouse over an edge of the (blue) filter, left-click and drag to where you want.

If you are trying to avoid interference, turn on the TNF (click at bottom of screen) then place the filter over the problem signal.  This will give you a variable width notch filter inside your passband. 

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James Whiteway

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Close, but not what I'm looking for. What you're talking about is adjusting the filter width. What I'm trying to describe moves the shaded area of the filter ,without changing the filter's width. If you are getting bleedover, splatter etc from outside the filter's width, then just changing the filter's width or using a TNF won't effect it at all. Splatter can move depending on the voice peaks of the offending signal. Moving the passband (or IF Shift) can move the desired signal away from the offending signal without changing the receive frequency. My Yeasu, ICOM'S all have this feature.
And I thought I remember PowerSDR having it as well.
Hovering the mouse over the filter opposite the side where you could vary the filter width, (depends on USB LSB) the pointer would change to a hand. Holdung the left mouse button down, you could then move the filter without changing frequency.
Or, maybe I'm getting senile in my old age!
:-)
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Bob Wright, N7ZO

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Hi James,

How about this, from the Software manual section 28.6.4:   Filter Control Widget



"The Filter Control Widget is used to adjust the high cut and low cut of the Receive Filter. To initiate the Filter Control Widget, hover your mouse over the Carrier Frequency just above the horizontal axis Frequency bar. This will cause the Filter Control Widget to appear. Within the control there are three sections separated by dotted lines."

"The center section adjusts both the high cut and low cut of the filter simultaneously. Hovering over the center section will display a four way arrow. Clicking and dragging up and down from within this section will decrease/increase the low cut while increasing the high cut of the filter effectively making the Receive Filter bar wider. Clicking and dragging left and right will move the Receive Filter bar left and right relative to the Carrier Frequency"
(Edited)
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W5XZ - dan

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perfect description, bob...73, w5xz, dan
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Gerald - K5SDR, Official Rep

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Bob has correctly called out the IF shift equivalent from the manual.  The last sentence is exactly that function.  I guess we should have just called it IF shift in the manual.  ;>)  
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James Whiteway

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Thanks Bob and Gerald!
Gerald, maybe not call it IF Shift, but noted it functioned similar to IF Shift. Makes it easier on us old guys that way! :-)
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James Whiteway

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I've tried/used that and it works fairly well. But, it is not quite the same as I am talking about. IF Shift and Passband tuning work differently than filters. I need to call the guy who bought my 1500 and get him to send me a screenshot of PSDR while using this feature.
That might make more sense then.
Thanks for your suggestion.
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Ken - NM9P, Elmer

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IF shift on legacy radios did essentially what was described. It shifted the IF oscillators so that the passband of the filter was shifted higher or lower in frequency relative to the station transmitting.

Kenwood then came out with two controls which allowed high cut and low cut independently. It was very effective if you had two IF filters in line.

On the 6000 series, rather than dragging the IF stripe on the display to shift the filter passband, you can do as suggested above, or use the IF filter tool in the TX/RX panel if you have it open.
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John n0snx

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No James SSDR does not have the IF shift like PSDR... Wish it did cause it was a neat feature... Just had to grab the filter with the mouse and slide it over without changing the filter width... I would like to see that feature implemented into SSDR

John
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Ken - NM9P, Elmer

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That would be a nice right-click-drag option for the 6500.
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James Whiteway

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Thanks John! I knew I wasn't imagining that!
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Stan - VA7NF

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I must be loosing perspective on this item.  The signal is digitized at the antenna and the slice "mixes" it down to baseband for listening/display.  As there is no IF, everything coming into the antenna is presented exactly as received without distortion.

If not the filtering of the baseband, what are you looking for?  The splatter received at the antenna will always remain in exact relationship with the wanted signal leaving the brick wall bandwidth filter of the signal, tunable notch filter(s) of undesirable "Frequencies" within that passband, and noise filtering which may ADD AGC interaction with in-band signals by out-of-band "noise".

What there isn't, and I expect a long ways off "Science Project", is a mathematical removal of phase related content from an undesired signal that originates in-band or out-of-band.  This touches on the full diversity noise reduction algorithms but certainly not a "Tunable IF Filter".

Please help this old logical brain get back in phase with the desired result.

Stan Williams  VA7NF

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Dale KB5VE

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I also liked the way the power sdr would move the filter. But as thing change I have moved it using the pop up or the fixed display in the Rx Tx screen. Having owned many of the quote super receivers including the Orion I can say the flex radios are winners. The 5000 was great and the 6500 is better. The one thing some new flex owners get a little upset over is the fact they cannot get some of the adjacent splatter out of the recieve. Usually this is the cracking sound almost like static but is tied to an adjacent signal. I have show many new and old users that what they are hearing is a real signal within their recieve pass band. If you look close you will see small signs of the signal. In this case you cannot filter out what is a signal In the pass band you are listening to.this is usually caused by over drive or excessive audio on the transmitter of the adjacent signal. I have always called this blow by of the transmit filter. See a lot of it when people stick the rack equipment on their station and don't know how to set it up.

So when we say brick wall I agree it stops the splatter you would get from a strong , very strong clean signal but if there is actual signs of the signal in the pass band the only thing you can do is try thr tnf where it exist. I am content with the superior performance I am getting from my 6500. And still fell the previous generation of flex radios will run with most of the radios comming out today. Real bargains on the 5000 now.
(Edited)
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James Whiteway

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Thanks everyone for all your help.
That is one of the things I like about the Flex Community. Everyone is willing to try and answer questions such as mine, no matter how poorly stated!
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James Whiteway

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Just got back home.(long haul truck driver) And sure enough, the filter can be moved without
changing the receive frequency!!! And, someone was nice enough to create some splatter below the group I was listening to and just moving the filter a tiny bit, got rid of them!!
Again, I really do appreciate everyone's comments and help.
Looking forward to the next release of SmartSDR!!!
james
WD5GWY
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Adam Farson

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There is a semantic problem here: a direct-sampling SDR does not have an IF strictly speaking. Channel shift or passband shift would be a more correct term.

73, Adam VA7OJ/AB4OJ
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Bob Wright, N7ZO

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Hi Adam,
FlexRadio simply calls it the "Receive Filter".
(Edited)
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James Whiteway

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And it works too!!!!