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Flex 1500 as a receiver




 
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N2DTS
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« on: November 18, 2014, 10:44:23 PM »

I picked up a used flex 1500 cheap, $250.00 off the new price and put it in place of my sdr-iq.
For the price, it seems very good as a receiver and as a qrp CW rig.
There is not much point in a 1 watt carrier AM rig, so I would not bother with that, but the receiver seems to work very well for such a small cheap sdr.
My sdr-iq is ok, but as a 14 bit unit its got some hash on weak signals.
The 1500 has better spec's although hardly the best that you can get these days.

It uses the common USB interface, but on many computers, the delay through the USB system has a good amount of delay. That varies a lot depending on the computer.
The other old flex radios used firewire that was much faster and had less delay on a good computer, and the radios that use ethernet seem to have almost no delay.

But for a small cheap unit, it works very well as a receiver.

One advantage is its easy to get working, no messing with the software really, just install and use, and power sdr is very ham friendly.
It does not cost $3000.00 like a 5000, or have a loud fan like the 3000, its silent, no fans.

Not sure I would pay $700.00 for a new one, but a cheap used one seems to make a nice receiver and a qrp CW rig.
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w1vtp
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« Reply #1 on: November 19, 2014, 11:32:07 AM »

Brett

I am using a Flex 1500 as a receiver in my class E station and am quite satisfied with it.  I will agree that the latency is an issue.  I have a 4 core 3.3 GHz clocked computer and it still has issues with latency.  I was told that the 1500 uses USB 1.1 rather than 2.0 or better yet 3.0.  I'm disappointed that Flex decided on this version of USB which runs at a snail's pace when compared to the faster versions of USB.  Better yet, why wouldn't Flex have offered as a factory install an upgrade to an Ethernet connection.

When I first started using the 1500 with the "E" transmitter I  used the transmitter out to drive the analog --> digital drive converter.  Most of the time that was just fine. But once in a while I would have transmitter reset problems where the protection circuitry would shut down the transmitter and I would have to release and go to transmit quickly in order to continue transmitting. 

At first I thought I was experiencing either an overload trip or that the protection circuitry was just set too close to the trip point. But it turned out to be that the 1500 was dropping out for a split second and that would cause the TX --> RX trip.  Since then the class E transmitter has been reconfigured to a standalone VFO / driver hookup and I no longer have that problem.  Lesson learned?  I wouldn't depend on the Flex 1500 for critical drive requirements.  On SSB most likely no problem - we're talking probably a 100 mS dropout - I never tried to catch the dropout on a scope. Again, that's probably not a problem on SSB but for my application it is a problem.  Dunno how that dropout problem would translate to, say, a class C transmitter with  grid leak bias or a combination of grid leak and stiff cutoff bias.  It might be a problem with the modulator having no load under maximum a modulation condition for a split second.

Currently, I am running the 1500 with the power turned to zero and toggling the 1500 from RX to TX in the normal way to mute the receiver and am experiencing no problems.  I like the 1500 as a receiver --- the front end is NOT bulletproof but you can select a 10 dB pad which will take care of most receive conditions.  I wouldn't consider the 1500 ready for the highly competitive DX scenario but that's a subject for another time.

Al


* PSDR (1) SYSTEM.jpg (56.79 KB, 1179x788 - viewed 385 times.)
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N2DTS
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« Reply #2 on: November 19, 2014, 01:36:47 PM »

Yes, usb of any kind is a poor choice, but very common, so that must be why flex went with it.
Firewire is a problem all in itself, Ethernet is the way to go I guess.

Most computers use the usb for the mouse and keyboard, and its all got a slow and low priority, and that may cause dropouts. Maxing out the buffers helps but adds a lot of delay.

I could get voice to work ok on TX, sounded good, with little delay, not enough to bother me when monitoring myself, but I did have some small glitches with the buffers set that way.
The 1500 also puts out some trash, so its likely not a great exciter for QRO.

It seems fine for sending CW with a key at 15 or 20 words per minute, and makes a good receiver for any mode if you do not mind the delay.
I leave all the receivers working on TX so I can monitor my TX signal in various ways, on the band scope, on the o scope, audio if I want, and to make sure I am on the same frequency as everyone else, or drifting.

The sdr-iq will overload way before the 1500, so its better, but even so, on TX at 300 watts carrier I get S9 on the meter of the 1500, right in the ballpark.

My homebrew receivers had the edge on weak signals compared to the sdr-iq, the 1500 should be better.

List of things no longer made:
rf space sdr-iq,
rf space sdr-14,
flex 3000,
flex 5000,
flex 1500 (most likely very soon).

I would like a net sdr (rf space) but its $1200.00 and just a receiver....

 
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WD5JKO
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« Reply #3 on: November 19, 2014, 01:48:15 PM »


 I have a Flex 3000, and all in all after a lot of trials with it I am still glad I purchased the thing. It was impulsive, and done.

The thing you mention Al about AM carrier dropping briefly is pretty common with the 3K and 5K series rigs, and from what you say, the 1500 series as well. The common item is PowerSDR. In my case, I was using a computer with limited resources, and I fixed the problem by relocating my WiFi antenna to get 4 bars instead of one. Yes anything that takes sudden system resources can cause a large PowerSDR latency, and a resultant drop out. Could also be a CPU that throttles the clock rate depending on load. All kinds of memory resident stuff like software looking for an update should be turned off by editing msconfig. The 1500 using USB instead of Fireware is interesting.

I had a tough issue where I went round and round. My 3K would gargle during transmit, and even sometimes on receive. Then PowerSdr would kick out. Then it worked for a while, and then it might stay working for a mere 10 seconds. Contacting Flex since it was still under warranty was interesting. It got a lot of canned responses to do this, do that, check this, check that. Everything was coming out fine until I mentioned I was running a 1 core AMD processor, and server 2003 operating system. The case was closed pending me getting a supported computer and operating system.

So I got a really nice computer that has gobs of horsepower. PowerSdr runs at 2-3% CPU utilization, and boots in 4 seconds. Great right? Nope, same problem as before.  SH_T!! Turned out to be a bad E_bay $5 Firewire cable.  Cry
I'm not unhappy though since I wanted to upgrade the shack computer for a long time. I'm about $800 poorer now that the XYL doesn't know about....

Jim
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N2DTS
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« Reply #4 on: November 19, 2014, 02:18:47 PM »

Yes, but its fun, no ? Reminds me of the windoze 3.11 days, always upgrading and replacing the computer to get games to run well, sort of fun in itself, if a bit expensive.

I used various computers to run the flex stuff (and the other sdr stuff) and all it does is run the radio, its not hooked up to the web and has no extra things running, and it was totally trouble free and stable.
No anti virus, no wireless lan, no windoze updates, just the radio.

The computer boots up quick and loads the sdr program quickly, and the sdr-iq had a big advantage in speed to working, the radio powered up with the computer, and sdr-radio loads fast, then click start and its working. Power sdr is slower, you have to power on the radio manually and the software is slower.
Like letting the tubes warm up.
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« Reply #5 on: November 20, 2014, 08:36:58 AM »

Fooled around last nite, tried putting the 1500 into the 2x 4x150 rf deck and modulating it, but that did not work as I have fixed and grid leak bias and I could not adjust the fixed bias voltage, its fixed!
I was trying to make it work as a grid driven linear, just for fun.

Ran it barefoot on 80 meters with various buffer settings and usb ports, and it often has those micro glitches if the buffers are set low, they seem to go away when they are increased.

There are a bunch of settings, USB priority slider, the TX and RX buffers, the audio buffer.
My computer has a fast 4 core processor but the rest of it is poor as its a small form factor computer, almost like a lap top, so that may be why the usb system is so poor.
The computer worked fine with the firewire, no glitches, no delay.

I thought this stuff was getting cheap, but a mid range desktop is around $700.00....

I compared the 1500 to the homebrew receiver on weak signals, and they are equal, at least on 80 meters at night on signals that were at the limit of copy.
Noise and fidelity are equal to my ears, the psdr sync detector is annoying with its loud swoop tone when someone is off frequency. Other programs (hdsdr and sdr-console) do not do that.
I did not hear any improvement using the sync detector, sdr-console adds noise under sync detection on weak signals with the sdr-iq, I did not notice that on psdr and the 1500.

I also tried running both the sdr-iq and the 1500 at the same time, I could do it, but the audio of the sdr-iq went away. The audio for the 1500 comes out of the radio, the audio for the sdr-iq comes out of the computer, so I wonder why it went away.
Its fun playing with this stuff, no heavy iron and high voltage...




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W3FJJ
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« Reply #6 on: November 20, 2014, 09:56:31 AM »


I bought a used Flex 1500, I really like the RX, and got
good reports with it on AM transmit, despite the narrow
bandwidth.. I ran two amplifiers,  flex into Hercules into Drake L7

My problem I had with it, probably due to my old PC,
a dual core laptop running windows 7, but has a lot
of stuff installed on it, and could use a fresh reinstall
of window,  I had to wait for laptop to completely
boot up, like three minutes, before I could run power
SDR otherwise I would get popping noise in the audio.. Also
the longer it was running the worse the latency would get
with PTT line, it was gradual thing but after a couple hours, it would be
like a 1/2 second..


It was fun to fool with, but it
was frustrating with the little quirks, I sold it a few months later
and pretty much got all my money back out of it..

Im sure another SDR will be in the future,
Cool technology.. Right now Im using
a homebrew down converter off 455khz off my NRD-515, into
sound card, using power SDR 1.8, I love the Synch Detector and Filtering..
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w1vtp
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« Reply #7 on: November 20, 2014, 10:23:58 AM »


<SNIP>
...........
My problem I had with it, probably due to my old PC,
a dual core laptop running windows 7, but has a lot
of stuff installed on it, and could use a fresh reinstall
of window,  I had to wait for laptop to completely
boot up, like three minutes, before I could run power
SDR otherwise I would get popping noise in the audio.. Also
the longer it was running the worse the latency would get
with PTT line, it was gradual thing but after a couple hours, it would be
like a 1/2 second..


It was fun to fool with, but it
was frustrating with the little quirks, I sold it a few months later
and pretty much got all my money back out of it..

Im sure another SDR will be in the future,
Cool technology.. Right now Im using
a homebrew down converter off 455khz off my NRD-515, into
sound card, using power SDR 1.8, I love the Synch Detector and Filtering..


I had a similar problem with my 1500.  I get pretty good success if I turn off the 1500 so that while my computer is booting up it doesn't see the 1500.  Once things settle down, I turn on the 1500 and greater than 90% of the time, I get a good connection from the computer to the 1500..

If I had to do it over again, I might have gotten  another mfg SDR.  Most of the time running the 1500 is a good experence

Al
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« Reply #8 on: November 20, 2014, 10:52:49 AM »

With any of these SDR-type rigs and softwware, there is a program that gamers use that sometimes helps to reduce latency and dropouts. It's called GBOOST, http://www.gzero.com/gboost/home.html Basically, when run, it disables a lot of background processes and calls that can disturb the normal running of SDR software. You can also tailor it if there are some programs that you need to run while the SDR stuff is running. I run it when I'm running PowerSDR on a dual-core Vista machine. Seems to help quite a bit to eliminate dropouts, software hangups, latency, etc.
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« Reply #9 on: November 20, 2014, 01:03:40 PM »

I will have to try that.
But yes, if you want things to work well and in real time, you need a good computer with nothing else on it.
Its best if its not hooked up to the web, and has NO other software on it.

I have gone in services and turned things off, there is a LOT of stuff that runs in the background on a normal computer.
Windows updates, adobe updates, updates for other software, lan connection stuff, windows backup and restore points, a system that allows diagnostics, anti virus software and updates, hard disk mapping, and who knows what else.

I have had 100% success and no problems because the computer does nothing else but sdr.
If the computer is poor, its got to be slow/big buffers/high latency but it should be stable and work.
A real fast computer will do it all with ease, I had a good one from Neil who builds them for flex users.

As a receiver, the 1500 seems to work great on a set up for sdr cheap computer, not a lap top, lap tops are very poor performers.

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« Reply #10 on: November 22, 2014, 05:16:07 PM »

40 meters was a real mess today, 10 meters was way open, so I guess 40 had to be bad.
I was in a qso where everyone was very hard to copy, and the home brew rx still has the edge, not sure why.
It just seems to pull audio out of the hash a bit better.
40 meters seemed like everyone was running 5 watts today.
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« Reply #11 on: December 03, 2014, 09:29:59 AM »

The street lamp outside my house crapped out and now generates nasty impulse noise.
The noise blankers do not seem to work very well on any of the sdr radios that I can tell.

On very weak AM signals, the homebrew RX seems quite a bit better, there just seems to be a low level hash in all the sdr's that impacts weak signal work.
On strong signals, the sdr radios seem fine to very good, but not so great (on AM anyway) with very weak signals.

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« Reply #12 on: December 05, 2014, 08:09:29 AM »

Been switching between the 1500 and the sdr-iq, along with the homebrew.
The homebrew still wins with pulling out weak signals, I think because it has almost no self generated noise.
The 1500 is next, the sdr-iq is poor with weak signals, lots of background hash.
During TX, the 1500 has all sorts of spurs and odd things on the display, the sdr-iq does not, the display acts like a high quality spectrum analyzer.
Both are hooked up the same way, to the same computer, using the same cables and so on.
The 1500 is sound card based (built in), the sdr-iq is a 14 bit direct digital conversion setup.
The 1500 has its own dac (digital to analog converter) built in, the sdr-iq uses the computer sound card.

The home brew is tubes and feeds right into the Marantz amp.
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