SB620 on aR390A

[KC2FXE]

 Hello All:
 Well tring to hook up this SB620 scanalyzer scope to my R390a
but the IF out put on the back panel  goes thru the fliters.
  The manual for the sb620 state i need to hook up at a mixer but i tryed all of them with no luck .I'm trying to find a455khz out put for this scope but so far no luck Any BODY ever try this before?

[WA1GFZ]

I have a SB620 and find it quite useless.
Spend $14 on a softrock 6 kit and see a real spectrum.
Sweeping spectrum displays are a pain to watch.

[wa1knx]

frank,
   wuz softrock 6 kit?

[Pete, WA2CWA]

  Assuming the SB-620 works and you know for sure the IF is 455 KHz, did you try these connections:

Plate of V204, 6C4, 3rd mixer, through a 3 or 4 pf cap, or
Grid of V501, pin 1, 1st IF Amplifier, through a 3 or 4 pf cap

The SB-620 input IF must be real close to the IF that your connecting to or you probably won't see any signals. Also, there has to be enough signal level there, to make the SB-620 dance. Note, shielded connecting cable should be used and make it as short as possible.

You might also want to review the SB-620 alignment procedures.

[WA1GFZ]

softrock40@yahoogroups.com

John,
Check these guys out. The newer kit is the softrock 6. Just ask for a crystal to demodulate 455 KHz. Look back through the postings and you will see a number of guys are doing IF demodulation that also displays a nice FFT spectrum display.. Steve HUZ just bought a kit. Sometimes the seller will do assembled kits. You can use FLEX SDR1000 software or I2PHD software. Buth have AM sync detectors.
This cheap little kit and a computer sound card will blow the 620 away.
My 620 has a problem with drifting resistors and need to replace a number of high values that have drifted enough that the trace is off the screen. I also have the older ho10. I took the IF filters out of it and installed them in the 620 to sharpen up the bandwidth and it still is less than impressive. I find it only useful for looking at a wide spectrum. Pete SOV was doing the same thing with his homebrew converter last night. gfz

[Pete, WA2CWA]

Sooooo, working just from memory here, at the points you mention, the received signal has already been through 2 tuned RF stages and some cans. Just how much bandwidth from the tuned frequency of the R-390A could be monitored at these points and be considered to be a true representation of the received signal in from the antenna?

I did the old monitor the IF output on a scope thing here years ago on a couple of receivers, it never really seemed to be a true representation of the incoming signal? The AM that looked great sometimes sounded lousy and vice versa?       

Ideality, in my opinion, the best place to hang a panadapter (like Heath's SB-620, HO-13, HO-5404 w/HOA-5404-1) is at the output of the first mixer. This requires that the panadapter IF frequency and the output of the mixer frequency match. However, some of our older receivers have two or more mixers (single conversion on some bands, dual conversion on other bands etc.) so it's sometimes difficult to make the panadapter work on all receive frequencies unless you take this into consideration. As you move the panadapter connection further down the mixer/IF chain, the less effective  the panadpter features become.

A receiver having 1, 2, or more RF stages really doesn't make a lot of difference other than maybe a noisier looking (more "grass") baseline. I don't remember exactly what the sweep width of the SB-620 is, but it's probably close to the HO-13 specs. which are 15 -100 KHz.

For monitoring IF output, I generally hang the scope on the input to the detector stage. However, I generally never see any real correlation between a scope display and what you hear after the audio is detected and sent through the various audio stages and speaker.

[Pete, WA2CWA]

You should see the panaoramic display on the Flex SDR-1000. See a signal blip; run your mouse pointer to it, click, and you're listening to it. You'll never go back to the old stuff.



You said, "I just didn't get much out of sitting there looking at the scope trace in my previous attempt at this setup. I was not trying to panoramic display, only look at the received AM signals. Things just never seemed to jive between what I saw & heard."

Once it goes through the detector, AGC stages, and audio stages, things change.

[WA1GFZ]

The SDR1000 software will work with the softrock connected to your R390a
Just tune the radio like normal and use the software to monitor the spectrum and demodulate if you like. Variable bandwidth is very cool. The SDR1000 software will also allow you to fine tune a bit.  I use a stock dell sound card that works well.
better sound cards give better performance.
I wouldn't buy an SDR1000 now a new generation is brewing.

[Pete, WA2CWA]

New stuff is always brewing. Sometimes you just have to draw a line in the sand and just go for it. Waiting, "for the better thing", deprives you of near-term gratification and enjoyment. You can deal with far-term products when they arrive. Plus resale value of used SDR-1000’s is very good.