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Author Topic: How do I use the VRF on a Yaesu FT-DX5000?  (Read 3123 times)
W9KDX
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Posts: 770




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« on: May 20, 2012, 06:07:30 AM »

I really have searched and sent a few emails to Yaesu (they say they are trying to figure it out) and I would really like to understand how the VRF works and how I should be using it.  The numbers don't make any sense to me and I am not sure when I should use it or when I should not.

All the other features are making sense, but this one is just beyond me.  I know it is an RF preselector which works in conjunction with a bank of fixed bandpass filters, but that knowledge doesn't help me adjust the knob, nor does it help me understand what I am doing. 

A number of reviewers have said it is an awesome feature, once you figure out how to use it, but they forget to tell me the important part- how to use it.

Please help.
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Sam
W9KDX
N4RSS
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Posts: 260




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« Reply #1 on: May 20, 2012, 06:17:57 AM »

Just turn the knob and hunt for a peak in received audio or background noise. If it seems too difficult then turn it off; it doesn't make a huge difference either way.

I'm fairly sure this in fact has been discussed on the yahoo board Wink
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KA4POL
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Posts: 2028




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« Reply #2 on: May 20, 2012, 08:50:23 AM »

I think you already got the point seeing this as a preselector, i.e. a variable bandpass to filter out unwanted interference. So you'll only see the effect if there are many close by signals and not just one.
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K8AXW
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Posts: 3900




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« Reply #3 on: May 20, 2012, 10:36:40 AM »

KDX: 
Quote
emails to Yaesu (they say they are trying to figure it out)
Wow!  If Yaesu doesn't know, who in the hell does!!

One of the great things about ham radio is that we have all of this gear with buttons, knobs and switches all over them and we get to twist, flip and push all we want!  This is one reason why hams enjoy channel surfing with a remote which drives their XYL crazy!

With that being said, the best way to find out what a particular control does is to turn, push or flip it and see what happens.  Enjoy. 

Then, and only then, if you still don't know, read the manual.  To do otherwise is un-American!
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W9KDX
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Posts: 770




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« Reply #4 on: May 20, 2012, 02:33:11 PM »

KDX: 
Quote
emails to Yaesu (they say they are trying to figure it out)
Wow!  If Yaesu doesn't know, who in the hell does!!

One of the great things about ham radio is that we have all of this gear with buttons, knobs and switches all over them and we get to twist, flip and push all we want!  This is one reason why hams enjoy channel surfing with a remote which drives their XYL crazy!

With that being said, the best way to find out what a particular control does is to turn, push or flip it and see what happens.  Enjoy. 

Then, and only then, if you still don't know, read the manual.  To do otherwise is un-American!

Already read the manual from cover to cover and it is no help.  I really did get that answer from Yaesu. 

KA4POL, thanks for the comment about removing interference from unwanted signals.  That helps a lot; I am really looking for what circumstances I would encounter when I might use this.  Just playing around with these things does very little good unless I am aware of the problem that the playing around is supposed to solve.
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Sam
W9KDX
N4RSS
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Posts: 260




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« Reply #5 on: May 20, 2012, 05:15:30 PM »

Try using it bring up weak signals thats what I use it for.

It is as simple as that
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K0OD
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Posts: 2558




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« Reply #6 on: May 20, 2012, 05:40:02 PM »

For for the rest of us, what the H... does VRF stand for?

"Variable RF Front-End Filter (Preselector)

    Yaesu's engineers have incorporated a high-Q "VRF" preselector filter for the Mark-V and Field transceivers, affording exceptional RF selectivity on the 160 - 20 meter bands, where antenna dimensions can be large, leading to high input signal voltages. The VRF filter is engaged using mechanical relays, not diodes that can contribute IMD, and it may be manually adjusted from the front panel. "


I think TRF radios had about the same thing in 1920.
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W9KDX
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Posts: 770




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« Reply #7 on: May 20, 2012, 07:00:27 PM »

Now I'm worse off than when I started.  Is it for weak signals or help with interference with overly strong signals?  From the description, it sounds like it is actually to reduce signal strength when it is too strong and it depends on the antenna size?

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Sam
W9KDX
KA4POL
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Posts: 2028




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« Reply #8 on: May 20, 2012, 10:10:06 PM »

Is it for weak signals or help with interference with overly strong signals? 
It is for both. Imagine you got a weak signal and a strong one below and another strong one above. Now you want to filter away the two strong signals so you can hear the weak one. You narrow the filter until the unwanted signals are attenuated by so much that you can listen to the weak signal.
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K0OD
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Posts: 2558




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« Reply #9 on: May 21, 2012, 06:02:47 AM »

No preselector will separate stations nearly on top of each other. This is from the FT-1000MP manual:

"The VRF feature allows you to engage a narrowband-pass “preselector” filter into the receiver’s RF circuit path. The added selectivity can be a tremendous help in minimizing potential interference from strong out-of-band signals, especially in a multi-transmitteroperating environment

If a potentially-interfering signal is very near your current operating frequency (for example, an SSB station operating near 3.80 MHz while you are on 3.52 MHz),additional protection may be realized by deliberately mistuning the VRF so as to place more “roll-off” of theundesired signal. In this example, tuning the VRF forpeak response at 3.40 MHz will cause additional attenuation to be placed on the strong signal at 3.80 MHz.Particularly on the lower frequency bands, there will beno loss of useful sensitivity with moderate detuning,but interference rejection will be significantly enhanced"
« Last Edit: May 21, 2012, 06:06:09 AM by K0OD » Logged
W9KDX
Member

Posts: 770




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« Reply #10 on: May 22, 2012, 07:00:00 PM »

No preselector will separate stations nearly on top of each other. This is from the FT-1000MP manual:

"The VRF feature allows you to engage a narrowband-pass “preselector” filter into the receiver’s RF circuit path. The added selectivity can be a tremendous help in minimizing potential interference from strong out-of-band signals, especially in a multi-transmitteroperating environment

If a potentially-interfering signal is very near your current operating frequency (for example, an SSB station operating near 3.80 MHz while you are on 3.52 MHz),additional protection may be realized by deliberately mistuning the VRF so as to place more “roll-off” of theundesired signal. In this example, tuning the VRF forpeak response at 3.40 MHz will cause additional attenuation to be placed on the strong signal at 3.80 MHz.Particularly on the lower frequency bands, there will beno loss of useful sensitivity with moderate detuning,but interference rejection will be significantly enhanced"


Thanks for the quote from the older manual.  The 5000 manual glosses over and barely indicates anything.

Last question, would you ever use notch or shift in combination with VRF?
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Sam
W9KDX
K8AC
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Posts: 1477




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« Reply #11 on: May 23, 2012, 04:42:05 AM »

Sam -  you probably ought to seek technical answers somewhere other than here!  The VRF may be useful in very limited circumstances where a band is crowded with very strong signals (160, 80 or 20M during a CW contest) or if there's a KW station down the block from you on the other end of the band. Or, it might be of use in the event you're operating a multi-op contest or DXpedition station where you have two stations operating simultaneously on the same band. The VRF tuning is rather broad, by design, and does absolutely nothing for weak signals unless the receiver front end is being affected by one of the conditions I mentioned.  It is NOT intended for, nor does it perform any function related to improving close-in selectivity.

It's no surprise to me that you couldn't find someone at Yaesu who could explain the function.  When I first saw the FTDX5000 at Orlando a couple of years ago, none of the booth reps knew much of anything about it, nor did they care.  And yes, I have owned one - and dumped it after a couple of months.  If you operate CW, you'll likely eventually dump it as well, but that's another story. 

73, Floyd - K8AC
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K0OD
Member

Posts: 2558




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« Reply #12 on: May 23, 2012, 06:41:05 AM »

"would you ever use notch or shift in combination with VRF?"

I would think you would. But I don't own a Yaesu. Isn't there a Yahoo Group where you could get expert help from owners of your exact model?
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W9KDX
Member

Posts: 770




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« Reply #13 on: May 23, 2012, 06:06:08 PM »

Sam -  you probably ought to seek technical answers somewhere other than here!  The VRF may be useful in very limited circumstances where a band is crowded with very strong signals (160, 80 or 20M during a CW contest) or if there's a KW station down the block from you on the other end of the band. Or, it might be of use in the event you're operating a multi-op contest or DXpedition station where you have two stations operating simultaneously on the same band. The VRF tuning is rather broad, by design, and does absolutely nothing for weak signals unless the receiver front end is being affected by one of the conditions I mentioned.  It is NOT intended for, nor does it perform any function related to improving close-in selectivity.

It's no surprise to me that you couldn't find someone at Yaesu who could explain the function.  When I first saw the FTDX5000 at Orlando a couple of years ago, none of the booth reps knew much of anything about it, nor did they care.  And yes, I have owned one - and dumped it after a couple of months.  If you operate CW, you'll likely eventually dump it as well, but that's another story. 

73, Floyd - K8AC

Thanks for the input.  I was aware of the CW issues before I bought and they are not a problem.
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Sam
W9KDX
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