Marriage between 20th & 21 century

[w1vtp]

Well, sort of.  Somewhere on this forum it was discussed the hooking up of a BA receiver such as the SP-600 and a Flex.  I had said that I might try it but I thought some attenuation should be used between the IF output and the Flex input.  Well, I can confirm  that, yes, the output from the SP-600 is high enough to merit adding attenuation - to the tune of 40 dB.

I think the resultant sound was quite good - this eliminates the distortion that comes along with the old technology diode detection and the "magic" of modifying the audio in the SP-600 plus you get to use Sync Detection.  This approach could also be easily duplicated using the so-called "soft-rock" hardware in conjunction PowerSDR.  Again, caution: levels must be carefully adjusted to eliminate distortion products that come from overloading the mixer in the soft-rock hardware and the input of the sound card of the computer you are going to use.

'nuf said.  Here is a recording of W1AEX and WA3WMI. Both had quite strapping signals.  The screen shot was taken after the fact 'cause I thought it would be a nice touch.

Al

[N2DTS]

The screen shot shows it at -100 db, I do not think you needed to attenuate anything at that level.
I put my sdr-iq directly into the homebrew receiver IF and it was fine...


For $150.00, you can get rid of the boatanchor and use a peaberry V2, or pick up a used sdr-iq cheap.

I just picked up an icom 756 pro 2, and the V2 runs circles around it.

Anyone want to buy a pro 2?

[w1vtp]

The screen shot shows it at -100 db, I do not think you needed to attenuate anything at that level.
I put my sdr-iq directly into the homebrew receiver IF and it was fine...


For $150.00, you can get rid of the boatanchor and use a peaberry V2, or pick up a used sdr-iq cheap.

I just picked up an icom 756 pro 2, and the V2 runs circles around it.

Anyone want to buy a pro 2?

Brett

Note the noise floor (-100 dBm)  That's about right for a receiver noise floor.  I had previously calibrated the system with Timmy and Joe (at +20 to +30 dB over S9).  I did the screen shot on a spur of the moment to show how it looked after the QSO was over.  The 40 dB attenuator is necessary, in my opinion, to avoid distortion and adjacent channel IMD problems.

It was just an experiment to show it could be done.  I'm not sure I want to use that hook up on my 40 meter, 32V1, Hammarlund SP-600 combination or not.  I'm finding the SE-3 to be a bit kludgey to use.

Al

[Steve - K4HX]

Nice recording Al.

Just a few things.

1. SDR is 20th century.

2. $150 would be about an order of magnitude more than needs to be spent to do this. See #3.

3. Use a Soft Rock. It's not so-called, that is what it is called since that is the name the designer gave it. 

[w1vtp]

Nice recording Al.

Just a few things.

1. SDR is 20th century.

2. $150 would be about an order of magnitude more than needs to be spent to do this. See #3.

3. Use a Soft Rock. It's not so-called, that is what it is called since that is the name the designer gave it. 

Yeah, you're right on all three counts.  I gotta get rid of this Soft Rock thing.  It was an interesting experiment. Dunno which way I will go.  Maybe I'll just return the 75A2 to service and simplify the Collins setup

Al

[Steve - K4HX]

Keep it. You have the best of both worlds - a vintage RX with a tuning knob and computer aided filtering, detection and recording on the back end. You can always turn off the computer if you wish go old school. 

[w1vtp]

Keep it. You have the best of both worlds - a vintage RX with a tuning knob and computer aided filtering, detection and recording on the back end. You can always turn off the computer if you wish go old school. 

Worked pretty good today for making a recording of Joe,  W1LJN & Paul, K8MPK.  Here's a recording.  Backgrounder: Joe is 77 years old and is certified to fly a 737 - I don't know about Paul.  I didn't know what they were talking about but I found it none the less entertaining.  Joe also has recently finished climbing the New England 4000+foot peaks.  Interesting guy.  His rig is a Collins 32V3.  Paul's rig is a DX-100.  They both are down to earth guys.

Al

[ka4koe]

Looks nice. I'm using an R388 with an IF output. Would a shielded Hi-R pot serve as a good attenuation device.

Philip

[WU2D]

I think you also need some 19th Century technology in that setup.

[N2DTS]

I do not think this is right.

You will be in the noise floor of the sdr.

The IF output of the receiver is going to be the strongest signal the sdr receives, and it should be in the normal range of signals the sdr is supposed to recieve, not match the boat anchor signal level.

Anyway, using an sdr as a detector is ok, but you do not get most of the advantages that sdr's provide.

Since you are looking at IF, you get no real frequency readout from the sdr.

You get all the front end problems (AGC, intermod, noise) of the old receiver.

You can not see other signals around you, you can not see that the person you are talking to is 2 Kc off frequency twards the side that has the strong ssb signal on it (I see that a LOT).

No click tuning to see who is calling CQ (or you) 5 or 10 Kc away.

The filter passband is only going to be as good as the old receiver.






Brett

Note the noise floor (-100 dBm)  That's about right for a receiver noise floor.  I had previously calibrated the system with Timmy and Joe (at +20 to +30 dB over S9).  I did the screen shot on a spur of the moment to show how it looked after the QSO was over.  The 40 dB attenuator is necessary, in my opinion, to avoid distortion and adjacent channel IMD problems.

It was just an experiment to show it could be done.  I'm not sure I want to use that hook up on my 40 meter, 32V1, Hammarlund SP-600 combination or not.  I'm finding the SE-3 to be a bit kludgey to use.

Al


[/quote]

[w1vtp]

Looks nice. I'm using an R388 with an IF output. Would a shielded Hi-R pot serve as a good attenuation device.

Philip

Dunno.  I'd be afraid of distributed capacitance. Why not make an attenuator?  Here's an article

Al

 

[w1vtp]

Brett

In any case, it's working well with the parameters I've imposed. I've done this under several different scenarios.   The approach works well. The recordings are testimony to that

Al

[Steve - K4HX]

The IF without the crystal filter engaged is at least 8-10 kHz on that R388. A little stagger tuning would make it quite a bit wider. My 51J-4 is about 13 kHz wide and the IF cans are the same as those in the R388. This means that you can see at least 6-8 kHz either side of your center frequency with the SDR. You'll easily see if someone is off from your frequency. You'll also easily see which side the interference is coming from.