Bob:
Thank you for your advise and help.
There are two separate issues:
1. DSP overload
2. BCI Overload
BCI overload is from very strong AM station close to my house. I have just
measured with the scope and the max. P-P voltage =2.00V at 50 Ohms.
I didn't have much time (lunch time) to take this measurement. I need to make
sure that there is no error.
When I engage attenuator in my Orion (preamp OFF) the IMD signal drops
proportionally.
That tells me that overload is happening before the attenuator. When I put
external attenuator at the antenna input than IMD is gone.
Also, if I put external High Pass filter IMD is gone.
That is why I'm looking at diode protection circuit right before the
attenuator. Unless there is some other circuit before that and I didn't
find it yet.
There is no BCI IMD in K2 or TS930s or FT1000D.
Very strange.
Thanks,
Mark WQ7X
>
> From: "Bob Henderson" <bob@cytanet.com.cy>
> Date: 2005/05/24 Tue PM 04:26:29 EDT
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Subject: Re: [TenTec] My new Orion
>
> Mark
>
> I apologise if I am repeating what has already been said but I saw your mail
> and having just returned from Dayton, I have a bunch of stuff still to catch
> up on. Anyway fwiw.
>
> Unless your Orion is faulty, the overload problem you see is not caused by
> hardware. I can say that quite categorically, because the effect was not
> apparent before 1.372. Personally, I wouldn't waste time looking at D30/D31
> or the front end devices.
>
> Orion has two agc loops. One of these controls the gain of the analogue
> front-end circuitry and the other the dsp back-end. These are necessary
> because the dsp i/f itself does not have adequate dynamic range to cope with
> the range of signal levels we experience.
>
> Firmware 1.372 combines adjustment of analogue rf gain together with dsp
> gain using the single rf gain control. This has been done in an attempt to
> make adjustment of the Orion rx less fiddly and intimidating. The problem
> is that the algorithm used to make the adjustment is imperfect. The
> consequence is this is that the dsp gain can be set too high and therefore
> overload in that part of the circuitry can occur. I believe the new V2
> firmware will resolve this.
>
> Whilst intuitively it seems a nonesense to believe the overload is a product
> of the firmware, this is nonetheless the case. As has been suggested
> already, the hardware is pretty much rock solid as evidenced by the various
> reviews which have been carried out by third parties. A temporary
> regression to firmware 1.371 should confirm this for you.
>
> Of course, if your findings are at odds with the above, then conceivably you
> have a hardware problem with your Orion and I am sure Ten Tec will be able
> to help. More likely, you will find what I have described.
>
> 73 Bob, 5B4AGN
>
>
> ----- Original Message -----
> From: <wq7x@cox.net>
> To: <tentec@contesting.com>
> Sent: Tuesday, May 24, 2005 5:19 PM
> Subject: [TenTec] My new Orion
>
>
> > Bill:
> >
> > Thanks for very comprehensive response. I agree with you 100%.
> > 1. Orion is the best for BDR and IMD but not with 1.372.This just kills
> the RX.
> > 2. Orion is not as good as K2 or IC7800 with 1kHz spacing and S9+35dB
> signal only because of 1.372 firmware.
> > 3. I know that people in EU reporting great results for BCI overload. That
> is why I'm puzzled why I have this problem.
> > I will borrow from my QRL the spectrum analyzer and check what is
> going on. However some others in private
> > emails did report similar problems. Look at the schematic-there are
> two protection diodes at the input of the
> > RX -D30 and D31. I think that AM station drives them in nonlinear
> region. I will check that. Orion attn. doesn't
> > improve overload, so it has to take place before the attenuator.
> External high pass filter eliminates the problem.But than I can't receive
> anything below 1.3MHz.
> >
> > This is the second time that I have purchased the ORION. First time almost
> two years ago.
> > This time I will not send it back to Ten Tec. Many problems are fixed
> (including hardware NB -was really ON in OFF position)
> > It is so close to be superb TRX. That doesn't mean that we should be quiet
> about some remaining problems.
> > Orion has very quiet RX. Pleasure to lsn. at night. Also, WOW no fan
> noise. Where is the fan? Hi Hi. Great.
> > Audio quality in SSB on RX and TX - out of this world. I liked better than
> IC7800.
> > To me narrow roofing filters and very low phase noise is necessary in
> well design RX. I use to design and build many RX myself.
> > I'm really happy that there is a company which understands the basics of
> good RX design. In Japan they are still learning.
> > We all should agree that IC7800 is very well designed TRX and mechanically
> is the best. Very solid and high quality.
> > They just forgot about basics of the RX design. Still don't understand how
> could Icom not pay attention to the phase noise.
> > Their DSP in CW however is just incredible. But this is just not good
> enough for me.So, Orion is my main Trx now.
> > Best 73! Mark WQ7X
> >
> >
> > _______________________________________________
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> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
>
>
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