Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
Thanks, Jack I just recently realized that many people assume that one sets the softrock center freq to the center of the IF passband. This would require MUCH isolation to keep the LO under control. This is NOT how I would recommend it be used. I would set the softrock's oscillator below the IF passband, outside the area passed by the roofing filter. Since all I ever use in my panadaptor with either my 756PRO3 or SDR-1000 or sofrtock 40 is about +/- 12 KHz anyway, I will be quite happy setting the LO to 12 KHz below the IF center, and let the SR panadaptor display the K3 tuned freq +/- 12 KHz. With this design, isolation problems may be simplified. Also, there is no need for a premium soundcard. I hope that, with the LO well outside the IF passband, we will need considerably less isolation. I actually have a premium soundcard available, so I can move the LO even farther away if that helps. But I won't know for sure until mine comes in and I warm up the soldering iron. Jerry W4UK At 06:14 AM 2/12/2008, you wrote: Jerry: You might first wish to measure the reverse isolation of a MMIC before you make that statement. While they are great devices, isolation is not their strong suit. The Gali74, which I use for a variety of purposes, has an isolation of around 28 dB at the K2's IF frequency. The gain is 25 dB, so if you pad the output for unity gain, you are around 53 dB. With a Softrock's typical -40 dBm LO leakage, that strikes me a bit on the marginal side. Jack K8ZOA Jerry Flanders wrote: I assume a simple MMIC amp plus a simple resistive attenuator circuit will provide enough isolation and also provide for matching levels up/down as may be necessary. At least, that will be my first cut at the problem unless somebody else comes up with a better plan before my K3 arrives. At down east microwave ( http://www.downeastmicrowave.com/cat-frame.htm ), see the http://literature.agilent.com/litweb/pdf/5967-6159E.pdfINA10386 (DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5. Very easy to use something like this, I think. Depending on the signal level of the K3 IF output, we might get enough isolation from a resistive attenuator alone and still have a usable signal level on the softrock panadaptor. I would much prefer a plug and play manufactured solution if it takes more than an attenuator, but not an expensive one. Jerry W4UK At 07:29 PM 2/11/2008, stephen pearce wrote: A month or so ago one of the Elecraft engineers pointed out that if the softrock lite rx is connected directly to the if port on the k3 there was a significant issue with coupling of rf from the softrock board into the rx if of the k# with consequent degradation in rx performance ... Has anyone produced a design for a suitable isolation amplifier/ coupling stage which will prevent this and still allow the softrock to be used (in conjunction with a pc) as a panadapter? Thanks -- Stephen Pearce zl1any Whangarei ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
I have not found that to be the case. I tried a number of MMICs and found them lacking in the kind of reverse isolation needed for this job. I use the same device in my LP-PAN panadapter as K8ZOA uses in his Z1 buffer. I am seeing 100dB isolation of the LO signal from my panadapter, which uses a mixer that is roughly similar to the SoftRock. Since my IF is at 8215 kHz, any LO leakage would be seen at the center of the panadapter display. In my case, the leakage signal is below the noise floor. With a SoftRock, the leakage signal would appear 23 kHz away from the K3 IF. I wouldn't use a SoftRock without a buffer, and if I did, I would sure make sure it was disabled during xmit. For reference, I measured LO leakage of a SoftRock on the order of -40dBm, which translates to over S9+30dB. It was also mentioned about filtering the stuff coming out of the K3 IF port. In my testing, I have found that additional bandpass filtering between the K3 IF and buffer are definitely required to avoid spurious mixing products between signals in the K3 BPF passbands and the internal signals coming out the essentially unfiltered K3 IF port (mostly LO and its harmonics). This is especially the case on 40m where a lot of strong signals can appear in the passband. I have found a 4th order bandpass filter to be acceptable for this task. 73, Larry N8LP Message: 48 Date: Mon, 11 Feb 2008 23:46:27 -0500 From: Jerry Flanders [EMAIL PROTECTED] Subject: Re: [Elecraft] K3 if isolation of softrock lite used as panadapter To: stephen pearce [EMAIL PROTECTED], Elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii; format=flowed I assume a simple MMIC amp plus a simple resistive attenuator circuit will provide enough isolation and also provide for matching levels up/down as may be necessary. At least, that will be my first cut at the problem unless somebody else comes up with a better plan before my K3 arrives. At down east microwave ( http://www.downeastmicrowave.com/cat-frame.htm ), see the http://literature.agilent.com/litweb/pdf/5967-6159E.pdfINA10386 (DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5. Very easy to use something like this, I think. Depending on the signal level of the K3 IF output, we might get enough isolation from a resistive attenuator alone and still have a usable signal level on the softrock panadaptor. I would much prefer a plug and play manufactured solution if it takes more than an attenuator, but not an expensive one. Jerry W4UK ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
The Softrock receiver I received came with a common 32768 crystal, giving a LO of 8192, far out of the passband of the roofing filter. I wonder if that won't help a bit. Dave W5DHM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
Jerry: You might first wish to measure the reverse isolation of a MMIC before you make that statement. While they are great devices, isolation is not their strong suit. The Gali74, which I use for a variety of purposes, has an isolation of around 28 dB at the K2's IF frequency. The gain is 25 dB, so if you pad the output for unity gain, you are around 53 dB. With a Softrock's typical -40 dBm LO leakage, that strikes me a bit on the marginal side. Jack K8ZOA Jerry Flanders wrote: I assume a simple MMIC amp plus a simple resistive attenuator circuit will provide enough isolation and also provide for matching levels up/down as may be necessary. At least, that will be my first cut at the problem unless somebody else comes up with a better plan before my K3 arrives. At down east microwave ( http://www.downeastmicrowave.com/cat-frame.htm ), see the http://literature.agilent.com/litweb/pdf/5967-6159E.pdfINA10386 (DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5. Very easy to use something like this, I think. Depending on the signal level of the K3 IF output, we might get enough isolation from a resistive attenuator alone and still have a usable signal level on the softrock panadaptor. I would much prefer a plug and play manufactured solution if it takes more than an attenuator, but not an expensive one. Jerry W4UK At 07:29 PM 2/11/2008, stephen pearce wrote: A month or so ago one of the Elecraft engineers pointed out that if the softrock lite rx is connected directly to the if port on the k3 there was a significant issue with coupling of rf from the softrock board into the rx if of the k# with consequent degradation in rx performance ... Has anyone produced a design for a suitable isolation amplifier/ coupling stage which will prevent this and still allow the softrock to be used (in conjunction with a pc) as a panadapter? Thanks -- Stephen Pearce zl1any Whangarei ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
I assume a simple MMIC amp plus a simple resistive attenuator circuit will provide enough isolation and also provide for matching levels up/down as may be necessary. At least, that will be my first cut at the problem unless somebody else comes up with a better plan before my K3 arrives. At down east microwave ( http://www.downeastmicrowave.com/cat-frame.htm ), see the http://literature.agilent.com/litweb/pdf/5967-6159E.pdfINA10386 (DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5. Very easy to use something like this, I think. Depending on the signal level of the K3 IF output, we might get enough isolation from a resistive attenuator alone and still have a usable signal level on the softrock panadaptor. I would much prefer a plug and play manufactured solution if it takes more than an attenuator, but not an expensive one. Jerry W4UK At 07:29 PM 2/11/2008, stephen pearce wrote: A month or so ago one of the Elecraft engineers pointed out that if the softrock lite rx is connected directly to the if port on the k3 there was a significant issue with coupling of rf from the softrock board into the rx if of the k# with consequent degradation in rx performance ... Has anyone produced a design for a suitable isolation amplifier/ coupling stage which will prevent this and still allow the softrock to be used (in conjunction with a pc) as a panadapter? Thanks -- Stephen Pearce zl1any Whangarei ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 if isolation of softrock lite used as panadapter
Thanks - the post was actually captioned 2nd Run on Z1 Buffer Amplifier. For the K3, the universal model of the Z1 would be usable and will provide around 70 dB isolation, which, when combined with the isolation in the K3's internal source follower IF buffer pick-off amplifier should be enough to let a Softrock receiver work without interference to the K3. I've delayed receipt of my K3 until the 2nd receiver issues are sorted out, so I can't run tests, but based on the numbers involved (Softrock local oscillator output around -40 dBm if my memory is correct) the Z1 and K3 internal isolation in tandem should be adequate. A related issue is whether it is necessary/desirable to interpose a bandpass filter between the K3's IF output and the Softrock receiver input. There's a lot of stuff that comes out the K3's IF output port, signals from internal oscillators, etc. I don't have an opinion on whether a 300 or 400 KHz wide bandpass filter will be necessary or not. Again, that requires some measurements that I can not perform until my K3 arrives. Since the Softrock works with an antenna connected to it, I suspect that additional filtering won't be required, but it would be nice to verify my suspiscion. I also have a connectorized version of the buffer amplifier, but had not decided whether to make it available or not. I use them around my shop when I need extra amplification for a particular project. Jack K8ZOA rkayakr wrote: Stephen Please comment by Jack Smith K8ZOA on Z1 interface in topic K3 SSB Strange Behavior. Bob KD8CGH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] K3 if isolation of softrock lite used as panadapter
A month or so ago one of the Elecraft engineers pointed out that if the softrock lite rx is connected directly to the if port on the k3 there was a significant issue with coupling of rf from the softrock board into the rx if of the k# with consequent degradation in rx performance ... Has anyone produced a design for a suitable isolation amplifier/ coupling stage which will prevent this and still allow the softrock to be used (in conjunction with a pc) as a panadapter? Thanks -- Stephen Pearce zl1any Whangarei ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
