6300 Dynamic range question

Alan Nusso, N4BV

Tim are there any preliminary specs for receiver dynamic range and third order intercept point  for the 6300? I was wondering how not having preselectors will affect overall dynamic range. Thanks!

Steve-N5AC

Superhet receivers have limited dynamic range and are forced to use filtering techniques at the front end and each stage to prevent overload.  The FLEX-6300 is a direct sampling receiver and by nature will consume the entire HF spectrum at once.  The overload point is simply the max voltage input to the A-to-D Converter (ADC) which is +7dBm (5mW) for the FLEX-6300.  This is a very large signal in the front end of the receiver and it is rare that you would encounter this level of signal. 

You could see a signal like this when there are other strong transmitters co-located with the FLEX-6300.  This is design difference in the FLEX-6500 and FLEX-6700 -- they both have preselectors. You have to decide for your environment if they will be necessary.  If you are going to run a multi-multi contest station, you will almost certainly want the preselectors.  If you are running the FLEX-6300 from your shack and do not have a next door neighbor that is a ham and runs power, you are much less likely to need preselectors.  At my house, I would never need them.

There is a broadcast filter in the FLEX-6300 which is the most likely place to find large signals so these signals will be knocked down considerably unless you are listening in that portion of the band.  If you need a more definitive answer, you can take readings at your operating point -- connect a power meter that is band limited to 1.8-54MHz and see what the total power reading on the meter is or alternately use a spectrum analyzer.  For reference, a +7dBm signal is S9+80dB!

Stan VA7NF

Steve, I am looking using my 6700 as a all-band concurrent usage monitor utilizing one SCU with 4 panadapters covering all of the 40, 20, 15, 10M bands connected to a separate receiving antenna.  Obviously this will be in WIDE mode.  (The second SCU + antenna will be a 6M and 2M VHF station).

Please confirm the pre-amp at -10 setting is before the ADC and if inadvertently switched to +30 it will clip and not pose a threat to the ADC.

Another advantage in multi-multi for the 6500 and 6700 is the use of Ant Out - Ant In loop to insert RX only filters or attenuators.  As said before, the RX has overload protection but it is best not to over exercise that feature.

Steve-N5AC

Stan, yes you will be in WIDE mode. You will not hurt the ADC, generally. Overload will start at +9dBm or so in the 6700. It should degrade gracefully for a few dB above that and then at about +16dBm the radio will disconnect the antenna from the ADC to prevent damage. As I recall damage is around +24dBm but you should be protected against this.

Peter Driessen

Is there any significant degradation in dynamic range by using the lower spec phases noise oscillator in hype 6300?

W9OY

I used my 6300 to see if any signals were even close to crunching the ADC. The strongest signal, radio Havana on 6 MHz (I live in fl 700 miles from there directly in their beam path). They were still 47 dBm below +7. Even the multiple 50 kW broadcasters around me were dramatically weaker than radio havana. I was initially worried about this issue but in practice it is a non issue for any but a handful of people. Steve does the 6300 self protect? 73 w9oy

Gerald-K5SDR

Yes, all 6000 series models self protect.

Howard -W6HDG

I have a 6300 and I worked a friend 5 blocks away last night on 10 meters SSB. He was running 100 watts and his signal was totally distorted for the first 3 seconds of each transmission and then it cleared up. I thought HE had a problem so I switched to my Yaesu and he sounded fine. So I imagine my 6300 was experience front end overload? He lowered his power to 10 watts and it still occurred but not quite as bad. I did not have the +20 db set on RF gain and my AGC was set to medium and level 50. Any tips on how to remedy this on a 6300? I didn't check how broad his signal was but it looked fine on the display. So I don't think this would be an issue during contests. I have 3 very active hams in the neighborhood.

W9OY

The AGC should be set to the minimum it can be set and still have band noise.  My typical on 10M is 16 - 20 with no preamp.

Steve-N5AC

You can probably discern this in a lab.  In the real world, you are not likely to notice.  Both have excellent low-noise oscillators

Gerald-K5SDR

Howard, what was your friend's signal strength on the panadapter?  Overload on the 6300 is about +8 dBm.  I doubt he was that strong.

Howard -W6HDG

Hi Gerald. No he was not anywhere near +8 dBm. So what might cause distortion that self clears after 3 seconds? My NB may have been on but not set too high.

W9OY

I think its likely you had the NB turned on.  There is no reason for the front end to fail for 3 seconds.  There is a reason for the NB to train itself on the noise.  That probably takes a couple seconds and was the first thing I thought of when you listed your report.  I have seen the NB take a couple f seconds to train itself.

I did a test using a external xmtr on my back yard vertical running 40w and using my front yard vertical as the rx antenna on my 6300.  The antennas are 175 ft apart  I was still only at -5 dBm on the rx and was able to copy signals well below -100 dBm both cw and ssb with no distortion

http://sdr-w9oy.blogspot.com/2014/05/crunch-time.html

The spikes from the K1 are there regardless even at 0.1 W.

73  W9OY

Takeshi Yamada

I think that it is yet because of NB turn on.  Try turn-off NB.
I have several active Kilo-watters within 5 miles and they are worse than noises near by when I turn on NB.  Without NB, they sound as they are.

Howard -W6HDG

Well, I've determined that SmartGuys run SmartSDR.  You are all correct - it is indeed the NB giving me the issue.  I'm very relieved that this is not front end overload per se.  Confirmed today with a different ham friend a few blocks away who also bought a 6300 at Dayton.  So we worked each other 6300 to 6300.  We both experienced the 3 seconds of distortion which clears during each transmission - if the NB is on and even if the NB is set as low as 10.  Our analog radios (Yaesu FTdx3000-me and FTdx5000-him are immune to distortion except for very high levels of NB).

Hopefully this can be improved in future software without decreasing NB effectiveness (which is just terrific on the 6300 BTW).  

And one more totally unrelated comment.  Some say that releasing PowerSDR into the public domain created competition for Flex. And indeed the software my friend and I were using with our Yaesu's + LP-PAN was NaP3 which is a public domain variant of PowerSDR.  But our using NaP3 was not a bad thing.  It became the training wheels for our discovery of the virtues of FlexRadio! Flex, in the end, is creating customers who understand the technology and want the envelope pushed as fast as possible.  Hopefully the 6300 introduction will create the cash flow to allow Flex to speed up software integration.  I'd personally not like to have all these icons in my tray for the utilities that give this radio more functionality such as SmartCAT, DAX, DDutil, SD-Bridge, Voice keyers, etc.  Howard W6HDG