SM220 connection to TS440S

Discussion in 'Amateur Radio Amplifiers' started by W6TMV, Jan 29, 2011.

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  1. W6TMV

    W6TMV Ham Member QRZ Page

    Hope this is the correct forum...
    I have a Kenwood SM220 with the BS8 Panadapter (455KHz if) and would like to connect it to my Kenwood TS440S which has the first or second if matching this...
    Any writeups on doing this or has anyone done this? I had a suggestion some time ago, but lost it...(my bad). Any suggestion/help appreciated.
     
    Last edited: Jan 29, 2011
  2. WA7PRC

    WA7PRC Ham Member QRZ Page

    It's the 2nd IF (8.83MHz) that you're interested in. But, before you dive in, consider the following. Most modern rigs use a triple-conversion receiver, with a high 1st IF. Your TS-440S is one of these, with a 45.05 MHz 1st IF and a "roofing filter" that has a bandwidth of around 20 KHz. Typically, this filter limits the bandwidth you'll "see" with a panoramic display adapter ("panadapter" or "bandscope"). In the TS-440S, the roofing filter will limit the bandwidth you'll see:

    [​IMG]

    I advise against bypassing the roofing filter. Doing so will severely diminish your receiver's in-band QRM rejection (it'll likely overload on any strong signal in the band). So, your "window" is likely limited to ±10KHz or so (your SM-220's wide sweep setting will be useless).

    If you want to add a tap, you'd tap ahead of any filters in the 2nd IF (8.83 MHz). A convenient place to tap this signal is at the input to the IF Unit (pn X60-1300-00)... J15-1 (RIF) and J15-2 (GND). BUT... there's another bandpass filter (F2) in the output of the 2nd Mixer on the RF Unit (pn X44-1680-00). Apparently, Terry/WA8OPR saw this and tapped ahead of F2 on the RF Unit with his TS-440S IF Output Modification for use with Larry N8LP's LP-Pan unit.

    My TS-850S has a high 1st IF (73.05 MHz) but they tap into that signal before the filter, mix it down to 8.83 MHz, and feed it to the noise blanker. They also provide an output to the rear panel for a panadapter. I use a Heath SB-620 'Scanalyzer' and can sweep the entire band. No, you can't have my 850 or 620! :p
     
  3. W6TMV

    W6TMV Ham Member QRZ Page

    Thank you for educating me on this - I should have known it was 8.83 as that is what matches the SM220 BS8 adapter - guess I will just leave it alone for now as it sounds like a useless mod - I've had the unit a long time and only used it to monitor the amp output or signal thus far...agn, mny thanks.
    Added - will look up those mods though!
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    You're welcome. I'd hate to see someone go through the trouble to add the tap and then be disappointed with the bandwidth. I've used it with my olde TS-120S & TS-130S (with a buffer amplifier) but then, those rigs are single conversion and it's broad as a barn door ahead of the IF filter.

    IMO, Kenwood tried to do too much in one box anyway. Though it's tubes, I like my Heath SB-620 better (as a panadapter) than my SM-220 with BS-8...

    • I prefer the longer persistence of the 620's CRT better (short duration signals such as CW & SSB display long enough to see).
    • The graticule for the 620 is marked better for use as a spectrum analyzer. The Kenwood unit just has X-Y markings (kinda hard to interpolate frequency and relative amplitude).
    • The Heath unit's vertical amplifier has linear, log, and log -20dB settings. With the Kenwood unit, you just have an input attenuator (I assume linear response only).
    • One thing I found to be a particular nuisance with the Kenwood unit was that they don't sense T/R function of your rig. Therefore, you have to turn a couple of knobs to setup for xmit and turn them back for proper rcv function
    • The 620 works with many IF frequencies. Its input amplifier can be used as a mixer, allowing it to be used with just about any IF (you need a heterodyne oscillator & enough IF level to drive it).
    I currently use the SB-620 for rcv monitoring and the SM-220 for xmit monitoring. I have an SB-610 xmtr monitor that I'll bring online when I get:

    [​IMG]
     
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