The 2.44 kHz spur does exist, and it is particularly noticeable on 160 meters
where local signals can be extremely strong. I measured it on a 5000A some
months ago, but did not test the 3000 on transmit. If my memory is correct,
the spur was down around 57 dB on 160 meters, but since I did not record the
data, I could be mistaken.
It definitely varied from band to band, but I did not check to see if it varied
with frequency within a given band. I did not experiment with the manual
nulling process, as I would never be able to do that in a contest, such as in
the upcoming CQ WW SSB this weekend. It is more of a CW issue, but I assume it
exists on SSB, but is likely covered up by IMD products in the PA.
If one looks at the odd-order IMD products on the 5000A, there are some unusual
products in-between the 5th, 7th, 9th and 11th products. I don't know if the
extra products have anything to do with the spur or not. My guess is no. IMD
measurements on five brands of transceivers were made on 20 meters . If anyone
wants to look at this data, it can be downloaded at: www.nc0b.com/temp.
Download the following files: nc0b-w9dxcc-3a.ppt (Power Point) and the two
associated WAV files. This presentation was given at W9DXCC on September 19,
2009.
There is a lot of information on many aspects of receiver and transmitter
performance in the Power Point slides.
73, Rob, NC0B
>>> "Jordan" <outposte...@shaw.ca> 10/20/2009 12:50 PM >>>
I haven't noticed this either, but I may check for it a little more closely
now....I'd like more info if there is any available as
well...73...Jordan....
----- Original Message -----
From: "David Beumer W0DHB" <d...@w0dhb.net>
To: "Ian Wade G3NRW" <g3...@yahoo.co.uk>
Cc: <flexradio@flex-radio.biz>
Sent: Tuesday, October 20, 2009 12:25 PM
Subject: Re: [Flexradio] Flex 5000 transmit spur -- any validity to this
> Tim, Dudley
>
> I have not observed this -- what's the scoop ?
>
> Dave
> W0DHB
>
>
>
> Ian Wade G3NRW wrote:
>> 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
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>
>
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