Greetings Ian and all,
Yes that was my post and YES, the spur DOES exist with the 5000. I cannot
speak to the 3000 as I have no experience with it.
Allow me to tell you my actual, documented on the air experience with this
issue. First, if you look at the ARRL product review you can see the spur on
the spectral display about 2.4 KHz below the fundamental. It is way down
from the fundamental and during normal, rag chew "how great is my audio" 100
watt operation it will most likely never be noticed.
Now, enter an arena on 160 meters working DX where you will run an
amplifier, sometimes a gain antenna and most likely be using low noise
receive antennas (I run 1.5 KW and Beverages & vertical array rx antennas as
most DX'ers do on 160). Early one morning, a DX station was listening up 2-3
KHz. I was up about 2.5 KHz calling and was slammed on the air and on the
160 meter chat reflector for calling right on the DX stations frequency. Of
course, this wasn't the case however I investigated and discovered that the
spur does in fact exist and under many conditions WILL be heard by other
stations. This is a hardware related spur with the 5000 and not with the
PowerSDR software.
W5UN (who was aware of it as well), W5LUA and I ran tests to try to resolve
the issue but were unsuccessful. The spur was clearly present and could be
heard in all tests. Flex was notified but frankly, with all due respect to
the folks at Flex, it took a bit of explaining and help from N4HY to make
them understand why this was an issue. The 160 meter contest was coming up
and I dearly wanted to use the 5000, however attempting to use it with the
spur issue would have been suicide for W5ZN. My buddy Bob McGwier, N4HY,
jumped in and wrote a manual software routine that generated another spur in
software that you adjusted to the same amplitude as the offending hardware
spur, then you moved the software spur onto the hardware spur and adjusted
the phase of the software spur to greatly reduce the hardware spur. This
procedure works, HOWEVER, this procedure is ONLY good for one band at a time
and if you change bands you have to run the manual procedure again.
A few weeks ago I was on 30 meters calling a DX station...same situation, up
about 2.5 KHz and I got slammed again. I had not run the manual spur
reduction procedure because it is cumbersome, I change bands a lot, so I got
nailed.
Those are the facts. Flex has known about this for about one year now and
nothing has been done to address it other than Bob's software procedure
(which I greatly appreciated him doing!). In fairness to Flex this probably
only effects less than 5% of their customers so there is no real urgency on
their part to address this. If you're going to enter the DX and contest
arena, though, please beware and the reason for my TopBand reflector post.
In time, you will get nailed to the wall with a nail gun because of it!
Sadly, as a result of this, I no longer use my 5000 on HF. The receiver is
great and performs very well, however the xmit problem is something I cannot
accept at W5ZN in my DX and contest operation.
I mean no offense by this email whatsoever to Flex or anyone, these are
simply the facts of my on-the-air experience and any effort to permanently
resolve this will be most welcome. I would like to use my 5000 on HF again.
73 Joel W5ZN
Date: Mon, 19 Oct 2009 20:38:40 +0100
From: Ian Wade G3NRW <g3...@yahoo.co.uk>
Subject: [Flexradio] Flex 5000 transmit spur
To: flexradio@flex-radio.biz
Message-ID: <6xkbu9nabm3kf...@ntlworld.com>
Content-Type: text/plain;charset=us-ascii;format=flowed
I just came across this contribution from Joel, W5ZN, in the top band
contesting list, and was surprised to read the second paragraph ("Also,
be aware ...").
As a prospective Flex 3000 purchaser, should I be concerned?
------- Forwarded message follows -------
Subject: Topband: noise floor
Newsgroups: !topband
To: 'Pete Parisetti' <hb9...@gmail.com>, topb...@contesting.com
From: Joel Harrison <w...@arrl.org>
Reply-To: w...@arrl.org
Date: Sun, 18 Oct 2009 21:35:06 -0500
Message-ID: <80c27fa30e524e5796108d76c2458...@wgint.net>
Pete - one other thing I need to mention if you haven't noticed
already....The noise floor will be different with each of the three sampling
rates (48, 96, 192). This doesn't change the signal to noise ratio will
change the display. The lower the sampling rate the lower the noise floor.
Also, be aware that the Flex 5000 has a transmit spur approximately 2.4 KHz
down from the fundamental freq. If you are calling a station up 2 KHz or so
and are running an amplifier you will most definitely put out a signal,
thanks to the spur, that people can hear. Flex is very aware of this but
they have NOT, repeat NOT fixed this. One of their software gurus did write
a MANUAL software routine in PowerSDR to address this hardware issue and it
does reduce the spur significantly but the procedure is a manual procedure
and is only effective on one band at a time. If you change bands, you have
to run the manual routine again. It is cumbersome.
After being "busted" twice on two different bands because of this I no
longer run my Flex 5000 on HF for transmitting. It has a very good receiver
and the calibrated dBm scale is great to use for signal comparison and love
it for that, but just be aware of the xmit spur.
I can give you more specific details if desire.
73 Joel W5ZN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
73
Ian, G3NRW
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