[Kenwood] SM-220/230 Questions

[WD8ARZ]

Hello Roy, here are the answers to your questions, placed below.

73 from Bill - WD8ARZ
wd8arz@ix.netcom.com

----- Original Message ----- 
From: "Roy Sakabu" <rsakabu@pwav.com>
To: <kenwood@mailman.qth.net>
Sent: Friday, April 19, 2002 10:39
Subject: [Kenwood] SM-220/230 Questions
>

> Hello list,
> I have a few questions regarding the "Station Monitor" scopes 
> (SM-220, SM-230) from the TS-940/950 era, mostly about the
> scope portion. How do they work?  Does it take the IF output 
> from the radio and display it?

* Yes, the I.F. is used from the radio, but it must fall within the
* frequency range of the panadapter module, so you have to choose
* the right module for the rig your going to use it on. The modules are 
* adjustable over a limited range. For example I am using the 8mHz
* module in the SM-220 with my Ic-720, but I had to retune the module
* for the slightly different I.F. frequency. There are three adjustments
* with the modules. One sets the gross frequency range to match the
* IF of the rig. Then there is one for each range to set center freq.

> Can you do the same thing with a plain old oscilloscope?

* No, you can not use a plain ol oscilloscope as a panadapter, or 
* spectrum analyzer with out some external conversion circuit to 
* support that. However the SM-220/230 do have oscilloscope
* features of basic oscilloscopes. These two units also have the
* trapezoid connections to feed the transmitter Rf through so you
* can see the characteristics of your transmitted signal. You can
* not do that on normal oscilloscopes for the most part either.

> When using the pan adapter, do you get a spectrum sweep
> where you can "see" who's talking above and below the
> frequency you are tuned to and is this similar to something like
> the IC-756Pro/Pro2 scope?  How wide can you sweep?

* Yes, and in real time. The sweep rate is adjustable, and there
* are two sweep ranges. Plus or minus 20 kHz of the tuned center
* frequency, and plus or minus 200 kHz. The Pro and Pro II are
* not the exact same panadapter. The Pro has some time delay, and
* I have heard poorer resolution than you would like to have. The
* Pro II however is much better and near as you can get to an
* external panadapter as you can get. But you pay a price, and I 
* don't just mean money. In order to have a wide enough band pass
* for the spectrum to be display, the I.F. tap off point cant have narrow
* filters ahead of it. Other wise the display on the scope would be
* no wider than the filter a head of it. Thus the First and Second I.F.
* in the Pro II is not narrowly filtered, and that is why it performs
* worse on Imd tests .... front end over load. The roofing filter in
* Pro II is in the Third I.F. of all places, to provide better filtering
* to Dsp functions down stream. Other rigs not only have the roofing 
* filter ahead of the first I.F., some have it ahead of any amplification
* devices of any kind. That is why those rigs have better receivers.
* A roofing filter will only be 15-25 kHz wide generally. Of course
* true discrete filters in the both of the first two I.F.'s go along way
* to improving receiver performance also. This is why the SM-220 
* here is connected to my IC-720 and not the FT-1000MP
*  (ie roofing filter)

> I just got a TS-940 (what a big, beautiful radio).  Can I use either the
> SM-220 or the SM-230?

* Yes, you can use either SM, but I have heard many complaints of 
* excessive drifting on the SM-230 as expected for its price new. The
* SM-220 will drift to, but settles down after awhile. Again, you have
* select the right panadapter I.F. frequency your going to need, or build
* a mixer to make the conversion between the rig and the panadapter.
* Yes, you have a great hf rig there, and a good SM on it would be
* a terrific performer and bang for the buck as compared to a Pro II. I
* would be tempted for the Pro II or III as a second rig though ... hi hi
 
> Do you know of a web page that might describe the functions/features
> of the scopes?

* No, I haven looked. But I bet if you did a search using Google, you
* might find a lot of information, and sources.

> Thank you very much,
> Roy
> AD6ZU