Overload of the flex.

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  • Updated 6 months ago
Good Morning all.  I have a neighbor that is 3 houses up the street from me.  He is a ham.  Our antenna's are maybe 150 feet apart.  He runs an amp.  On my 7300, I have to move off 40 meters or go away from where he is.  Turn on the attenuator.  I do the same thing to him I am sure.  There is no problems as we have an understanding.  Good friends and neighbors.  Will this affect the flex any more than it does the 7300.  

KB4OIF
John
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KB4OIF

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Posted 6 months ago

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Sergey, R5AU

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John, proper article you can download here, all described are in details
http://www.flexradio.com/downloads/flex-6000-fdx-power-calculation-worksheet-pdf/
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John - K3MA

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I do not have any hard data.  Only comparison operation with different rigs at the same time.  My experience is that the Flex 6500 will fair much better and is less prone to overload than the IC7300.  The newer Flex 6600 is going to have additional capability to reject strong local signals better than my 6500.

I think if you read user reviews on the IC7300 you will find that many have experienced overload with it even without a close other station such as your situation.  That was also the experience I had with the one I used in my shack.

No opinion matters like yours.  So you can test them in your shack with your conditions.  I believe Flex still offers a 30 day no questions asked full refund (minus shipping).  So buy a 6600 or 6600M (or even the 6400/6400M) and test it beside the IC7300 in your shack.  If it does not perform better than return it.

John K3MA
(Edited)
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Sergey, R5AU

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Well John, with exisitng overview many Overloads just LED falshing, BTW real overload put up dramatically noise level up or make signal not redable at all. Howeve your are right, any TRX in 6000 series  has more dinamic range from  above(confirmed by many contesters) and to prevent damage of the front end (especially in case SO2R or any close RX to TX antennas configuration) ,signal range calculation or assumtion need to be  be executed and  it will protect your budget defenetely.  
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KB4OIF

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Thanks John.  I tend to watch the radio when I am transmitting and listening.  I am in no way wanting to compare the 7300 to the Flex i have on order.  From all the flex owners I have spoken with to all of the research I have done on the Flex, it will be a lot better.  I am keeping the 7300 as a back up and will run it on alternate days.    What I was concerned with is the signal is so strong if I am on the same band as he is, could it in any way damage the flexes front end.  On the 7300, I turn the RF gain back a lot and hit the attenuator.
We at so close that we can use two cans and a string.

KB4OIF
John
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Gary Johnson

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Maybe you and he should just share antennas.  Better antennas and guarantee not to be on same band.
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KB4OIF

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We talked about it Gary.  JK.   His yard is about 2 1/2 times the size of mine.  He has the better antenna at this point.  With warmer weather coming hopefully, I'll try to change that.
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Mack McCormick, Elmer

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John,

May I suggest you consider the Flex 6600 which has integrated contest band filters? I have one (I'm an Alpha tester) and I can run legal limit on one band while listening on another band on a separate antenna. That would help a great deal as long as you're not both on the same band at the same time.

73,

Mack
W4AX
Alpha Tester
(Edited)
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Mark - WS7M

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Not scientific input...  But...

I have Flex-6500 (ya... one of the old models now... LOL) and it uses a 280 foot loop which is my primary antenna.

About 70 feet away I have an 80-10 End Fed antenna that is fairly close to the ground, like 20 feet.  I have my FT-991 on that wire.  If I transmit from FT-991 (100w max) in the same band as the Flex without any doubt the flex sees it and there is overload but surprisingly the signals are still there just difficult to pick out now.

Here is this mornings CWT going on:


And here is with my FT-991 transmitting 30W into the End Fed Antenna just 70 feet away:


As you can see anything close to the center freq of my transmit signal is just gone but there are still some signals you can see.

I try never to do this but I had to find out for myself just how much interference there was.  

Considering this is 70 feet away if your ham friend is like twice the distance and you have at least some frequency separation I think your flex will still be usable.

I can say this is not reciprocal.  IE if I have the FT-991 in receive on 40 and I transmit ANYTHING on 40 with my flex the little pan on the FT-991 goes crazy and all signals disappear.  So I think the flex will perform better than the 7300 in this scenario.
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KB4OIF

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Thanks Mark.  Gives me a look at what  is going to happen.  I think it will be ok.  
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Mark - WS7M

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I also have some hams nearby.  About 1/4 mile south of me is a big station W7RF and he has a gigantic loop he uses, I think its 1100 feet.  Plus he feeds it from a big tube amp.

When he is on I can definitely see him but it looks more like a slightly wider signal and not something like my picture.  So the distance will make a big difference!
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Mark - WS7M

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I should also add that if I have my flex say on 40m CW and I take the FT-991 up to say 7.175 and transmit 100W CW all I see on the flex is the baseline noise go from -120 up to about -116.  All the signals are still there and very workable.

If I transmit 100W on say 30 meters while the flex is on 40m it doesn't even see it.  Again the reciprocal is not true.  Transmitting anything on the flex down on 40m CW causes the little FT-991 to kind of go crazy regardless of the band.  I mean it still works but the pan shows all kinds of stuff.
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Tim - W4TME, Customer Experience Manager

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Mark, that "wider signal", is his transmitter's phase noise.
(Edited)
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Bill Roberts

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That's what I was thinking. A friend with an FTDX 1200 (similar radio) transmits from a mile away, whether he's running 5 watts of 1500, the signal is just wide and noisy. The suppressed wideband is still very visible.
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KB4OIF

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The 6600 is out of my price range Mack.  It's not a big deal as it only happens once in a while.  We both spend a lot of time on 40 meters.  He is a net controller for Southcars on 7.251.  
   
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Tim - W4TME, Customer Experience Manager

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We operate our radios using an antenna at hamfests for demo purposes.  Many times we are in very close proximity to special event stations; some running full legal limit.  The biggest problem we have is not overload, but the horrible phase noise from the transceiver or exciter.  I've gotten fairly good at looking at it and guessing the radio manufacturer by how broad it is.  And no, I am not going to rat out who they are.

If you want to better understand "overload" in a direct sampling radio and how we address it, I recommend this Community post: https://community.flexradio.com/flexradio/topics/adc-overload-myths-debunked
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KB4OIF

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Thanks Tim.  I will read that here in a little bit.  Am really anxious to see the 6400M at the Hamcation.
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Rick Hadley - W0FG

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Get your neighbor to buy a Flex and then share SmartLink login info.  It's a fun way to compare antenna performance.  I have a friend and fellow Alpha tester with a PGXL and contest-grade antennas who lives about 3 miles away.  Sometimes I'll log into his station and mine and do live audio testing, or see how much more I can hear with his big antennas.  I must say I'm extremely pleased with the RX performance of the 6400 I'm testing now, even though I'm limited to my Butternut vertical.
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KB4OIF

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Don't know if he would do that Rick.  He fixes his own equipment.  Loves to work on old gear.  Glad to hear the RX  on the 6400 is good.   I have a 6400M on order. 
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Varistor

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The answer to your question is in the design of the two radios. The reason the Icom tells you that it overloads is because Icom has chosen to have a lot of gain in front of the ADC. That is, the equivalent of enabling the Flex’s preamp. When you factor in the total system gain and the specifications of the two ADCs, you realize that the numbers are the same, within a few dBm.

The 7300 has a very sensitive receiver. Managing RF Gain is the thing to do. Most of my time I keep the dial between 9 and 10 o’clock. Never ever use the preamps below 20. Frankly, I do not use the preamps at all.

How do you know if you have too much RF Gain on either radio? If you see color noise, those random blue pixels, you have too much. Dial down the gain until they are gone.
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Bill -VA3WTB

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Yes, read Tim's post here with Steve's debunk on overload.
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mikeatthebeach .

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I use a Flex6700 here, my Ham neighbor 1 block away and he uses a Icom IC-7300
All I can say that his Icom IC-7300 get more overloading than the Flex6700. Most of
the time I do not even notice he is on the same band with the Flex6700 but he notices me 
a lot !
73 Mike
(Edited)
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KB4OIF

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Thanks Mike.  I will be using a 6400M.  Will be a while because I did not order it till this last Sunday.  

John.
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Ria - N2RJ, Elmer

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I have a CBer who has a ham license up the road. I reckon I cause more grief for him than he does for me. I also run So2R with filters  but even without them and just the flex preselectors I'm fine...
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Varistor

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Anecdotal stories, IMHO, have very little value as they describe the outcome, but say nothing about the environment- antennas, RF gain setting, use of pre-amps, etc. Further, they are truly irrelevant as the answer is with the specs of the ADC and its implementation. As I mentioned before, in the case of the 7300, the ADC has its pre-amp enabled, adding (I don't remember the exact value) 15-20 db of gain. Arm yourself with a calculator, look up the specs, and derive your own numbers based on how the ADC process works.

The bigger picture here is that the radio is only one of the pieces in the overall station design. For example, let's assume for a moment that the 7300 is a total piece of junk and overloads as soon as you turn on the lights. For the past 3 months I have been building an in-band S&P radio solution for my station using a pair of 7300s. In-band radio means that I have two radios that operate on the same band, sharing the same amp and TX and RX antennas. You have have two guys manning each band, one running and the other one S&P-ing. This is nothing new and virtually all winning M/n stations operate this way.

What we learned is that it is not the receivers that matter, but the 1) antennas separation (duh!), 2) antenna polarization (i.e., horizontal vs vertical), and 3) transmitter phase noise. Addressing #1 and #2 allows us to run the 7300s on the same band without any overload issues. You will be amazed what a difference #2 makes. We also compared 7300 vs K3S and did not observe any material differences.

The point I am making is that people spend way too much time staring at specs instead of thinking about station design and interference management. You can make lemonade with the worst lemons with careful planning.

For the record, no Flex rig tells you that it is overloading. As Gerald went on the record on this forum, when SDRs are being used you cannot tell that the rig is overloading; it doesn't just stop working. So anyone who claims "my rig doesn't overload" is simply speculating and does not know for sure.
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Dan -- KC4GO

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Mr. Varistor,
I quote you below. Would be nice to know a real name and and call sign, but guess not your way. 

"For the record, no Flex rig tells you that it is overloading. As Gerald went on the record on this forum, when SDRs are being used you cannot tell that the rig is overloading; it doesn't just stop working. So anyone who claims "my rig doesn't overload" is simply speculating and does not know
for sure."

73's
Dan

 
(Edited)
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Varistor

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What you are showing is the result of dumping too much TX power into the RX input, possibly because of inappropriate antenna management configuration. It takes 15 dBm to see this message and you won't be able to create this signal level under normal circumstances. To quote Gerard:

Another point to make is that all overloads are not created equal.  Overload sounds like an undesirable situation, but a momentary overload has no significant effect on a direct sampling radio.  Why is this so?  The individual data points that make up a signal you are listening to are almost never going to fall in the same time as the overload, statistically.  With a noise blanker, we remove thousands of samples with no negative effects to the signal being monitored and a momentary overload from the addition of many signals summing up will have a much lower effect.  This effect is called "soft overload" because momentary overloads just don't have an impact on the radio.  It takes much more significant and sustained overloads to cause a real problem.  The overload that folks are talking about is a non-event.  Even if it did happen, it's not going to affect the radio's performance.
(Edited)
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Marc Lalonde

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when this pop-up  it far more that overload ;-)

but if radio overload ,and you not notice it  who care  ?  here i never notice it 
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Varistor

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BTW, to keep things in perspective what 15 dBm means- S9 is -73 dBm:

http://www.astrosurf.com/luxorion/qsl-db-power-units.htm
(Edited)
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Sergey, R5AU

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So , Guys, i am very like theory and paractics together

My F6700 (R5AU) -  January 2014, very simple LC oscillyator , Blocking DR = 125db
SSDR Beta 1.0.24
https://www.youtube.com/watch?v=IveXp5Sd3rQ&feature=youtu.be&hd=1

P.S. i am sorry noise level  is too high to clarify RMDR - just 1 transistor and LC  + attenuator  ))


F6500 , Jan 2014 (R9MAB)
ocsillyator level +13dbm via summator with losses not more then 4db  , RF gain = 0




F6300  2014  (RW6MIT)

on 28490 ->   ~400-500 meters Yaesu with amp=~500watts + Double Quad antenna
no dropped signals on 6300



i guess it will be helpfully
(Edited)