6400 sensitivity discussion

Ed Stallman

Ken tnx , very good explanation  . I love playing with SNR ! I also play with SNR on 160 and 80m using and 8 circle array BSEF of short active verticals . with this setup , I get to play with preamps at the array and attenuators at the RXin  of the Flex 6600 and I normally add +8 to 16 db of gain using the Flex menu . With  this setup my S-Meter is just bouncing off of zero making an S1 signal easy copy .
I like to say 160 and 6m is the Chicken and all bands in between is the gravy 
Ed N5DG 

K0FLY

Hi Manuel:

Thanks for the shout out, "Highly Respected" maybe a stretch. HI  HI

73 Gayle

A.J. AJ2I

Ken, what happens is since I find myself using +16 of preamp on 20m and above, I find myself using the AGC-T more like an RF gain which I know is wrong way to use it, to quiet the background noise., even with the EQ 200-2300hz wide. With this setup my AGC-T is usually around 25-30. I know NR is probably more a useful tool.for this, but found the NR is pretty useless feature. So the only choice isto move AGC lower and lower and usually with +24 or +32 at times I have to goto 10.

Bill -VA3WTB

A.J I wonder what the difference is. On my 6500 on 20m, I have +10 gain,  the AGC-T is set to 10. I turned on the NR and set it to 15 and I can hear stations down in my noise floor just fine. The NR cuts about 75% of the noise, it does a nice job.

Lionel

Well said!

Steve - KC5F

Agreed. I'm about to jump in and buy a 6400 or 6400M, but from this and other threads some folks seem to think I should just save money and buy an IC7300 and get better sensitivity, noise blanking or whatever. They haven't quite convinced me, though!

Ken - NM9P

A.J. If you are running the AGC-T down that far below the sweet spot in order to cut down on noise, then you are also cutting lots of the weaker signals out. Which is ok if you are working strong signals and want a quiet background. But if you are listening for weaker signals on a quiet band, you have just cut off everything you gained with the preamp. But these rigs are flexible with lots of controls, so people can set them up any way they want if it fits their needs.

A.J. AJ2I

Gotcha,thanks ken. Will experiment more

VK7WH Winston

Steve, I think the major take out from this is that some people don’t understand that the Flex architecture is different from the radios that the 6400 is being compared with. The Flex RF Amp/Attenuator can be switched in or out on different bands, as required, in order to achieve the best balance between sensitivity and dynamic range. In addition the settings of each band can be recalled each time you return to that band. When I first received my 6700 five years ago, my immediate reaction was that “The receiver is sensational”. I still feel the same way 5 years later. Good luck, whatever you decide to buy Winston VK7WH

James Whiteway

I wouldn't let this or any thread, completely influence me in regards to purchasing a new radio. I had an Icom 7300 for a backup radio and the ONLY thing it had better than my Flex 6600M was the Automatic Notch Filter. Sensitivity is much better on the Flex. Plus, the Flex receiver is much quieter than the 7300. If you are looking for an inexpensive radio that has a good bandscope( but, no external monitor capability) the 7300 is hard to beat for the price. But, a 6400M is a good choice for not a lot more money.( new) It really boils down to what YOU want in a radio. And what you feel comfortable paying. James WD5GWY

Robert Lonn

Tonight I was on 20 meters listening to the Maritime Mobile net.. Here in Ca. it was not that great, the signal was only about a S-3.. So after making all the adjustments I could on my 6600M I decided to switch to Diversity Reception.. One antenna was a Carolina Windom, the other was a 65 foot Longwire.. On went the earphones, and it is such a cool feature, and what was a hard to understand conversation became very clear and readable.. NR was set to about 50%, Bandwidth was 2.3..

So after I heard the part and called the interested party, I switched on my Icom IC-9100 radio to see how it would here the station.. This is not an apples to apples comparison, but the Icom was basically useless.. I am not familiar with what other radios can do diversity like the Flex Can, you need two built in independent receivers, but I presume that when you switch to Diversity you need to Phase Lock the two receivers together, and having a 10 MHz reference input probably helps as well.. You hit the A<>B button to assure both are on the same frequency.

I was using the 6600M stand alone, not using SmartSDR external software, that should not matter much.. I think the 6600M can do this, I dont think the 6400M can do the same function as it does not have 2 SCU???

OH!!! I am still on 2.xx software, do we know if 3.xx has any enhancements to diversity  reception, I know a lot of folks wanted more flexibility on how it operated..

Robert

Steve - KC5F

Thanks, both. I'm a cw operator, and not seriously considering the 7300. And an automatic notch filter wouldn't help much on cw! But from reading everything I can find on the Flex, I have no doubt one would be great for me. Just trying to decide between a 6400M now or a 6400 now and a Maestro later.

Mike-VA3MW

Steve, give me a call at 512 535 4713 and just ring the Sales extension as it rings my phone.  If we don't answer, leave a message as we return all calls.  This is best discussed in a conversation.

Mike 

HCampbell WB4IVF

In another thread Chuck/W9WLX provided a link to an update of the Flex article on setting preamp gain.  Apologies if it’s already been discussed and is old news.  In any case it's interesting and explains reasons for / differences in preamp gain settings between the Flex radios:

Why is the FLEX-6600(M) / FLEX-6400(M) noise levels +10dB higher vs. the FLEX-6500 or FLEX-6700?

Now to the difference between the FLEX-6500/FLEX-6700 and the FLEX-6600. The FLEX-6600 incorporates 7th order bandpass filters on all of the HF contest bands. The 6500/6700 incorporate 3rd order filters on those bands. The 7th order filters provide greater than 50 dB of band to band isolation between the contest bands at the cost of higher insertion loss. This is excellent for Field Day, SO2R, and other contesting configurations. This additional loss is easily compensated with additional preamp gain if required.

Let's take a look at the default preamp gain strategy for the 6400 and 6600 radios. We used the "Rural" noise floor numbers for our calculations to set the default gain for each band. Note that the 6400 filters have a lower loss on the contest bands because it uses 3rd order preselector filters on all bands just as the 6500 and 6700 do. Below you can see the ITU typical noise power in dBm in a 500 Hz bandwidth with S unit call outs in red.

Given the Rural noise floor for each band and the receiver noise for each band we calculated a the target sensitivity to be 10 dB below the ITU typical. We then picked the preamp or attenuation setting. The table below shows the gain setting and the expected MDS with no antenna attached for that setting on the respective radio. If you need more or less gain for your location, antenna and operating conditions use the procedure above to adjust accordingly.

Robert Lonn

TOP SECRET!!!!
FLEX SDR Radio and SmartSDR!! WOW!!! We have come a long way baby!!!

https://www.youtube.com/watch?v=V9xUQWo4vN0

Robert

Clay N9IO

Sending this link to my FB "friends." Thanks Robert.

EDS

sit down with two radios and an antenna switch using the same antenna and switch between two radios with a weak signal and you will have the answer the TS-890 hears better than the Flex 6400, about 4 Db.

John KB4DU

I’m curious. How would I measure this?

EDS

you insert 4 Db of attention when on the Ts-890 and the signal sounds the same on the Flex radio