WNB issue or me?

dlwarnberg

I recently installed a 4 square receive array, it's hooked directly to RX A, on ANT 1 I have a 43' vertical.  Slice A listening to 7.251 South CARS this AM and was playing with settings a bit.  My observation is one that made me question if there was an issue with WNB.

Listening I decided to turn on WNB 0 at first then slowly increasing, however I noticed added noise, almost static like when WNB is enabled and the higher I ran the setting the worse it got.

Does WNB work on RX A?  Or is it trying to work on ANT 1 and I am hearing it on RX A?

I have a FLEX-6500

WNB ON

 

WNB OFF




Any idea's?

Bill -VA3WTB

David, the WNB is working as desined. But at times it can make things worse depending on the noise you have, it happens here sometimes. On the right kind of noise it is by far the best filter I have ever used, a day saver.

Cal N3CAL

David,   I've noticed your using +20db preselector on 40m.  I usually try to keep the preselctors off on 40m and below.   What kind of results do you get with 0 db selected? 

Cal/N3CAL

dlwarnberg

Yeah Cal, I am again testing... I have not received the pre-amp for the Array yet and was trying to pull in a very weak signal.. 

With this array, with NO RF gain on I can tell there is a signal there but can not hear it, if I go to +10db the signals are there and now audible and my noise floor drops.. if I go to +20db the noise floor drops even further and those weak signals are now there and audible.

Anyway back to your question..
+20db = WNB produces lots of noise
+10db = WNB produces no noticeable increase in noise
Off = WNB produces again no noticeable noise

So the only time this is observed is when I am using +20db RF gain.. so it only seems to effect anything when using a +20db RF Gain setting.

FYI noise floor readings on clear frequency (using FRlogger slice A):
0 RF Gain = -112
+10db RF Gain  = -117
+20db RF Gain = -125

I believe this will all be eliminated when I get the pre-amp as +20db RF gain won't be used (at least I hope)

k0eoo

Hello David,

The WBN is for dealing with wide band pulse noise vs. NB for blanking pulse noise in the receive bandpass.  The issue to remember with Wide band noise blankers is that they are sensitive to strong out of band signals.  For example, at my QTH I have an issue with a AM BC station that is 5 miles from the house.  if I use the WBN the noise floor on most any of the ham bands will go up as I turn the WBN setting up; but that's only if the local BC station's signal is very strong, lets say -10 or -20dBm.  this is actually true for ALL noise blankers, be they SDR or legacy radio....

So, open up your panadapter so you can see a full 14mHz and see if you can spot the offending signal.…  YMMV

Dennis, k0eoo

dlwarnberg

Thanks Dennis...  interesting enough I opened the pan adapter wider and found nothing really but now the WNB is not adding noise either.

Thanks for the reply, I'll continue to investigate but I'd bet there was something outside the pan adapter view that was a stronger sig that was causing what I was seeing.

k0eoo

Oh by the way, on the question regarding the frontend preselector setting, I also have a 6500 and I leave my RF Gain setting at 0 for all bands except 15, 12,10 and 6m.  on those bands I use +10 and on 6m I use +20.  Usually below 10 or 15m band noise, with antenna connected, will be greater than the noise floor of the 6500 with no antenna connected. point being, adding RF Gain increases your susceptibility to strong signals.  But, I suppose if you're using a RX antenna with very low gain that would make it necessary to add +10 or +20 dB of gain?

Dennis, k0eoo

dlwarnberg

So this may be a **** question but... you guys are referring to "preselector" I see it labeled as "RF Gain" what am I missing?

Thanks

Cal N3CAL

David, you are correct,  under the Ant Menu you select RF Gain which adjusts the preamp of the 6500 (RF gain is the correct term).  The 6500 has one hardware preamp and three preamp settings .  The FLEX-6500 can be set to -10dB, 0dB (default), +10dB and +20dB.   The 6500 has a single SCU so the preamp setting applies to any of the 4 slices you may have open at the same time. 

The term Preselection deals with band filters.  The Flex manual can explain it all better than I could (39.4.1 page 152).  One point is that out of band filtering (preselection) is not available when in the WIDE mode. 

Cal/N3CAL   

VK7WH Winston

David, I thought my noise floor was pretty good but wow, -145dbm on 40M with a 100 KHz display!


I would be interested to see what happens to the noise floor when you turn off the preamp. I suspect it will go up. Also, what antenna you are using for receive?


Thanks, Winston.

dlwarnberg

Winston..  it does go up, with is set to zero it's reading about -130dbm on the scale.

Both antenna's are good, the vertical stays between -125 and -130.. the new DX Engineering 4 Square active receive array stays at -130dbm, no added noise.
Whats nice about it is as I add preamp the noise floor drops with no added noise on the speakers and signals start appearing.  I can pick signals out of the noise I never heard before or barley knew they were there.

Here is a shot, on the receive array no preamp, I do hear some static crashes currently and I understand we have a few (very few) storms in the southern part of the state (I'm in Florida near Chrystal River).



Like they say "if you can't hear them you can't work them"  Well now I hear them, the question is can they hear me??

David
KK4QOE

dlwarnberg

Thanks Cal.. will take a look

dlwarnberg

Here is a prime example... 80 meters, series of snips.. 
1) 43 Vertical no preamp (no sig seen)
2) array no preamp (sig seen)
3) array +10db (sig seen and now workable)

FYI... after completing this there are now 5 workable signals on the band





it's deceiving but the last screen shot I missed a little... I really can hear them better it's just not showing it that well as that was the "other" guy.. weaker signal I didn't even see prior

VK7WH Winston

Very impressive David. As mentioned, my noise floor is pretty good but your receive performance is outstanding. I guess the real difference is your 4 Square antenna verses my 25 feet high 80/40/30 fan dipole at my remote rural site! I guess it proves the long held view that spending effort on the antenna system is by far the most productive area to work on to improve performance in our hobby. Well done, Winston

dlwarnberg

Thank you... FYI, the 4 square active receive array is only at 35' sides... after the detached garage / shack is built and I move out there I will probably put a bit more into the array and extend it out to the 70' sides I had originally planned (just too hot and too much to clear right now)

Dan -- KC4GO

Everyone should read Tim's info on Pre-amp settings https://helpdesk.flexradio.com/hc/en-us/articles/204923669-How-to-determine-the-amount-of-RF-Preamp-gain-to-apply-for-band-conditions

dlwarnberg

I actually did and that is why I use the RF Gain when using the 4 Square Array... with no antenna selected I read the noise floor, then connected the receive array and to my surprise 90% of the time (depending on frequency and again I am only using the array on 40, 80 or 160m) the noise floor did not change or changes so little I could not measure any real change.. thus why I use 10 to 20 RF gain when using it.  Does not work the same when connected to the vertical...

Anyway thanks for the info, it is a good read.