Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
flex radio musings...




 
The AM Forum
February 25, 2021, 02:16:21 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 [2]   Go Down
  Print  
Author Topic: flex radio musings...  (Read 29585 times)
0 Members and 1 Guest are viewing this topic.
N2DTS
Contributing
Member
*
Offline Offline

Posts: 2307


« Reply #25 on: January 05, 2010, 02:20:12 PM »

Until about 6 months ago, the idea of computer junk in the shack really turned me off, till I got the sdr-iq.
Now I find the sdr stuff the most interesting part of the hobby.
I think they could do wonders with the stuff, but its all in the hands of small companies with limited resources.

I wish I understood the software, if I was 18, I am sure I would be into it, but now it makes my head hurt along with math....

The flex 1500 is going to have much reduced spec's but still likely much better than any vintage and most modern receivers.
I think I will get one to listen on in the den.
If they ever come out....its like Apple starting in the garage....a ways to go...

Hey, maybe I should buy flex radio stock!


Brett
Logged
N2DTS
Contributing
Member
*
Offline Offline

Posts: 2307


« Reply #26 on: January 05, 2010, 02:27:48 PM »

I am not buying it.
If a little is good, more is better! Its the American way.
More food, more beer, more tubes, MORE POWER, it was Scott, an American company who sold 'the worlds most powerful receiver'!
8 cylinders is not enough, we want 12, or 16, or 32.

So what if it distorts a little, we get more!

Brett

Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2367


Making AM GREAT Again!


« Reply #27 on: January 05, 2010, 03:05:35 PM »

How do the CBers get Flex to TX out of ham bands.
Flex software guys are not interested in AM so it is set to text book
100%

AFAIK, it's "unlockable", to general coverage TX.

As I said, I've never played with them, but I did send an email to a friend who started on the 1000, and recently sold his 3K Flex.

--Shane
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2367


Making AM GREAT Again!


« Reply #28 on: January 05, 2010, 03:09:45 PM »

What you propose is not "fixed but lower gain." You are proposing to have less gain on the negative cycle than on the positive cycle. This means the gain changes every time the waveform crosses the zero axis. In other words, it does change with time. Further, a discontinuity like this will be very audible.

Which is called compression.

Limiting implies Brick wall, a la diode peak limiters.  Compression implies a non-linear (usually???) reduction in gain due to an external circumstance (audio signal, overdrive, etc).

At least, that's the way I look at it.

--Shane
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2367


Making AM GREAT Again!


« Reply #29 on: January 05, 2010, 03:15:41 PM »

Quote
One thing that would be interesting would be for all stations in a QSO to run DSB reduced carrier, and receive with a synchronous detector.  The DSB-RC could be generated with an analogue transmitter or SDR rig.  The idea would be to run double sideband, with just enough carrier to give the synch detector something to lock onto.  The  received signal would sound identical to a full  carrier AM signal with the synch detector, but to receive it without distortion on a conventional receiver would require receiving one of the sidebands in SSB mode.

Years ago when I worked at Harris RF Communications, our transmitter and receiver systems were capable of that. They could run USB, LSB, ISB, 4ISB, full carrier AM or 'pilot carrier' which was -26db down to synch up with the receivers at the far end. On the sites I helped design and build, we typically used that in a 4ISB mode, 4 independent 3 khz sidebands, -26db carrier. Lower Lower sideband, Lower sideband, Upper sideband and Upper upper sideband. Typically 2 voice channels on the top two, and 2 RTTY channels on the bottom two. The matching receiver had 4 ISB capability also (RF550) and 4 audio outputs.

From time to time I've wondered about doing ISB with voice on one sideband and sstv on the other so a qso could be ongoing while the pictures were being exchanged in the background on the other sideband. I bet that wouldn't be that hard to implement in a flex system - might be an interesting market niche for them.  How would the ssb folks handle that - we'd still  be using two sidebands, but be running ssb!  Shocked

I'm a very new convert to the flex-sdr realm having been curious for a while and having received an SDR-IQ from Santa.  Grin Now I find myself scanning the for sale ads for used gear, or contemplating a flex-1500... I wonder how well 5 watts will drive a Titan 425?

Myself and another person have done something similar with our "Hi Fi" modulators.

Essentially, it's a Class A series modulator high level modulating a single device, then we feed it into linears to increase the Pout.  I have done a similar design for HIGH level, 16 transistor amplifiers at 12 volts before.  Lots of pass transistors.

BUT, I did find that when using computer injection, it was entirely feasible to FM modulate a 30 Khz tone.  Something inaudible.  It wreaked havoc with the other operators, I could play music, in decent fidelity (limited to 10kc) on an AM channel any amount of KC away.

Boy, it SURE did make the amplifier heat up, though.

I also used negative peak limiting in the modulator, which in effect gave me supermod.  It would make the SB220 have a 75 watt carrier, increasing to 750 PEP.  AVG Pout was in the neighborhood of 500+ watts.  I've uploaded audio clips of it, albeit I was at an S1 to S7 at the RX end....  Depending on mod percentage.

This was 13 devices in the "audio rack", using Reaper or Adobe Audition 3.0 as the audio processors, and both included and purchased plugins. 

Anywho, another musing of "fun" on AM with multiple channels...  I guess my method was SCA, though?

--Shane
Logged
w1vtp
Member

Offline Offline

Posts: 2625



« Reply #30 on: January 05, 2010, 04:57:35 PM »

<snip>...click and you are right on freq.
And, the ssb signal can sound very good, better than some AM,  <snip>...
I had one good ssb qso, talking with a guy on a tug boat in Boston, talking about old AM rigs, flex radios and tug boat stuff...

I dont think ssb is a bad mode at all, its just the people on ssb that ruin it...

Brett


Eric WB2CAU and I do HIFI SSB (Slopbucket) with some regularity and it sounds just as good as the counterpart in AM.  We both run Flex radios and have calibrated our timebases.  All we have to do is set our xmit BW to whatever we agree on (5 KC for example), set our rigs to the same frequency, set the AGC for "Long" and it's armchair HIFI audio.  I'd upload an example of the audio but I'm not using that computer just now.

Al
Logged
K5UJ
Contributing
Member
*
Offline Offline

Posts: 2845



WWW
« Reply #31 on: January 05, 2010, 06:26:48 PM »

Eric WB2CAU and I do HIFI SSB (Slopbucket) with some regularity and it sounds just as good as the counterpart in AM.  We both run Flex radios and have calibrated our timebases.  All we have to do is set our xmit BW to whatever we agree on (5 KC for example), set our rigs to the same frequency, set the AGC for "Long" and it's armchair HIFI audio.  I'd upload an example of the audio but I'm not using that computer just now.

Al
Al, without having heard you I must nevertheless disagree.  It is impossible for SSB to ever sound as good as AM potentially can sound, because a sideband with no carrier is not giving a faithful representation of the baseband tx audio.   What you have is a complex cw signal that varies continually in frequency offset from an imaginary carrier (to represent tx audio frequencies) with volume of the original audio represented by the RF power in the various cw signal frequencies.   This is why analog diode clipping of the audio peaks is okay for AM but it isn't for SSB.  With SSB if you clip the analog audio you wind up txing something like a cw sig with an instantaneous rise (key clicks).   I'm getting into this only to try to illustrate why a SSB sig. doesn't represent audio the way an AM signal does.     Recently, a certain ham radio equipment company has in my opinion, irresponsibly reissued an old speech processor design for SSB that employs clipping by converting the mic audio to RF and filtering it before demodulating it back to AF.  They employ clever wording to make it sound like this is the best thing going of course, ignoring DSP based compression, and multi-band AF processing.  They claim as much as 6 dB increase in average power.  If ur average is 20 watts with a 100 w. SSB rig, that would be almost 80 w.!   It is impossible for that to:  A. Sound good and B. not cause garbage QRM.
</soapbox>

73

Rob
Logged

"Not taking crap or giving it is a pretty good lifestyle."--Frank
K5UJ
Contributing
Member
*
Offline Offline

Posts: 2845



WWW
« Reply #32 on: January 05, 2010, 06:40:17 PM »


The bigger thing to keep in mind is that negative peak limiting or other magic boxes are usually not needed to run extended positive peak modulation. Just set the polarity of your audio system to take advantage or the natural asymmetry of your voice. I can get 130-150% positive modulation without any special processing. As Fred noted, you just need a transmit system that can produce such modulation.



There are a couple of problems with that however (to my thinking):  1.  Not everyone has a lot of voice asymmetry.   2.  You can run pos. peaks to the moon but as someone, Fred I think, mentioned you eventually run (okay some of us run  Grin) into the limits of the transmitter components.   It's fine to be asymmetric in whatever way you want to do it, but it's also important to build high average power in the sidebands by using tight gain reduction peak limiting so you can compress then drive the final limiter to get dense loud audio that still sounds pleasant.   I would rather have a smaller peak to average than huge peaks with low level vowel sounds.
Logged

"Not taking crap or giving it is a pretty good lifestyle."--Frank
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2367


Making AM GREAT Again!


« Reply #33 on: January 06, 2010, 03:56:08 AM »

The flex 1500 is going to have much reduced spec's but still likely much better than any vintage and most modern receivers.
I think I will get one to listen on in the den.
If they ever come out....its like Apple starting in the garage....a ways to go...

Look at the WonderRadio.  1/2 watt output Flex radio, in kit or assembled form.

I spoke to one of my friends who used the Flex for years on HiFi AM.  His answer, honestly, was "Buy an Omnia Processor".  He LOVES... I mean L.O.V.E.S. his Omnia, and he used that, and the Flex.

I'm still waiting for one of the big boys in the northeast to answer me about his setup....  Although I'm starting to hear more and more musings about using the AM setup as stock, and more people are running to a second computer to do audio processing.


--Shane


--Shane
Logged
Steve - WB3HUZ
Guest
« Reply #34 on: January 06, 2010, 10:09:43 AM »

Different levels of the same thing - both are a nonlinear gain curve.

What you propose is not "fixed but lower gain." You are proposing to have less gain on the negative cycle than on the positive cycle. This means the gain changes every time the waveform crosses the zero axis. In other words, it does change with time. Further, a discontinuity like this will be very audible.

Which is called compression.

Limiting implies Brick wall, a la diode peak limiters.  Compression implies a non-linear (usually???) reduction in gain due to an external circumstance (audio signal, overdrive, etc).

At least, that's the way I look at it.

--Shane

Logged
Steve - WB3HUZ
Guest
« Reply #35 on: January 06, 2010, 10:24:05 AM »

I agree. I was not proposing doing nothing to increase the average level. But if asymmetry already exists, use it to your advantage - don't waste time on circtuits or processing to create it if it already exists. Once that's set correctly, process away to get the average level up.

Just remember, you can never increase the average level of the negative modulation beyond 100 percent, but you can on the positive peaks. Which will be louder, a station with both the positive and negative peaks at 90 percent on average or the station with the negative peaks at 90 perrcent average and the positive peaks at 150 percent average?

Yes, there are limits - how much your transmitter can handle, and how much the receiving end can handle (based on AGC and the detector). I keep my positive peaks below 150 percent, usually in the 120-130 range. Most receivers seem to deal with this OK FB. YMMV.

BTW, you sounded very good on 3885 last night. Hope to hear you again soon.


The bigger thing to keep in mind is that negative peak limiting or other magic boxes are usually not needed to run extended positive peak modulation. Just set the polarity of your audio system to take advantage or the natural asymmetry of your voice. I can get 130-150% positive modulation without any special processing. As Fred noted, you just need a transmit system that can produce such modulation.



There are a couple of problems with that however (to my thinking):  1.  Not everyone has a lot of voice asymmetry.   2.  You can run pos. peaks to the moon but as someone, Fred I think, mentioned you eventually run (okay some of us run  Grin) into the limits of the transmitter components.   It's fine to be asymmetric in whatever way you want to do it, but it's also important to build high average power in the sidebands by using tight gain reduction peak limiting so you can compress then drive the final limiter to get dense loud audio that still sounds pleasant.   I would rather have a smaller peak to average than huge peaks with low level vowel sounds.
Logged
K5UJ
Contributing
Member
*
Offline Offline

Posts: 2845



WWW
« Reply #36 on: January 06, 2010, 12:48:14 PM »

I agree Steve, and thanks for the comment on the audio here.  I also run about 130% positive (if the specs on the Inovonics 222 can be relied upon).   I may be out for a few days as I get this buzzard transmission heating problem nailed down and fixed.
Logged

"Not taking crap or giving it is a pretty good lifestyle."--Frank
Pete, WA2CWA
Moderator
Member

Offline Offline

Posts: 7833


CQ CQ CONTEST


WWW
« Reply #37 on: January 06, 2010, 01:38:40 PM »

[
Look at the WonderRadio.  1/2 watt output Flex radio, in kit or assembled form.
--Shane


If you're referring to the one in India, they're out of business.
Logged

Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
K3ZS
Member

Offline Offline

Posts: 1036



« Reply #38 on: January 07, 2010, 02:05:04 PM »

Referring to K5UJ's comment on RF speech processing,  Angelo W8ERN, an active oldtimer (but not on AM) has the most effective and good sounding standard bandwidth SSB that I have heard on the air.   When people comment on his great audio, he explains that he is using an RF speech processor.    I don't know if he designed it himself or bought it.   By the way, he is one of the designers of the AF-67 when he worked for Multi-Elmac.   

Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2367


Making AM GREAT Again!


« Reply #39 on: January 07, 2010, 02:09:53 PM »

[
Look at the WonderRadio.  1/2 watt output Flex radio, in kit or assembled form.
--Shane


If you're referring to the one in India, they're out of business.

Well.  Thanks for the bad news.  That's who I was referring to.

Too bad, was a nice little kit.

--Shane
Logged
KF1Z
Member

Offline Offline

Posts: 1796


Are FETs supposed to glow like that?


« Reply #40 on: January 07, 2010, 02:26:10 PM »

Not only went out of business, but did not deliver radios that were paid for.

And did NOT refund the money!


The radio did not work well at all...
Terrible layout, bad bad construction.

don't waste any money on it it you find one used!

Logged

N2DTS
Contributing
Member
*
Offline Offline

Posts: 2307


« Reply #41 on: January 07, 2010, 03:07:26 PM »

If it seems to good to be true, it is likely a rip off.
Like the 'new' globe king 500...remember those?

Brett
Logged
W3RSW
Contributing
Member
*
Offline Offline

Posts: 3288


Rick & "Roosevelt"


« Reply #42 on: January 07, 2010, 03:34:44 PM »

Anyone interested in a Wilsonski 2000A?   SDR, 250MHz DDS, 32Bit FGPA, 1.5kwpep, 400AM  all T/R relays built in, 4 independent receivers, 10Hz to 148Mhz, built in ant. tuner, good for 20:1 all bands.   Oh almost forgot - built in Mac.
Lifetime guarentee,
..no spurs, no gears, no fears...
Logged

RICK  *W3RSW*
KF1Z
Member

Offline Offline

Posts: 1796


Are FETs supposed to glow like that?


« Reply #43 on: January 07, 2010, 03:43:41 PM »

Anyone interested in a Wilsonski 2000A?   SDR, 250MHz DDS, 32Bit FGPA, 1.5kwpep, 400AM  all T/R relays built in, 4 independent receivers, 10Hz to 148Mhz, built in ant. tuner, good for 20:1 all bands.   Oh almost forgot - built in Mac.
Lifetime guarentee,
..no spurs, no gears, no fears...

Interest and reality may be slightly seperated in this intance...  Grin

(The deal-killer is the built-in Mac)
Logged

W3RSW
Contributing
Member
*
Offline Offline

Posts: 3288


Rick & "Roosevelt"


« Reply #44 on: January 08, 2010, 07:46:35 AM »

Oh that was a market specific come-on for Steve.
In the not so fine print you can alternately select a Winnogoes machine, 4Ghz processor , 10gig mem, 1Ghz FSB, 3 ea. 10TGs hard drives, and two 23" monitors.  Uh, ashamed to say the printer is extra.   urk.
Logged

RICK  *W3RSW*
Pages: 1 [2]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.092 seconds with 19 queries.